JPH02125573A - Electronic still camera and strobo for electronic still camera - Google Patents

Abstract

PURPOSE:To avoid a picture of skipped white level or deformed black level by giving plural timing signals to a strobo within a pickup time of one frame at strobo pickup and applying electronic shutter operation on the way of at least one lighting in each lighting so as to adjust the quantity of light reception. CONSTITUTION:A strobo is lighted at each of exposure periods split into 5. Then the intensity of strobo lighting is varied to change the characteristic. When the lighting quantity at the 5th time is selected to be 1/4 of the lighting quantity of the 1st to 4th lighting, the generated charge by the 1st-4th strobo lighting is as shown in figure A and the generated charge by the 5th strobo lighting is as shown in figure B. Thus, when the charges for the 5 lightings are added, the characteristic shown in figure C is obtained. That is, a nu characteristic appears depending on the difference from the characteristics A, B. Thus, no saturation takes place even in an object with a high reflectance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electronic still camera and a strobe for the electronic still camera.

(Background of the Invention) In a normal electronic still camera, after exposing and accumulating light for a predetermined period of time in the light receiving section of a solid-state image sensor, the exposure ends by transferring the charge to the transfer section.During this exposure period, the strobe flash fires once. only emits light.

Conventional strobes use all of the charge stored in a capacitor to emit light, and others detect the reflected light from the subject and stop emitting light when it reaches an appropriate level.

(Problems to be Solved by the Invention) When photographing with a strobe, objects close to the camera or objects with high reflectance tend to be washed out.

Additionally, if you adjust the aperture to suit the subject or stop the auto flash midway through the shot, there is a problem that subjects that are a little further away or have low reflectance will be blacked out.

In such a case, it can be helped if the subject is far away and the strobe light cannot reach it at all, but it would be a problem if the subject was close to the camera and the subject turned out black just by moving a little away.

Such problems also occur when photographing with a normal light source. As a means to solve this problem, the Knee characteristic system #J of the RCCP image sensor was introduced in 1978 National Television Academic Conference, pages 43-44.

A proposal has been made in Japanese Patent Application No. 62-87393 filed by the applicant of the present invention. However, since all of these methods perform exposure in multiple steps, there is a problem in that they cannot support strobe photography in which the flash is fired only once in response to a trigger signal.

The present invention has been made in view of the above-mentioned problems, and its purpose is to
To realize an electronic still camera and a strobe for an electronic still camera in which the obtained image does not become white or black.

(Means for Solving the Problems) The invention according to claim 1 which solves the above problems is an electronic still camera that is used with a strobe that emits light in synchronization with an external timing signal and is equipped with a solid-state image sensor. When shooting with a strobe, multiple timing signals are applied to the strobe within the shooting time of one frame, and the amount of light received is adjusted by performing an electronic shutter operation of the solid-state image sensor during at least one of each flash. It is characterized by this.

The invention according to claim 2, which solves the above problem, is a strobe used with an electronic still camera equipped with a solid-state image sensor having an electronic shutter function. The present invention is characterized in that it is configured to receive a plurality of light emission start signals from a still camera and emit light a plurality of times.

The invention according to claim 3 which solves the above problem is an electronic still camera for taking still images, which is used with a strobe whose start and stop of light emission is controlled by a light emission start signal and a light emission stop signal from the outside. When shooting with a flash, multiple sets of flash start signals and flash stop signals are applied to the flash within the shooting time of one frame, and at least one other set of flash flash start signals and flash stop signals are applied to the flash during the time interval from the flash start signal to the flash stop signal. It is characterized in that it is configured to be different from the time interval.

The invention according to claim 4 which solves the above problem is a strobe used with an electronic still camera having a solid-state image sensor, wherein the strobe emits light by a light emission start signal and a light emission stop signal given from the electronic still camera during strobe photography. The device is characterized in that it is configured to start and stop light emission.

The invention according to claim 5, which solves the above problem, is configured to emit light a plurality of times within the photographing time of one frame, and the amount of light emission of at least one of the plurality of times of light emission is different from the amount of light emission of the other times. This electronic still camera is used together with a strobe, and is characterized in that it is configured to generate a light emission start signal so that the strobe fires multiple times.

The invention according to claim 6, which solves the above problem, is a strobe for an electronic still camera used with an electronic still camera, the strobe flash being used multiple times within the shooting time of one frame in synchronization with a light emission timing signal from the electronic still camera. The device is characterized in that it emits light and that the amount of light emitted at least one time out of the plurality of times of light emission is different from the amount of light emitted in the other times.

(Function) In the electronic still camera according to claim 1, when photographing with a strobe, the flash is emitted multiple times within the photographing time of one frame, and the electronic shutter of the solid-state image sensor is activated during at least one of each flash. The strobe for an electronic still camera according to claim 2, characterized in that the amount of light received is determined by performing an operation, when performing strobe photography, receives a plurality of light emission start signals from the electronic still camera within the photographing time of one frame, and Emits light.

The electronic still camera according to the third aspect of the present invention generates a plurality of strobe light emission start signals and a plurality of light emission stop signals within the photographing time of one frame during flash photography, and at least generates a plurality of strobe light emission start signals and light emission stop signals within the time interval from the light emission start signal to the light emission stop signal. Once is made to be different from other time intervals.

In the strobe for an electronic still camera according to the fourth aspect of the present invention, the start and stop of light emission of the strobe is controlled by a light emission start signal and a light emission stop signal given from the electronic still camera.

The electronic still camera according to claim 5 is characterized by a light emission start signal so that the strobe fires a plurality of times.The electronic still camera strobe according to claim 6 is characterized in that the strobe emits light for one frame in synchronization with the light emission timing signal from the electronic still camera. The light is emitted a plurality of times within the photographing time, and the amount of light emitted at least one time among the plurality of times of light emission is different from the amount of light emitted in the other times.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the overall structure of an embodiment of an electronic still camera according to the present invention. In the figure, 1 is a solid-state image sensor (hereinafter referred to as CCD) for converting an optical image formed by a lens system 11, which will be described later, into an electrical signal (image data).
, 10 is a strobe that emits light during shooting, 11 is a lens system for focusing the image of the subject on the CCDI, and 12 is the CCDI
13 is a process circuit for converting the output of the CCDI into a video signal, 14 is a recording circuit that converts the video signal into a signal for recording on the video floppy 15, and 16 is the output of the CCDI. 17 is a CPU that performs overall control of various parts in addition to exposure control; and 18 is a CCD drive circuit that drives the CCD 1. It is assumed that this CCD drive circuit 18 has an electronic shutter function that adjusts the shutter speed by adjusting the charge readout timing.

FIG. 2 is a time chart showing drive pulses when driving this CCDI. Note that the CCD drive circuit that generates this drive pulse can be realized by making some changes to a known circuit, and the detailed circuit configuration will be omitted.

FIG. 3 is a configuration diagram showing the configuration of the main parts of the CCD 1 used in the above-described embodiment. Here, a case will be described in which an interline CCD is used as the CCDI. In the figure, 2 is a light receiving section that generates charges according to the amount of received light, 3 is a vertical transfer section that transfers the charges generated in the light receiving section in the vertical direction, and 4 is a horizontal transfer section that transfers the charges from the vertical transfer section in the horizontal direction. This is the transfer section. Here, 3/4 pixels are shown.

It is also assumed that the potentials of the light receiving section 2 and the vertical transfer section 3 of this CCDI are as shown in FIG. 4 or 5. That is, it is assumed that the transfer section can store five times as much charge as the light receiving section.

The operation of the embodiment of the present invention will be described below with reference to FIGS. 1 to 5, focusing on driving the COD.

Assuming that A in FIG. 2 is the exposure period and B is the readout period, at the beginning of A, the charges of the pixels corresponding to φv1 to φv4 are transferred to the vertical transfer section 3, and then the charges are discarded by reverse transfer.

Thereafter, charges are transferred from the light receiving section 2 to the vertical transfer section 3 in five times (Tl, T2T3.T4.T5), and the sum added on the vertical transfer section 3 is read out during period B. This 5
Fire the strobe during each divided exposure period (
Figure 2 (d) to (g)). By changing the intensity of this strobe light emission (FIG. 2 (e) to (g)), the characteristics can be changed.

If the amount of light emission is set equally for five times as shown in (d),
This is the same as normal readout using conventional strobe light emission (FIG. 2 (h)).

In addition, when only the fifth flash emission amount is reduced as in strobe light emission 2 (Figure 2 (E)), the reflectance of the subject and the CC
The relationship between the output charges of D1 is as shown in FIG. Here, a case will be described in which the amount of light emitted at the fifth time is 1/4 of the amount of light emitted at the first to fourth times. The charges generated by the first to fourth strobe light emissions are as shown in FIG. 6A, and the charges generated by the fifth strobe light emission are shown in FIG. 6B. Therefore,
When the charges for five times are added, the characteristic shown in FIG. 6C is obtained. That is, two characteristics appear due to the difference in characteristics between A and B.

Therefore, even objects with high reflectance will not be saturated.

In addition, when the ratio of the respective light emission amounts is set to 16:18:4:4:1 as in strobe light emission 3 (see Figure 2), the relationship between the reflectance of the subject and the output charge of the CCDI is 7 It becomes like a plan. The charges generated by the first and second strobe lights are as shown in Figure 7A, the charges generated by the third and fourth strobe lights are as shown in Figure 7B, and the charges generated by the fifth strobe light are as shown in Figure 7B. It will look like Figure 7C. Therefore, if the charges for five times are added, the characteristics shown in Figure 7 will be obtained. In other words, due to the difference in the characteristics of A, B, and C,
Knee characteristics appear. Therefore, the output does not become saturated even for objects with high reflectance.

In addition, when the ratio of the respective light emission amounts is set to 16:4:4:4:1 as in strobe light emission 3 (see Figure 2), the relationship between the reflectance of the subject and the output charge of the CCDI is It will look like Figure 7E. The charges generated by the first strobe light emission are as shown in FIG. 7A, and 2. 3. The charges generated by the fourth strobe light emission are as shown in FIG. 7B, and the charges generated by the fifth strobe light emission are shown in FIG. 7C. Therefore, when charges for five times are added, the characteristic shown in FIG. 7E is obtained. In other words, due to the difference in the characteristics of A, B, and C,
Knee characteristics appear. Therefore, the output does not become saturated even for objects with high reflectance.

As mentioned above, by changing the amount of light emitted by the strobe,
It is possible to obtain various other characteristics besides these.

FIG. 8 is a circuit diagram showing the circuit configuration of an ordinary strobe for reference. The operation of this strobe is as follows. When the main switch SWM is turned on, the booster circuit 10
The power supply voltage E is boosted by a, and the capacitor C1 is charged. When the voltage charged in the capacitor C8 reaches a predetermined value, the neon tube Ne lights up to notify that charging is complete. At this time, when SWx is turned on by the X contact signal from the camera, a spike-like voltage is applied to the discharge tube Xe due to the discharge current of the capacitor Cs. This spike-like voltage serves as a trigger for starting discharge, and the charge in the capacitor CI flows through the discharge tube, causing discharge (light emission). Capacitor C
When the charge of 1 is exhausted, discharging ends.

FIG. 9 is a circuit diagram showing the circuit configuration of a strobe according to the present invention. In this configuration, the charging capacitors are C+, C2,
There are five switches Ci, C4, and C5, and the switches sWc are switched by instructions from the controller 10b. Therefore, by adjusting the capacitance of each capacitor,
The light emission characteristics shown in FIGS. 2(d) to (g) can be easily achieved.

FIG. 10 shows the controller 10b and switch SWc.
FIG. 2 is a circuit diagram showing an example of the configuration. Further, FIG. 11 is a time chart during operation of the controller 10b. One-shot multi-MMI receives the X-contact signal from the electronic still camera, and has a longer firing time (approximately 1 ms) than the strobe light emission time.
generates a pulse. And one shot multi MM
2 receives this pulse and generates a pulse synchronized with the falling edge of the MMI output pulse. The 2-bit counter receives this output pulse of MM2 and generates C,,C,,carry. And 2t04 decoder and inverter I
Pulses D with different phases from NV. + DI +
D2 + D3 + D4 is output.

These pulses D. ,D, ,D, ,D3. D4 controls on/off of the switch SWC. In the case of Figure 11,
Pulse D. ,D,,D2. D3. When D4 is at a low level, each contact of the switch SWo is turned on. In this way, multiple capacitors of the strobe are switched by the X-contact signal from the electronic still camera, and light is emitted multiple times.

FIG. 12 is a circuit diagram showing another example of the circuit configuration of the strobe according to the present invention. In this configuration, the controller 10b controls the start and stop of light emission, thereby allowing a single capacitor to perform light emission control multiple times. That is, the light emission starts when the switch SWX is turned on, and the light emission is stopped by turning off the switch SWK during the light emission, and the amount of light emission is adjusted. Therefore, by controlling the timing at which the switch SWK is turned off, each amount of light emission can be adjusted. FIG. 13 is a time chart when performing such control. In this example, only the amount of light emission at the fifth time is small.

FIG. 14 is a circuit diagram showing an example of the configuration of the strobe controller shown in FIG. 12. Here, except when the 2-bit counter has a carry, the strobe emits light during the longer pulse of the one-shot multi MM2. Light emission is stopped at the falling edge of the output pulse of the one-shot multi-MM4.

When a carry is out, one shot multi MMI
Light emission is performed for a short pulse period of , and light emission stops at the falling edge of the output pulse of the one-shot multi-MM4.

Furthermore, since the start of light emission is always performed at the rising edge of the one-shot multi-MM3, it is necessary to make this pulse width longer than the full light emission time of the strobe.

Note that it is also possible to control the strobe directly from the electronic still camera side without disposing a controller on the strobe side. Therefore, the controller 10b is removed from the strobe 10 of FIG. 12, and the switches SWx and SWK are controlled by the signals shown in FIG. 15. In this case, both switches may be turned on when the signal shown in FIG. 15 is at a low level.

Another option is to keep the strobe light output the same each time and adjust the amount of light received by the electronic still camera. For this purpose, adjusting the aperture may be considered, but if high speed is required, CCD electronic shutter operation is appropriate. FIG. 16 shows an example of such an electronic shutter operation.

Here, charges are read out from the light receiving section of the CCD in the middle of the fifth strobe light emission (FIG. 16 (e)). Therefore, the light emission after the charge readout in the middle of the fifth light emission (FIG. 16(e)) does not contribute to image formation. Therefore, it is essentially the same as the amount of light emission being reduced for the fifth time. Therefore, the same effect as in the case of light emission shown in FIG. 2(e) can be obtained.

FIG. 17 is a time chart when charge reading is performed during the 3rd, 4th, and 5th strobe flashes.

In this case, the charge generated in the light receiving section after the electronic shutter operation during the third and fourth light emission is drained into the overflow drain (
I try to throw it away in OFD. For this reason, a control pulse is added to the overflow control gate (OFCG), and when this pulse is at a high level, 0FC
The level of G drops and the charge is dumped into the OFD.

FIG. 18 is a time chart in the case where the charge is discarded up to the middle of the 3rd, 4th, and 5th strobe flashes.

In this case, the strobe fires at 3.4° and 0.0° just before the 5th flash.
Keep FCG at high level and set it to low level during light emission. As a result, the charges during the 0FCG high level period are discarded to the OFD, and the charges during the 0FCG low level period are accumulated and read out. Therefore, by adjusting the low level period of this 0FCG, the effective value of the amount of light emission is adjusted.

In the above description, a case has been described in which the amount of light emitted each time is determined in advance, but it is also possible to make this amount of light emitted variable. For example, it is possible to perform an operation similar to an auto strobe (a strobe that receives reflected light from a subject, integrates it, and stops emitting light when the integrated value reaches a certain value).

In other words, instead of controlling the light emission each time by the amount of light emitted, a method may be considered in which the light emission is controlled by the photometric integral value of the reflected light from the subject. For example, in the case of strobe light emission 4 in Fig. 2 (g), the ratio of the light emission amount each time was controlled to be 16:4:1.
The first time is a certain value V. , 2, 3. The fourth time is V. /4.5th time is V. /16, the light emission is stopped. In this case, control as shown in FIGS. 15 and 17 is possible. In addition, as a variation of this, it is also possible to perform photometry only once at 11, store the amount of light emitted from this first time, and control the amount of light emitted from the second time onwards so that it is a constant ratio with the memorized value. .

A possible method is to always emit a constant amount of light for the first time, measure the light at that time, and control the amount of light emitted from the second time onwards according to the result. In the case of an autostroboscopic method, the response of the photometric circuit must be fast,
In the case of this method, it does not matter if it is slow. - For example, if the photometry result is a standard value, the ratio of the amount of light emitted each time is 18:4:
1. If the photometry result is a small value, the ratio of the amount of light emitted each time is set to 1.
6=8:2 If the JPI light result is a large value, the ratio of the amount of light emitted each time is set to 18:21.5. The characteristics at this time are
It is shown in Figure 9. In the figure, the horizontal axis represents the reflectance of an object at a certain distance, and the vertical axis represents the amount of signal charge. The characteristics when the luminescence amount ratio is 1B:8:4:2:1:o and 5 are ■, ■, ■, and ■, respectively.

■, ■, the characteristic when the three times of light emission is 16:4:l is A, the characteristic when the third time of light emission is 16:11:2 is B,
The characteristic when three times of light emission is 16:lo, 5 is C.

Here, in the case of ■ and C, the signal does not saturate up to the subject with a reflectance of 200%. This object with a reflectance of 200% corresponds to an object with a reflectance of 100% located at a distance IA/7. When the first light emission is photometered, and the result is a small value, it means that the subject is dark, that is, there are not many subjects with high reflectance, and there is no need to strengthen the knee characteristic. Therefore, in this case, characteristic B is sufficient, and 2
Controls the light emission after the first time. If the photometry result from the first light emission is a large value, the opposite is true, and control is performed so that the C characteristic can be used even for objects with high reflectance and close distances. Here, the exposure control is performed in three stages, but the accuracy of exposure control can be improved by continuously changing the ratio of the amount of light emitted each time according to the photometric value. Control method on the electronic still camera side (electronic shutter operation 1)
The same applies to light emission start/stop control).

It is also possible to emit preliminary light in advance and change the amount of light emitted by referring to the photometry results at that time. Since the multivalued light emission is performed before the photographing field, it is also possible to select the optimum light emission amount from the first light emission. However, 1. For preliminary light emission, it is necessary to increase the capacitance of the capacitor c1.

In the above description, the strobe light is emitted multiple times when the CCD is read out multiple times in one field period, but the strobe of the present invention can also be used in other cases. For example, the strobe of the present invention can also be used in a CCD such as that proposed in "Knee Characteristic Control of rCCD Image Sensor", 1978 National Conference of the Society of Television Engineers, pp. 43-44. FIG. 20 is an explanatory diagram showing the relationship between the charge storage characteristics of the proposed CCD and the X contact signal. In other words, the maximum amount of accumulated charge that can be stored in the light receiving section is increased during light reception (V I-V
2, Vz −Vy ) (7) gives j5. Therefore, each time the maximum accumulated charge amount is changed, the strobe light is emitted.

In addition, Figure 21 is a patent application filed by the applicant in Japanese Patent Application No. 62-8739.
The charge storage characteristics of the rCCD drive circuit proposed in No. 3 are as follows.
FIG. 3 is an explanatory diagram shown together with an X contact signal for controlling the strobe of the present invention. In this proposal, the Knee characteristic is obtained by fixing the maximum accumulated charge amount and discarding a certain amount of charge during light reception. In this case as well, good results can be obtained by causing the strobe of the present invention to emit light multiple times.

In the above explanation, the electronic still camera and the strobe are described as being separate, but it is also possible to use an electronic still camera with a built-in strobe. Furthermore, when an electronic still camera has a built-in strobe, control becomes easier.

(Effects of the Invention) As described above in detail, in the electronic still camera of the present invention, the strobe is emitted multiple times within the imaging time of one frame, and the charge is read out multiple times, and the amount of light emitted or the electronic shutter is adjusted. The amount of light received can now be adjusted through control.

Therefore, the output of the CCD is not saturated even in a high brightness region, and the dynamic range is widened. Therefore, even if there are differences in reflectance or distance, it is possible to realize an electronic still camera that does not produce images that are too white or too dark.

Further, in the strobe for an electronic still camera of the present invention, the strobe is emitted multiple times within the photographing time of one frame, and the amount of light emitted at least - times is different from the others. For this reason, the CCD output does not saturate on the electronic still camera side,
The dynamic range is expanded. Therefore, it is possible to realize a strobe for an electronic still camera in which images obtained by the electronic still camera do not appear white or black even if there are differences in the reflectance or distance of the subject.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a schematic structure of an electronic still camera, Fig. 2 is a time chart showing waveforms during operation of the device of the present invention, Fig. 3 is an explanatory diagram showing a schematic structure of a CCD, and Fig. 4 and Fig. 5 is an explanatory diagram showing the potential of CCD, Fig. 6 is an explanatory diagram showing the potential of CCD.
Figures 8 and 7 are characteristic diagrams showing the output characteristics of the COD, Figures 8 and 9 are circuit diagrams showing the strobe circuit configuration, and Figure 10 is a characteristic diagram showing the output characteristics of the COD.
The figure is a circuit diagram showing an example of the circuit of a strobe controller. Figure 11 is a time chart when the controller is operating.
Figure 2 is a circuit diagram showing another example of the strobe circuit configuration.
FIG. 3 is a time chart showing the strobe control status, FIG. 14 is a circuit diagram showing another example of the controller circuit, FIGS. 15 to 18 are time charts showing the strobe and CCD control status, and FIG. FIG. 19 is a characteristic diagram showing an example of charge storage characteristics according to the present invention, and FIGS. 20 and 21 are C
FIG. 3 is an explanatory diagram showing the relationship between the light receiving characteristics of a CD and the X contact signal. 1... CCD 2... Light receiving section 3...
Vertical transfer section 4... Horizontal transfer section 10... Strobe 10b... Controller 12... Amplifier 14... Recording circuit 15... Video floppy 16... Photometry circuit 18... CCD drive circuit 10a. ... Boost circuit 11 ... Lens system 13 ... Process circuit 17 ... CPU

Claims (6)

[Claims] (1) An electronic still camera equipped with a solid-state image sensor that is used with a strobe that emits light in synchronization with an external timing signal, and when shooting with a strobe, multiple timing signals are given to the strobe within the shooting time of one frame. . An electronic still camera characterized in that the amount of received light is adjusted by performing an electronic shutter operation of a solid-state image sensor during at least one of each light emission. (2) A strobe that is used with an electronic still camera equipped with a solid-state image pickup device that has an electronic shutter function, and when performing strobe photography, multiple flash start signals from the electronic still camera are sent within the shooting time of one frame. A strobe for an electronic still camera, characterized in that it is configured to emit light multiple times. (3) Used with a strobe whose start and stop of light emission is controlled by an external light emission start signal and a light emission stop signal,
An electronic still camera for taking still images, which applies multiple sets of strobe light emission start signals and light emission stop signals to the strobe within the shooting time of one frame during strobe photography, and also applies a light emission stop signal from these flash emission start signals. An electronic still camera characterized in that at least one of the time intervals is configured to be different from other time intervals. (4) A strobe to be used with an electronic still camera having a solid-state image sensor, configured so that the strobe starts and stops firing in response to a flash start signal and a flash stop signal given from the electronic still camera during strobe photography. This is a strobe for electronic still cameras. (5) An electronic still camera that is used with a strobe that emits light multiple times within the shooting time of one frame and is configured such that the amount of light emitted at least one time among these multiple times is different from the amount of light emitted by the other flashes. An electronic still camera characterized in that the electronic still camera is configured to generate a light emission start signal so that the strobe light emits multiple times. (6) A strobe for an electronic still camera used with an electronic still camera, which emits light multiple times within the shooting time of one frame in synchronization with a flash timing signal from the electronic still camera, and which flashes multiple times within the shooting time of one frame. A strobe for an electronic still camera, characterized in that the amount of light emitted at least one time is different from the amount of light emitted at the other times.