JPH07167646A - Distance measuring equipment - Google Patents

Abstract

PURPOSE:To extend applicability to external luminance, and to measure a distance with high accuracy at all times. CONSTITUTION:An active distance measuring section A measuring a distance according to an active system and a passive distance measuring section P measuring the distance according to a passive system are provided. Whether or not external luminance obtained by a luminance decision section L is at a high luminance level or a low luminance level is discriminated in a distance- measuring value selecting circuit 40. Consequently, the result of the distance measurement of the active distance measuring section A is selected as a proper distance-measuring value when the external luminance is decided as low luminance and the result of the distance measurement of the passive distance measuring section P is selected as the proper distance-measuring value when the external luminance is judged as high luminance in the distance-measuring value selecting circuit 40, and each selected distance-measuring value is output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for a camera which automatically measures the distance to a subject.

[0002]

2. Description of the Related Art As a distance measuring device for such a camera,
There is known a triangulation type active system that has a distance measuring light source such as an LED and measures the distance to a subject in combination with a light receiving element.

Further, as a distance measuring device of another system, a natural light reflected by a subject is received by two optical systems without a light source for distance measurement, and two optical images obtained by each optical system. There is known a triangulation type passive method for measuring a distance to a subject based on the phase difference of the.

[0004]

The active type distance measuring device receives the distance measuring light returning from the subject in this way and measures the distance to the subject. However, when the ambient brightness is high, the light receiving element detects this distance. In some cases, the reflected light of the distance light cannot be received well, the accuracy of distance measurement deteriorates, or the distance measurement becomes impossible depending on the external brightness. On the other hand, when the ambient brightness is low, the passive range finder also naturally reduces the amount of natural light reflected from the subject, which makes it difficult to detect the phase difference, which reduces the range accuracy and reduces the range. It may be impossible.

The present invention has been made to solve the above problems, and an object thereof is to provide a distance measuring device which has a wide range of application to external luminance and can always perform distance measurement with high accuracy. Especially.

[0006]

Therefore, the distance measuring apparatus according to the present invention receives the reflected light of the distance measuring light returning from the subject and measures the distance based on the focus position thereof. The distance measuring section and the two distance measuring sections of the passive type second distance measuring section for measuring the distance based on the two optical images obtained by receiving the natural light reflected by the subject with the two optical systems. Prepare A brightness determination unit that determines the external brightness from the photometric result is provided, and the distance measurement results obtained by the first distance measurement unit and the second distance measurement unit based on the external brightness determined here. A distance measurement value selecting means for selecting and outputting one of the distance measurement results as an appropriate distance measurement value is configured.

Further, in this distance measuring value selecting means, the external brightness obtained by the brightness determining section is set to a high level or a low level.
You may distinguish in stages. Then, when the external brightness is determined to be a low level, the distance measurement result of the first ranging unit can be selected, and when the external brightness is determined to be a high level, the ranging result of the second ranging unit can be selected. .

Further, the distance measurement value selecting means may discriminate the external luminance obtained by the luminance judging section into three levels of high level, intermediate level and low level. Then, when the external brightness is determined to be a low level, the ranging result of the first ranging unit is selected, and when the external brightness is determined to be a high level, the ranging result of the second ranging unit is selected to determine the external luminance. Is determined to be an intermediate level, one of the distance measurement results obtained by the first distance measuring unit and the second distance measuring unit is determined based on the value of the predetermined parameter obtained by the measurement. The distance measurement result may be selected as an appropriate distance measurement value.

[0009]

The distance measuring device according to the present invention is provided with two types of distance measuring units, that is, the first distance measuring unit of the active type and the second distance measuring unit of the passive type, both of which perform the distance measurement. And
The brightness determination unit determines the external brightness, and based on this result, the distance measurement value selection means selects one of the distance measurement results as an appropriate distance measurement value. That is, when it is determined that the ambient brightness is relatively high, the light receiving element that receives the distance measuring light does not function well in the active method, but the passive method increases the amount of natural light reflected by the subject, and The reliability of the distance value is high, and as a result, the distance measurement result of the second distance measuring unit by the passive method is selected. On the other hand, when it is determined that the external brightness is relatively low, the passive method has a small amount of natural light reflected and lacks reliability, but the active method detects well the reflected light of the distance measuring light in the light receiving unit. Therefore, the reliability of the distance measurement value is high, and as a result, the distance measurement result of the first distance measuring unit by the active method is selected.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of the distance measuring apparatus according to this embodiment. This range finder includes an active range finder A for performing triangulation type active range finder, and a passive range finder P for similarly performing triangulation type passive range finder, and further includes an external environment. A brightness determination unit L that determines brightness and a distance measurement value selection circuit 40 are provided.

The active distance measuring section A includes a light projecting section 11 composed of an LED or the like for projecting distance measuring light toward a subject and a light receiving section 12 composed of a PSD or the like for receiving the reflected light (see FIG. 3). In addition, a distance measurement calculation circuit 13 for calculating the distance to the subject based on the results of light projection and light reception is further provided.

The passive distance measuring unit P includes a right light receiving unit 21 and a left light receiving unit 22 (see FIG. 3) for receiving reflected light of natural light from a subject by two optical systems, and further through these. A CCD (optical position detection device: not shown) that receives the two optical images obtained, and a distance measurement calculation circuit 23 that calculates the distance to the subject based on the results are provided.

The brightness determination section L is a light receiving element for exposure control,
For example, a light receiving section 31 made of CdS or the like and a photometric calculation circuit 32 for calculating the external luminance based on the light reception result are provided.

The distance measurement value selection circuit 40 is provided with the luminance determination section L.
It is a circuit that selects and outputs one of the distance measurement values measured by the distance measurement units A and P according to the external brightness obtained in step S1.

FIG. 3 shows the external appearance of a camera equipped with the distance measuring device according to this embodiment, and FIG. 4 shows the outline of its internal mechanism. The distance measurement calculation circuits 13 and 23 shown in FIG.
The photometric calculation circuit 32 and the distance measurement value selection circuit 40 are configured in the CPU shown in FIG.

The operation of the distance measuring device will be described with reference to FIG.

First, the release switch (not shown) is turned on.
When N is performed (# 100), both the active distance measuring unit A and the passive distance measuring unit P start distance measurement (# 10).
2). Further, at the same time as, or before or after this process, the external brightness is measured by the brightness determination unit L (# 104). In the distance measuring value selection circuit 40, first, the passive distance measuring unit P
It is determined whether or not the distance measurement calculation is possible (# 106).
This is because the distance measurement is performed in the passive distance measurement depending on the pattern of the subject. For example, when the subject has repeated vertical stripe patterns or a uniform brightness surface, it is impossible to calculate the distance based on the passive distance measurement. This is because # 10
If it is determined that the distance cannot be detected by 6, the distance measurement value of the active distance measurement unit A is immediately selected and output from the distance measurement value selection circuit 40 (# 108, # 110). Subsequent shooting processing is executed based on this distance measurement value.

On the other hand, when the distance can be measured by the passive distance measuring unit P (“NO” in # 106), it is judged whether the external brightness obtained by the brightness judging unit L is a high brightness level of Lv14 or higher. (# 114). When the external brightness is high, in the active method, the light receiving unit 12 cannot properly receive the reflected light of the distance measuring light, which may reduce the distance measuring accuracy. On the other hand, in the passive method, the amount of natural light reflected by the subject increases, so the reliability of the distance measurement value is high. Therefore, the distance measurement value selection circuit 40 immediately selects the distance measurement value of the passive distance measurement unit P when the external luminance obtained by the luminance determination unit L is Lv14 or higher (# 116, # 110). Subsequent shooting processing is executed based on this distance measurement value output from the distance measurement value selection circuit 40 (# 112).

When the external brightness is less than Lv14 ("NO" in # 112), it is determined whether or not the external brightness is lower than Lv3 (# 118). When the ambient brightness is low, the passive method has a small amount of reflected natural light and lacks reliability, but the active method has high reliability of the distance measurement value because the reflected light of the distance measuring light is well detected in the light receiving unit 12. Therefore, the distance measurement value selection circuit 40 determines that the external brightness obtained by the brightness determination unit L is Lv3 or less (# 11
8 "YES"), the distance measurement value of the active distance measuring unit A is immediately selected and output (# 108, # 110).

In the case where the external luminance is a high luminance level of Lv14 or higher or a low luminance level of Lv3 or lower, the distance measurement value selection circuit 40 immediately selects one of the distance measurement values as described above. Select, but the brightness level is 3 <Lv
When the intermediate brightness level is <14, the selection is made based on the values of the following parameters.

First, the distance measurement value selection circuit 40 determines whether or not the contrast is low (# 120). In # 106, when it is determined that the distance measurement can be performed by the passive distance measurement unit P, but it is determined that the contrast is low from the sensor data of the AE (automatic exposure, see FIG. 4) including the luminance determination unit L, (“YES” in # 120), the distance measuring value selection circuit 40 immediately selects the distance measuring value of the active distance measuring unit A (# 10).
8). This is because in the case of passive distance measurement, the distance measurement result depends on the contrast of the subject, and for a subject with uniform brightness (low contrast), the distance measurement accuracy may decrease or the distance may not be able to be measured. Because. On the other hand, in the case of active distance measurement, even if the subject has low contrast, there is no such drawback. Therefore, the distance measurement value selection circuit 40 is set to select a more reliable distance measurement value of the active distance measurement unit A when the contrast is low.

Next, when the contrast is not low ("NO" in # 120), the determination is made based on the temperature. That is, it is determined whether the air temperature is a high temperature exceeding 40 ° C. (# 122) or a low temperature below 0 ° C. (# 124). This is because the components that make up the internal optical system provided inside the camera undergo thermal expansion and contraction depending on the temperature. Due to this thermal expansion and the like, the optical path length from the light emitter to the light receiver changes, but the optical path length of the passive distance measuring section P is much shorter than the optical path length of the active distance measuring section A. Therefore, when the temperature is low or high, the error in the distance measurement result of the passive distance measuring unit P becomes significantly large. Therefore, if either # 122 or # 124 is satisfied, the distance measurement value selection circuit 40 immediately selects the distance measurement result of the active distance measurement unit A (# 108).

If neither # 122 nor # 124 applies (“NO” in # 122 and # 124), the distance measuring value selection circuit 40 determines whether the distance measuring result of the active distance measuring unit A is 3 m or more. Is determined (# 126). This is because the active method projects distance measuring light toward the subject and receives the reflected light, so there is a limit to the distance that the distance measuring light can be projected, and reflection occurs when the distance to the subject is long. In some cases, sufficient light cannot be obtained, the accuracy of distance measurement deteriorates, or distance measurement becomes impossible. Therefore, the distance measurement value selection circuit 40 determines that the distance measurement result of the active distance measuring unit A is 3 m or more (“Y” in # 126).
ES ”), and selects the distance measurement value of the passive distance measuring unit P (# 11
6) If it is closer than 3 m (# 126: "N
O ”), and selects the distance measurement result of the active distance measuring unit A (#
108).

As described above, one distance measuring value is finally selected, and the photographing process is executed based on the distance measuring value selected by the distance measuring value selecting circuit 40.

Thus, the distance measuring device according to the present embodiment is
Among the distance measurement values obtained by the active distance measurement unit A and the passive distance measurement unit P, a more reliable distance measurement value is selected as an appropriate distance measurement value according to the external brightness and the like.

In the embodiment described above, the external luminance is set to Lv.
A high brightness level of 14 or higher, a low brightness level of Lv3 or lower,
Although an example in which the determination is made in three stages of the intermediate luminance level of 3 <Lv <14 is shown, in addition to this, it is also possible to discriminate the outside luminance in two stages of a high luminance level and a low luminance level. Is. In this case, the reference brightness level is Lv1.
A value of about 2 is a desirable value. That is, when the external brightness is Lv12 or more, the distance measurement result of the passive distance measuring unit P is selected, and when it is less than Lv12, the distance measurement result of the active distance measuring unit A is selected as an appropriate distance measurement value. To do. It should be noted that each of these brightness levels is merely an example of the most preferable value, and it is of course possible to use other values.

Further, in the present embodiment, the brightness determining section L can utilize the structure of the AE (automatic exposure) section in FIG.
In addition to this, a light receiving unit and a photometric calculation circuit are provided separately from the AE unit as the brightness determining unit, or, as shown in FIG. 2, the light receiving units 21 and 22 of the passive distance measuring unit P receive light. It is also possible to obtain the external luminance by the photometry / distance measurement calculation circuit 24 based on the result.

[0029]

As described above, the distance measuring apparatus according to the present invention comprises the active first distance measuring section and the passive second distance measuring section, and the brightness determining section and the distance measurement value selecting means. Therefore, either one of them is selected as an appropriate distance measurement value depending on the external brightness. Therefore, it is possible to provide a distance measuring device which has a wide application range with respect to external luminance and can always perform distance measurement with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a configuration of a distance measuring device according to an embodiment.

FIG. 2 is a block diagram showing another embodiment of the distance measuring device.

FIG. 3 is a front view showing a camera provided with the distance measuring device according to the present embodiment.

FIG. 4 is a block diagram schematically showing an internal configuration of a camera.

FIG. 5 is a flowchart showing an operation of the distance measuring device according to the present embodiment.

[Explanation of symbols]

A ... Active distance measuring unit (first distance measuring unit), P ... Passive distance measuring unit (second distance measuring unit), L ... Luminance determining unit, 40 ... Distance measuring value selection circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G02B 7/30 G03B 13/36

Claims (3)

[Claims] 1. An active type first distance-measuring unit for projecting distance-measuring light toward a subject and measuring the distance to the subject based on the condensing position of the reflected light, and reflected by the subject. 2nd optical system that receives natural light from two optical systems and measures the distance to the subject based on the two optical images obtained by each optical system. Based on the external brightness determined by the brightness determination unit and the first brightness determination unit.
Distance measuring value selecting means for selecting one of the distance measuring results obtained by the distance measuring unit and the second distance measuring unit as an appropriate distance measuring value and outputting the selected distance measuring value. Distance measuring device characterized by. 2. The distance measuring value selecting means determines the external brightness obtained by the brightness determining section into two levels, a high level and a low level, and when the external brightness is determined to be the low level, The first
2. The distance measuring device according to claim 1, wherein when the distance measuring result of the distance measuring unit is selected and the external luminance is determined to be the high level, the distance measuring result of the second distance measuring unit is selected. . 3. The distance measuring value selecting means determines the external luminance obtained by the luminance determining section into three levels of high level, intermediate level and low level, and determines the external luminance to be the low level. In the first
When the distance measurement result of the distance measuring unit is selected and the external luminance is determined to be the high level, when the distance measurement result of the second distance measuring unit is selected and the external luminance is determined to be the intermediate level, , Based on the value of the given parameter obtained by the measurement,
The distance measuring result according to claim 1, wherein one of the distance measuring results obtained by the first distance measuring unit and the second distance measuring unit is selected as an appropriate distance measuring value. Distance device.