JPH0695200A - Photometry controller for camera - Google Patents

Abstract

PURPOSE:To provide a photometry controller for a camera capable of obtaining an accurate exposure value by performing small number of times of photometry by controlling the storage time of a photoelectric conversion element to an optimum value so that a photometric value may not exceed or lower an upper limit value or a lower limit value to the utmost. CONSTITUTION:This photometry controller for the camera is provided with photometry means 7 and 9 outputting a photometric signal concerning the brightness of each photometric area by performing photometry after dividing an object field to plural photometric areas by plural storage type photoelectric conversion elements; and an exposure value is obtained based on the plural photometric signals by the photometry means. It is equipped with a storage time arithmetic means 13 obtaining the storage time at the time when next photometry is performed by the photoelectric conversion element by using at least either the maximum value or the minimum value of plural photometric signals, and a control means 14 actuating the photoelectric conversion element based on the storage time obtained by the means 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photometric control device for a camera, which divides an object field into a plurality of regions by using a plurality of storage-type photoelectric conversion elements to perform photometry.

[0002]

2. Description of the Related Art Conventionally, storage type photoelectric conversion elements (for example,
As a photometric device for a camera that performs photometry using a CCD),
For example, the one disclosed in JP-A-62-259022 is known. This device uses an integral photoelectric conversion element used for focus detection for photometry, and averages a plurality of integration times by the photoelectric conversion element, and obtains a subject brightness value based on the average value. is there. That is,
The lower the brightness of the subject, the longer the storage time of the photoelectric conversion element, so if the storage time is set so that the output of the photoelectric conversion element becomes a constant value, the brightness of the subject can be obtained from the storage time. it can.

[0003]

In such a conventional photometric device, since the photometric element and the focus detecting element are used in common, there are the following problems. That is, the first purpose is to detect the contrast of the subject in order to detect the focus, and it does not matter what the absolute value of the output value is as long as the contrast can be detected. Speaking extremely, for example, as shown in FIGS. 10A and 10B, contrast information can be obtained even if all but one output of the plurality of photoelectric conversion outputs are the upper limit value or the lower limit value. If there is no problem.

On the other hand, when the output of the photoelectric conversion element is used as a photometric signal, its absolute value becomes a problem, and when the output includes a large number of upper limit values or lower limit values, those values are required. Since there is a high possibility that the value is above the upper limit or below the lower limit, it cannot be said that it accurately reflects the brightness value of the subject. In particular, since the dynamic range of the photoelectric conversion element is usually smaller than the measurable range required by the photometric device, it is highly possible that the output of the element contains a large number of upper limit values or lower limit values in one photometry. Since the above-described conventional photometric device does not consider such a problem at all, an accurate luminance value may not be obtained unless the photometry is performed a plurality of times depending on the brightness of the subject.

An object of the present invention is to control the storage time of the photoelectric conversion element to an optimum value so that the photometric value does not exceed the upper limit value or the lower limit value as much as possible, and to obtain an accurate luminance value with few photometric operations. It is to provide a photometric control device for a camera.

[0006]

SUMMARY OF THE INVENTION The present invention is a photometric means for dividing a field into a plurality of photometric regions by means of a plurality of storage-type photoelectric conversion elements for photometry and outputting a photometric signal relating to the brightness of each photometric region. The present invention is applied to a photometric control device for a camera, which is provided with the above-mentioned photometric means and obtains an exposure value based on a plurality of photometric signals. Then, using at least one of the maximum value and the minimum value of the plurality of photometric signals, a storage time calculating means for obtaining a storage time at the next photometry of the photoelectric conversion element, and a storage time obtained by the storage time calculating means. And a control means for operating the photoelectric conversion element at a time,
This solves the above problem. Particularly, the second aspect calculates the accumulation time so that the average value of the maximum value and the minimum value of the photometric signal becomes an intermediate value of the photometric range of the photoelectric conversion element at the next photometry. According to a third aspect of the present invention, when the maximum value of the photometric signal is the upper limit value of the photometric range of the photoelectric conversion element, the number of the maximum values is counted, and the accumulation at the next photometry is performed based on the count value. It calculates time. Further, according to claim 4, when the minimum value of the photometric signal is the lower limit value of the photometric range of the photoelectric conversion element, the number of the minimum values is counted, and the accumulation time at the next photometry is based on the count value. Is calculated. Furthermore, when the maximum value of the photometric signal is the upper limit value of the photometric range of the photoelectric conversion element, the number of the maximum values is counted and the minimum value of the photometric signal can be measured. When the value is the lower limit value of the range, the number of the minimum values is counted, and the accumulation time at the next photometry is calculated based on these count values. Further, according to claim 6, when the maximum count value is larger than the minimum count value, the accumulation time at the next photometry is shorter than the previous accumulation time, while the maximum count value is the minimum. If the value is smaller than the count value, the accumulation time is calculated so that the accumulation time at the next photometry becomes longer than the previous accumulation time.

[0007]

In order to detect the accurate subject brightness with the minimum number of photometry, the photometric range of the device is set to the high brightness side or the low brightness side so that the output of the photoelectric conversion element does not include the upper limit value or the lower limit value as much as possible. It is necessary to shift appropriately. This shift of the measurable range can be adjusted by changing the storage time of the element. In the present invention, at least one of the maximum value and the minimum value of the plurality of photometric signals output from the photoelectric conversion element is used to determine the accumulation time at the next photometry, that is, the photometric range. This makes it possible to prevent the photometric signal from exceeding the upper limit value or the lower limit value of the photometric range as much as possible at the next photometry, that is, all the photometric signals fall within the photometric range of the element. Particularly, in claim 2, since the storage time is calculated so that the average value of the maximum value and the minimum value of the photometric signal is exactly the intermediate value of the photometric range of the photoelectric conversion element at the next photometry, When the difference from the minimum value is small, it is highly likely that all the photometric signals will fall within the photometric range of the element at the next photometry. Further, in claims 3 to 5, the number of signals of the upper limit value or the lower limit value of the photometric range of the plurality of photometric signals is counted, and the accumulation time at the next photometry is calculated based on the counted value. Even when the difference between the maximum value and the minimum value is large, it is highly likely that all the photometric signals will fall within the photometric range at the next photometry. In particular, when the maximum count value is larger than the minimum count value as in claim 6, the accumulation time at the next photometry is set to be shorter than the previous accumulation time (the photometry range is set to the high brightness side). On the other hand, if the maximum count value is less than the minimum count value, the accumulation time at the next photometry will be longer than the previous accumulation time (when the metering range is on the low brightness side). When the next photometry is performed, it is more likely that all the photometric signals will fall within the photometric range.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. << Explanation of Optical System >> In FIG. 1, reference numeral 1 denotes a taking lens, and the subject light passing through the taking lens 1 is observed by an eyepiece 5 through a quick return mirror 2, a diffusion screen 3 and a pentaprism 4. To be done. on the other hand,
A part of the subject light diffused by the diffusing screen 3 is guided to the photometric light receiving element 7 via the pentaprism 4 and the lens 6.

<< Explanation of Light-Receiving Element for Photometry and Control System >> The light-receiving element 7 is composed of a storage photoelectric conversion element such as a CCD sensor, and has a light-reception storage section 71, a transfer section 72, and
The voltage conversion unit 73 and the storage gate unit 74 are included. As shown in FIG. 2, the light receiving / accumulating unit 71 has 20 horizontal and 1 vertical arranged so that the object field corresponding to the entire photographing screen can be measured.
Two 240 segments in total are arranged in a matrix, and the charges generated in each segment are accumulated.

A timing circuit shown by reference numeral 8 creates a clock pulse necessary for transfer of electric charges by a master clock input from a clock generation circuit (not shown) and inputs the clock pulse to a transfer unit 72, and the transfer unit 72 receives the input. In accordance with the clock pulse, the charges accumulated in the light receiving / accumulating unit 71 are transferred to the voltage converting unit 73 pixel by pixel. The voltage conversion unit 73 converts the received charge signals of the 240 pixels into voltage level values, and outputs the voltage level values from the output terminal as A / A signals.
Output to the D conversion unit 9. The A / D conversion unit 9 converts the photometric signal (voltage signal) from the voltage conversion unit 73 into a numerical signal that can be recognized by the computer and outputs it. The accumulation gate unit 74 is a gate that receives a pulse signal from the accumulation control unit 14 included in the control circuit 100 and instructs the light reception accumulation unit 71 to start and end charge accumulation.

The control circuit 100 includes the control unit 14, the accumulation time setting unit 13, the brightness calculation unit 10, and the exposure calculation unit 1.
2 and the storage time setting unit 13 includes a brightness calculation unit 1
Based on 0 and the information from the exposure calculation unit 12, the optimum accumulation time for the next accumulation is calculated to adjust the accumulated charge amount. The details will be described later. Brightness calculation unit 10
Calculates the luminance value using the lens information from the in-lens ROM 11, the storage time input from the storage time setting unit 13, and the photometric signal from the A / D conversion unit 9. The exposure calculation unit 12 performs an exposure calculation based on the brightness value calculated by the brightness calculation unit 10 to calculate a proper exposure value, and also obtains an aperture value and a shutter speed value for the proper exposure. Then, when a release button (not shown) is pressed, the mirror 2 is flipped up, the diaphragm 10 and the shutter 11 are controlled to predetermined values, and exposure control is performed.

<< Description of Necessity of Setting Accumulation Time >> Next, the necessity of adjusting the accumulation time of the light receiving element 7 by the accumulation time setting unit 13 will be described. Generally, the photometric range required for the photometric device of a camera is EV0 to EV0.
EV20, that is, 20 EV in dynamic range
The current CCD has a dynamic range of about 10 EV at most. Therefore, it is necessary to adjust the storage time of the CCD and shift the required photometric range to an optimum level including the main subject.

Specifically, the brightness value in the object scene is EV0 to EV0.
EV20 has an illuminance of about 0.01 Lx to 10 on the light receiving element surface when a standard photographing lens is attached.
It is 000 Lx. The sensitivity of the light receiving element is about 20V / lx
S, and the saturated output is about 2V, so the storage time is 1
When it is 0 μS, the measurable range is about EV10 to EV2.
When the storage time is 10 mS, the measurable range is EV0 to EV10. That is, by adjusting the storage time of the light receiving element within the range of 10 μS to 10 mS, the dynamic range of EV0 to EV20, which is the photometric range required for the photometric device of the camera, can be realized for the first time.

In the case of using a CCD for photometry, the photometric range in one photometry is 10 for the above reason.
Although it is limited to the EV range, there is no problem because the dynamic range of the silver salt film is smaller than 10 EV.

<< Description of Main Algorithm >> FIG. 3 is a flowchart showing a main algorithm executed by the control unit of the control circuit 100. For example, when the release button is pressed halfway down, the program of FIG. 3 is started in the control unit 14, and first, in step # 101, the flag n is set to 1 which is the initial value. This flag n is for determining whether or not the photometric operation to be performed is the first photometric operation. When n = 1, the first photometric operation is performed, and when n = 0, the second and subsequent photometric operations are performed. It indicates that the photometry is.

When it is determined in step # 102 that n = 1, that is, the first photometry, n is determined in step # 103.
= 0, and then, in step # 104, the accumulation time t is set to t1, which is a predetermined value, and the accumulation operation of the light receiving element 7 is performed. Here, t1 = 10 μS, that is, the photometric range is EV10 to EV20. Step #
In 105, 240 photometric signals are read through the transfer section 72 and the voltage conversion section 73 by a predetermined charge read pulse generated from the timing circuit 95, and after being converted into numerical values by the A / D conversion section 9, they are not shown. Stored in memory. Here, the resolution of A / D conversion is 10 bits, that is, 0 to 1023.

In step # 106, the accumulation time t of the second photometry is set to t2 which is a predetermined value, and the accumulation is performed again. Here, t2 = 10 mS, that is, the measurable range is EV0 to EV10. Step # 107
Now, read out the photometric signal as in step # 105,
The data is stored in a memory different from the above. Step # 1
In 08, two photometric signals are combined. That is, the measurable range when the accumulation time t = t1 is EV10 to EV20, and the measurable range when the accumulation time t = t2 is EV0 to E.
Since it is V10, a photometric signal having a dynamic range of EV0 to EV20 is created based on these two photometric results. Specifically, t obtained in step # 105
240 luminance data at t = t1 are searched, and the photometric signal at t = t2 is used as the photometric result when t = t2 for a region that is less than or equal to the lower limit of photometry, that is, when EV10 or less. The photometric signal at time is used as the photometric result. In this case, the accumulation time is 1 between t1 and t2.
Since the difference is 000 times, either the data at t1 is multiplied by 1000 or the data at t2 is multiplied by 1/1000. Thereafter, the process proceeds to step # 119.

On the other hand, if n = 1 is not determined in step # 102, that is, it is determined that the photometry is the second or subsequent photometry, the process proceeds to step # 109 to set the variable k to "1". This k
Indicates the number of times of photometry in step # 110, and indicates that the first photometry is performed when k = 1 and the second photometry is performed when k = 0. In step # 110, the storage time t is read from the memory, and this storage time t
Then, the above accumulation operation is performed. Here, the accumulation time t is obtained in step # 120 described below based on the previous photometric signal.

Although not directly related to the gist of the present invention, the photometric operation (accumulation operation) of step # 110 is
Explain the reason for doing it once. For example, when photographing under a fluorescent lamp, the subject brightness is not always constant due to the influence of the flicker of the fluorescent lamp, and bright and dark are repeated in a constant cycle as shown in FIG. Therefore, the level of the photometric signal varies depending on the time when the above-mentioned accumulation operation is performed, and there is a possibility that a correct brightness value cannot be obtained by one accumulation operation. Therefore, in the present embodiment, the accumulation operation is performed twice at a predetermined time interval and the photometric signals for the two times are averaged, thereby eliminating the influence of flicker.

That is, if k = 1 is determined in step S111, the photometric signal is read out and stored in the memory in the same manner as step # 105, and if k ≠ 0, step # 113 is followed by step # 113. The photometric signal is read out in the same manner as 105, and the second photometric signal, the first photometric signal and the arithmetic mean value are obtained and stored again in a predetermined memory.

In step # 114, step # 112
Alternatively, it is determined whether or not the accumulation time t obtained in # 113 is smaller than the predetermined value Tf1. Tf1 is the time when the influence of flicker cannot be ignored in photometry. The effect of flicker cannot be ignored if the accumulation time is shorter than the flicker cycle, so that Tf1 = is set between the flicker cycle of 10 ms in the 50 Hz region and the flicker cycle of 8.3 mS in the 60 Hz region.
9.2 mS. If step # 114 is denied, the procedure proceeds to step # 119, and if affirmed, step # 115
Proceed to.

In step # 115, it is determined whether or not the accumulation time t is longer than a predetermined value Tf2. If the determination is negative, the process proceeds to step # 119, and if the determination is affirmative, the process proceeds to step # 116. The reason for making the determination in step # 115 is as follows. The brightness value under artificial lighting such as fluorescent light is at most E
V14, that is, the illuminance on the light receiving element is about 156 l
Since it is only at the x-th position, if the brightness value is brighter than that, it may be considered as illumination by natural light such as the sun. Therefore, if the accumulation time t is longer than the accumulation time when the brightness of about 156 lx is measured on the light receiving element, it can be considered that there is no influence of flicker. Therefore, Tf2 is the accumulation time 6 when 156 lx.
40 μS.

In step # 116, it is determined whether or not k = 1. If k ≠ 1, photometry has already been performed twice, so the process proceeds to step # 119. If k = 1, photometry is performed. Has been performed only once, the process proceeds to step # 117 to perform another photometry. K in step # 117
= 0, then in step # 118, a timer (not shown) is activated to wait until an odd multiple of 2 minutes of the flicker cycle has elapsed from the previous accumulation start time,
When the time comes, the process returns to step # 110 to start the accumulation again.

In step # 119, the brightness value calculation unit 10
Is operated, and the brightness value BV (m, n) corresponding to each photometric region is calculated based on the 240 photometric signals obtained in step # 112 or # 113. here,
(M, n) is an address that identifies each segment of the light receiving element shown in FIG. 2, m is an integer from 1 to 20 indicating the horizontal direction, and n is an integer from 1 to 12 indicating the vertical direction. . In step # 119A, the exposure calculation unit 12 is operated to obtain the proper exposure value BVans based on the calculated brightness values. The method of obtaining BVans will be described in detail later. In step # 120, the accumulation time setting unit 13 is operated to calculate the accumulation time t at the next photometry and store it in a predetermined memory. This accumulation time calculation method will also be described in detail later. If it is determined in step # 121 that the release button (not shown) is fully pressed, the process proceeds to step # 122, and the aperture and shutter are driven based on the obtained proper exposure value BVans to perform exposure control. If it is not fully pressed, the process returns to step # 102.

<< Explanation of Exposure Calculation >> Next, the above step #
An example of the exposure calculation processing in 119A will be described with reference to the flowchart of FIG. First, in step # 201, 240 brightness values B obtained corresponding to each photometric region are obtained.
Among V (m, n), data having a luminance value exceeding 16.3 EV is replaced with 16.3 EV. This is a measure for minimizing the influence of an object such as the sun that has an ultra-high brightness exceeding 16.3 EV because the object is strongly affected by it. .

In step # 202, it is determined whether or not all 240 pieces of photometric data have been replaced by 16.3 EV. If affirmative, BVans = 16.3 in step # 203, and if negative, in step # 204. , BVmax, BVmin, BVh, BVl, BVm, BVcw are obtained from the respective brightness values BV (m, n). The contents of these variables are as follows. BVmax: Of the 240 brightness values, the highest brightness BVmin: Of the 240 brightness values, the lowest brightness BVh: Of the 240 brightness values, 24 from the higher brightness side
Average brightness value of area BVl: 24 brightness values from the lower brightness side of 240 brightness values
Average brightness value of area BVm: Average value of all 240 brightness values BVcw: Of 240 brightness values BV (m, n), 8
Average brightness value of 36 areas (area indicated by A in FIG. 2) of ≦ m ≦ 13 and 4 ≦ n ≦ 9. Here, when calculating BVh and BVl, the average value of 24 areas was taken. It is not limited to 24 areas,
It can be more or less than this. Also, BVcw
Similarly, the output is not limited to the average value of the 36 areas, and may be any output as long as it is near the center of the object scene.

Next, at step # 205, BVmax-
It is determined whether or not BVmin <2, and if the result is affirmative, it can be considered that the scene is extremely flat because the difference between the maximum luminance value and the minimum luminance value is small. Therefore, in this case, the photometric value of any area is hardly changed, and therefore, in step # 206, the average brightness value of the 36 highly reliable central areas is substituted as the appropriate exposure value. That is, BVans = BVcw.

When step # 205 is denied, the routine proceeds to step # 207, where it is determined whether BVh-BVl <2.
If the result is affirmative, it can be considered that the difference between the high-luminance region and the low-luminance region is small and the scene is almost flat. Therefore, in step # 208, the proper exposure value BVans is calculated by BVans = (BVh + BVl + BVcw) / 3.

When step # 207 is denied, the routine proceeds to step # 209, where it is determined whether or not BVm-BVcw> 2. If affirmative, the central brightness value is smaller than the average brightness value, that is, the central part is dark, so it is considered to be backlight, and the appropriate exposure value BVans is determined by BVans = (BVl + BVcw) / 2 in step # 210. .

When step # 209 is denied, the routine proceeds to step # 211, where it is determined whether BVcw-BVm> 2. If the result is affirmative, it is considered that the scene is in the spotlight because the brightness value of the central part is larger than the average brightness value, that is, the central part is bright, and in step # 212, BVans = BVcw. To do.

When step # 211 is denied, the routine proceeds to step # 213, where it is determined whether or not BVh-BVm <0.5. If affirmative, it is considered that the scene has a small difference between the high brightness area and the average brightness value and a small dark subject exists in the screen, and in step # 214, it is appropriate by BVans = (2 · BVm + BVl) / 3. Determine the exposure value BVans.

When step # 213 is denied, the routine proceeds to step # 215, where it is determined whether BVm-BVl <0.5. If the result is affirmative, the scene is considered to have a small difference between the low-brightness area and the average brightness value and a small bright subject in the screen, and in step # 216, BVans = (2 · BVm + BVh) / 3 Determine the exposure value BVans.

If step # 215 is denied, what is not applicable to any of the above scenes is regarded as a so-called general scene, and in step # 217, proper exposure is performed by BVans = (BVm + BVcw) / 2. Find the value BVans.

<< Description of Calculation Method of Optimal Storage Time >> FIG.
3 is a flowchart showing details of the accumulation time calculation in step # 120 of FIG. First step # 3
In 01, it is determined whether BVmax-BVmin <10.
If affirmative, it is considered that all 240 photometric signals are within the photometric dynamic range of one time, and in step # 304, the next photometric reference level BVt is set to the maximum value and the minimum value of the brightness value (photometric signal). The average value is calculated by BVt = (BVmax + BVmin) / 2. Here, the photometric reference level BVt indicates a luminance value that gives a photometric signal that is exactly half the saturation level of the photometric signal when photometry is performed for a certain storage time. For example, when the photometric range is EV10 to EV20. , BVt = 15. That is, by substituting BVt into the equation used in step # 311, which will be described later, the storage time for obtaining a photometric range in which the value of BVt becomes half the saturation level is calculated.

If step # 301 is denied,
In the previous photometry, it means that there was data above the photometry upper limit value or below or below the photometry lower limit value, so in step # 303 the high brightness photometry limit data in the previous photometry,
That is, the maximum number Nmax is counted. Step #
In step 304, as in step # 303, the low-brightness photometry limit data in the previous photometry, that is, the minimum number N
Count min. In step # 305, the photometric reference level BVt in the previous photometry is calculated according to BVt = log (0.32 / t) / log2. Here, t is the accumulation time in the previous photometry. For example, when t = 0.01 seconds, BVt =
It becomes 5.

Next, at step # 306, the next photometric reference level BVt is obtained by using the previous photometric reference level as follows: BVt = BVt + (Nmax-Nmin) / 10. This formula works for increasing the high-brightness photometry limit data when Nmax is larger than Nmin, so it works to raise the next photometry reference level. Conversely, when Nmin is larger than Nmax, the low-brightness photometry limit data is Since there are many, it will work to lower the photometric reference level for the next time. Here, increasing the photometric reference level means shifting the photometric possible range to the high brightness side, and lowering the photometric reference level means shifting the photometric possible range to the high brightness side. The level shift amount is optimized by setting Nmax-Nmin to 1/10.
Not limited to / 10, optimized values may be used.

In step # 307, it is determined whether or not BVt> 15, and if the result is affirmative, the photometric reference level has exceeded the upper limit of photometry. Therefore, in step # 308, the next photometric reference level BVt is measured. The upper limit value is set to 15.
At this time, the photometric range is EV10 to EV20.
When step # 307 is denied, the routine proceeds to step # 309, where it is determined whether or not BVt <5. If the result at step # 311 is affirmative, the photometric reference level has exceeded the photometric lower limit, and therefore the next photometric reference level BVt is set at 5 as the photometric lower limit at step # 310. At this time, the photometric range is EV0 to EV10. Also, step #
If 309 is denied, the process proceeds to step # 311.

In step # 311, the above step # 3 is executed.
02, # 306, # 308, or # 310, the next storage time t is calculated from t = 0.32 / (2 ^ BVt), and this t is stored in a predetermined address of the memory. To do.
Here, the ^ mark represents exponentiation. The storage time t is a storage time for obtaining a photometric range in which the value of BVt becomes half the saturation level as described above, and the larger the BVt, the shorter the storage time t.

According to the procedure of FIG. 5 described above, when the difference between the maximum value and the minimum value of the brightness value (photometric signal) corresponding to each photometric output is less than the dynamic range 10 of the photoelectric conversion element,
That is, when all the photometric signals are within the photometric dynamic range of one time, the accumulation time t is calculated so that the average value of the maximum value and the minimum value becomes the intermediate value of the measurable range at the next photometry. To be done. If photometry is performed at this accumulation time t, it is unlikely that the obtained photometric signal exceeds the upper limit value and the lower limit value of the above-mentioned photometric range, and it is highly possible that the optimum exposure value can be calculated with one photometry. , It will be possible to quickly shoot the next shooting.

When the difference between the maximum value and the minimum value is 10 or more in the dynamic range of the photoelectric conversion element, that is, in the previous photometry, the brightness value above the upper limit value of the photometric range or below the lower limit value If it always exists, the accumulation time t is obtained according to the number of maximum values and minimum values. Specifically, if the number of maximum values is greater than the number of minimum values, the accumulation time at the next photometry should be shorter than the previous accumulation time (so that the measurable range is shifted to the high brightness side). On the other hand, if the number of maximum values is less than the number of minimum values, the accumulation time at the next photometry should be longer than the accumulation time at the previous photometry (the measurable range should be shifted to the low brightness side. 2) The accumulation time t is calculated. Therefore, if photometry is performed at this accumulation time t, it is unlikely that the photometric signal obtained in the same manner as above will exceed the upper limit value and the lower limit value of the above-mentioned photometric range, and the optimum exposure value will be calculated with one photometry. It is more likely to be possible.

In the configuration of the above embodiment, the light receiving element 7
Denotes a photometric unit, the accumulation time setting unit 13 constitutes an accumulation time calculation unit, and the control unit 14 constitutes a control unit.

The above-mentioned BVt represents 1/2 of the photometric range of the apex system. In the Apex method, the base 2 logarithm is used, so
It is different from 1/2 of the photometric range that is called a true number. To explain this in an easy-to-understand manner with reference to FIG. 7, since the saturation voltage of the photoelectric conversion optical element is 2V, 1/2 of the measurable range level in the apex method is 0.0625V, but it is 1 in the true number. / 2 is 1V. In the case of the present embodiment, since the apex method is used, the brightness of BVt is 0.0625V.
However, this may be set to 1V.

In the present embodiment, the high brightness photometric limit number N
Although both max and the low-luminance photometric limit number Nmin are counted, only one of them may be counted. In this case, in the equation BVt = BVt + (Nmax-Nmin) / 10 described in step # 306, 0 may be substituted for the variable that does not count among Nmax and Nmin. Also, in this equation, (Nmax-
When Nmin) is other than 0, the BVt of the next time is always changed, but if (Nmax-Nmin) is within a certain numerical range for stabilization of control, BVt will be changed.
The Vt may not be changed.

Further, focusing on the photometric value and its frequency distribution, as shown in FIG. 8A, Nmax is not 0 and B
When Vmin is relatively located on the high-luminance side of the measurable range, BVt may be calculated by BVt = BVmin + 5 so that BVmin is near the lower limit of the measurable range. As a result, at the next photometry, for example, the frequency distribution as shown in FIG. 9A is obtained. Similarly, as shown in FIG. 8B, when Nmin is not 0 and BVmax is relatively located on the low luminance side of the photometric range, BVmax is near the upper limit of the photometric range. In addition, BVt may be obtained by BVt = BVmax-5. As a result, at the next photometry, for example, a frequency distribution as shown in FIG. 9B is obtained. Here, 5 which is a constant term on the right side of the above equation is BVmin or BVmax because the measurable range is 10 EV.
It is for taking the lower limit or the upper limit of the photometric range.

The method of dividing the light receiving element is not limited to the embodiment. The exposure calculation method shown in FIG. 4 is not limited to this.

[0046]

According to the present invention, the accumulation time at the next photometry is obtained by using at least one of the maximum value and the minimum value of the plurality of photometric signals output from the photoelectric conversion element. The photometric range of the element can be shifted to the optimum range, so that the possibility that all the photometric signals will fall within the photometric range at the next photometry at the next photometry becomes high. Therefore, an accurate exposure value can be calculated with a small number of photometry operations, and the time from the shooting start operation to the shooting can be shortened. In particular, in claim 2, since the storage time is calculated so that the average value of the maximum value and the minimum value of the photometric signal becomes exactly the intermediate value of the photometric range of the photoelectric conversion element at the next photometry, When the difference between the value and the minimum value is small, there is a high possibility that all the photometric signals will fall within the photometric range at the next photometry. According to the invention of claims 3 to 5, the number of signals of the upper limit value or the lower limit value of the photometric range of the plurality of photometric signals is counted, and the accumulation time at the next photometry is calculated based on the count value. Since the calculation is performed, even if the difference between the maximum value and the minimum value is large, there is a high possibility that all the photometric signals will fall within the photometric range during the next photometry. In particular, according to the invention of claim 6, when the count value of the maximum value is larger than the count value of the minimum value, the accumulation time at the next photometry is shorter than the accumulation time of the previous time. If the number of counts is less than the minimum count, the accumulation time at the next photometry is set to be longer than the previous accumulation time, so all photometry signals may fall within the measurable range at the next photometry. Will be even higher.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a photometric control device according to the present invention.

FIG. 2 is a diagram showing an example of division of a light receiving element.

FIG. 3 is a flowchart showing a main algorithm.

FIG. 4 is a flowchart showing an exposure calculation subroutine.

FIG. 5 is a flowchart showing a storage time calculation subroutine.

FIG. 6 is a diagram illustrating the principle of flicker removal.

FIG. 7 is a diagram showing a relationship between a photometric output voltage and an EV value.

FIG. 8 is a diagram showing a frequency distribution of a photometric signal.

FIG. 9 is a view similar to FIG.

FIG. 10 is a diagram showing a photometric output by a conventional storage time setting method.

[Explanation of symbols]

 1 Photographic Lens 2 Quick Return Mirror 3 Diffusion Screen 4 Penta Prism 5 Eyepiece 6 Photometric Lens 7 Photodetector 8 Timing Circuit 9 A / D Converter 10 Luminance Calculator 11 Lens ROM 12 Exposure Calculator 13 Accumulation Time Setting 14 Control unit 71 Light receiving element 72 Transfer unit 73 Voltage conversion unit 74 Storage gate 100 Control circuit

Claims (6)

[Claims] 1. A photometric device that divides an object field into a plurality of photometric regions by a plurality of storage-type photoelectric conversion elements to perform photometry, and outputs a photometric signal relating to the brightness of each photometric region. In the photometric control device of the camera, which is configured to obtain the exposure value based on a plurality of photometric signals, using at least one of the maximum value and the minimum value of the plurality of photometric signals, at the time of the next photometry of the photoelectric conversion element. A photometric control device for a camera, comprising: a storage time calculating means for calculating a storage time; and a control means for operating the photoelectric conversion element at the storage time calculated by the storage time calculating means. 2. The storage time calculating means sets the storage time so that the average value of the maximum value and the minimum value of the photometric signal becomes an intermediate value of the photometric range of the photoelectric conversion element at the next photometry. The photometric control device for a camera according to claim 1, wherein the photometric control device calculates. 3. The storage time calculation means, when the maximum value of the photometric signal is the upper limit value of the photometric range of the photoelectric conversion element, counts the maximum value and sets the count value to the maximum value. 2. The photometric control device for a camera according to claim 1, wherein the accumulation time for the next photometry is calculated based on the photometric control. 4. When the minimum value of the photometric signal is the lower limit value of the photometric range of the photoelectric conversion element, the storage time calculation means counts the minimum value, and the counted value is counted. 2. The photometric control device for a camera according to claim 1, wherein the accumulation time for the next photometry is calculated based on the photometric control. 5. When the maximum value of the photometric signal is the upper limit value of the photometric range of the photoelectric conversion element, the storage time calculating means counts the maximum value and the photometric signal. When the minimum value of is the lower limit value of the photometric range, the number of the minimum values is counted, and the accumulation time at the next photometry is calculated based on these both count values. Item 1. A photometric control device for a camera according to item 1. 6. The accumulation time calculation means, when the maximum count value is greater than the minimum count value, so that the accumulation time at the next photometry is shorter than the previous accumulation time. 6. When the maximum count value is smaller than the minimum count value, the accumulation time is calculated so that the accumulation time at the next photometry is longer than the previous accumulation time. Photometric control device for the camera described.