JPH08279957A - Image pickup device - Google Patents

Abstract

PURPOSE: To hold an optimum exposure state and to obtained an intentioned image by correcting the exposure state of an exposure control means which is held by an exposure state holding means in accordance with a detection signal outputted from a focus distance detecting means. CONSTITUTION: An exposure correcting circuit 17 is provided with look-up tables (LUTs) storing data for correcting a change in brightness by changing an F value in accordance with the focal distance of a zoom lens 1. A triger signal from a trigger key 14 is inputted to the circuit 17, the stop state of an AE-locked stop mechanism is detected by a stop encoder 5 and the focal distance of a lens 1 is detected by a zoom encoder 4. An LUT corresponding to the stop state of the mechanism 2 is selected and F value correcting data corresponding to the focal distance of the lens 1 detected from the selected LUT are selected as reference data. When the focal distance of the lens 1 is changed, F value correcting data corresponding to the focal distance are selected from the LUT. The selected correction data are compared with the reference data to find out a necessary correction value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to exposure control of an image pickup device.

[0002]

2. Description of the Related Art Conventionally, exposure control in an image pickup device such as a video camera has been performed so that the aperture of the diaphragm, the storage time (electronic shutter) of the image pickup device, and the AGC circuit can be adjusted so that the level of the video signal becomes constant at a predetermined value. A method of controlling the gain is used.

Such a structure and operation will be described below with reference to the block diagram of FIG.

In FIG. 4, reference numeral 1 denotes an image forming lens group for an object, which is composed of a zoom lens whose focal length is variable. 2 is a diaphragm mechanism such as an iris having a diaphragm blade structure for controlling the amount of incident light and liquid crystal means for controlling the amount of transmitted light. Here, the case where an iris is used is shown, 3 is an image pickup device for photoelectrically converting incident light, and 6 Is a drive motor such as an IG meter for driving the diaphragm mechanism means, and 7 is an image sensor control for controlling a so-called electronic shutter function for controlling the image sensor 3 to read out a photoelectrically converted signal and controlling a signal accumulation time. Circuit.

Reference numeral 8 is a sample and hold circuit for sampling the signal photoelectrically converted by the image pickup device 3, 9 is an automatic gain control circuit (hereinafter referred to as AGC circuit) for electrically amplifying the signal, and 10 is gamma correction, color separation, and color difference. A camera signal processing circuit that generates a standard television signal by adding a synchronization signal after processing such as a matrix.An analog signal processing circuit that processes in an analog signal state, an analog-digital conversion of a video signal, a digital signal There is a method such as a digital signal processing circuit that performs digital-analog conversion after performing processing in the state, but here, the case where an analog signal processing circuit is used will be taken as an example.

Reference numeral 11 is a video tape recorder (hereinafter referred to as VTR) for recording a video signal on a tape, and 12 is an electronic viewfinder (hereinafter referred to as EVF) for monitoring an image being photographed.

Reference numeral 13 is an exposure detection circuit that detects the exposure state of the subject from the output signal of the AGC circuit 9, and 22 is controlled by the diaphragm mechanism 2 and the image pickup device control circuit 7 based on the detection signal output from the exposure detection circuit 13. An exposure control circuit that controls the shutter speed of the electronic shutter, the gain of the AGC circuit 9, and the like, 16 is an iris drive circuit that moves a motor that drives the aperture mechanism 2 in accordance with the output of the exposure control circuit 22, and 14 is AE that holds exposure control status
A trigger key for inputting a trigger signal for performing a lock operation.

Looking inside the exposure control circuit 22, the AGC gain, the signal indicating the exposure state such as the integrated value of the brightness level output from the exposure detection circuit 13 are respectively calculated.
An exposure calculation unit 13a that calculates control information for each of the shutter speed of the electronic shutter and the opening amount of the iris, the AGC gain output from the exposure calculation unit 13a, the shutter speed of the electronic shutter, and the control information for each opening amount of the iris.
An AGC data hold unit 13b and an electronic shutter data hold unit 13 that hold the trigger key 14 in accordance with the operation thereof.
c, the data hold section 13h including the iris data hold section 13d, the AGC data hold section 13b, the electronic shutter data hold section 13c, and the gain of the AGC circuit 9 according to the respective data supplied through the iris data hold section 13d. An AGC control unit 13e, an electronic shutter control unit 13f, and an iris control unit 13g that respectively control the speed of the electronic shutter of the image sensor 3 and the opening amount of the iris 2 are configured.

In the image pickup apparatus having the above-mentioned structure, in order to make it possible to obtain an optimum image by simple photographing in various places and under various conditions, the exposure detection circuit 13 makes the brightness of the subject more than the image signal. Of the exposure control parameter based on the detection signal of the exposure detection circuit 13 in the exposure control circuit 22 and the electronic shutter for controlling the storage time of the diaphragm mechanism 2, the image pickup device 3, the gain of the AGC circuit 9, and the like. The selection and correction amount of each parameter are determined, and control is performed so that stable and optimum exposure is always achieved. As a result, even if the brightness of the subject changes, it is possible to provide an automatic exposure control means for automatically performing optimum exposure control without bothering the photographer.

However, since the above-mentioned automatic exposure control means always controls the exposure state according to the brightness of the subject coming from the zoom lens 1, the zoom is performed even if the brightness of the main subject does not change. When the brightness of the surrounding subject changes due to the change of the focal length by the lens 1 or the movement of the main subject, the exposure control state also changes.

Therefore, even if the exposure state of the main subject is optimum, if the brightness of the peripheral subject changes, the exposure control state changes, and as a result, the exposure state of the main subject becomes unsuitable.

In order to deal with such a photographing situation, so-called AE lock means, which is an exposure state holding means for holding an optimum exposure control state, has been devised conventionally. AE
The operation of the lock means is an EVF which is a monitor means by the photographer.
When the exposure state that the user wants to hold while checking the screen of 12 is input, by inputting a trigger signal from the trigger key 14, the data hold section of the exposure control circuit 22 is controlled to the hold state at the time when the trigger signal is input. This is performed by holding the correction amount of each exposure control parameter of the aperture mechanism 2, the electronic shutter that controls the storage time of the image sensor 3, and the gain of the AGC circuit 9 calculated by the exposure control calculation unit.

The AE lock means has a large difference in brightness between the main subject and the surrounding subject, and when the exposure state of the main subject is not optimal by the automatic exposure control means, for example, in the case of photographing a person against backlight, the background is bright. The exposure state of the person will be darkened by the part, so-called black out, or conversely, the exposure state of the person will become too bright in the case of over-exposure like shooting a person illuminated by a spotlight. In a so-called overexposure situation, by changing the focal length of the zoom lens 1 to zoom up the main subject, the influence of the brightness of the surrounding subject is eliminated, and the exposure state of the main subject is optimized. There is a method in which the AE lock operation is performed, then the focal length of the zoom lens is returned, and shooting is started in accordance with the image frame intended by the photographer.

[0014]

However, even though the AE lock means is used as described above, even if the amount of incident light from the zoom lens 1 is constant and the diaphragm mechanism 2 for limiting the amount of incident light is constant. Since the F value of the zoom lens changes depending on the focal length of the zoom lens, the amount of light incident on the element surface of the image pickup element 3 changes, and even if the AE lock operation is performed in the optimum state, the focal length of the zoom lens changes. Although the control state of the exposure control parameters such as the diaphragm mechanism means, the AGC, and the electronic shutter has not changed, the exposure state at the time of performing the AE lock operation changes, and the optimum exposure state cannot be maintained. is there.

Therefore, an object of the present invention is to use the AE lock means to change the focal length of the zoom lens
An object of the present invention is to provide an imaging device capable of maintaining an optimum exposure state at the time of performing an E-lock operation.

[0016]

In order to achieve such a object, according to the invention described in claim 1 of the present application, a zoom lens which is an imaging lens group of a subject and whose focal length is variable is provided. An image pickup device (corresponding to the image pickup device 3 in the embodiment) that photoelectrically converts light incident through the zoom lens (corresponding to the zoom lens 1 in the embodiment),
A signal processing unit (corresponding to the camera signal processing circuit 10 in the embodiment) that processes a signal photoelectrically converted by the image pickup device to generate a video signal to be a television signal, and an exposure state according to the video signal. Exposure control means for controlling (corresponding to the exposure control circuits 15, 19, 20 in the embodiment)
And an exposure state holding means for holding the exposure state of the exposure control means (in the embodiment, the AGC data holding unit 15b,
(Corresponding to the electronic shutter data hold unit 15c and the iris data hold unit 15d), a focal length detecting unit for detecting the focal length of the zoom lens (corresponding to the zoom encoder 4 in the embodiment), and the focal length detecting unit. And an exposure correction unit (corresponding to the exposure correction circuit 17 in the embodiment) for correcting the exposure state of the exposure control unit held by the exposure state holding unit in accordance with the detection signal of. .

According to a second aspect of the present invention, in the first aspect, the signal processing means is an automatic gain control means for electrically amplifying a video signal (corresponding to the AGC circuit 9 in the embodiment). The exposure correction means is configured to correct the exposure control state by controlling the gain of the automatic gain control according to the change in the focal length of the zoom lens.

According to a third aspect of the present invention, in the first aspect, the exposure control means has an electronic shutter function for controlling the accumulation time of the image pickup device (in the embodiment, the image pickup device control circuit 7). The exposure correction means is configured to correct the exposure control state by controlling the storage time of the image sensor according to the change of the focal length of the zoom lens. .

According to a fourth aspect of the present invention, in the first aspect, the signal processing means has an automatic gain control means for electrically amplifying a video signal, and the exposure control means comprises: The exposure correction means has an electronic shutter function for controlling a storage time of the image pickup device, and the exposure correction unit controls a gain of the automatic gain control and a storage time of the image pickup device according to a change in a focal length of the zoom lens. Is configured to correct the exposure control state.

According to the invention of claim 5 of the present application, a zoom lens (corresponding to the zoom lens 1 in the embodiment) which is a lens group for imaging an object and whose focal length is variable, and the zoom lens. An image pickup device (corresponding to the image pickup device 3 in the embodiment) that photoelectrically converts light incident by
A diaphragm means (which corresponds to the diaphragm mechanism 2 in the embodiment) that limits the amount of light incident on the image sensor, and an aperture state detection means (which corresponds to the diaphragm encoder 5 in the embodiment) that detects the diaphragm state of the diaphragm means. A signal processing means (corresponding to the camera signal processing circuit 10 in the embodiment) for processing a signal photoelectrically converted by the image pickup device to generate a video signal to be a television signal, and an exposure state according to the video signal. Exposure control means (corresponding to the exposure control circuit 15 in the embodiment) and exposure state holding means (in the embodiment, AGC data hold unit 15b, electronic shutter data) for holding the exposure state of the exposure control means. (Corresponding to the hold unit 15c and the iris data hold unit 15d), and the focal length detecting means (in the embodiment, the zoom lens) for detecting the focal length of the zoom lens. (Corresponding to the coder 4), the detection signal of the focal length detection means and the output signal of the aperture state detection means, and an exposure correction means (an exposure correction circuit in the embodiment) for correcting the exposure state of the exposure control means. (Corresponding to 17).

According to a sixth aspect of the present invention, in the fifth aspect, the signal processing means is an automatic gain control means for electrically amplifying a video signal (corresponding to the AGC circuit 9 in the embodiment). The exposure correction means is configured to correct the exposure control state by controlling the gain of the automatic gain control according to the change in the focal length of the zoom lens.

According to the invention of claim 7 in the present application, in claim 5, the exposure control means has an electronic shutter function for controlling the accumulation time of the image sensor (in the embodiment, the image sensor control circuit 7). The exposure correction means is configured to correct the exposure control state by controlling the storage time of the image sensor according to the change of the focal length of the zoom lens. .

According to the invention described in claim 8 of the present application, in claim 5, the signal processing means corresponds to an automatic gain control means (in the embodiment, the AGC circuit 9) for electrically amplifying a video signal. ), The exposure control means has an electronic shutter function (corresponding to the image sensor control circuit 7 in the embodiment) for controlling the accumulation time of the image sensor, and the exposure correction means has the zoom lens. The exposure control state is corrected by controlling the gain of the automatic gain control and the storage time of the image sensor according to the change of the focal length of the.

[0024]

According to the first aspect of the present invention, the change in the focal length is detected when the zoom operation is performed during the AE lock in which the exposure state is held by the exposure state holding means. The exposure state of the exposure control means, which is held by the exposure state holding means, is corrected, and the change of the exposure due to the change of the F value due to the change of the focal length of the zoom lens is corrected.

According to the second aspect of the present invention, when the zoom operation is performed during the AE lock in which the exposure state is held by the exposure state holding means,
By detecting the change in the focal length and controlling the gain of the automatic gain control, the exposure state of the exposure control means held by the exposure state holding means is corrected, and F due to the change in the focal length of the zoom lens is corrected. The change in exposure due to the change in value is corrected.

According to the third aspect of the present invention, when the zoom operation is performed during the AE lock in which the exposure state is held by the exposure state holding means,
By detecting the change in the focal length and controlling the shutter speed of the electronic shutter, the exposure state of the exposure control means held by the exposure state holding means is corrected, and F due to the change in the focal length of the zoom lens is corrected. The change in the exposure due to the change in the value is corrected for the change.

According to the invention of claim 4 of the present application, when the zoom operation is performed during the AE lock in which the exposure state is held by the exposure state holding means,
By detecting the change in the focal length and controlling the gain of the automatic gain control and the shutter speed of the electronic shutter, the exposure state of the exposure control means held by the exposure state holding means is corrected, and the zoom lens The change in the exposure caused by the change in the F value due to the change in the focal length is corrected.

According to the invention of claim 5 of the present application, when the zoom operation is performed during the AE lock in which the exposure state is held by the exposure state holding means,
The exposure state of the exposure control means, which is held by the exposure state holding means, is corrected according to the change of the focal length and the state of the aperture, and the exposure caused by the change of the F-number due to the change of the focal length of the zoom lens. Changes are corrected.

According to the invention of claim 6 of the present application, when the zoom operation is performed during the AE lock in which the exposure state is held by the exposure state holding means,
By detecting the change of the focal length and the state of the diaphragm and controlling the gain of the automatic gain control, the exposure state of the exposure control means held by the exposure state holding means is corrected, and the focal length of the zoom lens is corrected. The change in exposure due to the change in F value due to the change in is corrected.

According to the invention of claim 7 of the present application, when the zoom operation is performed at the time of AE lock in which the exposure state is held by the exposure state holding means,
The exposure state of the exposure control means held by the exposure state holding means is corrected by detecting the change of the focal length and the state of the diaphragm to control the shutter speed of the electronic shutter, and the focal length of the zoom lens is corrected. The variation of the exposure due to the variation of the F value due to the variation of is corrected.

According to the invention of claim 8 of the present application, when the zoom operation is performed at the time of the AE lock in which the exposure state is held by the exposure state holding means,
By controlling the gain of the automatic gain control and the shutter speed of the electronic shutter according to the change of the focal length and the state of the diaphragm, the exposure state of the exposure control means held by the exposure state holding means is corrected, The change in the exposure caused by the change in the F value due to the change in the focal length of the zoom lens is corrected.

Further, according to the invention described in each of the claims of the present application, there is provided the AE lock means capable of maintaining the optimum exposure state at the time of performing the AE lock operation even if the focal length of the zoom lens is changed. Even if the AE lock means is used, the focal length can be changed to perform shooting in accordance with the angle of view intended by the photographer, and it is possible to provide an optimal image according to various subjects and shooting conditions. .

[0033]

【Example】

(First Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. The parts shown by the same reference numerals as those in the conventional example shown in FIG. 4 have the same functions as in the conventional example, and the description thereof will be omitted.

The process of processing the video signal is similar, and in the present invention, the zoom encoder 4 as the focal length detecting means for detecting the focal length of the zoom lens 1 and the diaphragm for detecting the diaphragm state of the diaphragm mechanism 2 as the diaphragm means. A diaphragm encoder 5 as a state detecting means and an exposure correction circuit 17 as an exposure correcting means for correcting a change in the F value depending on the focal length of the zoom lens are added, and 15 is an exposure control circuit as an exposure controlling means.

Internal component 1 of the exposure control circuit 15
5a to 15h correspond to the internal components 22a to 22h of the exposure control circuit 22 of FIG. 4, respectively, and the configurations here are the same.

The exposure correction circuit 17 as the exposure correction means of the present invention is provided with a look-up table (hereinafter referred to as LUT) which stores data for correcting a change in brightness due to a change in F value depending on the focal length of the zoom lens 1. I have it.

For example, assuming that the F-number characteristic with respect to the focal length of the zoom lens 1 has the characteristic shown in FIG. 5, the amount of incident light from the zoom lens 1 is constant and the diaphragm mechanism 2 is in the open state. The brightness of the image pickup surface of the image pickup element 3 is 10 when the focal length of the zoom lens 1 is at the wide end.
When it is 0%, it fluctuates corresponding to the change of the F value as shown in FIG. In the characteristic diagram of FIG. 5, the horizontal axis represents the focal length of the zoom lens, and the vertical axis represents the aperture value F.

The LUT provided in the exposure correction circuit 17 is
The F value correction data for correcting the change in brightness with respect to the focal length in FIG. 6 by the gain of the AGC circuit 8 is provided. The horizontal axis of the characteristic diagram of FIG. 5 indicates the focal length of the zoom lens,
The vertical axis represents brightness.

Further, when the diaphragm mechanism 2 is stopped down to, for example, the state of F2, the change of the F value of the zoom lens is apparently as shown in FIG. 5 on the element surface of the image pickup element 2, and the image pickup element 2 at that time is changed. The brightness on the imaging surface changes as shown in FIG.

Therefore, since the change of the F value with respect to the focal length differs depending on the state of the diaphragm mechanism 2, the F value correction data provided in the exposure correction circuit 17 is the LUT as shown in FIG. 7 according to the diaphragm state of the diaphragm mechanism 2. Is equipped with.

Next, the operation of the AE lock means which is a feature of the present invention will be described.

Normally, as in the conventional example shown in FIG. 4, the exposure change circuit 13 detects the change of the exposure due to the change of the subject from the image signal by the automatic exposure control means, and the exposure control circuit 15 detects the change of the exposure. Based on the detection signal, the exposure control calculation unit 15a selects an exposure control parameter such as the electronic shutter for controlling the accumulation time of the diaphragm mechanism 2 and the image sensor 3, the gain of the AGC circuit 9, and calculates the correction amount of each parameter. Then, control is performed so that stable and optimum exposure is always obtained.

The selection of these exposure control parameters and the correction amount of each parameter are performed by the AGC data holding unit 15b, the electronic shutter data holding unit 15c, and the iris data holding unit 15d, respectively.
5e, electronic shutter controller 15f, iris controller 15
It is supplied to g to control the AGC circuit 9, the image pickup device control circuit 7, and the iris control circuit 16 so that stable and optimum exposure is always achieved.

Next, when the photographer wants to maintain the proper exposure state, the AE lock means is operated. In particular,
By inputting the trigger signal from the trigger key 14,
The corner data hold units 15b to 15d in the data hold unit 15h of the exposure control circuit 15 are interlocked with the trigger signal.
Is controlled to the hold state, and the correction amount of each exposure control parameter of the aperture mechanism 2, the electronic shutter that controls the storage time of the image sensor 3, and the gain of the AGC circuit 9 calculated by the exposure control calculation unit 15a at that time is held. To do. As a result, the exposed state at that time is maintained.

At this time, the trigger signal of the trigger key 14 is input to the exposure compensation circuit 17, and the aperture state of the aperture mechanism 2 at the time of the AE lock operation is detected by the aperture encoder 5 as aperture state detection means by the trigger signal. In addition, the focal length of the zoom lens 1 is detected by the zoom encoder 4 as the focal length detecting means, the LUT corresponding to the detected diaphragm state of the diaphragm mechanism 2 is selected, and the focus of the zoom lens 1 detected by the selected LUT is selected. The F value correction data corresponding to the distance is selected and used as the reference data.

Next, when the focal length of the zoom lens 1 changes, the focal length at that time is detected, and the F value correction data corresponding to the focal length is selected from the selected LUT.

Then, the selected F value correction data is compared with the reference data to obtain a necessary correction amount.

For example, when the reference data at the time of AE lock operation is in the state of LUT1 in FIG. 7, the correction amount when the focal length changes to is +6 dB, and the correction amount when the focal length changes to The amount is -5 dB. This correction amount is corrected with respect to the gain data of the AGC circuit 8 held at the data hold unit at the time of the AE lock operation, and the gain of the AGC circuit 8 is controlled by the correction result.

The above-described operation always detects the change of the focal length, and every time the focal length changes, the variation of the brightness due to the F value of the lens is corrected by the gain of the AGC circuit 8 to keep the exposure state in the optimum state. Control to lean.

(Second Embodiment) FIG. 2 is a block diagram showing the configuration of the second embodiment of the present invention.

The second embodiment shows a case where the camera signal processing circuit of the first embodiment is used with a camera signal processing circuit 18 for performing digital signal processing. As a result, the exposure detection circuit 13, the exposure control circuit 15, and the exposure correction circuit 1 of the first embodiment.
The processing in 7 can be performed in a digital signal state by using the microcomputer 19, and can be realized with a simple configuration.

The function of each circuit and the correction operation are the same as those in the first embodiment, and further description will be omitted.

(Third Embodiment) FIG. 3 is a block diagram showing the configuration of the third embodiment of the present invention.

In the first embodiment, the exposure correction means 17 is provided with F value correction data for correcting the change in brightness due to the change in F value depending on the focal length of the zoom lens 1 by the gain of the AGC circuit 8. However, in the third embodiment, it is possible to correct even the speed of the electronic shutter that controls the storage time of the image sensor 3. Therefore, the LUT of the exposure compensating means 21 of the third embodiment is provided with F value compensation data based on electronic shutter data.

In the third embodiment, the correction operation is the same as that of the first embodiment, although the correction parameters are different.

The correction may be performed by using both the AGC and the electronic shutter as the correction parameter.

[0058]

As described above, according to the first aspect of the present invention, the zoom lens is driven while the exposure state controlled by the exposure state holding means is held. In this case, the exposure correction means corrects the held exposure control state in accordance with the change in the focal length, so that even if the focal length of the zoom lens changes, the optimum state at the time of the exposure state holding operation is performed. There is an effect that the exposure state is maintained and the image as intended by the photographer can be provided.

According to the second aspect of the present invention, since the correction by the exposure correction means is performed by the gain control of the automatic gain control circuit, the exposure control state according to the focal length of the zoom lens can be achieved. It is possible to make fine adjustments, and even if the focal length of the zoom lens changes, the optimum exposure state at the time of performing the exposure state holding operation is maintained, and there is the effect that the image as intended by the photographer can be provided. .

Further, according to the invention of claim 3 in the present application, since the correction by the exposure correction means is performed by controlling the accumulation time of the image pickup device, the exposure control state according to the focal length of the zoom lens is performed. Is corrected, the range that can be corrected becomes wider, and the optimum exposure state at the time of performing the exposure state holding operation is maintained even if the focal length of the zoom lens changes.
This has the effect of providing the image as intended by the photographer.

Further, according to the invention of claim 4 in the present application, the correction in the exposure correction means is performed by the gain control of the automatic gain control means and the accumulation time control of the signal of the image pickup device, so that the zoom lens The exposure control state, which changes according to the focal length of the, is corrected, the range that can be corrected is widened, and finer correction is possible, and even when the focal length of the zoom lens changes, the exposure state holding operation is performed. The optimum exposure state is maintained, and there is an effect that an image as intended by the photographer can be provided.

According to the invention of claim 5 in the present application, when the zoom lens is driven in a state where the exposure state controlled by the exposure state holding means is held, the zoom lens is driven. The stored exposure control status is corrected according to the focal length of the lens and the diaphragm state of the diaphragm mechanism, enabling more accurate correction in various shooting situations and maintaining the exposure state even if the focal length of the zoom lens changes. The optimum exposure state at the time of performing the operation is maintained, and there is an effect that an image as intended by the photographer can be provided.

According to the sixth aspect of the present invention, since the correction by the exposure correction means is performed by the gain control of the automatic gain control circuit, the exposure control state according to the focal length of the zoom lens can be achieved. It is corrected, and it is possible to make fine corrections in various shooting situations,
Even if the focal length of the zoom lens changes, the optimum exposure state at the time of performing the exposure state holding operation is maintained, and there is an effect that an image as intended by the photographer can be provided.

According to the invention of claim 7 in the present application, since the correction by the exposure correction means is performed by controlling the accumulation time of the image pickup device, the exposure control state according to the focal length of the zoom lens is performed. Is corrected, the range that can be corrected becomes wider, and the optimum exposure state at the time of performing the exposure state holding operation is maintained even if the focal length of the zoom lens changes.
This has the effect of providing the image as intended by the photographer.

According to the invention of claim 8 in the present application, since the correction in the exposure correction means is performed by the gain control of the automatic gain control means and the storage time control of the signal of the image pickup element, the zoom lens The exposure control state that changes according to the focal length of the camera is corrected, the range that can be corrected is widened, and finer correction is possible, and the exposure state holding operation is performed even when the focal length of the zoom lens changes in various shooting situations. The optimum exposure state at the time of performing is maintained, and there is an effect that a video image as intended by the photographer can be provided.

Further, according to the invention described in each claim of the present application, there is provided the AE lock means capable of maintaining the optimum exposure state at the time of performing the AE lock operation even if the focal length of the zoom lens is changed. Even if the AE lock means is used, the focal length can be changed to perform shooting in accordance with the angle of view intended by the photographer, and it is possible to provide an optimal image according to various subjects and shooting conditions. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional example.

FIG. 5 is a diagram showing a characteristic of an F value with respect to a focal length of a zoom lens.

FIG. 6 is a diagram showing a change in brightness with respect to a focal length of a zoom lens.

FIG. 7 is a diagram showing an example of a look-up table of the F-number correction means of the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Object imaging zoom lens 2 Aperture mechanism 3 Image sensor 4 Zoom encoder (focal length detection means) 5 Aperture echoda (aperture state detection means) 6 IG meter 7 Image sensor control circuit 8 Sample hold circuit 9 Auto gain control (AGC) Circuit 10 Camera signal processing circuit 11 Video tape recorder 12 Electronic viewfinder for monitor 13 Exposure detection circuit 14 Trigger key 15 Exposure control circuit (means) 16 of the first embodiment 16 Iris drive circuit 17 Exposure compensation circuit of the first embodiment (Means) 18 Camera Signal Processing Circuit (Digital Signal Processing Circuit) 19 Microcomputer 20 Exposure Control Circuit (Means) 21 of Third Embodiment 21 Exposure Compensating Means (Means) 22 of Third Embodiment Exposure Control Circuit of Conventional Example

Claims (8)

[Claims] 1. A zoom lens, which is a lens group for imaging a subject and whose focal length is variable, an image sensor for photoelectrically converting light incident by the zoom lens, and a signal photoelectrically converted by the image sensor. Signal processing means for generating a video signal to be a television signal, exposure control means for controlling the exposure state according to the video signal, exposure state holding means for holding the exposure state of the exposure control means, A focal length detecting means for detecting the focal length of the zoom lens, and an exposure correcting means for correcting the exposure state of the exposure control means held by the exposure state holding means in response to a detection signal of the focal length detecting means. An imaging device comprising: 2. The signal processing means according to claim 1, wherein the signal processing means includes an auto gain control means for electrically amplifying a video signal, and the exposure correction means performs the auto operation according to a change in a focal length of the zoom lens. An imaging apparatus configured to correct an exposure control state by controlling a gain of a gain control. 3. The exposure control means according to claim 1, wherein the exposure control means has an electronic shutter function for controlling a storage time of the image pickup device, and the exposure correction means operates in accordance with a change in a focal length of the zoom lens. An image pickup apparatus configured to correct an exposure control state by controlling a storage time of an image pickup element. 4. The electronic shutter function according to claim 1, wherein the signal processing unit has an auto gain control unit that electrically amplifies a video signal, and the exposure control unit controls an accumulation time of the image sensor. The exposure correction means is configured to correct the exposure control state by controlling the gain of the automatic gain control and the storage time of the image sensor according to the change of the focal length of the zoom lens. An imaging device characterized in that 5. A zoom lens, which is a lens group for imaging a subject and whose focal length is variable, an image sensor for photoelectrically converting light incident by the zoom lens, and a diaphragm for limiting the amount of light incident on the image sensor. Means, a diaphragm state detecting means for detecting a diaphragm state of the diaphragm means, a signal processing means for processing a signal photoelectrically converted by the image sensor to generate a video signal to be a television signal, and the video signal Exposure control means for controlling the exposure state according to the exposure control means, exposure state holding means for holding the exposure state of the exposure control means, focal length detection means for detecting the focal length of the zoom lens, and detection by the focal length detection means And an exposure correction means for correcting the exposure state of the exposure control means according to the signal and the output signal of the aperture state detection means. Location. 6. The signal processing means according to claim 5, further comprising an auto gain control means for electrically amplifying a video signal, and the exposure correction means according to a change in a focal length of the zoom lens. An imaging apparatus configured to correct an exposure control state by controlling a gain of a gain control. 7. The exposure control device according to claim 5, wherein the exposure control device has an electronic shutter function for controlling a storage time of the image sensor, and the exposure correction device operates in accordance with a change in focal length of the zoom lens. An image pickup apparatus configured to correct an exposure control state by controlling a storage time of an image pickup element. 8. The electronic shutter function according to claim 5, wherein the signal processing means has an auto gain control means for electrically amplifying a video signal, and the exposure control means controls an accumulation time of the image sensor. The exposure correction means is configured to correct the exposure control state by controlling the gain of the automatic gain control and the storage time of the image sensor according to the change of the focal length of the zoom lens. An imaging device characterized in that