JP2006139246A - Multifocal lens and imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multifocal lens and an imaging system in which out-of-focus states are approximately the same even when the distances to an object to be imaged are different and in which an image modification process can be realized by a process using the same data, independently of the distance to the object. <P>SOLUTION: In constituting the multifocal lens having a plurality of focal lengths (for example, the multifocal lens 521 having two focal lengths), respective lens parts having the different focal lengths from a plurality of first lens parts having the first focal length to the plurality of Nth lens parts having the Nth focal length (N is an integer of two or more) are integrated. The first-Nth lens parts are concentrically repeated plural times, with the center of the circular or elliptic first lens part. Each lens part may be formed of a diffraction lens. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multifocal lens and an imaging system having a plurality of focal lengths. For example, a desired still image or a moving image can be taken, a close still image such as a digital code is read, and the digital code It can be used as an optical lens and an imaging system to be attached to an information terminal device or the like that can perform recognition processing and various processing based on information of the recognized digital code.

  In general, in an information terminal device having an image input function such as a charge coupled device (CCD), for example, it has a function of photographing a desired image such as a user's own image or a landscape image, It is often very useful to have a function of reading a close-up still image such as a bar code, iris or character. For example, a barcode can represent a lot of information such as an e-mail address, a homepage address, a telephone number, a FAX number, a company name, an affiliation, and a job title. By using it in combination with an image, extremely useful communication can be realized.

  Conventionally, barcode reading as described above has been performed using a dedicated reading scanner. In addition, there is an example in which the barcode is read using an image input device such as a personal computer. In this case, for example, from a near point of the depth of field (for example, about 0.3 m) to infinity. A bar code, which is a close subject, is also read using a standard photographing lens used for photographing a normal subject such as a user or a landscape at a standard distance.

  However, the method of reading a bar code using the dedicated reading scanner as described above is inconvenient in practice because the operation is complicated, laborious and cumbersome. Further, when a barcode is read using a standard photographing lens for photographing a normal subject such as a user or a landscape, the resolution is insufficient. It was difficult to read and recognize information.

  In order to deal with such a problem, the inventor of the present application has developed a standard photographing lens for photographing a normal subject at a standard distance from the near point of the depth of field to infinity, A close-up lens for shooting a close-up subject located at a distance closer than a normal subject at a distance, and rotating a disk with both of these lenses attached, or sliding these lenses Therefore, a portable information terminal device has been proposed in which these lenses having different focal lengths are switched and used (see Patent Document 1). In this portable information terminal device, when photographing a normal subject such as a user or a landscape, an image is formed using a standard photographing lens, and when photographing a close subject such as a barcode, close-up shooting is performed. As a result, it is possible to form an image with a lens for use in the camera, so that the above-mentioned problems associated with the prior art are solved, and not only normal subjects such as users and landscapes, but also close subjects such as barcodes are photographed. However, it has become possible to carry out easily and with high accuracy.

  On the other hand, conventionally, a bifocal lens including two lens portions having different focal lengths has been used as a bifocal contact lens. When a human wears such a contact lens composed of a bifocal lens, an in-focus image formed by two lens portions and an out-of-focus image (so-called out-of-focus image) Is unconsciously selected and seems to be able to see only the in-focus image.

  By the way, if such a bifocal lens is provided in an information terminal device such as a mobile phone or a personal digital assistant (PDA), for example, a standard from the near point of the depth of field (for example, about 0.3 m) to infinity. An ordinary subject (for example, a person or a landscape) at a certain distance is photographed by a long focal lens portion (also referred to as a far lens portion in the present specification) having a long focal length, and on the other hand, A close object (for example, a two-dimensional barcode, an iris, or a character) arranged at a short distance is imaged by a short focus lens portion (also referred to as a near lens portion in the present specification) having a short focal length. By doing so, an image with high resolution can be obtained. And the information terminal device provided with such a bifocal lens has already been proposed by this inventor (refer patent document 2).

  However, in an information terminal device including such a bifocal lens composed of a long focus lens section and a short focus lens section, an optical shutter such as a liquid crystal shutter is provided between the bifocal lens and the image sensor to provide long focus. When the lens unit and the short focus lens unit can be switched, an image with high contrast can be obtained. However, when such a lens unit is not switched, each of the two lens units can be switched. Therefore, there is a problem that it is difficult to obtain a clear image because an image in focus and an image out of focus are overlapped.

  At this time, when a human wears a bifocal contact lens using a bifocal lens as described above, the human unconsciously selects an in-focus image and an out-of-focus image. Although it is considered that only matching images are viewed, a process similar to the image selection process in the human brain is applied to a portable information terminal device such as a normal cellular phone or a portable information terminal. If it can be executed in a short time by a central processing unit (CPU) having the performance of the installed level, the convenience and performance of the information terminal device can be improved, and it can be realized at low cost, which is convenient.

  Therefore, the inventor of the present application can improve the quality of the image picked up by the bifocal lens in a short time, and without using a focusing mechanism, a normal subject at a standard distance and more than this There has been proposed an image modification processing apparatus capable of obtaining a clear image for any of close objects at a short distance (see Patent Document 3). In this image modification processing apparatus, by using a convolution calculation matrix, an in-focus image formed by one lens unit constituting the bifocal lens and an in-focus image formed by the other lens unit A focused image can be obtained from an image where the and overlap.

  In addition, the inventor of the present application shows that, when shooting with a bifocal lens, blur of the same shape does not occur in all pixels of the image sensor, but different shapes of blur occur in each pixel. In view of this, an image modification processing apparatus that further enhances the image modification effect has been proposed (see Patent Document 4).

JP 2002-27047 A (FIG. 1, summary) JP 2002-123825 A (FIG. 1, FIG. 3, FIG. 9, summary) Japanese Patent Laid-Open No. 2003-309723 (FIG. 1, FIG. 2, FIG. 4, FIG. 7, summary) Japanese Patent Laying-Open No. 2005-63323 (FIG. 1, FIG. 2, FIG. 5 to FIG. 9, summary)

  By the way, in the image modification processing apparatus described in Patent Document 3 described above, when obtaining a focused image of a subject using the output signal of the image element and a convolution matrix, the subject to be photographed However, the value of each element of the convolution matrix generally differs depending on whether the subject is a normal subject at a standard distance or a close subject closer to the normal subject. That is, when shooting a normal subject and when shooting a close subject, the lens unit that forms a focused image and the lens unit that forms a blurred image are reversed. Along with this, the out-of-focus state changes. FIG. 18 is a diagram for explaining this situation.

  In FIG. 18, the bifocal lens 900 is usually located at a standard distance from the near point of the depth of field (for example, about 0.3 m) to infinity (also referred to as a long distance in the present specification). A far lens unit 901 for photographing a subject and a near lens unit 902 for photographing a close subject that is closer than a standard distance. Here, the planar shape (frontal shape) of the far lens portion 901 is circular, and the planar shape (frontal shape) of the near lens portion 902 is annular. Further, light from the subject that has passed through the bifocal lens 900 is projected onto the image sensor 903.

  In FIG. 18A, in order to explain the state of defocusing when shooting a normal subject at a standard distance, the normal subject is placed on the optical axis 904 of the bifocal lens 900. A state of an image formed on the image sensor 903 when a point light source 905 (a normal subject having a bright point at only one point) is arranged is shown. In this case, a projection image 906 as shown in FIG. 18A is obtained on the image sensor 903 when viewed from the front. That is, when the point light source 905 is disposed on a normal subject at a standard distance, a focused point-like image 907 is formed by the far lens unit 901, and the near lens unit 902 An annular image 908 having a finite width around the position of the point-like image 907, that is, a blurred image is formed. At this time, the shape of the image 908 that is out of focus is an annular shape according to the planar shape of the near lens portion 902. A projected image 906 is formed by the point-like image 907 that is in focus and the annular image 908 that is out of focus.

  FIG. 18B shows the proximity on the optical axis 904 of the bifocal lens 900 in order to explain the state of defocusing when photographing a close subject that is closer than the standard distance. A state of an image formed on the image sensor 903 when a point light source 909 (a close subject having a bright point at only one point) is arranged on the subject is shown. In this case, a projection image 910 as shown in FIG. 18B is obtained on the image sensor 903 when viewed from the front. That is, when the point light source 909 is arranged on a close subject, a point-like image 911 in focus is formed by the near lens unit 902, and the position of the point-like image 911 is formed by the far lens unit 901. A circular image 912 centered at, that is, a blurred image is formed. At this time, the out-of-focus image 912 has a circular shape in accordance with the planar shape of the far lens unit 901. A projected image 910 is formed in a state where the focused point-like image 911 and the blurred circular image 912 overlap each other.

  For this reason, a transition is made from a standard shooting state in which a normal subject at a standard distance is shot (shooting state in FIG. 18A) to a close-up shooting state in which a close subject is shot (shooting state in FIG. 18B). When shooting or moving in the opposite direction, either the shooting state must be automatically identified, or the shooting state must be switched by, for example, pressing a button or switching a switch. I must.

  However, when switching is performed automatically as described above, a switching circuit is required, which increases the complexity of the device and increases manufacturing costs. On the other hand, the user manually operates buttons and switches. This is not desirable because it places a burden on the user.

  Therefore, even if the distance to the subject to be photographed is different, the state of the out-of-focus state is substantially the same, and the image modification processing for removing the blur is performed regardless of the distance to the subject (for example, If a multifocal lens that can be realized by processing using the same value matrix element, the same value coefficient, the same characteristic, the same function, etc.) can be made, the switching circuit can be made unnecessary. , The burden on the user can be reduced.

  The object of the present invention is to perform the image modification process using the same data regardless of the distance to the subject even if the distance to the subject to be photographed is different. There is a need to provide a multifocal lens and imaging system that can be implemented.

  The present invention is a multifocal lens having a plurality of focal lengths, and when N is an integer equal to or larger than 2, a plurality of first lens portions having a first focal length from a plurality of first lens portions having a plurality of Nth focal lengths. The lens portions having different focal lengths up to the Nth lens portion are integrated and the first to Nth lens portions are arranged concentrically repeatedly around the first lens portion. The planar shape of the first lens unit arranged at the center is a circle, an ellipse, a polygon, or a shape surrounded by other closed ring lines, and is arranged at a position other than the center. The planar shape of the first lens portion and the planar shape of the lens portions other than the first lens portion are annular.

  Here, “the first to Nth lens portions are concentrically repeated a plurality of times” is described, but the lens portion that is closest to the outer peripheral side is not necessarily the Nth lens portion. In the case of repeating the first to third lens portions, the first, second, third,..., First, second, third, first, second, and third in order from the center. The second lens is not limited to the case where the third lens portion is located on the outermost peripheral side, but the first lens, the second lens, the third lens,... The first lens portion may be located on the outermost side, such as the first, second, third,..., First, second, third, and first. Good. The same applies to the case where the first and second lens portions are alternately arranged, and the second lens portion does not necessarily come to the outermost peripheral side, and the first lens portion is closest to the outermost peripheral side. May be.

  In addition, “a shape formed by being surrounded by other closed annular lines” means, for example, a closed annular line that combines a part of a circle and a part of an ellipse, or a closed combination that combines a part of a circle and a straight line. It is a shape formed by being surrounded by an annular line, a closed annular line combining a part of an ellipse and a straight line, a closed annular line combining a part of a circle, a part of an ellipse and a straight line, or the like.

  In the present invention, when a subject is photographed, an in-focus image is formed by one of the first to N-th lens portions, and an in-focus image is formed by the other lens portions. Is formed. At this time, the lens unit that forms an in-focus image changes according to the distance from the multifocal lens to the subject, and accordingly, the lens unit that forms an in-focus image also changes.

  Therefore, since the lens part that forms a defocused image changes according to the distance from the multifocal lens to the subject, the state of defocusing changes strictly according to the distance to the subject. However, in the present invention, since the first to Nth lens portions are repeatedly arranged concentrically a plurality of times, the state of defocusing is substantially the same regardless of the distance to the subject. In other words, conventionally, if the distance to the subject is different, such as the difference between the projection image 906 in FIG. 18A and the projection image 910 in FIG. However, in the present invention, since the lens portions having the same focal length are dispersed and arranged in a plane, the blur is distributed as if it is thinly spread over the entire plane, and the degree of blur is made uniform or smooth. As a result, regardless of the distance to the subject, the state of defocusing can be regarded as substantially the same (see FIG. 7 described later).

  For this reason, even if the distance to the subject to be photographed changes, the image modification processing for removing blur is performed using the same data (for example, the same value matrix element, the same value coefficient, the same characteristic, the same function, etc.). Since it can be realized by the processing used, it is possible to omit the installation of a switching circuit for automatically identifying the shooting state, and it is not necessary to perform switching by manual operation. It is possible to reduce the burden on the person, and the above-mentioned purpose is achieved by these.

  In the multifocal lens described above, it is desirable that each of the first to Nth lens portions is formed by arranging a diffractive lens or a flat surface portion where no diffractive lens is arranged.

  Here, the meaning of “formed with a diffractive lens or formed with a flat surface portion where a diffractive lens is not arranged” means at least one of the first to Nth lens parts. Means that when a lens portion is formed with a diffractive lens and is not provided with a diffractive lens, the lens portion is formed by a flat surface portion. Therefore, all of the first to Nth lens portions may be formed by disposing the diffractive lens. In this case, there is no lens portion formed by the flat surface portion where the diffractive lens is not disposed. In addition, the case where all the 1st-Nth lens parts are formed by the flat surface part in which a diffraction lens is not arrange | positioned is not included.

  In this way, when each of the first to Nth lens portions is a diffractive lens or a flat surface portion, it has a cross-sectional shape like a Fresnel lens or a cross-sectional shape close to this, so that the multifocal lens is entirely Therefore, the weight can be reduced, the degree of freedom in design can be improved, and the manufacturing can be facilitated and the manufacturing cost can be reduced.

  As a multifocal lens having a configuration in which each of the first to Nth lens portions is a diffractive lens or a flat surface portion, more specifically, a lens having the following configuration can be adopted.

  That is, in the multifocal lens described above, N is set to 2, and the first lens portion and the second lens portion are arranged alternately and concentrically with the first lens portion as the center, and the first or second lens portion is arranged. Any one of the lens portions may be formed by disposing a diffractive lens, and the other lens portion may be formed by a flat surface portion where no diffractive lens is disposed.

  Here, the “diffractive lens” may be a concave lens or a convex lens.

  In the N = 2 multifocal lens using the diffractive lens and the flat surface portion described above, the maximum dimension in the thickness direction of the step portion of the diffractive lens passes through the light and air. It is desirable for the light to have a size that is shifted by one wavelength or half wavelength.

  Here, the “wavelength” changes as the color changes, and the wavelength λ of light passing through the air is approximately red, 570 to 700 nanometers, green, 480 to 570 nanometers, and blue, 400 to 480. Nanometer. Therefore, in general, the calculation is made in green, for example, λ = 555 nanometer (wavelength indicating the maximum value of the human visibility curve) or the like. For example, in the case of a night-vision camera for monitoring, the calculation can be made in red (for example, λ = 650 nanometers), and the wavelength can be set according to the camera application. Good. The same applies to multifocal lenses having other configurations described below.

  In this way, when the maximum dimension in the thickness direction of the step portion of the diffractive lens is set to a dimension that is deviated by one wavelength or half wavelength, the wave of light that has exited from the same point light source and passed through the lens part having the same focal length Are matched by shifting two wavelengths or one wavelength, and an image using diffracted light is obtained. In other words, in the case of a size that is shifted by one wavelength, since every other lens unit having the same focal length is arranged, the light that has passed through adjacent lenses that have the same focal length These waves are shifted in phase by two wavelengths so that the phases coincide with each other, and an image using second-order diffracted light is obtained. In addition, when the dimensions are shifted by a half wavelength, the light waves that have passed through adjacent lens parts having the same focal length are shifted in phase by one wavelength so that the phases coincide with each other. An image using folding light is obtained.

  Furthermore, in the multifocal lens described above, N is set to 2, and the first lens portion and the second lens portion are arranged alternately concentrically with the first lens portion as the center, and the first and second lenses The lens portion can be formed by arranging diffractive lenses having different curvatures.

  Here, the “diffractive lenses having different curvatures” may be diffractive lenses that are both concave lenses or diffractive lenses that are both convex lenses. In addition, the meaning that a curvature differs is a meaning that the curvature in the corresponding position (position equidistant from an optical axis) of both diffractive lenses differs. Accordingly, both diffractive lenses may be lenses having a constant curvature or lenses having a non-constant curvature.

  In the N = 2 multifocal lens using the diffractive lenses having different curvatures described above, the stepped portion of the diffractive lens forming either one of the first lens portion and the second lens portion in the thickness direction. As for the maximum dimension, it is desirable that the light passing through the diffractive lens and the light passing through the air be shifted by one wavelength or half wavelength. In this case, as in the case of the N = 2 multifocal lens using a diffractive lens and a flat surface, the phase of the wave of light that has exited from the same point light source and passed through the lens unit having the same focal length Are matched by shifting by two wavelengths or by one wavelength, and an image using diffracted light is obtained.

  In the above-described multifocal lens, N is set to 2, and the first lens portion and the second lens portion are arranged alternately concentrically with the first lens portion as the center, and the first and second lenses Any one of the lens portions may be formed by disposing a diffractive lens by a concave lens, and the other lens portion may be formed by disposing a diffractive lens by a convex lens.

  In the N = 2 multifocal lens using the concave lens and the convex lens, the step portion of the diffraction lens forming at least one of the first and second lens portions is used. It is desirable that the maximum dimension in the thickness direction is such that the light passing through the diffractive lens and the light passing through the air are separated by one wavelength or half wavelength. In this case, as in the case of the N = 2 multifocal lens using a diffractive lens and a flat surface, the phase of the wave of light that has exited from the same point light source and passed through the lens unit having the same focal length Are matched by shifting by two wavelengths or by one wavelength, and an image using diffracted light is obtained.

  Furthermore, in the multifocal lens described above, N is set to 3, and the first to third lens parts are concentrically repeated a plurality of times around the first lens part, and the first to third lenses are arranged. Any one of the lens parts is formed by arranging a diffractive lens by a concave lens, the other one lens part is formed by arranging a diffractive lens by a convex lens, and the remaining one lens part is It can be set as the structure formed by the flat surface part in which a diffraction lens is not arrange | positioned.

  Further, in the above-described diffractive lens by the concave lens, diffractive lens by the convex lens, and N = 3 multifocal lens using the flat surface portion, diffraction that forms at least one of the first to third lens units. The maximum dimension in the thickness direction of the stepped portion of the lens is that the light passing through the diffractive lens and the light passing through the air are shifted by one wavelength, one third wavelength, or two thirds of the wavelength. It is desirable to have dimensions.

  In this way, when the maximum dimension in the thickness direction of the step portion of the diffractive lens is set to a dimension that is deviated by one wavelength, one third wavelength, or two thirds, the same focal point comes out of the same point light source. The phase of the wave of the light that has passed through the lens portion having the distance is matched by shifting by three wavelengths, one wavelength, or two wavelengths, and an image using diffracted light is obtained. In other words, when the dimensions are shifted by one wavelength, the lens portions having the same focal length are arranged at a ratio of one to three at intervals of two, so that the lens portions having the same focal length are the same. The waves of light passing through adjacent ones are shifted in phase by three wavelengths so that the phases coincide with each other, and an image using third-order diffracted light is obtained. In addition, when the dimensions are shifted by one-third wavelength, light waves that have passed through adjacent lens parts having the same focal length are shifted by one wavelength and the phases are matched. An image using the first-order diffracted light is obtained. Furthermore, when the dimensions are shifted by two-thirds of the wavelength, the waves of light that have passed through adjacent lens parts having the same focal length will be shifted in phase by two wavelengths. An image using second-order diffracted light is obtained.

  Further, an N = 2 multifocal lens using the above-described concave lens and a convex lens, or an N = 3 multifocal lens using the concave lens, the convex lens, and the flat surface portion. In the lens, it is desirable that the concave lens and the convex lens have the same or substantially the same curvature.

  Here, “the same or substantially the same curvature” means that the curvature when viewed in absolute value is the same or substantially the same. The meaning that the curvatures are the same or substantially the same means that the curvatures at the corresponding positions (positions equidistant from the optical axis) of both diffractive lenses are the same or substantially the same. Accordingly, both diffractive lenses may be lenses having a constant curvature or lenses having a non-constant curvature.

  When the curvatures of the concave lens and the convex lens are the same or substantially the same, the maximum dimension in the thickness direction of the step portion of the diffractive lens by the concave lens and the maximum dimension in the thickness direction of the step portion of the diffractive lens by the convex lens are Since they coincide or substantially coincide, it is possible to eliminate an unnecessary surface of the lens surface, that is, a surface that does not contribute to image formation.

  The following imaging system of the present invention can be configured using the multifocal lens of the present invention described above.

  That is, the present invention provides an imaging system including an imaging mechanism that images a subject and an image modification processing device that improves the quality of an image captured by the imaging mechanism. And an image pickup device that converts an image formed by the multifocal lens into an electrical signal and outputs the electrical signal. The value of each element of the convolution calculation matrix calculated using the point spread function matrix indicating the state of spreading on the image sensor due to the action of the multifocal lens of the present invention and the subject are imaged by the multifocal lens of the present invention. The matrix indicating the brightness of the light emitted by the subject by performing a convolution operation process using the values of each element of the matrix indicating the output signal of the imaging device for the image obtained in this way And it is characterized in that it is configured to calculate the value of each element.

  Here, as the image modification processing apparatus that performs the reproduction operation using the convolution calculation matrix as described above, for example, the image modification processing apparatus described in Patent Documents 3 and 4 described above (however, a bifocal lens is used). However, the present invention is not limited to this case, and may be applied to a lens having three or more focal points.

  More specifically, in the image modification processing apparatus described in Patent Document 3 described above, the size of the image sensor is M pixels × J pixels, and the matrix of M rows and J columns indicates the brightness of light emitted from the subject. Is a convolution operation calculated based on the following equation (1), where A is A and M is a matrix of M rows and J columns indicating an output signal of the imaging device for an image obtained by imaging a subject with a multifocal lens. A convolution operation for storing a value of a matrix portion including at least a non-zero element among values of each element Q (x, y) of a convolution operation matrix Q of (2M-1) rows (2J-1) columns for processing Matrix storage means and at least a part of each element Q (x, y) stored in the convolution calculation matrix storage means and each element Z (h, k) of the matrix Z of the output signal of the image sensor Each element A of the subject matrix A based on the following equation (2) Is of configuration and a reproducing operation means for calculating the value of t).

Q (x, y) = 1 / c- (W (0,0) -c) / ^cpower
(When x = 0, y = 0)
= -W (x, y) / c ^power
(When other than x = 0, y = 0)
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (1)

A (s, t) = Σ _h Σ _k Q (s−h, tk) Z (h, k)
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (2)

Here, x and y are integers, (1-M) ≦ x ≦ (M−1), (1-J) ≦ y ≦ (J−1), s and t are natural numbers, 1 ≦ s ≦ M, 1 ≦ t ≦ J, h and k are natural numbers, 1 ≦ h ≦ M, 1 ≦ k ≦ J, and W (x, y) is (2M−1) rows (2J−1) ) Value of each element of the matrix W of columns, and this matrix W is a point spread function matrix indicating a state in which the light emitted from one point (m, j) of the subject spreads on the image sensor due to the action of the lens (PSF: point spread function matrix), which is formed by each lens unit when an object having a bright spot at only one point indicated by coordinates (m, j) excluding the end portion is imaged by a multifocal lens. An M-row and J-column matrix Zmj indicating an output signal of the image sensor for an image is taken from coordinates (h, k) satisfying x = hm and y = kj. A matrix portion including non-zero elements of Zmj (h, k) by translating so that W (0,0) = Zmj (m, j) in coordinate transformation to (x, y) Is arranged at the center of the matrix W and the outer part of the matrix part including the non-zero elements arranged at the center is filled with zero elements, and c is a proportional coefficient, and is the overall area of the multifocal lens Is a value of the ratio of the area of the lens part that forms an in-focus image, power is a real number that is a power of c, 1 ≦ power ≦ 2, and Σ _h is h = 1 to M Σ _k is the sum of k = 1 to J.

Further, in the image modification processing device described in Patent Document 4 described above, the size of the image sensor is M pixels × J pixels, the matrix of M rows and N columns indicating the brightness of light emitted from the subject is A, Image formation of light from one point (m, j) in the object coordinate system, where Z is a matrix of M rows and J columns indicating the output signal of the image sensor for an image obtained by imaging the subject with a multifocal lens. When the subject coordinate system and the image coordinate system are set so that the position is one point (m, j) in the image coordinate system, all or part of each coordinate (m, j) is expressed by the following equation (1 ′). Each element Q _{m, j} (x, y) of the convolution matrix Q _{m, j} of (2M-1) rows (2J-1) columns with respect to the coordinates (m, j) for performing the convolution operation processing calculated based on Convolution operation matrix storage means for storing a matrix part value including at least a non-zero element among the values of Each element stored in the operation matrix storage means convolution _{Q m, j (x, y} ) and the value of each element Z (m + x, j + y) of the matrix Z of at least some of the values and the output signal of the imaging element of the And a reproducing operation means for calculating the value of each element A (m, n) of the subject matrix A based on the following equation (2 ′).

Q _{m, j} (x, y) = 1 / W _{m, j} (0,0)
(When x = 0, y = 0)
= −W _{m, j} (−x, −y) / W _{m, j} (0,0) ^power
(When other than x = 0, y = 0)
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (1 ')

A (m, j) = Σ x Σ y Q m, j (x, y) Z (m + x, j + y)
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (2 ')

Here, x and y are integers, (1-M) ≦ x ≦ (M−1), (1-J) ≦ y ≦ (J−1), m and j are natural numbers, and 1 ≦ m ≦ M, 1 ≦ j ≦ J, and W _{m, j} (x, y) is the value of each element of the matrix W _{m, j} of (2M−1) rows (2J−1) columns. W _{m, j} is a point spread function matrix indicating a state in which light emitted from one point (m, j) of the subject spreads on the image sensor due to the action of the lens, and W _{m, j} (0, 0) Is the value of the output signal of the pixel located in the center part of the spread, W _{m, j} (−x, −y) is the value of the output signal of the pixel located in the peripheral blur part, and power is W _m, a real number which is a power number of j (0,0), a 1 ≦ power ≦ 2, the sigma _x, the sum of x = (1-M) ~ (M-1), Σ y is , Y = (1-J) to (J-1) Is the sum.

Also, the convolution matrix storage means, the coordinates (m, j) convolution matrix for Q _m, convolution matrix Q _m of coordinates aligned on a straight line extending from the optical axis position in one direction of _{j, j} Is selected as a sampling matrix _, only the value of each element Q _{m, j} (x, y) of this sampling matrix Q _{m, j} is stored _, and each element of the convolution matrix Q _{m, j} for other coordinates is stored. Concerning the value of Q _{m, j} (x, y), a convolution calculation matrix rotation calculating means is provided, and each element of the sampling matrix Q _{m, j} is utilized by the convolution calculation matrix rotation calculating means by utilizing the axial symmetry of the lens. The arrangement of the values of Q _{m, j} (x, y) may be calculated by rotating about the optical axis position.

  The image modification processing apparatus described in Patent Documents 3 and 4 as described above includes three light beams corresponding to the colors separated into R, G, and B using a prism. You may combine with the imaging mechanism of the structure projected on an image element (what is called 3 plates), and the pixel for each color of R, G (Gb and Gr), B is the pixel for the same color (however, the pixel for Gb and Gr May be combined with an imaging mechanism having a configuration in which Bayer array image elements are arranged so that every other pixel is arranged vertically and horizontally.

  When combined with an imaging mechanism using a prism, the same convolution matrix is used for the output signal of the R image element, the output signal of the G image element, and the output signal of the B image element. Image modification processing can be performed.

  When combined with an image pickup mechanism having an image element having a Bayer array, an image pickup mechanism having the structure in which signals of all colors of R, G, and B are output for each pixel constituting the image element (same color) Since only one pixel for each pixel is provided vertically and horizontally, the output signals of the missing pixels between them are interpolated using the output signals of the surrounding pixels of the same color (for example, hardware The image pickup mechanism is configured to output not only the signals of the pixels actually provided but also the pixels of the same color in the vertical and horizontal directions. May be combined every other pixel, so that the number of pixels is a quarter of the total.

  As in the former case, when receiving an output signal subjected to interpolation processing from an imaging mechanism having a configuration with Bayer array image elements, as in the case of combining with an imaging mechanism using a prism, Image modification processing using the same convolution matrix can be performed on the G signal and the B signal.

As in the latter case, when an output signal that has not been subjected to interpolation processing is received from an imaging mechanism having an image element with a Bayer array (therefore, the number of signals for the same color is ¼). , W ′ or W _{m, j} ′ from which the number of rows and columns is halved and the number of elements is _¼ from the monochrome point spread function matrix W or W _{m, j} without missing elements Is created, and based on these W ′ or W _{m, j} ′, the number of rows and the number of columns are each halved and the number of elements is 4 minutes using the formula (1) or the formula (1 ′). The value of each element of the convolution matrix Q ′ or Q _{m, j} ′ to be 1 may be calculated, or based on the monochrome point spread function matrix W or W _{m, j} without missing elements, the formula ( 1) or a convolution matrix without missing elements using the formula (1 ′) Q or Q _m, after calculating the value of each element of _j, these convolution matrix Q or Q _m, from _j, the number of rows and columns is number of elements in each half a quarter A convolution matrix Q ′ or Q _{m, j} ′ may be created. At this time, the convolution calculation matrix Q ′ or Q _{m, j} ′ obtained by any procedure can be set to the same matrix for each color of R, G, and B. Then, using the output signal of the number of signals received from the imaging mechanism and the convolution operation matrix Q ′ or Q _{m, j} ′ of the number of elements of 1/4, the expression (2) or the expression ( After performing the convolution operation processing for each color based on 2 ′), R, G, and B may be combined.

From a monochrome point spread function matrix W or W _{m, j} with no missing elements, W ′ or W _{m, j} has half the number of rows and columns and one-fourth the number of elements, respectively. When creating ', you can collect and add the values of surrounding elements. For example, if the element of W ′ corresponding to W (u, v) is W ′ (u ′, v ′), W ′ (u ′, v ′) = a × W (u−1, v−1). ) + B × W (u−1, v) + a × W (u−1, v + 1) + b × W (u, v−1) + W (u, v) + b × W (u, v + 1) + a × W (u + 1) , V−1) + b × W (u + 1, v) + a × W (u + 1, v + 1), W ′ (u ′, v ′) can be obtained. Here, for example, a = 0.25, b = 0.5, and the like may be set, but a = b = 0 and W ′ (u ′, v ′) = W (u, v) may be set. This also applies to the case where W _m, the _j W _m, creating a _j '. Further, a convolution operation matrix Q ′ or Q _{m, j} ′ in which the number of rows and the number of columns is 1/2 and the number of elements is 1/4 from the convolution operation matrix Q or Q _{m, j} without missing elements is obtained. The same applies to the creation.

  The present invention also provides an imaging system including an imaging mechanism that images a subject and an image modification processing device that improves the quality of an image captured by the imaging mechanism. A multifocal lens and an image sensor that converts an image formed by the multifocal lens into an electrical signal and outputs the electrical signal. The load addition calculation process is performed using the inverse function of the transfer function of the point spread function indicating the state where the light emitted from one point spreads on the image sensor due to the action of the multifocal lens. It is a feature.

  Here, “a configuration in which load addition calculation processing is performed using an inverse function of a transfer function of a point spread function as a correction function” means, for example, a point spread function (PSF) of a multifocal lens expressed by a spatial coordinate axis. Is subjected to coordinate transformation by Fourier transformation or z transformation to obtain the transfer function H of the PSF of the multifocal lens, the inverse function 1 / H of this transfer function H is subjected to inverse Fourier transformation or inverse FFT, and the like. A filter coefficient sequence of the function 1 / H, that is, a reforming filter coefficient is obtained, and a load addition calculation process is performed using the reforming filter coefficient.

In the above description, the point spread function matrix is a monochrome point spread function matrix W. However, if the lens characteristic has chromatic aberration, the point for the color corresponding to each color of the image sensor.・ A spread function matrix is used to calculate the value of each element of the convolution matrix Q ′ or Q _{m, j} ′, where the number of rows and columns is 1/2 and the number of elements is 1/4 for each color. May be. The same applies to the case of obtaining the filter coefficient string of the transfer function H of the point spread function and its inverse function 1 / H.

  As described above, according to the present invention, the first to Nth lens portions having different focal lengths are arranged repeatedly concentrically, so that the distance to the subject to be photographed is different. However, the out-of-focus state is almost the same, and the image modification process can be realized with the same data regardless of the distance to the subject. Since the installation of the switching circuit can be omitted and the manual switching is not necessary, the burden on the user can be reduced.

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

[First Embodiment]
FIG. 1 shows an overall configuration of an imaging system 10 including a multifocal lens 21 according to the first embodiment of the present invention. FIG. 2 shows a detailed configuration of the multifocal lens 21. Further, FIG. 3 is an explanatory diagram showing a state in which a projected image is formed on the image sensor 24 when a subject having a bright spot at only one point (coordinates (m, j)) is imaged by the multifocal lens 21. 4 shows a subject at a relatively long distance (in this embodiment, a normal subject at a standard distance from the near point of the depth of field to infinity is taken as an example). Shooting with the multifocal lens 21 and shooting with the multifocal lens 21 of an object at a relatively short distance (in this embodiment, as an example, a close subject closer to the standard distance). It is explanatory drawing which shows that the state of a method of defocusing differs by the case where it does. The imaging system 10 includes, for example, an imaging system provided in a portable information terminal device such as a mobile phone (including PHS) and a personal digital assistant (PDA), or a personal computer and a camera connected thereto. Imaging system or the like.

  In FIG. 1, an imaging system 10 includes an imaging mechanism 20 that images a subject, an image modification processing device 30 that improves the quality of an image captured by the imaging mechanism 20, and a quality that is improved by the image modification processing device 30. Display means 40 for displaying the improved image.

  The imaging mechanism 20 includes a multifocal lens 21 that captures an image of an object and an image sensor 24 that captures an image formed by the multifocal lens 21.

  In FIG. 2, the multifocal lens 21 of the present embodiment is a multifocal optical system (in this embodiment, a bifocal optical system) centered on a circular lens portion 22A having a circular planar shape (front shape). By arranging a plurality of (three in the present embodiment) annular lens portions 23A, 22B, and 23B having a planar shape (front shape) on the outer peripheral side in this order, the first lenses having different focal lengths are arranged. And second lens portions are alternately arranged concentrically. That is, the multifocal lens 21 has a plurality of first and second circular lens portions 22A and 22B having a first focal length and a second focal length different from the first focal length. A plurality of annular lens portions 23A and 23B as second lens portions are arranged on the same surface and integrated. Therefore, the adjacent lens portions are disposed in contact with each other, and the circular lens portion 22A and the annular lens portions 23A, 22B, and 23B are disposed concentrically, so that each of these lens portions 22A, 22A, The optical axes of 23A, 22B, and 23B coincide.

  The circular lens portion 22A and the annular lens portion 22B that are the first lens portions constitute the far lens portion 22 that converges at a long focal length, and the short lens portions 23A and 23B that are the second lens portions are short. A near lens portion 23 that converges at a focal length is configured. For example, the far lens unit 22 is a lens for photographing a normal subject (for example, a person or a landscape) at a standard distance from a near point of the depth of field (for example, about 0.3 m) to infinity. The near lens unit 23 is a lens unit for photographing a close subject (for example, a barcode, an iris, a character, or the like) located at a distance (for example, less than 10 cm) shorter than a standard distance.

  In the first embodiment, a plurality of annular lens portions 23A, 22B, and 23B having a circular planar shape are arranged concentrically around the circular lens portion 22A having a circular planar shape. However, the planar shape of each lens part is not limited to these shapes. For example, an elliptical shape or a polygonal shape such as an elliptical shape or a polygonal shape is mainly used. It is good also as a multifocal lens provided with the structure by which each annular lens parts, such as a polygon, are arrange | positioned concentrically.

  In FIG. 1, for example, a complementary metal-oxide semiconductor (CMOS), a charge-coupled device (CCD), or the like can be used as the imaging device 24. Here, the size of the image sensor 24 is assumed to be M pixels in the vertical direction × J pixels in the horizontal direction (see FIG. 3).

  The image modification processing device 30 includes an output signal storage unit 31 that extracts and stores an output signal of the image sensor 24, and each element Q (x, y) of a convolution calculation matrix Q calculated in advance based on the following equation (1). ) Is provided with convolution operation matrix storage means 32 for storing at least a part of the value and reproduction calculation means 33 for performing calculation processing for reproducing the subject. Since this image modification processing apparatus 30 is the same as the image modification processing apparatus described in Patent Document 3 described above, detailed description will be omitted below and only a brief description will be given.

Q (x, y) = 1 / c- (W (0,0) -c) / ^cpower
(When x = 0, y = 0)
= -W (x, y) / c ^power
(When other than x = 0, y = 0)
(1)

  Here, x and y are integers, (1-M) ≦ x ≦ (M−1), (1-J) ≦ y ≦ (J−1), s and t are natural numbers, 1 ≦ s ≦ M, 1 ≦ t ≦ J, h and k are natural numbers, 1 ≦ h ≦ M, 1 ≦ k ≦ J.

  W (x, y) is a value of each element of the matrix W of (2M-1) rows (2J-1) columns, and this matrix W comes from one point (m, j) of the subject. This is a point spread function matrix (PSF) indicating a state in which light spreads on the image sensor 24 due to the action of the lens, and only one point indicated by coordinates (m, j) excluding the end portion shines. When a pointed subject is imaged by the multifocal lens 21, a matrix Zmj of M rows and J columns indicating an output signal of an image formed by the far lens unit 22 and the near lens unit 23 is expressed as x = hm, y Zmj () by translating so that W (0,0) = Zmj (m, j) in coordinate conversion from coordinates (h, k) satisfying = k−j to coordinates (x, y). h, k) is arranged in the center of the matrix W and includes the matrix part including the non-zero elements. It is constructed by filling the outer portion of the matrix portion containing the non-zero element disposed at zero element.

In the present embodiment, it is assumed that blur of the same shape is formed in all the pixels of the image sensor 24, and the point spread function matrix W is assumed to be a common matrix for each pixel. However, as in the image modification processing apparatus described in Patent Document 4 described above, a different matrix W _{m, j for} each coordinate (m, j) is considered in consideration of the occurrence of different shapes of blur at each pixel. It is good. In this case, the convolution matrix Q _{m, j} is different for each coordinate (m, j), but the convolution matrix Q _{m, j} for each coordinate (m, j). Is a convolution operation matrix Q _{m, j for} coordinates aligned on a straight line extending in one direction from the optical axis position using the axial symmetry of the lens as in the image modification processing apparatus described in Patent Document 4. May be calculated by rotating around the optical axis position.

  Further, c is a proportionality coefficient, which is a value of the ratio of the area of the lens portion that forms a focused image to the entire area of the multifocal lens 21. In the present invention, the same data is obtained regardless of whether in the standard photographing state or the close-up photographing state, that is, when either the far lens unit 22 or the near lens unit 23 is a lens unit that forms a focused image. In the first embodiment, which is a bifocal lens, the value of c is set to be in the vicinity of 0.5 from the viewpoint that image modification processing can be performed using. Note that, in the case of a trifocal lens as in the sixth embodiment described later, the value of c is in the vicinity of 1/3.

  Further, power is a real number that is a power of c, and 1 ≦ power ≦ 2. The power value may be determined according to the value c. At this time, when the value of c is in the vicinity of 0.5, the power value needs to be a value other than 2. More specifically, when the value of c is in the vicinity of 0.5, the power value is 1 or more and less than 2, more preferably 1. On the other hand, when the value of c is other than 0.5, it is set to 1 or more and 2 or less.

  Further, in the above description, the description has been given on the assumption that the lens unit that forms an in-focus image of the multifocal lens 21 forms an image without blur. Accordingly, it is assumed that an image formed by a lens unit that forms an in-focus image has a non-zero element only in W (0, 0) and its value is c.

  However, in reality, an image formed by a lens unit that forms an in-focus image may be blurred due to aberrations or the like, so an image formed by a lens unit that forms an in-focus image. Extends around W (0,0), and the elements around W (0,0) can also be non-zero elements.

  Therefore, when blurring due to aberration or the like occurs in an image formed by the lens unit that forms an in-focus image, and elements other than W (0,0) are non-zero elements, W (0,0) ) And non-zero element values generated around W (0,0) are summed, and the total value is re-entered into W (0,0) as the value of c, and around W (0,0) The value of each non-zero element generated in is corrected to zero, and each element Q () of the convolution matrix Q is used by using the value of each element W (x, y) created through these correction work. What is necessary is just to calculate the value of x, y).

  On the other hand, for the image formed by the lens unit that forms a defocused image, the same data is used regardless of which of the far lens unit 22 or the near lens unit 23 is a lens unit that forms a defocused image. From the standpoint that image modification processing can be performed using the image, the value of each element W (x, y) is set to the same value in any shooting state, and each element of the convolution calculation matrix Q is set. What is necessary is just to calculate the value of Q (x, y). For example, among the plurality of lens parts having the same focal length, the lens part arranged on the outermost peripheral side (in this embodiment, the annular lens part 22B constituting the far lens part 22 and the annular part constituting the near lens part 23). The outer peripheral line of the blurred image formed by the lens unit 23B is formed for each lens unit having each focal length (in this embodiment, as shown in FIG. 4, an annular lens is used). The outer peripheral line 63A of the defocused annular image 63 formed by the portion 22B and the outer peripheral line 53A of the defocused annular image 53 formed by the annular lens portion 23B are formed. The value of each element W (x, y) can be made uniform within a range surrounded by the outermost peripheral line (in this embodiment, the outer peripheral line 53A) among these outer peripheral lines. . Further, the value of each element W (x, y) may be smoothly changed within this range.

  The convolution operation matrix storage means 32 stores at least a part of the values of the respective elements Q (x, y) of the convolution operation matrix Q by arranging them as shown in the table according to the order of arrangement of x and y. Since it is at least a part, the whole may be stored. However, in order to reduce the calculation capacity and the memory capacity, it is preferable to store only the matrix part including the non-zero elements. Therefore, here, the description will be made assuming that only the matrix portion including the non-zero elements is stored.

  The reproduction calculation means 33 stores the value of each element Q (x, y) of the convolution calculation matrix Q stored in the convolution calculation matrix storage means 32 (each value of the matrix part including the non-zero elements) and an output signal. Using the values of the elements Z (h, k) of the matrix Z indicating the output signal of the image stored in the means 31, the elements A (s, t) of the matrix A of the subject based on the following equation (2) ) Is calculated. Since the elements other than the matrix part including the non-zero elements among the elements Q (x, y) of the convolution arithmetic matrix Q, that is, the parts not stored in the convolution arithmetic matrix storage means 32 are zero elements. No calculation is performed.

A (s, t) = Σ _h Σ _k Q (s−h, tk) Z (h, k)
(2)

Here, Σ _h is the sum of h = 1~M, is Σ _k, which is the sum of k = 1~J.

  The output signal storage means 31 and the convolution calculation matrix storage means 32 include, for example, a hard disk, ROM, EEPROM, flash memory, RAM, MO, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD -RAM, FD, magnetic tape, or a combination thereof can be employed.

  Further, the reproduction calculation means 33 is a variety of information terminal devices constituting the imaging system 10 (for example, portable information terminal devices such as mobile phones and portable information terminals, personal computers connected with cameras, surveillance camera devices, etc.) ) Is implemented by a central processing unit (CPU) provided inside the CPU and one or a plurality of programs that define the operation procedure of the CPU.

  As the display means 40, for example, a liquid crystal display, a CRT display, a projector and a screen, or a combination thereof can be employed.

  In such a first embodiment, when photographing is performed using the multifocal lens 21, the following optical imaging system is configured.

  FIG. 4 shows an optical imaging system in the multifocal lens 21 shown in FIG. FIG. 4A shows an object at a relatively long distance suitable for photographing by the far lens unit 22 having a long focal length on the optical axis 27 of the multifocal lens 21, for example, a near point of the depth of field. An optical imaging system is shown in which a point light source 28 is arranged on a normal subject (for example, a person or landscape) at a standard distance from (for example, about 0.3 m) to infinity.

  In the case of FIG. 4A, a projection image 50 as shown in FIG. 4A is obtained on the image sensor 24 when viewed from the front. That is, when the point light source 28 is arranged on a subject at a distance suitable for photographing with the far lens unit 22, a point-like shape in focus by the circular lens unit 22A and the annular lens unit 22B constituting the far lens unit 22 is provided. Focusing on the outer peripheral side of the image 51, the annular image 52 by the annular lens portion 23 </ b> A, and the outer peripheral side of the annular image 52 on the outer peripheral side, such as the annular image 53 by the annular lens portion 23 </ b> B, is out of focus. The projected image is projected.

  On the other hand, FIG. 4B shows an object at a relatively short distance suitable for photographing by the near lens unit 23 having a short focal length on the optical axis 27 of the multifocal lens 21, for example, a standard distance. 2 shows an optical imaging system in which a point light source 29 is arranged on a close subject (for example, a barcode, an iris, a character, etc.) at a short distance.

  In the case of FIG. 4B, a projection image 60 as shown in FIG. 4B is obtained on the image sensor 24 when viewed from the front. That is, when the point light source 29 is disposed on a subject at a distance suitable for photographing by the near lens unit 23, a point-like image 61 in focus by the annular lens units 23A and 23B constituting the near lens unit 23 is provided. A circular image 62 by the circular lens portion 22A is projected on the outer peripheral side, and a defocused image such as an annular image 63 by the annular lens portion 22B is projected on the outer peripheral side of the circular image 62. The

  In the present embodiment, when considering the case of FIG. 4A and the case of FIG. 4B together, in each case, the out-of-focus image is formed by the annular lens portion 23B. Since it can be considered that the image extends to the position of the outer circumferential line 53A of the out-of-focus annular image 53 (in the case of FIG. 4B, it extends to the position of the outer circumferential line 63A. 4 (a) can be regarded as extending to the position of the outer peripheral line 53A.) In the range surrounded by the outer peripheral line 53A, the values of the elements W (x, y) of the PSF matrix W are made uniform, Alternatively, the value of each element Q (x, y) of the convolution calculation matrix Q can be calculated so as to change smoothly.

  According to such 1st Embodiment, there exist the following effects. That is, when a normal subject and a close subject at a standard distance are photographed using the multifocal lens 21, as shown in FIG. 4, the state of defocusing depends on the photographing state. In other words, in the multifocal lens 21, since the first and second lens portions are concentrically repeated a plurality of times, that is, alternately arranged, the subject is changed. Regardless of the distance up to, the out-of-focus state is almost the same.

  Therefore, even if the distance to the subject to be photographed changes, image modification processing for removing blur is realized by processing using the same data, that is, each element Q (x, y) of the convolution calculation matrix Q It is possible to perform image modification processing with the same value set to. For this reason, the installation of the switching circuit for automatically identifying the photographing state can be omitted, and it is not necessary to perform switching by manual operation, so that the burden on the user can be reduced.

[Second Embodiment]
FIG. 5 shows a detailed configuration of the multifocal lens 221 according to the second embodiment of the present invention. Also, FIG. 6 shows many subjects that are relatively far away (in this embodiment, as an example, a normal subject that is at a standard distance from the near point of the depth of field to infinity). When shooting with the focus lens 221, a subject at a relatively short distance (in this embodiment, as an example, a close subject closer than a standard distance) is shot with the multifocal lens 221. It is explanatory drawing which shows that the state of the method of defocusing differs with the case. The multifocal lens 221 is a lens used by being incorporated in an imaging system similar to the imaging system 10 (see FIG. 1) of the first embodiment, and the configuration of the multifocal lens is the first in the imaging system as a whole. Unlike the first embodiment, other configurations and functions are the same as those of the first embodiment. Therefore, the same portions are denoted by the same reference numerals, and detailed description thereof will be omitted. The following description will focus on the different portions.

  In FIG. 5, a multifocal lens 221 is a multifocal optical system (in this embodiment, a bifocal optical system) centered on a circular lens portion 222 </ b> A whose planar shape (frontal shape) is circular, and is planar on the outer peripheral side thereof. A plurality of (seven in this embodiment) annular lens portions 223A, 222B, 223B, 222C, 223C, 222D, and 223D having a circular shape (front shape) are arranged in this order, so that their focal lengths are different from each other. The first lens portion and the second lens portion are alternately arranged concentrically. In other words, the multifocal lens 221 includes a circular lens unit 222A and annular lens units 222B, 222C, and 222D as a plurality of first lens units having a first focal length, and a second different from the first focal length. A plurality of annular lens portions 223A, 223B, 223C, and 223D as a plurality of second lens portions having a focal length are arranged on the same surface and integrated. Therefore, the adjacent lens portions are disposed in contact with each other, and the circular lens portion 222A and the annular lens portions 223A, 222B, 223B, 222C, 223C, 222D, and 223D are disposed concentrically. The optical axes of these lens portions 222A, 223A, 222B, 223B, 222C, 223C, 222D, and 223D are the same.

  The circular lens portion 222A and the annular lens portions 222B, 222C, and 222D that are the first lens portions constitute a far lens portion 222 that converges with a long focal length, and the annular lens portions 223A and 223A that are the second lens portions. 223B, 223C, and 223D constitute a near lens portion 223 that converges with a short focal length. For example, the far lens unit 222 is a lens for photographing a normal subject (for example, a person or a landscape) at a standard distance from a near point of the depth of field (for example, about 0.3 m) to infinity. The near lens unit 223 is a lens unit for photographing a close subject (for example, a barcode, an iris, a character, or the like) at a distance (for example, less than 10 cm) closer than a standard distance.

  In the second embodiment, a plurality of annular lens portions 223A, 222B, 223B, 222C, 223C, and 222D having a circular planar shape around the circular lens portion 222A having a circular planar shape at the center are provided. , 223D is described as an example, but the planar shape of each lens portion is not limited to these shapes, for example, lenses such as ellipse and polygon It is good also as a multifocal lens provided with the structure by which each annular lens part, such as an ellipse and a polygon, is arrange | positioned concentrically centering | focusing on a part.

  In such a second embodiment, when photographing is performed using the multifocal lens 221, the following optical imaging system is configured.

  FIG. 6 shows an optical imaging system in the multifocal lens 221 shown in FIG. FIG. 6A shows an object at a relatively long distance suitable for photographing by the far lens unit 222 having a long focal length on the optical axis 227 of the multifocal lens 221, for example, a near point of the depth of field. An optical imaging system is shown in which a point light source 228 is arranged on a normal subject (for example, a person or landscape) at a standard distance from (for example, about 0.3 m) to infinity.

  In the case of FIG. 6A, a projected image 250 as shown in FIG. 6A is obtained on the image sensor 24 when viewed from the front. In other words, when the point light source 228 is disposed on a subject at a distance suitable for photographing by the far lens unit 222, the focus by the circular lens unit 222A and the annular lens units 222B, 222C, and 222D constituting the far lens unit 222 is increased. Centered on the combined dot-shaped image 251, annular images 252, 253, 254, and 255 are formed by the annular lens portions 223 A, 223 B, 223 C, and 223 D constituting the near lens portion 223 on the outer peripheral side thereof. A defocused image is projected in a state of being arranged in order from the center toward the outer peripheral direction.

  On the other hand, FIG. 6B shows an object at a relatively short distance suitable for photographing by the near lens unit 223 having a short focal length on the optical axis 227 of the multifocal lens 221, for example, a standard distance. 2 shows an optical imaging system in which a point light source 229 is arranged on a close subject (for example, a barcode, an iris, a character, etc.) at a short distance.

  In the case of FIG. 6B, a projection image 260 as shown in FIG. 6B is obtained on the image sensor 24 when viewed from the front. That is, when the point light source 229 is disposed on the subject at a distance suitable for photographing with the near lens unit 223, the in-focus points by the annular lens units 223A, 223B, 223C, and 223D constituting the near lens unit 223 are arranged. A circular image 262 formed by the circular lens portion 222A on the outer peripheral side of the circular image 261, and circular images 263, 264 formed by the annular lens portions 222B, 222C, and 222D on the outer peripheral side of the circular image 262. A blurred image such as H.265 is projected.

  In the present embodiment, when considering the case of FIG. 6A and the case of FIG. 6B together, in each case, the out-of-focus image is formed by the annular lens portion 223D. Since it can be considered that the image extends to the position of the outer peripheral line 255A of the defocused annular image 255, the range surrounded by the outer peripheral line 255A (however, the defocused blur formed by the annular lens portion 222D). When the outer circumferential line 265A of the annular image 265 is located on the outer circumferential side, it is set as a range surrounded by the outer circumferential line 265A), and the value of each element W (x, y) of the PSF matrix W is The value of each element Q (x, y) of the convolution matrix Q can be calculated by making it uniform or changing smoothly.

  By the way, as in the conventional example described with reference to FIG. 18 described above, when the lens unit is arranged concentrically with only two components, the far lens unit 901 and the near lens unit 902, the focus formed by the near lens unit 902. The blurred image 908 has an annular shape (see FIG. 18A), and the blurred image 912 formed by the far lens portion 901 has a circular shape (see FIG. 18B), and FIG. ) And FIG. 18B project out-of-focus images having completely different shapes. On the other hand, in the first embodiment, as shown in FIG. 2, the near lens portion 23 and the far lens portion 22 are alternately arranged concentrically around the circular lens portion 22A. Thus, the defocused image 50 formed by the near lens unit 23 becomes a plurality of concentric rings (see FIG. 4A), and the defocused image formed by the far lens unit 22 is blurred. The image 60 has a circular shape and an annular shape arranged concentrically (see FIG. 4B), and a plurality of out-of-focus images are projected concentrically.

  Further, when comparing the multifocal lens 21 of the first embodiment shown in FIG. 2 and the multifocal lens 221 of the second embodiment shown in FIG. 5, the far lens portions arranged alternately and concentrically, By increasing the number (repetition number) of the near lens part, a plurality of circularly focused images formed by the near lens part and a plurality of circular and annular focus images formed by the far lens part are obtained. It can be seen that all the blurred images are more similar to a single circular blurred image. That is, when photographing is performed using the multifocal lens 21 of the first embodiment or the multifocal lens 221 of the second embodiment, a lens portion having a short focal length is formed when a subject at a long distance is photographed. The out-of-focus image component and the out-of-focus image component formed by the lens unit having a long focal length when a subject at a short distance is photographed are similarly similar to each other on the image sensor 24. In this case, a blurred image having the same shape is projected in any shooting state.

  That is, with respect to the multifocal lens 21 of the first embodiment shown in FIG. 2 and the multifocal lens 221 of the second embodiment shown in FIG. By the point spread function (PSF) by the near lens units 23 and 223 configured by the lens unit, and by the far lens units 22 and 222 configured by the plurality of first lens units in the case of photographing a subject at a short distance. The PSF is approximate, and by increasing the number of annular lens portions, these PSFs become more approximate. Therefore, when the PSFs of the lens units constituting the multifocal lens are approximated in this way, one representative PSF matrix W is determined, and the convolution calculation matrix Q is determined using the representative PSF matrix W. Thus, processing by the reproduction calculation means 33 (see FIG. 1) can be performed.

  FIG. 7 shows the conventional multifocal lens 900 shown in FIG. 18, the multifocal lens 21 of the first embodiment shown in FIG. 2, and the multifocal lens of the second embodiment shown in FIG. By comparing the state of blur (light quantity distribution) with the focal lens 221, and increasing the number of annular lens portions, the blur is uniformed (or the unevenness of the light quantity distribution indicating blur is reduced, You can think of it as a gentle distribution.) The vertical axis indicates the amount of light.

  In the light quantity distribution in the case of the conventional multifocal lens 900, the light quantity of the point-like images 907 and 911 in focus protrudes at the center position, and an annular image in which the near lens unit 902 is blurred around the light quantity distribution. The light amount 908 or the light amount of the circular image 912 that is out of focus by the far lens unit 901 is distributed. In the light quantity distribution in the case of the multifocal lens 21 of the first embodiment, the light quantity of the point-like images 51 and 61 in focus protrudes at the center position, and the near lens unit 23 is formed around the light quantity distribution. The light amounts of the annular images 52 and 53 by the annular lens portions 23A and 23B, or the light amounts of the circular image 62 and the annular image 63 by the circular lens portion 22A and the annular lens portion 22B constituting the far lens portion 22 are distributed. It is in a state. Further, in the light amount distribution in the case of the multifocal lens 221 of the second embodiment, the light amount of the focused point-like images 251 and 261 protrudes at the center position, and the near lens unit 223 is formed in the periphery thereof. The light amounts of the annular images 252, 253, 254, and 255 by the annular lens portions 223 A, 223 B, 223 C, and 223 D, or the circular images by the circular lens portions 222 A and the annular lens portions 222 B, 222 C, and 222 D that form the far lens portion 222. The amount of light of the H.262 and annular images 263, 264, 265 is distributed. As a result, the light amount distribution in the case of the multifocal lens 21 of the first embodiment and the case of the multifocal lens 221 of the second embodiment is smaller than that of the conventional multifocal lens 900. It can be seen that the amount of light is made uniform (or the change in the amount of light on the plane is smooth) and the value is small, and that the number of annular lens parts can be increased to make the amount more uniform. Recognize.

  According to such 2nd Embodiment, there exist the following effects. That is, when a normal subject and a close subject at a standard distance are photographed using the multifocal lens 221, the state of defocusing is strictly in accordance with the photographing state as shown in FIG. In other words, in the multifocal lens 221, the first and second lens portions are concentrically repeated a plurality of times, that is, alternately arranged, so that the subject is changed. Regardless of the distance up to, the out-of-focus state is almost the same.

  Therefore, even if the distance to the subject to be photographed changes, image modification processing for removing blur is realized by processing using the same data, that is, each element Q (x, y) of the convolution calculation matrix Q It is possible to perform image modification processing with the same value set to. For this reason, the installation of the switching circuit for automatically identifying the photographing state can be omitted, and it is not necessary to perform switching by manual operation, so that the burden on the user can be reduced.

[Third Embodiment]
FIG. 8 shows a detailed configuration of the multifocal lens 321 according to the third embodiment of the present invention. FIG. 9 is an explanatory diagram of a photographing state by the multifocal lens 321, and FIG. 10 is an explanatory diagram of a state in which light is refracted by the multifocal lens 321. The multifocal lens 321 is a lens used by being incorporated in an imaging system similar to the imaging system 10 (see FIG. 1) of the first embodiment, and the configuration of the multifocal lens is the first in the imaging system as a whole. Unlike the first embodiment, other configurations and functions are the same as those of the first embodiment. Therefore, the same portions are denoted by the same reference numerals, and detailed description thereof will be omitted. The following description will focus on the different portions.

  8 and 9, the multifocal lens 321 is a bifocal lens and is a subject at a relatively long distance (in this embodiment, as an example, a standard from the near point of the depth of field to infinity). A far lens unit 322 having a long focal length for photographing a normal subject at a short distance) and a subject at a relatively short distance (in the present embodiment, as an example, a distance larger than a standard distance). A near lens unit 323 having a short focal length for photographing a close object at a short distance.

  As shown in FIG. 9, the multifocal lens 321 is configured by combining a main lens 324 provided on the subject side and an auxiliary lens 328 provided on the imaging element 24 side. Among these, as shown in FIG. 8, the main lens 324 has a cross-sectional shape as if it is a Fresnel lens, and has a flat base 325 and a plurality of surfaces provided on the surface side (subject side) of the base 325. The close-up lens cutting pieces 326A, 326B, 326C, and 326D are integrally formed. The auxiliary lens 328 is a convex lens, and is arranged at a certain distance from the main lens 324. Note that the auxiliary lens 328 may be disposed at a position closer to the subject than the main lens 324.

  As shown in FIG. 8, the close-up lens cutting pieces 326A, 326B, 326C, and 326D have an annular (annular shape in this embodiment) planar shape (front shape), and are arranged concentrically. Yes. These close-up lens cut-out pieces 326A, 326B, 326C, and 326D are closer than a standard distance from a near point (for example, about 0.3 m) of the depth of field to infinity (for example, less than 10 cm). Etc.) as a constituent element of a lens unit for photographing a close subject (for example, a barcode, an iris, a character, etc.) in a close-up photographing lens 326 that is one convex lens having one focal length. It has been done. That is, the close-up lens cutting pieces 326A, 326B, 326C, and 326D partition the close-up lens 326 indicated by the dotted line in FIG. 8 at a predetermined interval d by a plane orthogonal to the optical axis thereof. A ring pitch is determined by a position P at which the surface of the close-up photographing lens 326 and each surface of a predetermined distance d intersect, and the close-up photographing lens 326 is concentrically arranged at the pitch (in this embodiment, a cylinder). Then, every other portion having a substantially triangular cross section including the surface of the close-up lens 326 is cut out and formed. The close-up photographing lens 326 may be a spherical lens or an aspherical lens.

  Further, the material of the close-up lens cutting pieces 326A, 326B, 326C, and 326D constituting the main lens 324 (that is, the material of the close-up lens 326) is the same as the material of the base 325 that also forms the main lens 324. For example, it is glass etc., and the refractive index n is about n = 1.5-1.8, for example.

  Furthermore, the planar shape (frontal shape) of the base 325 is circular in this embodiment, and the close-up lens cutting pieces 326A, 326B, 326C, and 326D are included in the surface of the base 325 (the subject side surface). The portions not arranged are a circular flat surface portion 325A and an annular flat surface portion 325B, 325C, 325D, 325E.

  A plurality of first lens portions are formed by a circular flat surface portion 325A and an annular flat surface portion 325B, 325C, 325D, 325E of the base 325. On the other hand, a plurality of second lenses are formed by the close-up lens cutting pieces 326A, 326B, 326C, and 326D and the portion of the base 325 where the close-up lens cutting pieces 326A, 326B, 326C, and 326D are arranged. The part is formed. Therefore, the first lens portion and the second lens portion are alternately arranged concentrically with the first lens portion as the center.

  Further, as shown in FIG. 9, light from infinity (that is, standard light) is obtained by the flat surface portions 325A, 325B, 325C, 325D, and 325E of the base 325 as the first lens portion and the auxiliary lens 328. Since the light from a single bright spot on a normal subject at a distance forms an image on the image sensor 24, a combination of these forms the far lens unit 322 (the optical path indicated by the solid line in FIG. 9). reference). On the other hand, the close-up lens cutout pieces 326A, 326B, 326C, and 326D as the second lens portion, the base 325 on which these are arranged, and the auxiliary lens 328 constitute the near-lens portion 323 (FIG. 9). (See the light path indicated by the dotted line in the middle.)

  In the third embodiment, photographing using diffracted light is performed by the multifocal lens 321 as follows.

  In FIG. 10, for example, if the light wavefronts W1 to W8 are incident in this order on the close-up lens cutout pieces 326A, 326B, 326C, and 326D of the main lens 324 constituting the multifocal lens 321, the optical path L1. As in L6, the light is refracted by the close-up lens cutting pieces 326A, 326B, 326C, and 326D. At this time, among the close-up lens cutting pieces 326A, 326B, 326C, and 326D, the close-up lens cutting pieces arranged adjacent to each other (in the example of FIG. 10, the close-up lens cutting pieces 326A, 326B), when the light is incident, the wavefront is shifted by two, for example, a wavefront W3 that has passed through the close-up lens cutting piece 326A and a wavefront W1 that has passed through the close-up lens cutout piece 326B. To match. That is, the image is formed by the second-order diffracted light by matching the phases by shifting by two wavelengths. Accordingly, a diffractive lens is formed by the close-up lens cutting pieces 326A, 326B, 326C, 326D and the base 325 integrated therewith.

  Here, the maximum dimension in the thickness direction of the close-up lens cutting pieces 326A, 326B, 326C, and 326D forming the diffractive lens (that is, the maximum dimension in the thickness direction of the step portion of the diffractive lens) is as described above. The distance d of the partition at the time of cutting out from the lens 326 is the distance d in the third embodiment, and the light passing through the close-up lens cutting pieces 326A, 326B, 326C, 326D and air The light passing therethrough is of a size that is shifted by one wavelength.

  That is, if the wavelength of light passing through the air is λ and the refractive index of the material of the close-up lens cutting pieces 326A, 326B, 326C, and 326D (for example, glass) is n, the close-up lens cutting out The wavelength of light passing through the pieces 326A, 326B, 326C, and 326D is λ / n, which is shortened. At this time, the distance required for the light passing through the close-up lens cutting pieces 326A, 326B, 326C, and 326D and the light passing through the air to be shifted by one wavelength is d, and the distance d If the wave number in the close-up lens cutout pieces 326A, 326B, 326C, 326D is m, the wave number in the air at the distance d may be m-1, so the following equations (3) and (3) (4) is established. Solving these equations (3) and (4) to eliminate m yields the following equation (5).

  m = d / (λ / n) (3)

  m-1 = d / λ (4)

  d = λ / (n−1) (5)

  Here, for example, if n = 1.5, d = 2λ, which is the example shown in FIG. In this example, the wave number in the air is 2 with respect to the distance d, and the wave numbers in the close-up lens cutting pieces 326A, 326B, 326C, and 326D are 3, so the phase is shifted by one wavelength. Will match. Accordingly, as shown by the two-dot chain line in FIG. 10, the close-up lens cutout piece having the same focal length between the close-up lens cutout pieces 326A and 326B (cut out from the close-up lens 326). Are adjacent to each other without a gap, for example, the wavefront shifts by one, for example, the wavefront W1 that has passed through the close-up lens cutout piece 326B and the close-up lens cutout drawn by a two-dot chain line. The wavefront W2 (inside the parentheses in FIG. 10) assumed to have passed through the protruding piece coincides. In the third embodiment, since every other close-up lens cutout piece is arranged, the wavefronts that have passed through the adjacent close-up lens cutout pieces 326A and 326B are shifted by two, For example, the wavefront W1 that has passed through the close-up lens cutout piece 326B and the wavefront W3 that has passed through the close-up lens cutout piece 326A coincide.

  For example, when n = 1.6, d = 1.67λ, when n = 1.8, d = 1.25λ, and when n = 2, d = λ. Further, in the third embodiment, the interval d at the time of cutting from the above-mentioned close-up lens 326 is set to the light passing through the close-up lens cutout pieces 326A, 326B, 326C, 326D, The light passing through the air is dimensioned to be deviated by one wavelength, but since the close-up photographing lens cut-out pieces are arranged every other piece, the interval d of the partition at the time of cutting is dimensioned to be deviated by half wavelength. In this case, the light that has passed through the adjacent cut-out pieces of the close-up photographing lens cut-out pieces arranged every other one is shifted by one wavelength, and image formation by the first-order diffracted light is realized.

  According to such 3rd Embodiment, there exist the following effects. That is, as in the first and second embodiments, in the multifocal lens 321, the first and second lens portions are concentrically repeated a plurality of times, that is, alternately arranged, so Regardless of the distance, the out-of-focus state is almost the same. Therefore, even if the distance to the subject to be photographed changes, image modification processing for removing blur is realized by processing using the same data, that is, each element Q (x, y) of the convolution calculation matrix Q It is possible to perform image modification processing with the same value set to. For this reason, the installation of the switching circuit for automatically identifying the photographing state can be omitted, and it is not necessary to perform switching by manual operation, so that the burden on the user can be reduced.

  A close-up lens cutout piece 326A, 326B, 326C, 326D and a base plate 325 integrated therewith form a diffractive lens, which has a cross-sectional shape similar to or close to that of a Fresnel lens. Therefore, the main lens 324 can be thinned as a whole, the weight can be reduced, the degree of freedom in design can be improved, and the manufacturing can be facilitated and the manufacturing cost can be reduced. .

[Fourth Embodiment]
FIG. 11 shows a detailed configuration of the multifocal lens 421 according to the fourth embodiment of the present invention. FIG. 12 is an explanatory diagram of a photographing state by the multifocal lens 421, and FIG. 13 is an explanatory diagram of a manufacturing method of the multifocal lens 421. The multifocal lens 421 is a lens used by being incorporated in an imaging system similar to the imaging system 10 (see FIG. 1) of the first embodiment, and the configuration of the multifocal lens is the first in the imaging system as a whole. Unlike the first embodiment, other configurations and functions are the same as those of the first embodiment. Therefore, the same portions are denoted by the same reference numerals, and detailed description thereof will be omitted. The following description will focus on the different portions.

  11 and 12, a multifocal lens 421 is a bifocal lens and is a subject at a relatively long distance (in this embodiment, as an example, a standard from a near point of the depth of field to infinity). A far lens unit 422 having a long focal length for photographing a normal subject at a short distance) and a subject at a relatively short distance (in the present embodiment, as an example, a distance larger than a standard distance). A near lens unit 423 having a short focal length for photographing a close subject at a short distance.

  As shown in FIG. 11, the multifocal lens 421 has a cross-sectional shape like a Fresnel lens, and has a flat base 425 and a plurality of close-up photographs provided on the surface side (subject side) of the base 425. Lens cut-out pieces 426A, 426B, 426C, 426D, and 426E and a plurality of standard photographing lens cut-out pieces 427A, 427B, 427C, and 427D are integrally configured. In the fourth embodiment, the auxiliary lens as in the third embodiment is not provided, but an auxiliary lens may be provided.

  As shown in FIG. 11, the close-up lens cutting piece 426A has a circular planar shape (front shape), and the close-up lens cutting pieces 426B, 426C, 426D, and 426E are annular (this embodiment). In this case, it has an annular shape), and these are arranged concentrically. These close-up lens cutting pieces 426A, 426B, 426C, 426D, and 426E are close objects (for example, barcodes, irises, characters, etc.) that are closer than a standard distance (for example, less than 10 cm). Is formed by cutting out from a close-up photographing lens 426 which is one convex lens having one focal length. The close-up photographing lens 426 may be a spherical lens or an aspherical lens.

  In addition, as shown in FIG. 11, the standard photographing lens cutout pieces 427A, 427B, 427C, and 427D have an annular (annular in this embodiment) planar shape, and these are arranged concentrically. Yes. These standard photographing lens cut-out pieces 427A, 427B, 427C, and 427D are normal subjects (for example, landscapes) at a standard distance from a near point (for example, about 0.3 m) of the depth of field to infinity. As a component of a lens unit for photographing a person or the like), it is cut out from a standard photographing lens 427 that is one convex lens having one focal length. The standard photographing lens 427 is a lens having a smaller curvature and a longer focal length than the close-up photographing lens 426. The standard photographing lens 427 may be a spherical lens or an aspherical lens.

  The material of the close-up lens cutting pieces 426A, 426B, 426C, 426D, and 426E (that is, the material of the close-up lens 426) and the material of the standard shooting lens cut-out pieces 427A, 427B, 427C, and 427D (that is, the standard) The material of the photographing lens 427 is the same as the material of the base 425, for example, glass or the like, and the refractive index n is, for example, about n = 1.5 to 1.8.

  A plurality of close-up lens cutout pieces 426A, 426B, 426C, 426D, and 426E and a portion of the base 425 in which the close-up shot lens cutout pieces 426A, 426B, 426C, 426D, and 426E are arranged. A first lens portion is formed. On the other hand, a plurality of second lenses are formed by the standard photographing lens cutout pieces 427A, 427B, 427C, and 427D and the portion of the base 425 where the standard photography lens cutout pieces 427A, 427B, 427C, and 427D are disposed. The part is formed. Therefore, the first lens portion and the second lens portion are alternately arranged concentrically with the first lens portion as the center.

  In addition, as shown in FIG. 12, light from infinity (that is, light from a single bright spot on a normal subject at a standard distance) is extracted as a standard photographing lens as the second lens unit. Since the image is formed on the image pickup device 24 through the pieces 427A, 427B, 427C, 427D and the base plate 425 on which these pieces are arranged, the far lens unit 422 is configured by these (shown by the solid line in FIG. 12). See light path). On the other hand, a close-up lens cutout piece 426A, 426B, 426C, 426D, and 426E as the first lens portion and a base plate 425 on which these are arranged constitute a near lens portion 423 (indicated by a dotted line in FIG. 12). See the light path shown).

  In the fourth embodiment, the multifocal lens 421 is manufactured as follows.

  In FIG. 13, first, the close-up lens 426 is partitioned at a predetermined distance d by a surface K1 orthogonal to the optical axis, and the surface of the close-up lens 426 and each surface K1 at a predetermined distance d intersect. The ring pitch is determined by P, and the close-up lens 426 is partitioned at the pitch by a plurality of concentric tubes (cylinders in the present embodiment) K2, and then has a substantially triangular cross section including the surface of the close-up lens 426. By cutting out every other portion, close-up lens cutting pieces 426A, 426B, 426C, 426D, and 426E are formed.

  Next, the standard photographing lens 427 is partitioned at a predetermined interval d by a surface K3 orthogonal to the optical axis thereof, and a plurality of tubes (this embodiment) having the same size as the plurality of tubes K2 partitioning the close-up photographing lens 426. In the embodiment, after the standard photographing lens 427 is partitioned by the cylinder) K4, that is, at the same pitch as that obtained by partitioning the close-up photographing lens 426, the surface of the standard photographing lens 427 among the surfaces K3 orthogonal to the optical axis The standard photographing lens 427 is cut on the non-intersecting surface, and every other part having a substantially trapezoidal cross section including the surface of the standard photographing lens 427 is cut out, so that the standard photographing lens cut-out pieces 427A, 427B, and 427C are obtained. , 427D. When the standard photographing lens 427 is partitioned by a plurality of tubes, unlike the close-up photographing lens 426, the position G intersects the surface of the standard photographing lens 427 and each surface K3 with a predetermined distance d. Since the ring pitch is not determined, but is divided by the same pitch as that obtained by dividing the close-up photographing lens 426, the cross-sectional shapes of the standard photographing lens cut-out pieces 427A, 427B, 427C, and 427D are not substantially triangular. Although it has a substantially trapezoidal shape, the ring pitch may be based on the standard photographing lens 427 instead of the ring pitch based on the close-up photographing lens 426 as described above. That is, the ring pitch is determined by the position G where the surface of the standard photographing lens 427 and each surface K3 with a predetermined interval d intersect, and the standard photographing lens 427 is concentrically arranged at the pitch (this embodiment). Then, after partitioning by the cylinder (K5) (see the alternate long and short dash line in FIG. 13), every other portion having a substantially triangular cross section including the surface of the standard photographing lens 427 is cut out, while the close-up photographing lens 426 is partitioned. May be partitioned at the same pitch as the partitioning of the standard photographing lens 427.

  The partition distance d described above is the same as in the case of the third embodiment, and the close-up lens cutting pieces 426A, 426B, 426C, 426D, and 426E and the standard shooting lens cut-out pieces 427A and 427B. , 427C, 427D and the light passing through the air are dimensioned to be shifted by one wavelength. Thereby, as in the case of the third embodiment, the light passing through the close-up lens cutout pieces arranged adjacent to each other among the close-up lens cutout pieces 426A, 426B, 426C, 426D, and 426E. The phases are matched by shifting by two wavelengths, thereby realizing imaging by the second-order diffracted light. Accordingly, a diffractive lens is formed by the close-up lens cutting pieces 426A, 426B, 426C, 426D, and 426E and the base 425 integrated with them. Further, the light passing through the standard photographing lens cutouts arranged adjacent to each other among the standard photographing lens cutouts 427A, 427B, 427C, and 427D is also shifted in phase by two wavelengths, thereby matching the phase. Imaging with the second-order diffracted light is realized. Therefore, a diffractive lens is formed by the standard photographing lens cut-out pieces 427A, 427B, 427C, 427D and the base 425 integrated therewith.

  However, the maximum dimension in the thickness direction of the close-up lens cutting pieces 426A, 426B, 426C, 426D, and 426E (that is, the step portion of the diffractive lens) is determined by the partition at the time of cutting out from the close-up lens 426 described above. While the distance d, that is, the light passing through the close-up lens cutting pieces 426A, 426B, 426C, 426D, and 426E and the light passing through the air are dimensioned to be shifted by one wavelength, The maximum dimension in the thickness direction of the standard photographing lens cut-out pieces 427A, 427B, 427C, and 427D (that is, the step portion of another diffractive lens) corresponds to the position (light) of the close-up photographing lens 426 and the standard photographing lens 427. Strictly speaking, it is not a dimension that is divided by one wavelength, that is, the interval d of the partitions. Further, as described above, a ring pitch based on the standard photographing lens 427 may be used. In this case, the maximum dimension in the thickness direction of the standard photographing lens cut-out piece is the partition interval d, that is, one wavelength. On the other hand, the maximum dimension in the thickness direction of the close-up lens cutting piece is not a dimension that is divided by one interval, that is, one wavelength. Therefore, the maximum dimension in the thickness direction of the cut-out piece of any one of the lenses that is used as a reference only needs to be the partition distance d.

  In the fourth embodiment, as described above, the interval d between the partitions is the light passing through the close-up lens cutting piece and the standard shooting lens cut-out piece, and the light passing through the air. However, in the fourth embodiment, since the close-up photographing lens cut pieces and the standard photographing lens cut pieces are arranged every other piece, the interval d between the partitions is set as follows. In this case, the light that has passed through the adjacent cut-out pieces of the close-up photographing lenses or the standard photographing lens cut-out pieces arranged every other wavelength is one wavelength. Deviation and image formation by the first-order diffracted light are realized.

  According to such 4th Embodiment, there exist the following effects. That is, as in the first to third embodiments, in the multifocal lens 421, the first and second lens portions are concentrically repeated a plurality of times, that is, alternately arranged, so Regardless of the distance, the out-of-focus state is almost the same. Therefore, even if the distance to the subject to be photographed changes, image modification processing for removing blur is realized by processing using the same data, that is, each element Q (x, y) of the convolution calculation matrix Q It is possible to perform image modification processing with the same value set to. For this reason, the installation of the switching circuit for automatically identifying the photographing state can be omitted, and it is not necessary to perform switching by manual operation, so that the burden on the user can be reduced.

  The close-up lens cutting pieces 426A, 426B, 426C, 426D, and 426E and the base 425 integrated therewith, and the standard shooting lens cut-out pieces 427A, 427B, 427C, and 427D and these are integrated. A diffraction lens is formed by each of the bases 425, and has a cross-sectional shape like a Fresnel lens or a cross-sectional shape close to this, so that the multifocal lens 421 can be thinned as a whole, and weight reduction can be achieved. In addition, the degree of freedom in design can be improved, and the manufacturing can be facilitated and the manufacturing cost can be reduced.

[Fifth Embodiment]
FIG. 14 shows a detailed configuration of the multifocal lens 521 according to the fifth embodiment of the present invention. FIG. 15 is an explanatory diagram of a shooting state by the multifocal lens 521. The multifocal lens 521 is a lens used by being incorporated in an imaging system similar to the imaging system 10 (see FIG. 1) of the first embodiment, and the configuration of the multifocal lens is the first in the imaging system as a whole. Unlike the first embodiment, other configurations and functions are the same as those of the first embodiment. Therefore, the same portions are denoted by the same reference numerals, and detailed description thereof will be omitted. The following description will focus on the different portions.

  14 and 15, a multifocal lens 521 is a bifocal lens, and is a subject at a relatively long distance (in this embodiment, as an example, a standard from the near point of the depth of field to infinity). A far lens unit 522 having a long focal length for photographing a normal subject at a short distance, and a subject at a relatively short distance (in this embodiment, as an example, more than a standard distance). A near lens unit 523 having a short focal length for photographing a close object at a short distance.

  The multifocal lens 521 is configured by combining a main lens 524 provided on the subject side and an auxiliary lens 528 provided on the image sensor 24 side. Among these, as shown in FIG. 14, the main lens 524 has a cross-sectional shape as if it is a Fresnel lens, and has a flat base 525 and a plurality of surfaces provided on the surface side (subject side) of the base 525. The standard photographing lens cut-out pieces 526A, 526B, 526C, 526D, and 526E and a plurality of close-up photographing lens cut-out pieces 527A, 527B, 527C, and 527D are integrally configured. The auxiliary lens 528 is a convex lens, and is arranged at a certain distance from the main lens 524. Note that the auxiliary lens 528 may be disposed at a position closer to the subject than the main lens 524.

  As shown in FIG. 14, the standard photographing lens cut-out piece 526A has a circular plane shape (front shape), and the standard photographing lens cut-out pieces 526B, 526C, 526D, and 526E are annular (this embodiment). In this case, it has an annular shape), and these are arranged concentrically. These standard photographing lens cutouts 526A, 526B, 526C, 526D, and 526E are normal subjects (for example, at a standard distance from a near point (for example, about 0.3 m) of the depth of field to infinity. As a constituent element of a lens unit for photographing a landscape, a person, etc.), it is cut out from a standard photographing lens 526 which is one concave lens having one focal length. The standard photographing lens 526 may be a spherical lens or an aspherical lens.

  Further, as shown in FIG. 14, the close-up lens cutting pieces 527A, 527B, 527C, and 527D have an annular (annular in this embodiment) planar shape, and are arranged concentrically. Yes. These close-up lens cut-out pieces 527A, 527B, 527C, and 527D photograph close-up subjects (for example, barcodes, irises, and characters) that are closer than a standard distance (for example, less than 10 cm). As a component of the lens unit for this purpose, the lens unit is cut out from the close-up lens 527 which is one convex lens having one focal length. The close-up lens 527 has the same curvature (absolute value) at the corresponding position (position equidistant from the optical axis) as the standard imaging lens 526. The close-up lens 527 may be a spherical lens or an aspheric lens.

  Standard shooting lens cutouts 526A, 526B, 526C, 526D, and 526E (ie, standard shooting lens 526 material) and proximity shooting lens cutouts 527A, 527B, 527C, and 527D (ie, proximity) The material of the photographing lens 527 is the same as the material of the base 525, for example, glass or the like, and the refractive index n is, for example, about n = 1.5 to 1.8.

  A plurality of standard photographing lens cutouts 526A, 526B, 526C, 526D, and 526E and a portion of the base 525 in which the standard photographing lens cutouts 526A, 526B, 526C, 526D, and 526E are arranged. A first lens portion is formed. On the other hand, a plurality of second lenses are formed by the close-up lens cutting pieces 527A, 527B, 527C, and 527D and the portion of the base 525 where the close-up lens cutting pieces 527A, 527B, 527C, and 527D are disposed. The part is formed. Therefore, the first lens portion and the second lens portion are alternately arranged concentrically with the first lens portion as the center.

  Further, as shown in FIG. 15, the standard photographing lens cut-out pieces 526A, 526B, 526C, 526D, and 526E as the first lens portion, and the base 525 on which these are arranged, and the auxiliary lens 528, are infinitely far away. Since the light from the lens (that is, the light from a single bright spot on a normal subject at a standard distance) forms an image on the image sensor 24, a combination of these forms the far lens unit 522 (see FIG. 15 (see the optical path indicated by the solid line). On the other hand, the close-up lens cutout pieces 527A, 527B, 527C, and 527D as the second lens portion, the base 525 on which these are arranged, and the auxiliary lens 528 constitute the near-lens portion 523 (FIG. 15). (See the light path indicated by the dotted line in the middle.)

  In the fifth embodiment, the multifocal lens 521 is manufactured as follows.

  In FIG. 14, the standard photographing lens 526 is partitioned at a predetermined interval d by a surface orthogonal to the optical axis, and the ring pitch is set according to the position where the surface of the standard photographing lens 526 intersects each surface of the predetermined interval d. After determining and dividing the standard photographing lens 526 by a plurality of concentric tubes (cylindrical in this embodiment) at that pitch, every other portion of the substantially triangular section including the surface of the standard photographing lens 526 is placed. By cutting out, the standard photographing lens cutout pieces 526A, 526B, 526C, 526D, and 526E are formed. Similarly, close-up lens cutting pieces 527A, 527B, 527C, and 527D are cut out from the close-up lens 527 and formed.

  At this time, since the magnitudes (absolute values) of curvature at the corresponding positions (positions equidistant from the optical axis) of the standard photographing lens 526 and the close-up photographing lens 527 are the same, they are formed by a plurality of tubes. The pitch when partitioning is the same. Along with this, the maximum dimension in the thickness direction of the standard photographing lens cut-out pieces 526A, 526B, 526C, 526D, and 526E (which will be a stepped portion of the diffraction lens as described below) and the close-up photographing. The maximum dimension in the thickness direction of each of the lens cut pieces 527A, 527B, 527C, and 527D (which will be a step portion of another diffractive lens as described below) is the interval d of the partitions and coincides.

  The partition interval d described above is the same as that in the third and fourth embodiments. The standard photographing lens cut-out pieces 526A, 526B, 526C, 526D, and 526E and the close-up photographing lens cut-out pieces are used. The light that passes through 527A, 527B, 527C, and 527D and the light that passes through the air have dimensions that are shifted by one wavelength. As a result, as in the third and fourth embodiments, the standard photographing lens cutout pieces 526A, 526B, 526C, 526D, and 526E pass through the standard photographing lens cutout pieces adjacent to each other. The light to be shifted is shifted in phase by two wavelengths so that the image is formed by the second-order diffracted light. Therefore, a diffractive lens is formed by the standard photographing lens cutout pieces 526A, 526B, 526C, 526D, and 526E and the base 525 integrated therewith. Furthermore, the light passing through the close-up lens cutout pieces arranged adjacent to each other among the close-up lens cutout pieces 527A, 527B, 527C, and 527D is also shifted in phase by two wavelengths, thereby matching the phase. Imaging with the second-order diffracted light is realized. Accordingly, a diffractive lens is formed by the close-up lens cutting pieces 527A, 527B, 527C, and 527D and the base 525 integrated therewith. In the fifth embodiment, as described above, the interval d between the partitions is the light passing through the standard shooting lens cutout piece and the close-up shooting lens cutout piece and the light passing through the air. However, in this fifth embodiment, the standard photographing lens cut-out pieces and the close-up photographing lens cut-out pieces are arranged every other piece, so that the interval d between the partitions is In this case, the light that has passed through the adjacent cut-out pieces of the standard shooting lens cut-out pieces and the close-up shot lens cut-out pieces arranged at every other wavelength is one wavelength. Deviation and image formation by the first-order diffracted light are realized.

  According to such 5th Embodiment, there exist the following effects. That is, as in the case of the first to fourth embodiments, in the multifocal lens 521, the first and second lens portions are concentrically repeated a plurality of times, that is, alternately arranged. Regardless of the distance, the out-of-focus state is almost the same. Therefore, even if the distance to the subject to be photographed changes, image modification processing for removing blur is realized by processing using the same data, that is, each element Q (x, y) of the convolution calculation matrix Q It is possible to perform image modification processing with the same value set to. For this reason, the installation of the switching circuit for automatically identifying the photographing state can be omitted, and it is not necessary to perform switching by manual operation, so that the burden on the user can be reduced.

  Further, the standard photographing lens cut-out pieces 526A, 526B, 526C, 526D, and 526E and the base plate 525 integrated therewith, and the close-up shooting lens cut-out pieces 527A, 527B, 527C, and 527D and these integrated therewith. Each of the bases 525 forms a diffractive lens and has a cross-sectional shape similar to that of a Fresnel lens or a cross-sectional shape close thereto, so that the main lens 524 can be thinned as a whole, and the weight can be reduced. In addition, the degree of freedom in design can be improved, and the manufacturing can be facilitated and the manufacturing cost can be reduced.

  Further, since the standard photographing lens 526 and the close-up photographing lens 527 have the same curvature (absolute value) at corresponding positions (positions equidistant from the optical axis), the standard photographing lens cut-out piece is used. 526A, 526B, 526C, 526D, 526E (that is, the step portion of the diffractive lens) in the thickness direction, and the close-up lens cutting pieces 527A, 527B, 527C, 527D (that is, the step portion of another diffractive lens). ) In the thickness direction can be matched. Since the surface parallel to the optical axis for the standard photographing lens cutout and the surface parallel to the optical axis for the close-up photographing lens cutout are arranged facing each other, the lens surface is unnecessary. Surfaces, that is, surfaces that do not contribute to image formation can be eliminated.

[Sixth Embodiment]
FIG. 16 shows a detailed configuration of the multifocal lens 621 according to the sixth embodiment of the present invention. FIG. 17 is an explanatory diagram of a shooting state by the multifocal lens 621. The multifocal lens 621 is a lens that is used by being incorporated in an imaging system similar to the imaging system 10 (see FIG. 1) of the first embodiment. For the entire imaging system, the configuration of the multifocal lens is the first one. Unlike the first embodiment, other configurations and functions are the same as those of the first embodiment. Therefore, the same portions are denoted by the same reference numerals, and detailed description thereof will be omitted. The following description will focus on the different portions.

  16 and 17, the multifocal lens 621 is a trifocal lens, and is an object at a relatively long distance (in this embodiment, as an example, a normal distance at a standard distance from about 1 m to infinity). A far lens unit 622 having a long focal length for photographing a subject, and a subject at a relatively intermediate distance (in this embodiment, a subject at a distance of about 50 cm is taken as an example). And an intermediate lens unit 629 having an intermediate focal length for shooting a subject and a subject at a relatively short distance (in this embodiment, a close subject at a distance of about 7 cm is taken as an example). And a near lens unit 623 having a short focal length.

  The multifocal lens 621 is configured by combining a main lens 624 provided on the subject side and an auxiliary lens 628 provided on the image sensor 24 side. Among these, as shown in FIG. 16, the main lens 624 has a cross-sectional shape as if it is a Fresnel lens, and has a flat base 625 and a plurality of bases 625 provided on the surface side (subject side). The standard photographing lens cut-out pieces 626A, 626B, and 626C and the plurality of close-up photographing lens cut-out pieces 627A, 627B, and 627C are integrated with each other. The auxiliary lens 628 is a convex lens, and is arranged at a certain distance from the main lens 624. Note that the auxiliary lens 628 may be disposed at a position closer to the subject than the main lens 624.

  As shown in FIG. 16, the standard photographing lens cut-out piece 626A has a circular plane shape (front shape), and the standard photographing lens cut-out pieces 626B and 626C are annular (in the present embodiment, annular). ) And are arranged concentrically. These standard photographing lens cutouts 626A, 626B, and 626C are configured as a lens unit for photographing a normal subject (for example, a landscape or a person) at a standard distance from about 1 m to infinity, for example. As an element, it is formed by cutting out from a standard photographing lens 626 that is one concave lens having one focal length. The standard photographing lens 626 may be a spherical lens or an aspherical lens.

  Further, as shown in FIG. 16, the close-up lens cutting pieces 627A, 627B, and 627C have an annular (annular in this embodiment) planar shape, and are arranged concentrically. These close-up photographing lens cut-out pieces 627A, 627B, and 627C are provided as one component of a lens unit for photographing a close subject (for example, a barcode, an iris, or a character) at a distance of about 7 cm, for example. The lens is cut out from the close-up lens 627, which is one convex lens having a focal length. The close-up lens 627 has the same curvature (absolute value) at the corresponding position (position equidistant from the optical axis) as the standard shooting lens 626. The close-up lens 627 may be a spherical lens or an aspheric lens.

  The material of the standard photographing lens cutouts 626A, 626B, and 626C (that is, the material of the standard photographing lens 626) and the material of the close-up lens cutting pieces 627A, 627B, and 627C (that is, the material of the close-up photographing lens 627) ) Is the same as the material of the substrate 625, for example, glass or the like, and the refractive index n is, for example, about n = 1.5 to 1.8.

  Furthermore, the planar shape (frontal shape) of the base 625 is circular in this embodiment, and the standard photographing lens cutouts 626A, 626B, 626C and the close-up photographing are included in the surface of the base 625 (subject side surface). The portions where the lens cutting pieces 627A, 627B, and 627C are not arranged are annular (in the present embodiment, annular) flat surface portions 625A, 625B, and 625C.

  A plurality of first lens portions are formed by the standard photographing lens cutouts 626A, 626B, and 626C and the portion of the base 625 where the standard photographing lens cutouts 626A, 626B, and 626C are disposed. ing. On the other hand, a plurality of second lens portions are formed by the close-up lens cutting pieces 627A, 627B, 627C and the portion of the base 625 where the close-up lens cutting pieces 627A, 627B, 627C are arranged. ing. In addition, a plurality of third lens portions are formed by annular flat surface portions 625A, 625B, and 625C of the base 625. Accordingly, the first to third lens portions are arranged repeatedly concentrically a plurality of times with the first lens portion as the center.

  In addition, as shown in FIG. 17, standard photographing lens cutouts 626 </ b> A, 626 </ b> B, 626 </ b> C serving as the first lens unit, a base plate 625 on which these are arranged, and an auxiliary lens 628 allow light from infinity ( That is, since the light from a single bright spot on a normal subject at a standard distance forms an image on the image sensor 24, the combination of these forms the far lens unit 622 (solid line in FIG. 17). (Refer to the optical path shown in the figure.) On the other hand, a close-up lens cutout piece 627A, 627B, 627C as a second lens portion, a base plate 625 on which these are arranged, and an auxiliary lens 628 constitute a close-up lens portion 623 (in FIG. 17). (See the light path indicated by the dotted line.) Further, the intermediate lens portion 629 is configured by the flat surface portions 625A, 625B, and 625C of the base 625 as the third lens portion and the auxiliary lens 628 (see the optical path indicated by the one-dot chain line in FIG. 17). .

  In the sixth embodiment, the multifocal lens 621 is manufactured as follows.

  In FIG. 16, the standard photographing lens 626 is partitioned by a surface perpendicular to the optical axis at a predetermined interval d, and the ring pitch is set according to the position where the surface of the standard photographing lens 626 intersects each surface of the predetermined interval d. After determining and dividing the standard photographing lens 626 by a plurality of concentric tubes (cylindrical in the present embodiment) at the pitch, every other portion of the substantially triangular section including the surface of the standard photographing lens 626 is placed. By cutting out, standard photographing lens cutout pieces 626A, 626B, and 626C are formed. Similarly, close-up lens cutting pieces 627A, 627B, and 627C are cut out from the close-up lens 627 and formed.

  At this time, since the magnitudes (absolute values) of curvature at the corresponding positions (positions equidistant from the optical axis) of the standard photographing lens 626 and the close-up photographing lens 627 are the same, they are formed by a plurality of cylinders. The pitch when partitioning is the same. Along with this, the maximum dimension in the thickness direction of the standard photographing lens cut-out pieces 626A, 626B, and 626C (which will be a step portion of the diffraction lens as described below), and the close-up photographing lens cut-out piece Each of the maximum dimensions in the thickness direction of 627A, 627B, and 627C (which will be a step portion of another diffractive lens as described below) corresponds to the partition interval d.

  The partition distance d described above is the same as in the case of the third to fifth embodiments. The standard photographing lens cutouts 626A, 626B, 626C and the close-up photographing lens cutouts 627A, 627B, The light passing through 627C and the light passing through the air are of a size that is deviated by one wavelength. Thereby, the light passing through the standard photographing lens cutouts arranged adjacent to each other among the standard photographing lens cutouts 626A, 626B, and 626C is shifted in phase by three wavelengths, and thus the phase is matched. Imaging with the next diffracted light is realized. Therefore, a diffractive lens is formed by the standard photographing lens cut-out pieces 626A, 626B, and 626C and the base 625 integrated therewith. In addition, the light passing through the close-up lens cutting pieces arranged adjacent to each other among the close-up lens cutting pieces 627A, 627B, and 627C is also shifted in phase by three wavelengths, thereby matching the phase. Imaging by folding light is realized. Therefore, a diffractive lens is formed by the close-up lens cutting pieces 627A, 627B, 627C and the base 625 integrated therewith. In the sixth embodiment, as described above, the interval d between the partitions is the light passing through the standard shooting lens cutout piece and the close-up shooting lens cutout piece and the light passing through the air. However, in the sixth embodiment, the standard photographing lens cut-out piece and the close-up photographing lens cut-out piece are arranged at a ratio of one out of two at intervals of two. Since it is arranged, the interval d of the partition may be a size that is divided by 1/3 wavelength or 2/3 wavelength, and in this case, it is arranged at a ratio of 1 to 3 with two intervals. The light that has passed through the adjacent cut-out pieces of the standard photographing lens cut-out piece and the close-up photographing lens cut-out piece forms an image by one wavelength or two wavelength shift, first-order diffracted light, or second-order diffracted light.

  According to the sixth embodiment, there are the following effects. That is, in the multifocal lens 621, the first to third lens portions are repeatedly arranged concentrically a plurality of times, so that the state of defocusing is substantially the same regardless of the distance to the subject. Therefore, even if the distance to the subject to be photographed changes, image modification processing for removing blur is realized by processing using the same data, that is, each element Q (x, y) of the convolution calculation matrix Q It is possible to perform image modification processing with the same value set to. For this reason, the installation of the switching circuit for automatically identifying the photographing state can be omitted, and it is not necessary to perform switching by manual operation, so that the burden on the user can be reduced.

  Further, the standard photographing lens cutouts 626A, 626B, and 626C and the base 625 integrated therewith, and the close-up lens cutting pieces 627A, 627B, 627C and the base 625 integrated therewith are used for diffraction. Since a lens is formed and has a cross-sectional shape similar to or close to that of a Fresnel lens, the main lens 624 can be thinned as a whole, the weight can be reduced, and design freedom can be achieved. The degree of manufacturing can be improved, and the manufacturing can be facilitated and the manufacturing cost can be reduced.

  Further, the standard photographing lens 626 and the close-up photographing lens 627 have the same curvature (absolute value) at the corresponding position (position equidistant from the optical axis). The maximum dimension in the thickness direction of 626A, 626B, and 626C (that is, the step portion of the diffractive lens) and the maximum dimension in the thickness direction of the close-up lens cutting pieces 627A, 627B, and 627C (that is, the step portion of another diffractive lens). The dimensions can be matched. Since the surface parallel to the optical axis for the standard photographing lens cutout and the surface parallel to the optical axis for the close-up photographing lens cutout are arranged facing each other, the lens surface is unnecessary. Surfaces, that is, surfaces that do not contribute to image formation can be eliminated.

  Note that the present invention is not limited to the above-described embodiments, and modifications and the like within a range in which the object of the present invention can be achieved are included in the present invention.

  That is, in the first and second embodiments, the number of repetitions of the first lens unit and the second lens unit arranged concentrically was 2 times and 4 times, respectively. However, the present invention is not limited to this, and may be a plurality of times. Note that, as described with reference to FIG. 7, with an increase in the number of repetitions of the first lens unit and the second lens unit arranged concentrically, the PSF at the time of shooting a normal subject at a standard distance, Since the PSF at the time of photographing a close subject that is closer than this is approximate, the accuracy of image modification processing can be improved by increasing the number of repetitions. The same applies to the third to sixth embodiments.

  In the first, second, third, and fifth embodiments, the lens unit arranged at the center, that is, the first lens unit is used as the lens unit that forms the far lens unit, and the second lens unit. However, the first lens unit is used as the lens unit constituting the near lens unit, and the second lens unit is used as the lens unit constituting the far lens unit. Good.

  On the other hand, in the fourth embodiment, the lens unit arranged at the center, that is, the first lens unit is a lens unit constituting the near lens unit, and the second lens unit is a lens configuring the far lens unit. However, the first lens unit may be the lens unit that forms the far lens unit, and the second lens unit may be the lens unit that configures the near lens unit.

  And in the said 6th Embodiment, the lens part arrange | positioned in the center, ie, the 1st lens part, is a lens part which comprises a far lens part, and the 2nd lens part is a lens which comprises a near lens part. The third lens unit is the lens unit that constitutes the intermediate lens unit, but the first lens unit may be a lens unit that constitutes the near lens unit or the intermediate lens unit, Alternatively, the arrangement order is not limited to the order of the lens part constituting the far lens part, the lens part constituting the near lens part, and the lens part constituting the intermediate lens part, and is arbitrary.

  Furthermore, the multifocal lenses 21, 221, 321, 421, and 521 of the first to fifth embodiments are configured by a lens unit having two focal lengths of a far lens unit and a near lens unit, and the sixth embodiment. The multifocal lens 621 of the embodiment is configured by a lens unit having three focal lengths of a far lens unit, a near lens unit, and an intermediate lens unit. However, the multifocal lens of the present invention is a bifocal lens or a trifocal lens. It is not limited to a lens, and may be configured by a lens unit having a focal length of 4 or more.

  In addition, the width of each lens portion constituting the multifocal lenses 21 and 221 of the first and second embodiments is not limited to the examples shown in FIGS. 2 and 5 and is arbitrary. However, from the viewpoint of realizing the image modification processing for removing the blur by processing using the same data, the total of the areas of the plurality of lens portions having the same focal length (area for the planar shape) is respectively For example, in the case of a bifocal lens, the total area of the plurality of first lens portions and the total area of the plurality of second lens portions are the same. , Preferably the same or substantially the same. The same applies to a multifocal lens having a focal length of 3 or more.

  Further, in the third embodiment, the main lens 324 is formed by integrating the base 325 and the close-up lens cutting pieces 326A, 326B, 326C, and 326D formed by cutting out from the close-up lens 326 that is a convex lens. However, the main lens may be formed by integrating a flat base and a concave lens cut piece formed by cutting out from a concave lens. In this case, the concave lens cut piece and The far lens part is constituted by the part where the concave lens cut piece is arranged in the base and the auxiliary lens which is a convex lens, the flat surface part where the concave lens cut piece is not arranged in the base, and the auxiliary lens which is a convex lens Thus, a near lens portion is configured.

  In the third to sixth embodiments, the convex lens cut piece and the concave lens cut piece are provided on the surface of the base (surface on the object side), but the convex lens is provided on the back of the base (surface on the image sensor 24 side). A cut piece or a concave lens cut piece may be provided, or a convex lens cut piece or a concave lens cut piece may be provided on both the front and back surfaces of the base.

  Moreover, in the said 3rd-6th embodiment, although the convex lens cut piece and the concave lens cut piece were provided in the surface of the board | substrate, and these diffraction pieces and the board | substrate were integrated, the diffraction lens was formed. The diffraction lens may be formed by processing a portion corresponding to the cut piece and a portion corresponding to the base from one material and finishing.

  Further, in the third, fifth, and sixth embodiments, one auxiliary lens 328, 528, and 628 is used. However, the auxiliary lens does not have to be a single lens, and includes a plurality of lenses. A combination lens may be used.

The image modification processing device 30 according to each of the embodiments described above is configured to perform a reproduction calculation using the convolution calculation matrix Q or Q _{m, j} , but is not limited thereto. A configuration may be adopted in which load addition calculation processing is performed on the output signal using an inverse function of the transfer function of the point spread function as a correction function.

  As described above, the multifocal lens and the imaging system of the present invention can capture a desired still image or moving image, for example, read a close still image such as a digital code, and recognize the digital code. It is suitable for use as an optical lens and an imaging system attached to an information terminal device or the like that can perform various processes based on the information of the recognized digital code.

1 is an overall configuration diagram of an imaging system including a multifocal lens according to a first embodiment of the present invention. 1 is a detailed configuration diagram of a multifocal lens according to a first embodiment. FIG. FIG. 3 is an explanatory diagram illustrating a state in which a projected image is formed on an image sensor when a subject having a bright spot only at one point (coordinates (m, j)) is imaged with a multifocal lens in the first embodiment. In the first embodiment, the method of defocusing differs between shooting a subject at a relatively long distance with a multifocal lens and shooting a subject at a relatively short distance with a multifocal lens. Explanatory drawing which shows that. The detailed block diagram of the multifocal lens of 2nd Embodiment of this invention. In the second embodiment, the method of defocusing differs between shooting a subject at a relatively long distance with a multifocal lens and shooting a subject at a relatively short distance with a multifocal lens. Explanatory drawing which shows that. By comparing the blur state (light quantity distribution) between the conventional multifocal lens, the multifocal lens of the first embodiment, and the multifocal lens of the second embodiment, and increasing the number of annular lens portions, A conceptual view showing how blur is evened out. The detailed block diagram of the multifocal lens of 3rd Embodiment of this invention. Explanatory drawing of the imaging | photography state by the multifocal lens of 3rd Embodiment. Explanatory drawing of the state in which light is refracted by the multifocal lens of a 3rd embodiment. The detailed block diagram of the multifocal lens of 4th Embodiment of this invention. Explanatory drawing of the imaging | photography state by the multifocal lens of 4th Embodiment. Explanatory drawing of the manufacturing method of the multifocal lens of 4th Embodiment. The detailed block diagram of the multifocal lens of 5th Embodiment of this invention. Explanatory drawing of the imaging | photography state by the multifocal lens of 5th Embodiment. The detailed block diagram of the multifocal lens of 6th Embodiment of this invention. Explanatory drawing of the imaging | photography state by the multifocal lens of 6th Embodiment. Explanatory drawing which shows a mode that the state of a defocusing differs by the case where a normal subject is image | photographed, and the case where a near subject is image | photographed.

Explanation of symbols

21, 221, 321, 521, 621 Multifocal lenses 22A, 222A Circular lens portions 22B, 222B, 222C, 222D as first lens portions Ring lens portions 23A, 23B, 223A as first lens portions 223B, 223C, 223D Annular lens portions 325A, 325B, 325C, 325D, 325E, 625A, 625B, 625C flat surface portions 326A, 326B, 326C, 326D, 426A, 426B, 426C, 426D, 426E Close-up lens cutting pieces for forming a diffractive lens 427A, 427B, 427C, 427D Standard shooting lens cut-out pieces for forming a diffractive lens 526A, 526B, 526C, 526D, 526E, 626A, 626B, 626C Diffraction lens by a concave lens Forming a standard taking lens cutout pieces 527A, 527B, 527C, 527D, 627A, 627B, close-up lens cutting pieces to form a diffractive lens according to 627C convex

Claims (13)

A multifocal lens with multiple focal lengths,
When N is an integer greater than or equal to 2, each lens unit having a different focal length from a plurality of first lens units having a first focal length to a plurality of Nth lens units having an Nth focal length , Integrated and configured,
The first to Nth lens parts are arranged concentrically repeatedly a plurality of times around the first lens part,
The planar shape of the first lens portion disposed at the center is a circle, an ellipse, a polygon, or a shape surrounded by other closed ring lines,
The multifocal lens, wherein the planar shape of the first lens unit disposed at a position other than the center and the planar shape of the lens unit other than the first lens unit are annular. The multifocal lens according to claim 1,
Each of the first to Nth lens portions is formed by arranging a diffractive lens, or is formed by a flat surface portion where no diffractive lens is arranged. The multifocal lens according to claim 2, wherein
N is 2, and the first lens unit and the second lens unit are alternately arranged concentrically around the first lens unit,
Either one of the first and second lens portions is formed by disposing a diffractive lens, and the other lens portion is formed by a flat surface portion where no diffractive lens is disposed. Multifocal lens characterized by The multifocal lens according to claim 3, wherein
The maximum dimension in the thickness direction of the step portion of the diffractive lens is such that the light passing through the diffractive lens and the light passing through the air are shifted by one wavelength or half wavelength. A multifocal lens. The multifocal lens according to claim 2, wherein
N is 2, and the first lens unit and the second lens unit are alternately arranged concentrically around the first lens unit,
The multifocal lens, wherein the first and second lens portions are formed by arranging diffractive lenses having different curvatures. The multifocal lens according to claim 5, wherein
The maximum dimension in the thickness direction of the step portion of the diffractive lens forming either one of the first lens portion or the second lens portion is the light passing through the diffractive lens and the air. A multifocal lens characterized in that the light passing therethrough is dimensioned to be shifted by one wavelength or half wavelength. The multifocal lens according to claim 2, wherein
N is 2, and the first lens unit and the second lens unit are alternately arranged concentrically around the first lens unit,
One of the first and second lens portions is formed by arranging a diffractive lens made of a concave lens, and the other lens portion is made by arranging a diffractive lens made of a convex lens. A multifocal lens characterized by that. The multifocal lens according to claim 7, wherein
The maximum dimension in the thickness direction of the step portion of the diffractive lens that forms at least one of the first and second lens portions is light that passes through the diffractive lens and air. The multifocal lens is characterized in that the size of the light to be shifted is one wavelength or half wavelength. The multifocal lens according to claim 2, wherein
N is 3, and the first lens unit to the third lens unit are concentrically repeated a plurality of times around the first lens unit,
Any one of the first to third lens portions is formed by disposing a diffractive lens by a concave lens, and the other lens portion is formed by disposing a diffractive lens by a convex lens. The remaining one lens portion is formed by a flat surface portion on which no diffractive lens is arranged. The multifocal lens according to claim 9, wherein
The maximum dimension in the thickness direction of the step portion of the diffractive lens forming at least one of the first to third lens portions is light passing through the diffractive lens and passing through the air. The multifocal lens is characterized in that the light to be transmitted is shifted by one wavelength, one third wavelength, or two third wavelengths. The multifocal lens according to claim 7 or 9,
The multifocal lens, wherein the concave lens and the convex lens have the same or substantially the same curvature. In an imaging system including an imaging mechanism that images a subject and an image modification processing device that improves the quality of an image captured by the imaging mechanism,
The imaging mechanism is
The multifocal lens according to any one of claims 1 to 11, which images the subject.
An image sensor that converts an image formed by the multifocal lens into an electrical signal and outputs the electrical signal;
The image modification processing apparatus includes:
A value of each element of a convolution calculation matrix calculated using a point spread function matrix indicating a state in which light emitted from one point of the subject spreads on the imaging device by the action of the multifocal lens; Brightness of light emitted by the subject by performing a convolution calculation process using values of each element of a matrix indicating an output signal of the imaging element for an image obtained by imaging with the multifocal lens An imaging system, characterized in that the value of each element of a matrix that indicates is calculated. In an imaging system including an imaging mechanism that images a subject and an image modification processing device that improves the quality of an image captured by the imaging mechanism,
The imaging mechanism is
The multifocal lens according to any one of claims 1 to 11, which images the subject.
An image sensor that converts an image formed by the multifocal lens into an electrical signal and outputs the electrical signal;
The image modification processing apparatus includes:
As a correction function, an inverse function of a transfer function of a point spread function indicating a state in which light emitted from one point of the subject spreads on the image sensor due to the action of the multifocal lens with respect to the output signal of the image sensor An imaging system characterized by being configured to perform load addition calculation processing.

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