JPH1164922A - Optical diaphragm device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of diffraction phenomenon obtained when light passes through a diaphragm by attaching a material whose transmissivity can be varied to a stop blade constituting the diaphragm so that the material comes out on the aperture part of the diaphragm and changing its transmissivity. SOLUTION: A liquid crystal device 6 which is one kind of the material whose transmissivity can be varied is attached to the stop blade constituting the diaphragm inside an optical system 1, and a liquid crystal driving device 7 driving the device 6 by voltage impressing under the control of a CPU 4 and a position detecting sensor 8 detecting the stop position of the diaphragm and transmitting a signal showing positional information to the CPU 4 are provided. In this case, the device 6 attached to the stop blade so as to come out on the aperture part of the diaphragm obstructs the optical path of the light passing through the diaphragm in the case of fine stop condition by strong light. At this time, the transmissivity of the device 6 is reduced. When the diaphragm is closed to a position where a gap which is not obstructed by the device 6 becomes fine, the transmissivity of the device 6 is increased, so that the light can be sufficiently transmitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the amount of light incident on an image pickup apparatus by opening and closing an aperture, and more particularly to an apparatus capable of preventing the occurrence of a diffraction phenomenon when light passes through the aperture.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional configuration of an optical diaphragm device used for controlling the amount of light incident on an image pickup device in a video camera, an electronic still camera, or the like.
It is as follows. Various lenses and lens aperture (aperture stop)
The light passing through the optical system 1 including the above is formed into an image on an image pickup device 2 using a CCD or the like as an image pickup device and converted into an electric signal. The electric signal is subjected to predetermined processing in a signal processing unit 3 and sent to a signal recording system (not shown) or the like.
Sent to PU4.

Based on this signal, the CPU 4 determines the aperture position (open / closed state) of the aperture according to the amount of light incident on the image pickup device 2.
Is generated and sent to the aperture driving device 5. The aperture driving device 5 adjusts the aperture position of the aperture based on this signal, and thereby controls the amount of light incident on the imaging device 2.

By the way, when the aperture is in a very small aperture state, a diffraction phenomenon occurs when light passes through the aperture, so that an image cannot be correctly formed on the image pickup device 2, so that the resolution is deteriorated. In order to avoid such a situation, the occurrence of the diffraction phenomenon has been conventionally prevented by the following method.

(1) An optical filter (ND filter) having a constant density is put in and taken out from the front of the optical system 1. (2) An ND filter is attached to a diaphragm blade forming the diaphragm. (3) The output level of the electric signal from the imaging device 2 is adjusted by changing the shutter speed of the electronic shutter of the imaging device 2.

[0006]

However, these conventional methods have the following problems. In the above method (1), a diffraction phenomenon occurs for intense light when the stop is in a minute stop state.

[0007] Even in the method (2) described above, a diffraction phenomenon occurs for intense light when the stop is in a minute stop state. In addition, since an ND filter that attenuates the light amount to about 1/10 is used, when the aperture is closed to a position where the gap that is not closed by the ND filter is small, the ND filter is equivalent to the aperture. It plays a role as a wing, and a diffraction phenomenon occurs in light passing through this gap.

In the method (3), when the shutter speed of the electronic shutter is increased with respect to intense light, the output level of the image pickup device 2 is attenuated.
Opens the aperture, so that the diffraction phenomenon does not occur,
When the shutter speed is increased, moving images are skipped, resulting in an unnatural image, and when strong light enters the imaging device 2, smear occurs.

The present invention has been made in view of the above points, and the method of (1) or (2) can prevent the occurrence of the diffraction phenomenon even in the scene where the diffraction phenomenon has occurred, and the method of the above (3). It is an object of the present invention to provide an optical diaphragm device which does not involve a problem of an image as in the method of (1).

[0010]

An optical diaphragm device according to the present invention is an optical diaphragm device having a lens diaphragm and a means for adjusting the diaphragm position of the diaphragm. A material having a variable transmittance is attached so as to protrude toward the opening, and a means for changing the transmittance of the material is provided.

According to this optical diaphragm device, when the diaphragm is in a minute diaphragm state by strong light, a material having a variable transmittance attached to the diaphragm blade so as to approach the opening of the diaphragm passes through the diaphragm. It will block the light path of light. Therefore, at this time, by reducing the transmittance of the material, it is not necessary to stop down the aperture to a state that causes the diffraction phenomenon, and thus the resolution is prevented from deteriorating.

Further, when the aperture is closed to a position where a gap which is not closed by the material is small, the transmittance of the material is increased so that light is sufficiently transmitted through the material. Therefore, this material does not play a role as a diaphragm blade equivalently, and the occurrence of a diffraction phenomenon when light passes through this gap is prevented.

As described above, the occurrence of the diffraction phenomenon can be prevented even in the scene where the diffraction phenomenon has occurred in the conventional method (1) or (2). Further, since the shutter speed of the electronic shutter is not changed according to the amount of light, there is no problem with the image as in the conventional method (3).

In addition, since a material having a variable transmittance is attached to the diaphragm blade of a diaphragm having a normal structure, the present invention can be applied to existing optical diaphragm devices without changing the diaphragm. It is possible.

[0015]

FIG. 1 shows an example of the configuration of an optical diaphragm apparatus according to the present invention. The same parts as those in FIG. 6 are denoted by the same reference numerals, and redundant description will be omitted. In this optical diaphragm device, a liquid crystal device 6 which is a kind of a material having a variable transmittance is attached to a diaphragm blade constituting a diaphragm in the optical system 1, and the liquid crystal device 6 is controlled under the control of the CPU 4. A liquid crystal driving device 7 driven by application of a voltage and a position detection sensor 8 which detects a diaphragm position of the diaphragm and sends a signal indicating the position information to the CPU 4 are provided.

As the liquid crystal device 6, various existing display methods (for example, twisted nematic (TN) type, super twisted nematic (STN) type, birefringence control (EC)
B) type, phase transition (PC) type, etc.).

FIG. 2 shows the principle of a display system of a TN type liquid crystal device as an example. A TN array cell 21 (a cell is a minimum unit of a liquid crystal device) is formed by sandwiching a nematic liquid crystal between two transparent electrode substrates such that the major axis of the liquid crystal molecules LC is continuously twisted by 90 degrees. Is done.

As shown in FIG. 2A, the polarization direction of the linearly polarized light perpendicularly incident on the substrate of the cell 21 rotates 90 degrees along the twist of the liquid crystal molecules while passing through the cell 21. On the other hand, when the voltage V is applied to the transparent electrode substrate of the cell 21, the long axis of the liquid crystal molecules LC starts to tilt in the electric field direction from a certain threshold voltage Vth. Then, at an applied voltage of about twice Vth, as shown in FIG. 2B, the major axis of most of the liquid crystal molecules LC rearranges parallel to the direction of the electric field, and the optical rotation of 90 degrees disappears.

Therefore, when the cell 21 is sandwiched between the polarizers 22 and 23 whose polarization axes are orthogonal to each other as shown in FIG. 2, the transmittance becomes maximum (about 50% as an example) in the state of FIG. 2A.
In the state of FIG. 2B, the transmittance becomes minimum (for example, about several%). Therefore, by changing the applied voltage V from Vth to 2 Vth, the transmittance can be changed between the maximum and the minimum.

The liquid crystal device 6 may be composed of a single cell since the transmittances of all the parts may be the same, or the liquid crystal device 6 may be composed of a plurality of cells. The voltages may be the same.

FIG. 3 shows an example of the structure of the stop in the optical system 1, the state of attachment of the liquid crystal device 6 to the stop, and the state of connection between the liquid crystal device 6 and the liquid crystal driving device 7. The diaphragm 11 has two diaphragm blades 11a and 11b which are arranged so as to be shifted from each other in the thickness direction by substantially the same thickness, and the diaphragm blades 11a and 11b move toward or away from each other. By moving in the direction, the size of the opening portion 11c between them changes (that is, the aperture position changes).
It has become. The liquid crystal device 6 has one of the aperture blades 11a and 11b (in the drawing, the aperture blade 11 is an example).
a) is fixedly attached so as to protrude into the opening 11c.

An aperture 11 is provided on the transparent electrode substrate of the liquid crystal device 6.
One end of the flexible wiring board 12 arranged at a position so as not to block the optical path of light passing therethrough is connected via an anisotropic conductive film (not shown). The liquid crystal driving device 7
It is mounted on this flexible wiring board 12. The other end of the flexible wiring board 12 is connected to a printed board (not shown) by soldering or the like, and the CPU 4 of FIG. 1 is mounted on the printed board. (As another example, the liquid crystal driving device 7 is mounted on the printed circuit board with a CP.
It may be mounted together with U4. )

Next, an example of the operation of the optical diaphragm device will be described for a case where the amount of light incident on the imaging device 2 changes from a small state to a large state. When the amount of incident light is sufficiently small, the aperture driving device 5 has fully opened the aperture 11 as shown in FIG. In this state, the liquid crystal device 6 is
Is not located on the optical path of the light passing through, the light enters the imaging device 2 only through the opening 11c. CPU4
Controls the liquid crystal driving device 7 from this state,
The transmittance of the liquid crystal device 6 is maximized.

When the amount of incident light starts to increase, the diaphragm driving device 5 gradually closes the diaphragm 11 so that the diaphragm 11
The liquid crystal device 6 comes to be on the optical path of the light passing therethrough. Therefore, part of the light passes through the liquid crystal device 6 and the rest enters the image pickup device 2 through the opening 11c. Then, when the amount of incident light increases to a certain degree, as shown in FIG. 4, a gap that is not closed by the liquid crystal device 6 (a gap between the liquid crystal device 6 and the diaphragm blade 11b) becomes small. The diaphragm 11 closes to this point (the flexible wiring board 12 and the liquid crystal driving device 7 are not shown in FIGS. 4 and 5 described later).

At this stop position, the transmittance of the liquid crystal device 6 remains at the maximum, so that the liquid crystal device 6 does not function equivalently as a stop blade, and a diffraction phenomenon occurs when light passes through this gap. Is prevented.

When the amount of incident light further increases, the aperture driving device 5 further closes the aperture 11, so that the optical path of light passing through the aperture 11 is completely blocked by the liquid crystal device 6. Therefore, the light passes through only the liquid crystal device 6 and enters the imaging device 2. Then, as the amount of incident light increases, the area of the light transmitting portion of the liquid crystal device 6 becomes smaller, and the liquid crystal device 6 enters a state of a minute aperture as shown in FIG.

When the sensor 8 detects that the diaphragm 11 is closed to a position slightly before the position causing the diffraction phenomenon, the CPU 4 controls the diaphragm driving device 5 to stop the closing operation of the diaphragm 11. And the liquid crystal driving device 7
Is controlled to change the applied voltage to the liquid crystal device 6, thereby changing the transmittance of the liquid crystal device 6 according to the amount of light. In other words, instead of continuing the closing operation of the diaphragm 11 with the increase in the light amount, the position of the diaphragm 11 is fixed and the transmittance of the liquid crystal device 6 is reduced, so that the amount of light incident on the imaging device 2 is controlled. . Since the stop 11 is fixed at a position where no diffraction phenomenon occurs, the resolution is prevented from deteriorating.

As described above, according to this optical diaphragm device,
As shown in FIG. 4 and FIG. 5, even in a scene where a diffraction phenomenon has occurred in the conventional method (1) or (2), the occurrence of the diffraction phenomenon is prevented. Further, since the shutter speed of the electronic shutter of the imaging device 2 does not change in accordance with the light amount, there is no problem with the image as in the conventional method (3).

Moreover, the diaphragm blade 1 of the diaphragm 11 having a normal structure is used.
Since the liquid crystal device 6 is attached to 1a or 11b, the present invention can be applied to an existing optical diaphragm device without replacing the diaphragm 11.

In the above operation example, the case where the amount of light incident on the imaging device 2 changes from a small state to a large state has been described. For example, a position slightly before the position causing the diffraction phenomenon in the state of FIG. If the amount of incident light starts to decrease after stopping the closing operation of the aperture 11 in step, the aperture driving device 5 is controlled to open the aperture 11 without reducing the transmittance of the liquid crystal device 6. What should I do?

Conversely, even when the incident light quantity changes from a large quantity to a small quantity, or when the incident light quantity changes irregularly as in the case of normal photographing, the above-described operation example is used. Similarly, the occurrence of the diffraction phenomenon in the scenes shown in FIGS. 4 and 5 is prevented.

In the above example, a liquid crystal device is used as a material having a variable transmittance, but other materials having a variable transmittance may be used. Further, in the above example, the present invention is applied to an optical aperture device having two aperture blades, but the present invention may be applied to an optical aperture device having an appropriate number of aperture blades. In addition, the present invention is not limited to the above-described embodiments, and may take various other configurations without departing from the gist of the present invention.

[0033]

As described above, according to the optical diaphragm device of the present invention, when the diaphragm is in a minute diaphragm state due to strong light, the transmittance of the material having a variable transmittance attached to the diaphragm blade is reduced. By doing so, it is possible to prevent a diffraction phenomenon from occurring when light passes through the stop.

Further, when the aperture is closed to a position where the gap not closed by the material becomes very small, the transmittance of the material is increased so that the material equivalently serves as a diaphragm blade. Thus, it is possible to prevent a diffraction phenomenon from occurring when light passes through the gap.

Accordingly, even in a scene where a diffraction phenomenon has occurred in the conventional method, the occurrence of the diffraction phenomenon can be prevented. Further, since the shutter speed of the electronic shutter is not changed according to the amount of light, there is no problem with the image as in the conventional method.

Further, since a material having a variable transmittance is attached to the diaphragm blade of the diaphragm having a normal structure, the present invention can be applied to an existing optical diaphragm device without changing the diaphragm. It is possible. Therefore, the optical diaphragm device according to the present invention can be easily and economically configured.

[Brief description of the drawings]

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

FIG. 2 is a perspective view illustrating an example of a principle of a display method of a liquid crystal device.

FIGS. 3A and 3B are diagrams illustrating an example of a structure of a diaphragm, an attached state of a liquid crystal device 6, and a connected state of a liquid crystal driving device 7, wherein A is a side view and B is a front view.

FIG. 4 is a diagram showing an example of a state in which the aperture position has changed, where A is a side view and B is a front view.

FIGS. 5A and 5B are diagrams illustrating an example of a state in which the aperture position is changed, where A is a side view and B is a front view.

FIG. 6 is a block diagram illustrating an example of a configuration of a conventional optical stop device.

[Explanation of symbols]

Reference Signs List 1 optical system, 2 imaging device, 3 signal processing unit, 4
CPU, 5 aperture driving device, 6 liquid crystal device, 7
Liquid crystal drive device, 8 position detection sensor, 11 diaphragm, 11a, 11b diaphragm blade, 12 flexible wiring board, 21 cell, 22, 23 polarizer

Claims (2)

[Claims] 1. An optical diaphragm apparatus comprising a lens diaphragm and a means for adjusting the diaphragm position of the diaphragm, wherein a transmittance of a diaphragm blade constituting the diaphragm is set so as to approach an opening of the diaphragm. An optical diaphragm device, wherein a variable material is attached, and means for changing the transmittance of the material is provided. 2. An optical diaphragm apparatus comprising a lens diaphragm and a means for adjusting the diaphragm position of the diaphragm, wherein the aperture blades constituting the diaphragm are arranged so as to protrude toward an opening of the diaphragm so as to have a transmittance. A variable material is attached, detecting means for detecting the aperture position of the aperture, and, in response to the detection of the minute aperture state of the aperture by the detecting means, reducing the transmittance of the material, Means for increasing the transmittance of the material in response to the detection means detecting that the aperture has been closed to a position where the gap not closed by the material is small. Characteristic optical diaphragm device.