JP3387121B2 - Exposure control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, for example.
For video cameras and other imaging devices equipped with optical systems such as
The aperture of the iris that composes the optical system
Auto iris function that automatically adjusts to the appropriate amount and charge
Automatically adjusts the image signal output level by the coupling element
Exposure control with automatic gain control function
It concerns the device. 2. Description of the Related Art Conventionally, an imaging device such as a video camera includes:
For example, as shown in FIG.
This is called imaging light. ) Is the charge via the optical system 101
On the imaging screen of the coupling element, so-called CCD imaging element 103
And an image signal from the CCD image sensor 103
Is supplied to the signal processing circuit 116, the optical system 1
Automatically adjust the amount of imaging light passing through 01 to an appropriate amount
Aperture correction control circuit 10 as an iris aperture adjustment means
4 and the output level of the imaging signal from the CCD imaging device 103.
Gain, an automatic gain adjustment means that automatically adjusts the
An adjustment (hereinafter, referred to as AGC) control circuit 105 is provided.
Is provided. In the aperture correction control circuit 104, the
First, as shown in FIG.
The output signal is supplied to a detection circuit 112, for example, an average detection.
The wave output is taken out. Then, the detection circuit 112
Detection output is supplied to the inverting input terminal of the comparison circuit 113.
Is done. At this time, the non-inverting input terminal of the comparison circuit 113 is
Is a reference voltage for aperture control by the reference power source 114.
Voltage, a so-called reference voltage. this
As a result, the comparison circuit 113 switches the detection circuit 1 to the inverting input terminal.
12 and the reference to the non-inverting input terminal
The reference voltage from the power supply 114 is compared. Soshi
The result of comparison by the comparison circuit 113 is
The iris driving circuit 115 drives the iris 03.
The iris drive circuit 115 is connected to the comparison circuit 11
3, the aperture of the iris 203 is adjusted.
I'm saving. In the AGC control circuit 105,
First, as shown in FIG.
These output signals are supplied to the detection circuit 1 via the AGC circuit 106.
07 and output from the detection circuit 107.
Is supplied to the inverting input terminal of the comparison circuit 108. this
At this time, the inverting input terminal of the
Reference voltage for AGC adjustment by the
Reference voltage is supplied. And this comparison
The circuit 108 detects the detection voltage which is the supply voltage to the inverting input terminal.
Detection output from the path 107 and supply power to the non-inverting input terminal.
Voltage from the reference power supply 109
And compares the result with the limiter 110.
Be paid. This limiter 110 has a maximum gain setting power supply.
111, the voltage for setting the AGC maximum gain,
A large gain setting voltage is supplied. And this limit
The comparator 110 determines the output voltage of the comparison circuit 108, for example,
The upper limit of the maximum gain setting voltage by the large gain setting power supply 111
Restrict as a fixed value. The result is the AGC circuit 1
06. Then, this AGC circuit 106
CCD imaging device 10 based on the output from
3 controls the output level of the image pickup signal. example
For example, the AGC circuit 106 controls the illuminance of the object
This is called subject illuminance. ) Is the maximum gain setting power supply 111
If the illuminance is equal to or higher than the maximum gain setting voltage,
A fixed output level (100 IRE) to the signal processing circuit 116
The gain is controlled so that the above imaging signals are not supplied,
Subject illuminance is set to the maximum gain by the maximum gain setting power supply 111
If the illuminance is less than or equal to the set voltage, output the imaging signal
Control is performed to obtain the maximum gain for the level. [0005] By the way, the above-mentioned shooting
The optical system 101 mounted on the imaging device has a focal length
The so-called zoom lens that can be changed
Have been applied. The optical system 101 is, for example, as shown in FIG.
As shown in FIG. 9, the front lens portion for capturing the imaging light is configured.
The first lens group 201 to enlarge / reduce the imaging light
Second lens group 202 constituting the variator of FIG.
An iris 203 for adjusting the amount of light of the
A third lens group 204 for correcting the direction and an image of the imaging light are formed.
A fourth lens group 205 constituting a focus for
It is composed of a prism 206 for color-separating the imaging light.
You. Therefore, the second lens group 202 is the first lens group 2
01 and within the movable range regulated by the iris 203
Is moved along the optical axis direction, so that the CCD
Without changing the position of the element 103 (the optical system 1
When 01 is composed of a plurality of refractive surfaces, etc.,
Name. ) Can be continuously variable. Here, in order to change the angle of view of the object to be imaged,
When changing the combined focal length of the optical system 101, a so-called
When zooming is performed, as the combined focal length becomes longer,
Accordingly, the incident light beam diameter d of the imaging light gradually becomes wider. You
That is, as shown in FIG.
The optical axis direction from the position closest to the first lens group 201
Along the direction, as shown in FIG.
Abbreviation of movable range restricted by 1 and iris 203
When operated to the intermediate position, the incident light beam diameter d of the imaging light becomes
The width of the squirrel 203 is gradually increased depending on the aperture amount. What
The second lens group 202 is closest to the first lens group 201
In the state shown in FIG. 7, the combined focal length of the optical system 101 is
The shortest distance. And do more zooming
And the incident light beam diameter d of the imaging light is made wider,
The lens group 202 has recently changed to the iris 203 shown in FIG.
Pass through the first lens group 201 before reaching the contact position.
The passing beam diameter of the imaging light and the rear side of the first lens group 201
Will be equal to the diameter of the lens. Note that the second
When the lens group 202 is closest to the iris 203,
The composite focal length of the system 101 is the longest distance. Therefore, the incident light beam diameter d of the image pickup light is the first
It becomes equal to the diameter of the lens on the rear side of the lens group 201.
The imaging light is kept in the first lens group 20 even if the zooming is performed.
1 when passing through the first lens group 201
Vignetting near the outer periphery of the lens, in other words, imaging
The incident light beam diameter d is not the aperture amount of the iris 203 but the
Determined by the diameter of the rear lens of one lens group 201
Therefore, the incident light beam diameter d of the imaging light is constant. this
At this time, the luminous flux diameter of the imaging light passing through the iris 203 and this
The aperture of the iris 203, that is, the aperture of the iris 203
There is a non-interference part between the diameter and the so-called dead zone.
In addition, the width of this dead zone becomes wider with zooming.
Therefore, the F value of the optical system 101 is
Theory determined by the combined focal length and the incident light beam diameter d of the imaging light
Lower than the typical F value (this is called the F drop phenomenon
It is called. ). And this F drop phenomenon
From the CCD image sensor 103 to the signal processing circuit 116.
The output level of the supplied imaging signal is as shown in FIG.
In addition, even if the subject illuminance is the same, the combined focus of the optical
It changes depending on the point distance. For example, the combined focal length of the optical system 101 is
When imaging an imaging target as a short distance, the subject illuminance
L in FIG. ₁₁ The maximum gain set by the power supply 111
If the illuminance is equal to or greater than the gain setting voltage, AGC control
The circuit 105 uses the image pickup signal from the CCD image pickup device 103.
The signal processing is controlled as shown by the solid line in FIG.
The output level of the imaging signal supplied to the logic circuit 116 is 1
00IRE Constant. And the subject illuminance is the maximum gain
Illuminance corresponding to maximum gain setting voltage by setting power supply 111
L ₁₁ If the gain further decreases, the gain of the AGC control circuit 105 becomes the maximum.
Supplied to the signal processing circuit 116 regardless of
The output level of the captured image signal is indicated by a solid line in FIG.
As the illuminance of the subject decreases,
I do. The maximum gain setting by the maximum gain setting power supply 111
Illuminance L equivalent to constant voltage ₁₁ At the shortest composite focal length
Illuminance at which the gain of the AGC control circuit 105 becomes maximum
Called. In addition, the imaging supplied to the signal processing circuit 116
The subject illuminance L at which the signal output level is 50 IRE ₁₂ To
This is referred to as the lowest subject illuminance at the shortest composite focal length. The combined focal length of the optical system 101 is minimized.
When imaging an imaging target as a long distance, as described above,
When the F-drop phenomenon occurs in the optical system 101,
AGC system at the shortest composite focal length due to reduced object illumination
The subject illuminance L at which the gain of the control circuit 105 is maximized ₁₁ Becomes
Previously, the gain of the AGC control circuit 105 was maximized. This
Here, the illuminance L at which the gain of the AGC control circuit 105 is maximized.
_{twenty one} To the AGC control circuit 105 at the longest synthetic focal length.
Is referred to as the subject illuminance at which the gain becomes maximum. And the subject
AGC control circuit 10 in which body illuminance is the longest synthetic focal length
The illuminance L of the subject at which the gain of 5 is maximum _{twenty one} When it gets lower,
Again, the gain of the AGC control circuit 105 is maximized.
Regardless of the imaging signal supplied to the signal processing circuit 116,
As shown by the broken line in FIG.
It gradually decreases as the illuminance of the subject decreases. here,
Output level of imaging signal supplied to signal processing circuit 116
Illuminance L when is 50 IRE _{twenty two} The longest synthetic focal length
Is referred to as the minimum subject illuminance. Therefore, the optical system
As a result of the occurrence of the F drop phenomenon in FIG.
As described above, even if the illuminance of the subject is the same, the signal processing circuit
The output level of the imaging signal supplied to 116 is approximately 10 dB
Will drop. As a result, when the subject illuminance is low,
The performance of the imaging device is significantly degraded. To solve this, the optical system 101 must be configured.
The luminous flux diameter of the imaging light passing through the iris 203
Iris so that it is larger than the opening width of Iris 203
According to the luminous flux diameter of the imaging light passing through
It is necessary to increase the diameter of the county 201. Place
However, if the diameter of the first lens group 201 becomes large,
To increase the weight of the imaging device and reduce its size and weight.
Is not preferred. In addition, the first lens group 201 is enlarged.
Cost increases. The present invention has been made in view of such circumstances.
The composite focal length of the optical system is set to the longest distance.
When imaging an object to be imaged as
Even if the step-up phenomenon occurs, the charge-coupled device
The output level of the supplied image signal is, for example, the sum of the optical system.
When imaging an imaging target with the shortest focal length
Until the illuminance at which the gain of the automatic gain adjustment means is maximized.
With the aim of providing an exposure control device
Target. According to the present invention, there is provided an image pickup apparatus comprising:
Lens system that enables the focal length of the light to be variable and the imaging
An iris that reduces the amount of light from the object to an appropriate amount
Image on the imaging screen of the image sensor via the optical system
Based on an output level of an image signal from the image sensor.
Adjusting the aperture of the iris by adjusting the aperture of the iris.
Node means and automatic gain for adjusting the output level of the image signal
An exposure control device comprising an adjusting means,
Detecting means for detecting a zoom position of a lens system, and the lens
Image sensor according to change of F value with respect to zoom position of system
Storage means for storing the amount of change in the output level of the imaging signal from the camera
And the storage means has a zoom from the detection means.
Output of an image signal from the image sensor corresponding to position information
Outputting the amount of change in level to the automatic gain adjustment means,
The maximum gain of the automatic gain adjustment means is set to
Changing according to the amount of change in the output level of the image signal.
Features. In the exposure control apparatus according to the present invention, the imaging light is
When an image is formed on the imaging screen of the image sensor through the
Wherein the detecting means is a zoom of a lens system constituting the optical system.
The position is detected, and the storage means stores the zoom position from the detection means.
Output level of an image signal from the image sensor corresponding to the position information.
The amount of change in the bell is output to the automatic gain adjusting means,
The maximum gain of the dynamic gain adjustment means,
It is changed according to the change amount of the output level of the signal. An embodiment of an exposure control apparatus according to the present invention will be described below.
Will be described with reference to the drawings. FIG. 1 shows an exposure control apparatus according to this embodiment.
As described above, the light from the object to be imaged can change the focal length
Adjust the amount of light from the lens system 1 and the object to be imaged to an appropriate amount
Charge through an optical system 20 having an iris 2
A coupling device, a so-called CCD imaging device 3
Output from the CCD image pickup device 3.
Based on the bell, the iris 2 arranged in the optical system 20
Iris aperture adjustment means for adjusting the aperture amount
Positive control circuit 21 and automatic adjustment of output level of imaging signal
And an AGC control circuit 22 as a gain adjusting means.
An exposure control device, wherein a lens disposed in an optical system 20
A detection circuit 1 serving as detection means for detecting the zoom position of the system 1
4 and the change in F value with respect to the zoom position of the lens system 1
Of the output level of the imaging signal from the CCD imaging device 3
ROM (Read Only Mem
ory) 15 and the ROM 15
CCD imaging device 3 corresponding to zoom position information from
Controlling the amount of change in the output level of the imaging signal from the AGC
The AGC control circuit 22 outputs the signal to the CC
The output level of the imaging signal from the D imaging device 3 is changed.
It is something that has been done. The optical system 20 has a variable focal length.
A so-called zoom lens, for example,
Before capturing light from the imaging target (that is, imaging light)
A first lens group constituting a ball portion, and an image pickup light which is enlarged / reduced.
Lens group that constitutes a variator, and a luminous flux of imaging light
An iris 2 for adjusting the diameter (or light amount), and an imaging light
A third lens group for correcting the direction and a CCD image sensor for imaging light
The fourth lens which forms a focus for imaging on the imaging screen of No. 3
Lens group and a prism for color-separating the imaging light
Things. Then, the second lens group is the lens described above.
Lens system 1, for example, the first lens group and
Along the optical axis direction within the movable range regulated by the iris 2
The position of the CCD image sensor 3
Variable composite focal length of optical system 20 without changing placement
Can be possible. In FIG. 1, the lens system is used.
Only 1 and iris 2 are shown. The aperture correction control circuit 21 controls the CCD
A detection circuit 10 to which an image signal from the image element 3 is supplied;
The output from the detection circuit 10 and the reference power supply 12
Reference voltage for aperture correction control, so-called reference voltage
And a comparison circuit 11 to which the pressure is supplied.
From the iris drive circuit 13 to which the comparison result is supplied.
It is configured. Note that the iris drive circuit 13
For example, a drive motor or the like is applied. In addition, AGC system
The control circuit 22 is supplied with an image signal by the CCD image sensor 3
AGC circuit 4 and output from AGC circuit 4 are supplied
Detection circuit 6, and the output and
Reference voltage for AGC adjustment by reference power supply 8
A comparison circuit 7 supplied with a reference voltage
The result of comparison by the comparison circuit 7 and output from the ROM 15
CCD imaging corresponding to the zoom position information from the detection circuit 14
The change amount of the output level of the imaging signal from the image element 3 is supplied.
And a limiter 9 to be used. Here, the exposure control apparatus of this embodiment is applied.
When the imaging object is imaged by
Will be described. First, the light from the object to be imaged (ie,
Imaging light) is captured by the CCD imaging device 3 through the optical system 20.
An image is formed on the image screen. At this time, the optical system 20 is configured.
Lens system 1 is operated along the optical axis direction.
Since the combined focal length is variable, the angle of view
It is possible to continuously change and image the object to be imaged.
That is, the lens system 1 is moved within its movable range along the optical axis direction.
Is operated on the imaging object side, the composite focus of the optical system 20 is
A wide-angle image of the object to be imaged can be taken with the distance being the shortest distance.
Lens system 1 moves along its optical axis along the optical axis direction.
When operated on the side of the D imaging device 3, the combined focus of the optical system 20
The image can be taken with the distance as the longest distance. The optical system 20
The position of lens system 1 where the combined focal length is the shortest
Below, this is called a zoom position. ) The shortest composite focal length
And the combined focus of the optical system 20
Set the zoom position of the lens system 1 with the longest distance to the longest distance.
This is referred to as a zoom position that is the focal length. Then, an image pickup signal by the CCD image pickup device 3
Is supplied to the aperture correction control circuit 21 and the aperture correction control is performed.
Will be That is, in the aperture correction control circuit 21, C
An output signal from the CD imaging device 3 is supplied to the detection circuit 10
Then, for example, average detection is performed. And this inspection
The detection output of the wave circuit 10 is the inverted input of the comparison circuit 11
It is supplied to the terminal. At this time, the non-inverting input of the comparison circuit 11 is performed.
The reference terminal by the reference power supply 12
Voltage is supplied. Thereby, the comparison circuit 11
Detection output by the detection circuit 10 to the inverting input terminal and non-inverting
Reference to input terminal by reference power supply 12
Compare with voltage. Then, the ratio by the comparison circuit 11
The comparison result is supplied to the iris drive circuit 13. Soshi
The output from the iris driving circuit 13
The squirrel 3 is driven and controlled. Further, an image signal from the CCD image sensor 3 is
The signal is supplied to the AGC control circuit 22, where the AGC control is performed.
You. At this time, the zoom position of the lens system 1 described above is detected.
It is detected by the output circuit 14. This detection circuit 14
Detects the zoom position of the lens system 1 as shown in FIG.
Variable resistor 16 and the output from the variable resistor 16
/ Digital (A / D) converter 1 supplied with
7 is comprised. And, both of the variable resistors 16
The end has a fixed bias and is installed in the lens barrel of the lens system 1.
The tip of the placed arm can be moved as the lens system 1 moves.
The variable contact portion of the variable resistor 16 is configured to slide.
You. Therefore, the zoom position of the lens system 1 is
16 as a variable voltage. And this is possible
The output from the variable resistor 16 is supplied to the A / D converter 17.
Then, the A / D converter 17 receives the signal from the variable resistor 16.
A / D conversion of the zoom position information of the lens system 1
The zoom position information of the lens system 1 is read from the ROM 15
Supplied to The ROM 15 is, for example, a lens shown in FIG.
The change of the output level of the imaging signal corresponding to the zoom position of the system 1
The amount of chemical conversion is stored. CCD image sensor 3 to signal processing circuit 1
The output level of the imaging signal supplied to the lens system 6 is
The F value of the optical system 20 is a composite focal length corresponding to the zoom position.
And the theoretical F-number determined by the incident light beam diameter d of the imaging light
Decreases with decrease. That is, as shown in FIG.
As shown in FIG.
3 from the zoom position with the shortest composite focal length indicated by.
In the zoom position with the longest combined focal length indicated by the middle 20mm
When operated in this direction (therefore, in this embodiment, the lens
The movable range of the storage system 1 is 20 mm. ), Lens system
Imaging while zoom position 1 is operated from 0 to 18mm
The output level of the signal gradually decreases to 4.5 dB, and furthermore,
The zoom position of the lens system 1 is operated to 18 to 20 mm.
The F drop phenomenon occurred in the optical system 20 during the
The output level of the imaging signal drops sharply to 10 dB
You. The output signal from the detection circuit 14 is stored in the ROM
When supplied to the lens system 15, the ROM 15
Information on the amount of change in the output level of the imaging signal corresponding to the zoom position
Information to the limiter 9 constituting the AGC control circuit 22.
You. Therefore, the A / D converter constituting the detection circuit 14
The output signal from the ROM 17 is the address signal of the ROM 15.
Have been. In the AGC control circuit 22,
An output signal from the CCD image sensor 3 is first supplied to an AGC circuit.
4 is supplied to a detection circuit 6 via the
Is supplied to the inverting input terminal of the comparison circuit 7.
You. At this time, the non-inverting input terminal of the comparison circuit 7
Reference voltage for AGC adjustment from reference power supply 8
Reference voltage is supplied. And this ratio
The comparison circuit 7 detects a signal from the detection circuit 6 to the inverting input terminal.
Reference and reference power supply 8 to non-inverting input terminal
Comparison with the reference voltage, and the comparison result is the limiter
9. And this limiter 9
As described above, the zoom position of the lens system 1
The change amount information of the output level of the corresponding imaging signal is supplied.
ing. Thus, the limiter 9 is controlled by the ROM 15
With the output as the upper limit set value, the amplitude of the output
Apply restriction processing. The result is sent to the AGC circuit 4.
Supplied. The AGC circuit 4 is connected to the limiter 9
Image signal from the CCD image sensor 3 based on the output
Control the output level of the signal. Thus, the AGC control circuit
By controlling the gain of the path 22, the signal processing circuit 5
The output level of the imaging signal supplied to the
Regardless of the angle, that is, the combined focal length of the optical system 20,
It is constant with respect to body illuminance. Here, an image pickup signal from the CCD image pickup device 3
However, the aperture correction control circuit constituting the exposure control apparatus of this embodiment is
Each time when supplied to the path 21 and the AGC control circuit 22.
The change in the gain of the paths 21 and 22 will be described with reference to FIG.
explain. It should be noted that the upper part of FIG.
The gain curve showing the change in the gain of the iris 3
The lower part of FIG. 4 shows the effect of the AGC circuit 4 on the subject illumination.
A gain curve showing the change in gain is shown. Also, the figure
Among the gain curves shown in FIG. 4, each gain curve shown by a solid line is an image.
A composite focal length of the optical system 20 for imaging a target at a wide angle.
The graph shows the change in gain when the separation is set to the shortest distance.
Each gain curve shown by a broken line is a composite focal length of the optical system 20.
Shows the change in gain when is the longest distance. For example, the composite focal length of the optical system 20 is set to be the shortest.
When imaging an imaging target as a distance, the illuminance of the subject is low.
Combined below, until the aperture width of the iris 2 is the maximum,
The gain of the aperture correction control circuit 21 gradually increases. Toes
As the illuminance of the subject decreases, the aperture of the iris 2
The width gradually increases. At this time, the AGC control circuit 22
Is constant. And the opening of iris 2
After the opening width becomes the maximum, the aperture correction control circuit 21
While the gain of the AGC control circuit 22 is constant.
Is the AGC control at the shortest composite focal length where the subject illuminance is shortest
The subject illuminance L at which the gain of the circuit 22 is maximized ₁₁ Until
Therefore, the size gradually increases in accordance with the decrease in the illuminance of the subject.
Then, the illuminance of the subject is AGC at the shortest composite focal length.
The subject illuminance L at which the gain of the control circuit 22 is maximized ₁₁ Becomes
Thereafter, the gain of the AGC control circuit 22 is kept constant. What
If the combined focal length of the optical system 20 is the shortest distance
In this case, the gain of the aperture correction control circuit 21 is maximized.
Illuminance L at which the gain of the GC control circuit 22 starts to increase ₃₁ The most
Aperture correction control circuit 21 and AGC at short composite focal length
This is referred to as the subject illuminance at which the gain of the control circuit 22 switches. The combined focal length of the optical system 20 is set to the shortest distance.
When capturing an image of an object as a separation,
And the aperture width of the iris 2 becomes maximum.
Thus, the gain of the aperture correction control circuit 21 gradually increases.
However, in this case, at the shortest composite focal length described above,
The gains of the aperture correction control circuit 21 and the AGC control circuit 22 are switched off.
Replacement subject illuminance L ₃₁ Optical system 2 with brighter subject illumination
Since the F drop phenomenon occurs at 0, the aperture correction control circuit
The gain of the path 21 is such that the luminous flux diameter of the imaging light passing through the iris 2 is
Will be the largest. Here, the effective maximum of the aperture correction control circuit 21
Subject illuminance L _{twenty one} At the longest composite focal length
The gain of the correction control circuit 21 and the gain of the AGC control circuit 22 are switched.
Object illuminance. And pass through iris 2
The luminous flux diameter of the imaging light is smaller than that of the rear lens of the first lens group 201.
At the longest synthetic focal length, as determined by the diameter
The gains of the aperture correction control circuit 21 and the AGC control circuit 22 are
Switching subject illuminance L _{twenty one} Even if the illuminance of the subject is
The effective gain of the correction control circuit 21 is fixed. So
As a result, the effective gain of the aperture correction control circuit 21 becomes maximum.
Thereafter, the gain of the AGC control circuit 22
Of imaging signals corresponding to the zoom position of the lens system 1
Based on the level change information, the subject illuminance
The gain of the AGC control circuit 22 at the point distance becomes maximum.
Subject illumination L ₁₁ Until the brightness of the subject decreases
It grows gradually. Then, the gain of the AGC control circuit 22
Is the AGC control at the shortest composite focal length where the subject illuminance is shortest
The subject illuminance L at which the gain of the circuit 22 is maximized ₁₁ Since
Descending, constant. Therefore, when imaging an object to be imaged,
The angle of view of the object to be imaged, that is, the combined focal length of the optical system.
Output of imaging signal supplied to signal processing circuit regardless of separation
The level is constant with respect to the subject illuminance. As described above, one embodiment of the exposure control apparatus according to the present invention.
Although an example has been described, the present invention is limited to the above-described embodiment.
It is not intended to depart from the spirit of the present invention.
Can be changed. For example, as shown in FIG.
After the control circuit 22, regardless of the combined focal length of the optical system
Set the output level of the imaging signal supplied to the signal processing circuit to the object
An imaging signal from the ROM 15 to be constant with respect to the illuminance
AGC control circuit 22 based on the output level change amount information of
A gain control amplifier circuit 18 for increasing the output of the
No. At this time, the AGC control circuit 22 controls the CCD
An AGC circuit 4 to which an image pickup signal from the image element 3 is supplied;
A detection circuit 6 to which an output from the AGC circuit 4 is supplied;
Output from the detection circuit 6 and A from the reference power supply 8
From the comparison circuit 7 supplied with the reference voltage for GC adjustment
It may be composed. As a result, the same effect as above
Can be obtained. Other configurations are the same as those of the above-described embodiment.
Since it is the same, detailed description is omitted. As is clear from the above description, the present invention
According to the exposure control apparatus of the present invention, the imaging light is transmitted through the optical system.
When an image is formed on the imaging screen of the
The step detects the zoom position of the lens system constituting the optical system.
The storage means stores the zoom position information from the detection means.
A corresponding change in the output level of the image signal from the image sensor.
And outputting the amount to the automatic gain adjustment means.
Means for maximizing the gain of the imaging signal output from the imaging device
Since it is changed according to the level change amount, the image pickup device
The output level of the image signal from the camera depends on the angle of view of the object.
Rather, it is constant with respect to the subject illuminance. Therefore,
Poor performance when subject illuminance is low in conventional imaging devices
The lower can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an exposure control device according to the present invention. FIG. 2 is a block diagram illustrating a schematic configuration of a detection circuit included in the exposure control device according to the present invention. FIG. 3 is a characteristic diagram illustrating a change in an output level of an image pickup signal based on an F-drop phenomenon with respect to a position of a lens system included in an optical system. FIG. 4 is a characteristic diagram illustrating a change in a gain of an AGC control circuit and a change in a gain of an iris of an optical system with respect to a subject illuminance. FIG. 5 is a block diagram showing a schematic configuration of another embodiment of the exposure control apparatus according to the present invention. FIG. 6 is a block diagram showing a schematic configuration of a conventional exposure control device. FIG. 7 is a side view showing a state in which the composite focal length of the zoom lens is set to the shortest distance. FIG. 8 is a side view showing a state in which the composite focal length of the zoom lens is set to an intermediate distance. FIG. 9 is a side view showing a state in which the combined focal length of the zoom lens is set to the longest distance. FIG. 10 is a characteristic diagram illustrating a change in an output level of an imaging signal with respect to a subject illuminance. [Explanation of symbols] 1 ····· Lens system 2 ····· Iris 3 ····· CCD imaging device 14 ···· Detection circuit 15 ····· ROM 20 ······ Optical system 21 Aperture correction control circuit 22 AGC control circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-222586 (JP, A) JP-A-2-75285 (JP, A) JP-A-5-100281 (JP, A) JP-A-4- 107078 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 5/222-5/257

Claims (1)

(57) [Claims 1] A lens system having a variable focal length of light from an object to be imaged and an iris to reduce the amount of light from the object to an appropriate amount. An iris aperture adjustment means for adjusting the aperture of the iris based on an output level of an image signal from the image sensor, and an iris aperture adjusting means, An exposure control device comprising: an automatic gain adjustment unit that adjusts an output level; a detection unit that detects a zoom position of the lens system; and the imaging according to a change in an F value with respect to the zoom position of the lens system. Storage means for storing a change amount of an output level of an imaging signal from an element, wherein the storage means stores a change amount of an output level of an imaging signal from the imaging element corresponding to zoom position information from the detection means. Said Outputs to the dynamic gain adjustment means, said automatic gain a maximum gain adjustment means, an exposure control apparatus characterized by varied depending on the amount of change in the output level of the imaging signal from the imaging device.