JPH1132252A - Image-pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image-pickup device which does not require variable density liquid crystal filter and, in addition, can reduce the hue variations of inputted light. SOLUTION: In an image-pickup device, a solid-state image-pickup element inputs light from an object condensed through a lens for prescribed exposure time, and converts the light into electrical signals, while a gain-adjusting circuit amplifies the electric signals. Then a luminance level detecting circuit integrates the electrical signal and calculates the average luminance of the image of the object, and a first comparator generates a compared signal S4 by taking the difference between the average luminance and the discriminated value of a first memory. In addition, a pulse number computing circuit 10 generates a pulse number S5, which determines the exposure time of the solid-state image- pickup element based on the positive/negative polarity of the value of the signal S4 and by taking a signal from a delay element DLY 11 into consideration. Finally, a second comparator 13 compares the magnitudes of the pulse number S5 and discriminated value of a second memory 12, and generates a gain- adjusting signal S6 which decides the gain of the gain-adjusting circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup apparatus for controlling an exposure amount of a camera by using an electronic shutter operation of a solid-state image pickup device.

[0002]

2. Description of the Related Art In recent years, for the purpose of miniaturization and cost reduction of electronic cameras, the control of the exposure amount of the camera is not performed by mechanical control by opening and closing the aperture, but by the electronic shutter operation of the solid-state imaging device. The electronic controls used are beginning to be used.

An apparatus using such electronic exposure amount control is, for example, an exposure amount control apparatus disclosed in Japanese Patent Application Laid-Open No. 1-159470. Hereinafter, the conventional exposure amount control device will be described with reference to FIG.

FIG. 6 is a block diagram showing the structure and operation of a conventional exposure control device. In FIG. 6, reference numeral 61 denotes a lens for condensing light from a subject, 62 denotes a variable density liquid crystal filter, 63 denotes a solid-state imaging device for photoelectrically converting light from the subject obtained through the variable density liquid crystal filter 62, 64
Denotes a variable density liquid crystal filter control circuit, 65 denotes an image amplification circuit, 66 denotes an electronic shutter control circuit, and 67 denotes an image amplification circuit with AGC.

The operation of such a conventional exposure control device is as described below. First, the lens 61 condenses light from a subject to form a subject image, and the solid-state imaging device 63 controls the density variable liquid crystal filter 6 for a predetermined exposure time.
The light is input through the optical amplifier 2 and the subject image is converted into an electric signal according to the amount of the light, and the video amplifier 65 amplifies the electric signal. Next, the density variable liquid crystal filter control circuit 64
Adjusts the density of the variable density liquid crystal filter 62 based on the magnitude of the electric signal from the video amplification circuit 65 to control the intensity of light transmitted through the variable density liquid crystal filter 62; 66 is also a video amplification circuit 65
The solid-state image sensor 63
By controlling the light input time, that is, the exposure time of the solid-state imaging device 63, the amount of light input to the solid-state imaging device 63, that is, the exposure amount, is controlled. And AG
The video amplification circuit with C 67 adjusts the gain of the electric signal amplified by the video amplification circuit 65, and controls the image captured by the camera, that is, the subject image, to an appropriate luminance level. In addition, controlling the exposure time is called an electronic shutter operation,
The exposure time is called an electronic shutter.

[0006]

However, the above-mentioned conventional exposure amount control apparatus is not limited to the density variable liquid crystal filter 62.
Therefore, a volume for installing the variable density liquid crystal filter 62 is required, and a variable density liquid crystal filter control circuit 64 for controlling the variable density liquid crystal filter 62 also needs to be provided. Therefore, the conventional exposure amount control device has a higher cost than the case where the exposure amount is controlled only by controlling the electronic shutter, even though it has a non-mechanical feature for controlling the exposure amount. Has become.

[0007] When the conventional exposure control device controls the exposure using only the electronic shutter, for example, under a light source such as a fluorescent lamp whose luminance is relatively large and whose luminance and hue periodically change. In such an environment, the amount of light is relatively large, so to control the exposure amount, an electronic shutter,
That is, although the exposure time of the solid-state imaging device 63 is shortened,
As the exposure time becomes shorter, the amount of each color component of the light input to the solid-state imaging device 63 greatly changes depending on the exposure timing. In other words, the hue of the light input to the solid-state imaging device 63 greatly changes. was there.

The present invention has a problem that such a conventional exposure control apparatus requires a variable density liquid crystal filter, and the conventional exposure control apparatus controls an exposure time only by an exposure time. In view of the problem that the hue of input light greatly changes when the length becomes short, an object of the present invention is to provide an imaging device that does not require a variable density liquid crystal filter and that reduces the change in hue of input light. Is what you do.

[0009]

According to a first aspect of the present invention, there is provided a light condensing means for condensing light, and the light condensed by the light condensing means is inputted, and the light is converted into electric light for a predetermined exposure time. An image sensor that converts to, a gain adjustment unit that adjusts the gain of the output of the image sensor, so that the output of the gain adjustment unit is appropriate,
A first control unit that outputs a control signal for controlling the exposure time in the image sensor; and a second control unit that controls an adjustment amount of the gain adjustment unit using the control signal. It is an imaging device characterized by the following.

[0010]

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

(Embodiment 1) The configuration of an imaging apparatus according to Embodiment 1 of the present invention will be described together with its operation.

First, the operation of the imaging apparatus according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram illustrating a configuration and an operation of the imaging device according to the first embodiment of the present invention. FIG. 2 is a diagram for supplementing FIG. 1, and is a block diagram showing the configuration and operation of the charge discharging pulse calculation circuit 8 of the imaging device according to the first embodiment of the present invention.

First, the lens 1 condenses light from a subject, and the solid-state imaging device 2 inputs the light S1 for a predetermined exposure time, and according to the amount of the light S1, that is, according to the exposure amount. The electric charge is accumulated, and an analog electric signal (hereinafter referred to as a video signal) S2
Convert to Note that the exposure time is a time during which the solid-state imaging device 2 inputs the light S1, and is also a time from when the solid-state imaging device 2 starts to accumulate charges to when the accumulated charges are discharged. Further, the exposure time is changed based on an instruction of a charge discharging pulse S7 described later.

Thereafter, the gain adjustment circuit 3 outputs the video signal S2
, And a voltage that amplifies the video signal S2 by a predetermined number is applied to the A / D converter 4. The gain adjustment circuit 3 has two modes, a standard mode and a low gain mode having a lower gain (gain) than the standard mode. Based on an instruction of a gain adjustment signal S6 described later, the gain adjustment circuit 3 Is a standard mode or a low gain mode. Standard mode is
The characteristics of the solid-state imaging device 2, the S / N ratio of the video signal S2, and the video signal S that can be converted by the A / D converter 4.
If the mode is determined by the dynamic range, which is the upper and lower limit of the magnitude of 2, and the mode of the gain adjustment circuit 3 is the standard mode, the gain adjustment circuit 3 amplifies the video signal S2 by a predetermined number of times. Is applied to the video signal S2.
On the other hand, if the mode of the gain adjustment circuit 3 is the low gain mode, the gain adjustment circuit 3 amplifies the video signal S2 by a predetermined number smaller than the predetermined number in the standard mode,
For example, a voltage 6 dB lower than the voltage in the standard mode is applied to the video signal S2.

Next, the A / D converter 4 is connected to the gain adjustment circuit 3
The video signal amplified by the above is input, converted into a digital signal, and output to the luminance level detection circuit 5 and the signal processing circuit 27.

Then, the signal processing circuit 27 receives the digitized video signal from the A / D converter 4 and outputs it to the outside.

The brightness level detection circuit 5 also receives the digitized video signal from the A / D converter 4, integrates the video signal for the entire image of the subject, and averages the brightness of the image. It is calculated as a luminance average S3.

Thereafter, the first comparator 7 calculates the luminance average S3
And a predetermined determination value S9 stored in the first memory 6, and a difference therebetween is calculated to generate a comparison signal S4.
For example, when the average luminance S3 is 100 and the determination value S9 is 80, the first comparator 7 generates a comparison signal S4 having a value of 20. Note that the determination value S9
The exposure time of the solid-state imaging device 2 and the gain adjustment are adjusted so that the luminance average S3 is substantially constant, in other words, the luminance of the image output from the signal processing circuit 27 is substantially constant and appropriate. This is a value that serves as a basis for controlling the mode of the circuit 3.

Further, the charge discharging pulse calculating circuit 8 receives the comparison signal S4, and based on the comparison signal S4, determines the number of pulses S5 for determining the exposure time of the solid-state imaging device 2 and the gain of the gain adjustment circuit 3. A gain adjustment signal S6 to be determined is generated.

As shown in FIG. 2, the charge discharging pulse calculating circuit 8 includes a pulse number calculating circuit 10, a delay element DLY11, a second memory 12, and a second comparator 13. The discharge pulse calculation circuit 8 outputs the comparison signal S4
Is input, the pulse number calculation circuit 10 actually inputs the comparison signal S4. When the pulse number calculation circuit 10 inputs the comparison signal S4 for the first time, and when the comparison signal S4 is input at least once, the pulse number S5
Is generated, and the operation of the pulse number calculation circuit 10 differs when a new comparison signal S4 is input. Therefore, the two cases will be described separately.

First, a case where the pulse number calculation circuit 10 inputs the comparison signal S4 for the first time will be described. In that case, that is, when the imaging apparatus inputs light from a subject for the first time, the exposure time of the solid-state imaging device 2 is set to a predetermined time A in advance, and the mode of the gain adjustment circuit 3 is set to the standard mode. Mode is set. The upper limit of the exposure time is a predetermined time A. Under such conditions, the pulse number calculation circuit 10 receives the comparison signal S4 for the first time, and based on the comparison signal S4,
The luminance average S3 of light next input from the subject by the imaging device is substantially the same as the determination value S9 of the first memory 6,
A pulse number S5 for determining the next exposure time is generated. For example, as described above, when the comparison signal S4 is a signal having a positive value such as 20, the pulse number calculation circuit 10
It is determined that the average brightness S3 exceeds the determination value S9, the exposure time of the solid-state imaging device 2 is shortened, the exposure amount is reduced,
A pulse number S5 having a pulse number that makes the luminance average S3 substantially the same as the determination value S9 is generated, and the comparison signal S4 becomes -20.
If the signal has a negative value or a value of 0 as described above, the pulse number calculation circuit 10 determines that the luminance average S3 does not exceed the determination value S9, and determines that the exposure time is the same as the predetermined exposure time A. The pulse number S5 of the number of pulses to be generated is generated.

Next, a case where the pulse number calculation circuit 10 receives the comparison signal S4 at least once, generates the pulse number S5, and then inputs a new comparison signal S4 will be described. In other words, in this case, it is assumed that the exposure time of the solid-state imaging device 2 when the imaging device inputs light based on the comparison signal S4 is X, and the pulse number calculation circuit 1
0 is a new comparison signal S4 based on the exposure time X
Is input, the pulse number calculation circuit 10 calculates the number of pulses S5 generated one or more fields before by the delay element DLY1
The number S8 of charge discharge pulses that have passed 1 is also input. Since the number S8 of charge discharge pulses is the number of pulses serving as a reference for determining the next exposure time, the pulse number calculation circuit 1
0 takes into account the positive and negative values of the comparison signal S4 based on the charge discharge pulse number S8, similarly to the operation of the pulse number calculation circuit 10 when the pulse number calculation circuit 10 inputs the comparison signal S4 for the first time. Then, the average brightness S3 of the light input from the subject next by the imaging device is equal to the determination value S9 of the first memory 6.
The pulse number S5 for determining the next exposure time is generated so as to be substantially the same as.

The upper limit of the exposure time of the solid-state imaging device 2 is the above-mentioned predetermined time A. The exposure time when the image pickup apparatus next inputs light from the subject is set to the pulse number S5. Since the next exposure time is T, the number of pulses of the pulse number S5 is n, and the exposure time T is reduced by time B for each pulse of the pulse number S5. The relational expression of T = A−nB holds.

Therefore, when the comparison signal S4 input to the pulse number calculation circuit 10 is a signal having a positive value, if the comparison signal S4 is input for the first time, for example, 1 Number of pulses S5
Is generated, and if the comparison signal S4 is not the first input, for example, one pulse is added to the number of charge discharging pulses S8 to generate a new number of pulses S5 to shorten the next exposure time T. . When the comparison signal S4 input to the pulse number calculation circuit 10 is a signal of 0, the pulse number calculation circuit 10 generates the pulse number S5 of 0 pulse if the comparison signal S4 is the first input signal. And
The next exposure time T is kept at a predetermined time A, and if the comparison signal S4 is not the first input, a pulse number S5 equal to the charge discharge pulse number S8 is generated, and the next exposure time T is compared. The same time as that based on the signal S4 is maintained. On the other hand, the pulse number calculation circuit 10
Is a negative value of the comparison signal S4 input by
If the comparison signal S4 is input for the first time, the pulse number calculation circuit 10 generates a pulse number S5 of 0 pulse, and then keeps the exposure time T at a predetermined time A. If it is not the first input, for example, the number of charge discharging pulses S8 is reduced by one pulse to generate a new number of pulses S5 not less than 0, and the next exposure time T exceeds the predetermined time A. Make it longer.

The pulse number calculation circuit 10 outputs the pulse number S5 generated as described above to the drive pulse generation circuit 9 and the second comparator 13 included in the charge discharge pulse calculation circuit 8.

After that, the second comparator 13 inputs the pulse number S5 from the pulse number calculation circuit 10 and the judgment value S10 stored in the second memory 12, compares the two values, and compares the magnitudes. If S5 is smaller than the determination value S10,
The second comparator 13 determines that the comparison signal S4 is not too large, and generates a gain adjustment signal S6 of 0 indicating the gain mode of the gain adjustment circuit 3 to the standard mode,
If the pulse number S5 is larger than the determination value S10, the second
The comparator 13 determines that the comparison signal S4 is too large,
A gain adjustment signal S6 of 1 indicating the gain mode of the gain adjustment circuit 3 to the low gain mode is generated and output to the gain adjustment circuit 3.

The drive pulse generation circuit 9 receives the pulse number S5 from the pulse number calculation circuit 10 and outputs the pulse number S5
, And controls the next exposure time T of the solid-state imaging device 2.

The use of the above-described imaging apparatus can overcome the disadvantage that the hue of light input to the imaging apparatus changes greatly. For example, the brightness is relatively large,
Further, in an environment such as a fluorescent lamp that emits light whose hue changes in a cycle of 3 to 5 seconds, the amount of exposure of the solid-state imaging device 2 is large, so that the value of the average brightness S3 is smaller than the determination value S9 of the first memory 6. Also increases. Therefore, the charge discharge pulse calculation circuit 8
The pulse number calculation circuit 10 generates a pulse number S5 that shortens the next exposure time Y. Here, the determination value S10 of the second memory 12 of the charge discharging pulse calculation circuit 8 includes the exposure time Y of the solid-state imaging device 2 at the boundary between the gain mode of the gain adjustment circuit 3 and the standard mode and the low gain mode, for example, 1
If a value corresponding to / 250 seconds is set, the exposure time T based on the instruction of the pulse number S5 from the pulse number calculation circuit 10 is shorter than 1/250 second, such as 1/500 second. In the event that the charge discharge pulse arithmetic circuit 8
The second comparator 13 compares the number of pulses S5 with the determination value S10 stored in the second memory 12 and determines that the value of the luminance average S3 is too large.
A gain adjustment signal S6 for controlling the gain mode of the above to the low gain mode is generated. Thereafter, since the gain mode of the gain adjustment circuit 3 has changed to the low gain mode, the value of the luminance average S3 decreases, and as a result, the value of the luminance average S3 becomes substantially the same as the determination value S9 of the first memory 6. As described above, the exposure time T becomes longer, and the change in the hue of the light input by the imaging device, that is, the change in the hue of the image of the subject captured by the camera becomes inconspicuous.

In the first embodiment, the pulse number calculation circuit 10 generates the pulse number S5 by considering only the sign of the comparison signal S4. However, the pulse number calculation circuit 10 generates the pulse number S5. The method may be the following method. For example, if the value of the comparison signal S4 is 20, the pulse number calculation circuit 10
8, two pulses are added to generate a pulse number S5 that shortens the exposure time T, and the value of the comparison signal S4 becomes -10.
If so, the pulse number calculation circuit 10 generates a pulse number S5 that is one pulse less than the charge discharge pulse number S8 and extends the exposure time T. For example, the pulse number calculation circuit 10 generates the comparison signal S4. In this method, the number of pulses S5 is generated such that the number of pulses does not fall below 0 by adding or subtracting the number of pulses corresponding to the magnitude of the value to the number of charge discharge pulses S8.

(Embodiment 2) The configuration of an imaging apparatus according to Embodiment 2 of the present invention will be described along with its operation.

The difference between the imaging device according to the second embodiment of the present invention and the imaging device according to the first embodiment of the present invention is only the configuration and operation of the charge discharging pulse calculation circuit 8. Only the configuration and operation of the charge discharge pulse calculation circuit 8 will be described with reference to FIG.

FIG. 3 is a block diagram showing the configuration and operation of the charge discharging pulse calculation circuit 8 of the imaging device according to the second embodiment of the present invention.

In FIG. 3, the third memory 15 stores a high-speed determination value S11 which is a basis for the gain mode of the gain adjustment circuit 3 to enter the low gain mode from the standard mode. In addition, the fourth memory 17 stores a low-speed side determination value S12 that is a condition for the gain mode of the gain adjustment circuit 3 to exit from the low gain mode to the standard mode.

As in the case of the second comparator 13 of the first embodiment, the third comparator 16 includes a pulse number S5 from the pulse number calculation circuit 10 and a high-speed determination value stored in the third memory 15. S11 is input and the magnitudes are compared. If the pulse number S5 is smaller than the high-speed determination value S11,
The third comparator 16 determines that the comparison signal S4 is not too large, generates a high-speed determination value signal S13 of 0 indicating the gain mode of the gain adjustment circuit 3 to the standard mode, and generates the pulse number S5. Is larger than the high-speed determination value S11, the third comparator 16 determines that the comparison signal S4 is too large, and instructs the gain mode of the gain adjustment circuit 3 to be in the low gain mode. Value signal S1
3 is output to the signal determination circuit 19.

Similarly to the third comparator 16, the fourth comparator 18 outputs the pulse number S5 from the pulse number arithmetic circuit 10.
And the low-speed side judgment value S12 stored in the fourth memory 17 and comparing the magnitudes thereof. If the pulse number S5 is smaller than the low-speed side judgment value S12, the fourth comparator 18
Determines that the comparison signal S4 is not too large,
A low-speed determination value signal S14 of 0 indicating the gain mode of the gain adjustment circuit 3 to the standard mode is generated, and the pulse number S
If 5 is larger than the low-speed determination value S12, the fourth comparator 18 determines that the comparison signal S4 is large, and the low-speed determination value of 1 indicating the gain mode of the gain adjustment circuit 3 to the low gain mode. A signal S14 is generated, and the signal determination circuit 1
9 is output.

Next, the signal decision circuit 19 receives the high-speed decision value signal S13 and the low-speed decision value signal S14, and the high-speed decision value signal S13 and the low-speed decision value signal S14 are both 1 signals. If so, a gain adjustment signal S6 of 1 for controlling the gain mode of the gain adjustment circuit 3 to the low gain mode is generated. If both the high-speed determination value signal S13 and the low-speed determination value signal S14 are 0 signals, the signal determination circuit 19 controls the gain mode of the gain adjustment circuit 3 to the standard mode. S6
Generate Further, if the high-speed determination value signal S13 and the low-speed determination value signal S14 have different values, the signal determination circuit 19 sets the gain mode of the gain adjustment circuit 3 to the same gain mode as the previous gain mode. A gain adjustment signal S6 for controlling the mode is generated. Thereafter, the signal determination circuit 19 applies the generated gain adjustment signal S6 to the gain adjustment circuit 3
To the gain adjustment circuit 3 to control the gain mode.

As described above, the signal judgment circuit 19
The high-speed-side determination value signal S13 and the low-speed-side determination value signal S14 play a role of providing hysteresis for switching the gain mode of the gain adjustment circuit 3.

When the above-described imaging apparatus is used, the imaging apparatus according to the first embodiment of the present invention uses the pulse number S
When the value of “5” is near the determination value S10 of the second memory 12, the gain mode of the gain adjustment circuit 3 frequently changes between the standard mode and the low gain mode, thereby inputting to the imaging device. Since the amount of light changes, a hunting phenomenon occurs in the image of the subject captured by the camera. The imaging device according to the second embodiment of the present invention is devised to suppress the hunting phenomenon.

For example, as in the first embodiment, in an environment such as a fluorescent lamp, the amount of exposure is large, so the pulse number calculation circuit 10 of the charge discharge pulse calculation circuit 8 determines the next exposure time T
Is generated such that the pulse number S5 is shortened. Here, in any case, the gain adjustment circuit 3 is added to the high-speed determination value S11 of the third memory 15 of the charge discharge pulse calculation circuit 8.
Is set to the exposure time T of the solid-state imaging device 2 for controlling the gain mode to the low gain mode, for example, a value corresponding to 1/500 second.
In any case, a value corresponding to the exposure time T of the solid-state imaging device 2 for controlling the gain mode of the gain adjustment circuit 3 to the standard mode, for example, 1/100 second, may be set as the low-speed side determination value S12. For example, if the exposure time T based on the instruction of the pulse number S5 from the pulse number calculation circuit 10 becomes a time shorter than 1/500 second, for example, 1/1000 second, the signal determination circuit 19 Both the side judgment value signal S13 and the low speed side judgment value signal S14
And the gain adjustment circuit 3 controls the gain mode of the gain adjustment circuit 3 to the low gain mode.
Is generated and output to the gain adjustment circuit 3.

Then, since the gain mode of the gain adjustment circuit 3 has been set to the low gain mode, the value of the luminance average S3 becomes small, and the value of the luminance average S3 becomes the judgment value S9 of the first memory 6.
The exposure time T is controlled so as to be substantially equal to 1/250 second so that the change in the hue of the light input by the imaging device, that is, the change in the hue of the image of the subject captured by the camera is performed. Becomes inconspicuous. Further, thereafter, since the exposure time T is increased to about 1/250 second, the signal determination circuit 19 inputs a signal from the high-speed determination value signal S13 to 0 and tries to exit from the low gain mode. Since the circuit 19 also receives a signal of 0 from the high-speed determination value signal S14, even if the high-speed determination value signal S13 is a signal of 0, the signal determination circuit 19 sets the gain mode of the gain adjustment circuit 3 to low. A gain adjustment signal S6 of 1 for controlling the gain mode is generated and output to the gain adjustment circuit 3. Then, the gain mode of the gain adjustment circuit 3 is maintained in the low gain mode.

As described above, when the gain mode of the gain adjustment circuit 3 is maintained in the low gain mode, the value of the average luminance S3 remains small. The exposure time T is further increased to become 1/100 second or more so as to be substantially the same as the value S9. Thus, when the exposure time T becomes 1/100 second or more, the signal determination circuit 19 outputs the high-speed determination value signal S13.
And the low speed determination value signal S14, a signal of 0 is input to generate a gain adjustment signal S6 of 0 for controlling the gain mode of the gain adjustment circuit 3 to the standard mode. Is released.

When the low gain mode of the gain adjustment circuit 3 is canceled and the mode is changed to the standard mode, the value of the luminance average S3 temporarily increases. That is, the entire image of the subject becomes brighter due to the increase in the gain. However, the exposure amount is adjusted again so that the value of the average luminance S3 becomes substantially the same as the determination value S9 of the first memory 6, and the exposure time T becomes 1/25.
At about 0 seconds, the value of the luminance average S3 becomes an appropriate size, that is, the entire image of the subject has an appropriate luminance level, and the change in the hue of the light input by the imaging device, that is, the image captured by the camera is taken. The change in the hue of the image of the subject becomes inconspicuous.

(Embodiment 3) The configuration of an imaging apparatus according to Embodiment 3 of the present invention will be described along with its operation.

The difference between the imaging device according to the second embodiment of the present invention and the imaging device according to the third embodiment of the present invention is only the configuration and operation of the charge discharging pulse calculation circuit 8. Only the configuration and operation of the charge discharging pulse calculation circuit 8 will be described with reference to FIG.

FIG. 4 is a block diagram showing the configuration and operation of the charge discharging pulse calculation circuit 8 of the imaging device according to the third embodiment of the present invention.

When the signal determination circuit 19 outputs a gain adjustment signal S6 of 1 indicating the gain mode of the gain adjustment circuit 3 to the low gain mode to the gain adjustment circuit 3, the value of the luminance average S3 becomes small. The memory 21 increases the exposure time T so that the value of the luminance average S3 becomes substantially the same as the determination value S9 of the first memory 6, that is, the high-speed side for correcting the pulse number S5 to a small number. Set value S1
5 are stored. When the signal determination circuit 19 outputs the gain adjustment signal S6 of 0 indicating the gain mode of the gain adjustment circuit 3 to the standard mode to the gain adjustment circuit 3, the value of the luminance average S3 becomes large. Is
The low-speed set value S16 for shortening the exposure time T, that is, for correcting the pulse number S5 to a large number, so that the value of the luminance average S3 becomes substantially the same as the determination value S9 of the first memory 6. Is stored.

The signal judgment circuit 19 according to the second embodiment
However, when outputting the gain adjustment signal S6 for controlling the gain mode of the gain adjustment circuit 3 to the gain adjustment circuit 3, the gain adjustment signal S6 is also output to the selector 23 at the same time.

Next, the selector 23 sets the gain adjustment signal S
6 as well as a high-speed set value S15 of the fifth memory 21 and a low-speed set value S16 of the sixth memory 22.

In the case where the gain adjustment signal S6 is a signal for changing the gain mode of the gain adjustment circuit 3 from the standard mode to the low gain mode, in the second embodiment, the exposure time T
Is also controlled to be shorter by the pulse number S5, and the value of the luminance average S3 is significantly reduced. To avoid this, the selector 23 sets the luminance average S based on the gain adjustment signal S6 and the high-speed set value S15 of the fifth memory 21.
The exposure time T is increased, that is, the number of pulses S5 is set so that the value of "3" is substantially equal to the determination value S9 of the first memory 6.
Is corrected to a small number and output to the pulse number calculation circuit 10.

On the other hand, when the gain adjustment signal S6 is a signal for changing the gain mode of the gain adjustment circuit 3 from the low gain mode to the standard mode, in the second embodiment, the exposure time T also depends on the number of pulses S5. It is controlled to be longer, and the value of the luminance average S3 is greatly increased. To avoid this, the selector 23 sets the gain adjustment signal S
6, and the exposure time T is shortened so that the value of the luminance average S3 becomes substantially the same as the determination value S9 of the first memory 6, based on the low-speed side set value S16 of the sixth memory 22, The pulse number S5 is corrected to a large number and output to the pulse number calculation circuit 10.

The pulse number calculation circuit 10 sets the value corrected by the selector 23 as the pulse number S5.
Output to the drive pulse generation circuit 9.

Specifically, taking an example similar to that of the second embodiment, the exposure time T is set to 1/50 such as 1/1000 second.
If the time is shorter than 0 second, the signal determination circuit 19 controls the gain mode of the gain adjustment circuit 3 to the low gain mode.
And outputs the same to the gain adjustment circuit 3. As a result, the value of the luminance average S3 is significantly reduced. In other words, the entire image of the subject is darkened.
The pulse number S5 is corrected to a small number so as to lengthen the exposure time T so that the determination value S9 becomes substantially the same as the determination value S9.
As 5, the signal is output to the drive pulse generation circuit 9.

Similarly, in the case of the example shown in the second embodiment, when the low gain mode of the gain adjustment circuit 3 is canceled and the mode becomes the standard mode, the value of the luminance average S3 increases. The entire image of the subject becomes brighter, but the selector 23 determines that the value of the average brightness S3 is
The exposure time T is set to be substantially the same as the determination value S9.
For example, the pulse number S5 is corrected to be a large number so as to shorten the exposure time T so that the exposure time T is shortened to about 1/100 second to 1/250 second, for example. As the pulse number S5, the drive pulse generation circuit 9
Output to

The image pickup apparatus described above differs from the image pickup apparatus according to the second embodiment of the present invention in that the image changes transiently when switching between the low gain mode and the standard mode, and the image is uncomfortable until the exposure adjustment is completed. This can cancel the transient change of the image.

(Embodiment 4) The configuration of an imaging apparatus according to Embodiment 4 of the present invention will be described along with its operation.

The difference between the imaging device according to the first embodiment of the present invention and the imaging device according to the fourth embodiment of the present invention is controlled based on the instruction of the gain adjustment signal S 6 from the charge discharging pulse calculation circuit 8. Since only the mode control method of the gain adjustment circuit 3 is used, in the fourth embodiment, only the mode control method of the gain adjustment circuit 3 will be described with reference to FIG.

FIG. 5 is a block diagram showing the configuration and operation of the imaging apparatus according to the fourth embodiment of the present invention.

In the first embodiment, the mode of the gain adjustment circuit 3 is controlled to one of the standard mode and the low gain mode by the output from the charge discharge pulse calculation circuit 8. However, in the fourth embodiment, The image pickup apparatus includes a time constant circuit 25 that changes the mode of the gain adjustment circuit 3 substantially continuously from the above-described standard mode to the low gain mode by the output from the charge discharge pulse calculation circuit 8, The mode of the gain adjustment circuit 3 is changed with a constant time constant.

The gain adjustment circuit 3 includes a time constant circuit 25
This is a circuit for continuously changing the gain in response to a continuous change of the gain control signal S17 which is the output of the circuit.

Thus, when the charge discharging pulse calculation circuit 8 changes the mode of the gain adjustment circuit 3 from the standard mode to the low gain mode, that is, when the gain adjustment signal S6 changes from 0 to 1, the time constant circuit 25 changes the gain. Control signal S17
Low potential VL determined from the specifications of the gain adjustment circuit 3
(0 V to 1 V) to a high potential VH (2 to 3.5 V) are slowly changed in about 1 to 3 seconds, and the gain of the gain adjustment circuit 3 is continuously changed.

Conversely, when the charge discharging pulse calculation circuit 8 changes the mode of the gain adjustment circuit 3 from the low gain mode to the standard mode, that is, when the gain adjustment signal S6 changes from 1 to 0, the time constant circuit 25 changes the gain. The control signal S17 slowly changes from a high potential VH determined by the specifications of the gain adjustment circuit 3 to a low potential VL, and continuously changes the gain of the gain adjustment circuit 3.

Therefore, the exposure amount control can follow the change in the gain of the gain adjustment circuit 3 while sufficiently correcting the change, so that it is possible to switch the mode for providing an image that does not seem strange.

In the present invention, a lens 1 as a light condensing means, a solid-state image pickup element 2 as an image pickup element, a gain adjustment circuit 3 as a gain adjustment means, a first comparator 7 as a first control means, and a pulse number calculation circuit 10 Delay element DLY11, or
First comparator 7, pulse number operation circuit 10, and delay element DLY
11, a selector 23, and a second comparator 1 as second control means.
3, or the third comparator 16 and the fourth comparator 18 and the signal determination circuit 19, or the third comparator 16 and the fourth comparator 18
And a signal determination circuit 19 and a time constant circuit 25.

In the low gain mode of the gain adjustment circuit 3 of the first embodiment, the voltage applied to the video signal S2 is, for example, 6 dB lower than the voltage in the standard mode. In the low gain mode of circuit 3,
The voltage applied to the video signal S2 may be a voltage lower by 3 to 20 dB than the voltage in the standard mode.

[0065]

As is apparent from the above description, the present invention can provide an image pickup apparatus which does not require a variable density liquid crystal filter and can reduce a change in hue of input light.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration and an operation of an imaging device according to a first embodiment of the present invention;

FIG. 2 is a block diagram illustrating a configuration and operation of a charge discharge pulse calculation circuit of the imaging device according to the first embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration and operation of a charge discharge pulse calculation circuit of the imaging device according to the second embodiment of the present invention;

FIG. 4 is a block diagram illustrating a configuration and operation of a charge discharge pulse calculation circuit of the imaging device according to the third embodiment of the present invention;

FIG. 5 is a block diagram illustrating a configuration and operation of an imaging device according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration and operation of a conventional exposure amount control device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lens 2 solid-state imaging device 3 gain adjustment circuit 4 A / D converter 5 luminance level detection circuit 6 first memory 7 first comparator 8 charge discharge pulse calculation circuit 9 drive pulse generation circuit 10 pulse number calculation circuit 11 delay element DLY 12 second memory 13 second comparator 15 third memory 16 third comparator 17 fourth memory 18 fourth comparator 19 signal determination circuit 21 fifth memory 22 sixth memory 23 selector 25 time constant circuit 26 gain adjustment circuit 27 Signal processing circuit 61 Lens 62 Variable density liquid crystal filter 63 Solid-state imaging device 64 Variable density liquid crystal filter control circuit 65 Image amplification circuit 66 Electronic shutter control circuit 67 Image amplification circuit with AGC

Claims (6)

[Claims] 1. A light collecting means for collecting light, an image pickup element which receives the light collected by the light collecting means and converts the light into electricity for a predetermined exposure time, and an output of the image pickup element. Gain adjusting means for adjusting the gain of the image sensor, first control means for outputting a control signal for controlling the exposure time in the image sensor so that the output of the gain adjusting means is appropriate, and utilizing the control signal. An imaging device comprising: a second control unit that controls an adjustment amount of the gain adjustment unit. 2. The imaging apparatus according to claim 1, wherein said second control means decreases the gain of said gain adjustment means when an exposure time indicated by said control signal is shorter than a predetermined time. 3. The second control means has a set value for two different exposure times, and when the exposure time indicated by the control signal is shorter than any of the two set values, the gain of the gain adjustment means is adjusted. 2. The imaging apparatus according to claim 1, wherein when the exposure time indicated by the control signal is longer than either of the two set values, the gain of the gain adjustment unit is increased. 4. The imaging apparatus according to claim 2, wherein the first control means determines and outputs the control signal in consideration of the change in the gain. 5. The imaging apparatus according to claim 1, wherein said second control means outputs a signal for changing the gain of said gain adjustment means substantially continuously. 6. The imaging apparatus according to claim 1, wherein the control signal is a pulse signal.