Patent ID: 12212370

EXAMPLE EMBODIMENTS

Hereinafter, example embodiments of the present invention will be described with reference to the drawings. However, the example embodiments described below have technically preferable limitations for carrying out the present invention, but the scope of the invention is not limited to the following. In all the drawings used in the following description of the example embodiment, the same reference numerals are given to the same parts unless there is a particular reason. In the following example embodiments, repeated description of similar configurations and operations may be omitted. The directions of the arrows in the drawings illustrate an example, and do not limit the directions of signals between blocks.

First Example Embodiment

First, a light receiving device according to the first example embodiment will be described with reference to the drawings. The light receiving device of the present example embodiment is used for optical spatial communication using a spatial light signal. The light receiving device according to the present example embodiment receives a spatial light signal transmitted from a communication target. The light receiving device of the present example embodiment identifies the communication device that is the light transmission source of the spatial light signal based on the received spatial light signal. For example, when the communication device on which the light receiving device of the present example embodiment is mounted identifies a communication device that is the light transmission source of the spatial light signal, the communication device transmits the spatial light signal to the identified communication device. Hereinafter, light for searching for a communication target and light carrying information to be exchanged with the communication target are referred to as spatial light signals. Hereinafter, it is assumed that the spatial light signal includes identification information for uniquely identifying the communication device that is the light transmission source.

(Configuration)

FIG.1is a conceptual diagram illustrating an example of a configuration of a light receiving device10of the present example embodiment. The light receiving device10includes a sensor array11, a lens12, and a reception unit13. The sensor array11includes a plurality of light receivers110.

The sensor array11has a structure in which a plurality of light receivers110is disposed in an array. The plurality of light receivers110included in the sensor array11is disposed with the light receiving face facing the lens12. The light receiving faces of the plurality of light receivers110form a light receiving face of the sensor array11. The sensor array11is disposed in such a way that the light receiving face is located between the main surface of the lens12and the focal surface of the lens12. The focal surface of the lens12is formed farther away from the lens12than the sensor array11.

The spatial light signal is incident on the light receiving face of the light receiver110. The light receiver110converts a spatial light signal received by the light receiving face into an electric signal (hereinafter, also referred to as a signal). The light receiver110outputs the converted signal to a reception unit13.

For example, the light receiver110is achieved by a photodiode (PD). For example, the light receiver110is achieved by a PN type photodiode, a PIN type photodiode, or an avalanche photodiode. The light receiver110may be a photodetector other than a photodiode as long as it can convert the received spatial light signal into an electric signal.

The light receiver110is sensitive to a wavelength band of a spatial light signal used for optical spatial communication. For example, the light receiver110has sensitivity to a wavelength band in the visible region. For example, the light receiver110may have sensitivity in an infrared region or an ultraviolet region. The wavelength band to be received by the light receiver110may be selected according to the wavelength band of the spatial light signal used for the optical spatial communication.

The lens12is disposed at a position capable of receiving a spatial light signal from the outside. The lens12is disposed in such a way that the light receiving face of the sensor array11is positioned between the main surface and the focal surface. The focal surface of the lens12is formed farther away from the lens12than the sensor array11. The lens12is an optical lens that focuses the spatial light signal on the light receiving face of the sensor array11. The spatial light signal focused by the lens12is applied to the light receiving face of the sensor array11. Since the light receiving face of the sensor array11is disposed in front of the focal surface of the lens, the light receiving face of the sensor array11receives a widened spatial light signal by its surface.

The reception unit13receives a signal from each of the plurality of light receivers110constituting the sensor array11. The reception unit13integrates the received signal. The reception unit13estimates an incoming direction of the spatial light signal received by the plurality of light receivers110based on the integrated signal. The reception unit13identifies that the communication target is located in the incoming direction of the spatial light signal. The reception unit13associates the identified communication target with the light receiver110that receives the spatial light signal from the communication target. The reception unit13amplifies the electric signal from the light receiver110associated with the communication target. The reception unit13decodes the amplified electric signal and analyzes a signal from the communication target.

[Reception Unit]

Next, a configuration of the reception unit13will be described in detail with reference to the drawings.FIG.2is a block diagram illustrating an example of a configuration of the reception unit13. The reception unit13includes a plurality of first processing circuits15-1to M, a control circuit16, a selector17, and a plurality of second processing circuits18-1to N (M and N are natural numbers).FIG.2illustrates the internal configuration of only the first processing circuit15-1among the plurality of first processing circuits15-1to M, but the internal configuration of each of the plurality of first processing circuits15-2to M is also similar to that of the first processing circuit15-1.

The first processing circuit15includes a high-pass filter151, an amplifier153, and an integrator155. InFIG.2, the high-pass filter151is denoted as a high path filter (HPF), the amplifier153is denoted as an amplifier (AMP), and the integrator155is denoted by as an integrator (INT). The signal having passed through the high-pass filter151is input in parallel to the amplifier153and the integrator155. The light receiver110and the first processing circuit constitute one unit for each light receiver110.

The high-pass filter151acquires a signal from the light receiver110. The high-pass filter151selectively passes a signal of a high frequency component corresponding to the wavelength band of the spatial light signal among the acquired signals. The high-pass filter151cuts off a signal derived from ambient light such as sunlight. Instead of the high-pass filter151, a band pass filter that selectively passes a signal in a wavelength band of a spatial light signal may be configured. When saturated with intense sunlight, the spatial light signal is unreadable. Therefore, a color filter that selectively passes the light in the wavelength band of the spatial light signal may be installed at the front stage of the light receiving face of the light receiver110. The signal that has passed through the high-pass filter151is supplied to the amplifier153and the integrator155.

The amplifier153acquires the signal output from the high-pass filter151. The amplifier153amplifies the acquired signal. The amplifier153outputs the amplified signal to the selector17. Among the signals input to the selector17, the signal to be received is allocated to any one of the plurality of second processing circuits18-1to N under the control of the control circuit16. The signal to be received is a signal from the light receiver110that receives a spatial light signal from a communication device to be communicated (not illustrated). A signal from the light receiver110that is not used for receiving the spatial light signal is not output to the second processing circuit18.

The integrator155acquires the signal output from the high-pass filter151. The integrator155integrates the acquired signal. The integrator155outputs the integrated signal to the control circuit16.

The integrator155is disposed to measure the intensity of the spatial light signal received by the light receiver110. In the present example embodiment, the light receiving face of the sensor array11receives, by its surface, the spatial light signal in a state in which the beam diameter is spread, thereby increasing the speed of searching for the communication target. Since the intensity of the spatial light signal received in a state where the beam diameter is not narrowed is weaker than that of the signal a case where the beam diameter is narrowed, it is difficult to measure the voltage of the signal amplified only by the amplifier153. By using the integrator155, for example, the voltage of the signal can be increased to a level at which the voltage can be measured by integrating the signal for several milliseconds (msec) to several tens of milliseconds.

The control circuit16acquires a signal output from the integrator155included in each of the plurality of first processing circuits15-1to M. In other words, the control circuit16acquires a signal derived from the spatial light signal received by each of the plurality of light receivers110. The control circuit16compares the readings of the signals derived from the plurality of light receivers110adjacent to each other, and selects the light receiver110having the maximum signal intensity. The control circuit16causes the selector17to allocate the signal derived from the selected light receiver110to any one of the plurality of second processing circuits.

The control circuit16selecting the light receiver110corresponds to estimating the incoming direction of the spatial light signal. That is, the control circuit16selecting the light receiver110corresponds to identifying the communication device that is the light transmission source of the spatial light signal. Allocating the signal derived from the selected light receiver110to any one of the plurality of second processing circuits corresponds to associating the identified communication target with the light receiver110that receives the spatial light signal from the communication target. That is, the control circuit16identifies the communication device that is the light transmission source of the spatial light signal based on the spatial light signal received by the sensor array11. For example, when a communication device (not illustrated) on which the light receiving device10of the present example embodiment is mounted identifies a communication device (not illustrated) that is a light transmission source of the spatial light signal, the communication device transmits the spatial light signal to the identified communication device.

A signal amplified by the amplifiers153included in each of the plurality of first processing circuits15-1to M is input to the selector17. The selector17outputs a signal to be received among the input signals to any one of the plurality of second processing circuits18-1to N according to the control of the control circuit16. A signal not to be received is not output from the selector17.

A signal derived from the light receiver110allocated by the control circuit16is input to the second processing circuit18. The second processing circuit18decodes the input signal. The second processing circuit18may be configured to perform some 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 illustrated).

When the selector17selects a signal derived from the light receiver110selected by the control circuit16, one second processing circuit is allocated to one communication target. That is, the control circuit16allocates a signal derived from the spatial light signal, from each of the plurality of communication targets, received by the sensor arrays11to any one of the plurality of second processing circuits18-1to N. As a result, the light receiving device10can simultaneously read signals derived from spatial light signals from a plurality of communication targets on individual channels. In a general method, spatial light signals from a plurality of communication targets are read in a time division manner in one channel. On the other hand, in the method of the present example embodiment, since spatial light signals from a plurality of communication targets are simultaneously read in a plurality of channels, the transmission speed is improved. The method of the present example embodiment may be configured to receive signals in a time division manner according to the situation.

For example, the scan of the communication target using the integrator155may be performed as a primary scan, and the incoming direction of the spatial light signal may be identified with coarse accuracy. Then, secondary scanning with fine accuracy may be performed in the identified direction to identify a more accurate position of the communication target. When communication with the communication target is possible, an accurate position of the communication target can be determined by exchanging signals with the communication target. For example, in a case where the light receiving device10is mounted on the mobile body, when the position of the communication target can be accurately determined, the moving direction, the speed, and the like of each other can be shared through communication with the communication target. When the moving directions, speeds, and the like can be shared, the mutual positional relationship can be predictively controlled with higher accuracy.

[Integrator]

Next, an example of a circuit configuration of the integrator155will be described with reference to the drawings.FIG.3is an example of a circuit configuration of the integrator155(integrator155-1). The integrator155-1includes a resistor R, an operational amplifier OP, a capacitor C, and a switch SW. InFIG.3, regarding the resistor R, the capacitor C, and the switch SW, the left terminal is referred to as a first end, and the right terminal is referred to as a second end. The operational amplifier OP has an inverting input terminal V−, a non-inverting input terminal V+, and an output terminal.

The first end of the resistor R is connected to an input end Vin. The second end of the resistor R is connected to the inverting input terminal V− of the operational amplifier OP, the first end of the capacitor C, and the first end of the switch SW. The inverting input terminal V− of the operational amplifier OP is connected to the second end of the resistor R, the first end of the capacitor C, and the first end of the switch SW. The non-inverting input terminal V+ of the operational amplifier is grounded. The output terminal of the operational amplifier OP is connected to an output end Vout, the second end of the capacitor, and the second end of the switch SW. The first end of the capacitor is connected to the second end of the resistor R, the inverting input terminal V− of the operational amplifier OP, and the first end of the switch SW. The second end of the capacitor is connected to the output terminal of the operational amplifier OP, the second end of the switch SW, and the output end Vout. The first end of the switch SW is connected to the second end of the resistor R, the first end of the capacitor C, and the inverting input terminal V− of the operational amplifier OP. The second end of the switch SW is connected to the second end of the capacitor C, the output terminal of the operational amplifier OP, and the output end Vout.

A reset pulse is applied to the switch SW at a predetermined timing. The switch SW is closed only for a predetermined period (reset time Trst) after the reset pulse is applied. The time during which the switch is open corresponds to an integration time Tint. The reset time Trst is set to be shorter than the integration time Tint.

FIG.4is a graph for explaining the operation of the integrator155-1.FIG.4illustrates a negative feedback reset operation of the integrator155-1including the operational amplifier OP. The integrator155-1functions as a kind of low-pass filter. The integrator155-1accumulates the charge in the capacitor C during the integration time Tint. When a reset pulse is applied to the switch SW, the charge accumulated in the capacitor C is reset. For example, when a voltage value immediately before resetting is read by an analog-digital (AD) converter (not illustrated), the voltage of the signal can be measured.

[Direction Detection]

Next, direction detection by the light receiving device10will be described with reference to the drawings.FIGS.5and6are conceptual diagrams illustrating a state in which a spatial light signal is incident on the lens12included in the light receiving device10and the spatial light signal is received by the sensor array11. The distance between the main surface of the lens12and the focal surface corresponds to a focal length f. As illustrated inFIGS.5and6, the sensor array11is disposed in such a way that the light receiving faces of the plurality of light receivers110are located between the main surface and the focal surface.

The example ofFIG.5is an example in which a spatial light signal D1comes from below the lens12. The spatial light signal D1having passed through the lens12is focused toward a focal point F1on the focal surface of the lens12. The light receiving faces of the upper light receivers110among the plurality of light receivers110receive the spatial light signal D1by its surface.

FIG.6illustrates an example in which a spatial light signal D2comes from above the lens12. The spatial light signal D2having passed through the lens12is focused toward a focal point F2on the focal surface of the lens12. The light receiving faces of the lower light receivers110among the plurality of light receivers110receive the spatial light signal D2by its surface.

FIG.7is a perspective view of the light receiving face of the sensor array11when viewed through the lens12. In the example ofFIG.7, the spatial light signal D1is received by the plurality of lower light receivers110of the sensor array11, and the spatial light signal is received by the plurality of upper left light receivers110of the sensor array11. As illustrated inFIG.7, on the light receiving face of the sensor array11, the spatial light signal is received not only at a position in the vertical direction but also at a position corresponding to the incoming direction in the horizontal direction.

The spatial light signal arriving from the distance is substantially collimated. Therefore, by detecting the position where the spatial light signal is collected by the sensor array11, it is possible to estimate from which direction the spatial light signal has come. The spatial light signal collected by the lens12is received by the light receiving faces of the plurality of light receivers110. The incoming direction of the spatial light signal can be estimated from the intensity ratio of the spatial light signals received by the respective light receivers110. When the communication device to be communicated is associated with the incoming direction of the spatial light signal, the light receiver110and the communication device can be associated with each other.

FIG.8illustrates an example in which the light receiving faces of a light receiver110-A, a light receiver110-B, a light receiver110-C, and a light receiver110-D adjacent to each other receives the spatial light signal D1. In the case of the example ofFIG.8, the light receiving area of the light receiver110-D is maximum. Therefore, for the light receiver110-D, the signal intensity at the spatial light signal D1is maximized. In this case, the light receiving device10determines that the light receiver110-D receives the spatial light signal D1. When the incoming direction of the spatial light signal and the light receiver110are associated with each other based on the positional relationship between the sensor array11and the lens12, the incoming direction of the spatial light signal can be estimated according to the position of the light receiver110at which the signal intensity is maximized.

In a case where a plurality of communication targets is close to each other, or in a case where another communication target is located between the light receiving device10and the communication target, positions where the plurality of spatial light signals is collected may overlap with each other. In such a case, a plurality of overlapping spatial light signals may be separated according to the situation. It is assumed that it can be determined that the plurality of spatial light signals is received based on identification information or the like included in each of the plurality of spatial light signals.

FIG.9illustrates an example in which the light receiving regions of the spatial light signal D1and the spatial light signal D2partially overlap. In the example ofFIG.9, the light receiver110-D has the maximum signal intensity of the spatial light signal D1, and the light receiver110-A has the maximum signal intensity of the spatial light signal D2. The light receiving device10determines that the light receiver110-D receives the spatial light signal D1, and determines that the light receiver110-A receives the spatial light signal D2. In the example ofFIG.9, since the degree of overlapping of the light receiving regions is slight, the spatial light signal D1and the spatial light signal D2can be separated without time division.

FIG.10illustrates an example in which most of the light receiving regions of the spatial light signal D1and the spatial light signal D2overlap each other. In the case of the example ofFIG.10, the spatial light signal D1and the spatial light signal D2cannot be separated based on the signal intensities of the spatial light signal D1and the spatial light signal D2. In such a case, the spatial light signal D1and the spatial light signal D2can be separated by time-dividing reception timings of the spatial light signal D1and the spatial light signal D2. At least any one of a plurality of communication targets having overlapping light receiving regions may be notified to be shifted in position.

As described above, the light receiving device of the present example embodiment includes the sensor array, the lens, and the reception unit. The lens collects the spatial light signal. The sensor array includes a plurality of light receivers that receive spatial light signal collected by the lenses. The reception unit integrates the electric signal derived from the spatial light signal received by each of the plurality of light receivers, and selects, according to a voltage value of the integrated electric signal, a light receiver that receives the spatial light signal.

In the light receiving device of the present example embodiment, the spatial light signal condensed by the lens is received by at least any one of the plurality of light receivers. The light receiving device of the present example embodiment integrates the electric signal derived from the spatial light signal, and selects, according to the voltage value of the integrated electric signal, a light receiver that receives the spatial light signal. According to the light receiving device of the present example embodiment, it is possible to collectively receive the spatial light signals from the plurality of communication targets and collectively distinguish the light transmission sources of the spatial light signals. Therefore, according to the light receiving device of the present example embodiment, spatial light signals coming from various directions can be efficiently received.

In an aspect of the present example embodiment, the light receiving faces of the plurality of light receivers are disposed in an array on the same plane in the same direction. The lens is disposed in such a way that the light receiving faces of the plurality of light receivers are positioned between the main surface and the focal surface of the lens.

According to the present aspect, by integrating the electric signal derived from the spatial light signal, even when the spatial light signal is received by the surface, the voltage value of the spatial light signal can be measured. Therefore, according to the present aspect, since the spatial light signal can be received at a wide light receiving angle, utilization efficiency of light is higher than that in a case where the spatial light signal is received at a point.

In an aspect of the present example embodiment, the reception unit includes a plurality of first processing circuits, a selector, a second processing circuit, and a control circuit. The plurality of first processing circuits is associated with the plurality of respective light receivers, amplifies the electric signals derived from the spatial light signal received by the plurality of respective light receivers, and integrates each of the electric signals. The selector receives the electric signals amplified by the first processing circuit and selectively outputs at least any one of the received electric signals. The second processing circuit decodes the electric signal output from the selector. The control circuit selects, according to the voltage value of the electric signal integrated by each of the plurality of first processing circuits, a light receiver that receives the spatial light signal. The control circuit causes the selector to allocate the electric signal from the selected light receiver to any one of the plurality of second processing circuits.

In an aspect of the present example embodiment, in a case where the spatial light signal is received by the plurality of light receivers adjacent to each other, the control circuit selects a light receiver having a maximum voltage value among voltage values of the electric signals integrated by the plurality of first processing circuits as the light receiver that receives the spatial light signal. For example, in a case where the spatial light signals from the plurality of light transmission sources are received by the plurality of light receivers adjacent to each other, the control circuit selects, according to the voltage value of the electric signal integrated by each of the plurality of first processing circuits, a light receiver that receives the spatial light signal for each light transmission source. For example, in a case where the control circuit is not allowed to select, according to the voltage value of the electric signal integrated by each of the plurality of first processing circuits, a light receiver that receives the spatial light signal for each light transmission source, the control circuit causes the same light receiver to receive the spatial light signal in a time division manner for each light transmission source.

According to the present aspect, the spatial light signal, from the single light transmission source, received by the plurality of light receivers can be allocated to any one of the light receivers. According to the present aspect, the spatial light signals, from the plurality of light transmission sources, received by the plurality of light receivers can be allocated to any one of the light receivers.

Second Example Embodiment

Next, a light receiving device according to the second example embodiment will be described with reference to the drawings. The light receiving device of the present example embodiment is different from that of the first example embodiment in that it includes a light pipe. The light pipe is a member that guides a spatial light signal received in a gap between the plurality of light receivers constituting the sensor array to each of the plurality of light receivers constituting the sensor array.

FIG.11is a conceptual diagram illustrating an example of a configuration of a light receiving device20of the present example embodiment. The light receiving device20includes a sensor array21, a lens22, and a reception unit23. The sensor array21includes a plurality of light receivers210and a plurality of light pipes211. The light pipe211is disposed in each of the plurality of light receivers210. Main functions of the sensor array21, the lens22, and the reception unit23are similar to those in the first example embodiment. Hereinafter, description will be given focusing on the light pipe211that is not included in the light receiving device10of the first example embodiment.

A gap corresponding to the size of the light receiving face of the light receiver210is generated between the plurality of light receivers210constituting the sensor array21. When the light receiving face is large, the gap between the adjacent light receivers210is small. When the light receiving face is small, the gap between the adjacent light receivers210is large. In a case where the spatial light signal is directly incident on the light receiving face of the sensor array21, when the gap between the adjacent light receivers210is large as compared with the spot diameter of the spatial light signal condensed on the light receiving face, the spot of the spatial light signal entering the gap is not detected. When the spot diameter of the spatial light signal condensed on the light receiving face of the sensor array21is large, the intensity of the spatial light signal received by each light receiver210decreases. Therefore, when the spatial light signal is directly incident on the light receiving face of the sensor array21, it is necessary to optimize the size of the gap between the adjacent light receivers210and the spot diameter of the spatial light signal.

FIG.12is a perspective view of a state in which the light pipes211are installed on the light receiving faces of the plurality of respective light receivers210. The light pipe211is provided in association with each of the plurality of light receivers210. The light pipe211has an incident face P1on which a spatial light signal is incident and an outgoing face P2from which a light signal guided inside the light pipe211is emitted. The outgoing face P2of the light pipe211is disposed in contact with the light receiving face of the light receiver210with which the light pipe211is associated. As long as the light signal emitted from the outgoing face P2of the light pipe211is incident on the light receiving face of the light receiver210, the outgoing face P2of the light pipe211and the light receiving face of the light receiver210may not be in contact with each other.

The adjacent light pipes211are disposed in such a way that there is no gap between the incident faces P1. The focal surface of the lens22may be formed closer to the sensor array21than the incident face P1of the light pipe211. The focal surface of the lens22may be formed in front of the light receiving face of the sensor array21when viewed from the lens22. AlthoughFIG.12illustrates an example in which the incident face P1and the outgoing face P2are parallel to each other, the incident face P1and the outgoing face P2may be non-parallel as long as the light signal can be guided from the incident face P1toward the outgoing face P2.

For example, the light pipe211can be made of a material of a general optical fiber. The light pipe211is preferably made of a material that easily transmits light in the wavelength band of the spatial light signal. The inner face of the light pipe211is a mirror surface that reflects a light signal guided inside the light pipe211. A light signal derived from the spatial light signal incident from the incident face P1of the light pipe211is guided to the outgoing face P2while being reflected by the inner face of the light pipe211. The light signal guided to the outgoing face P2is emitted from the outgoing face P2.

An anti-reflection layer corresponding to the wavelength band of the spatial light signal may be provided on the incident face P1of the light pipe211. When the anti-reflection layer is provided on the incident face P1, the spatial light signal reflected by the incident face P1can be reduced. A color filter that selectively passes light in the wavelength band of the spatial light signal may be provided on the incident face P1of the light pipe211. When the color filter is provided on the incident face P1, the light in the wavelength band of the spatial light signal is selectively guided to the light receiving face of the light receiver210, so that the noise component included in the spatial light signal can be removed.

When the light pipe211is used, the light receiving face of the light receiver210can be reduced. Therefore, the light receiver210having a small light receiving face can be configured while having the same light receiving efficiency. Therefore, when the light pipe211is used, options of the light receiver210are widened. For example, when the light pipe211is used, the light receiver210having a small light receiving face but high sensitivity can be used.

As described above, the sensor array of the light receiving device of the present example embodiment includes the plurality of light pipes that is associated with the respective light receiving faces of the plurality of respective light receivers, and each guides the spatial light signal to each of the light receiving faces of the plurality of light receivers. For example, each of the plurality of light pipes includes an incident face on which the spatial light signal is incident and an outgoing face from which the light signal incident from the incident face and guided is emitted, and the light pipes are disposed in such a way that the incident faces form the same plane without a gap. For example, each of the plurality of light pipes is disposed with the outgoing face facing the associated light receiving face.

According to the light receiving device of the present example embodiment, by installing the light pipes on the light receiving faces of the plurality of light receiving units, the light signal derived from the spatial light signal can be guided to the light receiving face of each light receiving unit without optimizing the size of the gap between the adjacent light receiving units and the spot diameter of the spatial light signal. Therefore, according to the light receiving device of the present example embodiment, the spatial light signal can be received more efficiently.

Third Example Embodiment

Next, a communication device according to a third example embodiment will be described with reference to the drawings. The communication device of the present example embodiment includes the light receiving device (also referred to as a light receiving unit) of each of the first and second example embodiments.

FIG.13is a block diagram illustrating an example of a configuration of a communication device3of the present example embodiment. The communication device3includes a light receiving unit30, a light transmitting unit35, and a light transmitting control unit37. The light receiving unit30corresponds to the light receiving device of the first example embodiment or the light receiving device20of the second example embodiment. Details of the light receiving unit30will not be described below.

The light receiving unit30receives the spatial light signal transmitted from the communication device to be communicated. The light receiving unit30decodes a signal based on the received spatial light signal to output the decoded signal to the light transmitting control unit37. The light transmitting unit35transmits the spatial light signal under the control of the light transmitting control unit37. The light transmitting control unit37acquires a signal from the light receiving unit30. The light transmitting control unit37controls the light transmitting unit35according to a signal from the light receiving unit30.

[Light Transmitting Unit]

Next, an example of a configuration of the light transmitting unit will be described with reference to the drawings.FIG.14is a conceptual diagram illustrating an example of a configuration of the light transmitting unit35. The light transmitting unit35includes a light source320, a spatial light modulator330, and a projection optical system340.FIG.14is conceptual, and does not accurately represent the positional relationship between the components, the traveling direction of light, and the like.

The light source320includes an emitter321and a collimator323. The emitter321emits laser light301of a predetermined wavelength band used for spatial light communication according to the control of the light transmitting control unit37. The collimator323converts the laser light301emitted from the emitter321into collimated beam302. The laser light301emitted from the emitter321is converted into the collimated beam302by the collimator323, and emitted from the light source320. The collimated beam302emitted from the light source320travels toward the modulation unit of the spatial light modulator330.

As illustrated inFIG.14, the incident angle of the collimated beam302is non-perpendicular to the irradiated surface of the modulation unit of the spatial light modulator330. That is, the emission axis of the collimated beam302emitted from the light source320is oblique to the irradiated surface of the modulation unit of the spatial light modulator330. When the emission axis of the collimated beam302is oblique to the irradiated surface of the modulation unit of the spatial light modulator330, the collimated beam302can be incident on the irradiated surface without using a beam splitter, so that the utilization efficiency of light can be improved. When the emission axis of the collimated beam302is set obliquely with respect to the irradiated surface of the modulation unit of the spatial light modulator330, the size of the light transmitting unit can be made compact.

The spatial light modulator330includes a modulation unit irradiated with the collimated beam302. In the modulation unit of the spatial light modulator330, a pattern corresponding to the detection light is set according to the control of the light transmitting control unit37. For example, the spatial light modulator330is achieved by a spatial light modulator including ferroelectric liquid crystal, homogeneous liquid crystal, vertical alignment liquid crystal, or the like. For example, the spatial light modulator330can be achieved by liquid crystal on silicon (LCOS). The spatial light modulator330may be achieved by a micro electro mechanical system (MEMS).

The projection optical system340is an optical system that projects modulated light303modulated by the spatial light modulator330as a spatial light signal305. As illustrated inFIG.14, the projection optical system340includes a Fourier transform lens346, an aperture347, and a projection lens348.

The Fourier transform lens346is an optical lens that forms an image formed when the modulated light303modulated by the spatial light modulator330is projected at infinity at a focal position near the aperture347.

The aperture347is a frame that shields high order light included in the light focused by the Fourier transform lens346and limits the outer edge of the display region. The opening of the aperture347is opened smaller than the outer periphery of the display region at the position of the aperture347, and is installed in such a way as to block the peripheral region of the image at the position of the aperture347. For example, the opening of the aperture347is formed in a rectangular shape or a circular shape. The aperture347is preferably installed at a focal position of the Fourier transform lens346. The aperture347may be shifted from the focal position of the Fourier transform lens346as long as high order light can be shielded and the display region can be limited.

The projection lens348is an optical lens that magnifies the light focused by the Fourier transform lens346. The projection lens348enlarges the spatial light signal305in such a way that an image corresponding to the phase image set in the modulation unit of the spatial light modulator330is formed on the face to be projected.

[Light Transmitting Control Unit]

Next, an example of a configuration of the light transmitting control unit37will be described with reference to the drawings.FIG.15is a block diagram illustrating an example of a configuration of the light transmitting control unit37. The light transmitting control unit37includes a light transmission condition storage unit371, a light transmission condition setting unit372, a modulator control unit373, and a light source drive unit374.

The light transmission condition storage unit371stores a pattern corresponding to the spatial light signal305. In a case where the spatial light modulator330is of the phase modulation type, the light transmission condition storage unit371stores a phase distribution corresponding to the spatial light signal305. The light transmission condition storage unit371stores a light transmission condition including a light source control condition for controlling the light source320and a modulation element control condition for controlling the spatial light modulator330. The modulation element control condition is a control condition for setting a pattern corresponding to the spatial light signal305in the modulation unit of the spatial light modulator330. The light source control condition is a control condition for emitting the laser light301from the light source320.

The light transmission condition setting unit372sets a light transmission condition for transmitting the spatial light signal305. The light transmission condition setting unit372sets a modulation element control condition in the modulator control unit373. The light transmission condition setting unit372sets a light source control condition in the light source drive unit374. The light transmission condition setting unit372matches the timing at which the modulation element control condition is set in the modulator control unit373with the timing at which the light source control condition is set in the light source drive unit374. As a result, the modulation unit of the spatial light modulator330in a state where the pattern corresponding to the spatial light signal305is displayed is irradiated with the collimated beam302derived from the laser light301emitted from the light source320.

For example, the light transmission condition setting unit372sets, in the light source drive unit374, a light source control condition for continuously emitting the laser light301during a period in which the communication device to be communicated is scanned (also referred to as a scanning period). At this time, the light transmission condition setting unit372sets, in the modulator control unit373, a modulation element control condition for transmitting the spatial light signal305of the first projection pattern in order to scan the communication device to be communicated. As a result, the spatial light signal305of the first projection pattern for scanning the communication device to be communicated is transmitted from the light transmitting unit35.

For example, during a period (also referred to as a communication period) in which communication with the communication device to be communicated is performed, the light transmission condition setting unit372sets, in the light source drive unit374, a light source control condition for emitting the spatial light signal305according to a signal to be transmitted to the communication device to be communicated. At this time, the light transmission condition setting unit372sets, in the modulator control unit373, a modulation element control condition for transmitting the spatial light signal305of the second projection pattern having a projection area smaller than that of the first projection pattern toward the communication device to be communicated. As a result, the spatial light signal305of the second projection pattern for communicating with the communication device to be communicated is transmitted from the light transmitting unit35.

For example, the light transmission condition setting unit372sets, in the spatial light modulator330, a modulation element control condition for selectively transmitting the spatial light signal305toward the incoming direction of the spatial light signal305for a predetermined period from the timing at which the spatial light signal305is received. By limiting the light transmission direction of the spatial light signal305, it is possible to set the output of the spatial light signal305to be transmitted toward the position of the communication device to be communicated high.

The modulator control unit373receives the pattern according to the spatial light signal305and the modulation element control condition from the light transmission condition setting unit372. The modulator control unit373drives a driver (not illustrated) that changes a pattern set in the modulation unit of the spatial light modulator330according to the modulation element control condition received from the light transmission condition setting unit372. As a result, a pattern corresponding to the spatial light signal305is set in the modulation unit of the spatial light modulator330.

The light source drive unit374includes a pulse generator (not illustrated) and a drive circuit (not illustrated). The pulse generator generates a pulse train related to a signal to be transmitted according to the light source control condition received from the light transmission condition setting unit372, and modulates the drive circuit. When the communication device to be communicated is determined, the pulse generator generates a pulse train related to a signal to be transmitted according to the content of communication with the communication device, and modulates the drive circuit. For example, the content of communication with the communication device is input by an input device (not illustrated). The drive circuit drives the emitter321in a state of being modulated in accordance with the pulse train generated by the pulse generator. That is, the light source drive unit374drives the emitter321in accordance with the pulse train pattern according to the light source control condition received from the light transmission condition setting unit372, and emits the laser light301from the emitter321. As a result, the modulation unit of the spatial light modulator330is irradiated with the collimated beam302derived from the laser light301in accordance with the timing at which the pattern is set in the modulation unit of the spatial light modulator330. The collimated beam302emitted to the modulation unit of the spatial light modulator330is modulated by the modulation unit of the spatial light modulator330. The modulated light303modulated by the modulation unit of the spatial light modulator330is transmitted as the spatial light signal305related to the pattern displayed on the modulation unit of the spatial light modulator330.

[Communication Method]

Next, a communication method with a plurality of communication targets by the communication device3according to the present example embodiment will be described with reference to the drawings. Here, the communication method by the communication device3of the present example embodiment and the communication method by the communication device of the comparative example will be described in comparison. The communication device of the comparative example has only one channel used for communication.

FIG.16is a conceptual diagram for describing a communication method by the communication device3of the present example embodiment. The left side of the bold arrow in the center shows an example of communication between the communication device3and the plurality of communication devices300to be communicated in the scanning period. The right side of the bold arrow in the center illustrates an example of communication between the communication device3and the plurality of communication devices300to be communicated in the communication period.

In the scanning period, the communication device3transmits the spatial light signal of the first projection pattern. When receiving the spatial light signals from the communication devices300to be communicated (T1to T4), the communication device3identifies the directions of the respective communication devices300according to the incoming directions of the spatial light signals. When identifying the respective directions of the communication devices300, the communication device3allocates the channels (ch1to ch4) to the signals derived from the spatial light signals from the respective communication devices300(T1to T4) and shifts to the communication period.

In the communication period, the communication device3transmits a spatial light signal of a second projection pattern having a projection area smaller than that of the first projection pattern to each of the communication devices300(T1to T4). Since the light transmission direction is narrowed in the communication period, the energy of the spatial light signal to be transmitted can be made larger than that in the scanning period. The communication device3communicates with each of the plurality of communication devices300by processing a signal derived from a spatial light signal from each of the communication devices300on a channel allocated to each of the communication devices300.

FIG.17is a conceptual diagram for describing a communication method by a communication device390of the comparative example. The left side of the bold arrow in the center shows an example of communication between the communication device390and the plurality of communication devices395to be communicated in the scanning period. The right side of the bold arrow in the center illustrates an example of communication between the communication device390and the plurality of communication devices395to be communicated in the communication period.

In the scanning period, the communication device390transmits the spatial light signal while changing the light transmission direction. Therefore, the spatial light signal from the communication device395sequentially reaches each of the plurality of communication devices390(C1to C4). Similarly, each of the plurality of communication devices395transmits the spatial light signal while changing the light transmission direction. The communication device390individually receives the spatial light signal from each of the plurality of communication devices395. The communication device390sequentially identifies the position of each communication device395based on the spatial light signal from each of the plurality of communication devices300. At this stage, communication between the communication device390and each of the plurality of communication devices395(C1to C4) is established, and the process shifts to the communication period. As described above, in the method of the comparative example, since communication is sequentially established with the individual communication devices395(C1to C4), it takes more time to establish communication, compared with the communication method of the present example embodiment.

In the communication period, the communication device390sequentially transmits the spatial light signal to each of the communication devices395(C1to C4). The communication device390receives signals derived from the spatial light signals from the individual communication devices395(C1to C4) in a time division manner and processes the signals in a single channel (ch1), thereby communicating with each of the plurality of communication devices300. Therefore, in the comparative example, in order to obtain a communication speed similar to that of the present example embodiment, it is necessary to configure a system with a very high transmission speed.

As described above, the communication device of the present example embodiment includes the light receiving unit, the light transmitting unit, and the light transmitting control unit. The light receiving unit includes a sensor array, a lens, and a reception unit. The lens collects the spatial light signal. The sensor array includes a plurality of light receivers that receive spatial light signal collected by the lenses. The reception unit integrates the electric signal derived from the spatial light signal received by each of the plurality of light receivers, and selects, according to a voltage value of the integrated electric signal, a light receiver that receives the spatial light signal. The light transmitting unit transmits the second spatial light signal according to the first spatial light signal received by the light receiving unit. The light transmitting control unit controls the light transmitting unit according to the first spatial light signal received by the light receiving unit, and causes the light transmitting unit to transmit the second spatial light signal to the communication target that is the light transmission source of the first spatial light signal.

In an aspect of the present example embodiment, the light transmitting control unit causes the light transmitting unit to transmit the second spatial light signal in the first projection pattern in a scanning period in which at least one communication target is scanned. In a communication period in which communication with at least one communication target is performed, the light transmitting control unit causes the light transmitting unit to transmit the second spatial light signal toward the communication target in a second projection pattern smaller than the first projection pattern.

According to the communication method of the present example embodiment, since the directions from which the plurality of spatial light signals has comes can be instantaneously identified, communication with the communication target can be established at high speed. According to the communication method of the present example embodiment, since communication can be performed simultaneously with a plurality of communication targets, the transmission speed of the communication system can be set low.

Fourth Example Embodiment

Next, a light receiving device according to the fourth example embodiment will be described with reference to the drawings. The light receiving device of the present example embodiment has a configuration obtained by simplifying the light receiving devices of the first and second example embodiments.

FIG.18is a conceptual diagram illustrating an example of a light receiving device40of the present example embodiment. The light receiving device40includes a sensor array41, a lens42, and a reception unit43.

The lens42collects the spatial light signal. The sensor array41includes a plurality of light receivers410that receive the spatial light signal collected by the lens42. The reception unit43integrates the electric signal derived from the spatial light signal received by each of the plurality of light receivers410, and receives the spatial light signal according to the voltage value of the integrated electric signal.

The light receiving device of the present example embodiment receives the spatial light signal condensed by the lens by at least any one of the plurality of light receivers. The light receiving device according to the present example embodiment integrates the electric signal derived from the spatial light signal received by each of the plurality of light receivers to set the voltage of the electric signal to a measurable level. Then, the light receiving device of the present example embodiment receives the spatial light signal according to the integrated voltage value of the electric signal.

According to the light receiving device of the present example embodiment, spatial light signals coming from various directions can be efficiently received.

(Hardware)

Here, a hardware configuration for executing processing of the control system (reception unit13, control circuit16, light transmitting control unit37, and the like) according to each example embodiment will be described using an information processing device90ofFIG.19as an example. The information processing device90inFIG.19is a configuration example for executing processing of the control system of each example embodiment, and does not limit the scope of the present invention.

As illustrated inFIG.19, the information processing device90includes a processor91, a main storage device92, an auxiliary storage device93, an input/output interface95, and a communication interface96. InFIG.19, the interface is abbreviated as an interface (I/F). The processor91, the main storage device92, the auxiliary storage device93, the input/output interface95, and the communication interface96are data-communicably connected to each other via a bus98. The processor91, the main storage device92, the auxiliary storage device93, and the input/output interface95are connected to a network such as the Internet or an intranet via the communication interface96.

The processor91develops the program stored in the auxiliary storage device93or the like in the main storage device92and executes the developed program. In the present example embodiment, a software program installed in the information processing device90may be used. The processor91executes processing by the control system according to the present example embodiment.

The main storage device92has an area in which a program is developed. The main storage device92may be a volatile memory such as a dynamic random access memory (DRAM). A nonvolatile memory such as a magnetoresistive random access memory (MRAM) may be configured and added as the main storage device92.

The auxiliary storage device93stores various pieces of data. The auxiliary storage device93includes a local disk such as a hard disk or a flash memory. Various pieces of data may be stored in the main storage device92, and the auxiliary storage device93may be omitted.

The input/output interface95is an interface that connects the information processing device90with a peripheral device. The communication interface96is an interface that connects to an external system or a device through a network such as the Internet or an intranet in accordance with a standard or a specification. The input/output interface95and the communication interface96may be shared as an interface connected to an external device.

An input device such as a keyboard, a mouse, or a touch panel may be connected to the information processing device90as necessary. These input devices are used to input information and settings. When the touch panel is used as the input device, the display screen of the display device may also serve as the interface of the input device. Data communication between the processor91and the input device may be mediated by the input/output interface95.

The information processing device90may be provided with a display device that displays information. In a case where a display device is provided, the information processing device90preferably includes a display control device (not illustrated) that controls display of the display device. The display device may be connected to the information processing device90via the input/output interface95.

The above is an example of a hardware configuration for enabling processing by the control system according to each example embodiment. The hardware configuration ofFIG.19is an example of a hardware configuration for executing the arithmetic processing of the control system according to each example embodiment, and does not limit the scope of the present invention. A program for causing a computer to execute processing of the control system according to each example embodiment is also included in the scope of the present invention. A recording medium in which the program according to each example embodiment is recorded is also included in the scope of the present invention. The recording medium can be achieved by, for example, an optical recording medium such as a compact disc (CD) or a digital versatile disc (DVD). The recording medium may be achieved by a semiconductor recording medium such as a Universal Serial Bus (USB) memory or a secure digital (SD) card, a magnetic recording medium such as a flexible disk, or another recording medium.

The components of the control system of each example embodiment can be combined in any manner. The components of the control system of each example embodiment may be achieved by software or may be achieved by a circuit.

While the present invention is described with reference to example embodiments thereof, the present invention is not limited to these example embodiments. Various modifications that can be understood by those of ordinary skill in the art can be made to the configuration and details of the present invention within the scope of the present invention.

This application is based upon and claims the benefit of priority from Japanese patent application No. 2020-113680, filed on Jul. 1, 2020, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

3communication device10,20,40light receiving device11,21sensor array12,22lens13,23reception unit15first processing circuit16control circuit17selector18second processing circuit35light transmitting unit37light transmitting control unit110,210light receiver151high-pass filter153amplifier155integrator211light pipe320light source321emitter323collimator330spatial light modulator340projection optical system346Fourier transform lens347aperture348projection lens371light transmission condition storage unit372light transmission condition setting unit373modulator control unit374light source drive unit