JP2005072778A - Optical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide optical equipment for electrically controlling an optical low-pass effect. <P>SOLUTION: The optical equipment comprises an optical element (4) that is changed by deforming the incident position of rays to an imaging element (10) for converting an optical image to an electric signal for outputting, and a control means for controlling the drive of the optical element. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical apparatus such as a digital still camera that can electrically control an optical low-pass filter effect.

  The digital still camera has an image sensor that converts photographing light into an electrical signal, and reproduces a subject image by performing image processing on a photoelectric conversion signal output from the image sensor. Since the plurality of pixels constituting the photoelectric conversion unit of the image sensor are regularly arranged, a spatial frequency (Nyquist) determined by the pixel arrangement period (pixel pitch) of the image sensor on the subject image formed on the image pickup surface. If an image having a spatial frequency higher than (frequency) is included, moiré or false color occurs in the reproduced subject image.

  For this reason, in general, a digital still camera is provided with an optical low-pass filter made of crystal, lithium niobate, or the like in a photographing optical path, and moiré or false color is generated by separating a photographing light flux and guiding it to an image sensor. It is preventing. FIG. 24 shows the MTF characteristics of an optical low-pass filter using crystal, and the MTF of the Nyquist frequency determined by the pixel period of the image sensor is almost zero.

On the other hand, there is an imaging apparatus in which a plurality of liquid crystal plates whose birefringence can be switched is provided in a photographing optical path and the optical low-pass effect is variable (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 6-292093 (paragraph number 0042, FIGS. 1 and 2)

  However, if an optical low-pass filter such as a crystal is arranged in the photographing optical path of an optical device such as a digital still camera, there is a drawback that the subject image is blurred due to this optical low-pass effect and the resolution is lowered. Further, since some users may want to prioritize resolution over the optical low-pass effect, a configuration that always generates the optical low-pass effect cannot meet the above-described user's request.

  Here, in the imaging device disclosed in Patent Literature 1, the optical low-pass effect can be generated or not generated by controlling the voltage to each liquid crystal plate on / off.

  However, this imaging apparatus has a drawback that the resolution of the subject image is lowered due to the scattering characteristics of the liquid crystal plate. Also, in order to obtain the optical low-pass effect, in order to efficiently change the traveling direction of ordinary light and extraordinary light, the orientation direction of all liquid crystal molecules on the liquid crystal plate must be maintained at 45 ° with respect to the optical axis. However, this orientation control is very difficult. Furthermore, since the liquid crystal plate is usually composed of two substrate glasses and is thick, there is a drawback that the liquid crystal plate cannot be arranged in the photographing optical path due to the layout depending on the camera model.

  An optical apparatus according to the present invention includes an optical element that changes an incident position of a light beam on an imaging element that converts an optical image into an electric signal and outputs the electric signal, and a control unit that controls driving of the optical element. It is characterized by that.

  Here, the optical element can be periodically deformed in a specific direction by the drive control of the control means. For example, a surface wave that periodically changes or a traveling wave can be generated in the optical element. When a traveling wave is generated, it is preferable that the traveling wave travels at least one wavelength during imaging with the image sensor.

  Then, by changing the drive timing of the optical element, the optical element can be periodically deformed in different directions. For example, the optical element can be periodically deformed in an arrangement direction of specific pixels in the imaging element and a direction having a predetermined angle with respect to the arrangement direction (for example, a direction orthogonal to the arrangement direction).

  The optical element can be composed of a piezoelectric transparent substrate, or a piezoelectric thin film can be provided on the surface of the transparent substrate. If a predetermined voltage is applied (electrically controlled) to the piezoelectric transparent substrate or thin film from the control means, the transparent substrate can be periodically deformed.

  On the other hand, a mode setting unit that can be set to a first imaging mode in which an optical element is deformed to perform imaging with the imaging element and a second imaging mode in which imaging with the imaging element is performed without deforming the optical element. Can be provided.

  In addition, a first imaging mode in which an optical element is deformed to perform imaging with the imaging element based on an output of the imaging element, and a second imaging mode in which imaging with the imaging element is performed without deforming the optical element. It is also possible to set one of the imaging modes.

  According to the first aspect of the present invention, the optical element is repeatedly deformed to change the arrival position of the light beam incident on the image sensor on the surface of the image sensor, thereby causing an optical low-pass effect to be captured by the image sensor. It is possible to prevent moiré and false colors from appearing in the image. In addition, since the present invention only deforms the optical element, it is not necessary to use a plurality of substrate glasses as in the background art, and the optical element can be thinned. Therefore, the optical element can be arranged without being limited to the layout for each model of the optical device.

  If the incident position of the light beam is not changed in a state where the optical element is not deformed, an image with high resolution can be obtained without producing the optical low-pass effect. By deforming or not deforming the optical element in this way, it is possible to obtain an image that exhibits the optical low-pass effect, or to obtain an image with a high resolution. Can be matched.

  Here, if the optical element is periodically deformed in a specific direction, for example, the arrangement direction of the pixels of the imaging element (if a surface wave or a traveling wave that periodically changes is generated), the pixel of the imaging element An optical low-pass effect corresponding to the periodic structure can be obtained.

  According to the invention described in claim 4 of the present application, by performing at least one wavelength of the traveling wave generated in the optical element during imaging with the imaging element, the spread of the image separated on the imaging element is increased. Variations can be suppressed and a good optical low-pass effect can be obtained.

  According to the invention described in claim 5 of the present application, by providing the optical apparatus with mode setting means for setting the first imaging mode and the second imaging mode, the user can appropriately select the imaging mode via the mode setting means. Can be switched.

  According to the sixth aspect of the present invention, since one of the first imaging mode and the second imaging mode is automatically selected and set based on the output of the imaging device, the user sets the imaging mode. The complexity of doing so can be eliminated.

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

  FIGS. 1-16 is a figure for demonstrating the camera (optical apparatus) which is Example 1 of this invention.

  FIG. 1 is a schematic configuration diagram of the camera of this embodiment. In the figure, reference numeral 10 denotes an image pickup device such as a CCD or CMOS image sensor, which is disposed on the planned image planes of the taking lenses 5a and 5b in the digital still camera 1. The photographing lenses 5a and 5b move in the direction of the optical axis to perform a zooming operation and a focus adjustment operation of the photographing optical system. An optical low-pass filter (optical element) 4 is disposed in the vicinity of the subject side (left side in FIG. 1) with respect to the imaging element 10 in a state of being fixed in the photographing optical path.

  A shutter 2 also serves as an aperture. A liquid crystal display element 9 displays a subject image obtained by the image sensor 10. Thus, the photographer can observe the subject image displayed on the liquid crystal display element 9 via the eyepiece 3. In FIG. 1, the photographic lens is shown as two lenses 5a and 5b for convenience, but it is actually composed of a plurality of lenses.

  FIG. 2 is an electric circuit block diagram of the camera 1. The CPU 20 controls the operation of the entire camera. The lens drive circuit 26 drives the photographing lens 5 based on the output of the CPU 20, and the shutter control circuit 28 controls the drive (exposure time and aperture diameter) of the shutter 2 based on the output of the CPU 20.

  The surface acoustic wave generating circuit 27 causes the optical low-pass filter 4 to exhibit an optical low-pass effect based on the output of the CPU 20, and will be described in detail later. The image sensor control circuit 21 controls driving (image accumulation and readout) of the image sensor 10 based on the output of the CPU 20.

  The image processing circuit 24 performs image processing (color processing, gamma correction, etc.) on the image signal read from the image sensor 10, and the liquid crystal display element driving circuit 25 is based on the output of the CPU 20. Drive. The memory circuit 22 records image data picked up by the image pickup device 10, and the interface circuit 23 outputs the image data processed by the image processing circuit 24 to the outside of the camera (PC, printer, etc.).

  The signal input circuit 29 confirms the setting state of various switches and outputs it to the CPU 20. Specifically, the state of SW1 and SW2 that are turned on / off by the operation of a release button provided on the camera 1 and the operation state of a mode dial 19 described later provided on the camera 1 are confirmed and output to the CPU 20.

  FIG. 3 is a front view of the image sensor 10 mounted on the camera 1, and pixels having photoelectric conversion units are periodically arranged in the X direction and the Y direction in the drawing. In this embodiment, the X direction in the figure is defined as the pixel array direction.

  FIG. 4 is a front view of the optical low-pass filter 4 in this embodiment. The optical low-pass filter 4 includes a piezoelectric transparent substrate 41 made of an oxide single crystal such as quartz, lithium tantalate, or lithium niobate, and a region surrounded by a dotted line in the figure of the piezoelectric transparent substrate 41 (photographing by the image sensor 10). Comb electrodes 42 (42a, 42b) and 43 (43a, 43b) provided outside the region corresponding to the effective region.

  The piezoelectric transparent substrate 41 is cut so that the optical axis is in the plane. The comb electrode 42 is an electrode for generating a surface acoustic wave in a direction (Y direction) orthogonal to the pixel arrangement direction (X direction) of the image sensor 10, and the comb electrode 43 is a pixel arrangement direction ( This is an electrode for generating surface acoustic waves in a direction (X direction) parallel to the (X direction). Each of the electrodes 42 and 43 is made of AL and is connected to the surface acoustic wave generation circuit 27.

  According to the present embodiment, since the optical low-pass filter 4 is composed of a single piezoelectric transparent substrate 41, the thickness can be reduced as compared with a conventional substrate composed of a plurality of substrate glasses. It can be arranged in the photographing optical path regardless of the camera model.

  The operation of the camera will be described below using the flowchart of FIG.

  When the photographer turns on a main switch (not shown in FIG. 1) provided in the camera 1 (S101), the camera 1 returns from the standby state. First, the CPU 20 sends an image pickup signal to the image pickup device control circuit 21 to cause the image pickup device 10 to pick up an image for an electronic viewfinder (EVF) (S102).

  The image sensor 10 is controlled by the image sensor control circuit 21 so that an image having the number of pixels thinned out at a predetermined ratio with respect to all pixels is output. At this time, the optical low-pass filter 4 is not driven by the surface acoustic wave generation circuit 27 (no voltage is supplied to the comb-shaped electrodes 42 and 43). It acts as a transparent substrate that does not refract the photographic light.

  As described above, when an image for EVF is taken, the surface acoustic wave is not generated, thereby minimizing the power consumption.

  The image data output from the image sensor 10 is processed into EVF image data by the image processing circuit 24 and then sent to the liquid crystal display element driving circuit 25. The liquid crystal display element drive circuit 25 that has received the image data via the CPU 20 drives the liquid crystal display element 9 to display the captured image (EVF display) (S103).

  When it is detected through the signal input circuit 29 that the release switch SW1 is turned on by operating the release button of the photographer (S104), the CPU 20 of the camera 1 detects the focus adjustment state of the photographing optical system (S105). . The camera 1 of this embodiment detects the focus adjustment state by a known contrast method.

  The CPU 20 having a function of detecting the focus adjustment state of the photographing lens 5 based on the output of the image sensor 10 calculates the contrast of the image previously captured by the image sensor 10 as an AF evaluation value. If the contrast of the image is low and the AF evaluation value is smaller than a predetermined AF determination level, the CPU 20 determines that the taking lens 5 is not in focus (S106) and sends a lens drive signal to the lens drive circuit 26. The photographing lens 5 is driven to a predetermined in-focus position (S111).

  On the other hand, when the contrast of the image obtained by the image sensor 10 is high and the AF evaluation value is higher than a predetermined AF determination level, the CPU 20 determines that the photographing lens 5 is in focus (S106). It is checked whether or not the release switch SW2 is in an ON state via the signal input circuit 29. If SW2 is in the ON state (S107), imaging for recording the main image in the memory circuit 22 is performed (S108).

  Here, the imaging operation of the main image of the camera 1 will be described using the flowchart of FIG. 6 and the timing chart of FIG.

  The CPU 20 starts capturing the main image by the image sensor 10 by sending an image signal to the image sensor control circuit 21 in response to the SW2 being turned on (S120). The image sensor control circuit 21 sends an image control signal Sens to the image sensor 10 to control driving of the image sensor 10. Next, the CPU 20 opens the shutter 2 by sending exposure information (shutter speed and aperture value) to the shutter control circuit 28 (S121).

  The shutter control circuit 28 controls the operation of the shutter 2 by sending a shutter control signal SH to the shutter 2. At this time, since the shutter 2 also serves as a diaphragm, the operation of the shutter 2 is controlled so as to have a predetermined aperture diameter corresponding to the subject brightness detected by the output of the image sensor 10.

  Further, the CPU 20 confirms the setting state of the mode dial 19 for selecting the photographing mode via the signal input circuit 29. As shown in the mode dial explanatory diagram of FIG. 7, the mode dial 19 is provided so as to be rotatable with respect to the camera 1.

  When the “on” displayed on the surface of the mode dial 19 is adjusted to the “LPF” index by rotating the mode dial 19, an optical low-pass effect shooting mode (first low-pass effect) is produced by the optical low-pass filter 4. Imaging mode). Further, when the display of “off” is matched with the index “LPF”, it is possible to set to a high-resolution imaging mode (second imaging mode) for obtaining an image with a high resolution without exhibiting the optical low-pass effect. . Further, when the display of “auto” is matched with the index “LPF”, it is possible to set the automatic selection mode in which the camera 1 automatically selects one of the optical low-pass effect shooting mode and the high-resolution shooting mode. it can.

  By operating the mode dial 19, the photographer can arbitrarily switch on / off the optical low-pass effect in the optical low-pass filter 4 according to the subject, and can set the automatic selection mode for the camera 1. . In this embodiment, the shooting mode is selected using a dial-type operation member. However, the shooting mode information may be input by a button operation or voice.

  According to the present embodiment, the optical low-pass effect can be exhibited or not manifested by the operation of the mode dial 19, so that it is possible to meet the demand of the photographer.

  If the photographer has set the automatic selection mode by operating the mode dial 19 (S122), the process proceeds to step S124. If the photographer has not been set to the automatic selection mode, the process proceeds to step S123.

  If the optical low-pass effect photographing mode is set (S124), the imaging operation is performed in the photographing mode in which the surface acoustic wave is generated in the optical low-pass filter 4 to obtain the optical low-pass effect. That is, the CPU 20 sends a signal to the surface acoustic wave generation circuit 27 to cause the optical low-pass filter 4 to generate a surface acoustic wave (S125).

  As shown in the timing chart of FIG. 8, the surface acoustic wave generating circuit 27 applies an AC voltage between the comb-shaped electrodes 43a and 43b at the timing of SAW_X, and applies an AC voltage between the comb-shaped electrodes 42a and 42b at the timing of SAW_Y. To do. In this embodiment, as shown in FIG. 8, the surface acoustic wave is generated three times in the pixel arrangement direction (X direction in FIG. 3) of the image pickup element 10 during the exposure time when the shutter 2 is open, and the image pickup is performed. The surface acoustic wave is generated three times in a direction (Y direction in FIG. 3) orthogonal to the pixel array direction (X direction) of the element 10.

  Here, the SAW_X and SAW_Y drive signals output from the surface acoustic wave generation circuit 27 to the comb-shaped electrodes 42 and 43 have the same period and are output at different timings. Are generated independently in the two axial directions (X and Y directions) of the optical low-pass filter 4.

  FIG. 9 shows the state of the photographing light beam when a surface acoustic wave is generated in the optical low-pass filter 4.

  When an AC voltage is applied between the comb-shaped electrodes 42a and 42b deposited on the surface of the piezoelectric transparent substrate 41 from the surface acoustic wave generating circuit 27, the surface of the piezoelectric transparent substrate 41 on which the comb-shaped electrode 42 is formed is shown in FIG. A progressive surface acoustic wave is generated in the Y direction.

  The wavelength and amplitude of the surface acoustic wave are determined by the distance between the optical low-pass filter 4 and the image sensor 10, the refractive index of the piezoelectric transparent substrate 41 such as lithium niobate, and the width of the image to be separated. If the pixel pitch of the image sensor 10 is 5 μm, an image separation width of about 5 μm corresponding to the pixel pitch is required on the image sensor 10 in order to obtain a desired optical low-pass effect. Here, when the distance between the optical low-pass filter 4 and the image sensor 10 is set to about 6 mm, an image separation of about 5 μm can be performed by generating a surface acoustic wave having a wavelength of 400 μm and an amplitude of 20 nm. At this time, the interval between the comb electrode 42a and the comb electrode 42b may be set to 200 μm.

  In FIG. 9A, the light beam passing through the concave vertex of the surface acoustic wave goes straight without being refracted by the optical low-pass filter 4 and enters the pixel at the position (I) in the image sensor 10. Here, 13 is a microlens, 12 is a color filter, 11 is a photoelectric conversion unit, and these members are provided corresponding to each pixel.

  FIG. 9B shows a state in which the surface acoustic wave travels a quarter wavelength from the state of FIG. At this time, since the light beam incident on the same position of the piezoelectric transparent substrate 41 (the same light beam as shown in FIG. 9A) is emitted from the middle of the surface acoustic wave, it receives a refracting action and is positioned in the image sensor 10. The light enters the pixel adjacent to the pixel (II), that is, the pixel at the position (I) in the Y (−) direction.

  FIG. 9C shows a state in which the surface acoustic wave travels a quarter wavelength from the state of FIG. 9B. At this time, since the light beam (the same light beam as described above) incident on the same position of the piezoelectric transparent substrate 41 is emitted from the convex vertex of the surface acoustic wave, the light beam travels straight without being refracted and the position of the image sensor 10 ( It enters the pixel of I).

  FIG. 9D shows a state in which the surface acoustic wave travels a quarter wavelength from the state of FIG. At this time, since the light ray (same light ray as described above) incident on the same position of the piezoelectric transparent substrate 41 is emitted from the middle of the surface acoustic wave, the pixel at the position (III) in the image sensor 10 due to the refracting action, that is, , Incident on the pixel adjacent to the pixel at the position (I) in the Y (+) direction.

  The propagation speed of the surface acoustic wave propagating through the piezoelectric transparent substrate 41 made of lithium niobate is about 4000 m / s. Actually, the surface acoustic wave has about 5 wavelengths during the exposure time when the shutter 2 is open (exposure time). Progress). Therefore, during the exposure time, the light beam changes in the states of FIGS. 9A to 9D and FIGS. 9D to 9A and is scanned about 5 times on the image sensor 10.

  Here, if the surface acoustic wave travels at least one wavelength during the exposure time, the light beam can be reciprocated once, so that image separation corresponding to the pixel pitch can be performed and variation in the spread of the light beam is reduced. Can do.

  FIG. 9 shows the state of light rays when the surface acoustic wave travels in the Y direction. As described above, the surface acoustic wave in the X direction of the optical low-pass filter 4 is independent of the surface acoustic wave in the Y direction. Since the surface acoustic wave is generated, the photographing light beam exhibits the same behavior as in FIG. 9 in the X direction.

  FIG. 10 shows a separated image on the image sensor 10 of a single photographic light beam when surface acoustic waves are generated in the optical low-pass filter 4. A thick line in the figure indicates the image on the image sensor 10. The locus of the incident position of the photographing light beam is shown.

  Here, the intersection of the Y-axis and the X-axis corresponds to the position (I) in FIG. 9, the end in the Y (−) direction among the thick lines in the Y direction corresponds to the position (II) in FIG. The end in the (+) direction corresponds to the position (III) in FIG. FIG. 10 shows that the images are separated with a width of about 5 μm in the Y direction and the X direction.

  FIG. 11 shows the intensity distribution of the separated image of one photographing light beam when surface acoustic waves are generated in the optical low-pass filter 4.

  In the vicinity of the top of the sine wave surface acoustic wave, the rate of change in the slope of the wave with respect to the position is large (the slope of the tangent of the wave changes greatly on both sides of the top of the wave). The scanning speed on the image sensor 10 of a photographic light beam having a small refraction angle is refracted. On the other hand, in the vicinity of the sinusoidal surface acoustic wave, the rate of change in the slope of the wave with respect to the position is small (the change in the slope of the tangent in the middle of the wave is small). The scanning speed of a large photographic light beam on the image sensor 10 becomes slow.

  As a result, the separated image of the photographing light beam has a low intensity of the photographing light beam having a small refraction angle (a central region in the intensity distribution of FIG. 11) and a high intensity of the photographing light beam having a large refraction angle (both ends in the intensity distribution of FIG. 11). A separated image of the intensity distribution is obtained.

  FIG. 12 shows the MTF characteristic of the optical low-pass filter when the intensity distribution of the separated image of the photographing light beam as shown in FIG. 11 is obtained.

  By generating a progressive surface acoustic wave in the optical low-pass filter 4 as in the present embodiment, as shown in the intensity distribution of the separated image of the photographing light beam in FIG. It is not image separation but image separation on continuous lines. For this reason, as shown by the MTF characteristic in FIG. 12, the response of the spatial frequency component higher than the predetermined spatial frequency is lowered, which is a more preferable characteristic in terms of the optical low-pass effect.

  As a result, it is possible to prevent the occurrence of moiré and false colors that occur when a subject image including a spatial frequency component finer than a predetermined spatial frequency determined by the pixel arrangement period of the image sensor 10 can be prevented, and a high-quality image can be obtained. Can be obtained.

  In the flowchart of the imaging operation of FIG. 6, when a predetermined time (exposure time) has elapsed after the opening operation of the shutter 2, the CPU 20 sends a shutter close signal to the shutter control circuit 28 to drive the shutter 2 to close (S126). Further, the CPU 20 transmits an imaging end signal to the image sensor control circuit 21 and ends the imaging operation by the image sensor 10 (S127).

  On the other hand, if the photographer operates the mode dial 19 for selecting the photographing mode to set the high-resolution photographing mode (S124), the CPU 20 captures an image without generating surface acoustic waves in the optical low-pass filter 4. The element 10 is exposed.

  Since the optical axis of the piezoelectric transparent substrate 41 constituting the optical low-pass filter 4 is in the plane, the optical low-pass filter 4 functions as a general transparent substrate unless surface acoustic waves are generated in the optical low-pass filter 4. Image separation does not occur. When a predetermined time (exposure time) elapses after the opening operation of the shutter 2, the CPU 20 sends a shutter close signal to the shutter control circuit 28 to drive the shutter 2 to close (S126). Further, the CPU 20 transmits an imaging end signal to the image sensor control circuit 21 and ends the imaging operation by the image sensor 10 (S127).

  As described above, unless a surface acoustic wave is generated in the optical low-pass filter 4, a high-resolution image corresponding to the number of pixels of the image sensor 10 can be obtained.

  If the photographer operates the mode dial 19 for selecting the shooting mode to set the automatic selection mode (S122), the CPU 20 uses the AF evaluation value calculated from the captured image data as the optical low-pass effect determination level. Compare with The AF evaluation value here represents the contrast of the subject image. Further, when the contrast of the subject image is low, it is not necessary to develop the optical low-pass effect, and therefore the optical low-pass effect determination level is set in advance as a reference for performing this determination.

  When the AF evaluation value is lower than the optical low-pass effect determination level (S123), the CPU 20 performs an imaging operation in a shooting mode in which a high-resolution image can be obtained without generating surface acoustic waves in the optical low-pass filter 4.

  On the other hand, when the AF evaluation value is higher than the optical low-pass effect determination level (S123), the CPU 20 generates a surface acoustic wave in the optical low-pass filter 4 (S125), and performs an imaging operation in a shooting mode in which the optical low-pass effect is obtained. Do. The imaging operation for obtaining the optical low-pass effect by generating the surface acoustic wave in the optical low-pass filter 4 is as described above.

  In this way, by providing the camera with the automatic selection mode, it is possible to leave the camera to determine whether or not to generate the optical low-pass effect, thereby reducing the complexity of the camera operation of the photographer.

  When the image capturing operation of the main image is completed (S128), the image signal captured by the image sensor 10 is A / D converted by the image sensor control circuit 21, and then subjected to image processing by the image processing circuit 24. At this time, predetermined image processing is performed for color reproduction based on an output signal from the image sensor 10.

  Then, the image signal subjected to the predetermined image processing is sent to the liquid crystal display element driving circuit 25 through the CPU 20 and displayed on the liquid crystal display element 9 (S109 in FIG. 5). As a result, the photographer can observe the subject image (main image) displayed on the liquid crystal display element 9 through the eyepiece 3. At the same time, the CPU 20 stores the captured image signal as it is in the memory circuit 22 of the camera 1 (S110).

  When the photographing operation is completed and the photographer turns off the main switch (S101), the camera is turned off and enters a standby state (S112).

  In this embodiment, independent surface acoustic waves are generated in a direction parallel to and perpendicular to the pixel arrangement direction (X direction) of the image sensor 10, and the photographing light beam is linear in the X direction and the Y direction. Although the case of performing image separation has been described, the present invention is not limited to this.

  Specifically, as shown in the timing chart of FIG. 13, between the AC voltage V43a-43b applied between the comb electrode 43a and the comb electrode 43b of the optical low-pass filter 4, and the comb electrode 42a and the comb electrode 42b. By changing the AC voltage V42a-42b applied to the voltage so that the polarity is reversed within the same period, in the two-axis directions of the X-axis direction and the Y-axis direction as shown in the separation image explanatory diagram of FIG. The image can be separated and the image can also be separated in the direction of ± 45 ° with respect to the X axis.

  As a result, the influence of moire and false colors on the periodic structure in the ± 45 ° direction with respect to the X direction in the pixel array of the image sensor 10 can be removed, compared with the case where the images are separated in the X direction and the Y direction. Further, it becomes possible to obtain an image with high quality.

  In the present embodiment, an example in which a progressive surface acoustic wave is generated by providing the comb electrode 42 and the comb electrode 43 on two sides orthogonal to each other among the four sides of the optical low-pass filter 4 is shown. A surface acoustic wave as a standing wave may be generated on the transparent substrate 41. In this case, an optical low-pass effect can be obtained.

  Specifically, as shown in the optical low-pass filter explanatory diagram of FIG. 15, the comb-shaped electrode is located at a position facing the comb-shaped electrode 42 with a region surrounded by a dotted line (a region corresponding to a photographing effective region of the image sensor 10) interposed therebetween. 45 (45a, 45b) is provided, and surface acoustic waves (standing waves) in the Y direction can be generated by applying AC voltages having different phases to the comb electrodes 42, 45 by the surface acoustic wave generating circuit 27. it can. Further, by providing comb electrodes 44 (44a, 44b) at positions facing the comb electrodes 43 across the area surrounded by the dotted line, and applying alternating voltages having different phases to the comb electrodes 43, 44, the X direction Surface acoustic waves (standing waves) can be generated.

  FIG. 16 is an explanatory diagram of the imaging light flux that passes through the optical low-pass filter 4 shown in FIG. Reference numeral 40 denotes a transparent substrate made of quartz or the like, and a piezoelectric transparent thin film 41 made of ZnO is deposited on the transparent substrate 40.

  FIG. 16A shows the state of the photographing light beam when no voltage is applied to the comb electrodes 42 and 45. The subject luminous flux that has passed through the photographing lens (5a, 5b in FIG. 1) is emitted without being bent by the optical low-pass filter 4 and converges in the vicinity of the microlens 13 of the image sensor 10. Here, as shown in FIG. 16A, the plurality of light rays reach a specific position on the image sensor 10.

  On the other hand, FIG. 16B shows the state of the photographing light beam when AC voltages having different phases are applied to the comb electrodes 42 and 45. When alternating voltages having different phases are applied to the comb-shaped electrodes 42 and 45, standing waves of surface acoustic waves are generated in the piezoelectric transparent thin film 41 formed on the transparent substrate 40.

  The light beam that passes through the region other than the top of the standing wave among the subject luminous flux that has passed through the photographing lens is bent and emitted by the standing wave of the surface acoustic wave generated on the exit surface of the optical low-pass filter 4 and imaged. It reaches the vicinity of the microlens 13 of the element 10. Further, the light beam that passes through the vertex of the standing wave enters the microlens 13 of the image sensor 10 without being refracted.

  At this time, each of the plurality of light beams transmitted through different regions of the pupil of the photographing lens has different exit positions from the standing wave of the surface acoustic wave, and therefore spreads to reach different positions on the image sensor 10. For this reason, even when a surface acoustic wave is generated as a standing wave, an optical low-pass effect can be obtained.

  In the present embodiment, an example in which the comb-shaped electrodes of the optical low-pass filter 4 are arranged in a direction parallel to and orthogonal to the pixel arrangement direction of the image sensor 10 to generate surface acoustic waves has been described. The optical low-pass filter 4 may be configured so that surface acoustic waves are generated in a 45 ° oblique direction with respect to the pixel arrangement direction. In this case, it is possible to remove moiré and false colors with respect to the periodic structure in the oblique 45-degree direction in the pixel array of the image sensor.

  Furthermore, in this embodiment, an example of a digital still camera is shown, but the present invention can also be applied to an optical apparatus such as a video camera, a measuring device with an image sensor, an image reading device, and the like.

  FIGS. 17-22 is a figure for demonstrating the camera system which is Example 2 of this invention. Here, FIG. 17 is a configuration diagram of the camera system in the present embodiment. The camera system according to the present embodiment includes a camera body 101 and a lens device 105 that is detachably attached to the camera body 101.

  In FIG. 17, reference numeral 110 denotes an image sensor such as a CCD or CMOS image sensor, which is disposed on the planned image planes of the photographing lenses 105 a and 105 b in the lens device 105 mounted on the camera body 1. The photographing lenses 105a and 105b perform a zooming operation and a focus adjustment operation of the photographing optical system by moving in the optical axis direction. An optical low-pass filter 104 is disposed in the vicinity of the subject side (left side in FIG. 17) with respect to the image sensor 10 in a state of being fixed in the photographing optical path.

  Reference numeral 102 denotes a focal plane shutter having a front curtain and a rear curtain made of a plurality of light shielding members, and is disposed between the optical low-pass filter 104 and the image sensor 110. Reference numeral 109 denotes a liquid crystal display element provided on the back surface of the camera body 101, which displays a subject image obtained by the image sensor 110. Thereby, the photographer can observe the subject image from the outside of the camera system.

  The lens device 105 is connected by a lens mount 50 provided on the front surface of the camera main body 101 so that data can be communicated between the lens device 105 and the camera main body 101. The photographing lenses 105a and 105b are shown as two lenses for the sake of convenience, but are actually composed of a large number of lenses.

  A stop 151 is disposed in the lens device 105, and the stop 151 adjusts the amount of subject light incident on the imaging surface by changing the diameter of the light passage opening.

  The flip-up mirror 106 can be moved back and forth with respect to the photographing optical path, and when it is obliquely installed in the photographing optical path, it reflects a part of the subject luminous flux transmitted through the photographing lenses 105a and 105b to the focus plate 107 side. The remaining light flux is guided to the focus detection unit 134.

  The subject light diffused by the focus plate 107 is optically converted by the penta roof prism 8 and then emitted from the eyepiece 3. Thereby, the photographer can observe the subject image through the eyepiece 3. The focus detection unit 134 detects the focus adjustment state of the photographing lens 5 by receiving the light guided from the flip-up mirror 6. The camera system of the present embodiment detects a focus adjustment state of the photographing optical system by a known pupil division phase difference method. The focus detection unit 134 includes a field lens (not shown), a secondary imaging lens, Members for detecting a focus adjustment state by a pupil division phase difference method, such as an aperture and an image sensor, are included.

  On the other hand, when the flip-up mirror 106 is retracted from the photographing optical path, the subject light transmitted through the photographing lenses 105a and 105b is directed toward the image plane side.

  In this embodiment, the configuration of the image sensor 110 mounted on the camera body 101 is the same as that of the image sensor 10 described in the first embodiment, and pixels having photoelectric conversion units in a two-dimensional direction (XY direction) are arranged. Arranged periodically. Also in this embodiment, the X direction is defined as the pixel arrangement direction. Further, the configuration of the optical low-pass filter 104 in the present embodiment is the same as that of the optical low-pass filter 4 described in the first embodiment (FIG. 4), and therefore detailed description thereof is omitted.

  FIG. 18 is an electric circuit block diagram of the camera system in the present embodiment.

  In FIG. 18, the camera body 101 is provided with a camera CPU 120 that controls the operation of the entire camera, and the lens device 105 is provided with a lens CPU 130 that controls the operation of the entire lens. The camera CPU 120 and the lens CPU 130 can communicate data with each other via the electrical contact 131.

  First, a circuit configuration in the camera body 101 will be described.

  The shutter control circuit 128 controls the driving of the shutter 102 based on the output from the camera CPU 20. The surface acoustic wave generation circuit 127 is for causing the optical low-pass filter 104 to exhibit an optical low-pass effect based on the output of the camera CPU 120, and will be described in detail later.

  The image sensor control circuit 121 controls driving (image accumulation and reading) of the image sensor 110 based on the output of the camera CPU 120. The image processing circuit 124 performs image processing (color processing, gamma correction, etc.) on the image signal captured by the image sensor 110, and the liquid crystal display element driving circuit 125 is based on the output of the camera CPU 120. Drive.

  The memory circuit 122 records the image data captured by the image sensor 110, and the interface circuit 123 outputs the image data processed by the image processing circuit 124 to the outside of the camera system (such as a PC or a printer).

  The signal input circuit 129 checks the setting state of various switches and outputs it to the camera CPU 120. Specifically, the state of SW1 and SW2 that are turned on / off by the operation of the release button provided on the camera body 101 and the operation state of the mode dial 119 provided on the camera body 101 are confirmed and output to the camera CPU 120. The focus detection circuit 133 controls driving of the focus detection unit 134.

  Here, the configuration of the mode dial 119 is the same as that of the mode dial 19 described in the first embodiment. In other words, by operating the mode dial 119, an optical low-pass effect shooting mode that exhibits an optical low-pass effect, a high-resolution shooting mode for obtaining a high-resolution image without exhibiting the optical low-pass effect, an optical low-pass effect shooting mode, and An automatic shooting mode in which the camera system automatically selects one of the high resolution shooting modes can be set.

  Next, a circuit configuration in the lens device 105 will be described.

  The lens driving circuit 126 controls the driving of the photographing lenses 105 a and 105 b based on the output of the lens CPU 130. The aperture control circuit 132 controls the driving of the aperture 151 based on the output of the lens CPU 130.

  Hereinafter, the operation of the camera system of this embodiment will be described with reference to the flowchart of FIG.

  When the photographer turns on a main switch (not shown in FIG. 17) provided on the camera body 101 (S201), the camera body 101 returns from the standby state. The camera CPU 120 checks whether the release switch SW1 (not shown) is in an ON state via the signal input circuit 129 (S202). When the photographer detects through the signal input circuit 129 that the SW1 is turned on by half-pressing a release button (not shown) (S202), the camera CPU 120 detects the focus adjustment state of the photographing optical system. Execute (S203). Specifically, based on the output from the focus detection unit 134, the focus adjustment state is detected by the pupil division phase difference method.

  The camera CPU 120 having a focus adjustment state detection function sends a focus detection signal to the focus detection circuit 133 and takes a pupil detection image for focus detection using the image sensor of the focus detection unit 134. Then, the defocus amount of the photographing lens 105 is calculated based on the relative positional deviation amount between the two captured pupil divided images.

  If it is determined that the photographing lens 105 is not in focus (S204), the camera CPU 120 sends a lens driving signal to the lens driving circuit 126 via the lens CPU 130 to drive the photographing lens 105 by an amount corresponding to the defocus amount. (S209).

  On the other hand, if it is determined that the photographic lens 105 is in focus (S204), the camera CPU 120 checks whether the release switch SW2 is in the ON state via the signal input circuit 129. If SW2 is on (S205), an imaging operation for recording the main image in the memory circuit 122 is performed (S206).

  Here, the imaging operation of the main image in the camera system of the present embodiment will be described using the flowchart of FIG. 20 and the timing chart of FIG.

  The camera CPU 120 starts imaging of the main image by the imaging element 110 by sending an imaging signal to the imaging element control circuit 121 in response to the SW2 being turned on (S220). The image sensor control circuit 121 controls the drive of the image sensor 110 by sending an image control signal Sens to the image sensor 110. Next, the camera CPU 120 sends a shutter release signal SH to the shutter control circuit 128 to open the release switch of the focal plane shutter 2 (S221). As a result, the front curtain and the rear curtain travel while forming a predetermined slit.

  Further, the camera CPU 120 confirms the setting state of the mode dial 119 for selecting the shooting mode via the signal input circuit 129. If the optical low-pass effect photographing mode is set by the operation of the mode dial 119 by the photographer (S224), the imaging operation is performed in the photographing mode in which the surface acoustic wave is generated in the optical low-pass filter 104 to obtain the optical low-pass effect. That is, the camera CPU 120 sends a signal to the surface acoustic wave generation circuit 127 to cause the optical low-pass filter 104 to generate a surface acoustic wave (S225).

  As shown in the timing chart of FIG. 21, the surface acoustic wave generation circuit 127 applies an AC voltage between the pair of comb electrodes (comb electrodes 43a and 43b in FIG. 4) provided in the optical low-pass filter 104 at the timing of SAW_X. At the same time, an AC voltage is applied between the other pair of comb-shaped electrodes (comb-shaped electrodes 42a and 42b in FIG. 4) at the timing of SAW_Y. In this embodiment, while performing the imaging operation of the main image, surface acoustic waves are generated at a predetermined period in a direction parallel to the pixel arrangement direction of the imaging element 110 (X direction in FIG. 4), and the imaging element 110 Surface acoustic waves are generated at a predetermined cycle in a direction perpendicular to the pixel arrangement direction (Y direction in FIG. 4).

  Here, since the SAW_X and SAW_Y drive signals output from the surface acoustic wave generation circuit 127 to the two comb-shaped electrodes have the same period and are output at different timings, the surface acoustic waves are generated. This occurs independently in the two axial directions of the optical low-pass filter 104.

  FIG. 22 shows the state of the photographing light beam when the surface acoustic wave is generated in the optical low-pass filter 104.

  In the figure, the optical low-pass filter 104 has a piezoelectric transparent thin film 141 such as ZnO deposited on a transparent substrate 140 such as quartz. Further, comb electrodes 142 a and 142 b are deposited on one end of the piezoelectric transparent thin film 141. As described above, the optical low-pass filter 104 includes the single transparent substrate 140 and the piezoelectric transparent thin film 141 deposited on the transparent substrate 140, so that the thickness of the optical low-pass filter 104 can be reduced. Regardless of the model, it can be placed in the imaging optical path. Note that the optical low-pass filter 104 may be formed of a piezoelectric transparent substrate.

  The front curtain 102a and the rear curtain 102b of the focal plane shutter 102 travel in the Y direction in FIG. 22 based on the release signal (SW2), and the subject light transmitted through the photographing lens 105 is the front curtain 102a. Then, the light passes through a slit formed by the rear curtain 102 b and enters the image sensor 110.

  In the timing chart of FIG. _1, EXP. _2, EXP. The dotted line indicated by _n indicates the exposure timing for the pixel line of the image sensor 110 of one line, two lines,... N lines (lines extending in the X direction and parallel in the Y direction in FIG. 22). It is. This exposure timing changes according to the movement of the slit.

  In FIG. 22, for example, a light beam emitted from the middle of a surface acoustic wave is refracted and passes through the slits of the front curtain 102a and the rear curtain 102b and enters the image sensor 110. Since this surface acoustic wave is a traveling wave, it travels during slit exposure and achieves image separation of the photographic light flux corresponding to the pixel pitch of the image sensor 110, as described in the first embodiment (FIGS. 9 and 10). To do.

  As a result, it is possible to prevent the occurrence of moiré and false colors that occur when a subject image including a spatial frequency component finer than a predetermined spatial frequency determined by the pixel arrangement period of the image sensor 110 is captured. A high image can be obtained.

  In the flowchart of the imaging operation in FIG. 20, the camera CPU 120 transmits an imaging end signal to the imaging element control circuit 121 in accordance with the end of the travel of the focal plane shutter 102, and the imaging operation by the imaging element 110 is ended (S226).

  On the other hand, when the photographer operates the mode dial 119 to set the high-resolution shooting mode (S224), the camera CPU 120 does not generate surface acoustic waves in the optical low-pass filter 104 and transfers to the image sensor 110. The exposure is performed. Unless surface acoustic waves are generated in the optical low-pass filter 104, the optical low-pass filter 104 acts as a general transparent substrate and image separation does not occur.

  In response to the end of the travel of the focal plane shutter 102, the camera CPU 120 transmits an imaging end signal to the image sensor control circuit 21 and ends the imaging operation by the image sensor 110 (S226).

  As described above, since the optical axis of the piezoelectric transparent substrate 141 constituting the optical low-pass filter 104 is in the plane, if the surface acoustic wave is not generated in the optical low-pass filter 104, a high level corresponding to the number of pixels of the image sensor 110 is obtained. A resolution image can be obtained.

  If the automatic selection mode is set by operating the mode dial 119 by the photographer (S222), the camera CPU 120 determines whether or not the image captured immediately before includes a periodic image. The camera CPU 120 obtains the spatial frequency characteristics of the captured image in order to determine whether the captured image includes a periodic image.

  If it is determined from the calculated spatial frequency characteristics of the image that a periodic image is not included (S223), the camera CPU 120 obtains a high-resolution image without generating surface acoustic waves in the optical low-pass filter 104. The image capturing operation is performed in the image capturing mode.

  On the other hand, if it is determined from the calculated spatial frequency characteristics of the image that a periodic image is included (S223), the camera CPU 120 generates a surface acoustic wave in the optical low-pass filter 104 (S225), and the optical low-pass effect is increased. An imaging operation is performed in the obtained imaging mode. The imaging operation for obtaining the optical low-pass effect by generating the surface acoustic wave in the optical low-pass filter 104 is as described above.

  In this way, by setting the automatic selection mode in the camera system, it is possible to leave the camera system to determine whether or not to generate the optical low-pass effect, thereby reducing the complexity of the photographer's operation of the camera system. be able to.

  When the image capturing operation of the main image is completed (S227), the image signal captured by the image sensor 110 is A / D converted by the image sensor control circuit 121 and then subjected to image processing by the image processing circuit 124. At this time, predetermined image processing is performed for color reproduction based on an output signal from the image sensor 110.

  The image signal on which the predetermined image processing has been performed is sent to the liquid crystal display element driving circuit 125 via the camera CPU 120, and the main image is displayed on the liquid crystal display element 109 (S207 in FIG. 19). Thus, the photographer can observe the captured subject image (main image) on the liquid crystal display element 9.

  At the same time, the camera CPU 120 stores the captured image signal as it is in the memory circuit 122 of the camera body 101 (S208). When the photographing operation is finished and the photographer turns off the main switch (S201), the camera system is turned off and enters a standby state (S210).

  In this embodiment, an example in which the optical low-pass filter 104 is disposed between the flip-up mirror 106 and the focal plane shutter 102 has been described. It may be arranged between the two.

  In the present embodiment, an example is shown in which surface acoustic waves are generated on the piezoelectric transparent substrate or the piezoelectric transparent thin film as the optical low-pass filter 104. As shown in the operation explanatory diagram of the optical low-pass filter in FIG. The piezoelectric body 141 is provided at the end of the surface of the transparent substrate 140 such as glass, and the piezoelectric body 141 is expanded and contracted in the surface direction of the transparent substrate 140 (the arrow direction in FIG. 23). It may be configured to generate and separate the imaging light flux.

  In the above-described embodiment, the light beam from the subject is transmitted through the optical low-pass filter and guided to the image sensor. However, in the optical system that reflects the light beam and guides it to the image sensor, the reflection surface has the above-described configuration. You may make it generate the surface acoustic wave etc. which were demonstrated in the Example.

1 is a schematic configuration diagram of a camera that is Embodiment 1. FIG. FIG. 2 is an electric circuit block diagram of the camera according to the first embodiment. The front view of an image sensor. The front view of an optical low-pass filter. 5 is an operation flowchart in the camera of Embodiment 1. 5 is a flowchart of an image capturing operation for a main image in the camera according to the first exemplary embodiment. Explanatory drawing of a mode dial. The timing chart at the time of imaging of this image. Operation | movement explanatory drawing (AD) of the optical low-pass filter in Example 1. FIG. FIG. 3 is an explanatory diagram of a separated image in the first embodiment. The intensity distribution of the separated image. 2 is an MTF characteristic of the optical low-pass filter in the first embodiment. 9 is a modification of the first embodiment, and is a timing chart at the time of capturing the main image. FIG. 6 is an explanatory diagram of a separated image in a modification of the first embodiment. FIG. 6 is a front view of an optical low-pass filter according to a modification of the first embodiment. Operation | movement explanatory drawing (A, B) of the optical low-pass filter in the modification of Example 1. FIG. FIG. 5 is a schematic configuration diagram of a camera system that is Embodiment 2. FIG. 6 is an electric circuit block diagram of a camera system that is Embodiment 2. 9 is an operation flowchart in the camera system according to the second embodiment. 9 is a flowchart of an image capturing operation for a main image in the camera system according to the second embodiment. 9 is a timing chart at the time of capturing a main image according to the second embodiment. FIG. 6 is an operation explanatory diagram of an optical low-pass filter in Embodiment 2. FIG. 10 is an operation explanatory diagram of an optical low-pass filter that is a modification of the second embodiment. The MTF characteristic of the optical low-pass filter in a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Camera 2 ... Shutter 3 ... Eyepiece 4 ... Optical low-pass filter 5 ... Shooting lens 9 ... Liquid crystal display element 10 ... Imaging element 20 ... CPU
DESCRIPTION OF SYMBOLS 21 ... Image sensor control circuit 22 ... Memory circuit 23 ... Interface circuit 24 ... Image processing circuit 25 ... Liquid crystal display element drive circuit 26 ... Lens drive circuit 27 ... Surface acoustic wave Generation circuit 28 ... Shutter control circuit 29 ... Signal input circuit 101 ... Camera body 104 ... Optical low pass filter 105 ... Lens device 110 ... Image sensor

Claims (6)

An optical element that changes an optical image by converting the optical image into an electrical signal and repeatedly changing the position of the light beam reaching the surface of the image sensor;
Control means for controlling the deformation of the optical element,
An optical apparatus, wherein a high frequency component of the optical image is reduced by repetitive deformation of the optical element. The optical apparatus according to claim 1, wherein the control unit periodically deforms the optical element in a specific direction. The optical apparatus according to claim 2, wherein the control unit generates a surface wave in the optical element. The optical apparatus according to claim 2, wherein the control unit generates a traveling wave in the optical element and causes the traveling wave to travel at least one wavelength during imaging with the imaging element. A mode that can be set to a first imaging mode in which the optical element is deformed to perform imaging with the imaging element, and a second imaging mode in which the optical element is subjected to imaging without deformation. The optical apparatus according to claim 1, further comprising a setting unit. The control means is configured to change the optical element based on the output of the imaging element and to perform imaging with the imaging element, and to perform imaging with the imaging element without deforming the optical element. The optical apparatus according to claim 1, wherein one of the second imaging modes for performing the imaging is set.

Images