JPH1184459A - Exposure controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of diffraction at a diaphragm position (intermediate diaphragm) where the greater part of the aperture part of a diaphragm is made so as to be shut with a neutral density(ND) filter in an exposure controller in which the ND filter is fitted to the diaphragm. SOLUTION: This controller is equipped with an optical system 2 provided with a lens and a diaphragm 1 and in which an ND filter is fitted to a diaphragm blade constituting the diaphragm 1 to project it to the aperture part of the diaphragm 1, a driving means 7 adjusting the diaphragm position of the diaphragm 1, a detection means 9 detecting the diaphragm position of the diaphragm 1, an image pickup means 12 converting light passing through the diaphragm 1 to an electric signal and a control means 11 changing the diaphragm position of the diaphragm 1 by the driving means 7 in response to the output level of the image pickup means 12 while referring to the detected result of the detection means 9 and executing such control that the diaphragm position of the diaphragm 1 is fixed without the range when the output level of the image pickup means 12 is the level that the diaphragm position of the diaphragm 1 should be fixed within the range that diffraction occurs in the intermediate diaphragm and the output level of the image pickup means 12 is electrically corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control apparatus for controlling the amount of incident light by opening and closing an aperture, and more particularly to an exposure control apparatus in which an optical filter is attached to an aperture blade so as to prevent occurrence of diffraction. .

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional configuration of an exposure control device used for controlling the amount of light incident on a solid-state imaging device (for example, a CCD or the like) in a video camera, an electronic still camera, or the like. It is as follows. Light from a subject enters a lens block 2 including various lenses and a stop (aperture stop) 1. As shown in FIG. 4, for example, the diaphragm 1 has two flat plate-like diaphragm blades 1a and 1b which are arranged facing each other with their positions in the thickness direction shifted by substantially the thickness. When the wings 1a and 1b are displaced toward or away from each other in the direction of the plate surface, the size of the opening 1c between them changes (that is, the aperture position changes).

Light passing through the lens block 2 is transmitted to a CCD 3
And is converted into an electric signal. This electrical signal
The signal is supplied to a signal processing unit 4 for generating a video signal, and is also sent to a detection circuit 5 to detect an amplitude level.

The microcomputer 6 controls each section of the exposure control device, and keeps the input level to the signal processing section 4 constant based on the detection output of the detection circuit 5 (ie, based on the amount of light incident on the CCD 3). Calculate the target aperture position to keep. Then, after the aperture position of the aperture 1 is changed to this target position by the aperture drive device 7, the aperture drive device 7 is stopped to fix the aperture position. In this way, the amount of light incident on the CCD 3 is controlled.

In recent years, the aperture of the lens of the lens block 2 has become smaller as the area of the image pickup surface of the CCD 3 has become smaller. Therefore, when the amount of incident light greatly increases, the aperture 1 is closed accordingly. (Hereinafter, such a stop position is referred to as “small stop”), the light passing through the stop 1 is diffracted by fixing the stop position in a state where the area of the opening of the stop 1 is extremely small. When such diffraction occurs, the imaging performance of the lens is reduced, and the image quality is deteriorated.

In order to prevent the occurrence of diffraction in such a small aperture, conventionally, as shown in FIG. 4, for example, an ND filter having a fixed density is applied to one of the aperture leaves 1a and 1b. The (neutral filter) 8 is mounted so as to protrude from the opening 1 c of the diaphragm 1.
As a result, when the amount of incident light greatly increases, even if the diaphragm 1 is not closed to a position where diffraction occurs, light passes through the ND filter 8 and the amount of incident light to the CCD 3 decreases.

[0007]

However, when the ND filter is attached to the aperture as described above, diffraction can be prevented from occurring at the small aperture, but diffraction does not occur at the aperture without the ND filter. At the stop position, diffraction occurs newly.

The stop position is a stop position at which the ND filter 8 blocks most of the opening portion 1c as shown in FIG. 5 (hereinafter, such a stop position is called an "intermediate stop"). In the intermediate stop, when the stop position is fixed in a state where the area of the portion not closed by the ND filter 8 (the gap between the ND filter 8 and the stop blade 1b) is extremely small, the light passing through this portion is diffracted. Will happen. As a result, in the intermediate stop, the image forming performance of the lens is also lowered, and the image quality is deteriorated. FIG. 6 shows an aperture position and an MTF (Modula) which is an index of the imaging performance of the lens.
This shows an example of the relationship with the value of the MTF in the range A where the diffraction occurs at the intermediate aperture, where the MTF value is below the allowable level L for preventing the image quality from deteriorating. ing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide an exposure control apparatus in which an optical filter such as an ND filter is attached to an aperture so as to prevent diffraction at an intermediate aperture. It is assumed that.

[0010]

An exposure control device according to the present invention has a lens and a diaphragm, and an optical filter in which an optical filter is attached to a diaphragm blade constituting the diaphragm so as to protrude from an opening of the diaphragm. System, driving means for adjusting the diaphragm position of the diaphragm, detecting means for detecting the diaphragm position of the diaphragm, and control means for changing the diaphragm position of the diaphragm with this driving means while referring to the detection result of the detecting means. Control means for controlling the aperture position of the aperture so as not to be fixed within a range in which diffraction occurs in light passing through a portion of the aperture of the aperture not blocked by the optical filter (that is, in a range where diffraction occurs in the intermediate aperture). It is characterized by having.

According to this exposure control device, control is performed so that the stop position of the stop is not fixed within a range where diffraction occurs in the intermediate stop. In other words, the range in which diffraction occurs in the intermediate stop is a prohibited area where fixing of the stop position is prohibited. This prevents diffraction at the intermediate stop.

Next, an exposure control device according to the present invention has an optical system having a lens and a diaphragm, and an optical system in which an optical filter is attached to a diaphragm blade forming the diaphragm so as to protrude from an opening of the diaphragm. Driving means for changing the aperture position of the aperture, detection means for detecting the aperture position of the aperture, imaging means for converting light passing through the aperture to an electric signal, and referring to the detection result of this detection means, Control means for changing the diaphragm position of the diaphragm by the driving means in accordance with the output level of the imaging means, wherein the output level of the imaging means is a level at which the diaphragm position of the diaphragm should be fixed within the above-described prohibited area. At this time, a control means for controlling the aperture position to be fixed outside the prohibited area and electrically correcting the output level of the imaging means is provided.

According to this exposure control device, when the output level of the imaging means is a level at which the aperture position of the aperture should be fixed in the prohibited area, the aperture position is fixed outside the prohibited area and the output level of the imaging means is reduced. Control for electrically correcting is performed. That is, at this time, the exposure is controlled by electrically correcting the signal level instead of opening and closing the aperture. As a result, the occurrence of diffraction at the intermediate stop is prevented, and continuous execution of exposure control is ensured.

[0014]

FIG. 1 shows an example of the configuration of an exposure control apparatus according to the present invention. The same parts as those in FIG. 3 are denoted by the same reference numerals, and redundant description will be omitted. In the same manner as shown in FIG.
Filter is installed.

As a difference from the exposure control device of FIG. 3, the exposure control device is provided with an aperture position detection device 9 for detecting the aperture position of the aperture 1. Also, a ROM of a microcomputer 10 for controlling each part of the device.
In the stop position of the stop 1, data in a range (range A in FIG. 6) of a position where diffraction occurs at the intermediate stop (for example, data obtained by actually measuring this range) is used as data indicating a prohibited area. It is stored in advance.

An operation example of the exposure control device will be described.
It is as follows. The microcomputer 10 calculates a target aperture position for keeping the input level to the signal processing unit 4 constant based on the detection output of the detection circuit 5, similarly to the microcomputer 6 of FIG. When the calculated target position is outside the prohibited area stored in the ROM, the aperture position of the aperture 1 is changed to the target position by the aperture driving device 7 as in the microcomputer 6 in FIG. After that, the aperture driving device 7 is stopped, and the aperture position is fixed at the target position.

On the other hand, the calculated target position is stored in the ROM
If the stop position is within the prohibited area stored in the stop position, the stop driving device 7 refers to the detection result of the stop position
Is changed toward the target position, and when the stop reaches just before the prohibited area, the stop driving device 7 is stopped to fix the stop position. As described above, within the range of the position where diffraction occurs at the intermediate stop, control is performed so that the stop position of the stop 1 is not fixed, so that the occurrence of diffraction at the intermediate stop is prevented.

Instead of fixing the aperture position immediately before the prohibited area as described above, the aperture position continues to be changed even after entering the prohibited area and reaching the target position. May be stopped to fix the aperture position. This is particularly desirable when the target position is closer to the stop position immediately after passing through the prohibited area than to the stop position immediately before the prohibited area.

Next, FIG. 2 shows another example of the configuration of the exposure control apparatus according to the present invention. The same parts as those in FIGS. 1 and 3 are denoted by the same reference numerals, and redundant description is omitted. I do. An ND filter is also attached to the aperture 1 of the exposure control device, and data indicating a prohibited area is also stored in the ROM of the microcomputer 11 that controls each part of the exposure control device.

The exposure control device includes a CCD 12 having an electronic shutter function and a signal processing unit 4 from the CCD 12.
And a variable gain amplifier 13 for amplifying the signal supplied to the power supply. (However, even in the exposure control device of FIG. 1, C
CD3 has an electronic shutter function, CCD3
An amplifier for amplifying the signal supplied to the signal processing unit 4 may be provided. )

An operation example of the exposure control device will be described.
It is as follows. The microcomputer 11 calculates a target aperture position for keeping the input level to the signal processing unit 4 constant based on the detection output of the detection circuit 5, similarly to the microcomputer 6 in FIG. When the calculated target position is outside the prohibited area stored in the ROM, the aperture position of the aperture 1 is changed to the target position by the aperture driving device 7 as in the microcomputer 6 in FIG. After that, the aperture driving device 7 is stopped, and the aperture position is fixed at the target position.

On the other hand, the calculated target position is stored in the ROM
When the microcomputer 11 is in the prohibited area, the microcomputer 11 changes the aperture position of the aperture 1 toward the target position by the aperture driving device 7 while referring to the detection result of the aperture position detection device 9, and inhibits the microcomputer 11. When the stop reaches just before the area, the stop driving device 7 is stopped to fix the stop position.

The gain of the amplifier 13 or the gain C of the amplifier 13 in accordance with the detection output of the detection circuit 5 at the fixed aperture position.
By changing one (or both) of the shutter speeds of the electronic shutter of the CD 3, the signal processing unit 4
To keep the input level constant.

That is, when the detection output of the detection circuit 5 at the fixed aperture position indicates that the input level to the signal processing section 4 is higher than the fixed input level, the gain of the amplifier 13 is reduced. And / or increasing the shutter speed of the electronic shutter, the input level to the signal processing unit 4 is reduced to the constant input level. On the other hand, the detection circuit 5
If the detected output indicates that the input level to the signal processing unit 4 is lower than the predetermined input level, the gain of the amplifier 13 is increased instead of opening the aperture 1 or the shutter of the electronic shutter The input level to the signal processing unit 4 is increased to the above-mentioned constant input level by either (or both) reducing the speed.

Next, in the case where the aperture position is fixed immediately before the prohibited area, the calculation is recalculated based on a change in the detection output of the detection circuit 5 (a change in the amount of light incident on the CCD 3). When the target position is outside the prohibited area, the microcomputer 11 changes the aperture position of the aperture 1 to the target position by the aperture driving device 7, and then stops the aperture driving device 7 to change the aperture position to the target position. Fixed to.

On the other hand, when the aperture position is fixed immediately before the prohibited area, and the target position recalculated based on the fluctuation of the detection output of the detection circuit 5 is still within the prohibited area, Computer 11
The signal is obtained by changing either one (or both) of the gain of the amplifier 13 or the shutter speed of the electronic shutter of the CCD 3 in the same manner as described above while keeping the aperture position of the aperture 1 fixed. The input level to the processing unit 4 is kept constant.

As described above, control is performed so that the stop position of the stop 1 is not fixed within the range of the position where diffraction occurs in the intermediate stop, and when the target position is within this range, the stop 1 is opened and closed instead of opening and closing. Amplifier 1 for signal level
By performing a control to keep the input level to the signal processing unit 4 constant by electrically correcting it by changing the gain of 3 and the shutter speed of the electronic shutter, the occurrence of diffraction at the intermediate diaphragm is prevented, Continuous execution of exposure control is ensured.

In the above example, the present invention is applied to an exposure control apparatus having an optical system in which an ND filter is attached to a diaphragm having two diaphragm blades. The present invention may be applied to an exposure control device having an optical system in which an ND filter is attached to a stop having the following. Further, the present invention may be applied to an exposure control device in which an optical filter other than the ND filter is attached to the stop.

In the above example, the present invention is applied to an exposure control device of an image pickup device using a CCD. However, an exposure control device of an image pickup device using a solid-state image pickup device other than a CCD or an image pickup tube as an image pickup means. The present invention may be applied to a computer. Also, as in the example of FIG. 1, an exposure control device that performs control not to fix the aperture position in the prohibited area but does not perform control to electrically correct the signal level is not only a video camera or an electronic still camera, but also an exposure control device. The present invention may be applied to an exposure control device of a general camera (still camera).

The present invention is not limited to the above embodiment,
It goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0031]

As described above, according to the exposure control apparatus of the present invention, the generation of diffraction at the intermediate stop can be prevented by simple control.

When the output level of the imaging means for converting the light passing through the aperture into an electric signal is a level at which the aperture position of the aperture should be fixed within the above-described prohibited area, the aperture position is moved out of this prohibited area. In the case where the control for fixing the output level of the image pickup device is performed while the output level of the image pickup unit is fixed, it is possible to prevent the diffraction from occurring at the intermediate stop and to ensure the continuous execution of the exposure control.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a configuration of an exposure control device according to the present invention.

FIG. 2 is a block diagram showing another example of the configuration of the exposure control device according to the present invention.

FIG. 3 is a block diagram illustrating an example of a configuration of a conventional exposure control device.

FIG. 4 is a diagram showing an example of the structure of the stop, where A is a side view and B is a front view.

5 is a diagram showing a state where the stop position of the stop in FIG. 4 is an intermediate stop, where A is a side view and B is a front view.

FIG. 6 is a diagram illustrating an example of the relationship between the imaging performance of a lens and the aperture position.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Aperture, 1a, 1b ... Aperture blade, 1c ... Aperture opening part, 2 ... Lens block, 3,12 ... CCD,
4 ... Signal processing unit, 5 ... Detection circuit, 6,10,11 ...
Microcomputer 7 ... Aperture drive device 8 ... N
D filter, 9 ... diaphragm position detector, 13 ... amplifier

Claims (4)

[Claims] 1. An optical system having a lens and a diaphragm, wherein an optical system having an optical filter attached to a diaphragm blade constituting the diaphragm so as to protrude from an opening of the diaphragm, and changing a diaphragm position of the diaphragm. Driving means for detecting the stop position of the stop, control means for changing the stop position of the stop by the drive means with reference to the detection result of the detection means, An exposure control device comprising: a control unit that performs control so that a stop position of the stop is not fixed in a range in which diffraction occurs in light passing through a portion not blocked by the optical filter. 2. An optical system having a lens and a diaphragm, wherein an optical system having an optical filter attached to a diaphragm blade forming the diaphragm so as to protrude from an opening of the diaphragm, and changing a diaphragm position of the diaphragm. A driving unit for detecting an aperture position of the aperture, an imaging unit for converting light passing through the aperture into an electric signal, and an output of the imaging unit while referring to a detection result of the detection unit. Control means for changing the diaphragm position of the diaphragm by the driving means in accordance with a level, wherein an output level of the imaging means is diffracted into light passing through a portion of the aperture not blocked by the optical filter. When the stop position of the stop is a level at which the stop position of the stop should be fixed within the range where the diffraction occurs, the stop position of the stop is fixed outside the range where the diffraction occurs, and the output level of the imaging unit is electrically set. Exposure control apparatus characterized by comprising a control means for positive control. 3. The exposure control apparatus according to claim 2, wherein said control means corrects the output level by changing a gain of a variable gain amplifier for amplifying an output level of said imaging means. Exposure control device. 4. The exposure control device according to claim 2, wherein said control means corrects an output level of said image pickup means by changing a shutter speed of an electronic shutter of said image pickup means. Exposure control device.