JP2020204786A - Phase filter, imaging optical system, and imaging system - Google Patents

Abstract

To suppress the generation of in-plane positional deviation of an image point according to defocus in a focal depth enlarged image after image processing of wavefront coding (WFC).SOLUTION: An imaging optical system comprises: a phase filter including a plurality of rows of ring bands having a concave surface serving as a concave lens having a substantially parabolic cross-sectional shape concentrically circular about an optical axis; and an image formation lens as convex lens with one focal point. A light flux parallel to an optical axis entering each ring band of the phase filter passes through the focal position of the image formation lens, and each concave surface disperses the incident light flux locally. Each light flux is overlapped with one another in a range enlarged before and after the optical axis including the focal position of the image formation lens.SELECTED DRAWING: Figure 1

Description

The present invention relates to a phase filter, an imaging optical system, and an imaging system. Specifically, in a depth-of-focus enlarged image after image processing of WFC, in-plane position shift of an image point according to the focus shift occurs. Regarding the technology that makes it possible to suppress.

In the pupil plane of the imaging camera optical system, by giving a phase distribution given by a cubic function to the coordinates in the pupil plane, the blur of the point image with respect to the defocus is made uniform, and the uniform blur is called deconvolution. A technique called Wavefront Coding (hereinafter abbreviated as WFC), which is removed by processing to expand the depth of field and the depth of focus of the optical system, has been proposed.

As a conventional technique related to such WFC, for example, the pupil function is phase-modulated by a phase filter that realizes a third-order phase function in the optical system of an imaging camera, and image processing is performed on the captured image to focus the optical system. A technique for increasing the depth (see Patent Document 1) has been proposed. In addition, as a phase filter that modulates the optical transfer function (OTF), when the x and y coordinates are orthogonal to the optical axis, the cubic function is generalized by the series of functions represented by the product of their arbitrary powers. A technique (see Patent Document 2) for expanding the focal depth of an optical system by giving a phase distribution in the shape of an orthogonal shape and performing image processing on the captured image has also been proposed. On the other hand, although it is not an imaging optical system, a technique (see Patent Document 3) has been proposed in which a non-diffraction beam is generated by using a conical prism called an axicon to improve the efficiency of laser wavelength conversion.

Japanese Patent No. 3275010 Japanese Unexamined Patent Publication No. 2011-120309 Japanese Unexamined Patent Publication No. 8-271942

In the above-mentioned conventional technique, the phase distribution of the phase filter is given by a cubic function or a function similar thereto with respect to the x-axis and the y-axis of the coordinates in the pupil plane. As described above, when a phase filter that is not rotationally symmetric with respect to the optical axis is used to make the point image uniform with respect to the defocus, there is a problem that the position of the point image shifts depending on the amount of the defocus.

For example, in the cubic function, the coefficient α is used for the phase distribution for the normalized pupil plane coordinates x and y.
Represented by. When the defocused wave surface aberration is added here, the normalized pupil radius coordinates ρ are used.

Here, W ₂₀ is the aberration coefficient of defocus, that is, defocus. The first term means that the cubic function phase distribution is added in the pupil plane with a deviation of W ₂₀ / 3α in both the x and y directions. This basically corresponds to a phase shift on the focal plane and does not affect the point image intensity distribution. Since the second term x, a phase distribution of the primary function of y, corresponds to a so-called wavefront tilt, in proportion to W _{20 2} ^/ 3.alpha. Means that the shift is the image point position on the focal plane. Since the third term is a constant term, it does not affect the point image intensity distribution. Therefore, if there is a cubic function phase distribution, the wave surface aberration of the focus shift is converted into the lateral shift of the point image distribution. Therefore, if only this lateral shift is allowed, the point image distribution does not substantially change even if there is a focus shift, and the blurring becomes uniform regardless of the focus shift. This enables deconvolution. This is the principle of WFC. However, since the point image shifts due to the focus shift, it becomes a problem in applications such as measuring the position of an object based on the position of the point image.

Further, an optical surface that generates a phase distribution that is not rotationally symmetric with respect to the optical axis, such as a cubic function distribution, basically requires a similar aspherical optical surface. Plastic injection molding and glass mold press molding are widely used for aspherical surfaces because of the mold processed by rotary lathe processing with a cutting tool. However, axisymmetric shapes are indispensable for lathe machining, and non-axisymmetric shapes such as cubic function aspherical surfaces require two-dimensional numerical control machining with a rotary grinding tool, which increases machining costs and machining time. There's a problem.

Further, in a phase filter described by a continuous function such as a cubic function distribution, a concave-convex shape having at least several tens of wavelengths or more is required, and when a light beam having an angle of view is incident, the phase shift amount is a desired shift. There is a problem that it deviates from the amount.

Further, in an optical system using an axicon, the laser beam propagates without being diffracted while being focused on a thin beam within a range in which the parallel beams incident on the bottom surface of the axicon are refracted and overlapped. However, this lens is used for parallel beams, and cannot be used for an optical system that requires simultaneous acquisition of many imaging points, such as an imaging camera.

Therefore, an object of the present invention is to provide a technique capable of suppressing the occurrence of in-plane position shift of the image point according to the focus shift in the depth of focus enlarged image after the image processing of WFC.

The phase filter of the present invention that solves the above problems has a ring zone structure that is rotationally symmetric with respect to the optical axis, and each ring zone uniformly expands the incident luminous flux on the focal plane and overlaps each other. It is characterized by having a cross-sectional shape. According to this, it is possible to suppress the occurrence of in-plane position shift of the image point according to the focus shift in the depth of focus enlarged image after the image processing of WFC.

Further, the imaging optical system of the present invention has a ring band structure that is rotationally symmetric with respect to the optical axis, and each ring band uniformly expands the incident luminous flux on the focal plane and overlaps each other. It is characterized in that the phase filter having the above is mounted on the imaging optical system. According to this, it is possible to suppress the occurrence of in-plane position shift of the image point according to the focus shift in the depth of focus enlarged image after the image processing of WFC, and the image pickup optical system can be set to the object position depending on the position of the point image. It can be used for measurement purposes.

Further, the imaging system of the present invention has an annular structure that is rotationally symmetric with respect to the optical axis, and each annular has a substantially parabolic cross-sectional shape in which the incident light beam is uniformly enlarged on the focal plane and overlaps with each other. The feature is that the included phase filter is subjected to deconvolution image processing on the image captured by the imaging optical system mounted on the imaging optical system to obtain a depth of focus enlarged image. According to this, it is possible to suppress the occurrence of in-plane position shift of the image point according to the focus shift in the depth of focus enlarged image after the image processing of WFC, and the image pickup system can measure the object position according to the position of the point image. It becomes possible to use it for the purpose of performing.

Further, the vehicle traveling support device of the present invention has a ring band structure that is rotationally symmetric with respect to the optical axis, and each ring band uniformly expands the incident light beam on the focal plane and overlaps each other. Depth of focus image processing is performed on the image of the object around the vehicle captured by the imaging optical system equipped with the phase filter having a shape in the imaging optical system to acquire the depth of focus enlarged image. It is characterized in that a predetermined image recognition algorithm is applied to simultaneously detect a plurality of objects within a certain distance from a vehicle and existing at different distances from each other. According to this, it is possible to simultaneously detect an obstacle located near the vehicle and an obstacle located far away from the vehicle, which has the effect of improving the safety of the vehicle running.

Further, the monitoring device of the present invention has a ring zone structure that is rotationally symmetric with respect to the optical axis, and each ring zone uniformly expands the incident light beam on the focal plane and overlaps with each other. Depth of focus image processing is performed on the image of the monitored area captured by the image pickup optical system equipped with the possessed phase filter in the imaging optical system to acquire a depth of focus enlarged image, which is predetermined to the depth of focus enlarged image. The image recognition algorithm of the above is applied to simultaneously detect a plurality of medical treatment target areas existing at different distances from the imaging optical system in the monitoring target area. According to this, the recognition rate of a suspicious person, a criminal, or the like who has invaded or is located in the monitored area is improved regardless of the location distance from the imaging optical system.

Further, the authentication device of the present invention has a ring band structure that is rotationally symmetric with respect to the optical axis, and each ring band uniformly expands the incident light beam on the focal plane and overlaps each other. Depth of focus magnified images are acquired by performing deconvolution image processing on each image in the same authentication target area, which was imaged multiple times by the imaging optical system equipped with the possessed phase filter in the imaging optical system, and the depth of focus is obtained. A predetermined image recognition algorithm is applied to the enlarged image to authenticate the same authentication target region from each image having a different shooting distance from the imaging optical system. According to this, even if the distance of the authentication target (human fingerprint, vein, iris, etc.) to the imaging optical system changes every time the authentication is performed, the variation in the distance is appropriately absorbed, and the authentication accuracy is increased. Can be improved.

Further, the medical device of the present invention has an annular structure that is rotationally symmetric with respect to the optical axis, and each annular has a substantially free-form cross-sectional shape that uniformly expands the incident light beam on the focal plane and overlaps each other. Depth of focus image processing is performed on the image of the medical treatment target area in the human body taken by the imaging optical system equipped with the phase filter provided in the imaging optical system to acquire the depth of focus enlarged image. It is characterized in that a predetermined image recognition algorithm is applied to the image, and images of a plurality of parts existing at different distances from the imaging optical system in a medical treatment target area are simultaneously output. According to this, the simultaneous visibility of the affected area in the medical staff is enhanced regardless of the perspective of the affected area from the imaging optical system. This facilitates the design of optical systems in medical cameras and the like, makes it possible to reduce the number of lenses required, and leads to a reduction in manufacturing costs.

In any of the above-mentioned vehicle traveling support device, monitoring device, authentication device, and medical device, the adjustment accuracy between the lens and the sensor surface is relaxed, and the manufacturing cost can be reduced.

According to the present invention, it is possible to suppress the occurrence of in-plane position shift of the image point according to the focus shift in the depth of focus enlarged image after the image processing of WFC.

It is a schematic diagram of the image pickup optical system equipped with the phase filter of 1st Embodiment. It is a top view which shows the structure of the phase filter in 1st Embodiment. It is a side sectional view which shows the structure of the phase filter in 1st Embodiment. It is a figure which shows the refracted ray by an axicon prism. It is a figure which shows the configuration example of the image pickup optical system which used the phase filter of 1st Embodiment, and the image pickup system which performs image processing on the image imaged by the image pickup optical system. It is a schematic diagram for formulating the shape of a parabolic cross section. It is a schematic diagram of the imaging optical system accompanying the explanation of the deconvolution operation. It is a figure which shows the processing result comparison example of the captured image with and without the phase filter of 1st Example. It is a figure which shows the wave surface aberration of the pupil surface by the phase filter of 1st Example. It is a figure which shows the calculation result 1 of the point image distribution by the phase filter of 1st Example. It is a figure which shows the calculation result 2 of the point image distribution by the phase filter of 1st Example. It is a figure which shows the calculation result 3 of the point image distribution by the phase filter of 1st Example. It is a figure which shows the calculation result 4 of the point image distribution by the phase filter of 1st Example. It is a figure which shows the calculation result 5 of the point image distribution by the phase filter of 1st Example. It is a top view which shows the structure of the phase filter of 2nd Example. It is a side sectional view which shows the structure of the phase filter of 2nd Example. This is an example of the optical path difference distribution by the phase filter of the second embodiment. It is a deconvolution result image by the 2nd Example. It is a top view which shows the structure of the phase filter of 3rd Example. It is a side sectional view which shows the structure of the phase filter of 3rd Example. This is an example of the optical path difference distribution by the phase filter of the third embodiment. It is a deconvolution result image according to the 3rd Example. It is a figure which shows the configuration example of the vehicle running support device in 2nd Embodiment. It is a figure which shows the hardware configuration example of the information processing apparatus provided in the vehicle running support apparatus of 2nd Embodiment. It is a figure which shows the example of the processing flow executed by the vehicle running support device in 2nd Embodiment. It is a figure which shows the configuration example of the monitoring apparatus in 3rd Embodiment. It is a figure which shows the hardware configuration example of the information processing apparatus included in the monitoring apparatus in 3rd Embodiment. It is a figure which shows the example of the processing flow executed by the monitoring apparatus in 3rd Embodiment. It is a figure which shows the configuration example of the authentication apparatus in 4th Embodiment. It is a figure which shows the hardware configuration example of the information processing apparatus included in the authentication apparatus in 4th Embodiment. It is a figure which shows the example of the processing flow executed by the authentication apparatus in 4th Embodiment. It is a figure which shows the structural example of the medical apparatus in 5th Embodiment. It is a figure which shows the hardware configuration example of the information processing apparatus provided in the medical apparatus of 5th Embodiment. It is a figure which shows the example of the processing flow executed by the medical apparatus in 5th Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view of a phase filter 101 in the first embodiment and an imaging optical system 150 equipped with the phase filter 101, FIG. 2 is a plan view showing the structure of the phase filter 101 in the first embodiment, and FIG. 3 is a side cross section. It is a figure. The phase filter 101 and the imaging lens 102 included in the imaging optical system 150 shown in FIG. 1 both show the shape of the side cross section.

As shown in FIGS. 1 to 3, the phase filter 101 has a disk-shaped outer shape and a rotationally symmetric shape centered on the optical axis 1. Further, in the phase filter 101, a plurality of grooves, that is, concave surfaces 112 having a parabolic cross-sectional shape are formed concentrically around the optical axis 1 at substantially equal intervals. The concave surface 112 formed concentrically around the optical axis 1 in this way is referred to as a ring band 111, and the ring bands 111 and the like are collectively referred to as a ring band structure 110. The example of the phase filter 101 shown in FIGS. 1 to 3 has a ring band structure 110 composed of two rows of ring bands 111. The annular zone 111 is a concave surface that acts as a concave lens in the radial direction of the pupil surface with respect to the light rays incident on the annular zone 111. The width of the ring band 111 in the phase filter 101 shown here is the same between the ring bands.

In the imaging optical system 150, the imaging lens 102 is arranged so as to share the optical axis 1 with the phase filter 101 described above. The imaging lens 102 is a lens capable of forming an image of an object space at a predetermined position on the optical axis 1 without the phase filter 101. By forming the imaging optical system 150 in such a configuration that the phase filter 101 is combined with the imaging lens 102, the light ray 103 (incident light flux) incident on the phase filter 101 is refracted by the concave surface 112 described above and locally diverged light. It becomes. The curvature of the concave surface 112 in the phase filter 101 is set so that the divergent light becomes a luminous flux that is locally substantially parallel (on the paper surface) by the imaging lens 102. Locally substantially parallel refers to a state in which light rays for each concave surface 112 that have passed through each concave surface 112 are substantially parallel after passing through the imaging lens 102.

The propagation direction of this local substantially parallel luminous flux is toward the original focal position 3 along the refraction direction of the light beam 2 passing through the center of the annular zone 111. This is because the virtual tangent plane with respect to the concave surface 112 (radial cross section) at the center of the ring zone 111 is perpendicular to the optical axis 1 of the imaging lens 102, and the light rays passing therethrough are connected without being refracted by the phase filter 101. This is because it is clear that the light beam passes through the focal position 3 in the absence of the phase filter 101 because it is incident on the image lens 102. In this way, the substantially parallel light fluxes from the plurality of ring zones 111 overlap in the optical axis direction in the range 104 in the vicinity of the focal point 3. For convenience of explanation, the luminous flux diverging from each ring zone 111 and refracted by the imaging lens 102 is referred to as a substantially parallel luminous flux, but it is actually rotationally symmetric with respect to the optical axis 1. The propagation form of is a luminous flux that propagates along the side surface of the cone.

Such a luminous flux is the same as the luminous flux refracted by the Axicon 201 shown in FIG. The axicon 201 is a conical lens having a bottom surface 202 whose first surface is a flat surface and a conical second surface, and is also called an axicon prism. FIG. 4 schematically shows the relationship between the side cross section of the Axicon 201, the optical axis 1, and the incident parallel luminous flux 203. The parallel light flux 203 incident from the bottom surface 202 of the axicon 201 is refracted by the side surface 204 of the inclined axicon 201, and is uniformly converged by an optical path along a virtual conical surface. In the range 202 in which the luminous flux 203 incident from both sides at an angle overlaps in a rhombus shape, a region 205 is formed in which two cones are bonded to each other with their bottom surfaces facing each other (FIG. In 4, it is colored with the intention of clearly indicating the corresponding area). Within this region 205, a non-diffraction beam is formed in the range 202 in the optical axis direction. The luminous flux from each ring zone 111 in the phase filter 101 of FIG. 1 described above corresponds to a plurality of overlapping light fluxes of the Axicon 201 illustrated in FIG. 4 at different angles, and a plurality of non-diffraction beams overlap each other. Smoothing of the image distribution in the focal direction is achieved.

Subsequently, the configuration of the imaging optical system 150 using the phase filter 101 and the imaging system 300 that performs image processing on the image captured by the imaging optical system 150 will be described with reference to FIG. Here, it is assumed that the object 301 exists at a relatively short distance from the imaging optical system 150 and the object 302 exists at a long distance.

In this case, the reflected light of the object 301 and the object 302 is incident on the imaging lens 102 via the phase filter 101 in the imaging optical system 150, and the blurring is uniform in the direction of the optical axis 1 (point image distribution described above). Images 303 and 304 (due to smoothing in the focal direction of) will be formed. Therefore, the image pickup system 300 has a configuration in which the image sensor 305 is arranged at a position where the images 303, 304 and the like overlap in the optical axis direction.

Further, the image pickup system 300 converts the output signal from the above-mentioned image sensor 305 into an appropriate image format of a still image or a moving image while maintaining the information of the highest resolution that can be output by the image sensor 305, and outputs it as an image signal. The image signal output circuit 306 is provided. Further, the image pickup system 300 includes a monitor output generation circuit 307 that receives an image signal output by the image signal output circuit 306, converts the image signal into a format capable of displaying the display, and outputs the image signal to the monitor display 308. As the image displayed on the monitor display 308, as schematically shown in FIG. 5, images 303 and 304 in which both the near object 301 and the distant object 302 are uniformly blurred can be obtained. However, since such monitor output processing is not essential for the image pickup system 300, there is no problem even if the configuration does not include the monitor display 308 and the monitor output generation circuit 307.

Further, the image pickup system 300 includes a deconvolution preprocessing circuit 309 and a deconvolution filter circuit 310. In the image pickup system 300, the output signal from the above-mentioned image signal output circuit 306 is branched and input to the deconvolution preprocessing circuit 309. As a result, the deconvolution preprocessing circuit 309 converts the digital image data format suitable for the filter calculation in the deconvolution filter circuit 310. Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the second monitor output generation circuit 311. The second monitor output generation circuit 311 converts the input signal from the deconvolution filter circuit 310 into an image format of an arbitrary general still image or moving image, and outputs and displays it as an output signal on the second monitor display 312. When the output is displayed on the second monitor display 312, the image focused on both the near object 301 and the distant object 302 described above is output. At this time, since the phase filter 101 is used, in the output image on the second monitor display 312, the image position of the corresponding object does not shift depending on the distance from the imaging optical system 150, and the objects 301 and 302 do not shift. The image is formed at a position that reflects the original position of.

Subsequently, a simulation for confirming the effect of expanding the depth of focus when the above-mentioned phase filter 101 is adopted will be described. FIG. 6 is a schematic diagram for formulating the shape of the parabolic cross section (that is, the concave surface 112) in the phase filter 101. In this figure, the horizontal axis shows the radial coordinates of the pupil surface, and the vertical axis shows the shape of the phase filter 101. Further, only one cycle is displayed here, and the case where the optical axis position with a radius of 0 has a sharp apex is displayed as even, and the case where the bottom of the parabola is on the optical axis is displayed as odd. The depth of the parabolic cross section is d. This shape is repeated in the radial direction with a period p.

Where r _n is the radius of the n-th annular zone 111, which corresponds to a pupil radius of the imaging optical system 150. Such an annular structure 110 has an annular structure in which the width and the phase difference of the annular 111 are all equal. It is assumed that the phase filter 101 is arranged on the pupil surface of the imaging optical system 150. This may be arranged at the aperture position in the actual imaging optical system 150.

As described above, in the phase filter 101, the cross-sectional shape of the ring band 111 is a parabolic cross-sectional shape, but this is not necessarily limited to the cross-sectional shape described by a quadratic function with respect to the local radial coordinates. is not. For example, it may have a circular or elliptical cross section. In each case, the parabolic cross section is described because the quadratic expansion term with respect to the radius is dominant in the vicinity of the apex of the cross section of the ring zone 111.

Next, deconvolution image processing will be described. The focal length imaging optical system 500 of f as shown in FIG. 7, the distance _{d 0} to have an object given by the light intensity distribution O (x0, y0), the optical image intensity distribution I (x, y) is, It is assumed that the image is formed at a distance d based on the imaging formula in the figure. At this time, if the light intensity distribution of the object is considered as a set of point light sources, the image I (x, y) is formed by superimposing the wave-optical point image distribution PSF (x, y) of the point light source. is there. This point image distribution is based on the aperture of the aperture of the imaging optical system 500, that is, the amplitude transmittance distribution P (X, Y) of the pupil surface.

The Fourier transform, as is generally well known, is an operation that transforms a time or spatial distribution of a physical quantity into its frequency spectrum. By superimposing this point image distribution on the geometric map O (x, y) of the light intensity distribution of the object surface and integrating it, the intensity distribution of the image surface can be obtained.
It can be expressed as. Here, * means the operation of the convolution integral. Furthermore, by applying a Fourier transform to this image plane intensity distribution,
It can be derived that the spatial frequency spectrum of the image plane light intensity distribution is the product of the spatial frequency spectrum of the object surface and the spatial frequency spectrum of the point image distribution. The spatial frequency spectrum of the point image distribution is called the optical transfer function OTF.
It can be expressed as. This operation is called deconvolution. Deconvolution, as can be seen from the form of the equation, requires that the OTF not be zero. Further, even when images of different object distances are mixed in the image plane, if the point image distributions are the same regardless of the focus shift, an ideal optical image can be uniformly obtained by deconvolution.

FIG. 8 shows an example of comparing the processing results of the captured image with and without the phase filter 101 of the first embodiment. The simulation conditions in the simulation result 510 shown in FIG. 8 are focal length 50 mm, effective diameter 15.625 mm, F number 3.2, wavelength 0.5 μm, object distance 710 mm, sensor size 15 mm, ring band pitch 0.8 mm, and so on. The phase difference is 4.24λ, the odd case, the approximate order is 8th, and the image size is 1024 × 1024. The OTF used for the deconvolution uses the average of the defocus 0 mm and 1 mm OTF. The gradation of the image acquired by the camera (that is, the imaging optical system or the imaging system) is assumed to be 12 bits. The original image is a spoke-shaped monochrome image with 0 and maximum brightness, the upper row is the normal acquisition image without the phase filter 101, the middle row is the camera acquisition image when the phase filter 101 of the first embodiment is applied, and the lower row is the deconvolution. It is a result image. Further, the row direction is -2, -1,0,1,2 mm from the left in terms of the amount of defocus on the sensor surface. In this case, a minus means that the sensor is close to the lens, and a plus means that the sensor is far from the lens. At the lower left of the image without the phase filter 101 and after the deconvolution process, the calculation results of the evaluation index values of the image are shown by white numbers. The evaluation index of the image is a numerical value called PSNR (Peak Signal to Noise Radio).
Defined in. Here, Max is the maximum brightness, m and n are the image sizes in the horizontal and vertical directions, I (i, j) is the evaluation image, and O (i, j) is the original image. From this result, it can be seen that the depth of focus is expanded without any noticeable image deterioration in the range of ± 2 mm, although it is not as good as the normal image without defocus. FIG. 9 shows the wave surface aberration of the pupil surface by the phase filter 101 of the first embodiment, that is, the phase distribution 520. However, here, the wave surface aberration of defocus is not included. It can be seen that a parabolic cross-sectional phase shift is applied to each ring zone 111.

Further, FIGS. 10 to 14 show the calculation results of the point image distribution function at this time. In each graph, the horizontal axis is the pixel position of the image, the vertical axis is the brightness, and the calculation area range is 0.938 mm. The graph is a calculation result when the amount of defocus is set to -2, -1, 0, 1, 2 mm from the upper left to the lower right. It can be seen that there is a sign that the focused spots are too narrowed when there is no defocus, but the spot sizes are almost the same in other cases.

In the first embodiment described above, the phase filter 101 of the annular structure 110 having the same annular width (pitch) has been described, but the width of the annular 111 in the phase filter 101 does not have to be the same between the annular bodies. FIG. 15 is a plan view showing the structure of the phase filter 101 of the second embodiment, and FIG. 16 is a side sectional view showing the structure of the phase filter 101 of the second embodiment. In the second embodiment below, an example in which the width of the ring band 111 in the phase filter 101 is narrowed from the optical axis 1 toward the peripheral edge portion 25 will be described. In the examples shown in FIGS. 15 and 16, the width 115 of the outermost ring zone 111, which is closest to the peripheral edge 25, is narrower than the width 116 of the inner peripheral ring band 111. Further, the phase filter 101 alternately includes a ring band 111 including a concave surface 112 acting as a concave lens in the radial direction of the pupil surface with respect to an incident light flux, and a ring band 114 including a convex surface 113 acting as a convex lens. It has a band structure 110.

FIG. 17 shows the wave surface aberration of the pupil surface due to the phase filter 101 having such a structure, that is, the phase distribution 580. In this phase distribution 580, the horizontal axis represents the normalized radius of the pupil plane, and the vertical axis represents the optical path difference (μm). In this phase distribution 580, it can be seen that the larger the normalized radius of the pupil surface, that is, the narrower the width of the annular band 111 is as the peripheral portion 25 of the phase filter 101. When such a structure is adopted in the phase filter 101, the area contributed by each ring zone can be made uniform, and it is less likely to be affected by manufacturing variations. Further, in the second embodiment, the phase difference is the same for all the ring zones 111.

It should be noted that the refraction action of the ring band 111 does not act on the light flux incident between the ring bands 111 (ring bands acting as a concave lens) in the phase filter 101 of the first embodiment, that is, on the steep and sharp convex portion. On the other hand, in the phase filter 101 in which the ring band 111 acting as a concave lens and the ring band 114 acting as a convex lens are alternately arranged as described above, the phase filter 101 is incident on the region of the concave surface 112 of the ring band 111 closest to the ring band 114. The light beam to be generated can also be refracted as desired by the convex lens action of the ring band 114, and its phase distribution 580 does not show a sharp peak as shown in the phase distribution 520 (FIG. 9) of the first embodiment and is smooth. Shape. With the phase filter 101 having such a structure, since the steep and sharp convex portion as described above does not exist between the ring bands, it is possible to suppress the occurrence of chipping in the phase filter 101.

In the above description, for convenience, the concave lens ring band 111 and the convex lens ring band 114 have been described, but in practice, the ring band width is defined with a region in which both are integrated as one ring band.

FIG. 18 shows an image after deconvolution when the phase filter 101 in the second embodiment described above is used. Here, the conditions other than the phase filter are the same as in the case of the first embodiment. The image 590 on the left is the case where there is no defocus (Just focus), and the image 600 on the right is the case where the defocus is 2 mm. Although the image quality is slightly inferior to that of the first embodiment, it can be seen that the depth of focus expansion effect is the same as that of the first embodiment.

Here, the larger the inclination of the concave surface 112 of the phase filter 101, the larger the inclination angle of the refracted light beam, whereas when the depth of the concave surface 112 is the same in the vicinity of the optical axis 1 and in the peripheral portion 25, the optical axis The closer it is to 1, the greater the change in the point where the light beam intersects the optical axis 1. It can be considered that this corresponds to the fact that the contribution to the expansion of the depth of focus increases as the optical axis approaches 1 and decreases as the peripheral portion 25 decreases. Therefore, an example of the phase filter 101 in which the depth of the concave surface 112 becomes deeper toward the peripheral portion 25 will be described below. The depth of the concave surface 112 in the ring band 111 becomes deeper from the optical axis 1 toward the peripheral edge portion 25, but the ring band width is assumed to be constant in all the ring bands.

FIG. 19 is a plan view showing the structure of the phase filter of the third embodiment, and FIG. 20 is a side sectional view showing the structure of the phase filter of the third embodiment. In the examples shown in FIGS. 19 and 20, the depth 117 of the concave surface 112 in the outermost ring zone 111, which is the closest to the peripheral edge 25, is deeper than the depth 118 of the concave surface 112 in the inner peripheral ring zone 111. ing. Further, the phase filter 101 alternately includes a ring band 111 including a concave surface 112 acting as a concave lens in the radial direction of the pupil surface with respect to an incident light flux, and a ring band 114 including a convex surface 113 acting as a convex lens. It has a band structure 110.

FIG. 21 shows the wave surface aberration of the pupil surface due to the phase filter 101 having such a structure, that is, the phase distribution 610. As shown in the phase distribution 610, the change in the optical path difference increases and the amount of change in the phase shift also increases as the depth of the concave surface 112 of the ring zone 111 in the phase filter 101 becomes deeper.

FIG. 22 shows an image after deconvolution when the phase filter 101 in the third embodiment is used. Here, the conditions other than the phase filter are the same as in the case of the first embodiment. The image 620 on the left side of the paper is out of focus-2 mm, the image 630 in the center is out of focus -1 mm, and the image 640 on the right side is out of focus 0 mm. The dB value shown below each image is PSNR (Peak Signal-to-Noise Radio). It can be seen that almost the same image quality as that of the first embodiment is obtained.

As described above, the phase filter 101 is a technique for expanding the effective depth of focus of the imaging optical system 150, and various applications are conceivable. An example of an apparatus using the phase filter 101 will be described below according to the application.

FIG. 23 is a diagram showing a configuration example of the vehicle travel support device 700 according to the second embodiment, and FIG. 24 is a diagram showing a hardware configuration example of the information processing device 710 included in the vehicle travel support device 700 according to the second embodiment. is there. For example, a device that incorporates a phase filter 101 into an in-vehicle camera to photograph an obstacle around the vehicle and detects an obstacle for collision prevention based on an image captured by the in-vehicle camera, that is, a vehicle traveling support device 700 can be assumed. ..

Similar to the imaging system 300 shown in the first embodiment, the vehicle traveling support device 700 includes an image sensor 305, an image signal output circuit 306, a deconvolution preprocessing circuit 309, and a deconvolution filter circuit 310. , Includes information processing device 710. Further, the processing result of the information processing device 710 will be displayed on the monitor display of the car navigation device 730 provided in the vehicle.

In this case, the reflected light of other vehicles 701 and 702 existing around the vehicle equipped with the vehicle traveling support device 700, for example, in front of the vehicle, enters the imaging lens 102 through the phase filter 101 in the imaging optical system 150. , Images 703 and 704 with uniform blurring in the direction of the optical axis 1 are formed. Therefore, in the vehicle traveling support device 700, the image sensor 305 obtains the sensing data of the images 703, 704 and the like, and provides the sensing data to the image signal output circuit 306. Further, the deconvolution preprocessing circuit 309 receives the image signal output from the image signal output circuit 306 and converts it into a digital image data format suitable for the filter calculation in the deconvolution filter circuit 310. Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the information processing device 710. After a predetermined process, the output signal is far from the other nearby vehicle 701 described above. The car navigation device 730 displays an image focused on the vehicle 702 and outputs a voice such as a warning notification corresponding to the display.

The hardware configuration of the information processing device 710 included in the vehicle traveling support device 700 is as follows. The information processing device 710 reads the storage device 701 composed of an appropriate non-volatile storage device such as a hard disk drive, the memory 703 composed of a volatile storage device such as RAM, and the program 702 held in the storage device 701 into the memory 703. It is equipped with a CPU 704 that performs various determinations, calculations, and control processes while performing overall control of the device itself, and a 705 (display, keyboard, mouse, etc.) that accepts user input and outputs results. As the program 702, at least the image recognition algorithm 710 for implementing the functions required for the vehicle traveling support device 700 and the approach determination program 711 are stored. The processing of the program 702 will be described later.

Next, the processing flow executed by the vehicle traveling support device 700 will be described with reference to FIG. 25. The imaging optical system 150 in the vehicle traveling support device 700 images other vehicles 701 and 702, which are objects around the vehicle (s100), and the image sensor 305 senses the images 703 and 704 obtained by this imaging to acquire image data. (S101).

The image sensor 305 provides the above-mentioned image data to the image signal output circuit 306 as an image signal, and the image signal output circuit 306 provides an appropriate still image or an appropriate still image while maintaining the maximum resolution information that can be output by the image sensor 305. It is converted into a moving image format and output as an image signal to the deconvolution preprocessing circuit 309 (s102).

The deconvolution preprocessing circuit 309 receives the image signal output from the image signal output circuit 306 and converts it into a digital image data format suitable for the filter calculation in the deconvolution filter circuit 310 (s103). Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the information processing apparatus 710 (s104).

The information processing device 710 acquires the output data of the deconvolution filter circuit 310, that is, the depth of focus enlarged image, and applies the image recognition algorithm 710 for vehicle recognition to the depth of focus enlarged image from the own vehicle. It simultaneously detects a plurality of objects such as other vehicles 701 and 702 that exist at different distances and are within a certain distance from the own vehicle (s105). The image recognition algorithm 710 performs image processing such as specifying and highlighting a region (corresponding to the vehicle shape) of a predetermined color set of pixels for the pixels constituting the original image. It becomes the algorithm to be performed.

The information processing device 710 displays the images 703 and 704 of the other vehicles 701 and 702 detected in step s105 on the car navigation device 730, and sends a notification message warning that the vehicles are approaching the other vehicles 701 and 702. Display or audio output on the car navigation device 730 (s106). According to such a vehicle traveling support device 700, it is possible to simultaneously detect an obstacle located near the own vehicle and an obstacle located far away from the own vehicle, and the safety during vehicle traveling can be improved.

In addition, a device that incorporates a phase filter 101 into a surveillance camera to photograph a suspicious person or an intruder located in a predetermined surveillance target area and performs a predetermined surveillance process based on an image captured by the surveillance camera, that is, a surveillance device. 750 can be assumed. FIG. 26 is a diagram showing a configuration example of the monitoring device 750 according to the third embodiment, and FIG. 27 is a diagram showing a hardware configuration example of the information processing device 760 included in the monitoring device 750 according to the third embodiment.

Similar to the image pickup system 300 shown in the first embodiment, the monitoring device 750 includes an image sensor 305, an image signal output circuit 306, a deconvolution preprocessing circuit 309, and a deconvolution filter circuit 310, as well as information. It includes a processing device 760. Further, the processing result of the information processing apparatus 760 will be displayed on the monitor display 780.

In this case, the reflected light of the persons 751 and 752 existing in the monitoring target area spreading around the monitoring device 750 enters the imaging lens 102 through the phase filter 101 in the imaging optical system 150, and the direction of the optical axis 1 Images 753 and 754 with uniform blurring will be formed. Therefore, in the monitoring device 750, the image sensor 305 obtains the sensing data of the images 753, 754 and the like, and provides the sensing data to the image signal output circuit 306. Further, the deconvolution preprocessing circuit 309 receives the image signal output from the image signal output circuit 306 and converts it into a digital image data format suitable for the filter calculation in the deconvolution filter circuit 310. Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the information processing device 760. After a predetermined process, the person 752 far from the above-mentioned close person 751 The monitor display 780 displays an image that is also focused on, and outputs a sound such as a warning notification corresponding to the display.

The hardware configuration of the information processing device 760 included in the monitoring device 750 is as follows. The monitoring device 750 reads into the memory 763 a storage device 761 composed of an appropriate non-volatile storage device such as a hard disk drive, a memory 763 composed of a volatile storage device such as RAM, and a program 762 held in the storage device 761. It is equipped with a CPU 764 that performs general control of the device itself and performs various determinations, calculations, and control processes, and a 765 (display, keyboard, mouse, etc.) that accepts user input and outputs results. The program 762 stores at least an image recognition algorithm 770 for implementing the functions required as the monitoring device 750. The processing of the program 702 will be described later.

Next, the processing flow executed by the monitoring device 750 will be described with reference to FIG. 28. The imaging optical system 150 in the monitoring device 750 images the persons 751 and 752 located in the monitored area (s200), and the image sensor 305 senses the images 753 and 754 obtained by this imaging to acquire image data (s201). ).

The image sensor 305 provides the above-mentioned image data to the image signal output circuit 306 as an image signal, and the image signal output circuit 306 provides an appropriate still image or an appropriate still image while maintaining the maximum resolution information that can be output by the image sensor 305. It is converted into a moving image format and output as an image signal to the deconvolution preprocessing circuit 309 (s202).

The deconvolution preprocessing circuit 309 receives the image signal output from the image signal output circuit 306 and converts it into a digital image data format suitable for the filter calculation in the deconvolution filter circuit 310 (s203). Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the information processing apparatus 760 (s204).

The information processing device 760 acquires the output data of the deconvolution filter circuit 310, that is, the depth of focus enlarged image, and applies the image recognition algorithm 770 for person recognition to the depth of focus enlarged image to monitor the device 750. A plurality of people such as 751 and 752 who are present at different distances from the monitoring device 750 and are within a certain distance from the monitoring device 750, that is, in the monitoring target area, are simultaneously detected (s205). The image recognition algorithm 770 specifies, for example, a region (corresponding to the outer shape of a person) of the shape and size of a pixel set of predetermined colors for the pixels constituting the original image, and highlights the image processing. It becomes an algorithm to perform.

The information processing device 760 displays the images 753 and 754 of the persons 751 and 752 detected in step s205 on the monitor display 780, and warns that these persons 751 and 752 have invaded the monitored area. Is displayed or output as audio on the monitor display 780 (s206). According to such a monitoring device 750, the recognition rate of a suspicious person, a criminal, or the like who has invaded or is located in the monitored area is improved regardless of the distance from the imaging optical system.

In addition, a device that incorporates the phase filter 101 into an image pickup device to be authenticated in an authentication device, photographs a predetermined authentication target, and performs a predetermined authentication process based on an image captured by the image pickup device, that is, an authentication device 800. Can be assumed. FIG. 29 is a diagram showing a configuration example of the authentication device according to the fourth embodiment, and FIG. 30 is a diagram showing a hardware configuration example of the information processing device included in the authentication device according to the fourth embodiment.

Similar to the imaging system 300 shown in the first embodiment, the authentication device 800 includes an image sensor 305, an image signal output circuit 306, a deconvolution preprocessing circuit 309, and a deconvolution filter circuit 310, as well as information. It includes a processing device 810. Further, the processing result of the information processing apparatus 810 will be displayed on the monitor display 830.

In this case, the reflected light of the fingers 801 and 802 to be authenticated by the authentication device 800 (eg, fingers, palms, wrists, eyes to be the site of iris authentication, etc., which are the parts of fingerprint authentication and vein authentication) is imaged. It is incident on the imaging lens 102 through the phase filter 101 in the optical system 150, and forms images 803 and 804 with uniform blurring in the direction of the optical axis 1. Therefore, in the authentication device 800, the image sensor 305 obtains the sensing data of the images 803, 804 and the like, and provides the sensing data to the image signal output circuit 306. Further, the deconvolution preprocessing circuit 309 receives the image signal output from the image signal output circuit 306 and converts it into a digital image data format suitable for the filter calculation in the deconvolution filter circuit 310. Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the information processing apparatus 810. After the predetermined processing, the shooting distance from the imaging optical system 150 is short. The monitor display 830 displays the image focused on the finger 801 at the occasion or the finger 802 at the time when the shooting distance is long, and displays the authentication processing result or the audio output accordingly. ..

The hardware configuration of the information processing device 810 included in the authentication device 800 is as follows. The information processing device 810 reads into the memory 813 a storage device 811 composed of an appropriate non-volatile storage device such as a hard disk drive, a memory 813 composed of a volatile storage device such as RAM, and a program 812 held in the storage device 811. It is equipped with a CPU 814 that performs various determinations, calculations, and control processes, and 815 (display, keyboard, mouse, etc.) that accepts user inputs and outputs results. As the program 812, at least the image recognition algorithm 880 for implementing the functions required as the authentication device 800 and the authentication program 881 are stored. The processing of the program 812 will be described later.

Next, the processing flow executed by the authentication device 800 will be described with reference to FIG. 31. The image pickup optical system 150 in the authentication device 800 takes an image of the authentication targets 801 and 802 (s300), and the image sensor 305 senses the images 803 and 804 obtained by this image pickup to acquire image data (s301).

The image sensor 305 provides the above-mentioned image data to the image signal output circuit 306 as an image signal, and the image signal output circuit 306 provides an appropriate still image or an appropriate still image while maintaining the maximum resolution information that can be output by the image sensor 305. It is converted into a moving image format and output as an image signal to the deconvolution preprocessing circuit 309 (s302).

The deconvolution preprocessing circuit 309 receives the image signal output from the image signal output circuit 306 and converts it into a digital image data format suitable for the filter calculation in the deconvolution filter circuit 310 (s303). Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the information processing apparatus 810 (s304).

The information processing device 810 acquires the output data of the deconvolution filter circuit 310, that is, the depth of focus enlarged image, and applies the image recognition algorithm 770 for recognition of the authentication target to the depth of focus enlarged image to provide an authentication opportunity. Although the distance from the image pickup optical system 150 is different for each case, the authentication data of the authentication targets 801 and 802 belonging to the same person are obtained (s305). The authentication data is image data corresponding to images 803 and 804 such as fingerprints, veins, and irises. The image recognition algorithm 770 specifies, for example, a region of the shape and size of a predetermined color set of pixels (corresponding to the shape of a fingerprint, vein, iris, etc.) of the pixels constituting the original image, and highlights the pixels. It is an algorithm that performs image processing such as

The information processing apparatus 810 inputs the image data of the authentication targets 801 and 802 obtained in step s305 into the authentication program 881, extracts the feature data by the authentication program 881, and extracts the extracted feature data and a predetermined template (authentication target). The general authentication process is performed by executing each process of collating with the authentication standard data prepared in advance for each person (s306).

The information processing device 810 displays or outputs the authentication result obtained in step s306 on the monitor display 830 (s307). According to such an authentication device 800, even if the distance of the authentication target (human fingerprint, vein, iris, etc.) to the image pickup optical system 150 changes every time the authentication is performed, the variation in the distance is appropriately absorbed. As a result, the authentication accuracy can be improved.

In addition, a device that incorporates the phase filter 101 into an imaging device for a medical treatment target area in a medical device, photographs a predetermined medical treatment target area, and performs predetermined processing based on an image captured by the imaging device, that is, a medical device 850. Can be assumed. FIG. 32 is a diagram showing a configuration example of the medical device 850 according to the fifth embodiment, and FIG. 33 is a diagram showing a hardware configuration example of the information processing device 860 included in the medical device 850 according to the fifth embodiment.

Similar to the image pickup system 300 shown in the first embodiment, the medical device 850 includes an image sensor 305, an image signal output circuit 306, a deconvolution preprocessing circuit 309, and a deconvolution filter circuit 310, as well as information. It includes a processing device 860. Further, the processing result of the information processing apparatus 860 will be displayed on the monitor display 880.

In this case, the reflected light of the affected areas 851 and 852, which is the medical treatment target area (eg, the organ for medical treatment and examination) in the medical device 850, is transmitted to the imaging lens 102 via the phase filter 101 in the imaging optical system 150. Images 853 and 854 that are incident and have a uniform blur in the direction of the optical axis 1 are formed. Therefore, in the medical device 850, the image sensor 305 obtains the sensing data of the images 853 and 854 and provides the sensing data to the image signal output circuit 306. Further, the deconvolution preprocessing circuit 309 receives the image signal output from the image signal output circuit 306 and converts it into a digital image data format suitable for the filter calculation in the deconvolution filter circuit 310. Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the information processing apparatus 860. After a predetermined process, the affected area 851 is close to the imaging optical system 150. The monitor display 880 displays the image focused on the affected area 852, which is far away from the device.

The hardware configuration of the information processing device 860 included in the medical device 850 is as follows. The information processing device 860 reads into the memory 863 a storage device 861 composed of an appropriate non-volatile storage device such as a hard disk drive, a memory 863 composed of a volatile storage device such as RAM, and a program 862 held in the storage device 861. It is equipped with a CPU 864 that performs general control of the device itself and performs various determinations, calculations, and control processes, and an 865 (display, keyboard, mouse, etc.) that accepts user input and outputs results. The program 862 stores at least an image recognition algorithm 870 for implementing the functions required as the medical device 850. The processing of program 862 will be described later.

Next, the processing flow executed by the medical device 850 will be described with reference to FIG. 34. The imaging optical system 150 in the medical device 850 captures images of the affected areas 851 and 852 in the medical treatment target area (s400), and the image sensor 305 senses the images 853 and 854 obtained by the imaging to acquire image data (s401). ..

The image sensor 305 provides the above-mentioned image data to the image signal output circuit 306 as an image signal, and the image signal output circuit 306 provides an appropriate still image or an appropriate still image while maintaining the maximum resolution information that can be output by the image sensor 305. It is converted into a moving image format and output as an image signal to the deconvolution preprocessing circuit 309 (s402).

The deconvolution preprocessing circuit 309 receives the image signal output from the image signal output circuit 306 and converts it into a digital image data format suitable for the filter calculation in the deconvolution filter circuit 310 (s403). Further, the output signal of the deconvolution preprocessing circuit 309 is filtered by the deconvolution filter circuit 310 and input to the information processing apparatus 860 (s404).

The information processing device 860 acquires the output data of the deconvolution filter circuit 310, that is, the depth of focus enlarged image, applies the image recognition algorithm 870 of the affected area to the depth of focus enlarged image, and images the image in the medical treatment target area. Image data of a plurality of affected areas 851, 852 and the like existing at different distances from the optical system 150 are obtained (s405). The image recognition algorithm 870 specifies, for example, a region of the shape and size of a pixel set of predetermined colors (corresponding to the shape of the affected area) of the pixels constituting the original image, and highlights the image processing. It becomes an algorithm to perform.

The information processing apparatus 860 displays the image data of the affected areas 851 and 852 obtained in step s405 on the monitor display 880 (s406). According to such a medical device 850, the simultaneous visibility of the affected area by the medical staff is enhanced regardless of the perspective of the affected area from the imaging optical system 150. This facilitates the design of optical systems in medical cameras and the like, makes it possible to reduce the number of lenses required, and leads to a reduction in manufacturing costs.

Although the best mode for carrying out the present invention has been specifically described above, the present invention is not limited to this, and various modifications can be made without departing from the gist thereof.

According to the present embodiment, in the depth of focus enlarged image after the image processing of WFC, the in-plane position shift of the image point according to the focus shift is eliminated, and the phase filter of the present embodiment and the optical system using the phase filter are used. , And the imaging system can be used for measuring the position of an object according to the position of a point image. Further, the optical aspherical surface serving as the phase filter has a rotationally symmetric shape, and the mold used for forming the optical aspherical surface also has a rotationally symmetric shape, so that rotary lathe processing is possible when manufacturing the mold. Therefore, it is possible to shorten the manufacturing time of the phase filter mold and reduce the manufacturing cost. Further, by introducing the annular structure in the phase filter, a large uneven shape is unnecessary, that is, the unevenness of the element is reduced, and the deviation of the phase shift amount with respect to the light beam having an angle of view can be alleviated. Further, in the optical system of the present embodiment, an optical system equivalent to forming an axicon in a ring shape can be realized, and it can be applied to an imaging optical system.

Therefore, it is possible to suppress the occurrence of in-plane position shift of the image point according to the focus shift in the depth of focus enlarged image after the image processing of WFC.

The description herein reveals at least the following: That is, in the phase filter of the present embodiment, the annular band may include a concave surface that acts as a concave lens in the radial direction of the pupil surface with respect to the incident light flux. According to this, the optical aspherical surface serving as the phase filter has a rotationally symmetric shape in which the ring-shaped concave surfaces are arranged concentrically, and the mold used for the molding also has a rotationally symmetric shape, and the rotary lathe is processed when manufacturing the mold. Is possible. Therefore, it is possible to shorten the manufacturing time of the phase filter mold and reduce the manufacturing cost. Further, by introducing such an annular structure in the phase filter, a large uneven shape is unnecessary, that is, the unevenness of the element is reduced, and the deviation of the phase shift amount with respect to the light beam having an angle of view can be alleviated.

Further, in the phase filter of the present embodiment, the annular band may alternately include a concave surface acting as a concave lens and a convex surface acting as a convex lens in the radial direction of the pupil surface with respect to the incident light flux. According to this, as compared with the case where the ring band structure is formed only by the ring band acting as a concave lens, the wave surface aberration of the pupil surface due to the phase distribution, that is, the sharp peak in the phase distribution is eliminated, and the phase distribution is smooth. Therefore, it is possible to suppress the occurrence of chipping in the manufactured phase filter.

Further, in the phase filter of the present embodiment, the width of the ring zones may be equal between the ring zones. According to this, since the annular structure in the phase filter is simplified, it is possible to shorten the manufacturing time and the manufacturing cost of the mold used for the molding.

Further, in the phase filter of the present embodiment, the phase difference applied by the ring zones may be equal between the ring zones. According to this, a similar phase shift can be applied between each ring zone in the phase filter.

Further, in the phase filter of the present embodiment, the width of each ring band may be narrowed from the optical axis toward the peripheral edge portion of the phase filter. According to this, it is possible to make the area where each ring zone contributes uniform and to make it less susceptible to manufacturing variations.

Further, in the phase filter of the present embodiment, the phase difference applied by the ring zone may be larger in the peripheral portion of the phase filter than in the vicinity of the optical axis. According to this, the contribution of the phase filter to the expansion of the depth of focus in each ring zone can be leveled regardless of the distance from the optical axis.

Although all of FIGS. 1, 5, 23, 26, 29, and 32 have a configuration in which a phase plate having a single-sided plane and a single-sided phase structure is inserted, the diaphragm or the pupil plane which is the imaging position thereof. Since the effect is the same even if the phase structure is directly formed on the lens surface close to, the phase filter may be integrally formed directly on such a lens surface.

As the lens optical system to which the present invention is applied, not only a lens having a fixed focal length but also a zoom lens optical system having a variable focal length can be applied. If the phase filter is arranged near the aperture or the pupil surface, the effect of expanding the depth of focus may change slightly, but it is basically applicable. As the depth of field that can be photographed is expanded, the focus adjustment between the image and the sensor surface becomes easier, and the focus adjustment mechanism can be eliminated.

1 Optical axis 2 Rays passing through the center of the ring 25 Phase filter peripheral edge 101 Phase filter 102 Imaging lens 103 Ray 104 Luminous flux overlap range 110 Ring structure 111 Ring (concave lens)
112 Concave surface 113 Convex surface 114 Ring band (convex lens)
115 Peripheral ring band width 116 Near optical axis Ring band width 150 Imaging optical system 201 Axicon 202 Light beam overlap range 300 Imaging system 301 Object at a short distance 302 Object at a long distance 303 Image of an object at a short distance 304 Far distance Image of an object in 305 Image sensor 306 Image signal output circuit 307 Monitor output generation circuit 308 Monitor display 309 Deconvolution preprocessing circuit 310 Deconvolution filter circuit 311 Second monitor output generation circuit 312 Second monitor display 700 Vehicle driving support Device 710, 760, 810, 860 Information processing device 750 Monitoring device 800 Authentication device 850 Medical device

Claims (10)

It is an optical system consisting of an imaging optical system having a focal point and a phase filter in which a plurality of rows of rings are formed concentrically around the optical axis.
When a luminous flux parallel to the optical axis is incident on the imaging optical system, the parallel luminous flux is incident on each of the ring zones of the phase filter and has passed through each of the ring zones of the phase filter. The luminous flux is locally made into each divergent light by each of the ring zones of the phase filter.
An optical system characterized in that each of the luminous fluxes transmitted through each of the ring bands of the phase filter and the imaging optical system overlaps in a predetermined range in the optical axis direction at different angles. The optical system according to claim 1, wherein the widths of the annular bands of the phase filter are equal. The optical system according to claim 1, wherein the width of each ring band of the phase filter is narrowed from the optical axis toward the peripheral edge portion of the phase filter. The optical system according to claim 1, wherein the phase difference applied by the ring zones is equal between the ring zones. The optical system according to claim 1, wherein the phase difference applied by the annular band is larger in the peripheral portion of the phase filter than in the vicinity of the optical axis. The optical system according to claim 1, wherein each of the annular bands of the phase filter has a concave surface having a cross-sectional shape that acts as a concave lens having a substantially parabolic shape. The optical system according to claim 6, wherein a convex ring band having a convex surface acting as a convex lens is provided between the ring bands having a concave surface of the phase filter. The optical system according to claim 1, wherein the phase filter is integrally and directly formed on a lens surface constituting the imaging optical system. An imaging optical system comprising the optical system according to claim 1 and an image sensor arranged at a position where the imaging optical system overlaps in an enlarged range before and after the optical axis. An imaging system characterized by performing deconvolution image processing on an image captured by the image sensor according to claim 9 to obtain a depth-of-focus enlarged image.