Light receiving device, receiving device, and communication device

Abstract

Provided is a light-receiving device comprising: a condenser lens which, in order to efficiently receive a spatial optical signal arriving from an arbitrary direction, condenses the spatial optical signal; a variable lens on which a lens region is formed at an arbitrary position, and which focuses, in the lens region, an optical signal derived from the spatial optical signal condensed by the condenser lens; a control unit which forms the lens region at a desired position on the variable lens and controls the emission direction of the optical signal emitted from the variable lens; and a light-receiving element on which light-receiving unit is arranged so as to face the variable lens and which receives the optical signal focused by the variable lens.

Description

[Technical Field]

[0001] The present disclosure relates to a light receiving device that receives a spatial optical signal. [Background technology]

[0002] In optical space communications, optical signals (hereinafter referred to as spatial optical signals) that propagate through space are transmitted and received without using a medium such as an optical fiber. In order to receive spatial optical signals that propagate through space, a focusing lens as large as possible is required. Furthermore, in optical space communications, a photodiode with a small capacitance is required to enable high-speed communications. Because the light-receiving surface of such a photodiode is very small, it is difficult to focus spatial optical signals arriving from various directions onto the light-receiving surface using a large focusing lens.

[0003] Patent Document 1 discloses a light-receiving device that filters condensed light. The device in Patent Document 1 includes a first condensing lens, a collimating lens, a bandpass filter, and a light-receiving element. The collimating lens has a focal length shorter than that of the first condensing lens and converts the light condensed by the condensing lens into parallel light. The parallel light from the collimating lens is incident perpendicularly on the filter surface of the bandpass filter. The light that passes through the bandpass filter, which transmits only the wavelength of the incident light, is received by the light-receiving element. Patent Document 1 also discloses a configuration that makes it easier to guide the light condensed by the condensing lens to the light-receiving element by arranging a second condensing lens that condenses light that has passed through the bandpass filter and by arranging an aperture at the focal position of the condensing lens. Patent Document 1 also discloses a mechanism that moves the condensing lens and aperture in three axial directions to adjust them to optimal positions according to the angle of incidence of the light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-186595 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the technique of Patent Document 1, spatial light can be guided to a light receiving element by focusing light that has passed through a bandpass filter onto a second focusing lens, or by adjusting the focusing lens or aperture to an optimal position according to the angle of incidence of the light. However, with the technique of Patent Document 1, the intensity of the light guided to the light receiving element changes depending on the angle of incidence of the spatial light. Therefore, with the technique of Patent Document 1, spatial light cannot be efficiently received depending on the direction from which the spatial light arrives.

[0006] An object of the present disclosure is to provide a light receiving device or the like that can efficiently receive a spatial optical signal arriving from any direction. [Means for solving the problem]

[0007] An optical receiving device according to one aspect of the present disclosure includes a focusing lens that focuses a spatial optical signal, a variable lens that has a lens area formed at an arbitrary position and focuses an optical signal derived from the spatial optical signal focused by the focusing lens in the lens area, a control unit that forms the lens area at a desired position of the variable lens and controls the emission direction of the optical signal emitted from the variable lens, and a light receiving element that is arranged with its light receiving unit facing the variable lens and receives the optical signal focused by the variable lens. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a light receiving device or the like that can efficiently receive a spatial optical signal arriving from any direction. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a conceptual diagram illustrating an example of the configuration of a light receiving device according to a first embodiment. [Figure 2] FIG. 2 is a conceptual diagram illustrating an example of a trajectory of light in the light receiving device according to the first embodiment. [Figure 3] FIG. 4 is a conceptual diagram showing another example of the trajectory of light in the light receiving device according to the first embodiment. [Figure 4] 4A and 4B are conceptual diagrams illustrating an example of control of a liquid crystal lens in the light receiving device according to the first embodiment. [Figure 5] FIG. 10 is a conceptual diagram illustrating an example of the configuration of a light receiving device according to a second embodiment. [Figure 6] FIG. 10 is a conceptual diagram illustrating an example of the configuration of an imaging unit of a light receiving device according to a second embodiment. [Figure 7] FIG. 10 is a conceptual diagram illustrating an example of the configuration of a light receiving device according to a third embodiment. [Figure 8] FIG. 10 is a conceptual diagram showing an example of a trajectory of light in the light receiving device of the third embodiment. [Figure 9] FIG. 10 is a conceptual diagram illustrating an example of the configuration of a light receiving device according to a fourth embodiment. [Figure 10] FIG. 10 is a conceptual diagram showing an example of a trajectory of light in the light receiving device according to the fourth embodiment. [Figure 11] FIG. 10 is a conceptual diagram showing an example of a virtual lens image displayed on the surface of a liquid crystal lens of the light receiving device according to the fourth embodiment. [Figure 12] FIG. 10 is a conceptual diagram showing an example of a trajectory of light in a modified example of the light receiving device of the fourth embodiment. [Figure 13] FIG. 10 is a conceptual diagram illustrating an example of the configuration of a light receiving device according to a fifth embodiment. [Figure 14] FIG. 11 is a conceptual diagram showing an example of a trajectory of light in a light receiving device according to a fifth embodiment. [Figure 15] FIG. 11 is a block diagram showing an example of the configuration of a decoder included in a light receiving device according to a fifth embodiment. [Figure 16] FIG. 13 is a conceptual diagram illustrating an example of the configuration of a light receiving device according to a sixth embodiment. [Figure 17] FIG. 13 is a conceptual diagram showing an example of a trajectory of light in the light receiving device according to the sixth embodiment. [Figure 18] FIG. 13 is a conceptual diagram showing an example of a trajectory of light in a modified example of the light receiving device of the sixth embodiment. [Figure 19]FIG. 13 is a block diagram showing an example of the configuration of a decoder included in a light receiving device according to a sixth embodiment. [Figure 20] FIG. 13 is a conceptual diagram illustrating an example of the configuration of a communication device according to a seventh embodiment. [Figure 21] FIG. 13 is a conceptual diagram illustrating an example of the configuration of a light transmitting unit included in a communication device according to a seventh embodiment. [Figure 22] FIG. 13 is a conceptual diagram for explaining an application example of a communication device according to a seventh embodiment. [Figure 23] FIG. 13 is a conceptual diagram illustrating an example of the configuration of a light receiving device according to an eighth embodiment. [Figure 24] FIG. 2 is a block diagram showing an example of a hardware configuration for executing control and processing in each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the embodiments described below are limited in a manner that is technically preferable for carrying out the present invention, but the scope of the invention is not limited to the following. In all the drawings used to describe the following embodiments, the same reference numerals are used for similar parts unless there is a particular reason. In all the drawings used to describe the following embodiments, the reference numerals for similar configurations may be omitted. In the following embodiments, repeated description of similar configurations and operations may be omitted.

[0011] In all the drawings used to explain the following embodiments, the direction of the arrows in the drawings is merely an example and does not limit the direction of light or signals. Furthermore, the lines showing the trajectories of light in the drawings are conceptual and do not accurately represent the actual traveling direction or state of light. For example, in the following drawings, changes in the traveling direction or state of light due to refraction, reflection, diffusion, etc. at the interface between air and a substance may be omitted, or a light beam may be represented by a single line.

[0012] (First embodiment) First, a light receiving device according to a first embodiment will be described with reference to the drawings. The light receiving device of this embodiment is used for optical space communication in which an optical signal propagating through space (hereinafter also referred to as a spatial optical signal) is transmitted and received without using a medium such as an optical fiber. The light receiving device of this embodiment may be used for applications other than optical space communication as long as it receives light propagating through space. In the following, unless otherwise specified, the spatial optical signal is considered to be parallel light because it arrives from a position sufficiently distant.

[0013] (composition) FIG. 1 is a conceptual diagram showing an example of the configuration of a light receiving device 10 of this embodiment. The light receiving device 10 includes a condenser lens 11, a liquid crystal lens 13, a light receiving element 15, and a control unit 17. FIGS. 2 and 3 are conceptual diagrams for explaining an example of the trajectory of light received by the light receiving device 10. FIGS. 1 and 2 are views of the internal configuration of the light receiving device 10 as seen from the side. FIG. 3 is a perspective view of the internal configuration of the light receiving device 10 as seen from a diagonally forward perspective on the incident surface side.

[0014] The condenser lens 11 is an optical element that condenses a spatial optical signal received from the outside. The light (also referred to as an optical signal) derived from the spatial optical signal condensed by the condenser lens 11 is condensed toward the incident surface of the liquid crystal lens 13. For example, the condenser lens 11 can be made of a material such as glass or plastic. For example, the condenser lens 11 is realized by a material such as quartz. When the spatial optical signal is light in the infrared region (hereinafter also referred to as infrared), it is preferable that the condenser lens 11 is made of a material that transmits infrared light. For example, the condenser lens 11 may be realized by a material such as silicon, germanium, or a chalcogenide-based material. Note that there is no limitation on the material of the condenser lens 11 as long as it can refract and transmit light in the wavelength region of the spatial optical signal.

[0015] Liquid crystal lens 13 (also called a variable lens) is disposed after condenser lens 11. Liquid crystal lens 13 is disposed so that its incident surface faces the exit surface of condenser lens 11. In order for the optical signal to be efficiently received by light receiving element 15, liquid crystal lens 13 is preferably disposed so that the incident surface of liquid crystal lens 13 is located in front of the focal position of condenser lens 11.

[0016] The liquid crystal lens 13 is a lens using liquid crystal. For example, the liquid crystal lens 13 has a structure in which a liquid crystal lens body, in which liquid crystal is sealed between two alignment films, is sandwiched between two transparent conductive films. The refractive index of the liquid crystal lens 13 changes depending on the voltage applied between the two transparent conductive films. The range of the focal length of the liquid crystal lens 13 is set depending on the refractive index of the material constituting the liquid crystal lens 13. A lens region 130 is formed at any location on the liquid crystal lens 13 under the control of the control unit 17. For example, a lens region can be formed at any location on the liquid crystal lens 13 by adjusting the portion to which a voltage is applied. The focal length of the lens region 130 formed on the liquid crystal lens 13 can be changed depending on the applied voltage. Multiple lens regions 130 can be formed on the liquid crystal lens 13. The focusing direction and focal length of the multiple lens regions 130 formed on the liquid crystal lens 13 can be individually set by adjusting the applied voltage.

[0017] In response to control by the control unit 17, the liquid crystal lens 13 diffracts an optical signal incident from its incident surface onto the lens region 130, and emits the diffracted optical signal from its exit surface toward the region where the light receiving element 15 is disposed. That is, the emission direction of the optical signal incident on the liquid crystal lens 13 is controlled by the control by the control unit 17, and the optical signal is focused toward the light receiving unit 150 of the light receiving element 15. FIGS. 2 and 3 show an example in which a spatial optical signal incident on the condenser lens 11 is condensed by the condenser lens 11 and incident on the lens region 130 of the liquid crystal lens 13. The liquid crystal lens 13 emits the optical signal incident on the lens region 130 toward the region where the light receiving element 15 is disposed. As a result, the optical signal derived from the spatial optical signal is received by the light receiving unit 150 of the light receiving element 15.

[0018] Light receiving element 15 is disposed after liquid crystal lens 13. Light receiving element 15 has a light receiving unit 150 that receives the optical signal emitted from liquid crystal lens 13. Light receiving element 15 is disposed so that light receiving unit 150 faces the emission surface of liquid crystal lens 13. Light receiving element 15 receives the optical signal emitted from liquid crystal lens 13 at light receiving unit 150.

[0019] The light receiving element 15 receives light in the wavelength range of the optical signal to be received. For example, the light receiving element 15 receives an optical signal in the visible range. For example, the light receiving element 15 receives an optical signal in the infrared range. The light receiving element 15 receives an optical signal with a wavelength in the 1.5 μm (micrometer) band, for example. Note that the wavelength band of the optical signal received by the light receiving element 15 is not limited to the 1.5 μm band. The wavelength band of the optical signal received by the light receiving element 15 can be set arbitrarily to match the wavelength of the spatial optical signal transmitted from the light transmitting device (not shown). The wavelength band of the optical signal received by the light receiving element 15 may be set to, for example, the 0.8 μm band, the 1.55 μm band, or the 2.2 μm band. The wavelength band of the optical signal received by the light receiving element 15 may also be, for example, the 0.8 to 1 μm band. A shorter wavelength band of the optical signal is advantageous for optical space communication during rainfall because it is less absorbed by moisture in the atmosphere. The light receiving element 15 may also receive an optical signal in the visible region. If the light receiving element 15 is saturated with intense sunlight, it will not be able to read the optical signal derived from the spatial optical signal. Therefore, a color filter that selectively passes light in the wavelength band of the spatial optical signal may be installed before the light receiving element 15.

[0020] The light receiving element 15 converts the received optical signal into an electrical signal. The light receiving element 15 outputs the converted electrical signal to a decoder (not shown). For example, the light receiving element 15 can be realized by an element such as a photodiode or a phototransistor. For example, the light receiving element 15 can be realized by an avalanche photodiode. The light receiving element 15 realized by an avalanche photodiode can support high-speed communication. Note that the light receiving element 15 may be realized by an element other than a photodiode, phototransistor, or avalanche photodiode, as long as it can convert an optical signal into an electrical signal.

[0021] To improve communication speed, it is preferable that the light receiving section 150 of the light receiving element 15 be as small as possible. For example, the light receiving section 150 of the light receiving element 15 has a light receiving area with a diameter of approximately 0.1 to 0.3 mm (millimeters). The optical signal collected by the condensing lens 11 is collected within a certain range depending on the direction of arrival of the spatial optical signal, but cannot be collected in the predetermined area where the light receiving section 150 of the light receiving element 15 is located. In this embodiment, the optical signal collected by the condensing lens 11 is guided to the area where the light receiving section 150 of the light receiving element 15 is located using a liquid crystal lens 13 that selectively guides the optical signal collected by the condensing lens 11 to a predetermined area. Therefore, the light receiving device 10 can efficiently guide the spatial optical signal arriving at the incident surface of the condensing lens 11 from any direction to the light receiving section 150 of the light receiving element 15.

[0022] The control unit 17 controls the liquid crystal lens 13 so that an optical signal incident on the incident surface of the liquid crystal lens 13 is emitted toward a position (predetermined region) where the light receiving unit 150 of the light receiving element 15 is arranged. For example, the control unit 17 is realized by a microcomputer including a processor and a memory. For example, the control unit 17 forms a lens region 130 at a desired position on the liquid crystal lens 13 by controlling a voltage applied to the liquid crystal lens 13. The control unit 17 changes the refractive index of the lens region 130 by adjusting the voltage applied to the liquid crystal lens 13. By changing the refractive index of the lens region 130, the spatial optical signal incident on the liquid crystal lens 13 is appropriately diffracted in accordance with the refractive index of the lens region 130. In other words, the spatial optical signal incident on the liquid crystal lens 13 is diffracted in accordance with the optical properties of the lens region 130. Note that the method of driving the liquid crystal lens 13 by the control unit 17 is not limited to the above.

[0023] Fig. 4 is a conceptual diagram for explaining an example of control of liquid crystal lens 13 by control unit 17. Fig. 4 is a diagram showing the internal configuration of light receiving device 10 as viewed from the side. In the control example of Fig. 4, control unit 17 is connected to light receiving element 15. Control unit 17 receives the optical signal received by light receiving element 15 and measures the intensity of the optical signal.

[0024] The control unit 17 performs light direction detection to detect the arrival direction of the spatial optical signal of the optical signal condensed by the condensing lens 11 according to the position where the optical signal is incident on the liquid crystal lens 13. For example, the control unit 17 moves the lens region 130 within a predetermined range to scan the emission direction of the optical signal. For example, the control unit 17 moves the lens region 130 within a predetermined range along the vertical or horizontal direction to scan the emission direction of the optical signal. The control unit 17 adjusts the lens region so that it is formed in a region where the intensity of the optical signal received by the light receiving element 15 (also referred to as received light intensity) is maximized.

[0025] The control unit 17 detects the light direction at a predetermined timing. The timing of the light direction detection by the control unit 17 can be set arbitrarily. For example, the control unit 17 is set to detect the light direction at the timing when the light receiving element 15 receives an optical signal derived from the spatial optical signal. For example, the control unit 17 detects the light direction when reception of an optical signal derived from a spatial optical signal arriving from the same arrival direction begins. For example, the control unit 17 detects the light direction at the timing when the receiving position of the optical signal on the incident surface of the liquid crystal lens 13 changes. For example, the control unit 17 detects the light direction at the timing when the received light intensity of the optical signal changes to or above a threshold. If the arrival direction of the spatial optical signal is fixed, it is not necessary to detect the light direction.

[0026] As described above, the light receiving device of this embodiment includes a condensing lens, a liquid crystal lens, a control unit, and a light receiving element. The condensing lens receives a spatial optical signal. The liquid crystal lens (variable lens) has a lens region formed at an arbitrary position. The liquid crystal lens focuses, in the lens region, an optical signal derived from the spatial optical signal focused by the condensing lens. The control unit forms the lens region at a desired position on the liquid crystal lens. The control unit controls the emission direction of the optical signal emitted from the liquid crystal lens. The light receiving element is arranged with the light receiving unit facing the liquid crystal lens. The light receiving element receives the optical signal focused by the liquid crystal lens.

[0027] In the light receiving device of this embodiment, the optical signal collected by the collecting lens is diffracted by the lens region formed in the variable lens and guided to the light receiving portion of the light receiving element, so that spatial light arriving from any direction can be efficiently received.

[0028] In one aspect of this embodiment, the liquid crystal lens (variable lens) is a transmissive liquid crystal lens. The control unit forms a lens region at a desired position on the liquid crystal lens by adjusting the voltage applied to the liquid crystal lens. According to this aspect, by forming the lens region at the desired position on the liquid crystal lens, spatial light arriving from any direction can be efficiently received.

[0029] In one aspect of this embodiment, the control unit scans the emission direction of the optical signal emitted from the liquid crystal lens (variable lens) by moving the position of the lens region. The control unit detects the arrival direction of the spatial optical signal based on the received light intensity of the optical signal by the light receiving element. The control unit forms a lens region on the variable lens according to the detected arrival direction of the spatial optical signal. According to this aspect, the direction in which the liquid crystal lens focuses the optical signal can be optimized according to the arrival direction of the spatial optical signal, thereby improving the reception efficiency of the optical signal by the light receiving element.

[0030] (Second embodiment) Next, a light receiving device according to a second embodiment will be described with reference to the drawings. The light receiving device according to this embodiment includes an imaging unit (camera) for detecting the direction of arrival of a spatial optical signal. Note that the imaging unit may be used for purposes other than detecting the direction of arrival of a spatial optical signal.

[0031] (composition) Fig. 5 is a conceptual diagram showing an example of the configuration of the light receiving device 20 of this embodiment. The light receiving device 20 includes a condenser lens 21, a liquid crystal lens 23, a light receiving element 25, an imaging unit 26, and a control unit 27. Fig. 5 is a diagram showing the internal configuration of the light receiving device 20 as viewed from the side.

[0032] The condenser lens 21 is an optical element that condenses a spatial optical signal arriving from the outside. The optical signal condensed by the condenser lens 21 is condensed toward the incident surface of the liquid crystal lens 23. The condenser lens 21 has the same configuration as the condenser lens 11 of the first embodiment.

[0033] The liquid crystal lens 23 (also referred to as a variable lens) is disposed after the condenser lens 21. The liquid crystal lens 23 is disposed so that its incident surface faces the exit surface of the condenser lens 21. A lens region 230 is formed in the liquid crystal lens 23 under the control of the control unit 27. An optical signal incident on the incident surface of the liquid crystal lens 23 is diffracted by the lens region 230 formed under the control of the control unit 27, and is emitted toward the light receiving unit 250 of the light receiving element 25. The liquid crystal lens 23 has the same configuration as the liquid crystal lens 13 of the first embodiment.

[0034] The light receiving element 25 is arranged after the liquid crystal lens 23. The light receiving element 25 has a light receiving section 250 that receives an optical signal focused by the liquid crystal lens 23. The light receiving element 25 is arranged so that its light receiving section 250 faces the exit surface of the liquid crystal lens 23. The light receiving element 25 is arranged so that the light receiving section 250 is located in a predetermined area. The optical signal emitted from the liquid crystal lens 23 is received by the light receiving section 250 of the light receiving element 25 located in the predetermined area. The light receiving element 25 converts the received optical signal into an electrical signal. The light receiving element 25 outputs the converted electrical signal to a decoder (not shown). The light receiving element 25 has the same configuration as the light receiving element 15 of the first embodiment.

[0035] The imaging unit 26 is disposed with its imaging direction facing the direction from which the spatial optical signal arrives. The imaging unit 26 captures an image for detecting the spatial optical signal arriving from outside. For example, the imaging unit 26 has the function of a digital camera. The entrance surface of the lens of the imaging unit 26 is disposed facing in the same direction as the entrance surface of the condenser lens 21. The imaging unit 26 captures an image in the direction from which the spatial optical signal arrives. The imaging unit 26 outputs the captured image to the control unit 27.

[0036] 6 is a conceptual diagram showing an example of the configuration of the imaging unit 26. The imaging unit 26 has a lens 260, an imaging element 261, an image processing processor 263, an internal memory 265, and a data output circuit 267.

[0037] The lens 260 is an optical element for capturing an image of the direction of arrival of the spatial optical signal. The lens 260 can be made of materials such as glass or plastic. For example, the lens 260 is made of a material such as quartz. When the spatial optical signal is light in the infrared region (hereinafter also referred to as infrared), it is preferable that the lens 260 be made of a material that transmits infrared light. For example, the lens 260 may be made of silicon, germanium, or a chalcogenide-based material. Note that there are no limitations on the material of the lens 260 as long as it can refract and transmit light in the wavelength region of the spatial optical signal.

[0038] The imaging element 261 is an element for capturing an image of the direction of arrival of a spatial optical signal and detecting the direction of arrival. The imaging element 261 is a photoelectric conversion element in which semiconductor components are integrated. The imaging element 261 can be realized by, for example, a solid-state imaging element such as a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor). The imaging element 261 has a number of pixels capable of detecting the direction of arrival of a spatial optical signal. Typically, the imaging element 261 captures light in the visible range. The imaging element 261 may also be configured by an element capable of capturing infrared light, ultraviolet light, or the like.

[0039] The image processor 263 is an integrated circuit that performs image processing such as dark current correction, interpolation, color space conversion, gamma correction, aberration correction, noise reduction, and image compression on the image data captured by the image sensor 261 and converts the data into image data. Note that if the image information is not processed, the image processor 263 may be omitted.

[0040] The internal memory 265 is a storage element that temporarily stores image information that cannot be processed by the image processor 263 and processed image information. The internal memory 265 may also be configured to temporarily store image information captured by the imaging element 261. The internal memory 265 may be configured using a general memory.

[0041] The data output circuit 267 outputs the image data processed by the image processor 263 to the control unit 27. The image data output to the control unit 27 is used to detect the direction of arrival of the spatial optical signal (detection of the light direction). Note that the data output circuit 267 may be configured to output the light receiving position of the spatial optical signal in the pixel of the image sensor 261 to the control unit 27.

[0042] The control unit 27 controls the liquid crystal lens 23 so that the optical signal incident on the incident surface of the liquid crystal lens 23 is emitted toward the position (predetermined region) where the light receiving unit 250 of the light receiving element 25 is arranged. The control unit 27 performs light ray direction detection to detect the arrival direction of the spatial optical signal based on the image captured by the imaging unit 26. For example, the control unit 27 detects the arrival direction of the spatial optical signal based on the position of the spatial optical signal in the image captured by the imaging unit 26. For example, if the light receiving position of the spatial optical signal in the pixel of the imaging element 261 can be received, the light ray direction detection may be performed based on the light receiving position. The control unit 27 causes the liquid crystal lens 23 to form a lens region 230 according to the arrival direction of the spatial optical signal.

[0043] For example, the control unit 27 is configured to perform light ray direction detection at the timing when an optical signal derived from a spatial optical signal is detected from an image captured by the imaging unit 26. For example, the control unit 27 performs light ray direction detection when reception of an optical signal derived from a spatial optical signal arriving from the same arrival direction begins. For example, the control unit 27 performs light ray direction detection at the timing when the light receiving position of the optical signal on the incident surface of the liquid crystal lens 23 changes. For example, the control unit 27 performs light ray direction detection at a predetermined timing that is set in advance. The timing of light ray direction detection by the control unit 27 can be set arbitrarily. Furthermore, light ray direction detection may be performed by combining the method of scanning the emission direction of an optical signal emitted from the emission surface of the liquid crystal lens 23 as in the first embodiment with the method using the imaging unit 26 of this embodiment.

[0044] As described above, the light receiving device of this embodiment includes a condensing lens, an imaging unit, a liquid crystal lens, a control unit, and a light receiving element. The condensing lens receives a spatial optical signal. The imaging unit captures an image of the arrival direction of the spatial optical signal. The liquid crystal lens (variable lens) has a lens region formed at an arbitrary position. The liquid crystal lens focuses, in the lens region, an optical signal derived from the spatial optical signal condensed by the condensing lens. The control unit detects the arrival direction of the spatial optical signal based on the image captured by the imaging unit. The control unit causes the variable lens to form a lens region according to the detected arrival direction of the spatial optical signal. The control unit controls the emission direction of the optical signal emitted from the liquid crystal lens. The light receiving element is arranged with the light receiving unit facing the liquid crystal lens. The light receiving element receives the optical signal focused by the liquid crystal lens.

[0045] The light receiving device of this embodiment forms a lens region in the liquid crystal lens according to the direction of arrival of the spatial optical signal detected based on the image captured by the imaging unit. Therefore, according to this embodiment, the direction in which the liquid crystal lens focuses the optical signal can be optimized according to the direction of arrival of the spatial optical signal, and the light receiving efficiency of the light receiving element can be improved.

[0046] (Third embodiment) Next, a light receiving device according to a third embodiment will be described with reference to the drawings. The light receiving device of this embodiment is applied to a situation in which the direction from which the spatial optical signal arrives is somewhat limited. The light receiving device of this embodiment includes a liquid crystal lens having an elongated shape set to match the direction from which the spatial optical signal arrives. In this embodiment, the direction from which the spatial optical signal arrives is limited to the horizontal direction, and the shape of the liquid crystal lens is set to be elongated in the horizontal direction to match the direction from which the spatial optical signal arrives. The light receiving device of this embodiment may include the imaging unit of the second embodiment.

[0047] (composition) FIG. 7 is a conceptual diagram showing an example of the configuration of a light receiving device 30 of this embodiment. The light receiving device 30 includes a condenser lens 31, a liquid crystal lens 33, a light receiving element 35, and a control unit 37. FIG. 7 is a diagram showing the internal configuration of the light receiving device 30 as viewed from the side. FIG. 8 is a conceptual diagram for explaining an example of the trajectory of light received by the light receiving device 30. FIG. 8 is a perspective view of the internal configuration of the light receiving device 30 as viewed from a diagonally forward position on the incident surface side.

[0048] The condenser lens 31 is an optical element that condenses a spatial optical signal arriving from the outside. The optical signal condensed by the condenser lens 31 is condensed toward the incident surface of the liquid crystal lens 33. The condenser lens 31 has the same configuration as the condenser lens 11 of the first embodiment. The condenser lens 31 may be configured to condense light in accordance with the shape of the liquid crystal lens 33.

[0049] The liquid crystal lens 33 (also referred to as a variable lens) is disposed after the condenser lens 31. The liquid crystal lens 33 is disposed so that its incident surface faces the exit surface of the condenser lens 31. The liquid crystal lens 33 is set to have a shape that matches the arrival direction of the spatial optical signal. For example, when the spatial optical signal arrives from the horizontal direction, the liquid crystal lens 33 is set to have a shape that has a major axis in the horizontal direction and a minor axis in the vertical direction. For example, when the spatial optical signal arrives from a direction perpendicular to the horizontal plane (hereinafter referred to as the vertical direction), the liquid crystal lens 33 is set to have a shape that has a major axis in the vertical direction and a minor axis in the horizontal direction. The shape of the liquid crystal lens 33 may be set to match the arrival direction of the spatial optical signal.

[0050] A lens region 330 is formed in the liquid crystal lens 33 under the control of the control unit 37. An optical signal incident on the incident surface of the liquid crystal lens 33 is diffracted by the lens region 330 formed under the control of the control unit 37, and is emitted toward the light receiving unit 350 of the light receiving element 35. Except for its shape, the liquid crystal lens 33 has the same configuration as the liquid crystal lens 13 of the first embodiment.

[0051] The light receiving element 35 is disposed after the liquid crystal lens 33. The light receiving element 35 has a light receiving section 350 that receives the optical signal focused by the liquid crystal lens 33. The light receiving element 35 is disposed so that the light receiving section 350 faces the exit surface of the liquid crystal lens 33. The light receiving element 35 is disposed so that the light receiving section 350 is located in a predetermined area. The optical signal emitted from the liquid crystal lens 33 is received by the light receiving section 350 of the light receiving element 35 located in the predetermined area. The light receiving element 35 converts the received optical signal into an electrical signal. The light receiving element 35 outputs the converted electrical signal to a decoder (not shown). The light receiving element 35 has the same configuration as the light receiving element 15 of the first embodiment.

[0052] The control unit 37 controls the liquid crystal lens 33 so that the optical signal incident on the incident surface of the liquid crystal lens 33 is emitted toward the position (predetermined area) where the light receiving unit 350 of the light receiving element 35 is arranged. The control unit 37 causes the liquid crystal lens 33 to form a lens area 330 according to the arrival direction of the spatial optical signal. The control unit 37 has the same configuration as the control unit 17 of the first embodiment.

[0053] As described above, the light receiving device of this embodiment includes a condensing lens, a liquid crystal lens, a control unit, and a light receiving element. The condensing lens receives a spatial optical signal. The liquid crystal lens (variable lens) has a shape that matches the direction of arrival of the spatial optical signal. A lens region is formed at an arbitrary position on the liquid crystal lens. The liquid crystal lens focuses, in the lens region, an optical signal derived from the spatial optical signal focused by the condensing lens. The control unit forms the lens region at a desired position on the liquid crystal lens. The control unit controls the emission direction of the optical signal emitted from the liquid crystal lens. The light receiving element is arranged with the light receiving unit facing the liquid crystal lens. The light receiving element receives the optical signal focused by the liquid crystal lens.

[0054] According to the light receiving device of this embodiment, a liquid crystal lens having a shape that matches the direction of arrival of the spatial optical signal can be used to efficiently receive a spatial optical signal from a limited direction of arrival. For example, if the direction of arrival of the spatial optical signal from the communication target is limited to a horizontal direction, vertical direction, or the like, there is no need to receive light arriving from a direction other than these. In this embodiment, the direction of arrival of the spatial optical signal is limited to a horizontal direction, and the shape of the liquid crystal lens is elongated along the horizontal direction to match the direction of arrival. If the direction of arrival of the spatial optical signal is limited to a vertical direction, the shape of the liquid crystal lens may be elongated along the vertical direction to match the direction of arrival. Furthermore, light arriving from a direction other than the direction of arrival of the spatial optical signal from the communication target can be considered to be a noise component or a disturbance component. Therefore, according to this embodiment, the noise component or disturbance component light is not received, and therefore the spatial optical signal from the communication target can be more efficiently received.

[0055] (Fourth embodiment) Next, a light receiving device according to a fourth embodiment will be described with reference to the drawings. The light receiving device of this embodiment includes a liquid crystal lens that diffracts and reflects an optical signal collected by a collecting lens. In this embodiment, an example will be described in which an elongated liquid crystal lens is included that is set in accordance with the direction from which the spatial optical signal arrives, but the liquid crystal lens (first embodiment) that can accommodate spatial optical signals arriving from any direction may also be applied.

[0056] (composition) FIG. 9 is a conceptual diagram showing an example of the configuration of a light receiving device 40 of this embodiment. The light receiving device 40 includes a condenser lens 41, a liquid crystal lens 43, a light receiving element 45, and a control unit 47. FIG. 9 is a diagram showing the internal configuration of the light receiving device 40 as viewed from the side. FIG. 10 is a conceptual diagram for explaining an example of the trajectory of light received by the light receiving device 40. FIG. 10 is a perspective view of the internal configuration of the light receiving device 40 as viewed from a diagonally forward position on the incident surface side.

[0057] The condenser lens 41 is an optical element that condenses a spatial optical signal arriving from the outside. The optical signal condensed by the condenser lens 41 is condensed toward the incident surface of the liquid crystal lens 43. The condenser lens 41 has the same configuration as the condenser lens 11 of the first embodiment. The condenser lens 41 may be configured to condense light in accordance with the shape of the liquid crystal lens 43.

[0058] The liquid crystal lens 43 (also referred to as a variable lens) is disposed after the condenser lens 41. The liquid crystal lens 43 is a reflective diffractive optical element. The liquid crystal lens 43 has a reflective surface that diffracts and reflects light in the wavelength band of the optical signal. The reflective surface of the liquid crystal lens 43 is disposed so that the optical signal emitted from the condenser lens 41 is reflected toward the light receiving unit 450 of the light receiving element 45. For example, the liquid crystal lens 43 is realized by a spatial light modulator using a ferroelectric liquid crystal, a homogeneous liquid crystal, a vertically aligned liquid crystal, or the like. For example, the liquid crystal lens 43 is realized by an LCOS (Liquid Crystal on Silicon). For example, the liquid crystal lens 43 may be realized by a MEMS (Micro Electro Mechanical System). The refractive index of the reflective surface of the liquid crystal lens 43 changes depending on the applied voltage.

[0059] A lens region 430 is formed on the reflective surface of the liquid crystal lens 43 under the control of the control unit 47. A virtual lens pattern (hereinafter referred to as a virtual lens image) is displayed on the lens region 430 formed on the reflective surface of the liquid crystal lens 43 under the control of the control unit 47. FIG. 11 is a conceptual diagram showing an example of a virtual lens image. The virtual lens image is a lens pattern for focusing a spatial optical signal at a desired focal length. Similar to diffraction, the wavefront of light can be controlled by phase control. A spherical change in phase creates a spherical difference in the wavefront, generating a lens effect. That is, the virtual lens image is a pattern that spherically changes the phase of light (spatial optical signal) incident on the reflective surface of the liquid crystal lens 43, generating a lens effect that focuses the light at a predetermined focal length. For example, to focus an optical signal derived from a spatial optical signal on the light receiving unit 450 of the light receiving element 45, a virtual lens image that focuses the optical signal toward the light receiving unit 450 may be displayed on the reflective surface of the liquid crystal lens 43.

[0060] The liquid crystal lens 43 is formed in a shape that matches the direction from which the spatial optical signal arrives. For example, if the spatial optical signal arrives from the horizontal direction, the liquid crystal lens 43 is formed in a shape that has a major axis in the horizontal direction and a minor axis in the vertical direction. For example, if the spatial optical signal arrives from the vertical direction, the liquid crystal lens 43 is formed in a shape that has a major axis in the vertical direction and a minor axis in the horizontal direction. The shape of the liquid crystal lens 43 may be formed in accordance with the direction from which the spatial optical signal arrives. Note that there are no particular limitations on the shape of the liquid crystal lens 43 when the liquid crystal lens 43 is configured to accommodate spatial optical signals arriving from any direction.

[0061] The optical signal condensed by condensing lens 41 is incident on the reflective surface of liquid crystal lens 43, on which the virtual lens image is displayed. The optical signal incident on the reflective surface of liquid crystal lens 43 is diffracted and reflected toward a predetermined area. The emitting direction of the optical signal diffracted / reflected by the reflective surface of liquid crystal lens 43 is controlled under the control of control unit 47, and the optical signal is emitted toward light receiving unit 450 of light receiving element 45.

[0062] The light receiving element 45 is arranged after the liquid crystal lens 43. The light receiving element 45 has a light receiving unit 450 that receives the optical signal reflected by the liquid crystal lens 43. The light receiving element 45 is arranged so that the optical signal reflected by the liquid crystal lens 43 is received by the light receiving unit 450 of the light receiving element 45. The light receiving element 45 converts the received optical signal into an electrical signal. The light receiving element 45 outputs the converted electrical signal to a decoder (not shown). The light receiving element 45 has the same configuration as the light receiving element 15 of the first embodiment.

[0063] The control unit 47 controls the liquid crystal lens 43 so that the optical signal incident on the reflective surface of the liquid crystal lens 43 is reflected toward the position (predetermined region) where the light receiving unit 450 of the light receiving element 45 is arranged. The control unit 47 forms a lens region 430 on the reflective surface of the liquid crystal lens 43 according to the direction from which the spatial optical signal arrives. For example, the control unit 47 changes the refractive index of the reflective surface by changing the voltage applied to the reflective surface of the liquid crystal lens 43 so that the optical signal is reflected toward the light receiving unit 450 of the light receiving element 45. By changing the refractive index of the reflective surface, the optical signal irradiated on the reflective surface is appropriately diffracted based on the refractive index of each portion of the reflective surface.

[0064] The control unit 47 controls the liquid crystal lens 43 so that the optical signal incident on the incident surface of the liquid crystal lens 43 is emitted toward the position (predetermined region) where the light receiving unit 450 of the light receiving element 45 is arranged. For example, the control unit 47 is realized by a microcomputer including a processor and a memory. For example, the control unit 47 forms a lens region 430 at a desired position on the liquid crystal lens 43 by controlling a voltage applied to the reflective surface of the liquid crystal lens 43. The control unit 47 changes the refractive index of the lens region 430 by adjusting the voltage applied to the reflective surface of the liquid crystal lens 43. By changing the refractive index of the lens region 430, the spatial optical signal incident on the liquid crystal lens 43 is appropriately diffracted according to the refractive index of the lens region 430. In other words, the spatial optical signal incident on the liquid crystal lens 43 is diffracted according to the optical characteristics of the lens region 430. For example, the control unit 47 displays a virtual lens image on the reflective surface of the liquid crystal lens 43 to focus the spatial optical signal at a desired focal length. Note that the method of driving the liquid crystal lens 43 by the control unit 47 is not limited to the above.

[0065] [Modification] Fig. 12 is a conceptual diagram for explaining a modified example of the light receiving device 40 of this embodiment. The light receiving device of the modified example of Fig. 12 includes a reduction optical system 410. The reduction optical system 410 has a structure in which a first condenser lens 411 and a second condenser lens 412 are combined. It is preferable that the second condenser lens 412 has a higher refractive index than the first condenser lens 411. Fig. 12 shows an example in which the first condenser lens 411 and the second condenser lens 412 are combined, but the reduction optical system 410 may include three or more lenses.

[0066] The first condenser lens 411 condenses the spatial optical signal toward the second condenser lens 412. The second condenser lens 412 condenses the light condensed by the first condenser lens 411 toward the liquid crystal lens 43. The light condensed by the second condenser lens 412 (also referred to as an optical signal) is condensed by the liquid crystal lens 43 and received by the light receiving element 45.

[0067] According to this modification, the focal range of the optical signal can be made smaller than when a single condenser lens is used. Therefore, according to this modification, the size of the liquid crystal lens 43 can be made smaller. Furthermore, according to this modification, the focal length of the reduction optical system can be made shorter than when a single condenser lens is used for condensing light, so the size of the light receiving device can be made smaller.

[0068] As described above, the light receiving device of this embodiment includes a condensing lens, a liquid crystal lens, a control unit, and a light receiving element. The condensing lens receives a spatial optical signal. The liquid crystal lens (variable lens) is a reflective liquid crystal lens. A lens region is formed at an arbitrary position on the liquid crystal lens. The liquid crystal lens focuses, in the lens region, an optical signal derived from the spatial optical signal focused by the condensing lens. The control unit forms the lens region at a desired position on the liquid crystal lens by adjusting the voltage applied to the liquid crystal lens. The control unit controls the emission direction of the optical signal emitted from the liquid crystal lens. The light receiving element is arranged with the light receiving unit facing the liquid crystal lens. The light receiving element receives the optical signal focused by the liquid crystal lens.

[0069] According to the light receiving device of this embodiment, the optical signal focused by the focusing lens is reflected by the reflective liquid crystal lens so as to be guided to a predetermined area, thereby enabling efficient reception of spatial optical signals arriving from any direction. In a transmissive liquid crystal lens, the intensity of the transmitted optical signal is reduced due to the grid between the liquid crystal pixels. In contrast, a reflective liquid crystal lens does not reduce the intensity of the incident optical signal. Therefore, according to the light receiving device of this embodiment, the light receiving efficiency of the spatial optical signal can be improved compared to when a transmissive liquid crystal lens is used. Furthermore, according to the light receiving device of this embodiment, the use of a reflective liquid crystal lens bends the traveling direction of the optical signal, allowing the size of the light receiving device to be reduced compared to when a transmissive liquid crystal lens is used.

[0070] In one aspect of this embodiment, the liquid crystal lens (variable lens) is LCOS (Liquid Crystal on Silicon). The control unit displays a virtual lens image that focuses a spatial optical signal toward a light receiving portion of the light receiving element at a desired position on the LCOS display unit. According to this aspect, by displaying the virtual lens at a desired position on the LCOS display unit, the optical signal can be efficiently focused on the light receiving portion of the light receiving element.

[0071] The light receiving device according to one aspect of the present embodiment includes a reduction optical system that combines multiple condenser lenses. For example, when an LCOS is used as the liquid crystal lens, it is necessary to reduce the light-collecting area to match the size of the LCOS. According to this aspect, the focal length can be shortened by combining multiple condenser lenses, so that even a liquid crystal lens with a small light-receiving surface can receive an optical signal based on a spatial optical signal arriving from any direction.

[0072] (Fifth embodiment) Next, a receiving device according to a fifth embodiment will be described with reference to the drawings. The receiving device of this embodiment includes a decoder that decodes an optical signal received by a light receiving element. In this embodiment, an example including a long and narrow liquid crystal lens set in accordance with the direction of arrival of the spatial optical signal will be described, but a liquid crystal lens that can accommodate spatial optical signals arriving from any direction may also be applied. A reflective liquid crystal lens such as that of the fourth embodiment may also be applied to the receiving device of this embodiment. The receiving device of this embodiment may also include the imaging unit of the second embodiment.

[0073] (composition) FIG. 13 is a conceptual diagram showing an example of the configuration of a receiving device 50 of this embodiment. The receiving device 50 includes a condenser lens 51, a liquid crystal lens 53, a light receiving element 55, a decoder 56, and a control unit 57. FIG. 13 is a diagram showing the internal configuration of the receiving device 50 as viewed from the side. FIG. 14 is a conceptual diagram for explaining an example of the trajectory of light received by the receiving device 50. FIG. 14 is a perspective view of the internal configuration of the receiving device 50 as viewed from a position diagonally forward on the incident surface side. Note that there is no particular limitation on the position of the decoder 56. The decoder 56 may be arranged inside the receiving device 50 or outside the receiving device 50.

[0074] The condenser lens 51 is an optical element that condenses a spatial optical signal arriving from the outside. The optical signal condensed by the condenser lens 51 is condensed toward the incident surface of the liquid crystal lens 53. The condenser lens 51 has the same configuration as the condenser lens 11 of the first embodiment. The condenser lens 51 may be configured to condense the optical signal in accordance with the shape of the liquid crystal lens 53.

[0075] The liquid crystal lens 53 (also referred to as a variable lens) is disposed after the condenser lens 51. The liquid crystal lens 53 is disposed so that its incident surface faces the exit surface of the condenser lens 51. For example, the liquid crystal lens 53 is set to a shape that matches the direction of arrival of the spatial optical signal, as in the third embodiment. Note that the liquid crystal lens 53 may be configured to accommodate spatial optical signals arriving from any direction, as in the first embodiment. The optical signal incident on the incident surface of the liquid crystal lens 53 is focused by a lens region 530 formed under the control of the control unit 57, and is emitted toward the light receiving unit 550 of the light receiving element 55. The liquid crystal lens 53 has a configuration similar to that of the liquid crystal lens 33 of the third embodiment. The liquid crystal lens 53 may be a reflective type, as in the fourth embodiment. Since the liquid crystal lens 53 is similar to any of the first to fourth embodiments, a detailed description thereof will be omitted.

[0076] The light receiving element 55 is arranged after the liquid crystal lens 53. The light receiving element 55 has a light receiving unit 550 that receives the optical signal focused by the liquid crystal lens 53. The light receiving element 55 is arranged so that the light receiving unit 550 faces the exit surface of the liquid crystal lens 53. The light receiving element 55 is arranged so that the light receiving unit 550 is located in a predetermined area. The optical signal emitted from the liquid crystal lens 53 is received by the light receiving unit 550 of the light receiving element 55 located in the predetermined area. The light receiving element 55 converts the received optical signal into an electrical signal. The light receiving element 55 outputs the converted electrical signal to the decoder 56. The light receiving element 55 has the same configuration as the light receiving element 15 of the first embodiment.

[0077] The decoder 56 acquires the signal output from the light receiving element 55. The decoder 56 amplifies the signal from the light receiving element 55. The decoder 56 decodes the amplified signal and analyzes the signal from the communication target. The signal decoded by the decoder 56 is used for any purpose. There are no particular limitations on the use of the signal decoded by the decoder 56.

[0078] The control unit 57 controls the liquid crystal lens 53 so that the optical signal incident on the incident surface of the liquid crystal lens 53 is emitted toward the position (predetermined area) where the light receiving unit 550 of the light receiving element 55 is arranged. The control unit 57 causes the liquid crystal lens 53 to form a lens area 530 according to the arrival direction of the spatial optical signal. The control unit 57 has the same configuration as the control unit 17 of the first embodiment.

[0079] 〔decoder〕 Next, an example of a detailed configuration of the decoder 56 included in the receiving device 50 will be described with reference to the drawings. Fig. 15 is a block diagram showing an example of the configuration of the decoder 56. The decoder 56 has a first processing circuit 561 and a second processing circuit 565.

[0080] The first processing circuit 561 acquires a signal from the light receiving element 55. The first processing circuit 561 amplifies the selected signal. The first processing circuit 561 may selectively pass a signal in the wavelength band of the spatial optical signal. For example, the first processing circuit 561 may cut signals derived from ambient light such as sunlight from the acquired signals and selectively pass signals of high-frequency components corresponding to the wavelength band of the spatial optical signal. The first processing circuit 561 outputs the amplified signal to the second processing circuit 565.

[0081] The second processing circuit 565 acquires a signal from the first processing circuit 561. The second processing circuit 565 decodes the acquired signal. The second processing circuit 565 may be configured to perform some kind of signal processing on the decoded signal, or may be configured to output the signal to an external signal processing device or the like (not shown). When decoding multiple signals derived from spatial light from multiple communication targets, the second processing circuit may be configured to read these signals in a time-division manner.

[0082] As described above, the receiving device of this embodiment includes a condensing lens, a liquid crystal lens, a control unit, a light receiving element, and a decoder. The condensing lens receives a spatial optical signal. The liquid crystal lens (variable lens) has a lens area formed at an arbitrary position. The liquid crystal lens focuses, in the lens area, an optical signal derived from the spatial optical signal focused by the condensing lens. The control unit forms the lens area at a desired position on the liquid crystal lens. The control unit controls the emission direction of the optical signal emitted from the liquid crystal lens. The light receiving element is disposed with the light receiving unit facing the liquid crystal lens. The light receiving element receives the optical signal focused by the liquid crystal lens. The decoder decodes a signal based on the optical signal received by the light receiving element.

[0083] The receiving device of this embodiment can decode a signal based on a spatial optical signal arriving from any direction. For example, the receiving device of this embodiment can realize a single-channel receiving device. For example, the receiving device of this embodiment can realize a multi-channel receiving device by decoding a signal based on a spatial optical signal in a time-division manner.

[0084] (Sixth embodiment) Next, a receiving device according to a sixth embodiment will be described with reference to the drawings. The receiving device of this embodiment includes a plurality of decoders that decode optical signals received by light receiving elements. In this embodiment, an example will be described in which an elongated liquid crystal lens is included that is set in accordance with the direction of arrival of the spatial optical signal, but a liquid crystal lens that can accommodate spatial optical signals arriving from any direction may also be applied. A reflective liquid crystal lens such as that of the fourth embodiment may also be applied to the receiving device of this embodiment. The receiving device of this embodiment may also include the imaging unit of the second embodiment.

[0085] (composition) FIG. 16 is a conceptual diagram showing an example of the configuration of a receiving device 60 of this embodiment. The receiving device 60 includes a condenser lens 61, a liquid crystal lens 63, a plurality of light receiving elements 65-1 to 65-M, a decoder 66, and a control unit 67 (M is a natural number equal to or greater than 2). FIG. 16 is a plan view of the internal configuration of the receiving device 60 as viewed from above. FIG. 17 is a conceptual diagram for explaining an example of the trajectory of light received by the receiving device 60. FIG. 17 is a perspective view of the internal configuration of the receiving device 60 as viewed from a vantage point diagonally forward from the incident surface side. Note that there is no particular limitation on the position of the decoder 66. The decoder 66 may be disposed inside the receiving device 60 or outside the receiving device 60.

[0086] The condenser lens 61 is an optical element that condenses a spatial optical signal arriving from the outside. The optical signal condensed by the condenser lens 61 is condensed toward the incident surface of the liquid crystal lens 63. The condenser lens 61 has the same configuration as the condenser lens 11 of the first embodiment. The condenser lens 61 may be configured to condense light in accordance with the shape of the liquid crystal lens 63.

[0087] The liquid crystal lens 63 (also called a variable lens) is disposed after the condenser lens 61. The liquid crystal lens 63 is disposed so that its incident surface faces the exit surface of the condenser lens 61. The liquid crystal lens 63 has the same configuration as the liquid crystal lens 33 of the third embodiment. For example, the liquid crystal lens 63 is set to have a shape that matches the direction from which the spatial optical signal arrives, as in the third embodiment. Note that the liquid crystal lens 63 may be configured to accommodate spatial optical signals arriving from any direction, as in the first embodiment.

[0088] An optical signal condensed by the condensing lens 61 is incident on the incident surface of the liquid crystal lens 63. A plurality of light beam control areas 630-1 to 630-M are set in the liquid crystal lens 63. Each of the plurality of light beam control areas 630-1 to 630-M set in the liquid crystal lens 63 corresponds to a respective one of a plurality of light receiving elements 65-1 to 65-M. A lens area 635 is formed in each of the plurality of light beam control areas 630-1 to 630-M according to the control of the control unit 67. The optical signal incident on each of the plurality of light beam control areas 630-1 to 630-M is diffracted by the lens area 635 formed in the respective light beam control areas 630. The optical signal diffracted by the lens area 635 formed in each light beam control area 630 is focused toward a predetermined area where the light receiving unit 650 of the light receiving element 65-1 to 65-M corresponding to each light beam control area 630 is arranged. 。 figure In the example of FIG. 17, spatial optical signal A and spatial optical signal B arriving from different directions are incident on a condenser lens 61. Optical signals derived from spatial optical signal A and spatial optical signal B are condensed by the condenser lens 61 and incident on different light beam control regions 630 of a liquid crystal lens 63. The optical signals incident on the incident surface of the liquid crystal lens 63 are condensed by lens regions 635 formed in different light beam control regions 630 under the control of a control unit 67, and are emitted toward a light receiving unit 650 of a light receiving element 65. As a result, the optical signal derived from spatial optical signal A and the optical signal derived from spatial optical signal B are received by different light receiving elements 65.

[0089] 18 shows a configuration in which the reflective liquid crystal lens 43 of the fourth embodiment is disposed in place of the liquid crystal lens 63 of this embodiment. In the example of FIG. 18, an optical signal derived from a spatial optical signal is collected by a collecting lens 61 and made incident on a light beam control region on the reflecting surface of the liquid crystal lens 43. The optical signal incident on the incident surface of the liquid crystal lens 43 is collected by a lens region 430 formed under the control of a control unit 67 and is emitted toward a light receiving unit 650 of a light receiving element 65. As a result, the optical signal derived from the spatial optical signal is received by the light receiving element 65 associated with the light beam control element.

[0090] The plurality of light receiving elements 65-1 to 65-M are arranged after the liquid crystal lens 63. Each of the plurality of light receiving elements 65-1 to 65-M has a light receiving unit 650 that receives an optical signal emitted from the liquid crystal lens 63. The plurality of light receiving elements 65-1 to 65-M are arranged so that the light receiving unit 650 faces the emission surface of the liquid crystal lens 63. The light receiving unit 650 of each of the plurality of light receiving elements 65-1 to 65-M is arranged so that it faces each of the plurality of light beam control regions 630-1 to 630-M. The optical signal emitted from each of the plurality of light beam control regions 630-1 to 630-M is received by the light receiving unit 650 of each of the plurality of light receiving elements 65-1 to 65-M. Each of the plurality of light receiving elements 65-1 to 65-M converts the received optical signal into an electrical signal (hereinafter also referred to as a signal). Each of the plurality of light receiving elements 65-1 to 65-M outputs the converted signal to the decoder 66. Each of the plurality of light receiving elements 65-1 to 65-M has the same configuration as the light receiving element 15 of the first embodiment.

[0091] The decoder 66 acquires signals output from each of the multiple light-receiving elements 65-1 to 65-M. The decoder 66 amplifies the signals from each of the multiple light-receiving elements 65-1 to 65-M. The decoder 66 decodes the amplified signals and analyzes the signals from the communication target. For example, the decoder 66 analyzes the signals from each of the multiple light-receiving elements 65-1 to 65-M collectively. When the signals from each of the multiple light-receiving elements 65-1 to 65-M are analyzed collectively, a single-channel receiving device 60 that communicates with a single communication target can be realized. For example, the decoder 66 analyzes the signals from each of the multiple light-receiving elements 65-1 to 65-M individually. When the signals from each of the multiple light-receiving elements 65-1 to 65-M are analyzed individually, a multi-channel receiving device 60 that communicates with multiple communication targets simultaneously can be realized. The signals decoded by the decoder 66 can be used for any purpose. There are no particular limitations on the use of the signals decoded by the decoder 66.

[0092] 〔decoder〕 Next, an example of the detailed configuration of the decoder 66 included in the receiving device 60 will be described with reference to the drawings. Fig. 19 is a block diagram showing an example of the configuration of the decoder 66. The decoder 66 has a plurality of first processing circuits 661-1 to 661-M, a control circuit 662, a selector 663, and a plurality of second processing circuits 665-1 to 665-N (M and N are natural numbers). Fig. 19 shows the internal configuration of only the first processing circuit 661-1 out of the plurality of first processing circuits 661-1 to 661-M, but the internal configurations of the plurality of first processing circuits 661-2 to 661-M are the same as that of the first processing circuit 661-1.

[0093] First processing circuit 661 is associated with any one of the plurality of light receiving elements 65-1 to 65-M. First processing circuit 661 includes a high-pass filter 6611, an amplifier 6613, and an integrator 6615. Figure 19In the figure, the high-pass filter 6611 is referred to as an HPF (High Pass Filter), the amplifier 6613 is referred to as an AMP (Amplifier), and the integrator 6615 is referred to as an INT (Integrator). The high-pass filter 6611 of each of the plurality of first processing circuits 661-1 to 661-M acquires a signal from one of the light receiving elements 65-1 to 65-M associated with the plurality of first processing circuits 661-1 to 661-M. Each of the plurality of light receiving elements 65-1 to 65-M and each of the plurality of first processing circuits 661-1 to 661-M corresponding thereto constitute a unit. The signal that has passed through the high-pass filter 6611 of each of the plurality of first processing circuits 661-1 to 661-M is input in parallel to the amplifier 6613 and the integrator 6615.

[0094] The high-pass filter 6611 acquires a signal from the light receiving element 65. The high-pass filter 6611 selectively passes high-frequency components of the acquired signal that correspond to the wavelength band of the spatial light signal. The high-pass filter 6611 cuts off signals derived from ambient light such as sunlight. Note that instead of the high-pass filter 6611, a band-pass filter that selectively passes signals in the wavelength band of the spatial light signal may be configured. Furthermore, if the light receiving element 65 becomes saturated with intense sunlight, the optical signal becomes unreadable. For this reason, a color filter that selectively passes light in the wavelength band of the spatial light signal may be installed before the light receiving section of the light receiving element 65. The signal that has passed through the high-pass filter 6611 is supplied to the amplifier 6613 and the integrator 6615.

[0095] The amplifier 6613 acquires the signal output from the high-pass filter 6611. The amplifier 6613 amplifies the acquired signal. The amplifier 6613 outputs the amplified signal to the selector 663. Of the signals output to the selector 663, signals to be received are assigned to one of the multiple second processing circuits 665-1 to 665-N under the control of the control circuit 662. The signals to be received are spatial optical signals from a communication device (not shown) that is the communication target. Signals from the light receiving elements 65 that are not used to receive the spatial optical signals are not output to the second processing circuit 665.

[0096] The integrator 6615 acquires the signal output from the high-pass filter 6611. The integrator 6615 integrates the acquired signal. The integrator 6615 outputs the integrated signal to the control circuit 662. The integrator 6615 is arranged to measure the intensity of the spatial optical signal received by the light receiving element 65. In this embodiment, the spatial optical signal with a widened beam diameter is received on the incident surface of the condenser lens 61, thereby increasing the speed of searching for a communication target. Since the spatial optical signal received with an unfocused beam diameter has a weaker intensity than when the beam diameter is focused, it is difficult to measure the voltage of the signal amplified by only the amplifier 6613. By using the integrator 6615, for example, by integrating for several msec (milliseconds) to several tens of msec, the voltage of the signal can be increased to a level at which the voltage can be measured.

[0097] The control circuit 662 acquires a signal output from the integrator 6615 included in each of the multiple first processing circuits 661-1 to 661-M. In other words, the control circuit 662 acquires a signal derived from an optical signal received by each of the multiple light receiving elements 65-1 to 65-M. For example, the control circuit 662 compares the read values ​​of the signals from multiple adjacent light receiving elements 65. Based on the comparison result, the control circuit 662 selects the light receiving element 65 with the greatest signal strength. The control circuit 662 controls the selector 663 to assign the signal derived from the selected light receiving element 65 to one of the multiple second processing circuits 665-1 to 665-N.

[0098] The control circuit 662 selecting the light receiving element 65 corresponds to estimating the direction of arrival of the spatial optical signal. In other words, the control circuit 662 selecting the light receiving element 65 corresponds to identifying the communication device that is the source of the spatial optical signal. Furthermore, the control circuit 662 assigning the signal from the light receiving element 65 selected by the control circuit 662 to one of the plurality of second processing circuits corresponds to associating the identified communication target with the light receiving element 65 that receives the spatial optical signal from that communication target. In other words, the control circuit 662 identifies the communication device that is the source of the optical signal (spatial optical signal) based on the optical signal received by the plurality of light receiving elements 650-1 to 650-M. Note that if the position of the communication target is identified in advance, the signal output from the light receiving elements 65-1 to 65-M may be decoded as is without performing the process of estimating the direction of arrival of the spatial optical signal.

[0099] The selector 663 receives signals amplified by the amplifiers 6613 included in each of the plurality of first processing circuits 661-1 to 661-M. The selector 663 outputs signals to be received from the input signals to one of the plurality of second processing circuits 665-1 to 665-N in accordance with the control of the control circuit 662. Signals not to be received are not output from the selector 663.

[0100] The second processing circuits 665-1 to 665-N receive signals from any of the light receiving elements 65-1 to 65-N assigned by the control circuit 662. Each of the second processing circuits 665-1 to 665-N decodes the input signal. Each of the second processing circuits 665-1 to 665-N may be configured to perform some kind of signal processing on the decoded signal, or may be configured to output the decoded signal to an external signal processing device or the like (not shown).

[0101] The selector 663 selects a signal originating from the light-receiving element 65 selected by the control circuit 662, thereby allocating one second processing circuit 665 to one communication target. That is, the control circuit 662 allocates signals originating from spatial optical signals from multiple communication targets, received by the multiple light-receiving elements 65-1 to 65-M, to one of the multiple second processing circuits 665-1 to 665-N. This enables the receiving device 60 to simultaneously read signals originating from spatial optical signals from multiple communication targets in individual channels. In the case of the fifth embodiment, in order to simultaneously communicate with multiple communication targets, the spatial optical signals from the multiple communication targets are read in a single channel in a time-division manner. In contrast, in the method of this embodiment, the spatial optical signals from multiple communication targets are read simultaneously in multiple channels, thereby improving the transmission speed. Note that the method of this embodiment may also be configured to receive signals in a time-division manner depending on the situation.

[0102] For example, a primary scan of the communication target may be performed to roughly identify the direction of arrival of the spatial optical signal. A secondary scan with finer accuracy may then be performed in the identified direction to more accurately identify the position of the communication target. Once communication with the communication target is possible, the exact position of the communication target can be determined by exchanging signals with the communication target. Note that if the position of the communication target has been identified in advance, the process of identifying the position of the communication target may be omitted.

[0103] As described above, the receiving device of this embodiment includes a condensing lens, a liquid crystal lens, a control unit, multiple light receiving elements, and multiple decoders. The condensing lens condenses a spatial optical signal. The liquid crystal lens (variable lens) includes multiple light beam control regions corresponding to multiple predetermined regions. A lens region is formed at an arbitrary position in each of the multiple light beam control regions. An optical signal derived from the spatial optical signal condensed by the condensing lens is incident on each of the multiple light beam control regions. The liquid crystal lens emits the optical signal incident on each of the multiple light beam control regions toward the predetermined region corresponding to the light beam control region. Each of the multiple light receiving elements is arranged with its light receiving unit facing one of the multiple predetermined regions. Each of the multiple light receiving elements receives the optical signal condensed by the lens region formed in the corresponding light beam control region. The control unit forms a lens region at a desired position in each of the multiple light beam control regions included in the liquid crystal lens. The control unit controls the emission direction of the optical signal emitted from the multiple light beam control regions included in the liquid crystal lens. Each of the multiple decoders is connected to one of the multiple light receiving elements. The decoder decodes a signal based on the optical signal received by each of the plurality of light receiving elements.

[0104] According to the receiving device of this embodiment, signals based on spatial optical signals arriving from any direction can be decoded for each direction of arrival. For example, according to the receiving device of this embodiment, a multi-channel receiving device according to the directions of arrival of spatial optical signals can be realized.

[0105] (Seventh embodiment) Next, a communication device according to a seventh embodiment will be described with reference to the drawings. The communication device according to this embodiment includes the receiving device according to the fifth embodiment and a light transmitting unit that transmits a spatial light signal corresponding to a received spatial light signal. An example of a communication device including a light transmitting unit that includes a phase modulation spatial light modulator will be described below. Note that the communication device according to this embodiment may also include a light transmitting unit that includes a light transmitting function other than a phase modulation spatial light modulator. The communication device according to this embodiment may also have a wireless communication function. The communication device according to this embodiment may also be configured by combining the light receiving device according to the sixth embodiment and a light transmitting unit. A reflective liquid crystal lens as in the fourth embodiment may be applied to the light receiving device according to this embodiment. The light receiving device according to this embodiment may also include the imaging unit according to the second embodiment.

[0106] (composition) FIG. 20 is a conceptual diagram showing an example of the configuration of a communication device 70 of this embodiment. The communication device 70 includes a condenser lens 71, a liquid crystal lens 73, a light receiving element 75, a decoder 76, a control unit 77, and a light transmitting unit 78. FIG. 20 is a diagram showing the internal configuration of the communication device 70 as viewed from the side. Note that there are no particular limitations on the positions of the decoder 76 and the light transmitting unit 78. The decoder 76 and the light transmitting unit 78 may be disposed inside the communication device 70 or outside the communication device 70.

[0107] The condenser lens 71 is an optical element that condenses a spatial optical signal arriving from the outside. The optical signal condensed by the condenser lens 71 is condensed toward the incident surface of the liquid crystal lens 73. The condenser lens 71 has the same configuration as the condenser lens 11 of the first embodiment. The condenser lens 71 may be configured to condense light in accordance with the shape of the liquid crystal lens 73.

[0108] The liquid crystal lens 73 (also referred to as a variable lens) is disposed after the condenser lens 71. The liquid crystal lens 73 is disposed so that its incident surface faces the exit surface of the condenser lens 71. For example, the liquid crystal lens 73 is shaped to match the direction of arrival of the spatial optical signal, as in the third embodiment. Note that the liquid crystal lens 73 may be configured to accommodate spatial optical signals arriving from any direction, as in the first embodiment. The optical signal incident on the incident surface of the liquid crystal lens 73 is focused by a lens region 730 formed under the control of the control unit 77, and is emitted toward the light receiving unit 750 of the light receiving element 75. The liquid crystal lens 73 has a configuration similar to that of the liquid crystal lens 33 of the third embodiment. The liquid crystal lens 73 may be a reflective type, as in the fourth embodiment. Furthermore, the liquid crystal lens 73 may include a plurality of light beam control regions, as in the sixth embodiment. The liquid crystal lens 73 is similar to any of the first to sixth embodiments, and therefore a detailed description thereof will be omitted.

[0109] The light receiving element 75 is arranged after the liquid crystal lens 73. The light receiving element 75 has a light receiving unit 750 that receives the optical signal emitted from the liquid crystal lens 73. The light receiving element 75 is arranged so that the light receiving unit 750 faces the emission surface of the liquid crystal lens 73. The optical signal emitted from the liquid crystal lens 73 is received by the light receiving unit 750 of the light receiving element 75. The light receiving element 75 converts the received optical signal into an electrical signal (hereinafter also referred to as a signal). The light receiving element 75 outputs the converted signal to a decoder 76. The light receiving element 75 has the same configuration as the light receiving element 15 of the first embodiment. Note that, as in the sixth embodiment, multiple light receiving elements 75 may be arranged.

[0110] The decoder 76 acquires the signal output from the light receiving element 75. The decoder 76 amplifies the signal from the light receiving element 75. The decoder 76 decodes the amplified signal and analyzes the signal from the communication target. The decoder 76 outputs a control signal to the light transmitting unit 78 for transmitting an optical signal according to the signal analysis result.

[0111] The control unit 77 controls the liquid crystal lens 73 so that the optical signal incident on the incident surface of the liquid crystal lens 73 is emitted toward the position (predetermined area) where the light receiving unit 750 of the light receiving element 75 is arranged. The control unit 77 causes the liquid crystal lens 73 to form a lens area 730 according to the arrival direction of the spatial optical signal. The control unit 77 has the same configuration as the control unit 17 of the first embodiment.

[0112] The light transmitting unit 78 acquires a control signal from the decoder 76. The light transmitting unit 78 projects a spatial light signal in accordance with the control signal. The spatial light signal projected from the light transmitting unit 78 is received by a communication target (not shown). For example, the light transmitting unit 78 includes a phase modulation type spatial light modulator. Alternatively, the light transmitting unit 78 may include a light transmitting function other than a phase modulation type spatial light modulator.

[0113] [Light transmitting unit] Next, an example of a detailed configuration of the light sending unit 78 will be described with reference to the drawings. Fig. 21 is a conceptual diagram showing an example of a detailed configuration of the light sending unit 78. The light sending unit 78 includes an irradiation unit 781, a spatial light modulator 783, a projection control unit 785, and a projection optical system 787. The irradiation unit 781, the spatial light modulator 783, and the projection optical system 787 constitute a light projecting unit 700. The light projecting unit 700 projects a spatial light signal in accordance with the control of the projection control unit 785. Note that Fig. 21 is conceptual and does not accurately represent the positional relationship between the components or the traveling direction of light.

[0114] The irradiation unit 781 emits coherent light 702 of a specific wavelength. As shown in FIG. 21 , the irradiation unit 781 includes a light source 7811 and a collimating lens 7812. As shown in FIG. 21 , the light 701 emitted by the irradiation unit 781 passes through the collimating lens 7812 to become coherent light 702, and is then incident on a modulation unit 7830 of the spatial light modulator 783. For example, the light source 7811 includes a laser light source. For example, the light source 7811 is configured to emit light 701 in the infrared region. Note that the light source 7811 may also be configured to emit light 701 in a region other than the infrared region, such as the visible region or the ultraviolet region. The irradiation unit 781 is connected to a power source (also referred to as a light source driving power source) that is driven under the control of the projection control unit 785. When the light source driving power source is driven, the light source 7811 emits light 701.

[0115] The spatial light modulator 783 sets a pattern for projecting a spatial light signal (a phase distribution corresponding to the spatial light signal) in its own modulation section 7830 in accordance with the control of the projection control section 785. In this embodiment, with a predetermined pattern displayed on the modulation section 7830 of the spatial light modulator 783, the modulation section 7830 is irradiated with light 702. The spatial light modulator 783 emits reflected light (modulated light 703) of the light 702 incident on the modulation section 7830 toward the projection optical system 787.

[0116] 21, the angle of incidence of light 702 is made non-perpendicular to the incident surface of the modulation unit 7830 of the spatial light modulator 783. That is, in the example of Fig. 21, the emission axis of light 702 from the irradiation unit 781 is made oblique to the modulation unit 7830 of the spatial light modulator 783, and the light 702 is made incident on the modulation unit 7830 of the spatial light modulator 783 without using a beam splitter. In the configuration of Fig. 21, the light 702 is not attenuated by passing through a beam splitter, and therefore the utilization efficiency of the light 702 can be improved.

[0117] The spatial light modulator 783 can be realized by a phase modulation type spatial light modulator that receives coherent light 702 with a uniform phase and modulates the phase of the incident light 702. The light emitted from the projection optical system 787 using the phase modulation type spatial light modulator 783 is focus-free, so even if light is projected at a plurality of projection distances, it is not necessary to change the focus for each projection distance.

[0118] A phase distribution corresponding to the spatial light signal is displayed on a modulation section 7830 of the phase modulation type spatial light modulator 783 in response to driving by a projection control section 785. The modulated light 703 reflected by the modulation section 7830 of the spatial light modulator 783 on which the phase distribution is displayed becomes an image like an assembly of a kind of diffraction grating, and an image is formed as if light diffracted by the diffraction grating is gathered.

[0119] The spatial light modulator 783 is realized by a spatial light modulator using, for example, ferroelectric liquid crystal, homogeneous liquid crystal, vertically aligned liquid crystal, or the like. Specifically, the spatial light modulator 783 can be realized by LCOS (Liquid Crystal on Silicon). For example, the spatial light modulator 783 may be realized by a MEMS (Micro Electro Mechanical System). The phase modulation type spatial light modulator 783 can concentrate energy on the image portion by operating to sequentially switch the location where the projection light is projected. Therefore, if the phase modulation type spatial light modulator 783 is used, it is possible to display information brighter than other types of modulators with the same light source output.

[0120] The projection control unit 785 causes a modulation unit 7830 of the spatial light modulator 783 to display a pattern corresponding to the spatial light signal in response to a control signal from the decoder 76. The projection control unit 785 drives the spatial light modulator 783 so as to change a parameter that determines the difference between the phase of the light 701 irradiated to the modulation unit 7830 of the spatial light modulator 783 and the phase of the modulated light 703 reflected by the modulation unit 7830.

[0121] The parameters that determine the difference between the phase of the light 702 irradiated onto the modulation section 7830 of the phase-modulation spatial light modulator 783 and the phase of the modulated light 703 reflected by the modulation section 7830 are, for example, parameters related to optical characteristics such as refractive index and optical path length. For example, the projection control section 785 changes the refractive index of the modulation section 7830 by changing the voltage applied to the modulation section 7830 of the spatial light modulator 783. By changing the refractive index of the modulation section 7830, the light 702 irradiated onto the modulation section 7830 is appropriately diffracted based on the refractive index of each section of the modulation section 7830. In other words, the phase distribution of the light 702 irradiated onto the phase-modulation spatial light modulator 783 is modulated in accordance with the optical characteristics of the modulation section 7830. Note that the method of driving the spatial light modulator 783 by the projection control section 785 is not limited to the above.

[0122] The projection optical system 787 projects the modulated light 703 modulated by the spatial light modulator 783 as projection light 707 (also referred to as a spatial light signal). As shown in FIG. 24 , the projection optical system 787 includes a Fourier transform lens 7871, an aperture 7873, and a projection lens 7875. The modulated light 703 modulated by the spatial light modulator 783 is irradiated as projection light 707 by the projection optical system 787. Note that any of the components of the projection optical system 787 may be omitted as long as an image can be formed within the projection range. For example, if an image corresponding to the phase distribution set in the modulation unit 7830 of the spatial light modulator 783 is enlarged using a virtual lens, the Fourier transform lens 7871 can be omitted. Furthermore, components other than the Fourier transform lens 7871, the aperture 7873, and the projection lens 7875 may be added to the projection optical system 787 as necessary.

[0123] The Fourier transform lens 7871 is an optical lens for focusing an image formed when the modulated light 703 reflected by the modulation unit 7830 of the spatial light modulator 783 is projected to infinity at a nearby focal point. In Fig. 24, the focal point is formed at the position of the aperture 7873.

[0124] Aperture 7873 blocks higher-order light contained in the light focused by Fourier transform lens 7871 and specifies the area in which projected light 707 is displayed. The opening of aperture 7873 is smaller than the outermost periphery of the display area at the position of aperture 7873, and is installed so as to block the peripheral area of ​​the displayed information at the position of aperture 7873. For example, the opening of aperture 7873 is formed in a rectangular or circular shape. Although aperture 7873 is preferably installed at the focal position of Fourier transform lens 7871, it may be located away from the focal position as long as it can perform the function of eliminating higher-order light.

[0125] The projection lens 7875 is an optical lens that magnifies and projects the light focused by the Fourier transform lens 7871. The projection lens 7875 projects the projection light 707 so that display information corresponding to the phase distribution displayed on the modulation unit 7830 of the spatial light modulator 783 is projected within the projection range. When projecting a line drawing such as a simple symbol, the projection light 707 projected from the projection optical system 787 is not projected uniformly over the entire projection range, but is instead concentrated on parts such as characters, symbols, and frames that make up the image. Therefore, according to the communication device 70 of this embodiment, the amount of light 701 emitted can be substantially reduced, thereby suppressing the overall light output. In other words, the communication device 70 can be implemented with a small, low-power irradiation unit 781, and therefore the output of a light source driving power supply (not shown) that drives the irradiation unit 781 can be reduced, thereby reducing overall power consumption.

[0126] Furthermore, if the irradiation unit 781 is configured to emit light of multiple wavelengths, it is possible to change the wavelength of the light emitted from the irradiation unit 781. Changing the wavelength of the light emitted from the irradiation unit 781 makes it possible to multicolor the color of the spatial optical signal. Furthermore, if the irradiation unit 781 is used that simultaneously emits light of different wavelengths, communication using spatial optical signals of multiple colors becomes possible.

[0127] [Application example] 22 is a conceptual diagram for explaining an application example of the communication device 70 of this embodiment. In this application example, the communication device 70 is placed on the top of a utility pole. In this application example, the communication device 70 has a function of wireless communication.

[0128] There are few obstacles at the top of utility poles. Therefore, the top of utility poles is suitable for installing communication devices 70. Furthermore, if the communication devices 70 are installed at the same height at the top of utility poles, the direction of arrival of the spatial optical signals is limited to the horizontal direction, and the liquid crystal lens can be made horizontally elongated as in the third to seventh embodiments. A pair of communication devices 70 exchanging communications is arranged so that at least one communication device 70 receives the spatial optical signal transmitted from the other communication device 70. The pair of communication devices 70 may be arranged so that they transmit and receive spatial optical signals to each other. When a communication network for spatial optical signals is formed by multiple communication devices 70, an intermediate communication device 70 may be arranged so that the spatial optical signal transmitted from another communication device 70 is relayed to another communication device 70.

[0129] According to this application example, communication using spatial optical signals becomes possible between a plurality of communication devices 70 installed on different utility poles. For example, according to this application example, in response to communication between the communication devices 70 installed on different utility poles, communication by wireless communication can be performed between the communication device 70 and a wireless device installed in a car, a house, or the like.

[0130] As described above, the communication device of this embodiment includes a condensing lens, a liquid crystal lens, a control unit, a light receiving element, a decoder, and a light transmitting unit. The condensing lens receives a spatial optical signal. The liquid crystal lens (variable lens) has a lens region formed at an arbitrary position. The liquid crystal lens focuses, in the lens region, an optical signal derived from the spatial optical signal focused by the condensing lens. The control unit forms the lens region at a desired position on the liquid crystal lens. The control unit controls the emission direction of the optical signal emitted from the liquid crystal lens. The light receiving element is disposed with the light receiving unit facing the liquid crystal lens. The light receiving element receives the optical signal focused by the liquid crystal lens. The decoder decodes a signal based on the optical signal received by the light receiving element. The light transmitting unit transmits a spatial optical signal corresponding to the signal decoded by the decoder.

[0131] The communication device of this embodiment enables communication using spatial optical signals. For example, if a plurality of communication devices are arranged so as to be able to transmit and receive spatial optical signals, a communication network using spatial optical signals can be constructed.

[0132] In one aspect of this embodiment, the light sending unit includes a light source, a spatial light modulator, a control unit, and a projection optical system. The light source emits parallel light. The spatial light modulator includes a modulation unit that modulates the phase of the parallel light emitted from the light source. The control unit sets a phase image corresponding to the spatial light signal in the modulation unit and controls the light source so that the parallel light is irradiated toward the modulation unit on which the phase image is set. The projection optical system projects the light modulated by the modulation unit. Because the communication device of this aspect includes a phase-modulation spatial light modulator, it can send spatial light signals of the same brightness with lower power consumption than communication devices including a general light sending mechanism.

[0133] (Eighth embodiment) Next, a light receiving device according to an eighth embodiment will be described with reference to the drawings. The light receiving device of this embodiment has a configuration in which the light receiving function of the first to seventh embodiments is simplified. FIG. 23 is a conceptual diagram showing an example of the configuration of a light receiving device 80 of this embodiment. The light receiving device 80 includes a condenser lens 81, a variable lens 83, a light receiving element 85, and a control unit 87.

[0134] The condensing lens 81 condenses the spatial optical signal. The variable lens 83 has a lens region 830 formed at an arbitrary position. The variable lens 83 focuses, in the lens region 830, an optical signal derived from the spatial optical signal condensed by the condensing lens 81. The control unit 87 forms the lens region 830 at a desired position on the variable lens 83. The control unit 87 controls the emission direction of the optical signal emitted from the variable lens 83. The light receiving element 85 is arranged with the light receiving unit 850 facing the variable lens 83. The light receiving element 85 receives the optical signal focused by the variable lens 83.

[0135] In the light receiving device of this embodiment, the optical signal collected by the collecting lens is focused by the lens area formed in the variable lens and guided to the light receiving portion of the light receiving element, so that spatial light arriving from any direction can be efficiently received.

[0136] (Hardware) Here, a hardware configuration for executing control and processing by a control unit or the like according to each embodiment of the present disclosure will be described using an information processing device 90 in Fig. 24 as an example. Note that the information processing device 90 in Fig. 24 is an example configuration for executing control and processing according to each embodiment, and does not limit the scope of the present disclosure.

[0137] As shown in Fig. 24, an information processing device 90 includes a processor 91, a main storage device 92, an auxiliary storage device 93, an input / output interface 95, and a communication interface 96. In Fig. 24, interface is abbreviated as I / F (Interface). The processor 91, the main storage device 92, the auxiliary storage device 93, the input / output interface 95, and the communication interface 96 are connected to each other via a bus 98 so as to be able to communicate data with each other. The processor 91, the main storage device 92, the auxiliary storage device 93, and the input / output interface 95 are also connected to a network such as the Internet or an intranet via the communication interface 96.

[0138] The processor 91 loads a program stored in an auxiliary storage device 93 or the like into the main storage device 92 and executes the loaded program. In each embodiment, a software program installed in the information processing device 90 may be used. The processor 91 executes control and processing according to each embodiment.

[0139] The main memory device 92 has an area where a program is loaded. The main memory device 92 may be a volatile memory such as a dynamic random access memory (DRAM). Alternatively, a non-volatile memory such as a magnetoresistive random access memory (MRAM) may be configured as the main memory device 92 or added.

[0140] The auxiliary storage device 93 stores various data. The auxiliary storage device 93 is configured with a local disk such as a hard disk or flash memory. Note that it is also possible to configure the main storage device 92 to store various data, and omit the auxiliary storage device 93.

[0141] The input / output interface 95 is an interface for connecting the information processing device 90 to peripheral devices. The communication interface 96 is an interface for connecting to external systems or devices via a network such as the Internet or an intranet based on standards and specifications. The input / output interface 95 and the communication interface 96 may be a common interface for connecting to external devices.

[0142] The information processing device 90 may be configured to be connected to input devices such as a keyboard, mouse, or touch panel as needed. These input devices are used to input information and settings. When a touch panel is used as the input device, the display screen of the display device may also serve as an interface for the input device. Data communication between the processor 91 and the input devices may be mediated by an input / output interface 95.

[0143] The information processing device 90 may also be equipped with a display device for displaying information. When a display device is equipped, the information processing device 90 preferably includes a display control device (not shown) for controlling the display of the display device. The display device may be connected to the information processing device 90 via the input / output interface 95.

[0144] The information processing device 90 may also be equipped with a drive device. The drive device acts as an intermediary between the processor 91 and a recording medium (program recording medium) for reading data and programs from the recording medium, writing the processing results of the information processing device 90 to the recording medium, etc. The drive device may be connected to the information processing device 90 via an input / output interface 95.

[0145] The above is an example of a hardware configuration for executing control and processing according to each embodiment. Note that the hardware configuration in FIG. 24 is an example of a hardware configuration for executing control and processing according to each embodiment, and does not limit the scope of the present invention. Furthermore, a program that causes a computer to execute control and processing according to each embodiment is also within the scope of the present invention. Furthermore, a program recording medium on which a program according to each embodiment is recorded is also within the scope of the present invention. The recording medium can be realized, for example, as an optical recording medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc). Furthermore, the recording medium may be realized as a semiconductor recording medium such as a USB (Universal Serial Bus) memory or an SD (Secure Digital) card, a magnetic recording medium such as a flexible disk, or other recording medium. When a program executed by a processor is recorded on a recording medium, the recording medium corresponds to a program recording medium.

[0146] The components that execute the control and processing of each embodiment can be combined in any manner, and the components that execute the control and processing of each embodiment may be realized by software or by circuits.

[0147] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0148] This application claims priority based on Japanese Patent Application No. 2021-047564, filed on March 22, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0149] 10, 20, 30, 40, 80 light receiving device 11, 21, 31, 41, 51, 61, 71, 81 Condenser lenses 13, 23, 33, 43, 53, 63, 73 Liquid crystal lens 15, 25, 35, 45, 55, 65, 75, 85 Light receiving element 17, 27, 37, 47, 57, 67, 77, 87 Control section 50, 60 Receiver 56, 66, 76 decoder 70 Communication equipment 78 Light transmitting unit 83 Variable Lens 410 Reduction optical system 411 First condenser lens 412 Second focusing lens 561, 661 First processing circuit 565, 665 Second processing circuit 662 Control circuit 663 Selector 700 Light projector 781 Irradiation unit 783 Spatial Light Modulator 787 Projection optical system 6611 High-pass filter 6613 Amplifier 6615 Integrator 7811 Light source 7812 Collimating Lens 7871 Fourier transform lens 7873 Aperture 7875 Projection Lens

Claims

1. a focusing lens for focusing the spatial optical signal; a variable lens in which a lens area is formed at an arbitrary position by adjusting a portion to which a voltage is applied, and a focusing direction and a focal length can be individually set by adjusting the applied voltage, and which focuses an optical signal derived from the spatial optical signal focused by the focusing lens in the lens area; a control unit for forming the lens region at a desired position of the variable lens and controlling an emission direction of the optical signal emitted from the variable lens; a light receiving element that is arranged with a light receiving portion facing the variable lens and receives the optical signal focused by the variable lens; The control means A light receiving device in which a position of the lens area is changed by adjusting a voltage applied to the variable lens, and the emission direction of the optical signal emitted from the variable lens is directed toward the light receiving portion of the light receiving element.

2. The variable lens is It is a transmissive liquid crystal lens, The control means 2. The light receiving device according to claim 1, wherein the lens region is formed at a desired position of the liquid crystal lens by adjusting a voltage applied to the liquid crystal lens.

3. The variable lens is It is a reflective liquid crystal lens, The control means 2. The light receiving device according to claim 1, wherein the lens region is formed at a desired position of the liquid crystal lens by adjusting a voltage applied to the liquid crystal lens.

4. The variable lens is LCOS (Liquid crystal on silicon) The control means The light receiving device according to claim 3 , wherein a virtual lens image that focuses the spatial light signal toward the light receiving portion of the light receiving element is displayed at a desired position on a display portion of the LCOS.

5. The control means by moving a position of the lens region, scanning an emission direction of the optical signal emitted from the variable lens; Detecting an arrival direction of the spatial optical signal based on a received light intensity of the optical signal by the light receiving element; The light receiving device according to claim 1 , wherein the variable lens forms the lens area in accordance with a detected direction of arrival of the spatial light signal.

6. further comprising an imaging means for imaging the direction of arrival of the spatial optical signal; The control means Detecting the direction of arrival of the spatial light signal based on the image captured by the imaging means; The light receiving device according to claim 1 , wherein the variable lens forms the lens area in accordance with a detected direction of arrival of the spatial light signal.

7. The variable lens is The light receiving device according to claim 1 , having a shape that matches the direction of arrival of the spatial optical signal.

8. The light receiving device according to claim 1 , further comprising a reduction optical system in which a plurality of the condenser lenses are combined.

9. A light receiving device according to any one of claims 1 to 8, A receiving device including a decoder for decoding a signal based on the optical signal received by the optical receiving device.

10. A receiving device according to claim 9 ; a light transmitting means for transmitting a spatial light signal corresponding to a signal decoded by a decoder included in the receiving device.

Images