JP2007121770A - Lens device, lens adjustment device, and camera - Google Patents

Abstract

An object of the present invention is to perform field curvature correction by enabling a correction lens to be moved in a compact and low-cost manner.
A correction lens for correcting curvature of field of a second lens provided in a second lens barrel is provided in the first lens barrel. The correction lens 18 includes three stud pins 14B provided in the housing 14A of the second lens barrel 14 and a through hole 18A of the correction lens 18, and the through hole 18A is sufficiently large with respect to the diameter of the stud pin 14B. So that the correction lens 18 can be moved in a direction perpendicular to the optical axis. Then, the first lens barrel 12 and the correction lens 20 are connected by the piezoelectric element sheet 20. That is, by applying a current to the piezoelectric element sheet 20, the piezoelectric element sheet 20 is distorted, and thereby the correction lens 18 is moved in the first lens barrel 12.
[Selection] Figure 1

Description

  The present invention relates to a lens device, a lens adjustment device, and a camera, and more particularly to a lens device, a lens adjustment device, and a camera that can correct field curvature of a photographing lens.

  Since a lens apparatus used for an interchangeable lens camera or the like has a field curvature characteristic, an image of a portion other than the optical axis is not necessarily a sharp image. That is, since the image surface has a characteristic of being curved in accordance with the distance from the optical axis, a sharp image is obtained near the optical axis, but an out-of-focus image is obtained at a position away from the optical axis.

  Therefore, in the technique described in Patent Document 1, it is proposed to receive field curvature information from the lens barrel, correct the focus position, and adjust the focus position of the subject image formed by the imaging lens. ing.

  In order to adjust the in-focus position, it is necessary to move a lens such as a correction lens. As a method for moving the lens, a technique described in Patent Document 2 has been proposed.

  In the technique described in Patent Document 2, the pin of the holding frame that holds the lens group that contributes to zooming and focusing among the lens groups that constitute the zoom lens device passes through the cam groove of the focus cam ring, and the zoom cam ring It has been proposed to engage the cam groove, attach a piezoelectric element type actuator to the focus cam ring, and apply a drive pulse to the piezoelectric element to move the focus cam ring to the optical axis method for focusing. Yes.

On the other hand, when a plurality of lenses are provided, the deviation of the optical axis of the lens causes curvature of field. Therefore, in the technique described in Patent Document 3, an apparatus for detecting a deviation of the optical axis of a lens has been proposed.
Japanese Patent Laid-Open No. 2003-121913 JP-A-8-94906 JP 2003-114166 A

  However, the technique described in Patent Document 3 only detects the optical axis deviation of the lens, and does not propose a correction method or a correction lens moving method for correcting the optical axis deviation of the lens.

  Similarly, the technique described in Patent Document 1 is proposed to acquire and correct field curvature information from the lens apparatus, but a method for moving the lens to correct field curvature is also proposed. It has not been.

  Furthermore, although the technique described in Patent Document 2 has proposed that the lens be moved in the optical axis direction by a piezoelectric element, there is a problem in that it is impossible to correct curvature of field that occurs due to optical axis misalignment. In addition, there is a problem that a complicated mechanism is required to move the lens in the optical axis direction.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to perform field curvature correction by enabling a correction lens to be moved in a small size and at a low cost.

  In order to achieve the above object, the lens device according to claim 1, wherein the correction lens for correcting curvature of field of a lens that forms a subject image, and the optical axis of the correction lens are movable, and the correction is performed. It comprises a lens barrel that houses a lens, and a piezoelectric element sheet that connects the lens barrel and the correction lens and moves the optical axis of the correction lens by distortion generated by applying a current.

  According to the first aspect of the present invention, the correction lens for correcting the curvature of field of the lens that forms the subject image is connected by the piezoelectric element sheet and housed in the lens barrel. The correction lens housed in the lens barrel is housed in such a way that the optical axis of the correction lens is movable, so that applying a current to the piezoelectric element sheet causes distortion in the piezoelectric element sheet, thereby changing the optical axis of the lens. Can move. For example, as in the third aspect of the invention, the piezoelectric element sheet moves the correction lens in a direction orthogonal to the optical axis of the correction lens, or uses the correction lens with the direction orthogonal to the optical axis of the correction lens as a rotation axis. You may make it rotate.

  That is, by moving the optical axis of the correction lens by the piezoelectric element sheet, the imaging position of the correction lens changes, so that the field curvature of the lens can be corrected.

  Accordingly, since the correction lens can be moved using a relatively inexpensive and small piezoelectric element sheet, the field curvature can be corrected by moving the correction lens with a small and low-cost configuration.

  For example, as in the second aspect of the invention, an image sensor that obtains a photographic signal by converting a subject image formed by a lens to a light source, and a piezoelectric element sheet based on the photographic signal obtained from the image sensor. By further comprising control means for controlling the applied current, it becomes possible to correct field curvature.

  At this time, if the control means has a plurality of piezoelectric element sheets as in the invention described in claim 4, the control means moves the correction lens by selectively applying a current to the plurality of piezoelectric element sheets. Can do. In other words, the control means may selectively control the piezoelectric element sheet to which current is applied and control the current value to be applied.

  The control means controls the current applied to the piezoelectric element sheet on the basis of a photographing signal obtained by photoelectrically converting a chart image determined in advance by the imaging element as in the invention described in claim 5. May be.

  The lens adjustment device according to claim 6 is a lens adjustment device that adjusts the position of the correction lens of the lens device according to claim 1, wherein the subject image formed by the lens is photoelectrically converted and photographed. Control means for controlling a current to be applied to the piezoelectric element sheet is provided based on the photographing signal obtained from the image sensor that obtains the signal.

  According to the lens adjustment device of the sixth aspect, the current to be applied to the piezoelectric element sheet is obtained based on the photographing signal obtained from the imaging element that photoelectrically converts the subject image formed by the lens to obtain the photographing signal. Since the control means for controlling is provided, the curvature of field can be corrected in the same manner as the lens apparatus according to claim 2. Further, since the lens apparatus according to the first aspect is adjusted, the curvature of field can be corrected by moving the correction lens with a small and low-cost configuration.

  For example, the piezoelectric element sheet moves the correction lens in a direction orthogonal to the optical axis of the correction lens, or rotates the direction orthogonal to the optical axis of the correction lens, as in the invention described in claim 7. The correction lens may be rotated as an axis.

  Further, as in the invention described in claim 8, when the control means has a plurality of piezoelectric element sheets, the control means can move the correction lens by selectively applying a current to the plurality of piezoelectric element sheets. it can. In other words, the control means may selectively control the piezoelectric element sheet to which current is applied and control the current value to be applied.

  The control means controls the current applied to the piezoelectric element sheet on the basis of a photographing signal obtained by photoelectrically converting a chart image determined in advance by the imaging element, as in the ninth aspect of the invention. May be.

  The lens device according to any one of claims 1 to 5 may be provided in a camera as in the invention according to claim 10.

  Further, in the case of a camera provided with the lens device according to any one of claims 2 to 5, as in the invention according to claim 11, the focus at the center of the photographed image represented by the photographing signal is obtained. A storage unit that pre-calculates and stores the optimum position of the in-focus state of the correction lens based on the state and the in-focus state of the four corners of the captured image, and the control unit stores the optimum position stored in the storage unit. The current applied to the piezoelectric element sheet may be controlled so as to move the correction lens. That is, since the correction lens is moved to the optimum position stored in the storage means, processing such as calculation of the optimum position of the correction lens can be shortened, and the field curvature can be corrected at high speed.

  Further, when the lens of the lens device according to any one of claims 2 to 5 includes a variable magnification lens capable of changing a photographing magnification, a photographing signal is provided as in the invention according to the twelfth aspect. Storage means for calculating and storing in advance the optimum position of the focus state of the correction lens for each shooting magnification based on the focus state at the center of the captured image represented by The control unit may control the current applied to the piezoelectric element sheet so as to move the lens to the optimum position of the correction lens stored in the storage unit corresponding to the magnification of the variable magnification lens. That is, since the optimum position of the correction lens is stored for each lens magnification, processing such as calculation of the optimum position of the correction lens for each magnification can be shortened, and the field curvature can be corrected at high speed. .

  As described above, according to the present invention, since the optical axis of the correction lens is moved using the piezoelectric element sheet, the correction lens can be moved with a small size and at low cost, and the field curvature can be corrected. effective.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an exploded perspective view showing a configuration of a lens apparatus according to an embodiment of the present invention.

  The lens apparatus according to the embodiment of the present invention is used as a camera unit built in or attached to a camera.

  A lens apparatus 10 according to an embodiment of the present invention includes a first lens barrel 12 and a second lens barrel 14 as shown in FIG.

  The first lens barrel 12 is provided with a protective glass 16, and the field curvature of the second lens 24 provided in the second lens barrel 14 on the rear side of the protective glass 16 (inside the first lens barrel 12). A correction lens 18 is provided for correcting the above. The correction lens 18 has a through hole 18A through which three stud pins 14B provided in the housing 14A of the second barrel 14 pass, and the through hole 18A and the stud pin 14B are engaged with each other. ing. The through hole 18A has a sufficient size with respect to the diameter of the stud pin 14B, and the correction lens 18 is movable in a direction perpendicular to the optical axis of the correction lens 18. In addition, it is good also as a rotation possible for the direction orthogonal to the optical axis of the correction lens 18 as a rotation axis.

  A piezoelectric element sheet 20 is provided between the first lens barrel 12 and the correction lens 18, and the first lens barrel 12 and the correction lens 20 are connected by the piezoelectric element sheet 20. By applying an electric current to the piezoelectric element sheet 20, the piezoelectric element sheet 20 is distorted. As a result, the correction lens 18 moves in the first lens barrel 12, and the optical axis of the correction lens 18 is changed. Moving. In the present embodiment, the correction lens 18 is moved in a direction orthogonal to the optical axis. In addition, the piezoelectric element sheet | seat 20 is connected to the flexible cable 22, and can be connected to the system controller 36 shown in FIG. In the present embodiment, the correction lens 18 is supported by the three piezoelectric element sheets 20, but the present invention is not limited to this. For example, the correction lens 18 is supported by four or more piezoelectric element sheets 20. You may do it.

  In the second lens barrel 14, the second lens 24 and the image sensor 26 described above are provided. The protective glass 16 and the correction lens 18 of the first lens barrel 12 and the second lens 24 of the second lens barrel 14 are provided. A subject image is formed on the image sensor 26 via the.

  Next, the lens adjustment device 30 that adjusts the lens device 10 of the present invention configured as described above will be described.

  FIG. 2 is a block diagram showing the configuration of the lens adjustment device 30 according to the embodiment of the present invention.

  As shown in FIG. 2, the lens adjustment device 30 according to the embodiment of the present invention includes a driver 32, a signal processing unit 34, a system controller 36, a display device 38, and an operation unit 40.

  The driver 32 drives the image sensor 26 provided in the lens device 10 described above, and acquires a shooting signal. An imaging signal acquired by the imaging element 26 is processed by the signal processing unit 34 and input to the system controller 36.

  The signal processing unit 34 includes, for example, a CDS circuit, an analog / digital converter (hereinafter referred to as “A / D”), and the like, and correlates a shooting signal indicating a subject image read from the image sensor 26. Performs double sampling (CDS) processing and color separation processing of R, G, B color signals to adjust the signal level of each color signal, and converts the analog signal processed by the CDS circuit to a digital signal Then, processing such as white balance adjustment (not shown), gamma correction, and YC signal creation is performed on the data converted into digital data by A / D. The signal processing unit 34 compresses the digital image data in a predetermined compression format (for example, JPEG), and compresses / decompresses the decompressed digital image data. May be further performed.

  The system controller 36 shoots the image with the image sensor 26, analyzes the photographic signal processed by the signal processor 34, applies a current to the piezoelectric element sheet 20 based on the analysis result, moves the correction lens 18, and The curvature aberration of the two lenses 24 is corrected. For example, the system controller 36 divides the shooting signal into a plurality of areas, calculates the focus state for each of the divided areas, and calculates the focus state at the center of the image represented by the shooting signal, the focus states at the four corners, and the like. The movement direction and the movement amount of the correction lens 18 are determined based on the calculation result, and the piezoelectric element sheet 20 is moved so that the correction lens 18 moves according to the determined movement direction and movement amount of the correction lens 18. Apply current. As a result, distortion occurs in the piezoelectric element sheet 20, and the correction lens 18 moves in a direction orthogonal to the optical axis, so that the bending aberration of the second lens 24 can be corrected. The system controller 36 controls the movement of the correction lens 18 by selecting the piezoelectric element sheet 20 to which the current is applied or controlling the value of the applied current.

  The display device 38 displays the analysis result of the focus state by the system controller 36, and the operation unit 40 inputs an instruction regarding adjustment of the lens device 10. In the present embodiment, the display device 38 and the operation unit 40 are provided, but may be omitted.

  Further, as shown in FIG. 2, the lens adjustment device 30 is configured to house the above-described lens device 10, and the imaging device 26 of the lens device 10 includes contact electrodes and connectors in the driver 32 and the signal processing unit 34. The flexible cable 22 to which the piezoelectric element sheet 20 of the lens device 10 is connected is electrically connected to the system controller 36 by contact electrodes, connectors, or the like.

  In the present embodiment, an example in which the lens device 10 is housed in the lens adjustment device 30 and the lens device 10 is adjusted by the lens adjustment device 30 will be described. However, as shown in FIG. You may make it comprise the camera unit 42 provided with the structure (The driver 32, the signal processing part 34, the system controller 36, the display apparatus 38, and the operation part 40) of the apparatus 30. FIG.

  Next, processing when the lens apparatus 10 according to the embodiment of the present invention is adjusted with the lens apparatus 10 will be described.

  FIG. 4 is a flowchart showing an example of a flow of processing when the lens apparatus 10 according to the embodiment of the present invention is adjusted.

  First, as shown in FIG. 2, when the lens device 10 is set in the lens adjustment device 30 and the start of measurement is instructed by the operation unit 40 or the like, in step 100, the image is taken by the imaging device 26 of a predetermined chart. Move on to step 102.

  In step 102, an imaging signal that is captured by the image sensor 26 and processed by the signal processing unit 34 is input to the system controller 36, and the imaging signal is analyzed by the system controller 36. The system controller 36 analyzes the focus state of the image from the photographing signal. The analysis of the focus state is performed, for example, by analyzing the frequency of the image or analyzing the contrast.

  Next, in step 104, the system controller 36 determines whether or not the blur amounts at the four corners are substantially the same from the analysis result of step 102. In this determination, for example, the imaging signal is divided into a plurality of regions and frequency analysis is performed to determine whether or not the frequencies of the regions corresponding to the four corners are substantially the same. If the determination is negative, step 106 is performed. If the result is affirmative, the process proceeds to step 110. Note that the amount of blur is determined by measuring the maximum contrast value or the like using a TTL (Through The Lens) method used in autofocus or the like to determine whether or not the blur amounts at the four corners are substantially the same. You may do it.

  In step 106, the system controller 36 calculates the moving direction and moving amount of the correction lens 18 based on the analysis result in step 102, and the process proceeds to step 108. For example, the system controller 36 converges at a higher frequency than the focused area in the out-of-focus area other than the center of the captured image, so the frequencies of the images in the four corner areas are substantially the same. The moving direction and moving amount of the correction lens 18 are calculated.

  In step 108, the system controller 36 performs current control on the piezoelectric element sheet 20 based on the calculation result in step 106, and the process returns to step 102 to repeat the above-described processing. That is, the piezoelectric element sheet 20 to which the current is applied is determined so as to be the movement direction of the correction lens 18 calculated in step 106, and the current is applied to the piezoelectric element sheet 20 so that the calculated movement amount is obtained. As a result, distortion occurs in the piezoelectric element sheet 20, and the correction lens 18 is moved in a direction orthogonal to the optical axis.

  On the other hand, when the correction lens 18 is moved and the blur amounts at the four corners of the image represented by the photographing signal become substantially the same, and the determination in step 104 is affirmed and the routine proceeds to step 110, the process of storing the position of the correction lens 18 is performed. To complete a series of processing. Note that the correction lens position storage processing in step 110 includes, for example, the piezoelectric element sheet 20 to which current is to be applied and the current applied to the piezoelectric element sheet 20 at which the correction lens 18 position where the blurs at the four corners are substantially the same. A value or the like (a control value for energizing the piezoelectric element sheet 20) is stored in the lens device 10 or stored in a camera or the like on which the lens device 10 is mounted.

  As described above, in the present embodiment, the correction lens 18 can be moved using the piezoelectric element sheet 20, and thus the moving mechanism of the correction lens 18 can be reduced in size. In addition, since the piezoelectric element sheet 20 is relatively inexpensive, a moving mechanism for the correction lens 18 can be configured at a low cost. Accordingly, it is possible to correct the curvature of field by making the lens movable at a small size and at low cost.

  Next, a digital camera including the functions of the lens device 10 and the lens adjustment device 30 according to the above-described embodiment of the present invention will be described.

  FIG. 5 is a block diagram showing the configuration of the digital camera according to the embodiment of the present invention.

  As shown in FIG. 5, the digital camera 50 includes a zoom lens 54 and a focus (AF) lens 56 for forming a subject image, and a lens unit 52 configured to include the correction lens 18 of the lens device 10 described above. An image sensor 26 that is disposed behind the optical axis of the lens unit 52 and captures a subject image, a CDS circuit 60, an analog / digital converter (hereinafter referred to as "A / D") 62, a data processing unit 64, and a lens. A drive controller 66, a correction lens drive controller 68, and a microcomputer 70 that controls the overall operation of the digital camera 50 are provided.

  The CDS 60 performs correlated double sampling (CDS) processing on a photographing signal indicating a subject image read from the CCD 58, and color-separates the signals into R, G, and B color signals to determine the signal level of each color signal. The A / D 62 converts the analog signal processed by the CDS circuit 60 into a digital signal, and the data processing unit 64 performs white balance (not shown) on the data converted into the digital data by the A / D 62. Performs adjustment, gamma correction, YC signal creation, etc., performs compression processing on digital image data in a predetermined compression format (for example, JPEG), and performs decompression processing on the compressed digital image data Performs compression / decompression. The CCD 58 is driven in synchronization with a timing signal generated from a timing generator (not shown).

  In addition, the lens drive control unit 66 includes a zoom motor for moving the zoom lens 54 included in the lens unit 52 (extension and contraction of the lens barrel), an AF (Auto Focus) motor for moving the focus (AF) lens 56, In addition, each motor such as an iris shutter motor that drives an aperture / shutter mechanism (not shown) is driven. The lens drive control unit 66 performs focus control (automatic focus adjustment) by driving the AF lens 56 so that the contrast of an image obtained by imaging by the CCD 58 is maximized according to an instruction from the microcomputer 70. . As the automatic focus adjustment, a so-called TTL photometry method is adopted in which the position of the AF lens 56 is set so that the contrast of the read image is maximized. The automatic focus adjustment is started when the shutter button is half-pressed. For example, the focus is adjusted with respect to the subject at the photographing position indicated by a predetermined autofocus frame.

  The correction lens drive control unit 68 controls the movement of the correction lens 18 by performing energization control of the piezoelectric element sheet 20 provided between the first lens barrel 12 and the correction lens 18 of the lens device 10 described above. That is, the curvature of field can be corrected by moving the correction lens 18.

  Further, the microcomputer 70 controls the movement of the image display unit 72 that displays a subject image obtained by imaging by the CCD 58 and various information, the operation unit 74 including a power switch, an operation button, a shutter button, and the correction lens 18. System controller 36, ROM 76 for storing programs for performing various controls of the digital camera 50, RAM 78 for developing various programs and temporarily storing data, and various adjustment data (for example, auto Interface (I / F) 84 for connecting an EEPROM 80 storing data for focusing, data for shading correction of the CCD 32, etc., and a memory card 82 for storing shooting signals obtained by shooting as image data Has been.

  The image display unit 72 also functions as a finder that displays a moving image (through image) obtained by continuous imaging by the CCD 58 in addition to displaying an image obtained by photographing and displaying various information.

  The digital camera 50 according to the embodiment of the present invention has a measurement mode for correcting the curvature of field of the lens unit 52, and the movement position of the correction lens 18 is determined by starting the measurement mode. It is supposed to be. In addition, it transfers to measurement mode by operating the operation part 74, for example.

  Next, processing in the measurement mode performed by the digital camera 50 configured as described above will be described.

  FIG. 6 is a flowchart showing an example of the flow of processing performed in the measurement mode of the digital camera 50 according to the embodiment of the present invention.

  When the operation unit 74 of the digital camera 50 is operated to shift to the measurement mode, in Step 200, the zoom lens 54 is moved to the wide angle end, and the process proceeds to Step 202. That is, when the microcomputer 70 instructs the lens drive control unit 66 to move the zoom lens 54, the lens drive control unit 66 moves the zoom lens 54 to the wide angle end.

  In step 202, AF processing is started and the routine proceeds to step 204. For example, the AF process is started by pointing the digital camera 50 toward an appropriate subject and half-pressing a shutter button or the like, and is read while the lens drive control unit 66 drives the AF lens 56. The position of the AF lens 56 is set so that the contrast of the image is maximized.

  Next, in step 204, the microcomputer 70 measures the blur amounts at the four corners of the photographed image. Specifically, the focus state is analyzed using the frequency of the photographic signal, the captured image represented by the photographic signal is divided into a plurality of regions, and the frequency of the image corresponding to each divided region is measured to measure the four corners. Measure the amount of blur. Note that the blur amount may be measured by measuring the maximum contrast value or the like using a TTL method used for autofocus or the like.

  In subsequent step 206, the microcomputer 70 determines whether or not the blur amounts at the four corners are substantially the same from the blur amount measurement result in step 204. In this determination, for example, the imaging signal is divided into a plurality of regions and frequency analysis is performed to determine whether or not the frequencies of the regions corresponding to the four corners are substantially the same. If the determination is negative, step 208 is performed. If YES, the process proceeds to step 212.

  In step 208, the microcomputer 70 analyzes the focus state, calculates the movement direction and movement amount of the correction lens 18, and proceeds to step 210. For example, the microcomputer 70 converges at a higher frequency than the focused area in an unfocused area other than the center of the captured image, and therefore the frequencies of the images in the four corner areas are substantially the same. The moving direction and moving amount of the correction lens 18 are calculated.

  In step 210, the microcomputer 70 controls the current to the piezoelectric element sheet 20 based on the calculation result in step 208, and returns to step 204 to repeat the above-described processing. That is, the piezoelectric element sheet 20 to which the current is applied is determined so as to be the movement direction of the correction lens 18 calculated in step 206, and the current is applied to the piezoelectric element sheet 20 so that the calculated movement amount is obtained. As a result, distortion occurs in the piezoelectric element sheet 20, and the correction lens 18 is moved in a direction orthogonal to the optical axis.

  On the other hand, when the correction lens 18 is moved and the blur amounts at the four corners of the image represented by the photographic signal become substantially the same, the determination at step 206 is affirmative and the routine proceeds to step 212. 20) is recorded as correction lens information in the RAM 78 or the like, and the process proceeds to step 2147.

  In step 214, the microcomputer 70 determines whether or not the zoom lens 54 is at the telephoto end. In this determination, the position information of the zoom lens 54 is acquired from the lens drive control unit 66, and it is determined from the position information whether or not the camera is at the telephoto end. If the determination is negative, the process proceeds to step 216. The microcomputer 70 outputs an instruction to move the zoom lens 54 to the one-step telephoto end side to the lens drive control unit 66, thereby moving the zoom lens 54 to the one-step telephoto end side and returns to step 204 to perform the above-described processing. Repeatedly, when the determination in step 214 is affirmed, the processing in a series of measurement modes is terminated.

  As described above, in the present embodiment, the correction lens 18 can be moved using the piezoelectric element sheet 20 in the same manner as the lens device 10 and the lens adjustment device 30 described above. The digital camera 50 can be downsized. In addition, since the piezoelectric element sheet 20 is relatively inexpensive, a moving mechanism for the correction lens 18 can be configured at a low cost. Accordingly, it is possible to correct the curvature of field by making the lens movable at a small size and at low cost.

  In the present embodiment, the position of the correction lens 18 is obtained for each magnification of the zoom lens 54 and recorded in the RAM 78 or the like, so that processing such as calculation of the position of the correction lens 18 for each magnification is shortened. Therefore, it is possible to easily and quickly correct the curvature aberration for each lens magnification.

  Next, a modified example of the process in the measurement mode of the digital camera 50 described above will be described. In the modification, an example will be described in which the above-described digital camera 50 is provided with a photographing lens having a fixed photographing magnification instead of the zoom lens 54.

  FIG. 7 is a flowchart showing a modified example of processing in the measurement mode of the digital camera 50 according to the embodiment of the present invention.

  When the operation unit 74 of the digital camera 50 is operated to shift to the measurement mode, in step 300, the correction lens 18 is set to a predetermined origin position. That is, the microcomputer 70 outputs an instruction for setting the correction lens 18 to the origin position to the correction lens drive control unit 68 to set the correction lens 18 to a predetermined origin position.

  In step 302, the focus lens 56 is set at a predetermined position. That is, the microcomputer 70 outputs an instruction to set the focus lens 56 at a predetermined position to the lens drive control unit 66, thereby setting the focus lens 56 at a predetermined position. For example, the predetermined position is set on the side with the longest focal distance or the side with the closest focal length.

  Next, in step 304, the chart board is photographed. That is, when the shutter button or the like is pressed halfway, the chart plate is photographed by the image sensor 26 and the process proceeds to step 306.

  In step 306, the captured image is divided into a plurality of areas, and the microcomputer 70 evaluates the focus state of each area. The focus state of each region may be evaluated by measuring the frequency of the image corresponding to each divided region, or by evaluating the focus state using the TTL method.

  Subsequently, in step 308, it is determined whether or not the evaluation of each lens position has been completed. In the determination, the microcomputer 70 determines whether or not the focus lens 56 is moved to all the movement ranges and the focus state is evaluated. If the determination is negative, the process proceeds to step 310. When the microcomputer 70 outputs an instruction to move the focus lens 56 by one step to the lens drive control unit 66, the microcomputer 70 moves the focus lens 56 by one step, returns to step 306, repeats the above processing, and determines at step 308. When is affirmed, the routine proceeds to step 312.

  In step 312, the microcomputer 70 identifies the position of the focus lens 56 in which each area is in focus, and the process proceeds to step 314.

  In step 314, the microcomputer 70 calculates the difference between the position of the focus lens 56 in focus in each area and the position of the focus lens 56 in focus in the center of the captured image, and the process proceeds to step 316.

  In step 316, the microcomputer 70 primarily records each difference calculated in step 314 as a shift amount of the focus position with respect to the optical axis direction in the RAM 78 or the like, and proceeds to step 318.

  In step 318, the position of the correction lens 18 is determined from the amount of deviation temporarily stored in the RAM 78 or the like by the microcomputer 70, and the series of processes is terminated. For example, the average value of the calculated differences may be obtained, and the position of the correction lens 18 may be determined based on the average value so that the shift amount of the focus position in each region becomes equal.

  Even in this case, since the correction lens 18 can be moved using the piezoelectric element sheet 20 as in the above-described embodiment, the movement mechanism of the correction lens 18 can be reduced in size. In addition, since the piezoelectric element sheet 20 is relatively inexpensive, a moving mechanism for the correction lens 18 can be configured at a low cost. Accordingly, it is possible to correct the curvature of field by making the lens movable at a small size and at low cost.

It is a disassembled perspective view which shows the structure of the lens apparatus concerning embodiment of this invention. It is a block diagram which shows the structure of the lens adjustment apparatus concerning embodiment of this invention. It is a block diagram which shows the case where the structure of a lens adjustment apparatus is provided in a lens apparatus. It is a flowchart which shows an example of the flow of a process at the time of performing adjustment of the lens adjustment apparatus lens apparatus concerning embodiment of this invention. It is a block diagram which shows the structure of the digital camera concerning embodiment of this invention. It is a flowchart which shows an example of the flow of the process performed at the time of the measurement mode of the digital camera concerning embodiment of this invention. It is a flowchart which shows the modification of the process at the time of the measurement mode of the digital camera concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lens apparatus 12 1st lens tube 14 2nd lens tube 18 Correction lens 20 Piezoelectric element sheet | seat 26 Imaging element 30 Lens adjustment apparatus 32 Driver 34 Signal processing part 36 System controller 42 Camera unit 50 Digital camera 52 Lens unit 54 Zoom lens 78 RAM

Claims (12)

A correction lens for correcting curvature of field of a lens that forms a subject image;
A barrel that houses the correction lens so that the optical axis of the correction lens can be moved;
A piezoelectric element sheet that connects the lens barrel and the correction lens and moves the optical axis of the correction lens by distortion generated by applying an electric current;
A lens apparatus comprising:   An image sensor that photoelectrically converts the subject image formed by the lens to obtain a photographic signal; and a control unit that controls a current applied to the piezoelectric element sheet based on the photographic signal. The lens device according to claim 1, characterized in that:   The piezoelectric element sheet moves the correction lens in a direction orthogonal to the optical axis of the correction lens, or rotates the correction lens about a direction orthogonal to the optical axis of the correction lens as a rotation axis. Item 3. The lens device according to Item 1 or Item 2.   The lens device according to claim 2, wherein the lens device includes a plurality of the piezoelectric element sheets, and the control unit selectively applies a current to the plurality of piezoelectric element sheets.   5. The control unit according to claim 2, wherein the control unit controls a current applied to the piezoelectric element sheet based on a photographing signal obtained by photoelectrically converting a predetermined chart image by the imaging element. The lens device according to any one of the above. A lens adjustment device for adjusting a position of the correction lens of the lens device according to claim 1,
Control means for controlling a current applied to the piezoelectric element sheet based on the imaging signal obtained from an imaging device that photoelectrically converts an object image formed by the lens to acquire an imaging signal. Lens adjustment device to do.   The piezoelectric element sheet moves the correction lens in a direction orthogonal to the optical axis of the correction lens, or rotates the correction lens about a direction orthogonal to the optical axis of the correction lens as a rotation axis. Item 7. The lens adjustment device according to Item 6.   The lens adjustment device according to claim 6 or 7, wherein the lens device includes a plurality of the piezoelectric element sheets, and the control unit selectively applies a current to the plurality of piezoelectric element sheets. .   The control means controls a current applied to the piezoelectric element sheet based on a photographing signal obtained by photoelectrically converting a predetermined chart image by the imaging element. The lens adjustment device according to any one of the above.   A camera comprising the lens device according to any one of claims 1 to 5. The lens device according to any one of claims 2 to 5,
Storage means for preliminarily calculating and storing the optimum position of the in-focus state of the correction lens based on the in-focus state at the center of the captured image represented by the captured signal and the in-focus states at the four corners of the captured image;
With
The camera, wherein the control means controls a current applied to the piezoelectric element sheet so as to move the correction lens to the optimum position stored in the storage means. A camera comprising the lens device according to any one of claims 2 to 5,
The lens includes a magnification variable lens capable of changing a photographing magnification, and is based on a focus state at a center of a photographed image represented by the photographing signal and focus states at four corners of the photographed image. Storage means for calculating and storing in advance the optimum position of the in-focus state of the correction lens;
The control means controls a current applied to the piezoelectric element sheet so as to move the correction lens to the optimum position stored in the storage means corresponding to the magnification of the variable magnification lens. Camera.

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