JPH03233329A - Photometric device - Google Patents

Abstract

PURPOSE:To allow the rapid acquisition of metering information even when a subject is illuminated with a light source of periodically changing luminances by correcting the information to the luminance information corresponding to the average value of the luminance information obtd. by plural times of accumulation with an image sensor. CONSTITUTION:A microprocessor M calculates the luminance information at every specified period form the signal of a photoelectric conversion element AE for photometry which executes center-weighted metering, etc., and determines the average luminance information of the subjected illuminated with the light source of the periodically changing luminances by averaging plural pieces of the calculated luminance information. On the other hand, the processor calculates the luminance information from the signal by one time of the accumulation of the accumulation type image sensor AF for focus detection and corrects this information by using the luminance information based on the photoelectric conversion element for photometry and the average luminance information. The immediate estimation of the average information calculated from the luminance information determined by making plural times of the accumulation with the image sensor AF is thus possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a photometric device used in a camera that obtains luminance information of a subject, and particularly to a photometric device that obtains luminance information from the output of an image sensor used for focus detection. The present invention relates to a photometric device.

[Prior Art] Photometering devices in cameras include average metering that measures the entire photographic screen, center-weighted metering that focuses on the area near the center of the screen, and spot metering that measures a very narrow area at the center of the screen. There is photometry, etc.

On the other hand, in recent cameras, the light beam in the center of the shooting screen is converted into an electrical signal by an image sensor array made up of multiple photosensor pixels, and focus detection is performed based on this electrical signal to achieve autofocus. However, it is known to perform spot photometry by simultaneously using the electrical signals of this image sensor array as luminance information.

[Problems to be Solved by the Invention] However, since the image sensor array used for focus detection is of a charge accumulation type, such as a COD image sensor, the following problems arise.

Generally, in a photometer, the electric charge generated by a photodiode is used as a current value, so that luminance information at a certain point in time can be obtained instantaneously. Therefore, in order to suppress fluctuations in brightness information when the brightness changes periodically, such as when the light source illuminating the subject is a fluorescent lamp, it would be a waste of time to use a configuration that averages the brightness information from several times. I never eat.

However, in the case of a charge accumulation type sensor such as a COD image sensor used for focus detection, in order to obtain a sensor output signal, it takes a long time to accumulate charge, that is, an accumulation time.
Transfer time is required to output the outputs of multiple photosensors in time series using a shift register, and in order to suppress fluctuations in brightness information due to periodic light such as fluorescent lights, it is necessary to average the brightness information of several times. When I tried to do this, the problem was that it took a very long time.

The present invention has been made in view of these conventional problems, and it is possible to immediately obtain luminance information corresponding to the average value of multiple luminance information from a signal obtained by one accumulation by an accumulation type image sensor. The object of the present invention is to provide a photometric device that can perform

[Means for Solving the Problems] First, the present invention is directed to a camera having a photoelectric conversion element for photometry and an accumulation type image sensor for focus detection.

In the present invention, as a photometry device for such a camera,
a first photometric calculation means for calculating brightness information by inputting the light reception signal of the photoelectric conversion element for photometry at regular intervals; a second photometric calculation means for calculating average brightness information from which fluctuations due to periodic light sources have been removed based on the average value; calculating brightness information by inputting a signal obtained each time the image sensor completes one accumulation; a third photometric calculation means; based on the brightness information calculated by the first and second photometry calculation means, the image sensor accumulates the brightness information calculated by the third photometry calculation means a plurality of times; and a correction means for correcting the brightness information to correspond to the average value of the brightness information obtained.

Here, in the correction calculation by the correction means, if one accumulation time of the image sensor is shorter than the brightness information calculation cycle of the first photometry calculation means, the correction calculation is performed by adding the brightness information calculated by the third photometry calculation means to the brightness information calculated by the third photometry calculation means. Correction is performed by adding the difference between the average photometric information calculated by the second photometric calculating means and the luminance information calculated by the first photometric calculating means at approximately the same time as the completion of one accumulation of the image sensor.

Further, if the one-time accumulation time of the image sensor is longer than the brightness information calculation cycle of the first photometric calculation means, the brightness information calculated by the third photometry calculation means is added to the brightness information calculated by the second photometry calculation means. Correction is performed by adding the difference between the average brightness information obtained and the average value of the plurality of brightness information calculated by the first photometric calculation means during one accumulation of the image sensor.

[Function] According to the photometric device of the present invention having such a configuration, luminance information is calculated at regular intervals from a signal of a conventional photoelectric conversion element for photometry that performs center-weighted photometry, etc., and the calculated luminance is By averaging a plurality of pieces of information, average brightness information of a subject illuminated by a light source whose brightness changes periodically is determined.

On the other hand, brightness information is calculated from the signal accumulated once by the storage type image sensor for focus detection, and the brightness information based on this image sensor is corrected using the brightness information based on the photoelectric conversion element for photometry and the average brightness information. By doing so, it is possible to immediately estimate the average brightness calculated from the calculated brightness information that has been accumulated multiple times by the image sensor.

[Example 1] FIG. 1 is an overall configuration diagram of a camera equipped with a photometric device of the present invention.

In the pair 1 diagram, L is the objective lens and HM is the half mirror.
15M is a submirror, FS is a focusing screen, PP is a pentaprism, IP is an eyepiece, AE is a photometry module equipped with a photoelectric conversion element, and AF is a focus detection module equipped with an accumulation type image sensor (COD image sensor). , MP is a microprocessor.

Of the light flux that passes through the objective lens L, a part of the light flux reflected by the half mirror HM forms an image on the focusing screen FS, and the photographer uses the pentaprism P to pass this formed image.
P allows the image to be observed as an erect image through the eyepiece IP. Then, the photometry module AE sends the light reception signal of the image on the focusing screen FS to the microprocessor.
It outputs to the MP to calculate brightness information.

On the other hand, among the light fluxes that have passed through the half mirror HM, the light flux near the optical axis of the objective lens L is guided by the submirror SM to the focus detection module AF. Focus detection module AF
includes an image sensor array to be described later, converts the light beam incident on the focus detection module AF into an electrical signal, and inputs the electric signal to the microprocessor-MP. The microprocessor MP detects the focus adjustment state (defocus amount) of the objective lens L and calculates brightness information in a very narrow area at the center of the photographic screen based on signals from the image sensor array.

Next, the configuration of the image sensor chip 3 used in the focus detection module AF will be explained using FIG.

As shown in FIG. 2, the image sensor chip 3 includes a pair of image sensor arrays a and b consisting of a plurality of sensor pixels arranged laterally, and another pair of image sensor arrays c and d perpendicular to these. has. Therefore, even for objects that have contrast only in the horizontal direction, such as the horizon, focus can be detected by the image sensors c and d.

Image sensor - first parallel to array a, b, c, d
．． Second. Third shift register 111°112.11
3 is formed, and outputs the image sensor array signals from output terminals 0UTO, 0UTI, and 0UT2. Image sensor array c, d and shift register 1
Memory parts 116 and 119 are provided between the image sensor array C1d and the image sensor array C1d, and these memory parts temporarily store charge signals corresponding to each photosensor from the image sensor array C1d, and store them in the shift register of the next stage after a predetermined time. 112.11
Transfer to 3. The shift gate 14 transfers the charge signal stored in each photosensor of the image sensor arrays a and b to the shift register 111, and the shift gate 1
15.118 transfers the charge signals stored in each image sensor array of image sensor arrays c and d to a memory part 116.119. Memory part 116.1
A transfer gate 117110 provided between the shift register 19 and the shift register +12113 is provided to transfer the charge signal stored in each memory element of a part of the memory to the shift register 112 and 113. The input terminal CLR is connected to all image sensor arrays a,
b, c.

d, and charges corresponding to the light incident on the photosensors are accumulated in each photosensor only during the period when the digital signal "L" is input. In addition, the input terminal CLKI
is connected to all shift registers, and transfers the output charges from each image sensor array a, b, c, d to shift register I11.112.113 according to the transfer pulse.
Used to transfer data sequentially.

Next, the focus detection optical system used in the focus detection module AF will be explained using FIG.

As shown in FIG. 3, the focus detection optical system includes a field mask 20, a field lens 30, and an aperture 4 on the optical axis of the objective lens L.
0, a re-imaging lens 50, and an image sensor chip 3 are arranged in this order. The field mask 20 has a cross-shaped opening and is arranged near the intended focal plane of the objective lens L to restrict the aerial image of the subject imaged by the objective lens L. The diaphragm 40 has four apertures 41, 42, 43, and 44, which apertures 11, 42, 43, and 44 are formed on the objective lens by the field lens 30. ↑2゜13.14
projected as. The re-imaging lens 50 has an opening 51.42.43.44 corresponding to the aperture 41.42.43.44 of the diaphragm 40, as shown in FIG. 3(b). Consisting of four lenses of 52° and 53.54°, the image of the field mask 20 is transmitted to the image sensor chip 3.
image is formed.

Therefore, the light flux incident from the region 11 of the objective lens L passes through the field mask 20, the field lens 30, the aperture 41 of the diaphragm 40, and the lens 51 of the re-imaging lens, and forms an image on the image sensor array d. Similarly, 1 of objective lens L
The light beams incident from areas 2.13.14 form images on image sensor arrays b, c, and d, respectively.

When the objective lens L is focused on the front, the subject images formed on the image sensor arrays a and b move away from each other.
When the rear focus is on, they are close to each other, and when the focus is on, they are lined up at a predetermined interval. Therefore, the horizontal focus adjustment state of the objective lens L can be detected by processing the signals of the image sensor arrays a and b.

Similarly, the subject images formed on the image sensor arrays c and d move away from each other when the objective lens L is focused on the front, approach each other when the objective lens L is focused on the rear, and are lined up at a predetermined interval when in focus. Therefore, the vertical focus adjustment state of the objective lens L can be detected by processing the signals of the image sensor arrays c and d.

The photometry module AE will be explained using FIG. 4.

The photometry module AE has a lens E as shown in Fig. 4(a).
It consists of L and circuit C. The role of the lens EL is to determine from which range of the image on the finder screen FS brightness information is to be obtained.

The circuit C consists of a photodiode FD, a diode D1, and an operational amplifier OP, as shown in FIG. 4(b), for example. This configuration performs the function of logarithmic compression, and the current I generated by the photodiode FD is output by the diode D and the operational amplifier OP to the output terminal 0UTH as a voltage V proportional to Log (1). The reason for logarithmically compressing the current is that the brightness of the subject to be photographed has a very wide dynamic range, and in the APEX method, which is a common exposure calculation method, the subject brightness is logarithmically processed as the subject brightness. This is because since it is expressed as a value Bv, the calculation can be simplified if the data is input in a logarithmically compressed form.

Regarding the connection between the focus detection module AF, the photometry module AE, and the microprocessor-MP explained above, the fifth
This will be explained using figures.

In FIG. 5, 3 is the image sensor chip explained in FIG. 2, 2 is the focus detection optical system 2 explained in FIG. 3, and 4 and 5 are signals between the image sensor chip 3 and the microprocessor-MP. These are a first control section and a second control section that perform control.

The image sensor chip 3 has TRTRI as an input terminal.
, TR2, CLR, CLKI, 0U as output terminal
It has TO,0UTIOUT2. Output terminal 0UTO, 0
UTI, 0UT2 is connected to the second control unit 5, and CLR
The CLKI terminal is connected to the microprocessor-MP, and the input terminals TR, TR2, and TRI are connected to the first control section 4. The signals output from the first control section 4 to TR, TRI, and TR2 are also output to the second control section 5. The output terminal TRR of the microprocessor-MP is connected to the second control section 4, the input terminal INI is connected to the second control section 5, and the input terminal IN2 receives the above-mentioned voltage V manually as a luminance signal from the first photometry module AE. do.

The first control unit 4 controls the terminals TR, TRlTR2 according to the signal input from the TRR terminal of the microprocessor-MP.
A digital signal trigger pulse is generated.

The trigger pulse input to the terminal TR is the shift gate 1
14, 115, and 118 simultaneously to transfer the charge signals stored in the image sensor arrays a, b, c, and e. The trigger pulses input to the terminals TRI and TR2 act on the transfer gates 117 and 110 at different times, respectively, to transfer the charges stored in the memory parts 116 and 119, respectively.

Next, the operation of the image sensor chip 3 will be explained using the timing chart shown in FIG.

Image sensor arrays a, b, c, d are input terminals CL
Accumulation starts simultaneously at time t1 when the digital signal to R becomes "L". When a pulse is applied from the first control section 4 to the shift gate 114 via the terminal TR at time 12,
The charge signals of the image sensor arrays a and b are sent to the shift register Ill, transferred in accordance with the transfer pulse, and outputted from the output section 0UTO as a time-series signal output as shown at PH in the figure. At this same time 12, the charge signals of the image sensor arrays c and d are also transferred to the memory part 116.1 through the shift gate 115118, respectively.
19 respectively. Incidentally, the aforementioned accumulation time is 12-tl.

At time i3 when the charge transfer between the image sensor arrays a and b by the shift register III ends, the first control unit 4
A pulse is applied to the terminal TRI to transfer the charge signal of the image sensor array C stored in the memory section 116 to the shift register +12, and sequentially output it as a time-series signal output like PVI from the output section 0UTI.

Further, the first control unit 4 waits for the completion of the transfer regarding the image sensor array C, and applies a pulse to the terminal TR2 at time t4, and transfers the charge signal of the image sensor array d stored in the memory part 119 to the shift register. 113, and is sequentially output from the output unit 011T2 as a time-series signal output like PV2.

By using image sensor array chips with such a configuration, each image sensor array a, b
, c, and d in parallel are output as time-series signals from the output terminals 0UTO, 0UTI, and PUT2 without overlapping in time.

Next, the configuration of the second control section 5 will be explained using FIG. 7.

The second control unit 5 is 0U of the image sensor array chip 3.
It functions to collectively output a total of three output lines, TO, 0UT1.0UT2, to the input terminal INI of the microprocessor-MP. The output terminals 0UTO, 0UTI, 0UT2 of the image sensor array chip 3 are connected to the switches Sl, S2. S3, the switch SI S2 S3 is connected to the control terminals Jl, +2. +
It is opened and closed by the signal input to 3. each switch Sl, 82. The output ends of S3 are combined into one and input to amplifier G. The circuit shown in FIG.
, TRI, and the control terminals 11. of the switches 51.32.33 by the signals output to the TR2 terminals. +2. This is a control circuit that controls the signal to +3. This control circuit is NO
R gate Nl, N2. N3. It consists of N4 and AND gate AI A2.

Next, the operation will be explained.

When a pulse is input from the first control unit 4 to the TR terminal to end the accumulation of image sensor arrays a, b, c, and d, this pulse is also input to the control circuit, and only the control terminal 11 is controlled by this pulse. becomes the digital signal “H”, only switch S1 becomes “open”, and 0
image sensor array a output from the UTO terminal;
Only the signal b is sent to the microprocessor through amplifier G.
It is sent to the terminal IN+ of MP. When the transfer of the signals from the image sensor arrays a and b is completed and a pulse is output from the first control unit 4 to the TRI, this pulse is also input to the control circuit, and only the control terminal J2 becomes a digital signal due to this pulse. "H", only the switch S2 is "open", and only the signal of the image sensor array C output from the terminal 0υT1 is sent to the terminal INI of the microprocessor-MP through the variable gain amplifier G.

When the signal transfer of the image sensor array C is completed and a pulse is output from the first control unit 4 to TR2, this pulse is also input to the control circuit, and this pulse causes only the control terminal j3 to change to "H" of the digital signal. ”, switch S3
Only the signal from the image sensor array d output from the terminal 0UT2 is sent to the terminal INI of the microprocessor MP through the amplifier G.

Microprocessor-MP is image sensor chip 3
A signal to start the accumulation is input to the CtR terminal and a clock CLKI is input to the transfer gate I11, 112, 113, and the first control unit 4 is instructed to finish the accumulation of the image sensor chip 3. A signal is input to the TRR terminal, image sensor array data sent from the second control unit 5 is input to the INI terminal, and this is A/D converted by the A/D converter built in the microprocessor-MP. The A/D converted data is stored in the memory inside the microprocessor-MP. Here, the A/D converter may not be built into the microprocessor 6 but may be externally attached, but this is not preferable in a camera where space is limited. Then, focus detection calculation is performed using the data string stored in the memory, and the focus detection calculation method is disclosed in Japanese Patent Laid-Open No. 60-3 by the present applicant.
7513, Japanese Unexamined Patent Publication No. 61-245123, etc., so the explanation here will be omitted.

The microprocessor-MP receives the voltage V from the input terminal IN2 as a light reception signal of the image formed on the finder screen FS from the output terminal 0UTE of the photometry module AE, A/D converts it, and stores it in the memory. Then, a value Bv representing the subject brightness is calculated using the APEX method from the A/D converted voltage (2). Here, countermeasures for light sources whose brightness changes periodically, such as fluorescent lamps, in the photometry module AE will be explained using FIG. 8.

As a light source whose brightness changes periodically, consider a light source with a waveform that takes the absolute value of a sine wave as shown in FIG. 8(a). Then, the voltage V output from the photometry module AE changes over time as shown in FIG. 8(b), which is obtained by logarithmically compressing the waveform of the light source.

The microprocessor-MP inputs the output voltage from the photometry module AF at regular intervals tp, adds up the input signals of several times as shown in Fig. 8(c), takes the average, and calculates the Bv value from the average value. This is then taken as luminance information by the second photometric means. The number of additions may be about 8 to 12 times, and since the frequency of the light source is different from the frequency of the AC power supply, the detection period tp is determined by this.

Next, a method of obtaining luminance information using data from the image sensor chip 3 of the focus detection module AF will be explained.

The output of a storage type image sensor such as a CCD is determined by the brightness of the subject and the storage time. For example, as shown in Figure 9, if the storage time is doubled when the brightness of the subject is the same, the output will be doubled. If the storage time is the same and the subject brightness is doubled, the output will also be doubled. Therefore, it is not possible to directly use the output of the image sensor as brightness information of the object; instead, it is normalized by the accumulation time, for example, as shown in the equation below.

OUT/IT Here, OUT is the output of the image sensor, and IT is the accumulation time. The standardized values are then subjected to logarithmic processing, etc., and AP
The subject brightness Bv value of the EX method is calculated.

Incidentally, the outputs of the respective pixels of the image sensor array in the - column are different as shown in FIG. 11, for example. Therefore, as the image sensor output OUT, the average of the outputs of all pixels or some pixels, the one showing the largest output, the one showing the smallest output, etc. may be used. When the image sensor chip 6 used in the present invention has image sensor arrays in both the vertical and horizontal directions, the image sensor output OUT is set using the output of the central pixel in both directions. As a result, the spot photometry area becomes a cross shape as shown in FIG. 10(a), and the spot photometry area becomes elongated using one image sensor array as shown in FIG. 10(b). The advantage is that the difference in photometric values when shooting in a vertical position and when shooting in a horizontal position is small.

Next, Figures 12 and 13 show countermeasures for light sources whose brightness changes periodically, such as fluorescent lamps, in spot photometry using the output of the image sensor of the focus detection module AF.
This will be explained using figures.

In FIG. 12, (1) is a microprocessor-MP
(2) represents the timing of inputting a signal from the photometry module AE at regular intervals tp, and (2) represents the timing of the input signal to the CLR terminal which is stored in the image sensor array of the focus detection module AF.

FIG. 12(a) shows a case where the brightness of the object is high, the storage time IT of the image sensor array is short, and IT<tp. First, the accumulation in the image sensor array starts at the same time as the signal is input from the photometry module at time TA.Actually, the accumulation starts immediately after the signal is input from the first photometry module. It takes almost no time to input the signal from the module, so it can be said that it is simultaneous), 17
Accumulation ends after a certain amount of time. The value (OUT
/IT), and further calculate the brightness value Ez by calculating the Bv value.
seek. On the other hand, the Bv value calculated from the data input from the photometry module AE at time TA is Ha shown in FIG.
It is assumed that the Bv value calculated from the average of the data of the times is Hm shown by the dotted line in the figure.

Photometry range of photometry module AE and focus detection module A
Although the photometry range of F is different, the illuminating light source is considered to be the same, and the Bv value Ha calculated from the data from the photometry module AE and the Bv value Ez calculated from the data from the focus detection module AF are approximately the same. Since this is considered to be the subject brightness at the same time, if the image sensor array is accumulated multiple times, the difference between the Bv value Em and Ez (Em-
Ez) is expected to be approximately equal to the difference between Hm and Ha (Hm-Ha), where <Bv value, based on the data of the photometry module AE.

Therefore, Em calculated by the following formula is a photometric value that is not affected by the periodic light source caused by the focus detection module AF.

Em=EZ+Hm-Ha... (1) In this way, in the present invention, since the image sensor array is stored only once, photometry can be performed much more quickly than when storage is performed multiple times. It becomes possible.

Subsequently, the brightness of the object becomes lower and the storage time IT of the image sensor array becomes longer, as shown in FIG. 12(b) when tp<IT<3Xtp.

First, the accumulation in the image sensor array is started at time TH at the same time as the signal is input from the photometry module AE, and the accumulation is finished 17 hours later.

A normalized value (OUT/IT) is calculated from the output of the image sensor array obtained by this accumulation, and Ez is further calculated as the Bv value.

On the other hand, the Bv values calculated from the data input from the photometry module AE at times TB, TC, and TD during IT are Hb, Hc, and Hd shown in FIG. 13, respectively, and H
Hm (dotted line) is calculated as the Bv value calculated from the average of the past eight data including data for calculating b, He, and Hd.

Since Ez as a Bv value calculated from the data from the image sensor array can be said to be the average of the subject brightness during the time between time TB and TE, if the image sensor
The difference between the Bv value Em and Ez (Em
-Ez) is expected to be approximately equal to the difference between Hm and the average value of Hb, Hc, and Hd (Hm-(Hb+Hc+Hd)+3). Therefore, Em calculated by the following equation is taken as the Bv value by the focus detection module AF which is not affected by the periodic light source.

Em=Ez+Hm −(Hb+Hc+Hd)+3...
(3) Furthermore, even if the brightness of the object becomes low and the storage time becomes longer, the Bv value Em can be calculated in the same manner as described above, but the image sensor array only calculates the Bv value Em during the storage time. Since the average brightness is output, if the accumulation time is longer than a certain point, the B calculated at this time
This means that the v value Ez can be used as it is as a photometric value by the focus detection module AF.

In the embodiment described above, the first photometry module AE is located near the eyepiece lens in order to output brightness information of the image on the focusing screen S, but the invention is not limited thereto. Examples of other forms of the first photometric module are listed below.

FIG. 14 shows an example of a method for supporting the optical system of the focus detection module shown in FIG. 3.

In FIG. 15, HP is a holder made of plastic or the like, 3 is an image sensor array, 50 is a re-imaging lens, 40 is an aperture, 30 is a field lens, 20 is a field mask, Ml is Mira IF is an infrared It is a light cut filter.

The infrared light cut filter IF prevents infrared light components that adversely affect focus detection from entering the image sensor array 3, and the mirror M1 plays the role of bending the light beam so that the entire optical system can be compactly accommodated within the camera. Fulfill.

An example in which a first photometry module AE is added near the focus detection module AF assembled in this way is shown in the 15th example.
It is shown in FIGS.

First, the embodiment shown in FIG. 15 is the lens E of the first photometry module.
L and a photodiode FD are placed at the bottom of the holder HP of the focus detection module, and receive the reflected light beam from the aperture 40 and the re-imaging lens 50.

In addition, in the embodiment shown in FIG. 16, the infrared light cut filter IF
The lens EL and the photodiode FD receive the reflected light beam from the infrared cut filter IF.

In the embodiment of FIG. 17, a half mirror 8M2 is arranged in place of the mirror M1 of FIG. 14, and the light transmitted through the half mirror 8M2 is received by a lens EL and a photodiode FD.

Since the amount of reflected light and transmitted light in the embodiments shown in FIGS. 15 to 17 is small, the reliability of the output of the first photometry module is low when the brightness of the subject is low. However, if the brightness of the subject is low, the storage time of the image sensor array will be longer, so if the light source is a fluorescent lamp or
Even if the image sensor
There is no problem because the subject brightness can be detected without adding correction to the array output. Furthermore, when the brightness of the subject is high and the amount of reflected light is large, the reliability of the output of the first photometry module is sufficient, and as in the case described above, the output of the first photometry module is different from the output of the image sensor array. By adding correction based on this, photometry becomes possible even when the brightness of the light source changes in an AC manner.

In this way, if the first photometry module is placed near the focus detection module without being used to obtain luminance information of the image on the focusing screen, a finder without photometry means can be installed in a finder-interchangeable camera. Even if the image sensor of the focus detection module
An advantage is obtained that brightness information of the object can be obtained by the array and the first photometric means.

In the above explanation, an example has been given in which the present invention is applied to a case where a charge storage type image sensor is used for focus detection and at the same time obtains luminance information of a subject. It is effective in most cases when it is intended to be used without the influence of AC-varying light sources.

For example, in a camera, the shooting screen is divided into multiple areas and the brightness of each area is detected, and from the brightness distribution of the shooting screen obtained, exposure information regarding the optimal exposure amount for the photographic film is obtained. Application to so-called multi-pattern photometry, which obtains the following values, is also conceivable. Next, an example in this case will be described.

For example, multi-pattern photometry is defined in USP 4.476,
For example, as shown in FIG. 18, a photometric sensor corresponding to the photographing screen is PO.

PL, P2. P3. It is composed of five photosensors P4 and detects the brightness distribution of the photographic screen based on the output of each. In this case, the number of divisions is five, but if the number of divisions is increased, the brightness distribution of the photographic screen can be detected more precisely, and more accurate exposure information can be obtained.

However, if the number of divisions is increased, the area of each photosensor will become smaller. As the area becomes smaller, the output current per unit brightness decreases accordingly, resulting in a problem that accurate exposure information cannot be obtained at low brightness. Therefore, it is necessary to use an accumulation-type two-dimensional image sensor, such as a two-dimensional CCD image sensor, that accumulates the charges generated by the photosensor.

Then, a problem arises when the subject is illuminated by a light source whose brightness changes in an AC manner, as in the case where spot photometry is performed using the output of the focus detection CCD image sensor described above.

FIG. 19 shows a configuration when this embodiment is applied to a single-lens reflex camera. L is the objective lens, HM is the half mirror, 15M is the submirror, FS is the focusing screen, PP is the pentaprism, IP is the eyepiece, A
E is a first photometry section, MAE is a multi-pattern photometry section including a two-dimensional CCD image sensor to be described later, and MP' is a microprocessor. Of the light beam that passes through the objective lens L, what is reflected by the half mirror HM forms an image on the focusing screen FS, and the photographer can observe this formed image as an erect image using the pentaprism PP through the eyepiece IP. . Then, the multi-pattern photometry unit MAE collects the luminance information of each subdivided area of the image on the focusing screen FS using the microprocessor MP'.
Output to.

On the other hand, among the light beams that have passed through the half mirror HM, those near the optical axis of the objective lens L are guided to the first photometry section AE by the submirror SM. The first photometric section AE may be the one shown in FIG. 4, or may be added to the focus detection module as shown in FIGS. 15, 16, and 17. Furthermore, the location where it is installed need not be limited to the bottom of the body as shown in FIG. 19.

Two-dimensional C used in multi-pattern photometry unit MAE
As shown in FIG. 20, the CD image sensor (SII=
It consists of a total of SI (xxy) sensor pixels,
It has a transfer section (not shown) that transfers charges generated and accumulated in each pixel. Charge signals generated in each pixel during a certain accumulation time are outputted in time series by the transfer section.

The microprocessor MP' inputs signals from the photometry unit AE and the multi-photometry unit MAE, calculates luminance information,
Exposure information regarding the appropriate amount of exposure for photographic film is calculated.

Next, in photometry using the output of the two-dimensional CCD image sensor of the multi-photometry unit MAE, we will discuss countermeasures against light sources whose brightness changes due to AC, such as fluorescent lamps, as shown in FIGS. 12 and 13 used in the above embodiment. This will be explained using figures.

In this embodiment, (1) and (2) in FIG. 12 indicate the timing at which the microprocessor MP' inputs the signal from the first photometry section AE, and (2) indicates the timing at which the two-dimensional CCD image sensor of the multi-photometry section MAE inputs the signal. Corresponds to accumulation time and timing. When the brightness of the subject is high and the accumulation time IT is short, as shown in FIG. 12(a), and IT<tp, the accumulation of the two-dimensional CCD image sensor is first performed by the first photometer at time TA. It starts almost at the same time as the signal is input from the AE, and ends the accumulation after IT time. Through this accumulation, the image obtained from the two-dimensional CCD image sensor (Sit~
Output from SI (OUTII~OUT!)
TII/IT ~ 0UTxy/IT), and the Bv value calculated from this is (E z II ~ EZ I
Suppose that it becomes T). On the other hand, in TA, the Bv value calculated from the data input from the first photometry section AE corresponds to Ha shown in Fig. 13, and the Bv value calculated from the average of 8 data including this data is shown in Fig. This corresponds to Hm shown by the dotted line inside. Photometering range of first photometering section AE and multi-metering section MA
Although the photometric range of E is different, the illuminating light source is considered to be the same, and Ha and (E z II - E z xy) are considered to be the subject brightness at almost the same time, so if the image sensor The Bv value (E
It is expected that the difference between mit ~ Emxy) and (E z 11 - E Z ! is almost equal to the difference between Hm and Ha mentioned above. Therefore, Emmn calculated by the following formula can be calculated using the two-dimensional CCD image of the multi-photometering section. Each pixel of the sensor corresponds to the photometric value of the corresponding area of the photographic screen.

Emmn=Ezmn+Hm−Ha (m=1., z,
n=1. ．． 7) In this way, since the two-dimensional CCD image sensor performs the accumulation only once, much faster photometry is possible than when the accumulation is performed multiple times.

Next, the brightness of the subject is lower than in the above case, and the storage time IT of the two-dimensional CCD image sensor is also longer, t
FIG. 12(b) shows the case where p IT<3×tp1. First, the two-dimensional CCD image sensor accumulates data at time TB.
The accumulation starts at the same time as the signal is input from the first photometry section AE, and ends after the IT time. A two-dimensional CCD image sensor obtained by this accumulation (8
Calculate (OUTII/IT-OUTxy/I'r) from the output (OUTII ~ 0UTx7) of
t7). Meanwhile, time TB occurred during IT.

The Bv values calculated from the data input from the first photometry section AE in TCSTD are shown in Figure 13 1': Hb
, Hc, and Hd, and the Bv value Hm calculated by averaging eight data including these data is obtained. Said (
Ez 11~Ez! 7) is from time TB to time TE
It can be said that the Bv value (Eml
It is expected that the difference between (1-Emxy) and (E z II to E Z IF) is approximately equal to the difference between the average values of Hm, :Hb, Hc, and Hd. Therefore, Emmn calculated by the following equation is taken as the photometric value of the area of the photographic screen to which each pixel of the two-dimensional CCD image sensor of the multi-photometering section corresponds.

Emmn=Ezmn+Hm-(Hb+Hc×Hd) ÷
3 (m=1., L n=l1.y) Furthermore, even if the brightness of the subject becomes lower and the storage time becomes longer, Emmn can be found in the same way as described above, but it is better to use a two-dimensional CCD image sensor. outputs the average brightness of the subject during the accumulation time, so if the accumulation time is longer than a certain point, the Bv calculated at this time
The value Ezmn can be used as it is as the photometric value of the area of the photographing screen to which each pixel of the two-dimensional CCD image sensor of the multi-photometering section corresponds.

[Effects of the Invention] As explained above, according to the present invention, in a photometry device that uses the output of an accumulation-type image sensor used for focus detection as luminance information of a subject, the luminance of a subject such as a fluorescent lamp periodically changes. Photometric information can be quickly obtained even when illuminated by a changing light source.

[Brief explanation of drawings]

Figure 1 is an overall view of a camera equipped with the photometric device of the present invention; Figure 2 is an explanatory diagram of the image sensor chip; Figure 3 is an explanatory diagram of the focus detection optical system; Figure 4 is an illustration of the photometric module AE. Figure; Figure 5 is an explanatory diagram showing the connection between the focus detection module AF, the first photometry module AE, and the microprocessor; Figure 6 is an explanatory diagram showing the timing of the operation of the image sensor chip; An explanatory diagram of the control unit; Figure 8 is a signal waveform diagram showing the photometric signal when the brightness of the light source changes periodically; Figure 9 shows the relationship between the accumulation time of the image sensor array, the subject brightness, and the output Explanatory diagram; Figure 10 is an explanatory diagram showing the range photometered by the image sensor array on the shooting screen; Figure 11 is an explanatory diagram showing the output of the image sensor array; Figure 12 is the output from the photometry module AE and a timing diagram of the output from the focus detection module AF; FIG. 13 is an output timing diagram of the brightness value Bv calculated from the output of the photometry module AE; FIG. 14 is an explanatory diagram showing an example of supporting the focus detection optical system ; Figures 15 to 17 are configuration diagrams of an embodiment in which the first photometry device is located near the focus detection module; Figure 18 is an explanatory diagram of multi-pattern photometry; Figure 19 is an illustration of the case where the present invention is applied. Configuration diagram of a single-lens reflex camera; FIG. 20 is a pixel arrangement diagram of a two-dimensional CCD image sensor used in the multi-pattern photometry section MAE of FIG. 19. Explanation of symbols of main parts AF: Focus detection module AE: Photometry module MP2 microprocessor

Claims (4)

[Claims] (1) In a camera having a non-storage type photoelectric conversion element and an accumulation type image sensor, a first photometric calculation means that calculates luminance information by inputting a light reception signal of the photoelectric conversion element at predetermined intervals; a second photometric calculation means for calculating average luminance information from which fluctuations due to the periodic light source have been removed based on an average value of light reception signals for a plurality of periods of the photoelectric conversion element inputted by the first photometry calculation means; the image sensor; a third photometric calculation means for calculating brightness information by inputting a signal obtained each time one accumulation is completed; A correction means for correcting the brightness information calculated by the third photometric calculation means to brightness information corresponding to the average value of the brightness information obtained by accumulating the brightness information a plurality of times in the image sensor; Photometering device. (2) In a camera having a photoelectric conversion element for photometry and an accumulation type image sensor for focus detection, a first photometry calculation means that calculates brightness information by inputting the light reception signal of the photoelectric conversion element at predetermined intervals. and; a second photometric calculation means for calculating average luminance information from which fluctuations due to the periodic light source have been removed based on the average value of the light reception signal for a plurality of cycles of the photoelectric conversion element inputted by the first photometry calculation means; a third photometric calculation means for calculating brightness information by inputting a signal obtained each time the image sensor completes one accumulation; based on the brightness information calculated by the first and second photometry calculation means; and a correction means for correcting the brightness information calculated by the third photometric calculation means to brightness information corresponding to the average value of the brightness information obtained by accumulating the brightness information a plurality of times by the image sensor; A photometric device featuring: (3) If the one-time accumulation time of the image sensor is shorter than the brightness information calculation cycle of the first photometric calculation means, the correction means adds the brightness information calculated by the third photometry calculation means to the second one. Correction is performed by adding the difference between the average luminance information calculated by the photometric calculation means and the brightness information calculated by the first photometry calculation means at approximately the same time as the completion of one accumulation of the image sensor. The photometric device according to claim 1. (4) If one accumulation time of the image sensor is longer than the brightness information calculation period of the first photometric calculation means, the correction means may include the brightness information calculated by the third photometry calculation means in the brightness information calculated by the third photometry calculation means. performing correction by adding a difference between the average luminance information calculated by the second photometric calculation means and the average value of the brightness information calculated a plurality of times by the first photometry calculation means during one accumulation of the image sensor; The photometric device according to claim 1, characterized in that: