Patent Publication Number: US-2022229461-A1

Title: Optical computing system

Description:
TECHNICAL FIELD 
     The present invention relates to a light diffraction element which carries out optical computing. Moreover, the present invention relates to an optical computing system which includes such a light diffraction element. 
     BACKGROUND 
     A light diffraction element is known that includes a plurality of microcells each of which has an individually set refractive index. This light diffraction element is designed such that light beams which have passed through the microcells are caused to interfere with each other to optically carry out predetermined computing. The optical computing using the light diffraction element can be carried out at a higher speed and low power consumption, as compared with electrical computing using a processor. Patent Literature  1  discloses an optical neural network having an input layer, an intermediate layer, and an output layer. The above light diffraction element can be utilized as, for example, an intermediate layer for such an optical neural network. 
     PATENT LITERATURE 
     Patent Literature 1: U.S. Pat. No. 7847225 
     In computing, it is sometimes necessary to refer to both information before the computing and information after the computing. As an example of such computing, in a defect extraction operation for extracting a defect of a subject in an image, an image before the operation is synthesized with an image after the operation, and thus an image can be obtained in which a checker can easily visually identify a type and a location of a defect in the subject. However, signal light which is obtained in a conventional optical computing system that uses the light diffraction element includes only signal light indicative of information after the computing, and does not include signal light indicative of information before the computing. Therefore, the conventional light diffraction element is not suitable for computing that needs to refer to both information before the computing and information after the computing. 
     One or more embodiments of the present invention provide an optical computing system which makes it possible to obtain signal light indicative of information before the computing, in addition to signal light indicative of information after the computing. 
     SUMMARY 
     An optical computing system in accordance with one or more embodiments of the present invention includes a light diffraction element group including n (n is a natural number of  2  or more) pieces of light diffraction elements, each of the light diffraction elements included in the light diffraction element group being constituted by a plurality of cells each of which has a thickness or a refractive index that is independently set, the plurality of cells being classified into two types of cells C 1  (i.e., “C 1  cells”) and C 2  (i.e., “C 2  cells”), and the thickness or the refractive index of each of the cells C 1  of each of the light diffraction elements included in the light diffraction element group being set so that optical computing that is carried out by the light diffraction element group becomes an identity operation when the cells C 2  of each of the light diffraction elements included in the light diffraction element group are masked. 
     According to one or more embodiments of the present invention, it is possible to provide an optical computing system which makes it possible to obtain signal light indicative of information before the computing, in addition to signal light indicative of information after the computing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a configuration of a light diffraction element in accordance with one or more embodiments of the present invention. 
         FIG. 2  is a perspective view illustrating a partially magnified portion of the light diffraction element illustrated in  FIG. 1 . 
         FIG. 3  is a perspective view illustrating a main part configuration of an optical computing system including the light diffraction element illustrated in  FIG. 1 . 
         FIG. 4  is a perspective view illustrating a first modification example of the optical computing system illustrated in  FIG. 3 . 
         FIG. 5  is a perspective view illustrating a second modification example of the optical computing system illustrated in  FIG. 3 . 
         FIG. 6  is a perspective view illustrating a third modification example of the optical computing system illustrated in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     [Configuration of Light Diffraction Element] 
     The following description will discuss a configuration of a light diffraction element  1  in accordance with one or more embodiments of the present invention with reference to  FIG. 1  and  FIG. 2 .  FIG. 1  is a plan view illustrating the light diffraction element  1 .  FIG. 2  is a perspective view in which a part (surrounded by the dashed lines in  FIG. 1 ) of the light diffraction element  1  is magnified. 
     The light diffraction element  1  is a planar light diffraction element and includes a plurality of microcells (an example of “cell” in claims) whose phase-change amounts are independently set. Here, the term “microcell” refers to a cell having a cell size of less than 10 μm. The term “cell size” refers to a square root of an area of a cell. For example, when a shape of a microcell in a plan view is a square shape, the cell size is a length of one side of the cell. A lower limit of the cell size is not particularly limited and can be, for example, 1 nm. 
     The light diffraction element  1  illustrated in  FIG. 1  is constituted by 12×12 microcells which are arranged in a matrix manner. A shape of each of the microcells in a plan view is a square shape having a size of 1 μm×1 μm, and a shape of the light diffraction element  1  in a plan view is a square shape having a size of 12 μm×12 μm. 
     The light diffraction element  1  includes two types of microcells C 1  and C 2  which are subjected to different types of optical computing. The microcells C 1  (white cells in  FIG. 1 ) are arranged in a staggered manner, and the microcells C 2  (shaded cells in  FIG. 1 ) are also arranged in a staggered manner. That is, each of the microcells C 1  abuts on four microcells C 2  at its respective four sides, and each of the microcells C 2  abuts on four microcells C 1  at its respective four sides. The light diffraction element  1  carries out (1) first optical computing that is performed by causing light beams, which have passed through the microcells C 1 , to interfere with each other and (2) second optical computing that is performed by causing light beams, which have passed through the microcells C 2 , to interfere with each other. Details of the first optical computing and the second optical computing will be described later with reference to other drawings. 
     A method for independently setting phase-change amounts of the microcells constituting the light diffraction element  1  for each cell can be (1) a method of independently setting a thickness of a microcell for each microcell, and (2) a method of independently selecting a refractive index of a microcell. In one or more embodiments, the method (1) which can be carried out by nanoimprinting is employed. In this case, each of the microcells C 1  and C 2  is constituted by a pillar having a square bottom surface and having a quadratic prism shape, as illustrated in  FIG. 2 . 
     [Configuration of Optical Computing System] 
     The following description will discuss a configuration of an optical computing system  10  including the light diffraction element  1 , with reference to  FIG. 3 .  FIG. 3  is a perspective view illustrating a configuration of the optical computing system  10 . 
     The optical computing system  10  includes a light diffraction element group  11 , a light-emitting device  12 , and a light-receiving device  13 . 
     The light diffraction element group  11  is constituted by n pieces of light diffraction elements  1  which are arranged parallel to each other. Here, n is a natural number of 2 or more and, in one or more embodiments, n is 3. Hereinafter, when it is necessary to distinguish the light diffraction elements  1  from each other, the first one of the light diffraction elements  1  from the light-emitting device  12  side is referred to as “first light diffraction element  1   a ”, the second one of the light diffraction elements  1  from the light-emitting device  12  side is referred to as “second light diffraction element  1   b ”, and the third one of the light diffraction elements  1  from the light-emitting device  12  side is referred to as “third light diffraction element  1   c”.    
     The light-emitting device  12  is a device for emitting signal light that is to be input to the light diffraction element group  11 . The light-emitting device  12  has a plurality of cells which are arranged in a matrix manner and is constituted by, for example, a two-dimensional display. The cells in the light-emitting device  12  correspond to, for example, respective microcells of the light diffraction element  1  (i.e., one-to-one correspondence). Signal light, which has been output from each cell of the light-emitting device  12 , is input to a corresponding microcell of the first light diffraction element  1   a.    
     The signal light which has passed through each of the microcells C 1  of the first light diffraction element  1   a  mainly interferes with signal light which has passed through another microcell C 1  of the first light diffraction element  1   a,  and is mainly input to each of the microcells C 1  of the second light diffraction element  1   b.  Meanwhile, the signal light which has passed through each of the microcells C 2  of the first light diffraction element  1   a  mainly interferes with signal light which has passed through another microcell C 2  of the first light diffraction element  1   a,  and is mainly input to each of the microcells C 2  of the second light diffraction element  1   b.    
     Moreover, the signal light which has passed through each of the microcells C 1  of the second light diffraction element  1   b  mainly interferes with signal light which has passed through another microcell C 1  of the second light diffraction element  1   b,  and is mainly input to each of the microcells C 1  of the third light diffraction element  1   c.  Meanwhile, the signal light which has passed through each of the microcells C 2  of the second light diffraction element  1   b  mainly interferes with signal light which has passed through another microcell C 2  of the second light diffraction element  1   b,  and is mainly input to each of the microcells C 2  of the third light diffraction element  1   c.    
     The light-receiving device  13  is a device for detecting signal light that has been output from the light diffraction element group  11 . The light-receiving device  13  has a plurality of cells which are arranged in a matrix manner and is constituted by, for example, a two-dimensional image sensor. The cells in the light-receiving device  13  correspond to respective microcells of the light diffraction element  1  (i.e., one-to-one correspondence). The signal light which has passed through each of the microcells C 1  of the third light diffraction element  1   c  mainly interferes with signal light which has passed through another microcell Cl of the third light diffraction element  1   c,  and is mainly input to each cell of the light-receiving device  13  corresponding to that microcell C 1 . Meanwhile, the signal light which has passed through each of the microcells C 2  of the third light diffraction element  1   c  mainly interferes with signal light which has passed through another microcell C 2  of the third light diffraction element  1   c,  and is mainly input to each cell of the light-receiving device  13  corresponding to that microcell C 2 . 
     A thickness or a refractive index of each of the microcells C 1  of the light diffraction elements  1   a  through  1   c  is set so that optical computing that is carried out by the light diffraction element group  11  becomes an identity operation when the microcells C 2  of the light diffraction elements  1   a  through  1   c  are masked. In other words, the thickness or refractive index of each of the microcells C 1  of the light diffraction elements  1   a  through  1   c  is set so that a phase distribution or intensity distribution of signal light output from the microcells C 1  of the third light diffraction element  1   c  conforms to a phase distribution or intensity distribution of signal light input to the microcells C 1  of the first light diffraction element  1   a,  when the microcells C 2  of the light diffraction elements  1   a  through  1   c  are masked. Meanwhile, a thickness or a refractive index of each of the microcells C 2  of the light diffraction elements  1   a  through  1   c  is set so that optical computing that is carried out by the light diffraction element group  11  becomes an operation other than an identity operation when the microcells C 1  of the light diffraction elements  1   a  through  1   c  are masked. In other words, the thickness or refractive index of each of the microcells C 2  of the light diffraction elements  1   a  through  1   c  is set so that a phase distribution or intensity distribution of signal light output from the microcells C 2  of the third light diffraction element  1   c  does not conform to a phase distribution or intensity distribution of signal light input to the microcells C 2  of the first light diffraction element  1  a, when the microcells C 1  of the light diffraction elements  1   a  through  1   c  are masked. 
     Therefore, among the cells constituting the light-receiving device  13 , signal light detected by cells corresponding to the microcells C 1  of the light diffraction elements  1   a  through  1   c  indicates information before the computing. Here, the term “information before the computing” refers to information indicated by signal light that is output from, among the cells constituting the light-emitting device  12 , cells corresponding to the microcells C 1  of the light diffraction elements  1   a  through  1   c.  Meanwhile, among the cells constituting the light-receiving device  13 , signal light detected by cells corresponding to the microcells C 2  of the light diffraction elements  1   a  through  1   c  indicates information after the computing. Here, the term “information after the computing” refers to information obtained by applying predetermined computing to information indicated by signal light that is output from, among the cells constituting the light-emitting device  12 , cells corresponding to the microcells C 1  of the light diffraction elements  1   a  through  1   c.    
     As described above, according to the optical computing system  10 , it is possible to achieve, with use of the light diffraction element group  11 , optical computing for deriving information after the computing while preserving information before the computing. For example, the optical computing system  10  can be suitably used for a defect extraction operation for extracting a defect of a subject from an image. In this case, when an original image is displayed on the light-emitting device  12  which is a display device, the light-receiving device  13  can detect the original image and a defect image which includes only a defect extracted from the original image as a subject. 
     In one or more embodiments, the configuration is employed in which signal light output from the light-emitting device  12  is directly input to the light diffraction element group  11 , and signal light output from the light diffraction element group  11  is directly input to the light-receiving device  13 . Note, however, that the present invention is not limited to this configuration. For example, it is possible to employ a configuration in which one or more other light diffraction elements are provided on an optical path of signal light output from the light-emitting device  12 , and light which has passed through the one or more other light diffraction elements is input to the light diffraction element group  11 . Alternatively, it is possible to employ a configuration in which one or more other light diffraction elements are provided on an optical path of signal light output from the light diffraction element group  11 , and light which has passed through the one or more other light diffraction elements is input to the light-receiving device  13 . Such modification examples are illustrated in  FIGS. 4 through 6 . An optical computing system  10 A illustrated in  FIG. 4  employs a configuration in which one light diffraction element  14  is provided at a preceding stage of the light diffraction element group  11 , and signal light output from the light diffraction element  14  is input to the light diffraction element group  11 . An optical computing system  10 B illustrated in  FIG. 5  employs a configuration in which one light diffraction element  15  is provided at a following stage of the light diffraction element group  11 , and signal light output from the light diffraction element group  11  is input to the light diffraction element  15 . An optical computing system  10 C illustrated in  FIG. 6  employs a configuration in which one light diffraction element  14  is provided at a preceding stage of the light diffraction element group  11 , and one light diffraction element  15  is provided at a following stage of the light diffraction element group  11 . 
     An optical computing system in accordance with one or more embodiments of the present invention includes a light diffraction element group including n (n is a natural number of 2 or more) pieces of light diffraction elements, each of the light diffraction elements included in the light diffraction element group being constituted by a plurality of cells each of which has a thickness or a refractive index that is independently set, the plurality of cells being classified into two types of cells C 1  and C 2 , and the thickness or the refractive index of each of the cells C 1  of each of the light diffraction elements included in the light diffraction element group being set so that optical computing that is carried out by the light diffraction element group becomes an identity operation when the cells C 2  of each of the light diffraction elements included in the light diffraction element group are masked. 
     According to the configuration, it is possible to output signal light indicative of information after the computing from cells C 2  of an n-th light diffraction element, and to output signal light indicative of information before the computing from cells C 1  of the n-th light diffraction element. 
     The optical computing system in accordance with one or more embodiments of the present invention employs, in addition to the configuration of the embodiments described above, a configuration in which, in each of the light diffraction elements included in the light diffraction element group, the cells C 1  are arranged in a staggered manner, and the cells C 2  are arranged in a staggered manner. 
     According to the configuration, it is possible to output signal light indicative of information after the computing from cells C 2  of an n-th light diffraction element, and to output signal light indicative of information before the computing from cells C 1  of the n-th light diffraction element. 
     The optical computing system in accordance with one or more embodiments of the present invention employs, in addition to the configuration of the embodiments described above, a configuration of further including: one or more other light diffraction elements arranged at a preceding stage of a first light diffraction element included in the light diffraction element group; and/or one or more other light diffraction elements arranged at a following stage of an n-th light diffraction element included in the light diffraction element group. 
     According to the configuration, it is possible to input, to the light diffraction element group, signal light which has been output from one or more other light diffraction elements arranged at a preceding stage of the first light diffraction element, and/or to input signal light which has been output from the light diffraction element group to one or more other light diffraction elements which are arranged at a following stage of the n-th light diffraction element. 
     The optical computing system in accordance with one or more embodiments of the present invention employs, in addition to the configuration of any of the embodiments described above, a configuration of further including: a light-emitting device that emits signal light which is input to a first light diffraction element included in the light diffraction element group or emits signal light which is input to one or more other light diffraction elements arranged at a preceding stage of the first light diffraction element; and a light-receiving device that detects signal light which is output from an n-th light diffraction element included in the light diffraction element group or detects signal light which is output from one or more other light diffraction elements arranged at a following stage of the n-th light diffraction element. 
     According to the configuration, among the cells constituting the light-receiving device, signal light indicative of information before the computing can be detected by cells corresponding to the cells C 1  of the light diffraction element. Alternatively, among the cells constituting the other light diffraction element, signal light indicative of information before the computing can be input to cells corresponding to the cells C 1  of the light diffraction element. Here, the term “information before the computing” refers to information indicated by signal light that is output from, among the cells constituting the light-emitting device, cells corresponding to the cells C 1  of the light diffraction element. Moreover, according to the configuration, among the cells constituting the light-receiving device, signal light indicative of information after the computing can be detected by cells corresponding to the cells C 2  of the light diffraction element. Alternatively, among the cells constituting the other light diffraction element, signal light indicative of information after the computing can be input to cells corresponding to the cells C 2  of the light diffraction element. Here, the term “information after the computing” refers to information obtained by applying predetermined computing to information indicated by signal light that is output from, among the cells constituting the light-emitting device, cells corresponding to the cells C 2  of the light diffraction element. 
     The optical computing system in accordance with one or more embodiments of the present invention employs, in addition to the configuration of any of the embodiments described above, a configuration in which: the thickness or the refractive index of each of the cells C 2  of each of the light diffraction elements included in the light diffraction element group is set so that optical computing that is carried out by the light diffraction element group becomes an operation other than an identity operation when the cells C 1  of each of the light diffraction elements included in the light diffraction element group are masked. 
     According to the configuration, it is possible to output signal light indicative of information after the computing from cells C 2  of an n-th light diffraction element, and to output signal light indicative of information before the computing from cells C 1  of the n-th light diffraction element. 
     [Additional Remarks] 
     The present invention is not limited to the embodiments described above, but may be altered in various ways by a skilled person within the scope of the claims. Any embodiments based on proper combinations of technical means disclosed in the embodiments is also encompassed in the technical scope of the present invention. 
     Note that the “light diffraction element” in this specification is an element for converting an optical signal indicative of certain information (for example, a certain image) into an optical signal indicative of other information (for example, another image). Therefore, the “light diffraction element” in this specification can alternatively be referred to as “optical filter”, as in a case in which an element for converting an electrical signal indicative of a certain image into an electrical signal indicative of another image is called “filter”. In this case, the optical computing system disclosed in this specification can also be expressed as follows. 
     An optical computing system in accordance with one or more embodiments includes an optical filter group including n (n is a natural number of 2 or more) pieces of optical filters, each of the optical filters included in the optical filter group including a plurality of cells for each of which a refractive index is independently set, the plurality of cells being classified into two types of cells C 1  and C 2 , and the refractive index of each of the cells C 1  of each of the optical filters included in the optical filter group being set so that a phase distribution of signal light output from the cells C 1  of an n-th optical filter conforms to a phase distribution of signal light input to the cells C 1  of a first optical filter. 
     The optical computing system in accordance with one or more embodiments employs, in addition to the configuration of the embodiments described above, a configuration in which, in each of the optical filters included in the optical filter group, the cells C 1  are arranged in a staggered manner, and the cells C 2  are arranged in a staggered manner. 
     The optical computing system in accordance with one or more embodiments employs, in addition to the configuration of the embodiments described above, a configuration of further including: one or more other optical filters arranged at a preceding stage of the first optical filter; and/or one or more other optical filters arranged at a following stage of the n-th optical filter. 
     The optical computing system in accordance with one or more embodiments employs, in addition to the configuration of any of the embodiments described above, a configuration of further including: a light-emitting device that emits signal light which is input to the first optical filter or emits signal light which is input to one or more other optical filters arranged at a preceding stage of the first optical filter; and a light-receiving device that detects signal light which is output from the n-th optical filter or detects signal light which is output from one or more other optical filters arranged at a following stage of the n-th optical filter. 
     Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims. 
     REFERENCE SIGNS LIST 
       1 ,  1   a  through  1   c:  Light diffraction element 
       10 : Optical computing system 
       11 : Light diffraction element group 
       12 : Light-emitting device 
       13 : Light-receiving device