JP2009187092A - Imaging device, imaging method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To use an optical system for imaging, having a proper response characteristic according to a correction characteristic. <P>SOLUTION: This imaging device has: the optical system having nearly the same optical transfer function to light from an object point regardless of a distance to the object point by expanding the light from the object point to nearly the same size regardless of the distance to the object point; and a correction part correcting an image obtained through the optical system based on the optical transfer function of the optical system. Dependence upon a defocus amount of the optical transfer function is smaller in a spatial frequency area having a larger correction amount by which the image is corrected by the correction part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, an imaging method, and a program. The present invention particularly relates to an imaging apparatus and an imaging method for imaging an image, and a program for the imaging apparatus.

A camera including an objective optics having a PSF larger than twice the pitch of the light receiving element array is known (see, for example, Patent Document 1). In addition, a technique is known in which an optical transfer function of optical imaging is substantially unchanged with respect to a focus-related aberration by an optical element that changes the phase of the wavefront (see, for example, Patent Document 2).
JP 2006-519527 A JP-T-2006-523330

  The difference in OTF tends to be large for light from an object with a significantly different distance from the imaging device. Therefore, as described in the prior art document 1 and the prior art document 2, if the restoration process is performed using the same filter, the subject image cannot be restored well in the frequency region where the MTF characteristic depends on the distance to the object. There is a fear.

  In order to solve the above-described problem, according to a first embodiment of the present invention, an imaging apparatus is provided that expands light from an object point to substantially the same size regardless of the distance to the object point. The optical transfer function for light from the optical system is substantially the same regardless of the distance to the object point, and a correction unit that corrects an image captured through the optical system based on the optical transfer function of the optical system. The dependency of the transfer function on the defocus amount is smaller in the spatial frequency region where the correction amount by which the image is corrected by the correction unit is larger.

  According to the second aspect of the present invention, there is provided an imaging method in which an optical transfer function for light from an object point is obtained by expanding the light from the object point to substantially the same size regardless of the distance to the object point. A correction stage for correcting an image captured through a substantially identical optical system regardless of the distance to the object point based on the optical transfer function of the optical system, and the dependency of the optical transfer function on the defocus amount is a correction stage. The correction amount by which the image is corrected is smaller in the larger spatial frequency region.

  According to a third aspect of the present invention, there is provided a program for an imaging apparatus, wherein the imaging apparatus expands light from an object point to substantially the same size regardless of the distance to the object point. Defocusing of the optical transfer function by causing the optical transfer function for the light to function as a correction unit that corrects the image captured through the same optical system regardless of the distance to the object point based on the optical transfer function of the optical system. The dependence on the amount is smaller in the spatial frequency region where the correction amount by which the image is corrected by the correction unit is larger.

  According to the fourth aspect of the present invention, in the imaging device, the optical transfer function for the light from the object point is obtained by expanding the light from the object point to substantially the same size regardless of the distance to the object point. An optical system that is substantially the same regardless of the distance to the object point, and a correction unit that corrects an image captured through the optical system based on the optical transfer function, the correction unit corresponding to the defocus amount of the optical transfer function The spatial frequency component of the image in the spatial frequency region having a higher dependency is corrected with a smaller correction amount.

  According to the fifth aspect of the present invention, in the imaging method, the optical transfer function for the light from the object point is obtained by expanding the light from the object point to substantially the same size regardless of the distance to the object point. A correction stage for correcting an image captured through a substantially identical optical system regardless of the distance to the object point based on the optical transfer function is provided, and the correction stage is more dependent on the defocus amount of the optical transfer function. The spatial frequency component of the image in the spatial frequency domain is corrected with a smaller correction amount.

  According to a sixth aspect of the present invention, there is provided a program for an imaging apparatus, wherein the imaging apparatus expands light from an object point to substantially the same size regardless of the distance to the object point. An optical transfer function with respect to the light of the optical system is substantially the same regardless of the distance to the object point, and a correction unit that corrects an image captured through the optical system based on the optical transfer function. It functions as a correction unit that corrects a spatial frequency component of an image in a spatial frequency region having a greater dependency on the focus amount with a smaller correction amount.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 shows an example of a block configuration of an imaging apparatus 100 according to an embodiment. The imaging device 100 captures a subject and generates an image. The imaging apparatus 100 includes a lens system 110 as an example of an optical system that focuses light, a light receiving unit 120 that receives light that has passed through the lens system 110, a correction parameter storage unit 180, a correction parameter selection unit 185, a correction unit 140, An image processing unit 145 and an output unit 150 are provided.

  The lens system 110 expands the light from the object point to substantially the same size regardless of the distance to the object point, so that the optical transfer function for the light from the object point is substantially the same regardless of the distance to the object point. Has optical properties. The optical characteristics of the lens system 110 will be described qualitatively with reference to FIG.

  The light receiving unit 120 has a plurality of light receiving elements arranged two-dimensionally. The correction unit 140 corrects an image obtained by A / D converting the amount of light received by each of the plurality of light receiving elements. For example, the correction unit 140 corrects the image based on the value of the received light amount after A / D conversion, the position of each light receiving element, and the optical transfer function of the lens system 110. As described above, the correction unit 140 corrects the image captured through the lens system 110 based on the optical transfer function of the lens system 110.

  The correction parameter storage unit 180 stores a plurality of correction parameters having different correction amounts for correcting an image. Then, the correction parameter selection unit 185 is a correction parameter that can correct the spatial frequency component of the image in the spatial frequency region where the dependence of the optical transfer function of the lens system 110 on the defocus amount is larger with a smaller correction amount, Select from multiple correction parameters. Then, the correction unit 140 corrects the image with the correction parameter selected by the correction parameter selection unit 185.

  As described above, the correction unit 140 corrects the frequency component in the spatial frequency region, which has a large dependence on the defocus amount of the optical transfer function of the lens system 110, with a small correction amount. Therefore, according to the imaging apparatus 100, it is possible to suppress the occurrence of artifacts in the corrected image due to the difference in the optical transfer function. The correction parameter selection unit 185 selects a correction parameter that can correct the spatial frequency component of the image in the spatial frequency region where the dependency of the optical transfer function on the image height is larger with a smaller correction amount. You may choose from.

  The image processing unit 145 performs image processing on the image corrected by the correction unit 140. Examples of image processing performed by the image processing unit 145 include color balance processing, γ conversion, color synchronization processing, contour correction processing, and color correction processing. As described above, the image processing unit 145 converts the pixel value of the image corrected by the correction unit 140 into a non-linear value with respect to the amount of light received by the light receiving element.

  Then, the output unit 150 outputs an output image obtained by processing by the image correction unit 140 and the image processing unit 145. For example, the output unit 150 may display an output image. The output unit 150 may record the output image on a recording medium. In addition, the output unit 150 may send an output to the communication line. The output unit 150 may output the output image after compressing it.

  FIG. 2 schematically shows an example of the optical characteristics of the lens system 110. In this figure, among the light rays incident on the lens system 110 from an object point on the optical axis, the trajectories of three light rays 210, 220, and 230 that are incident on the entrance pupil 205 at different positions from the optical axis 200 are schematically illustrated. Is shown in As shown in the figure, the light ray 210, the light ray 220, and the light ray 230 are incident on the entrance pupil 205 at a position close to the optical axis 200 in this order.

  As shown in the drawing, the light beam 210 intersects the optical axis 200 at a position 215 away from the lens system 110 in the optical axis direction from the paraxial focal position 250 by the lens system 110. Further, the light beam 230 intersects the optical axis 200 at the position 235 away from the lens system 110 in the optical axis direction from the position 215 by the lens system 110. Then, the light ray 220 incident on the position farthest from the optical axis 200 crosses the optical axis 200 at the position 225 between the position 215 and the position 235 by the lens system 110.

  As shown in the figure, it is expected that the size of the light spread by the lens system 110 is substantially the same between the position 215 and the position 235. Thus, the lens system 110 has overcorrected spherical aberration and images light substantially far from the paraxial focal point position 250. Therefore, according to the lens system 110, the spherical aberration is excessively corrected for the distance in the optical axis direction where the magnitude of the light spread from the object point is substantially the same regardless of the position of the image plane in the optical axis direction. It can be longer than if not.

  Thus, when the distance in the optical axis direction becomes longer, the image plane position at which the magnitude of the light spread is substantially the same for light from an object point existing in a wider distance range from the lens system 110. Can exist. When the light receiving unit 120 is provided at such an image plane position, the optical transfer functions at the position where the light receiving unit 120 is provided are substantially the same regardless of the distance to the object point. As described above, in the lens system 110, the optical transfer function with respect to light from the object point is substantially the same regardless of the distance to the object point due to the above-described aberration characteristics.

  The optical characteristics of the lens system 110 have been described qualitatively with reference to FIG. Note that the schematic diagram of the lens system 110 shown in FIG. 2 is drawn for the purpose of qualitatively understanding the optical characteristics of the lens system 110, and is not drawn according to an actual scale. Should.

  FIG. 3 shows an example of the configuration of the lens system 110. The lens system 110 includes a diaphragm 300, a lens 310, a lens 320, and a lens 330. The image plane is denoted by reference numeral 380. In the drawing, a plurality of light rays are drawn on the lens system 110. Hereinafter, the arrangement of the lens 310, the lens 320, and the lens 330 and their optical characteristics will be described.

  The refractive indexes of the lens 310 and the lens 330 are 1.53128710, 1.52470166, and 1.52196091 for light with a wavelength of 486.133 nm, a wavelength of 587.562 nm, and a wavelength of 656.273 nm, respectively. The refractive index of the lens 320 is 1.59943869, 1.58546992 and 1.579886377 for light with a wavelength of 486.133 nm, a wavelength of 587.562 nm, and a wavelength of 656.273 nm, respectively. The diaphragm 300 is provided at a distance of 0.0005358337 mm from the apex of the lens 310 on the image plane side.

  The thickness of the lens 310 is 1.688465 mm. In addition, the thickness in description of this figure shows the length of the optical axis direction of a lens. The radius of curvature of the object-side surface of the lens 310 is 11.47443 mm, the cross-sectional radius of the object-side is 1.482371 mm, and the conical constant of the object-side surface is −556.3053. The curvature radius of the image side surface of the lens 310 is -14.56409 mm, the cross-sectional radius of the image side is 2.111479 mm, and the conic constant of the object side surface is 41.9261. In the description of this figure, if the radius of curvature is negative, it indicates that the surface shape is concave with respect to light.

  The lens 320 is provided at a distance of 0.0992469 mm from the lens 310 in the image plane direction. In the description of this figure, the distance between lenses indicates the distance between the image side surface of the object side lens and the object side surface of the image side lens on the optical axis. The thickness of the lens 320 is 0.2598875 mm. The radius of curvature of the object-side surface of the lens 320 is 1.401978 mm, the cross-sectional radius of the object-side surface is 2.175006 mm, and the cone constant of the object-side surface is −7.665905. Further, the radius of curvature of the image side surface of the lens 320 is 0.6412006 mm, the sectional radius of the image side is 2.041809 mm, and the conic constant of the image side surface is −2.333718.

  The lens 330 is provided at a distance of 3.139189 mm from the lens 320 in the image plane direction. The thickness of the lens 330 is 0.138909 mm. Further, the radius of curvature of the object-side surface of the lens 330 is −0.374831 mm, the cross-sectional radius of the object-side surface is 3.653998 mm, and the conic constant of the object-side surface is −260.7873. Further, the curvature of the image side surface of the lens 330 is −0.3040315 mm, the cross-sectional radius of the image side is 3.744696 mm, and the conic constant of the image side surface is −254.3315. The image plane is set at a position away from the lens 330 by a distance of 1.885325 mm.

  Thus, the plurality of lenses 310, the lens 320, and the lens 330 are arranged coaxially with the central axes of the lenses aligned. Accordingly, the lens system 110 is rotationally symmetric with respect to the optical axis. Due to the rotational symmetry, the alignment of the lenses at the time of manufacturing the imaging device 100 becomes very easy.

  The absolute value of the difference between the normal angle of the image plane and the angle at which the chief ray is incident on the image plane is determined in advance so that the calculation error of the optical transfer function of the lens system 110 is smaller than a predetermined value. Less than the given value. As described above, by increasing the telecentricity of the lens system 110, the calculation error of the optical transfer function can be reduced. For example, when calculating the MTF, the MTF can be calculated with a sufficiently small error even by FFT. For this reason, it is possible to restore the image blur caused by the lens system 110 at high speed.

  FIG. 4 shows the aberration characteristics of the lens system 110 shown in FIG. In this figure, a spherical aberration diagram, astigmatism and distortion diagram, and lateral aberration diagram are shown in order from the top. As shown in the uppermost spherical aberration diagram, the spherical aberration of the lens system 110 shown in FIG. 3 is overcorrected. It should be noted that the horizontal axis of this spherical aberration diagram indicates the position with respect to the set image plane, and does not indicate the position with respect to the paraxial focal point.

  As shown in the figure, the longitudinal aberration has a positive value over the entire image surface. Longitudinal aberration increases monotonously up to the position of P1 in the figure, and starts to decrease monotonically at P1.

  In addition, a graph showing transverse aberration at a plurality of image heights is shown at the bottom of the figure. The upper left graph shows a lateral aberration diagram on the optical axis, and the upper right graph shows a lateral aberration diagram at an image height of 1.1250 mm. The lower left graph shows the lateral aberration at an image height of 1.5750 mm, and the lower right graph shows the lateral aberration at an image height of 2.2500 mm. As described above, the lateral aberration of the lens system 110 shows substantially the same shape at each image height. If wavefront aberration is used as an index, the difference between the optical path length along the light incident on the incident position on the entrance pupil different from the principal ray and the optical path length along the principal ray, and the entrance to the entrance pupil of the lens system 110 The relationship between the incident positions may be substantially the same regardless of the image height.

  FIG. 5 shows the optical transfer characteristics of the lens system 110 shown in FIG. In this figure, the spot diagram showing the image height and defocus dependency of the spot diagram in order from the top, the defocus dependency of the MTF, and the spatial frequency characteristics of the MTF are shown.

  In the uppermost spot diagram, spot diagrams at different image heights and different defocus amounts are shown. In this spot diagram diagram, a plurality of spot diagrams with a plurality of different defocus amounts at the same image height are arranged in the horizontal direction. A plurality of spot diagrams at different image heights with the same defocus amount are arranged in the vertical direction.

  As shown by the numerical image height to the left of each spot diagram, this spot diagram diagram shows 1.1250 mm from the optical axis, 1.5750 mm from the optical axis, and 2.2500 mm from the optical axis on the optical axis. A spot diagram at the image height at the position of is included. Further, as the defocus amount indicated by a numerical value below each spot diagram, this spot diagram diagram shows a position of −75 μm from the image plane, a position of −37.5 μm from the image plane, and a position of the image plane. , A spot diagram at a position 37.5 μm from the image plane and at a position 75 μm from the image plane is included.

  As shown in this spot diagram diagram, it is understood that the spread of the spot diagram is substantially the same over at least the image plane position in the optical axis direction within a predetermined range, and is substantially the same regardless of the image height. Thus, the spread of light from the object point by the lens system 110 is substantially the same over the image plane position in the optical axis direction within a predetermined range. The light spread may be a spot diagram spread as shown in the figure, or may be a light spread indicated by a point spread function.

  As described above, the spread of light from the object point by the lens system 110 is substantially the same regardless of the image height, and the spread of light from the object point by the lens system 110 is at least in a predetermined range of the optical axis direction. It can be seen that they are substantially the same over the image plane positions. In addition, as each spot diagram shows, it turns out that the intensity distribution of the light from the object point in an image surface has a spatial "core" centering on the position of a chief ray. That is, the intensity distribution on the image plane of light from the object point by the lens system 110 has two peaks at different image heights, and one peak exists at a position where the principal ray crosses the image plane. As can be seen from having such a “core”, the lens system 110 can also transmit high frequencies substantially spatially. The high-frequency transfer characteristics are also shown in a graph of the spatial frequency characteristics of the MTF described later.

  Further, as shown in the graph of the defocus dependence of MTF shown in the middle of the figure, it can be seen that the distribution of MTF values is substantially the same for a plurality of image heights, sagittal rays and meridional rays. Further, the MTF shows substantially the same value at least within the defocus range shown in the graph. Thus, the MTF of the lens system 110 takes substantially the same value over a wide defocus range.

  Further, as shown in the graph of the spatial frequency characteristics of the MTF at the bottom of the figure, it can be seen that the lens system 110 has substantially the same MTF frequency characteristics for a plurality of image heights, sagittal rays and meridional rays. Thus, it can be said that the MTF of the lens system 110 is substantially the same regardless of the image height. The MTF of the lens system 110 is substantially the same over the image plane position in the optical axis direction within a predetermined range.

  In this figure, a line indicating the diffraction limit where the MTF value monotonously decreases from 1 is shown. However, the MTF of the lens system 110 is substantially equal to the diffraction limit cutoff frequency. It can be seen that Thus, it can be seen that the lens system 110 can transmit high frequency spatially.

  FIG. 6 shows the dependence of the optical transfer function of the lens system 110 on the image height. As shown by the spatial frequency characteristics of the MTF in the lowermost stage in FIG. 5, the MTF characteristics of the light from the object point where the principal ray enters the position of the image height 0 (corresponding to the line 610 in FIG. 6) and the principal ray. Is different from the MTF characteristic of light from an object point incident at an image height of 1.1250 mm (corresponding to the line 620 in FIG. 6) in some frequency regions. In FIG. 6, the difference in dependency of the MTF characteristic on the image height is schematically shown by lines 610 and 620. Thus, the MTF of the lens system 110 has image height dependent frequency regions f1 to f2, which are frequency regions depending on the image height.

  A line 600 indicates the diffraction limited MTF characteristic. When the correction unit 140 corrects the optical response indicated by the optical transfer function of the lens system 110, it is desirable that the MTF characteristics of the entire system including the correction unit 140 ideally match the MTF characteristics indicated by the line 600. . However, when the image height dependent frequency region is largely corrected by the inverse filter used by the correction unit 140, a difference in MTF characteristics in the image height dependent frequency region may appear significantly in the corrected image. .

  FIG. 7 illustrates an example of correction parameters stored in the correction parameter storage unit 180 in a table format. The correction parameter storage unit 180 stores a plurality of inverse filters that correct the optical response of the lens system 110.

  Note that the spread of light in the light receiving unit 120 is obtained by the optical transfer function of the lens system 110. A pixel block to be used for correction is determined from the spread of the light and the distance (pixel pitch) between the plurality of light receiving elements of the light receiving unit 120. For example, it is determined whether the correction unit 140 uses a 5 × 5 pixel block or a 7 × 7 pixel block. When the pixel block to be used is determined, a frequency region that can be restored by the inverse filter is determined based on the pixel pitch. Here, when the frequency region that can be restored by the correction unit 140 overlaps with the image height-dependent frequency region shown in FIG. 6, the difference in MTF depending on the image height is corrected as described above. It may appear in the image after correction by the unit 140.

  Therefore, it is desirable that the lens system 110 has optical characteristics in which the dependency of the optical transfer function on the image height is smaller in the spatial frequency region where the correction amount by which the image is corrected by the correction unit 140 is larger. For example, the dependency of the optical transfer function of the lens system 110 on the image height is desirably smaller than a predetermined value in a correctable frequency region that is a spatial frequency region that can be corrected by the correcting unit 140. Note that the dependency of the optical transfer function of the lens system 110 in the correctable frequency region on the image height may be smaller than the dependency on the image height in the spatial frequency region other than the correctable frequency region. Conversely, the dependency of the optical transfer function of the lens system 110 on the image height in the spatial frequency region other than the correctable frequency region may be greater than the dependency on the image height in the correctable frequency region.

  6 and 7, the dependency of the MTF characteristic on the image height is shown, but the same can be said for the defocus amount. That is, the MTF characteristic can also depend on the defocus amount. For this reason, when the frequency region restored by the correction unit 140 overlaps the frequency region that depends on the defocus amount, the difference in the MTF depending on the defocus amount appears in the image by the correction by the correction unit 140. May end up.

Therefore, it is desirable that the lens system 110 has optical characteristics in which the dependency of the optical transfer function on the defocus amount is smaller in the spatial frequency region where the correction amount by which the image is corrected by the correction unit 140 is larger. For example, the dependency of the optical transfer function of the lens system 110 on the defocus amount is desirably smaller than a predetermined value at least in a correctable frequency region that is a spatial frequency region that can be corrected by the correction unit 140.
The dependency on the defocus amount in the correctable frequency region, which is the spatial frequency region in which the correction unit 140 can correct the image, is smaller than the dependency on the defocus amount in the spatial frequency region other than the correctable frequency region. Good. In other words, the dependency of the optical transfer function of the lens system 110 in the spatial frequency region other than the correctable frequency region on the defocus amount may be larger than the dependency on the defocus amount in the correctable frequency region.

  Thus, the MTF characteristic of the lens system 110 has been described. On the other hand, the correction process can be controlled so that no artifact occurs in the corrected image. For example, the correction unit 140 may correct the spatial frequency component of the image in the spatial frequency region where the dependence of the optical transfer function on the defocus amount is larger with a smaller correction amount. Further, regarding the image height, the correction unit 140 may correct the spatial frequency component of the image in the spatial frequency region where the dependence of the optical transfer function on the image height is larger with a smaller correction amount.

  Specifically, the correction parameter storage unit 180 may store a plurality of correction parameters having different correctable frequency regions that are spatial frequency regions in which an image can be corrected. Then, the correction parameter selection unit 185 selects a correction parameter in which the spatial frequency region and the correctable frequency region whose dependency on the defocus amount of the optical transfer function is larger than a predetermined value do not coincide with each other from the plurality of correction parameters. You may choose.

  Further, in relation to the image height, the correction parameter selection unit 185 selects a plurality of correction parameters in which the spatial frequency region in which the dependence of the optical transfer function on the image height is greater than a predetermined value does not match the correctable frequency region. You may select from among the correction parameters. Regarding the image height dependency, the correction unit 140 is different for each image height so as to reduce the dependency of the optical transfer function on the image height in the spatial frequency region where the dependency on the image height of the optical transfer function is larger. The image may be corrected with the correction amount. Specifically, the correction parameter selection unit 185 may select different correction parameters for each image height.

  FIG. 8 shows an exemplary hardware configuration of the imaging apparatus 100. The imaging apparatus 100 includes a CPU peripheral part, an input / output part, and a legacy input / output part. The CPU peripheral section includes a CPU 1505, a RAM 1520, a graphic controller 1575, and a display device 1580 that are connected to each other by a host controller 1582. The input / output unit includes a communication interface 1530, a hard disk drive 1540, and a CD-ROM drive 1560 that are connected to the host controller 1582 by the input / output controller 1584. The legacy input / output unit includes a ROM 1510, a flexible disk drive 1550, and an input / output chip 1570 connected to the input / output controller 1584.

  The host controller 1582 connects the RAM 1520, the CPU 1505 that accesses the RAM 1520 at a high transfer rate, and the graphic controller 1575. The CPU 1505 operates based on programs stored in the ROM 1510 and the RAM 1520 to control each unit. The graphic controller 1575 acquires image data generated by the CPU 1505 or the like on a frame buffer provided in the RAM 1520 and displays the image data on the display device 1580. Alternatively, the graphic controller 1575 may include a frame buffer that stores image data generated by the CPU 1505 or the like.

  The input / output controller 1584 connects the host controller 1582 to the hard disk drive 1540, the communication interface 1530, and the CD-ROM drive 1560, which are relatively high-speed input / output devices. The hard disk drive 1540 stores programs and data used by the CPU 1505. The communication interface 1530 is connected to the network communication device 1598 to transmit / receive programs or data. The CD-ROM drive 1560 reads a program or data from the CD-ROM 1595 and provides it to the hard disk drive 1540 and the communication interface 1530 via the RAM 1520.

  The input / output controller 1584 is connected to the ROM 1510, the flexible disk drive 1550, and the relatively low-speed input / output device of the input / output chip 1570. The ROM 1510 stores a boot program that is executed when the imaging apparatus 100 is activated, a program that depends on the hardware of the imaging apparatus 100, and the like. The flexible disk drive 1550 reads a program or data from the flexible disk 1590 and provides it to the hard disk drive 1540 and the communication interface 1530 via the RAM 1520. The input / output chip 1570 connects various input / output devices via the flexible disk drive 1550 or a parallel port, serial port, keyboard port, mouse port, and the like.

  A program executed by the CPU 1505 is stored in a recording medium such as the flexible disk 1590, the CD-ROM 1595, or an IC card and provided by the user. The program stored in the recording medium may be compressed or uncompressed. The program is installed in the hard disk drive 1540 from the recording medium, read into the RAM 1520, and executed by the CPU 1505. The program executed by the CPU 1505 causes the imaging apparatus 100 to be used as the correction parameter storage unit 180, the correction parameter selection unit 185, the correction unit 140, the image processing unit 145, and the output unit 150 described with reference to FIGS. Make it work.

  The program shown above may be stored in an external storage medium. As the storage medium, in addition to the flexible disk 1590 and the CD-ROM 1595, an optical recording medium such as a DVD or PD, a magneto-optical recording medium such as an MD, a tape medium, a semiconductor memory such as an IC card, or the like can be used. Further, a storage device such as a hard disk or a RAM provided in a server system connected to a dedicated communication network or the Internet may be used as a recording medium and provided to the imaging apparatus 100 as a program via the network. As described above, the computer controlled by the program functions as the imaging apparatus 100.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

It is a figure which shows an example of the block configuration of the imaging device 100 concerning one Embodiment. It is a figure which shows typically an example of the optical characteristic of the lens system. 2 is a diagram illustrating an example of a configuration of a lens system 110. FIG. It is a figure which shows the aberration characteristic of the lens system 110 shown in FIG. It is a figure which shows the optical transmission characteristic of the lens system 110 shown in FIG. It is a figure which shows the dependence with respect to image height of the optical transfer function of the lens system. It is a figure which shows an example of the correction parameter which the correction parameter storage part 180 has stored in the table format. 2 is a diagram illustrating an example of a hardware configuration of the imaging apparatus 100. FIG.

Explanation of symbols

100 imaging device 110 lens system 120 light receiving unit 140 correction unit 145 image processing unit 150 output unit 180 correction parameter storage unit 185 correction parameter selection unit 200 optical axis 205 entrance pupil 210 light beam 220 light beam 230 light beam 300 aperture 310 lens 320 lens 330 lens 1505 CPU
1510 ROM
1520 RAM
1530 Communication interface 1540 Hard disk drive 1550 Flexible disk drive 1560 CD-ROM drive 1570 Input / output chip 1575 Graphic controller 1580 Display device 1582 Host controller 1584 Input / output controller 1590 Flexible disk 1595 CD-ROM
1598 Network communication device

Claims (15)

By expanding the light from the object point to approximately the same size regardless of the distance to the object point, the optical transfer function for the light from the object point is approximately the same regardless of the distance to the object point, and
A correction unit that corrects an image captured through the optical system based on an optical transfer function of the optical system;
The dependence of the optical transfer function on the defocus amount is smaller in the spatial frequency region where the correction amount by which the image is corrected by the correction unit is larger. The dependency on the defocus amount in the correctable frequency region, which is the spatial frequency region in which the correction unit can correct the image, is more dependent on the defocus amount in the spatial frequency region than the correctable frequency region. The imaging device according to claim 1, which is small. The imaging apparatus according to claim 2, wherein the dependency of the optical transfer function on the image height is smaller in a spatial frequency region where a correction amount by which the image is corrected by the correction unit is larger. The imaging apparatus according to claim 3, wherein dependency on the image height in the correctable frequency region is smaller than dependency on the image height in a spatial frequency region other than the correctable frequency region. By spreading the light from the object point to approximately the same size regardless of the distance to the object point, the optical transfer function for the light from the object point is imaged through a substantially identical optical system regardless of the distance to the object point. A correction step for correcting the image based on the optical transfer function of the optical system,
The dependence of the optical transfer function on the defocus amount is a smaller imaging method in a spatial frequency region where the correction amount by which the image is corrected in the correction stage is larger. A program for an imaging apparatus, wherein the imaging apparatus is
By spreading the light from the object point to approximately the same size regardless of the distance to the object point, the optical transfer function for the light from the object point is imaged through a substantially identical optical system regardless of the distance to the object point. Function as a correction unit for correcting the image based on the optical transfer function of the optical system,
A program in which the dependence of the optical transfer function on the defocus amount is smaller in a spatial frequency region where the correction amount by which the image is corrected by the correction unit is larger. By expanding the light from the object point to approximately the same size regardless of the distance to the object point, the optical transfer function for the light from the object point is approximately the same regardless of the distance to the object point, and
A correction unit that corrects an image captured through the optical system based on the optical transfer function, and
The correction unit is an imaging apparatus that corrects the spatial frequency component of the image in a spatial frequency region in which the dependence of the optical transfer function on the defocus amount is larger with a smaller correction amount. The imaging device according to claim 7, wherein the correction unit corrects a spatial frequency component of the image in a spatial frequency region where the dependence of the optical transfer function on the image height is larger with a smaller correction amount. The correction unit corrects the image with a different correction amount for each image height so as to reduce the dependency of the optical transfer function on the image height in a spatial frequency region where the dependency on the image height of the optical transfer function is larger. The imaging device according to claim 8. A correction parameter storage for storing a plurality of correction parameters having different correction amounts for correcting the image;
A correction for selecting a correction parameter capable of correcting the spatial frequency component of the image in a spatial frequency region having a greater dependency on the defocus amount of the optical transfer function with a smaller correction amount from the plurality of correction parameters. A parameter selector and
The imaging apparatus according to claim 7, wherein the correction unit corrects the image with a correction parameter selected by the correction parameter selection unit. The correction parameter storage unit stores a plurality of correction parameters having different correctable frequency regions that are spatial frequency regions capable of correcting the image,
The correction parameter selection unit selects a correction parameter in which the spatial frequency region in which the dependence of the optical transfer function on the defocus amount is greater than a predetermined value does not match the correctable frequency region, among the plurality of correction parameters. The imaging device according to claim 10, wherein the imaging device is selected from the following. A correction parameter storage for storing a plurality of correction parameters having different correction amounts for correcting the image;
A correction parameter for selecting a correction parameter capable of correcting the spatial frequency component of the image in a spatial frequency region where the dependence of the optical transfer function on the image height is larger with a smaller correction amount from the plurality of correction parameters. A selection unit and
The imaging apparatus according to claim 8, wherein the correction unit corrects the image with a correction parameter selected by the correction parameter selection unit. The correction parameter storage unit stores a plurality of correction parameters having different correctable frequency regions that are spatial frequency regions capable of correcting the image,
The correction parameter selection unit selects a correction parameter in which the spatial frequency region whose dependence on the image height of the optical transfer function is greater than a predetermined value does not match the correctable frequency region from the plurality of correction parameters. The imaging device according to claim 10 to select. By spreading the light from the object point to approximately the same size regardless of the distance to the object point, the optical transfer function for the light from the object point is imaged through a substantially identical optical system regardless of the distance to the object point. A correction step of correcting the obtained image based on the optical transfer function,
In the correction step, the spatial frequency component of the image in the spatial frequency region where the dependence of the optical transfer function on the defocus amount is larger is corrected with a smaller correction amount. Imaging with an optical system in which the optical transfer function for light from an object point is approximately the same regardless of the distance to the object point by expanding the light from the object point to approximately the same size regardless of the distance to the object point A program for a device, wherein the imaging device is
A correction unit that corrects an image captured through the optical system based on the optical transfer function, wherein a spatial frequency component of the image in a spatial frequency region in which the dependency of the optical transfer function on the defocus amount is larger. A program that functions as a correction unit that corrects with a smaller correction amount.

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