JPH09186930A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep an optimum exposure state even when a focus of a zoom lens is changed by controlling a transmittivity of a transmittivity variable filter in response to the focus of the zoom lens detected by a long distance detection means. SOLUTION: An exposure change due to an object change is detected from a video signal of a camera signal processing means 16 with an exposure control means of a microcomputerg. Based on a detection signal, exposure control parameters by diaphragm mechanism means 5, an electronic shutter controlling a storage time of an image pickup element 12, an exposure control parameter of an AGC gain of a CSD/AGC means are selected and a control arithmetic step for correction amount for each parameter is decided to conduct exposure control, then a prescribed exposure state is always maintained even when a focus of zoom lens 1 is fluctuated and an F-value is change. On the other hand, in response to the focus of the lens 1 detected by a focus means 4, the transmittivity of the filter 9 is made variable to operate correction amount of a surrounding luminous quantity at each focus of the lens 1. The transmittivity of the filter means 9 is controlled by the correction value to correct reduction in the surrounding luminous quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of imaging devices, and more particularly to the technical field of imaging devices having exposure control means.

[0002]

2. Description of the Related Art The structure and operation of a conventional image pickup apparatus will be described below with reference to the block diagram of FIG.

The structure of the image pickup apparatus shown in FIG. 11 is as follows: 1 is a lens group for forming an image of a subject and has a variable focal length, 2 is a zoom lens drive motor for varying the focal length of the zoom lens 1, 3 is a zoom lens driving means for driving the zoom lens driving motor 2, 4 is a focal length detecting means for detecting the focal length of the zoom lens 1, 5 is a diaphragm mechanism means of a diaphragm blade structure for controlling the amount of incident light, and 6 is A diaphragm mechanism drive motor such as an IG meter for driving the diaphragm mechanism means 7, 7 is a diaphragm mechanism drive means for driving the diaphragm mechanism drive motor 6, and 8 is a diaphragm state detection means for detecting the diaphragm state of the diaphragm mechanism means 5. is there.

Reference numeral 12 is an image pickup element for photoelectrically converting incident light, and 13 is an image pickup element control circuit for controlling the image pickup element 12 to read out a photoelectrically converted signal and for controlling a so-called electronic shutter function for controlling a signal accumulation time. , 14
Is a CDS / AGC means for performing automatic gain control (hereinafter referred to as AGC) for sampling a signal photoelectrically converted by the image sensor 12 and electrically amplifying the signal, 1
Reference numeral 5 is an analog-digital conversion (hereinafter referred to as A / D conversion) means for converting an analog signal output from the CDS / AGC means 14 into a digital signal, and 16 is processing such as gamma correction, color separation, and color difference matrix. After that, a camera signal processing means for adding a synchronizing signal to generate a standard television signal, and a digital-analog conversion 17 for converting an output signal of the camera signal processing means 16 from a digital signal state to an analog signal (hereinafter referred to as D / A conversion). 18) is an electronic viewfinder (hereinafter referred to as EVF) for monitoring the image being photographed, 19 is a telephoto for changing the focal length of the zoom lens 1 according to the photographer's intention,
It is a key input means for inputting a wide trigger signal and a trigger signal for performing an AE lock operation for holding the exposure state.

Reference numeral 21 denotes means for detecting a signal from the key input means 19 to control the focal length of the zoom lens, diaphragm mechanism 5,
The microcomputer is provided with an exposure control means for controlling the exposure by controlling the electronic shutter function of the image sensor 12 and the AGC of the CDS / AGC means 14.

In the image pickup apparatus having the above-mentioned structure, in order to obtain an optimum image by simple photographing in various places and under various conditions, the object is detected from the image signal of the camera signal processing means 16. Of the aperture of the CDS / AGC unit 14 by detecting the change in the brightness of the image pickup device and controlling the storage time of the diaphragm mechanism unit 5 and the image pickup device 12 according to the detection signal in the exposure control unit of the microcomputer 21. The exposure control parameters are selected and the correction amount of each parameter is determined, and control is performed so that stable and optimum exposure is always obtained.

For example, the exposure control means of the microcomputer 21 is a control flowchart shown in FIG. 12 and FIG.
When the control is performed as shown in the program diagram in Fig. 3, shooting under sufficient illuminance such as outdoors (area B shown in Fig. 13)
Then, the AGC gain is fixed to the minimum gain according to the control flowchart of FIG. 12, and the exposure data detection step S12
The control amount of the diaphragm mechanism means 5 corresponding to the signal detected in 1 is obtained in the control value calculation step S127.

When the brightness of the subject becomes dark and the diaphragm state of the diaphragm mechanism means 5 detected by the diaphragm state detection means 8 becomes the released state (area A shown in FIG. 13) and the diaphragm mechanism means 5 cannot control the diaphragm mechanism. Fix the means 5 in the open state,
The control amount of the AGC gain according to the brightness of the subject is calculated in the control value calculation step S125.

The control value of each parameter obtained in this way is output in the control value output step S128, and the control value is updated so that the brightness of the subject is always followed to achieve the optimum exposure state. . As a result, even if the brightness of the subject changes, it is possible to provide 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 optimal, if the brightness of the surrounding 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 conventionally devised. AE
The operation of the lock means is an EVF which is a monitor means by the photographer.
When the exposure state is desired to be held while checking the screen of 18, the trigger signal is detected by the microcomputer 21 by inputting a trigger signal from the AE lock key of the key input means 19, and according to the control flowchart shown in FIG. Hold the correction amount of each exposure control parameter of the aperture mechanism unit 5, the electronic shutter that controls the accumulation time of the image sensor 12, the AGC gain of the CDS / AGC circuit 14 when the trigger signal is input in the control value calculation step S129. Done in.

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 control means, for example, in the case of photographing a person against backlight, the bright part of the background People's exposure is affected by, and the exposure state of the person becomes darker, so-called black shadow,
Conversely, in a shooting situation where the exposure state of the person becomes too bright in the case of over-forward light, such as when shooting a person illuminated by a spotlight light, so-called overexposure,
By changing the focal length of the zoom lens 1 to zoom up the main subject, the influence of the brightness of the peripheral subject is eliminated, and the AE lock operation is performed when the exposure state of the main subject is optimal. There is a shooting method in which the focal length is returned and shooting is started in accordance with the image frame intended by the photographer.

[0013]

However, even though the AE lock means is used as described above, the amount of incident light from the zoom lens 1 is constant and the diaphragm mechanism means 5 for limiting the amount of incident light is in a constant state. However, depending on the zoom lens, the F value of the lens changes depending on the focal length, so the amount of light incident on the image sensor surface of the image sensor 12 fluctuates, and even if the AE lock operation is performed in an optimum state, the zoom lens When the focal length is changed, it changes from the exposure state at the time of performing the AE lock operation, and there is a problem that the optimum exposure state cannot be maintained.

Further, since the image forming lens is generally designed in consideration of the balance between compactness and performance such as aberration, not only the lens sufficiently satisfying the performance is required. Among them, the aperture efficiency is designed in balance with compactness, and it is made small within a range that does not hinder practical use, so that light that enters obliquely causes vignetting and the amount of light that enters the image sensor surface of the image sensor 12. However, there is a problem of so-called peripheral light amount drop, in which the light amount of the peripheral portion is lower than the light amount of the central portion of the image sensor. Further, since the aperture efficiency is influenced by the focal length, the peripheral light amount drop also changes in the zoom lens when the focal length changes. Therefore, even with a normal automatic exposure control means that does not perform the AE lock operation, the average exposure state of the entire screen is controlled to be appropriate, but shading occurs due to peripheral light drop, and a subject of uniform brightness is photographed. Even if the central part is overexposed and the peripheral part is underexposed, the shading condition changes when the focal length of the zoom lens 1 is changed. There is a problem that images cannot be obtained.

An object of the present invention is to provide an image pickup apparatus capable of maintaining an optimum exposure state even if the focal length of a zoom lens is changed.

[0016]

For this reason, the image pickup apparatus according to the present invention comprises: (1) a zoom lens which is a lens group for forming an image of a subject and has a variable focal length, and a light incident from the zoom lens. An image pickup device for conversion, a transmittance variable filter unit provided on the optical path of the zoom lens for changing the transmittance of light incident on the image pickup device, and a television which processes a signal photoelectrically converted by the image pickup device. An image pickup apparatus comprising: a signal processing unit that generates a video signal that is a John signal; a focal length detecting unit that detects the focal length of the zoom lens; and a controlling unit, wherein the controlling unit detects the focal length. An image pickup apparatus, wherein the light transmittance of the transmittance variable filter means is controlled according to the focal length of the zoom lens detected by the means.

(2) A zoom lens which is a lens group for forming an image of a subject and whose focal length is variable, an image pickup element for photoelectrically converting light incident from the zoom lens, and the above-mentioned optical path provided on the zoom lens. Transmittance variable filter means for changing the transmittance of light incident on the image sensor, 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 zoom lens Focal length detection means for detecting the focal length of
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, and F value correction means for correcting the exposure state according to the focal length of the zoom lens. In the case where the exposure state holding means is performing a holding operation, the F-value correction means performs the transmission according to the focal length of the zoom lens detected by the focal length detection means. An image pickup apparatus, characterized in that the exposure state is corrected by controlling the light transmittance of the variable rate filter means.

(3) The signal processing means has an automatic gain control means for electrically amplifying a video signal, and performs an operation of holding the exposure state controlled by the exposure control means by the exposure state holding means. In this case, the F value correcting means controls the light transmittance of the transmittance variable filter means and the gain of the automatic gain control means in accordance with the focal length of the zoom lens detected by the focal length detecting means. The image pickup apparatus according to (2) above, wherein the image pickup apparatus corrects the exposure state.

By the above, the above-mentioned object is achieved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image pickup apparatus according to the present invention is provided with a means for correcting a change in F-number due to a change in focal length of a zoom lens and a change in exposure state due to a drop in peripheral light amount. It is intended to achieve the above object.

With the above arrangement, even if the focal length of the zoom lens is changed, it becomes possible to control the exposure so that the optimum exposure state can be maintained. By changing the focal length, the image frame intended by the photographer can be obtained. It is possible to provide the optimum video according to various subjects and shooting conditions.

[0022]

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

(First Embodiment) FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. The parts denoted by the same reference numerals 1 to 8 and 12 to 19 as in the conventional example have the same functions as in the conventional example, and the process of processing the video signal is the same.

In this embodiment, the transmittance variable filter means 9 for changing the light transmittance of incident light and the transmittance variable filter driving means 1 for driving the transmittance variable filter means 9 are used.
0, the transmittance detecting means 11 for detecting the light transmittance of the variable transmittance filter means 9 is added, and the exposure control means for correcting the exposure state due to the peripheral light amount drop which changes according to the focal length of the zoom lens is added. The microcomputer 20 provided with the means is a characteristic configuration of this embodiment.

Next, the operation of the exposure control means, which is a feature of this embodiment, will be described with reference to the control flow chart shown in FIG.

Generally, in a zoom lens, the F value increases as the focal length becomes closer to the telephoto side, and even if a constant amount of light enters the zoom lens 1, the amount of light incident on the image pickup device surface of the image pickup device 12 decreases toward the telephoto side. It will be. However, as in the conventional case, the exposure control means of the microcomputer detects the change in exposure due to the change of the subject from the video signal of the camera signal processing means 16, and based on the detected signal, the accumulation time of the diaphragm mechanism means 5 and the image pickup device 12 is determined. The electronic shutter to be controlled, the selection of the exposure control parameter of the AGC gain of the CSD / AGC means 14, and the correction amount of each parameter are determined in the control value calculation steps S104 and S106 according to the program diagram shown in FIG. By performing the above, it is possible to always maintain a constant exposure state even if the focal length of the zoom lens 1 changes and the F value changes.

However, although the exposure control means alone controls the exposure state in which the entire screen is averaged,
As shown in (a) of FIG. 3, the amount of light incident on the image sensor surface decreases toward the peripheral portion, and shading occurs due to the fall of peripheral light amount, and as shown in (b) of FIG. 3, a subject having uniform brightness is photographed. Also, the exposed state of the center part is over-exposed,
It is not possible to prevent the phenomenon that the exposed state of the peripheral part becomes underexposed. Furthermore, the phenomenon also changes depending on the focal length of the zoom lens 1. The peripheral light amount drop is corrected in the peripheral light amount correction step S108.

In the peripheral light amount correction step S108, the light transmittance of the variable transmittance filter unit 9 is varied according to the focal length of the zoom lens 1 detected by the focal length detecting unit 4 to change the light transmittance at each focal length of the zoom lens 1. A correction amount for correcting the peripheral light drop is calculated. The variable transmittance filter means 9 is divided into a plurality of areas as shown in FIG. 4, and the light transmittance can be controlled for each area. Here, an example in which it is divided into four is shown.

In step S108 for correcting the amount of peripheral light, FIG.
As shown in, a look-up table (hereinafter referred to as LUT) in which the light transmittance data of each area of the variable transmittance filter unit 9 for correcting the peripheral light amount drop according to each focal length of the zoom lens 1 is set in advance is shown. Compensation data is selected from the LUT according to the focal length of the zoom lens 1 detected by the focal length detection unit 4, and the light transmittance of the transmittance variable filter unit 9 is controlled by the selected correction value. The peripheral light falloff is corrected.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

The block diagram showing the configuration of the second embodiment of the present invention is similar to the block diagram showing the configuration of the first embodiment shown in FIG. 1, and reference is made to FIG. The second embodiment differs from the internal processing of the microcomputer 20 and is provided with an exposure control means in which an F value correction means for correcting the change in exposure due to the change in F value due to the focal length of the zoom lens is added.

Generally, in zooming, the F value increases as the focal length becomes closer to the telephoto side, and even if a constant amount of light enters the zoom lens 1, the amount of light incident on the image pickup device surface of the image pickup device 12 decreases toward the telephoto side. become.

For example, F with respect to the focal length of the zoom lens
In the case where the value characteristic is as shown in FIG. 6, assuming that the amount of light incident on the image sensor surface of the image sensor 12 at the wide end is 100%, the amount of light incident on the image sensor 12 with respect to the focal length is as shown in FIG. Changes to. As shown in FIG. 6, when the F value at the wide end is F1.4 and the F value at the tele end is F2.8, the light amount on the image pickup element surface at the tele end is about ¼ of that at the wide end. Further, the zoom lens 1 when the aperture state of the aperture mechanism unit 5 is fixed at F2 by the AE lock unit
The change in the F value with respect to the focal length is as shown in FIG. 6, and the amount of light incident on the image sensor surface of the image sensor 12 at that time is as shown in FIG. As described above, the change of the F value with respect to the focal length also differs depending on the diaphragm state of the diaphragm mechanism means 5.

The F value correcting means provided in the microcomputer 20 of this embodiment uses the variable transmittance filter means 9 for the change of the light amount of the image pickup element surface with respect to the change of the F value with respect to the focal length of the zoom lens 1 described above. The correction is performed, and the light transmittance of the transmittance variable filter unit 9 is changed and corrected so that the light incident on the image pickup element surface becomes constant even if the focal length changes.

For this reason, the F value correcting means is provided with a look-up table (hereinafter referred to as LUT) which stores correction data. The data of this LUT is a correction amount necessary for keeping the amount of light incident on the image sensor surface of the image sensor 12 constant, and as described above, the correction amount varies depending on the diaphragm state of the diaphragm mechanism means 5, so that it depends on the diaphragm state. It has multiple tables.

FIG. 8 shows a typical table of the LUT of the F value correction means in the case of the zoom lens having the characteristics shown in FIG.

Next, the operation of the AE lock means, which is a feature of this embodiment, will be described with reference to the control flowchart of FIG.

Normally, as in the conventional case, the exposure control means of the microcomputer 20 detects the change in exposure due to the change of the subject from the video signal of the camera signal processing means 16,
A diaphragm mechanism means 5, an electronic shutter for controlling the storage time of the image sensor 12, and a CSD / AGC means 1 based on the detection signal.
The selection of the exposure control parameter of AGC gain of No. 4 and the correction amount of each parameter are determined in the control value calculation steps S205 and S207 according to the program diagram shown in FIG. 13, and the control is performed so that the exposure is always stable and optimal.
At this time, the light transmittance of the variable transmittance filter means 9 is fixed at a predetermined transmittance. Here, instead of being divided into a plurality of areas as in the first embodiment, it is controlled with the same light transmittance over the entire area. For example, the light transmittance is fixed at 25%. The variable transmittance filter means 9
The light transmittance of is detected by the transmittance detecting means, and is controlled by the microcomputer 20 so that the light transmittance becomes constant.

Next, when the photographer wants to maintain the proper exposure state, the AE lock operation is performed by inputting the trigger signal of the AE lock request from the key input means 19. When the trigger signal is detected by the microcomputer 20, the key information is discriminated in the AE lock key discrimination step S202, and in the case of the AE lock operation request, in the control value calculation step S210, the aperture mechanism means 5, the electronic shutter, the AGC gain at that time. It is carried out by holding the control value of each exposure control parameter.

At this time, the diaphragm state of the diaphragm mechanism means 5 at the time of the AE lock operation is detected by the diaphragm state detecting means 8, and the focal length of the zoom lens 1 is detected by the focal length detecting means 4 to obtain the F value correction data. Selection step S211
L corresponding to the diaphragm state of the diaphragm mechanism means 5 detected in
The UT is selected, and the F-number correction data corresponding to the detected focal length of the zoom lens 1 is selected from the selected LUT and used as reference data.

Next, when the focal length of the zoom lens 1 changes, the focal length at that time is detected and L selected when the reference data is calculated in the F value correction data selection step S211.
The F value correction data corresponding to the focal length is selected from the UT. In the F value correction amount calculation step S214, the selected F value correction data and the reference data are compared, and the amount of light on the image sensor surface of the image sensor 12 due to the change of the focal length of the zoom lens and the change of the F value is detected. Find the amount of correction needed to keep the change constant. For example, the diaphragm mechanism means F1.4
When the AE lock operation is performed in this state, the selected LUT is the LUT1 shown in FIG. 8, and in the state where the focal length of the zoom lens 1 is the LUT1 shown in FIG. As +6 dB
Is selected. When the focal length changes to the state of LUT1 shown in FIG. 8, +12 dB is selected as the F value correction data, and in the F value correction amount calculation step S214, the F value correction amount = (current F value correction data−reference data). Is calculated, and a correction amount required to keep the amount of incident light on the image sensor surface of the image sensor 12 during the AE lock operation constant + 6d
B is required. Based on this correction amount, it is converted into data for controlling the light transmittance of the variable transmittance filter means 9 in the transmittance calculation step S215. Here, the F value correction amount is +6
Since the value is dB, if the light transmittance of the variable transmittance filter means 9 in the automatic exposure control state before the AE lock operation is fixed at 25%, the corrected light transmittance of the variable transmittance filter means 9 is 50%. The amount of light incident on the surface of the image sensor is kept constant by controlling the above.

Conversely, when the focal length of the zoom lens 1 changes to the state of the LUT 1 shown in FIG. 8, 0 dB is selected as the F value correction data, and the necessary correction amount is -6d.
B, and the light transmittance of the variable transmittance filter means 9 is 1
It is corrected by controlling to 2.5%.

If the aperture state of the aperture mechanism means 5 during the AE lock operation is F2, the correction value may be calculated from the data table of LUT2 shown in FIG.

As described above, a necessary correction amount is provided in advance according to the diaphragm state of the diaphragm mechanism means 5 and the focal length of the zoom lens 1 during the AE lock operation, and the transmittance variable filter means 9 of the variable transmittance filter means 9 corresponds to the change of the focal length. Image sensor 1 by controlling light transmittance
The correction is performed so that the amount of light incident on the image pickup element surface of No. 2 becomes constant.

(Third Embodiment) The third embodiment of the present invention has the same configuration as that of the first embodiment except that the internal processing of the microcomputer 20 is different. This will be described with reference to FIG.

In the second embodiment described above, only the variable transmittance filter means 9 is used, and the light transmittance of the variable transmittance filter means 9 is controlled according to the change of the focal length of the zoom lens 1, and the image pickup device 12 is controlled. Although the configuration has been described in which correction is performed so that only the amount of light incident on the image pickup element surface becomes constant, the AE lock operation is sufficient even if the focal length of the zoom lens 1 is in any state only with the variable transmittance filter means 9. To F
In order to perform the value correction, it is necessary to set the light transmittance of the variable transmittance filter means 9 to be low in the automatic exposure control state where the AE lock operation is not performed.

For example, when the light transmittance of the variable transmittance filter means 9 is set to 100% in the automatic exposure control state, when the AE lock is set on the tele side and the focal length is changed to the wide side, the image pickup element surface is displayed. Since the amount of light is increased, it is possible to correct it by lowering the light transmittance of the variable transmittance filter means 9. However, when AE lock is performed on the wide side and the focal length is changed to the tele side, the image is captured. It is necessary to further increase the light transmittance of the variable transmittance filter because the amount of light on the element surface is reduced, but it is assumed that the variable transmittance of the variable transmittance filter means 9 before the AE lock operation is set to 100%. It is impossible to correct. Therefore the second
In the second embodiment, the above-mentioned problem is compensated by setting the light transmittance of the variable transmittance filter means 9 in the automatic exposure control state to 25%. However, there is a problem that the S / N ratio is deteriorated when the illuminance is low by using the transmittance variable filter means 9 with the transmittance lowered during normal automatic exposure control.

In the third embodiment of the present invention, the zoom lens 1
The variable transmittance filter means 9 according to the change of the focal length of the
Of the CDS / AGC means 14 and the AGC gain of the CDS / AGC means 14 are controlled to perform correction so that the amount of light incident on the image sensor surface of the image sensor 12 becomes constant.

Next, the operation of the F value correcting means of the third embodiment will be described.

The exposure control of the third embodiment is performed according to the control flow chart shown in FIG. 10, but the automatic exposure control means sets the light transmittance of the variable transmittance filter means 9 to 100.
The only difference is that it is fixed to%, and other processing is the second
This is the same as the embodiment. Also, the F value correction means during the AE lock operation is the same as the second embodiment in the processing up to the F value correction amount calculation step S314, and only the transmittance / AGC gain calculation step SA315 is different.

In the transmittance / AGC gain calculation step S315 of the third embodiment, the F value correction amount calculation step S31 is performed.
When the correction amount calculated in step 4 is a positive gain correction amount, the AG of the CDS / AGC means 14 according to the correction amount is added.
If the correction amount is a negative gain correction amount, it is converted into the light transmittance control data of the variable transmittance filter unit 9 according to the correction amount.

For example, when the diaphragm mechanism means is F1.4, A
When the E-lock operation is performed, the selected LUT is the LUT1 shown in FIG. 8. In the state where the focal length of the zoom lens 1 is the LUT1 shown in FIG. 8, +6 dB is selected in the F value correction data selection step S311. Used as reference data. When the focal length changes to the state of LUT1 shown in FIG. 8, +12 dB is selected as the F value correction data, the F value correction amount is calculated in the F value correction amount calculation step S314, and the image sensor 12 during the AE lock operation is selected. Correction amount required to keep the amount of incident light on the image sensor surface of +6 dB
Is required. Since the correction amount in this case is the correction of the positive gain, the CSD / AGC means 14 is adjusted according to the correction amount.
The AGC gain is converted into control data for increasing the AGC gain setting value at the time of the AE lock operation by 6 dB.

Conversely, when the focal length of the zoom lens 1 changes to the state of the LUT 1 shown in FIG. 8, 0 dB is selected as the F value correction data, and the necessary correction amount is -6d.
Since this is B, which is a correction amount of a negative gain, it is converted into data for controlling the light transmittance of the variable transmittance filter router 9 according to this correction amount. Here, since the light transmittance of the variable transmittance filter means 9 in the automatic exposure control state is fixed to 100%, the light transmittance of the variable transmittance filter means 9 after correction is controlled to 50% to thereby obtain an image sensor. The amount of light incident on the surface is kept constant.

As described above, in the third embodiment, the parameter to be corrected according to the correction amount of the F value correction is the light transmittance of the variable transmittance filter means 9 or the A of the CDS / AGC means.
One of the GC gains is selected and correction is performed so that the amount of light incident on the image sensor surface of the image sensor 12 becomes constant.

[0055]

As described above, according to the first invention of the present application, the light transmittance of the variable transmittance filter means is controlled according to the focal length of the zoom lens detected by the focal length detecting means. As a result, it is possible to correct the peripheral light amount drop that changes depending on the focal length, and it is possible to provide an image pickup apparatus that can obtain an image in which an optimal exposure state is always maintained.

According to the second invention of the present application,
When the holding operation of holding the exposure state controlled by the exposure control means by the exposure state holding means is performed, the light transmittance of the transmittance variable filter means according to the focal length of the zoom lens detected by the focal length detection means. It is possible to correct a change in the amount of light incident on the image pickup element surface due to a change in the F-number of the zoom lens, and it is possible to adjust the optimum value at the time of performing the exposure state maintaining operation even if the focal length of the zoom lens changes. It is possible to provide an effect that it is possible to provide an image pickup apparatus in which an exposed state is maintained and an image as intended by a photographer can be obtained.

According to the third invention of the present application,
When the holding operation of holding the exposure state controlled by the exposure control means by the exposure state holding means is performed, the light transmittance of the transmittance variable filter means according to the focal length of the zoom lens detected by the focal length detection means. And CDS / AGC means A
By controlling the GC gain, it becomes possible to correct the conversion of the amount of light incident on the image pickup element surface due to the F value variation of the zoom lens without deteriorating the S / N ratio of the image.
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 it is possible to provide an image pickup apparatus that can obtain an image as intended by the photographer.

[Brief description of the drawings]

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

FIG. 2 is a control flowchart of the exposure control means of the first embodiment.

FIG. 3 is a conceptual diagram for explaining a peripheral light drop phenomenon.

FIG. 4 is a transmittance variable filter means according to the first embodiment.

FIG. 5 is a lookup table according to the first embodiment of the present invention.

FIG. 6 is a diagram showing characteristics of an F value with respect to a focal length of a zoom lens.

FIG. 7 is a diagram showing a change in brightness with respect to a focal length of a zoom lens.

FIG. 8 is a lookup table according to second and third embodiments of the present invention.

FIG. 9 is a control flow chart of the exposure control means of the second embodiment.

FIG. 10 is a control flow chart of the exposure control means of the third embodiment.

FIG. 11 is a block diagram showing a configuration of a conventional example.

FIG. 12 is a control flowchart of an exposure control unit of a conventional example.

FIG. 13 is a program diagram of automatic exposure control means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Object imaging zoom lens 2 Zoom lens drive motor 3 Zoom motor drive means 4 Focal length detection means 5 Aperture mechanism means 6 Aperture mechanism drive motor 7 Aperture mechanism drive means 8 Aperture state detection means 9 Transmittance variable filter means 10 Transmittance Variable filter driving means 11 Transmittance detecting means 12 Image sensor 13 Image sensor driving means 14 CDS / AGC means 15 Analog-digital converting means 16 Camera signal processing means 17 Digital-analog converting means 18 Monitor electronic viewfinder 19 Key input means 20 Microcomputer of Embodiment of Present Invention 21 Microcomputer of Conventional Example

Claims (3)

[Claims] 1. A zoom lens, which is a lens group for imaging a subject and has a variable focal length, an image pickup device for photoelectrically converting light incident from the zoom lens, and the image pickup provided on an optical path of the zoom lens. A variable transmittance filter means for changing the transmittance of light incident on the element, 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 a zoom lens of the zoom lens. An image pickup apparatus comprising: a focal length detecting means for detecting a focal length; and a controlling means, wherein the controlling means has the variable transmittance filter according to the focal length of the zoom lens detected by the focal length detecting means. An image pickup device, characterized in that the light transmittance of the means is controlled. 2. A zoom lens, which is a lens group for imaging a subject and has a variable focal length, an image pickup device for photoelectrically converting light incident from the zoom lens, and the image pickup provided on the optical path of the zoom lens. A variable transmittance filter means for changing the transmittance of light incident on the element, 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 a zoom lens of the zoom lens. Focal length detection means for detecting the focal length, exposure control means for controlling the exposure state according to the video signal,
An image pickup apparatus comprising: an exposure state holding means for holding the exposure state of the exposure control means; and an F value correction means for correcting the exposure state according to the focal length of the zoom lens, wherein the exposure state holding means holds the exposure state. If you are doing
An image pickup apparatus characterized in that the F value correcting means controls the light transmittance of the transmittance variable filter means according to the focal length of the zoom lens detected by the focal length detecting means to correct the exposure state. . 3. The signal processing means has an automatic gain control means for electrically amplifying a video signal, and performs an operation of holding the exposure state controlled by the exposure control means by the exposure state holding means. In this case, the F value correcting means controls the light transmittance of the transmittance variable filter means and the gain of the automatic gain control means according to the focal length of the zoom lens detected by the focal length detecting means. The image pickup apparatus according to claim 2, wherein the exposure state is corrected.