JPH09261545A - Image input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select a transmission-through band of a spatial filter for preventing moire depending on the resolution in the image input device provided with an image shift means to receive a plurality of images with different resolution. SOLUTION: A position of an image formed on an image pickup face of a CCD 14 is deviated by tilting a transparent refraction flat plate 22 with respect to an optical axis 10 of an incident light from a subject to attain shift of image. An image is shifted at a distance shorter than a distance between photo sensing parts of the CCD 14 and resulting plural images are synthesized to obtain an image with high resolution. A transmission-through band of the spatial filter 12 for preventing moire is selected by changing a relative angle between double refraction plates 20, 21. In the case of input of an image with high resolution by an image shift mechanism 13, the transmission-through band of the spatial filter 12 is selected toward high frequencies to obtain an image with excellent resolution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device capable of inputting images having a plurality of different resolutions, and more particularly to an image input device provided with an image shift means and a spatial filter for removing moire.

[0002]

2. Description of the Related Art In a video camera for picking up a moving image or a still camera as an image input device for picking up a still image, a solid-state image pickup device such as a CCD in which pixels are arranged in a two-dimensional matrix to form an image pickup surface. Is widely used.
The resolution of the image to be captured is increasing, and it is desired that the image capturing apparatus can also input a high resolution image. To increase the resolution, it is sufficient to increase the number of pixels on the image pickup surface of the solid-state image pickup device, but the production is technically difficult, or the productivity becomes poor and the cost becomes high. In consideration of such a situation, an image shift method has been proposed as a method for obtaining high resolution while using an image sensor having a small number of pixels.

FIG. 22 shows the basic principle of the image shift method. An image shift mechanism 3 is provided in front of an image pickup surface of a CCD 4, which is a solid-state image pickup device, along an optical axis 2 of a lens group 1 on which light from a subject enters. The image shift mechanism 3 includes a refraction plate 5, and by changing the inclination angle with respect to the optical axis 2, the optical path 2a reaching the image pickup surface of the CCD 4 can be changed by Δ.

23 to 26 show the principle of improving the resolution by the image shift operation. 23 is the same as FIG.
3 shows an array pattern of pixels which are photosensitive portions on the image pickup surface of CCD 4. The numbers 1 to 9 in FIG. 23 are the arrangement patterns of the photosensitive portions, and the distance between the arrangement patterns of the photosensitive portions in the horizontal direction is Δx, and the distance between the arrangement patterns of the photosensitive portions in the vertical direction is Δy. When the image is formed at the first position on the image pickup surface of the CCD 14, the video signals from the positions 1 to 9 in FIG. 23 are taken out from the CCD 4 as the first image signal.
Next, the position of the image formed on the image pickup surface of the CCD 4 is set to Δx
When the refracting plate 5 is tilted so as to be shifted by / 2 or Δy / 2, the incident optical path 2a is displaced. When the video signal when the incident optical path 2a is deviated is taken out from the CCD 4 as the second image signal and is combined with the first image signal, an image equivalent to the state where the photosensitive portion is arranged as shown in FIG. 24 is obtained. As a result, the spatial sampling interval is shortened and high resolution can be obtained.

FIG. 25 is an equivalent view realized by an image in which the image formed on the CCD 4 is shifted by Δx / 2 by tilting the refracting plate 5 to take out the second image signal and combined with the first image signal. The arrangement of various photosensitive parts is shown. FIG.
Reference numeral 6 shifts the image formed on the CCD 4 by Δx / 2 to obtain a second image signal, and then outputs Δx / 2 and Δy / 2.
The third image signal is picked up by shifting by Δy / 2
The layout of the photosensitive portions is equivalent to the case where the fourth image signal is taken out by shifting each and the image obtained by combining the first to fourth image signals is obtained.

Even if the photosensitive portion is arranged as shown in FIG.
Although high resolution can be obtained by performing image shift as shown in FIGS. 24 to 26,
The following issues are a problem. Generally, in the CCD 4 which is a solid-state image sensor used in a video camera, the incident light image is sampled and taken in at a constant interval in the vertical and horizontal directions, so that the highest spatial frequency that can be resolved is sampled. 1 / spatial frequency
2, that is, the Nyquist frequency. When a spatial frequency component higher than the Nyquist frequency is included, a false signal or moire occurs. In order not to generate these, it is necessary to reduce high spatial frequency components above the Nyquist frequency before sampling, and a spatial filter is used. However, in the optical system as shown in FIG. 22, if the spatial filter is used to reduce the frequency components exceeding the Nyquist frequency, the spatial filter is used when the image shift is performed to shorten the sampling interval in order to achieve high resolution. Since the high frequency components are reduced by, the high resolution cannot be obtained.

FIG. 27 shows a configuration for switching between two types of spatial filters disclosed in JP-A-3-226078 as prior art. Optical axis 2 between lens group 1 and CCD 4
The spatial filter 6 can be inserted by switching the low resolution spatial low pass filter 7 and the high resolution spatial low pass filter 8 above. Low resolution spatial low pass filter 7
The high-resolution spatial low-pass filter 8 is supported by the support frame 9. The low-resolution spatial low-pass filter 7 is used when the image shift is not performed, and the high-resolution spatial low-pass filter 8 is used when the image shift is performed.
Switch to use. As a method for obtaining high resolution, not only image shift can be used but also a color image can be captured using a color image sensor and a monochrome image can be captured at high resolution. Furthermore, there is a method in which the spatial low-pass filter is used only when capturing a low-resolution image, and the spatial low-pass filter is retracted from the optical axis when capturing a high-resolution image.

Further, in Japanese Patent Laid-Open No. 4-236585, a birefringent plate is used for a spatial filter, the birefringent plate is rotatable so that a transmission band is variable, and a spatial filter is inserted within a depth of focus of an optical system for focusing. An image pickup optical system has been proposed which uses blurring of an image based on a shift to prevent the resolution from being lowered too much.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the prior art of No. 8, although the spatial filters are exchanged according to a plurality of transmission bands when the image sampling interval is changed by the image shift, a plurality of different spatial filters are required, and the manufacturing cost due to the increase in the number of filters is increased. Increase, the number of parts, and the size of the image pickup apparatus are increased. Furthermore, in order to replace the spatial filter according to the resolution, one spatial filter is retracted from the optical axis and the other spatial filter is inserted, so that the low resolution mode and the high resolution mode are switched. Rapid switching is difficult.

In the prior art in which a spatial low-pass filter is used in low-resolution shooting and the spatial low-pass filter is retracted from the optical axis when high-resolution shooting is performed, the back focus is short although the number of filters and the replacement speed are improved. Therefore, it may be necessary to compensate the optical system by inserting a dummy glass or the like. When a dummy glass or the like is inserted, the same problem as in the case of replacing the optical filter eventually arises.

Further, in the prior art of Japanese Patent Laid-Open No. 4-236585, although the resolution of the image is reduced by utilizing the image blur itself due to the focus shift, a mechanism for changing the frequency band by rotating the spatial filter is concrete. However, it is difficult to realize based only on the description. Further, the disclosed idea is about an operation of compensating for a decrease in resolution due to a focus shift, and is different from the idea to cope with the case where the image shift is made to have a higher resolution than the resolution of the image pickup device itself.

Further, when inputting images having different resolutions by image shift, an image shift mechanism is required in addition to the spatial low pass filter for low resolution and the spatial low pass filter for high resolution. When the image shift is performed by inclining the refraction plate and shifting the optical path, the optical path length after the refraction plate is changed by inserting the image shift mechanism, and it is necessary to improve or compensate the optical system.

The object of the present invention is to solve the above-mentioned problems.
An object of the present invention is to provide an image input device capable of switching a plurality of resolutions at high speed and easily and capable of obtaining an optimum image according to the resolutions.

[0014]

According to the present invention, there is provided image shift means for displacing a relative positional relationship between an optical path incident on an image pickup device and the image pickup device. In an image input device capable of inputting an image having a second resolution higher than the resolution,
A spatial filter that is provided between an optical system that inputs incident light from a subject and an image pickup device that captures an image of the subject, and that is capable of switching the transmission band of the spatial frequency of the incident light to at least two types, and a control means. When inputting an image having a first resolution, the spatial filter has a first transmission band, and when inputting an image having a second resolution, the spatial filter can transmit a spatial frequency higher than the first transmission band. The second transmission band, the image shift means operates, and the control means controls so that a plurality of images can be input in synchronization with the shift of the optical path incident on the image sensor. It is an image input device. According to the present invention,
The spatial filter can switch the transmission band of the spatial frequency of the incident light from the subject into a first transmission band corresponding to the first resolution and a second transmission band corresponding to the second resolution. Since the second pass band can pass spatial frequency components higher than the first pass band, when inputting an image having a second resolution higher than the first resolution, the image input can be performed without lowering the resolution. Can be done.

Further, in the present invention, the image shift means is provided between an optical system for inputting incident light from a subject and a solid-state image pickup device for taking in an image from the subject and picks up an image with an inclination with respect to the optical axis. It is characterized by comprising a transparent flat plate-like refracting plate capable of shifting the optical path incident on the element. According to the invention, by tilting the transparent flat refracting plate with respect to the optical axis, the optical path incident on the image sensor is shifted, and a resolution higher than the arrangement pitch of the photosensitive parts of the image sensor is equivalently obtained. be able to.

Further, the present invention comprises an image shift means for shifting the relative positional relationship between the optical path incident on the image pickup element and the image pickup element, and the first resolution and the first shift higher than the first resolution by the image shift means. In an image input device capable of inputting an image having a resolution of 2, the image shift means is provided between an optical system for inputting incident light from a subject and an image sensor for capturing an image of the subject,
It is possible to operate as a spatial filter capable of switching at least two types of transmission bands of the spatial frequency of incident light,
As the image shift means, a part of the spatial filter is tilted with respect to the optical axis and is configured to shift the optical path incident on the image pickup element, and is the control means, and when an image having the first resolution is input, The spatial filter serves as the first transmission band, and when an image having the second resolution is input, the spatial filter serves as the second transmission band capable of transmitting a spatial frequency higher than the first transmission band, and the image shift means. The image input device is characterized by including a control unit that operates as described above and controls so that a plurality of images can be input in synchronization with the deviation of the optical path incident on the image pickup element. According to the present invention, the spatial filter can switch the first and second transmission bands corresponding to the first and second resolutions, and a part of the spatial filter is tilted with respect to the optical axis to form an image. It can also be operated as a shift means. By the image shift, the second resolution is switched to be higher than the first resolution, and the second transmission band can transmit a spatial frequency higher than the first transmission band. It can be obtained while preventing an increase in back focus due to the insertion of the mechanism. Further, since the image shift and the spatial filter can be combined, a compact optical system can be realized.

Further, according to the present invention, the image having the first resolution is a moving image. According to the present invention, since the image of the first resolution is a moving image, it is possible to capture two types of still images and moving images.

Further, in the present invention, the spatial filter is configured to include at least two or more birefringent plates supported so as to be rotatable relative to each other about an axis parallel to the optical axis. It is possible to switch to the first and second transmission bands by relative rotation of. According to the present invention, since the transmission band of the spatial filter can be switched by the relative rotation of two or more birefringent plates, it is not necessary to move the spatial filter itself from the optical axis, and it is possible to quickly perform the operation with a simple mechanism. The transmission band can be switched.

Further, in the present invention, the relative rotation angle between the birefringent plates is about 4 between the first transmission band and the second transmission band.
It is characterized by changing 5 degrees. According to the present invention, the transmission band can be switched by changing the rotation angle of about 45 degrees, so that the change distance of the movable mechanism for switching can be small and the switching can be performed quickly. Further, since the mechanism is simplified, the size and durability can be improved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic configuration of an image input device as an embodiment of the present invention. An image from a subject is incident along the optical axis 10, passes through the lens group 11 and the spatial filter 12, and the image shift mechanism 13 interposed between the lens group 11 and the spatial filter 12, and then the CCD 14 which is a solid-state image pickup device. Form an image on the imaging surface. Image shift mechanism 13 and spatial filter 12
Are mechanically driven by the image shift mechanism driving device 15 and the spatial filter driving device 16, respectively.
The image shift mechanism driving device 15 and the spatial filter driving device 16 are controlled by the system controller 17. The output corresponding to the image formed on the image pickup surface of the CCD 14 is converted into a video signal by the signal processing circuit 18.

The spatial filter 12 comprises two birefringent plates 2
Including 0 and 21. The birefringent plates 20 and 21 are relatively rotatable around the optical axis 10. Two birefringent plates 20, 2
When 1 is relatively rotated about the optical axis 10, it is possible to change the transmission band, which is the range of spatial frequencies that can be transmitted. The configuration and operating principle of the spatial filter 12 will be described later. The image shift mechanism 13
Basically, the image shift operation is performed by tilting the flat refracting plate 22 with respect to the optical axis 10 and changing the optical path incident on the image pickup surface of the CCD 14 as in the prior art shown in FIG.

The system controller 17 has a CCD 14
When an image is input at the first resolution, which is the original resolution of, the control signal for normal resolution is sent to the image shift mechanism driving device 15 and the spatial filter driving device 16. The image shift mechanism driving device 15 stops at a position where the surface of the refraction plate 22 is substantially perpendicular to the optical axis 10. The incident light from the subject is the lens group 11 and the refraction plate 2.
2. The light passes through the birefringent plates 20 and 21 and forms an image on the image pickup surface of the CCD 14. The spatial filter driving device 16 includes the birefringent plate 2
0 and 21 are relatively rotated about the optical axis 10, and the transmission band of the incident light is stopped at a predetermined position which is the first transmission band where moire does not occur at the first resolution. CCD1
4 outputs a signal corresponding to the image formed on the imaging surface,
The signal processing circuit 18 converts the video signal. The video signal can be output as a still image stored in the image memory, or can be output as a so-called moving image that is displayed on a cathode ray tube (abbreviated as "CRT") as a conventional video signal.

When shooting at a second resolution which provides an image having a higher resolution than the first resolution, the system controller 17 gives a control signal for high resolution to the spatial filter driving device 16 to cause the spatial filter 12 to operate. Birefringent plate 20,
21 is relatively rotated about the optical axis 10. The transmission band of the light incident on the birefringent plates 20 and 21 of the spatial filter 12 is stopped at a position where it becomes a second transmission band capable of transmitting a spatial frequency band higher than the first transmission band. Next, the system controller 17 sends a control signal to the image shift mechanism driving device 15,
2 and the prior art described in FIGS. 23 to 26,
Image shift mechanism 1 each time one frame image is captured
The refraction plate 22 of 3 is tilted with respect to the optical axis 10, and the CCD 1
The image forming position of 4 on the imaging surface is moved to 2 or 4 positions. In synchronization with such movement of the image forming position, the system controller 17 causes the CCD 14 and the signal processing circuit 18 to operate.
A control signal is also sent to the control unit to synthesize the images to generate image data having a higher resolution than the first resolution, that is, a short spatial sampling interval.

2, 3 and 4 show a spatial filter 1
2 shows the principle that the transmission band can be made variable by the relative rotation of the birefringent plates 20 and 21. For convenience of explanation, a case where one birefringent plate 20 is fixed and only the other birefringent plate 21 is rotated to make the transmission band variable is shown as an example. As shown in FIG. 2, in the direction of the optical axis 10, the x-axis,
X, y, z orthogonal 3 where the horizontal direction and the vertical direction of the array of pixels on the imaging surface of the CCD 14 are the z axis and the y axis, respectively.
Assume the axial direction. The two birefringent plates 20 and 21 are shown in FIG.
Although they are spaced apart, they can be in contact with each other. Although the birefringent plates 20 and 21 have a rectangular plate shape, they may have another shape, for example, a disk shape, as long as the effective light beam entering the CCD 14 can be transmitted in the first and second transmission bands. The optical axes of the birefringent plates 20 and 21 are cut out at about 45 degrees with respect to the incident optical axis. FIG. 3 shows the projection of the optical axes of the birefringent plates 20 and 21 onto the zy plane. The optical axis of the birefringent plate 20 shown in FIG. 3A is in the z-axis direction with respect to the zy plane, and the optical axis direction of the birefringent plate 21 shown in FIG. 3B is zy.
Projection is performed in the direction of about 135 degrees counterclockwise from the z-axis centering on the origin of the surface. As shown in FIG. 4, the light incident on the birefringent plates 20 and 21 is separated into ordinary light and extraordinary light, and separated and imaged on the imaging surface of the CCD 14. First, the birefringent plate 20 separates an ordinary light image 23 and an extraordinary light image 24, and the birefringent plate 21 separates the respective images 23 and 24 as ordinary light and a component separated as extraordinary light. An image is formed by and images 25 and 26 are added. According to the configuration of the birefringent plates 20 and 21 described above,
The brightness of the four separation point images 23 to 26 can be made substantially equal to each other, and the distance L between the separation points in the horizontal direction can be made substantially the distance between the photosensitive portions of the CCD 14.

FIG. 5 shows an example of a transmission band in which the spatial filter 12 is made to correspond to the 1/3 inch CCD 14.
The separation width of ordinary light and extraordinary light of the birefringent plate 20 is 7.5 μm,
The separation width of the birefringent plate 21 is 5.3 μm. The Nyquist frequency fn, which is 1/2 the sampling frequency fs, matches the cutoff frequency fc of the spatial filter 12, and the transmission band is reduced at frequencies above the Nyquist frequency fn, so that the occurrence of spurious signals and moire is reduced. can do.

6 and 7, the spatial filter 12 is
The structure which switches to the 2nd transmission band which can permeate | transmit a frequency band higher than a 1st transmission band is shown. FIG. 6 shows the direction of the optical axis with respect to the zy plane of the birefringent plates 20 and 21 in (a).
And (b) are respectively projected and shown. The optical axis direction of the birefringent plate 20 is the z-axis direction, and the optical axis of the birefringent plate 21 is about 18 from the z-axis counterclockwise about the origin of the zy plane.
The direction is 0 degree. With such a configuration of the spatial filter 12, as shown in FIG.
It is separated into ordinary light and extraordinary light by 0, 21 and CCD 1
4, and two separated point images 23 and 27 are formed. The two separation point images 23 and 27 have almost the same brightness, and the separation point distance is 2.2 μm.

FIG. 8 shows the transmission band of the spatial filter 12 constructed according to FIGS. 6 and 7. It can be seen that the cut-off frequency fc shifts to a higher range and can be transmitted up to a higher frequency band as compared with FIG. Therefore, even when the spatial sampling interval is shortened by the image shift and the sampling frequency fs is increased, it is possible to transmit the high frequency component.
A high-resolution image can be obtained.

Comparing the configurations of the spatial filters 12 in the first and second transmission bands with reference to FIGS. 3 and 6, the optical axis of the birefringent plate 21 changes about 45 degrees counterclockwise on the zy plane. . Therefore, in order to switch such a transmission band, the birefringence plate 21 is angularly displaced counterclockwise by about 45 degrees from the state of FIG. 3 showing the first transmission band. Good. From the second transmission band to the first
When switching to the transmission band of the above, it may be changed about 45 degrees clockwise about the optical axis 10. In this way, the spatial filter 12 can be switched with a relatively small rotation angle of about 45 degrees, so that the time required for switching the transmission band is short and the distance to be moved is small, so that the durability is improved. It is possible to obtain a high structure. The same effect can be obtained even if the positions of the two birefringent plates 20 and 21 are switched with respect to the direction of the incident optical axis 10.
The positional relationship of the birefringent plates 20 and 21 with respect to the optical axis 10 can be exchanged. Also, the rotation axis for switching is
It may be parallel to the optical axis 10.

FIG. 9 and FIG. 10 show an example of the structure of the spatial filter driving device 16 which rotates the birefringent plate 21 relative to the birefringent plate 20. The birefringent plate 21 has a disc shape, and an outer peripheral portion thereof is held by an annular holding member 30. The holding member 30 is supported by at least three points on the outer circumference by a rotating roller 31, and is rotatable about an incident optical axis or an axis parallel to the optical axis. further,
A protrusion 32 is provided on the outer periphery of the holding member 30 and is connected to the lever 33. The lever 33 is biased in one direction by a torsion spring 34. A groove 35 extending in the radial direction of the birefringent plate 21 and the holding member 30 is formed in the protrusion 32, and a pin 36 fixed to one end of the lever 33 is coupled to the protrusion 32.
The other end of the lever 33 is fixed to the tip of the rotary shaft 38 of the motor 37. The axial direction of the rotating shaft 38 is the birefringent plate 2
1 and the rotation axis of the holding member 30. The torsion spring 34 presses the lever 33 about the rotating shaft 38 so that the lever 33 is in the state shown by the solid line in FIG. 9. The state shown by the solid line in FIG. 9 corresponds to the first transmission band as the predetermined position when the driving force by the motor 37 is not generated.

When the motor 37 is energized to generate a rotational driving force in the clockwise direction of FIG. 9, if the rotational driving force exceeds the spring biasing force of the torsion spring 34, the lever 33 moves clockwise around the rotating shaft 38. Swing displacement in the circumferential direction.
The movement of the pin 36 is restricted at the end of the groove 35, and the pin 36 stops at the position indicated by the imaginary line. The stop position at this time is a predetermined position where the spatial filter 12 is in the second transmission band. When the lever 33 swings between the position corresponding to the first transmission band indicated by the solid line and the position corresponding to the second transmission band indicated by the phantom line, the pin 36 moves in the groove 35. To do.
In FIG. 9, the positioning is performed when the pin 36 is located at the radially outer end of the groove 35. However, as shown in FIG. 10, the pin 36 corresponding to the first transmission band indicated by the solid line is A configuration is also possible in which the position of the end of the groove 35 that stops and the position of the end of the groove 35 that stops the pin 36 for forming the second transmission band shown by the phantom line change. That is, FIG.
Then, with respect to the first transmission band, the radially outer end of the groove 35 is positioned, and with respect to the second transmission band, the radially inner end of the groove 35 is positioned. The lever 33 and the groove 35 are different in length from the configuration of FIG. 9 and the configuration of FIG. 10. As shown in FIG. 9 and FIG. 10, the end of the groove 35 becomes the limiting position and the rotation angle of the birefringent plate 21 can be determined, so that the configuration of the spatial filter driving device 16 can be simplified and downsized. It is possible to switch the transmission band quickly.

11 and 12 show the spatial filter 12
Another configuration example of the birefringent plate 21 and the spatial filter driving device 16 will be shown. The disc-shaped birefringent plate 21 is held at its outer peripheral portion by a holding member 40 having an annular shape. Holding member 40
Is rotatably supported on the outer periphery by at least three rotating rollers 41. The rotation axis is parallel to the incident optical axis. A protrusion 42 is provided on the outer peripheral portion of the holding member 40, and is connected to one end of a lever 43. The lever 43 has an arc-shaped portion matching the shape of the holding member 40, and is configured so as not to block incident light. The other end of the lever 43 is biased upward in FIG. 11 by a tension spring 44. The connection between one end of the lever 43 and the protrusion 42 is the protrusion 4
2, a groove 45 formed so as to extend outward in the radial direction of the holding member 40, and a pin 46 provided at one end of the lever 43.
And done by The pin 46 is movable in the groove 45 along the radial direction of the holding member 40. The other end of the lever 43 can be pulled by the plunger 47 in the direction opposite to the direction pulled by the tension spring 44. A shaft 48 is provided between the other end of the lever 43 and the circular arc portion, and is displaceable with the shaft 48 as a fulcrum. The plunger 47 is capable of displacing the movable portion 49 in the vertical direction in the drawing, and the movable portion 49 is coupled to the other end of the lever 43.

FIG. 12 shows a state in which the plunger 47 has sucked the movable portion 49. The attraction force of the plunger 47 is larger than the tension force of the tension spring 44. As a result, the lever 43 is angularly displaced about the shaft 48 as a fulcrum, and the groove 45 is radially inward.
The pin 46, which has been coupled with, moves radially outward to a position where it is coupled with the groove 45. The holding member 40 is rotated by such movement of the lever 43, and the direction of the optical axis of the birefringent plate 21 can be changed.

The state in FIG. 11 in which the other end of the lever 43 is pulled by the tension spring 44 without generating the driving force in the plunger 47 is the predetermined position which is the first transmission band, and the attraction force by the plunger 47 causes the compounding to occur. When the state shown in FIG. 12 in which the refraction plate 21 is rotated is the predetermined position where the second transmission band is obtained, the rotation angle of the birefringence plate 21 is determined by the two stop positions, the mechanism is simple and small, and the space is small. It is possible to realize the spatial filter drive device 16 that can change the transmission band of the filter 12 rapidly.

FIG. 13 shows still another configuration example of the spatial filter driving device 16. The birefringent plate 21 has a disc shape, and the outer circumference thereof is held by a ring-shaped holding member 50. The holding member 50 has a structure in which at least three points on the outer circumference are supported by the rotating roller 51 and is rotatable about an axis parallel to the incident optical axis. The rotational driving force from the worm gear 52 is transmitted to the outer periphery of the holding member 50. The worm gear 52 is rotated by the motor 53, and the rotational driving force is transmitted to the holding member 50 via the wheel gear portion 54 formed on the outer periphery of the holding member 50 as the worm gear 52 rotates. Since the rotation speed of the motor 53 corresponds to the rotation angle of the holding member 50, the motor 53
The rotation angle of the birefringent plate 21 can be detected and accurately controlled by counting the number of rotations of (1) with a counter (not shown). Such a simplified mechanism
It can be configured in a small size, and the transmission band of the spatial filter 12 can be changed quickly.

In the above description, one birefringent plate 20 is fixed and only the other birefringent plate 21 is driven to rotate about 45 degrees about an axis parallel to the incident optical axis. When the refraction plates 20 and 21 are equivalent to each other, for example, when the relative change angle is 45 degrees, one of the refraction plates 20 and 21 is rotated clockwise 22.
A configuration in which the other is rotated by 5 degrees and the other by 22.5 degrees counterclockwise is also possible.

The birefringent plates 20 and 21 have been conventionally used as a component of a fixed band spatial filter in a video movie or the like. On the other hand, by changing the relative angle, the transmission band as a spatial filter can be made variable. Therefore, it is not necessary to prepare a plurality of spatial filters for attachment / detachment, replacement, and compensation of the optical system, so that it is possible to suppress an increase in the size of the mechanism and an increase in the number of parts. Further, since the birefringent plate of the spatial filter used in the conventional video movie can be used, it is possible to suppress the cost increase when a new spatial filter is manufactured. Furthermore, since the mechanism of the spatial filter is simple and small,
The transmission band of the spatial filter can be changed quickly.

FIGS. 14 and 15 show another example of the arrangement of the optical axes for obtaining the first transmission band in the arrangement of the birefringent plates 20 and 21 as shown in FIG. 2 and the incident light. The separated states are shown. The optical axes of the birefringent plates 20 and 21 are
It is cut out at about 45 degrees with respect to the incident optical axis, and as shown in FIG. 14A, yz of the optical axis of the birefringent plate 20.
The fact that the projection on the plane is in the z-axis direction means that FIG.
The configuration is the same as that described above. In this configuration, the projection of the optical axis of the birefringent plate 21 on the zy plane is about 45 degrees counterclockwise from the z axis with the origin of the zy plane as the center. The incident light is separated into ordinary light and extraordinary light by the birefringent plates 20 and 21, and the CC light is transmitted in the same manner as in FIGS.
Images 23 to 26, which are separation points, are formed as shown in FIG. 15 on the imaging surface of D14. The brightness of each separation point is substantially equal, and the distance L between the separation points in the horizontal direction is approximately equal to the CCD 14.
It is equal to the distance between the photosensitive parts. The transmission band of the incident light at this time is the same first transmission band as in the cases of FIGS. 3 and 4. In the case of the second transmission band, the birefringent plate 21 is rotated as shown in FIGS. 6 and 7 described above. FIG.
From (b) to the state of FIG. 6 (b), the birefringent plate 21 is
It may be rotated counterclockwise by 135 degrees about the incident optical axis. The positions of the birefringent plates 20 and 21 with respect to the optical axis may be interchanged back and forth, and since the rotational displacement is relative, the birefringent plate 20 may be rotated to fix the birefringent plate 21. The birefringent plates 20 and 21 may be rotated equally.

16 and 17 show still another example of the spatial filter 12 whose transmission band can be switched in the arrangement shown in FIG. The birefringent plates 20 and 21 are cut out at about 45 degrees with respect to the incident optical axis, and the projections on the yz plane are as shown in FIGS. 16A and 16B, respectively. Both 21 are arranged so as to be in the z direction.
The light incident on the birefringent plates 20 and 21 is separated into ordinary light and extraordinary light, and images 23 and 27 as separation points as shown in FIG. 17 are formed on the image pickup surface of the CCD 14 in the same manner as in FIG. To be done. The brightness of both separation points is substantially equal, and the distance between the separation points is approximately equal to 1/2 of the distance between the photosensitive parts of the CCD 14. Cutoff frequency fc of the spatial filter 12
Is the same as the Nyquist frequency fn, and the transmission band is reduced at frequencies above the Nyquist fn, so it is possible to reduce the occurrence of spurious signals and moire.

FIGS. 18 and 19 show an example of imaging at the second resolution. The projection of the optical axes of the birefringent plates 20 and 21 onto the yz plane is shown in FIGS. 18 (a) and 18 (b), respectively. A state in which the incident light is separated into ordinary light and extraordinary light by the birefringent plates 20 and 21 and separated on the image pickup surface of the CCD 14 is shown in FIG. Since the brightness of the separation points is almost equal and the distance between the separation points is shorter than that in FIG. 17,
The pass band is shifted to the higher frequency side, and the spatial filter of the second pass band can be realized. In the state of FIG. 16B and the state of FIG. 18B, the birefringent plate 21 is rotated by about 180 degrees. Therefore, if the birefringent plate 21 is rotated 180 degrees about the incident optical axis, the first resolution and the second resolution can be switched. Note that the two birefringent plates 20 and 21 have the same effect even if they are switched in the direction of the incident optical axis, and the rotation angles are relative. The same effect can be obtained by rotating the birefringent plates 20 and 21 equally.

Further, although the image shift is performed by utilizing the inclination of the refraction plate 22 in this embodiment, if the optical path incident on the CCD 14 which is the solid-state image pickup device is relatively displaced, the image is similarly obtained. The shift can increase the resolution.

FIG. 20 shows the structure of an image input apparatus according to another embodiment of the present invention. In the present embodiment, portions corresponding to the embodiment of FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted. Image shift mechanism 60 of the present embodiment
Are arranged between the lens group 11 and the CCD 14.
The image shift mechanism 60 includes an image shift mechanism drive device 65 capable of inclining the birefringent plates 61 and 62 with respect to the incident optical axis 10, and a birefringent plate 61 and 62 relative to the optical axis 10. It is driven by a rotary drive device 66 which is rotatably supported by the rotary drive device 66. The image shift mechanism drive device 65 and the rotation drive device 66 are controlled by the system controller 67.

FIG. 21 shows the principle of image shift by the image shift mechanism 60. The incident light is transmitted through the optical path 63 by inclining the birefringent plates 61 and 62.
Is changed, and the image formation position on the CCD 14 is shifted by Δ. In addition, the transmission band can be made variable by relatively rotating the two birefringent plates 61 and 62 about the optical axis 10.

In the embodiment shown in FIG. 20, when shooting at the first resolution, a control signal is sent from the system controller 67 to the rotary drive device 66 and the image shift mechanism drive device 65, and the rotary drive device 66 is sent by the control signal.
Rotates the birefringent plates 61 and 62 relative to each other about the optical axis 10 and sets the transmission band of light incident on the birefringent plates 61 and 62 of the image shift mechanism 60 to the first transmission band in which moire does not occur. Is stopped at a predetermined position. Further, the image shift mechanism driving device 65 is used to drive the birefringent plates 61, 62.
However, it is stopped at a position substantially perpendicular to the optical axis 10. The incident light from the subject is the lens group 11 and the birefringent plate 6
An image is formed on the image pickup surface of the CCD 14 through the light beams 1, 62.
The formed image is taken out as a signal and processed by the signal processing circuit 18 to generate a video signal. The captured image at this time is stored in the image memory and output as a still image. Also, as in the conventional case, a CRT is used as a video signal.
It can also be output as a moving image that is displayed on the screen.

When shooting at a second resolution which allows an image to be obtained at a higher resolution than the first resolution, a control signal from the system controller 67 is sent to the rotary drive device 6.
6, the birefringent plates 61 and 62 of the image shift mechanism 60 are relatively rotated about the optical axis 10 by the rotation driving device 66. The birefringent plates 61 and 62 stop at a predetermined position, which is a second transmission band that is a frequency band higher than the first transmission band as a transmission band of incident light. next,
The system controller 67 sends a control signal to the image shift mechanism driving device 65, the signal processing circuit 18 and the CCD 14 and the image shift mechanism 6 for each frame photographing.
Inclining the birefringent plates 61 and 62 of 0 with respect to the optical axis 10,
The image forming position is moved to two or four positions on the CCD 14, and the image data at each position is combined using the signal processing circuit 18, and the sampling interval is shorter and the resolution is higher than that of the image of the first resolution. The control is performed so as to generate the image data of the resolution.

The image shift mechanism 60 includes a birefringent plate 61,
The principle that the first and second transmission bands can be switched by the relative rotation of 62 is the same as that of the birefringent plates 20 and 21 of the spatial filter 12 in the embodiment of FIG. To do. Regarding the image shift, the optical axis 10 which enters both the birefringent plates 61 and 62
The birefringent plate 61,
It is also possible to make one of the members 62 tiltable with respect to the optical axis 10 and perform the image shift.

As in this embodiment, the birefringent plates 61, 62
The image shift mechanism 60 is configured by the above, and if the image shift is performed by inclining with respect to the optical axis 10 so as to pass the high frequency component, it is necessary to make the spatial filter and the image shift mechanism as separate mechanisms. Therefore, the number of parts can be reduced. In addition, since the spatial filter and the image shift mechanism can be realized together only by rotating and tilting the spatial low-pass filter of the optical system that has been conventionally used for video movies, etc., the image shift mechanism is inserted separately. It is also possible to prevent an increase in back focus due to this, and it is possible to realize a compact optical system. Further, since it is not necessary to attach / detach or replace a plurality of spatial filters, or to compensate for the optical system, it is possible to suppress an increase in the size of the mechanism and the number of parts. Further, the birefringent plate 6
Since the components of the spatial filter used in the current video movie can be used for Nos. 1 and 62, it is possible to prevent an increase in manufacturing cost due to the use of new components.

[0047]

As described above, according to the present invention, the spatial filter can be switched so that the transmission band of the spatial frequency of the incident light is at least two types, and the first spatial filter is used when an image having the first resolution is input. Since the spatial filter is the second transmission band capable of transmitting a spatial frequency higher than the first transmission band when an image having a second resolution higher than the first resolution is input, Images with different resolutions can be input with the spatial filter inserted. Since the transmission band can be switched with the same spatial filter, the space for movement required for switching can be reduced, the image sensor can be made smaller and lighter, and it can be combined with image shift and other mechanisms. Images with high resolution can also be satisfactorily obtained.

Further, according to the present invention, since the image shift can be performed by inclining the transparent flat refracting plate with respect to the optical axis, the resolution less than the pixel arrangement pitch of the image pickup device can be easily achieved. Can be configured.

Furthermore, according to the present invention, the optical path incident on the image pickup device is shifted so that the second resolution having a higher resolution than the first resolution is obtained.
A plurality of image shifters for generating an image having a resolution and a spatial filter capable of switching the transmission band between the first transmission band and the second transmission band corresponding to the first and second resolutions. Since it can be performed by inclining and relative rotating one of the birefringent plates, the image shift means and the spatial filter can be configured as one mechanism. Therefore, it is possible to reduce the number of components and prevent an increase in back focus due to the insertion of the image shift mechanism, and it is possible to realize a compact optical system.

Further, according to the present invention, since the image having the first resolution is a moving image, it is possible to obtain a smooth moving image by using the images continuously formed by the image pickup device. Therefore, it is possible to take two types of images, a moving image and a high-resolution still image, with one image pickup device, which is convenient for the user.

Further, according to the present invention, since the spatial filter can switch the transmission band by the relative rotation of two or more birefringent plates, it is a component of the conventional spatial filter. Utilizing a certain birefringent plate,
It can be easily formed. Further, since it is not necessary to replace the spatial filter according to a plurality of resolutions, the resolution switching mechanism is simplified and the required space may be small.
It is possible to prevent an increase in the manufacturing cost of the image input device.

Further, according to the present invention, the transmission band can be switched only by changing the relative rotation angle between the birefringent plates by about 45 degrees, so that the moving distance of the mechanism for switching is small and the transmission band is small. It is possible to quickly switch between the two and to improve the durability of the mechanism.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a simplified perspective view showing a configuration of a spatial filter 12 in the embodiment shown in FIG.

FIG. 3 is a birefringent plate 2 in the spatial filter 12 of FIG.
It is a projection figure which shows the azimuth | direction of the optical axis of 0,21.

FIG. 4 is a birefringent plate 2 having an optical axis with the orientation shown in FIG.
FIG. 3 is a view showing a separation state when incident light is imaged on an image pickup surface of CCD 14 by 0 and 21.

5 is a graph showing a transmission band of the spatial filter realized by the combination of the optical axes of FIG.

FIG. 6 is a projection view showing the direction of an optical axis for making a second transmission band that allows transmission to a frequency band higher than the first transmission band in the spatial filter of FIG.

FIG. 7: Incident light corresponds to the projection of the optical axis in FIG.
It is a figure which shows the isolation | separation state at the time of focusing on 14.

8 is a graph showing a transmission band of the spatial filter obtained corresponding to the arrangement of the optical axes in FIG.

9 is a simplified front view showing an example of the configuration of the spatial filter driving device 16 for rotating the birefringent plate 21 in the embodiment of FIG. 1. FIG.

10 is a front view showing another example of the configuration of the spatial filter driving device 16 for rotating the birefringent plate 21 that constitutes the spatial filter 12 of FIG.

FIG. 11 is a spatial filter driving device 16 for rotating the birefringent plate 21 of the spatial filter 12 in the embodiment of FIG.
6 is a simplified front view showing a state in which one transmission band is obtained by still another configuration of FIG.

FIG. 12 is a simplified front view showing a state where the spatial filter driving device 16 shown in FIG. 11 has the other transmission band.

13 is a simplified front view showing still another configuration of the spatial filter driving device 16 for rotating the birefringent plate 21 of the spatial filter 12 in the embodiment of FIG. 1. FIG.

14 is a projection diagram on the yz plane showing another example for realizing the first transmission band in the direction of the optical axes of the birefringent plates 20 and 21 shown in FIG.

FIG. 15 is a diagram showing a state of separation of incident light obtained corresponding to the optical axis arrangement of FIG. 14 by image formation on the CCD.

16 is a projection diagram on the yz plane showing still another example of the directions of the optical axes of the birefringent plates 20 and 21 of FIG.

FIG. 17 is a diagram showing a state of separation of incident light obtained corresponding to the optical axis shown in FIG. 16 by image formation on the CCD.

18 is a projection diagram on the yz plane showing the azimuth of the optical axis when the birefringent plate having the azimuth of the optical axis shown in FIG. 16 is rotated to realize the second transmission band.

FIG. 19 shows a state in which the azimuth of the optical axis shown in FIG.
It is a figure which shows the isolation | separation state when incident light forms an image.

FIG. 20 is a block diagram showing a schematic configuration of an image input device according to another embodiment of the present invention.

21 is a simplified side view showing the principle of image shift by the image shift mechanism 60 in the embodiment of FIG.

FIG. 22 is a simplified side view showing the principle of performing image shift by tilting a conventional refraction plate.

FIG. 23 is a simplified front view showing an arrangement state of photosensitive units of an image sensor.

FIG. 24 is a simplified front view showing an arrangement state of photosensitive units of an equivalent image pickup device whose resolution is increased by image shifting.

FIG. 25 is a simplified front view showing an arrangement state of photosensitive units of an equivalent image pickup device whose resolution is increased by image shifting.

FIG. 26 is a simplified front view showing an arrangement state of photosensitive units of an equivalent image pickup device whose resolution is increased by image shifting.

FIG. 27 is a block diagram showing a schematic configuration of an image input device including a spatial filter according to the prior art.

[Explanation of symbols]

 10 Optical Axis 11 Lens Group 12 Spatial Filter 13,60 Image Shift Mechanism 14 CCD 15,65 Image Shift Mechanism Driving Device 16 Spatial Filter Driving Device 17,67 System Controller 18 Signal Processing Circuit 20, 21, 61, 62 Birefringent Plate 22 Refraction plate 30, 40, 50 Holding member 31, 41, 51 Rotating roller 32, 42 Protrusion 33, 43 Lever 34 Torsion spring 35, 45 Groove 36, 46 Pin 37, 53 Motor 44 Tension spring 47 Plunger 52 Worm gear 54 Wheel gear part 63 optical path 66 rotation drive device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Okuda 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Co., Ltd. Within the corporation

Claims (6)

[Claims] 1. An image shift means for displacing a relative positional relationship between an optical path incident on an image sensor and the image sensor,
The first resolution and the first by the image shifting means
In an image input device capable of inputting an image having a second resolution higher than the resolution of, the space of the incident light is provided between the optical system for inputting the incident light from the subject and the image sensor for capturing the image of the subject. A spatial filter capable of switching at least two kinds of frequency pass bands, and a control means, wherein the spatial filter becomes the first pass band and has the second resolution when an image having the first resolution is input. At the time of image input, the spatial filter becomes a second transmission band capable of transmitting a spatial frequency higher than the first transmission band, and the image shift means operates to synchronize with the deviation of the optical path incident on the image sensor. An image input device comprising: a control unit that controls so that a plurality of images can be input. 2. The image shift means is provided between an optical system for inputting incident light from a subject and an image pickup device for taking in an image from the subject, and is incident on the image pickup device while being inclined with respect to an optical axis. The image input device according to claim 1, further comprising a transparent flat plate-shaped refraction plate capable of shifting an optical path. 3. An image shift means for displacing a relative positional relationship between an optical path incident on the image sensor and the image sensor,
The first resolution and the first by the image shifting means
In the image input device capable of inputting an image having a second resolution higher than that of, the image shift means is provided between an optical system for inputting incident light from a subject and an image sensor for capturing an image of the subject. The image pickup device can operate as a spatial filter capable of switching the transmission band of the spatial frequency of the incident light into at least two types, and as the image shift means, a part of the spatial filter is inclined with respect to the optical axis. The control means is configured so as to shift the optical path incident on the optical path, and the spatial filter serves as the first transmission band when an image having the first resolution is input, and the spatial filter is used when an image having the second resolution is input. The filter becomes a second transmission band capable of transmitting a spatial frequency higher than the first transmission band, operates as an image shift means, and enters the image sensor. In synchronism with the displacement of the Ruhikariro image input apparatus characterized by comprising control means for controlling so that a plurality of images can be input. 4. The image input device according to claim 1, wherein the image having the first resolution is a moving image. 5. The spatial filter is configured to include at least two or more birefringent plates that are supported so as to be rotatable relative to each other about an axis parallel to the optical axis. The image input device according to any one of claims 1 to 4, wherein the image input device is switchable to the first and second transmission bands by various rotations. 6. The relative rotation angle between the birefringent plates is
The image input device according to claim 5, wherein the first transmission band and the second transmission band are changed by about 45 degrees.