JP2550062B2 - Exposure control device - Google Patents

Description

The present invention relates to an exposure control device that is effective when applied to an electronic still camera or the like.

[Conventional technology]

Conventionally, as an exposure control device applied to an electronic still camera or the like, a device configured to change the gain of photoelectric conversion output according to the output level of photoelectric conversion means in order to widen the dynamic range of photometry (Japanese Patent Application Laid-Open No. 2000-121242) JP-A-60-43979) has been proposed. In order to change the gain, a plurality of amplifying means corresponding to the number of gain stages to be changed are arranged in parallel, and one of these amplifying means is selectively used according to the level of photoelectric conversion output. It is usually configured as follows.

[Problems to be solved by the invention]

In the conventional exposure control device of this kind as described above, as the dynamic range of photometry is expanded, many amplifying means having different gains must be provided, resulting in a complicated structure and an increase in the number of parts. Therefore, a large mounting space is required, which is an obstacle to downsizing of the device.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an exposure control device of this type that can accurately cover an extremely wide dynamic range with a relatively small circuit configuration. Is.

[Means and Actions for Solving Problems]

In order to solve the above-mentioned problems, one invention of the present application is: photoelectric conversion means for obtaining a photoelectric conversion output exhibiting a rate of change in accordance with the amount of incident light; An integrating means for obtaining an output corresponding to an integrated photoelectric conversion output, an integral target value setting means for variably setting an integral target value in the integrating means, and an output of the integrating means for the duration of the exposure. Means for resetting the integration means each time the integration target value is reached, counting means for counting the number of times the output of the integration means reaches the integration target value, and variably setting the counting target value in the counting means Counting target value setting means, and is configured to perform exposure control based on the integration target value, the counting target value, and the counting result of the counting means. It is that the exposure control device according to.

Another invention of the present application is: photoelectric conversion means for obtaining a photoelectric conversion output exhibiting a rate of change according to the amount of incident light, and integration of the photoelectric conversion output as the exposure time progresses from the time corresponding to the start of the exposure. , An integration target value setting means for variably setting the integration target value in the integration means, and an output of the integration means each time the output of the integration means reaches the integration target value while continuing the exposure. And a counting means for counting the number of times the output of the integrating means reaches the integration target value, and exposure control is performed based on the integration target value and the counting result in the counting means. It is an exposure control device characterized by being configured to perform.

Still another invention of the present application is: photoelectric conversion means for obtaining a photoelectric conversion output exhibiting a change rate according to the amount of incident light, and integrating the photoelectric conversion output with the progress of exposure time from the time corresponding to the start of the exposure. An integrating means for obtaining an output corresponding to the object, a means for resetting the integrating means each time the output of the integrating means reaches a predetermined integration target value during the continuation of the exposure, and an output of the integrating means for the integration target. The counting means for counting the number of times the value has been reached, and the counting target value setting means for variably setting the counting target value in the counting means, are exposed based on the counting target value and the counting result in the counting means. An exposure control device characterized by being configured to perform control.

According to each of the above inventions, the integration target value and / or the counting target value is variably set according to the amount of incident light, so that exposure control covering a wide dynamic range can be performed by a relatively small-scale counting means. .

〔Example〕

FIG. 2 is a block diagram showing a system of an electronic still camera including an exposure control device as an embodiment of the present invention.

Photometric IC100 including photoelectric conversion element, gate array
200, a photometric microcomputer 300, and a system control microcomputer 400 are connected by a bus and other signal lines so as to exchange signals with each other. Further, the gate array 200 is connected with an in-lens circuit 500 for controlling the diaphragm and the shutter. The gate array 200 includes a photometric block 210 that performs a predetermined signal processing operation based on the exchange of signals with the photometric IC 100 and the photometric microcomputer 300, and this photometric block 210.
Also, a circuit is formed including each block (circuit) of the exposure control block 220 that transmits / receives a control signal to / from the in-lens circuit 500 based on transmission / reception of a signal with the microcomputer for photometry 300. In the present system, the lens has a diaphragm, a shutter, and driving means for these, but the in-lens circuit 500 may also be configured to include a microcomputer. The photometric microcomputer 300 is connected with a switch circuit 310 for externally performing exposure compensation and other function settings by the operation of the operator. Similarly, the system control microcomputer 400
A switch circuit 410 for selecting a shooting mode such as aperture priority and shutter priority and triggering shooting is connected to the.

The outline of the operation of the electronic still camera system having the above configuration is as follows.

The case where the present system performs pre-photometry operation in response to a command from the system control microcomputer 400 will be described. First, the photometric IC 100 obtains a photoelectric conversion output corresponding to the amount of incident light. In this system, this is performed in a so-called open metering state in which the diaphragm is fully opened.
The counter corresponding to this photoelectric conversion output is performed in the counter in the photometry block 210 in the gate array 200, and the photometric microcomputer 300 calculates the value of the incident light amount based on the count value of the counter. Further, the shutter speed, aperture value, etc. corresponding to the photometric value are also calculated in the photometric microcomputer 300. These values are transferred to the system control microcomputer 400. Microcomputer 400 for system control
Generates a signal for performing a predetermined display operation relating to the shutter speed, aperture value, etc. corresponding to the amount of incident light at that time based on the transferred data. As will be described later in detail, in the system of the present example, in the photometric microcomputer 300, the count value in the counter of the gate array 200 is monitored, and the count value is repeatedly changed and reset if necessary so that the counter does not overflow. It is done like this. For this reason, even in the dynamic range of extremely wide area photometry that is necessary for open metering,
A relatively small number of counting means can be used.

Next, the exposure control operation will be described. Switch circuit 410
When the trigger button, which is a circuit element, is pressed, the system microcomputer 400 gives the photometric microcomputer 300 a command to switch the system operation from the pre-photometric operation described above to the exposure control operation. The exposure control operation of this system is performed by the so-called direct photometry method based on the photoelectric conversion output from the same photometric IC 100 as in the above-described pre-photometry. When the exposure control operation starts, a photoelectric conversion signal accumulation operation is started in the photometric IC 100, and at the same time, a command is issued to the image sensor to perform signal integration operation. The level of the integrated value of the photoelectric conversion signal in the photometric IC 100 (more precisely, the voltage of the capacitor corresponding to the time integrated value of the current corresponding to the photoelectric conversion) is measured by the microcomputer 300 for photometry at that time with respect to the IC 100. Each time it reaches the set level (that is, the integration target value),
The IC 100 gives an integration end pulse to the photometry block 210 of the gate array 200. The photometry block 210 performs integrated counting of this integration end pulse, and immediately after the calculation of each pulse,
Reset IC100. When the integrated count value in the photometric block 210 reaches a value (preset value) set from the system microcomputer 400 via the photometric microcomputer 300, the photometric block 210 transfers to the in-lens circuit 500 via the exposure control block 220. Give a control signal. On the basis of this control signal, the in-lens circuit regulates the exposure time, that is, performs operations such as closing the shutter and / or stopping the signal accumulation operation of the image sensor to end the exposure. In the above, the photometric microcomputer 30
The integrated value level (that is, the integration target value) set for the photometric IC 100 from 0, and the microcomputer
The integrated count value (that is, the target count value) set from 300 to the photometry block 210 of the gate array 200 can be changed to take an appropriate value as required, such as exposure correction, as described later in detail.

The above is the outline of the system of the electronic still camera to which the present invention is applied. The more detailed configuration, operation, and effect of the present invention will be described in detail below.

FIG. 1 is a block diagram showing in detail the main parts of the system of FIG. In FIG. 1, parts corresponding to those in FIG. 2 are designated by the same reference numerals. As shown,
In the photometric IC 100, the output of an operational amplifier 102 in which a photodiode 101 arranged at a position that responds to incident light is connected between both ends of an input is connected to one input end of a comparator 103, and the other end of the comparator 103 is connected. The reference level signal Eγ is applied to the input terminal of the. Also, the photodiode
Integrating capacitor 104 between the cathode of 101 and ground
Is connected. The midpoint between the integration capacitor 104 and the photodiode 101 is connected to the positive electrode side of the electromotive force means (battery) 106 that generates the reference voltage Ei via the drain / source of the FET 105 for switching, and the negative electrode side of the battery 106. Is grounded. As described above with reference to FIG. 2, the gate array 200 includes the side light block 210 and the exposure control block 220. This metering block 210 is a metering IC1
FET in response to the integration end pulse IE which is the output of the comparator 103 of 00
A charge / discharge control circuit 211 that gives a pulsed reset signal RT to the gate of 105, a clock signal CL from an oscillation circuit 600 that generates a clock signal that is common to the photometric microcomputer 300, and receives from the photometric microcomputer 300 Frequency divider 212 that divides the same clock pulse at a division ratio according to a division instruction, counting pulse that is an output signal of frequency divider 212 in response to photometry / exposure control switching signal MC from microcomputer 300 Switching circuit 213 for selectively outputting both or one of CP and integration end pulse IE of comparator 103 of photometric IC 100, 8-bit counter 214 for counting output pulse SC of switching circuit 213, 8-bit counter 214 215 that latches the output of
It is configured to include each. 8-bit counter 21
A function of receiving the integration end pulse IE through the switching circuit 213 and giving it to the exposure control block 220 and the photometry microcomputer 300 as a photometry end signal ED is added to the unit 4. Further, as will be described later, the photometry end signal ED is output even when the preset value to the 8-bit counter 214 is subtracted and counted and the count number becomes 0. To the charge / discharge control circuit 211 and the exposure control block 220, a photometry start command MS from the photometry microcomputer 300 is given. The reference level signal Eγ given to the comparator 103 of the photometric IC 100 is the photometric microcomputer 30.
It is output from the D / A converter 301 attached to 0.

The operation of the system to which the present invention having the above configuration is applied will be described in detail below.

A diaphragm arranged in a lens (lens barrel) (not shown) is controlled by an in-lens circuit 500 and maintains an open state during a photometric operation according to a command from the photometric microcomputer 300. Start command M from the microcomputer 300
When S is given to the charge / discharge control circuit 211, the charge / discharge control circuit 211 gives a reset signal RT to the gate of the FET 105 of the photometric IC 100. The FET conducts during the high level period of the reset signal RT with a relatively small duty, and the integration capacitor
The current from the electromotive force means 106 charges 104, that is, integrates it to the reference voltage Ei. Immediately after the reset signal RT changes to the low level, the switch by the FET 105 is cut off, and the charge accumulated in the integrating capacitor 104 is stored in the photodiode 101.
The light is discharged through the photodiode 101 with a current value corresponding to the amount of incident light. The voltage on the positive electrode side of the integrating capacitor 104, which was E _i at the beginning of charging, drops at a rate of change corresponding to the charging flow at this time. Along with this, the output voltage of the operational amplifier 102 also drops, and this voltage is set to the reference level signal E set for the comparator 103.
When it becomes equal to the level of γ, the comparator 103 outputs the integration end pulse IE.

FIG. 3 is a diagram showing the timing of each signal described above. FIG. 3 (a) is the reset signal RT described above, FIG. 3 (b) is the positive terminal voltage of the integrating capacitor 104, and FIG. The integration end pulse IE is shown. As shown in the figure, the charging / discharging of the integrating capacitor 104 is repeated in synchronization with the reset signal RT from the charging / discharging control circuit 211.
Is formed and emitted at every arrival of the integration end pulse IE. As described above, the change in the positive electrode voltage of the integrating capacitor 104 as shown in FIG. 3 (b) is due to the electric charge of the same capacitor being discharged through the photodiode 101. Current value, that is, the current value is proportional to the amount of light incident on the photodiode 101 having a proportional relationship. The time integrated value of the discharge current is equal to the discharge charge amount in the integrating capacitor 101 within the same section.

That is, when the capacity of the integrating capacitor 104 is C, and the voltage of the integrating capacitor 104 decreases from the voltage Ei of the electromotive force means 106 to the reference level Eγ, its discharge current is t, which is the time until the i _SC voltage changes from Ei to Eγ. From the above formula (1) Although the discharge current i _SC in the above equation (2) corresponds to the incident light amount, that is, the capacitance C of the integrating capacitor 101 is constant, so that the incident light amount can be determined by measuring the time t. You can When the amount of incident light fluctuates, the values of t in each discharge t ₀ , t ₁ , t ₂ ...
Will be different. Even if the amount of incident light is constant, E
If the value of γ is changed, the value of t will change.
In this system, the 8-bit counter 214 includes an oscillator circuit 6
It is configured to count counting pulses CP (thus an output pulse SC of the switching circuit 213) of a predetermined frequency supplied from 00 through the frequency divider 212 and the switching circuit 213, and obtain the time t by the counted value. There is.

In the above, the 8-bit counter 214 uses the photometry / exposure control switching signal MC from the photometry microcomputer 300.
The switching circuit 213 that responds to the above enables selective counting of the counting pulse CP from the frequency divider 212 or the integration end pulse IE from the comparator 103. When the system operates in the pre-metering mode in response to a command from the system control microcomputer 400, the signal MC causes
The switching circuit 213 supplies the counting pulse CP to the 8-bit counter 214 for counting.

FIG. 4 is a flowchart showing the operation of the device of the present invention. The operation of the system shown in FIGS. 1 and 2 will be described below with reference to this flowchart. When the photometric operation starts, the photometric microcomputer 300 gives the reference level signal Eγ to the comparator 103 via the D / A converter 301. Further, by issuing a frequency division command DV to the frequency divider 212 and setting a predetermined frequency division ratio, the frequency F of the counting pulse CP which is the output of the frequency divider 212 is initialized. A photometric start command MS is issued from the photometric microcomputer 300, and based on this, the charge / discharge control circuit 211 resets the integrating capacitor 104 by a reset signal RT (that is, charges to the voltage Ei).
To do. At the same time, the microcomputer 300 resets the 8-bit counter 214 by the counter clear command CC.
Immediately after this reset, the voltage of the integrating capacitor 104 begins to drop at a rate of change corresponding to the amount of light incident on the photodiode 101 due to discharge. During the time period in which the voltage of the integrating capacitor 104 continues to drop, the 8-bit counter 214 simultaneously continues counting the counting pulse SC supplied as the output SC of the switching circuit 213. The voltage of the integrating capacitor 104 drops, and the output of the operational amplifier 102 becomes the reference level signal Eγ.
When the level of reaches the level of
Is emitted. Based on this integration end pulse IE, the charging / discharging control circuit 211 again issues the reset signal RT, whereby the charging / discharging operation of the integrating capacitor 104 is repeated as described above. The integration end pulse IE is also supplied to the microcomputer for photometry 300 as a photometry end signal ED via the switching circuit 213 and the 8-bit counter 214 (a circuit additionally provided in addition to the 8-bit counter section) in the above order. When the microcomputer 300 receives the photometry end signal ED, the microcomputer 8
The count number D of the bit counter 214 is read via the latch 215. In the above operation, when the amount of light incident on the photodiode 101 is large, the integrating capacitor 104 is also quickly discharged, and the voltage of the capacitor 104 reaches the reference level Eγ in a relatively short time, but the amount of incident light is small. In this case, it takes a relatively long time for the voltage of the integrating capacitor 104 to reach Eγ. Therefore, if the amount of incident light is extremely small, the discharge time is extended and the 8-bit counter 211 that counts this time may overflow. Especially in this system, so-called open metering is performed in the pre-metering mode, so that the required dynamic range of metering is extremely wide, about 100 dB. In order to secure the identification accuracy of about ± 10% in this wide dynamic range, a counter of about 20 digits is usually required. However, in this system, the value of the count number D is monitored by the photometric microcomputer 300, and the reference level Eγ and the frequency F of the count pulse CP are adjusted so that the value of D is within a predetermined range.
I am trying to change. As a result, it is possible to cover a wide dynamic range, which cannot be covered unless a counter of about 20 bits is normally used, with a counter of only 8 bits with sufficient accuracy. That is, the photometric microcomputer 300 discriminates whether or not the count number D of the 8-bit counter 214 read as described above is within the range of 11 to 255 in decimal, and the value of D is within the range. , The level of the reference signal Eγ given to the comparator 103 via the D / A converter 301 and / or the frequency of the counting pulse CP by the frequency divider 212 controlled by the frequency division command DV. Change F and reset. If the count D does not fall within the above range even by this resetting, the level of the reference signal Eγ and / or the frequency F of the counting pulse CP is further changed and reset again.
8 as described above due to charging and discharging of the integration capacitor 104
The counting operation of the bit counter 214 is configured to be repeated about 10 times per second. If it is discriminated that the count number D is within the above range, the photometric microcomputer 30
0 calculates the incident light quantity based on the count number D, the reference level Eγ, and the frequency F of the counting pulse CP at this time.

In this system, an extremely efficient calculation means is used also for the calculation of the incident light amount. That is, the photometric microcomputer 300 stores each count number D in its own ROM.
Count code D'corresponding to each (count range)
Is provided for encoding, and based on this table, the count number D is directly relative to a certain count number D based on D = a (a is a certain integer value). Convert it to a code that represents the logarithmic value of the value (relative Ev value described later). That is, with respect to the coding of each count number, a separate calculation for coding is not required.

FIG. 5 is a diagram showing the contents of the table set in the ROM as described above. As shown in the figure, the count code D'corresponding to the count number D does not necessarily correspond one-to-one, and each count code D'corresponds to each value in the range of the count number D. There is.
Each count code d ₁ , d ₂ , d ₃ ......, d _m , ...... d _n-1 , d _n is 1 each
One of the relative Ev values _{e 1, e 2, e 3} , ......, 0, corresponds to _{...... e n-1, e n} . Here, the relative Ev value is a logarithmic value whose base is the count number D = a and whose base is 2 of the ratio Dm / a of the median value (median) Dm of each count number region. By converting the count number D into such a logarithmic value, the exposure amount can be easily calculated by the well-known APEX system. Relative Ev value takes a value including fractions below the decimal point, but in this system, each relative Ev value
The calculation is further simplified by making the Ev value correspond to the count code D ′ which is an integer value. In the table of FIG. 5, when the count number D (median value Dm) is a, the relative Ev value is used as a reference.
The relative Ev value corresponding to Dm = a is 0, and the count code dm is associated with this. Count number 238
When it is above 255 and below (median Dm = 252), the relative Ev value is Ev
= Log ₂ (252 / a) = e ₁ (e ₁ is a certain number that can specifically include a decimal number), and the corresponding count code is d ₁ (d ₁ is a certain integer). The photometric microcomputer 300 obtains the count code D ′ on the basis of the above table and executes the exposure amount calculation. This arithmetic expression is as follows.

A + k (Eγ + F) + D '(3) where A: open aperture (F value) k: proportional constant Eγ: reference level of comparator 103 F: frequency of counting pulse CP Represented.

The photometric microcomputer 300 calculates the amount of incident light by the calculation of the equation (3), and based on this value, the aperture value (aperture priority mode) or the shutter speed (shutter priority mode) set from the outside at this time. The display data is transferred to the system control microcomputer 400 in order to display the corresponding optimum shutter speed or aperture value. The system control microcomputer 400 performs a display operation based on this data. Further, when the system is in the aperture priority mode or the shutter priority mode, the photometric microcomputer 300 gives the exposure control command EC to the exposure control block 220 to operate at the optimum shutter speed or aperture value at the time of shooting. , Circuit in lens 500
To perform the required operation. Even when the system is in the program mode, the aperture value and shutter speed corresponding to the incident light amount are set in the microcomputer 300 for photometry.
The exposure control command EC corresponding to these data is issued based on the program set in the OM, and the in-lens circuit 500 is operated as described above. Regarding transmission and reception of commands and data between the exposure control block 220 and the in-lens circuit 500, a small number (or a single value) can be obtained by inserting an appropriate data parallel / serial conversion means and data value / parallel conversion means. The conductor) enables the transmission of a large number of commands and data.

FIG. 6 shows the reference level Eγ depending on various incident light amounts.
3 is a diagram showing a region of incident light amount corresponding to these set values when setting the frequency F of the counting pulse CP. For example in the area of the incident light amount is largest (I), the reference level Eγ to a _1, the frequency F of the count pulse CP is set to b _1. Similarly, in the region (III) where the amount of incident light is the third place, Eγ is set to a ₃ and F is set to b ₃ . In this example, b ₃ is b ₁
Set lower than.

The operation of this system in the exposure control mode will be described below. As described above, the exposure control in this system is based on the so-called direct photometry method.

When the system control microcomputer 400 switches the system to the exposure control mode by detecting the pressing of the trigger button, the photometric microcomputer 30
In response to this, 0 switches the switching circuit 213 by the photometry / exposure control switching signal MC. That is, the integration end pulse IE from the comparative example 103 is supplied to the 8-bit counter 214 as a counted pulse. Further, the 8-bit counter 214 is preset as preset data PS by the photometric microcomputer 300 as preset data PS and / or a reference level signal Eγ is set according to whether the exposure control operation is performed in a normal state or how many steps of exposure correction are performed. Set the level of. The preset data PS preset in the 8-bit counter 214 is the counting target value in this embodiment, and the level of the reference level signal Er is the integration target value in this embodiment. When the exposure operation starts, the positive electrode voltage of the integrating capacitor 104 decreases from the initial value Ei with a change rate according to the exposure intensity to the image pickup element at this time, that is, the incident light amount to the photodiode 101 exposed under the same condition. As a result, the output level of the operational amplifier 102 is changed to the comparator 103.
When the reference level Eγ in (1) is reached, the integration end pulse IE is emitted from the comparator 103, as in the case of the pre-photometry described above. However, in this case, since the system is in the exposure control mode as described above, the integration end pulse IE passes through the switching circuit 213 and the 8-bit counter 2
14 is provided to perform a subtraction count. The charging / discharging operation itself of the integrating capacitor 104 can be repeated exactly as in the above-described pre-photometry. Each time the integration end pulse IE arrives, the 8-bit counter 214 causes the above-mentioned preset value (PS)
When the value of the 8-bit counter 214 becomes 0, the counter 214 issues a photometry end signal ED. The exposure control block 220 uses this metering end signal ED
When receiving the signal, it issues a command to the lens internal circuit 500 to end the exposure. In response to this command, the in-lens circuit 500 performs a required operation such as closing the shutter to end the exposure.
Therefore, in this system, if the time required for discharging the integration capacitor 104 m times, that is, the time until the integration end pulse is emitted m times is set to correspond to the normal exposure time, the 8-bit counter 214 is used. Appropriate exposure control is performed by setting the preset value PS at m to m. In addition, the preset value PS is set to 2m, 2 ^{2 ・} m,…
..., 2 ²ⁿ · m, the exposure compensation of over exposure of n steps is done, and conversely, if PS is m / 2, m / 2 ² , ..., m / 2 ²ⁿ , the exposure of under exposure of the step is performed. Can be In the above, the time corresponding to one discharge of the integrating capacitor 104 can be changed according to the reference level Eγ set in the comparator 103. Ie Ei
As the width from E to Eγ is set narrower, one discharge time,
Therefore, the time corresponding to one count in the counter is
Be shortened. Therefore, by setting the width of Ei to Eγ to be narrow, it becomes possible to perform finer exposure correction.

In summary, the system is based on the photodiode 10
1 is configured to have the functions of a light receiving element for pre-photometry and a light receiving element for exposure control (direct photometry). Further, by changing the counting condition such as the frequency of the counting pulse according to the amount of incident light, it is possible to cover a wide dynamic range with a counter having a relatively small number of bits. Furthermore, using the same 8-bit counter 214,
It is configured to have a counting function (time measuring function) for pre-photometry and a step number setting function for exposure compensation. Switching of each function is based on the fact that the system control microcomputer 400 detects the operation of the trigger button, etc.
This is done by receiving a command issued by the photometric microcomputer 300 and performing a mode switching operation.

In the above system, the shutter is provided inside the lens,
Although this is driven by the circuit in the lens to control the exposure, the idea of the present invention is not limited to this. That is, a focal plane shutter or a driving means (so-called element shutter) of the image pickup device corresponding to the function of the shutter may be provided on the main body side of the apparatus, and the exposure may be controlled by driving this. .

〔The invention's effect〕

In open metering and the like, the photometric means is required to have an extremely wide dynamic range. However, since the present invention has means for changing the counting pulse frequency and other counting conditions as described above, a counter having a relatively small number of stages is applied. With such a simple and small-scale circuit configuration, it is possible to sufficiently cover a wide dynamic range while maintaining the required photometric accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing in detail the main parts of the system shown in FIG. 2, and FIG. 2 is a block diagram showing a system of an electronic still camera including an apparatus as an embodiment of the present invention. (A), (b) and (c) are timing charts for explaining the operation of the present invention, FIG. 4 is a flowchart showing the operation of the device of the present invention, and FIG. 5 is set in the ROM of the device of the present invention. Showing the contents of the created table, No. 6
The drawings are diagrams for explaining the present invention. 100 …… Photometric IC, 101 …… Photodiode, 200 …… Gate array, 210 …… Photometry block, 211 …… Charge / discharge control circuit, 212 …… Divider, 214 …… 8-bit counter, 220 …… Exposure control block, 300 ... Microcomputer for photometry, 3
01 …… D / A converter, 400 …… Microcomputer for system control

Claims (3)

(57) [Claims] 1. A photoelectric conversion means for obtaining a photoelectric conversion output exhibiting a rate of change in accordance with the amount of incident light, and an output corresponding to an integral of the photoelectric conversion output as the exposure time progresses from the time corresponding to the start of the exposure. , An integration target value setting means for variably setting the integration target value in the integration means, and the integration means each time the output of the integration means reaches the integration target value while the exposure is continued. A resetting means, a counting means for counting the number of times the output of the integrating means reaches the integral target value, and a counting target value setting means for variably setting the counting target value in the counting means, An exposure control device configured to perform exposure control based on an integration target value, the counting target value, and a counting result of the counting means. 2. A photoelectric conversion means for obtaining a photoelectric conversion output exhibiting a rate of change according to the amount of incident light, and an output corresponding to an integration of the photoelectric conversion output with the progress of exposure time from the time corresponding to the start of the exposure. , An integration target value setting means for variably setting the integration target value in the integration means, and the integration means each time the output of the integration means reaches the integration target value while the exposure is continued. A resetting means and a counting means for counting the number of times the output of the integrating means reaches the integration target value, and the exposure control is performed based on the integration target value and the counting result of the counting means. An exposure control device characterized by being performed. 3. A photoelectric conversion means for obtaining a photoelectric conversion output exhibiting a rate of change in accordance with the amount of incident light, and an output corresponding to the integration of the photoelectric conversion output with the progress of exposure time from the time corresponding to the start of the exposure. And a means for resetting the integration means each time the output of the integration means reaches a predetermined integration target value while continuing the exposure, and the number of times the output of the integration means reaches the integration target value. And counting target value setting means for variably setting the counting target value in the counting means, and exposure control is performed based on the counting target value and the counting result in the counting means. An exposure control device characterized by being configured.