Patent Description:
As a system that acquires three-dimensional (3D) images (information on the depth of an object surface/ depth information) and measures the distance to an object, a structured light method using a dynamic projector and a dynamic vision camera has been proposed (for example, refer to PTL <NUM>). In the structured light method, the dynamic projector projects dot light having a predetermined pattern to a measurement target/an object, and distortion of the pattern is analyzed on the basis of the result of imaging performed by the dynamic vision camera to acquire the depth information/the distance information.

PTL <NUM> described above discloses a technique in which a vertical cavity surface emitting laser (VCSEL) is used as the dynamic projector serving as a light source, and an event detection sensor called a dynamic vision sensor (DVS) is used as the dynamic vision camera serving as a light receiving unit. The event detection sensor is a sensor that detects the fact that a change in luminance of a pixel photoelectrically converting incident light has exceeded a predetermined threshold as an event. "<NPL>) discloses usage of event based vision sensors in 3D depth estimation techniques using structured light.

Post published document <CIT> discloses a system that includes a processor, a light source controlled by the processor and configured to emit a light, and an event based vision sensor controlled by the processor. The sensor includes a plurality of pixels. At least one of the plurality of pixels includes a photosensor configured to detect incident light and first circuitry configured to output a first signal based on an output from the photosensor. The first signal indicates a change of amount of incident light. The sensor includes a comparator configured to output a comparison result based on the first signal and at least one of a first reference voltage and a second reference voltage. The processor is configured to apply one of the first reference voltage and the second reference voltage to the comparator selectively based on an operation of the light source. "<NPL>) discusses the combination of a dynamic vision sensor with a pulsed line laser to allow fast terrain reconstruction.

Incidentally, the event detection sensor outputs not only event information (a true event) originated from the dot light having the predetermined pattern emitted from the light source to the object as event information but also other information as a noise event. Thus, it is necessary to perform a process of removing the noise event other than the event information originated from the dot light having the predetermined pattern emitted from the light source to the object.

An object of the disclosure is to provide an object recognition system making it possible to remove the information (noise event) other than the event information originated from the dot light having the predetermined pattern emitted from the light source to the object and thereby reduces the loads on subsequent signal processing, a method of signal processing performed by the object recognition system, and an electronic apparatus including the object recognition system.

This is achieved by the claimed subject-matter, which defines the present invention. Embodiments not covered by the claimed subject-matter do not form part of the invention.

In the following, some configurations for implementing the technology according to the disclosure (hereinafter referred to as "embodiments") are described in detail with reference to the drawings. The technology of the disclosure should not be limited to the embodiments. In the following description, the same components or components having the same function are denoted by the same reference numerals, and duplicated descriptions thereof are omitted. It is to be noted that the description is made in the following order.

For an object recognition system and an electronic apparatus according to the disclosure, an event detection sensor is configured to detect one dot light beam in units of a plurality of pixels adjacent to each other, and when the plurality of pixels adjacent to each other reads an event within a certain period of time, the signal processor may read the event as event information originated from the dot light having a predetermined pattern.

For the object recognition system and the electronic apparatus according to the disclosure including the configurations described above, the signal processor may read the event information originated from the dot light having the predetermined pattern from the combination of units each including the plurality of pixels in which the one dot light beam is to be detected. Additionally, the combination of the units each including the plurality of pixels may be a combination of a plurality of units adjacent to each other at an interval corresponding to the one dot light beam in a row direction, a column direction, or a diagonal direction of a pixel array matrix.

Further, for the object recognition system and the electronic apparatus according to the disclosure including the preferred configurations described above, the signal processor may change the number of the pixels in one unit in which the one dot light beam is to be detected on the basis of the distance to the object. Specifically, the signal processor may set a relatively small number of the pixels when the distance to the object is smaller than a predetermined threshold, and a relatively large number of the pixels when the distance to the object is larger than the predetermined threshold.

Further, for the object recognition system and the electronic apparatus according to the disclosure including the preferred configurations described above, the signal processor may have a distance measurement function of measuring the distance to the object, and measure the distance to the object using the distance measurement function. Alternatively, the distance to the object may be measured by a proximity sensor.

Further, for the object recognition system and the electronic apparatus according to the disclosure including the preferred configurations described above, the light source may preferably include a surface-emitting semiconductor laser, and the surface-emitting semiconductor laser may be preferably a vertical cavity surface.

Further, the object recognition system and the electronic apparatus according to the disclosure including the preferred configurations described above may be used for face recognition in a case where the object is a human face. Additionally, processing for the face recognition involves, in order, detecting a face at a certain position using a vertical cavity surface emitting laser serving as the light source and the event detection sensor, performing processing of recognizing features of the face detected, recognizing the shape of the face recognized, and performing processing of recognizing the face whose shape has been recognized.

The object recognition system to which the technology according to the disclosure is applied includes a combination of a light source and an event detection sensor and uses a structured light method. The light source is a group of point light sources and configured to control emission/non-emission on a point light source basis. The event detection sensor detects. Additionally, the object recognition system to which the technology according to the disclosure is applied includes a function of acquiring three-dimensional (3D) images and a function of measuring the distance to the object. Using the structured light method, 3D images are acquired by identifying from which point light source a point image (spotlight) and the coordinates of the point image are projected through pattern matching.

Having the function of acquiring 3D images, the object recognition system to which the technology according to the disclosure is applied may be referred to as a three-dimensional image acquiring system. Having the function of measuring the distance to the object, the object recognition system to which the technology according to the disclosure is applied may be referred to as a ranging system. Further, in a case where the object is a human face, for example, the object recognition system to which the technology according to the disclosure is applied may be used for face recognition and thus be referred to as a face recognition system.

<FIG> is a schematic diagram illustrating an exemplary system configuration of the object recognition system to which the technology according to the disclosure is applied. <FIG> is a block diagram illustrating an exemplary circuit configuration of the object recognition system.

An object recognition system <NUM> to which the technology according to the disclosure is applied includes a surface-emitting semiconductor laser such as a vertical cavity surface emitting laser (VCSEL) <NUM> as a light source that includes a group of point light sources and emits dot light beams having a predetermined pattern to the object. The object recognition system <NUM> further includes an event detection sensor <NUM> called a dynamic vision sensor (DVS) as a light receiving unit. It is to be noted that, as the light source emitting dot light having a predetermined pattern to the object, a general edge-emitting semiconductor laser (LD) may be exemplified in addition to the vertical cavity surface emitting laser (VCSEL).

The vertical cavity surface emitting laser <NUM> is configured to control emission/non-emission on a point light source basis. The vertical cavity surface emitting laser <NUM> projects dot light beams having, for example, a predetermined pattern to an object <NUM>. The event detection sensor <NUM> has sensitivity with respect to infrared light (IR), receives a dot light beam reflected by the object <NUM>, and detects the fact that a change in luminance of a pixel has exceeded a predetermined threshold as an event. The event detection sensor <NUM> is a sensor making it possible to achieve increase the speed and reduce the amount of data and electric consumption by reading a signal of the pixel exhibiting the change in luminance.

The object recognition system <NUM> to which the technology according to the disclosure is applied includes a system controller <NUM>, a light source driver <NUM>, a sensor controller <NUM>, a signal processor <NUM>, a light source-side optical system <NUM>, and a camera-side optical system <NUM> as well as the vertical cavity surface emitting laser (VCSEL) <NUM> and the event detection sensor (DVS) <NUM>. Details of the vertical cavity surface emitting laser <NUM> and the event detection sensor <NUM> will be described later.

The system controller <NUM> is configured by a processor (CPU), for example. The system controller <NUM> drives the vertical cavity surface emitting laser <NUM> via the light source driver <NUM>, and drives the event detection sensor <NUM> via the sensor controller <NUM>. To drive the vertical cavity surface emitting laser <NUM> and the event detection sensor <NUM>, the system controller <NUM> preferably controls the vertical cavity surface emitting laser <NUM> and the event detection sensor <NUM> by synchronizing them.

The arrangement of the point light sources (dots) <NUM> in the vertical cavity surface emitting laser <NUM> is described. In the object recognition system <NUM> to which the technology according to the disclosure is applied, the point light sources <NUM> in the vertical cavity surface emitting laser <NUM> are arranged in two-dimensional arrays (matrix) provided at a constant pitch, as illustrated in <FIG>. The arrangement is a so-called array-dot arrangement.

For the object recognition system <NUM> including the combination of the vertical cavity surface emitting laser <NUM> and the event detection sensor <NUM>, the point light sources <NUM> in the vertical cavity surface emitting laser <NUM> are sequentially turned on, and the event detection sensor <NUM> records time stamps of the events, i.e., time information indicating relative time of the occurrence of the events (timing information). Referring to the timing information, it is possible to easily identify from which point light source <NUM> the image is projected.

The number of the point light sources <NUM> provided in the array-dot arrangement is larger than that in a so-called random-dot arrangement illustrated in <FIG>, in which the point light sources <NUM> are arranged in a specific manner without repetition to have a feature in a spatial direction. The array-dot arrangement is thus advantageous in increasing the resolution of distance images that depends on the number of the point light sources <NUM>. Herein, the term "distance image" refers to an image from which the information on the distance to the object is acquired.

Incidentally, in the case of the random-dot arrangement, it is difficult to increase the number of the point light sources <NUM> while the specific feature of the arrangement pattern of the point light sources <NUM> is maintained. This hinders an increase in the resolution of the distance image that depends on the number of the point light sources <NUM>. However, the arrangement of the point light sources <NUM> in the vertical cavity surface emitting laser <NUM> in the object recognition system <NUM> to which the technology according to the disclosure is applied should not be limited to the array-dot arrangement and may be the random-dot arrangement.

The vertical cavity surface emitting laser <NUM> is a surface emitting light source configured to control emission/non-emission on a point light source <NUM> basis under the control of the system controller <NUM>. Accordingly, the vertical cavity surface emitting laser <NUM> makes it possible to irradiate the entire object with light and irradiate part of the object with dot light with a desired pattern by dot irradiation on a point light source basis or line irradiation on a pixel column basis.

Incidentally, the structured light method may involve irradiating the object (distance measurement target) with light from the plurality of point light sources <NUM> at different angles, and reading the light reflected from the object to recognize the shape of the object.

Described next is the event detection sensor <NUM> that detects the fact that a change in luminance of a pixel has exceeded a predetermined threshold as an event.

<FIG> is a block diagram illustrating an exemplary configuration of the event detection sensor according to a first configuration example. The event detection sensor according to the first configuration example may be used as the event detection sensor <NUM> in the object recognition system <NUM>.

As illustrated in <FIG>, the event detection sensor <NUM> according to the first configuration example is an asynchronous event detection sensor called a DVS. The event detection sensor <NUM> includes a pixel array unit <NUM>, a drive unit <NUM>, an arbiter unit (arbitration unit) <NUM>, a column processing unit <NUM>, and a signal processing unit <NUM>.

In the pixel array unit <NUM> of the event detection sensor <NUM> having the configuration described above, multiple pixels <NUM> are arranged in two-dimensional matrix (arrays). To the respective pixel arrays in the pixel array matrix, a vertical signal line VSL described below are connected.

Each of the multiple pixels <NUM> generates an analog signal having a voltage corresponding to a photocurrent as a pixel signal. Additionally, each of the multiple pixels <NUM> detects the presence or absence of an address event on the basis of the determination as to whether or not the amount of change in photocurrent has exceeded a predetermined threshold. When the address event is generated, the pixel <NUM> outputs a request to the arbiter unit <NUM>.

The drive unit <NUM> outputs the pixel signal generated by each pixel <NUM> to the column processing unit <NUM> by driving the multiple pixels <NUM>, respectively.

The arbiter unit <NUM> arbitrates the request from each of the multiple pixels <NUM> and send a response based on the result of arbitration to the pixel <NUM>. When receiving the response from the arbiter unit <NUM>, the pixel <NUM> supplies a detection signal indicating the detection result (a detection signal of the address event) to the drive unit <NUM> and the signal processing unit <NUM>. The detection signals may be read from the pixels <NUM> in units of a plurality of columns.

The column processing unit <NUM> includes an analog-digital converter, for example. The column processing unit <NUM> performs processing of converting an analog signal outputted from each pixel column of the pixels <NUM> in the pixel array unit <NUM> into a digital signal. Thereafter, the column processing unit <NUM> supplies the digital signal to the signal processing unit <NUM> after the analog-digital conversion.

The signal processing unit <NUM> performs predetermined signal processing such as correlated double sampling (CDS) processing or image recognition processing on the digital signals supplied from the column processing unit <NUM>. Thereafter, the signal processing unit <NUM> supplies data indicating the result of the processing and the detection signal supplied from the arbiter unit <NUM> to a recording unit <NUM> (refer to <FIG>) via a signal line <NUM>.

<FIG> is a block diagram illustrating an exemplary configuration of the pixel array unit <NUM> in the event detection sensor <NUM> according to the first configuration example.

In the pixel array unit <NUM> including the multiple pixels <NUM> arranged in two-dimensional matrix, each of the multiple pixels <NUM> includes a light receiving unit <NUM>, a pixel signal generating unit <NUM>, and an address event detection unit <NUM>.

The light receiving unit <NUM> in the pixel <NUM> having the configuration described above generates a photocurrent by photoelectrically converting incident light. Thereafter, the light receiving unit <NUM> supplies the photocurrent generated by the photoelectrical conversion to the pixel signal generating unit <NUM> or the address event detection unit <NUM> under the control of the drive unit <NUM> (refer to <FIG>).

The pixel signal generating unit <NUM> generates a signal of voltage corresponding to the photocurrent supplied from the light receiving unit <NUM> as a pixel signal SIG, and supplies the generated pixel signal SIG to the column processing unit <NUM> (refer to <FIG>) via the vertical signal line VSL.

The address event detection unit <NUM> detects the presence or absence of the address event on the basis of the determination as to whether or not the amount of change in photocurrent from the corresponding light receiving unit <NUM> has exceeded a predetermined threshold. The address event includes an on-event that the amount of change in photocurrent has exceeded an upper limit threshold and an off-event that the amount of change has fallen below a lower limit threshold, for example. Further, the detection signal of the address event includes one bit indicating the result of detection of the on-event, and one bit indicating the result of detection of the off-event, for example. It is to be noted that the address event detection unit <NUM> may be configured to detect only the on-event.

When the address event is generated, the address event detection unit <NUM> supplies the arbiter unit <NUM> (refer to <FIG>) with a request for sending the detection signal of the address event. When receiving the response to the request from the arbiter unit <NUM>, the address event detection unit <NUM> supplies the detection signal of the address event to the drive unit <NUM> and the signal processing unit <NUM>.

<FIG> is a circuit diagram illustrating an exemplary circuit configuration of the pixel <NUM> in the event detection sensor <NUM> according to the first configuration example. As described above, each of the multiple pixels <NUM> includes the light receiving unit <NUM>, the pixel signal generating unit <NUM>, and the address event detection unit <NUM>.

The light receiving unit <NUM> in the pixel <NUM> having the configuration described above includes a light receiving element (photoelectric transducer) <NUM>, a transfer transistor <NUM>, and an overflow gate (OFG) transistor <NUM>. As the transfer transistor <NUM> and the OFG transistor <NUM>, an N-type metal oxide semiconductor (MOS) transistor is used, for example. The transfer transistor <NUM> and the OFG transistor <NUM> are coupled in series to each other.

The light receiving element <NUM> is coupled between a common connection node N<NUM> of the transfer transistor <NUM> and the OFG transistor <NUM> and a ground. The light receiving element <NUM> photoelectrically converts incident light to generate electric charge in the amount corresponding to the amount of incident light.

To a gate electrode of the transfer transistor <NUM>, a transfer signal TRG is supplied from the drive unit <NUM> illustrated in <FIG>. In response to the transfer signal TRG, the transfer transistor <NUM> supplies the electric charge generated by the photoelectrically conversion at the light receiving element <NUM> to the pixel signal generating unit <NUM>.

To a gate electrode of the OFG transistor <NUM>, a control signal OFG is supplied from the drive unit <NUM>. In response to the control signal OFG, the OFG transistor <NUM> supplies the electric signal generated by the light receiving element <NUM> to the address event detection unit <NUM>. The electric signal supplied to the address event detection unit <NUM> is a photocurrent including electric charge.

The pixel signal generating unit <NUM> includes a reset transistor <NUM>, an amplification transistor <NUM>, a selection transistor <NUM>, and a floating diffusion layer <NUM>. For example, an N-type MOS transistor is used as the reset transistor <NUM>, the amplification transistor <NUM>, and the selection transistor <NUM>.

The light receiving unit <NUM> supplies the electric charge generated by the photoelectrical conversion at the light receiving element <NUM> to the pixel signal generating unit <NUM> via the transfer transistor <NUM>. The electric charge supplied from the light receiving unit <NUM> accumulates in the floating diffusion layer <NUM>. The floating diffusion layer <NUM> generates a voltage signal corresponding to the amount of electric charge accumulated. That is, the floating diffusion layer <NUM> converts electric charge into voltage.

The reset transistor <NUM> is coupled between a power line of a power voltage VDD and the floating diffusion layer <NUM>. To a gate electrode of the reset transistor <NUM>, a reset signal RST is supplied from the drive unit <NUM>. In response to the reset signal RST, the reset transistor <NUM> initializes (resets) the amount of electric charge in the floating diffusion layer <NUM>.

The amplification transistor <NUM> and the selection transistor <NUM> are coupled in series between the power line of the power voltage VDD and the vertical signal line VSL. The amplification transistor <NUM> amplifies the voltage signal generated by the electric charge voltage conversion at the floating diffusion layer <NUM>.

To a gate electrode of the selection transistor <NUM>, a selection signal SEL is supplied from the drive unit <NUM>. In response to the selection signal SEL, the selection transistor <NUM> outputs the voltage signal amplified by the amplification transistor <NUM> to the column processing unit <NUM> (refer to <FIG>) via the vertical signal line VSL as a pixel signal SIG.

In the event detection sensor <NUM> according to the first configuration example including the pixel array unit <NUM> having the two-dimensional arrays of the pixels <NUM> with the configuration described above, the drive unit <NUM> drives the OFG transistor <NUM> by supplying the control signal OFG to the OFG transistor <NUM> of the light receiving unit <NUM> when the controller <NUM> illustrated in <FIG> instructs to start the detection of the address event, so that the OFG transistor <NUM> supplies a photocurrent to the address event detection unit <NUM>.

When the address event is detected by any of the pixels <NUM>, the drive unit <NUM> turns off the OFG transistor <NUM> of the pixel <NUM> so that the OFG transistor <NUM> stops supplying the photocurrent to the address event detection unit <NUM>. Thereafter, the drive unit <NUM> drives the transfer transistor <NUM> by supplying the transfer signal TRG to the transfer transistor <NUM> so that the transfer transistor <NUM> transfers the electric charge photoelectrically converted at the light receiving element <NUM> to the floating diffusion layer <NUM>.

As described above, the event detection sensor <NUM> according to the first configuration example including the pixel array unit <NUM> having the two-dimensional arrays of the pixels <NUM> with the configuration described above outputs only the pixel signal of the pixel <NUM> in which the address event has been detected to the column processing unit <NUM>. Accordingly, the electric power consumption and the processing amount in the image processing at the event detection sensor <NUM> are reduced regardless of the presence or absence of the address event compared with the case where pixel signals of all of the pixels are outputted.

It is to be noted that the configuration of the pixel <NUM> described above is an example, and that the configuration of the pixel <NUM> should not be limited to the configuration example. For example, the pixel may have a configuration in which the pixel signal generating unit <NUM> is not provided. In the case of this pixel configuration, the OFG transistor <NUM> may be omitted in the light receiving unit <NUM>, and the transfer transistor <NUM> may have the function of the OFG transistor <NUM>.

<FIG> is a block diagram illustrating a first configuration example of the address event detection unit <NUM> in the event detection sensor <NUM> according to the first configuration example. As illustrated in <FIG>, the address event detection unit <NUM> according to the configuration example includes a current-voltage converting unit <NUM>, a buffer <NUM>, a subtracter <NUM>, a quantizer <NUM>, and a transfer unit <NUM>.

The current-voltage converting unit <NUM> converts the photocurrent from the light receiving unit <NUM> of the pixel <NUM> into a voltage signal having a logarithm of the photocurrent. The current-voltage converting unit <NUM> supplies the voltage signal acquired as the result of the conversion to the buffer <NUM>. The buffer <NUM> performs buffering of the voltage signal supplied from the current-voltage converting unit <NUM> and supplies the signal to the subtracter <NUM>.

The drive unit <NUM> supplies a row drive signal to the subtracter <NUM>. In accordance with the row drive signal, the subtracter <NUM> decreases the level of the voltage signal supplied from the buffer <NUM>. Thereafter, the subtracter <NUM> supplies the voltage signal with a reduced level to the quantizer <NUM>. The quantizer <NUM> quantizes the voltage signal supplied from the subtracter <NUM> into a digital signal, and outputs the digital signal to the transfer unit <NUM> as the detection signal of the address event.

The transfer unit <NUM> transfers the detection signal of the address event supplied from the quantizer <NUM> to the arbiter unit <NUM>, for example. When the address event is detected, the transfer unit <NUM> supplies a request for sending the detection signal of the address event to the arbiter unit <NUM>. Thereafter, when receiving a response to the request from the arbiter unit <NUM>, the transfer unit <NUM> supplies the detection signal of the address event to the drive unit <NUM> and the signal processing unit <NUM>.

Described next are configuration examples of the current-voltage converting unit <NUM>, the subtracter <NUM>, and the quantizer <NUM> in the address event detection unit <NUM>.

<FIG> is a circuit diagram illustrating an exemplary configuration of the current-voltage converting unit <NUM> in the address event detection unit <NUM> according to the first configuration example. As illustrated in <FIG>, the current-voltage converting unit <NUM> according to the example has a circuit configuration including an N-type transistor <NUM>, a P-type transistor <NUM>, and an N-type transistor <NUM>. As these transistors <NUM> to <NUM>, MOS transistors are used, for example.

The N-type transistor <NUM> is coupled between a power line of a power voltage VDD and a signal input line <NUM>. The P-type transistor <NUM> and the N-type transistor <NUM> are coupled in series between the power line of the power voltage VDD and the ground. Additionally, a gate electrode of the N-type transistor <NUM> and an input terminal of the buffer <NUM> illustrated in <FIG> are coupled to a common connection node N<NUM> of the P-type transistor <NUM> and the N-type transistor <NUM>.

A predetermined bias voltage Vbias is applied to a gate electrode of the P-type transistor <NUM>. The P-type transistor <NUM> thereby supplies a constant current to the N-type transistor <NUM>. Photocurrent is inputted from the light receiving unit <NUM> to a gate electrode of the N-type transistor <NUM> via the signal input line <NUM>.

Drain electrodes of the N-type transistor <NUM> and the N-type transistor <NUM> are coupled to a power source side. These circuits are called source followers. The two source followers connected into a loop shape convert the photocurrent from the light receiving unit <NUM> into a voltage signal having a logarithm of the photocurrent.

<FIG> is a circuit diagram illustrating exemplary configurations of the subtracter <NUM> and the quantizer <NUM> in the address event detection unit <NUM> according to the first configuration example.

The subtracter <NUM> according to the example has a configuration including a capacitative element <NUM>, an inverter circuit <NUM>, a capacitative element <NUM>, and a switch element <NUM>.

One terminal of the capacitative element <NUM> is coupled to an output terminal of the buffer <NUM> illustrated in <FIG>, and the other end of the capacitative element <NUM> is coupled to an input terminal of the inverter circuit <NUM>. The capacitative element <NUM> is coupled in parallel to the inverter circuit <NUM>. The switch element <NUM> is coupled between both ends of the capacitative element <NUM>. The drive unit <NUM> supplies the row drive signal to the switch element <NUM> as an opening/closing control signal. In accordance with the row drive signal, the switch element <NUM> opens or closes a path coupling both ends of the capacitative element <NUM>. The inverter circuit <NUM> reverses the polarity of the voltage signal inputted via the capacitative element <NUM>.

When the switch element <NUM> is turned on (in a closed state) in the subtracter <NUM> having the configuration described above, a voltage signal Vinit is inputted to a terminal of the capacitative element <NUM> adjacent to the buffer <NUM>, and the other terminal of the capacitative element <NUM> becomes a virtual ground terminal. The virtual ground terminal has a potential of zero for convenience of explanation. At this time, a charge Qinit accumulated in the capacitative element <NUM> is represented by the following expression (<NUM>): <MAT> where C<NUM> denotes the capacitance of the capacitative element <NUM>. In contrast, a charge accumulated in the capacitative element <NUM> is zero as both ends of the capacitative element <NUM> are shunted.

Next, when the switch element <NUM> is turned off (in an open state) and the voltage at the terminal of the capacitative element <NUM> adjacent to the buffer <NUM> changes to Vafter, a charge Qafter accumulated in the capacitative element <NUM> is represented by the following expression (<NUM>): <MAT>.

In contrast, a charge Q<NUM> accumulated in the capacitative element <NUM> is represented by the following expression (<NUM>): <MAT> where C<NUM> denotes the capacitance of the capacitative element <NUM>, and Vout denotes an output voltage.

At this time, as the total amount of charges of the capacitative element <NUM> and the capacitative element <NUM> do not change, the following expression (<NUM>) is satisfied: <MAT>.

Substituting the expressions (<NUM>) to (<NUM>) to the expression (<NUM>) and deforming the resultant expression yields the following expression (<NUM>): <MAT>.

The expression (<NUM>) represents a subtraction operation of the voltage signal, and the gain of the result of subtraction is represented by C<NUM> / C<NUM>. As the gain is generally required to be maximized, it is preferable to design such that C<NUM> becomes large and C<NUM> becomes small. However, if C<NUM> is too small, a kTC noise can increase and the noise characteristics can deteriorate. Thus, the reduction in capacitance of C<NUM> is limited within such a range that the noise is generated in an acceptable amount. Additionally, as the address event detection unit <NUM> including the subtracter <NUM> in each pixel <NUM> is mounted, the capacitative element <NUM> and the capacitative element <NUM> have constraints on area. In view of them, the capacitance C<NUM> of the capacitative element <NUM> and and the capacitance C<NUM> of the capacitative element <NUM> are determined.

In <FIG>, the quantizer <NUM> includes a comparator <NUM>. The comparator <NUM> receives an output signal from the inverter circuit <NUM>, i.e., a voltage signal from the subtracter <NUM> as an non-inverting (+) input, and receives a predetermined threshold voltage Vth as an inverting (-) input. Thereafter, the comparator <NUM> compares the voltage signal from the subtracter <NUM> with the predetermined threshold voltage Vth, and outputs a signal indicating the result of comparison to the transfer unit <NUM> as the detection signal of the address event.

<FIG> is a block diagram illustrating a second configuration example of the address event detection unit <NUM> in the event detection sensor <NUM> according to the first configuration example. As illustrated in <FIG>, the address event detection unit <NUM> according to the second configuration example includes a storage <NUM> and a control unit <NUM> in addition to the current-voltage converting unit <NUM>, the buffer <NUM>, the subtracter <NUM>, the quantizer <NUM>, and the transfer unit <NUM>.

The storage <NUM> is provided between the quantizer <NUM> and the transfer unit <NUM>. The storage <NUM> stores an output of the quantizer <NUM>, i.e., the results of comparison at the comparator <NUM> on the basis of a sample signal supplied from the control unit <NUM>. The storage <NUM> may be a sampling circuit made of a switch, plastic, or a capacitor, or a digital memory circuit made of a latch or a flip-flop.

The control unit <NUM> supplies the predetermined threshold voltage Vth to the inverting (-) input terminal of the comparator <NUM>. The threshold voltage Vth supplied from the control unit <NUM> to the comparator <NUM> may be varied by time sharing. For example, the control unit <NUM> supplies a threshold voltage Vth1 indicating a threshold voltage corresponding to the on-event that the amount of change in photocurrent has exceeded the upper limit threshold and a threshold voltage Vth2 indicating a threshold voltage corresponding to the off-event that the amount of change in photocurrent has fallen below the lower limit threshold at different timings. This allows the single comparator <NUM> to detect several various kinds of address events.

For example, while the threshold voltage Vth2 corresponding to the off-event is supplied from the control unit <NUM> to the inverting (-) input terminal of the comparator <NUM>, the storage <NUM> may store the results of comparison at the comparator <NUM> using the threshold voltage Vth1 corresponding to the on-event. It is to be noted that the storage <NUM> may be provided inside the pixel <NUM> or outside the pixel <NUM>. Further, the storage <NUM> is not an essential component of the address event detection unit <NUM>. That is, the storage <NUM> may be omitted.

The event detection sensor <NUM> according to the first configuration example described above is an asynchronous event detection sensor that reads the events by an asynchronous reading method. It is to be noted that the event reading method should not be limited to the asynchronous reading method. The event reading method may be a synchronous reading method. An event detection sensor to which a synchronous reading method is applied is an event detection sensor using a scanning method, as with the case of a general imaging apparatus that performs imaging at a predetermined frame rate.

<FIG> is a block diagram illustrating an exemplary configuration of an event detection sensor according to a second configuration example. The event detection sensor according to the second configuration example may be used as the event detection sensor <NUM> in the object recognition system <NUM> to which the technology according to the disclosure is applied, i.e., the event detection sensor using the scanning method.

As illustrated in <FIG>, the event detection sensor <NUM> according to the second configuration example includes the pixel array unit <NUM>, the drive unit <NUM>, the signal processing unit <NUM>, a reading region selecting unit <NUM>, and a signal generating unit <NUM>.

The pixel array unit <NUM> includes the multiple pixels <NUM>. The multiple pixels <NUM> output output signals in response to selection signals from the reading region selecting unit <NUM>. Each of the multiple pixels <NUM> may include the comparator, as illustrated in <FIG>, for example. The multiple pixels <NUM> output output signals corresponding to the amount of change in light intensity. The multiple pixels <NUM> may be arranged in two-dimensional matrix, as illustrated in <FIG>.

The drive unit <NUM> drives each of the multiple pixels <NUM> to output a pixel signal generated at each of the pixels <NUM> to the signal processing unit <NUM>. It is to be noted that the drive unit <NUM> and the signal processing unit <NUM> are circuit units that acquire gray scale information. Thus, in a case where only the event information is to be acquired, the drive unit <NUM> and the signal processing unit <NUM> may be omitted.

The reading region selecting unit <NUM> selects some of the multiple pixels <NUM> included in the pixel array unit <NUM>. For example, the reading region selecting unit <NUM> determines a selected region in accordance with a request from each of the pixels <NUM> of the pixel array unit <NUM>. For example, the reading region selecting unit <NUM> selects any one or more rows included in the two-dimensional matrix structure corresponding to the pixel array unit <NUM>. The reading region selecting unit <NUM> sequentially selects one or more rows in a predetermined cycle.

On the basis of output signals from the pixels selected by the reading region selecting unit <NUM>, the signal generating unit <NUM> generates an event signal corresponding to an active pixel having detected the event among the selected pixels. The event is an event of the change in light intensity. The active pixel is a pixel whose amount of change in light intensity in response to the output signal has exceeded a predetermined threshold or has fallen below the predetermined threshold. For example, the signal generating unit <NUM> compares the output signals of the pixels with a reference signal to detect the active pixel that outputs an output signal larger than or smaller than the reference signal. The signal generating unit <NUM> then generates the event signal corresponding to the active pixel.

The signal generating unit <NUM> may include, for example, a row selection circuit that arbitrates a signal inputted to the signal generating unit <NUM>. Further, the signal generating unit <NUM> is configured not only to output the information on the active pixel having detected the event but also to output the information on a non-active pixel having detected no event.

From the signal generating unit <NUM>, address information of the active pixel having detected the event and time stamp information (e.g., X, Y, and T) are outputted through an output line <NUM>. It is to be noted that the data outputted from the signal generating unit <NUM> may include not only the address information and the time stamp information but also frame format information (e.g., (<NUM>,<NUM>,<NUM>,<NUM>,.

The chip (semiconductor integrated circuit) structure of event detection sensor <NUM> according to the first configuration example or the second configuration example described above may be a laminated chip structure, for example. <FIG> is an exploded perspective view of the event detection sensor <NUM> having the laminated chip structure.

As illustrated in <FIG>, the laminated chip structure, i.e., a so-called laminated structure includes a laminate of at least two chips: a light receiving chip <NUM> serving as a first chip and a detection chip <NUM> serving as a second chip. Each of the light receiving elements <NUM> in the circuit configuration of the pixel <NUM> illustrated in <FIG> are provided on the light receiving chip <NUM>, and all elements other than the light receiving elements <NUM> and elements in the other circuit portions of the pixel <NUM> are provided on the detection chip <NUM>. The light receiving chip <NUM> and the detection chip <NUM> are electrically coupled via a connection portion such as a via, Cu-Cu bonding, or a bump.

It is to be noted that, although the light receiving elements <NUM> are provided on the light receiving chip <NUM> and the elements other than the light receiving elements <NUM> and the elements in the other circuit portions of the pixel <NUM> are provided on the detection chip <NUM> in the configuration example described herein, the configuration example is not restrictive.

For example, in the circuit configuration of the pixel <NUM> illustrated in <FIG>, the elements of the light receiving unit <NUM> may be provided on the light receiving chip <NUM>, and the elements other than the light receiving unit <NUM> and the elements in the other circuit portions of the pixel <NUM> may be provided on the detection chip <NUM>. Further, the elements of the light receiving unit <NUM> and the reset transistor <NUM> and the floating diffusion layer <NUM> of the pixel signal generating unit <NUM> may be provided on the light receiving chip <NUM>, and elements other than these elements may be provided on the detection chip <NUM>. Further, some of the elements included in the address event detection unit <NUM> may be provided on the light receiving chip <NUM> together with the elements of the light receiving unit <NUM>.

Incidentally, the event information outputted from the event detection sensor <NUM> in the object recognition system <NUM> using the structured light method should not be limited to the event information (true event) originated from the dot light having a predetermined pattern (hereinafter also referred to as "dot pattern light" emitted from the vertical cavity surface emitting laser <NUM> to the object. For example, the event information originated from the movement of the object (an animal body) includes other information (hereinafter also referred to as "noise event") when outputted. The noise event (false event) may be, for example, information originated from a change in pattern projected on the object, background light, or a sensor noise, for example.

<FIG> is an image diagram illustrating the event information originated from an animal body and including noise events. <FIG> is an image diagram illustrating the event information (true event) originated from the dot pattern light emitted from the vertical cavity surface emitting laser <NUM> to the object. If the event information outputted from the event detection sensor <NUM> includes the true events and the noise events, it is necessary to perform processing of removing the noises in a subsequent stage. This can place loads on the subsequent signal processing.

The object recognition system <NUM> according to the embodiment of the disclosure makes it possible to reduce the loads on the subsequent signal processing by removing the information other than the event information originated from the dot pattern light (dot light having a predetermined pattern) emitted from the surface-emitting semiconductor laser serving as a light source, e.g., the vertical cavity surface emitting laser <NUM> to the object, i.e., the noise events (false events).

Described below is a specific example of the embodiment for outputting (reading) the event information (true event) originated from the dot pattern light emitted from the vertical cavity surface emitting laser <NUM> to the object and including no noise event (false event).

It is supposed that the noise event is generated independently in each pixel, for example. However, an animal body has a certain size. Thus, the event information originated from the dot pattern light emitted from the vertical cavity surface emitting laser <NUM> to the object is generated across the pixels in a certain region.

Accordingly, in a case where the distance from the event detection sensor <NUM> to the object (i.e., the distance between the object and the event detection sensor <NUM>) is a predetermined distance, one dot light beam is detected in units of four pixels adjacent to each other in Example <NUM>. The four pixels includes two pixels in the row direction by two pixels in the column direction.

However, the number of adjacent pixels in one unit in which one dot light beam is to be detected should not be limited four. In a case where the object recognition system <NUM> according to the present embodiment is used as a face recognition system mounted on a smartphone, for example, the term "predetermined distance" used herein refers to an average distance between the smartphone and the face of a human holding the smartphone in the hand, for example.

Further, in the signal processing according to Example <NUM>, the event information (true event) originated from the dot pattern light emitted from the vertical cavity surface emitting laser <NUM> to the object is read when the four pixels adjacent to each other output an on-event signal indicating that the amount of change in photocurrent from each of the light receiving units <NUM> (refer to <FIG>) has exceeded the upper limit threshold within a certain period of time. Accordingly, in a case where the four pixels adjacent to each other do not output the on-event signal within the certain period of time, the event information is not read as it is determined to be the noise event.

It is to be noted that, although the true event originated from the dot pattern light is read when the four pixels output the on-event signal within the certain period of time, an off-event signal indicating that the amount of change in photocurrent from each of the light receiving units <NUM> has fallen below the lower limit threshold may be outputted in place of the on-event signal.

The signal processing according to Example <NUM> is executed as one of the signal processes performed by the signal processor <NUM> illustrated in FG. Accordingly, when the four pixels adjacent to each other do not output the on-event signal within the certain period of time, the signal processor <NUM> has a filtering function of removing the noise events. An exemplary circuit configuration for implementing the signal processing according to Example <NUM> is illustrated in <FIG>.

In the signal processing according to Example <NUM>, an operation circuit <NUM> is provided in units of four pixels <NUM> adjacent to each other (i.e., two pixels in the row direction by two pixels in the column direction). When the four pixels <NUM> adjacent to each other output the on-event signal (or the off-event signal) within the certain period of time, the operation circuit <NUM> reads the event as the event information (true event) originated from the dot pattern light emitted to the object.

It is to be noted that, although the determination as to whether the event information is true or false is performed by hardware using the operation circuit <NUM> in the present embodiment, this is a mere example. The determination may be performed by a method other than the signal processing using the operation circuit <NUM>. For example, the on-event signals (or the off-event signals) outputted from the pixels <NUM> of the event detection sensor <NUM> may be stored in a memory, and the determination as to whether the event information is true or false may be performed by software in a certain time cycle.

<FIG> illustrates a flowchart of exemplary signal processing performed by the object recognition system according to the disclosure in which the determination is performed by software. First, the signal processor <NUM> acquires the amount of change in photocurrent from each of the light receiving units <NUM> (refer to <FIG>) in units of four pixels adjacent to each other (Step S1), and determines whether the four pixels adjacent to each other output the on-event signal indicating that the amount of change in photocurrent has exceeded the upper limit threshold within the certain period of time (Step S2). If it is determined that the on-event signal is outputted (S2: YES), the event is read as the event information (true event) originated from the dot pattern light emitted to the object (Step S3). Otherwise (S2: NO), the event is removed as the noise event (Step S4).

Example <NUM> is a modification example of Example <NUM>. In the signal processing of Example <NUM>, one dot light beam <NUM> is detected in units of four pixels <NUM> adjacent to each other as illustrated in <FIG>, and the event information (true event) is read in this unit.

In contrast, in the signal processing of Example <NUM>, a plurality of units in which one dot light beam <NUM> is to be detected are combined to detect the event information (true event). Specifically, in the signal processing of Example <NUM>, two units adjacent to each other at an interval corresponding to one dot light beam in the row direction are combined into one unit in which the event information is to be detected, as illustrated in <FIG>, for example. In the case of the combination of units, the event information (true event) is read when an event is detected in four pixels in a first unit, no event is detected in four pixels in the interval, and an event is detected in four pixels in a second unit.

In a case where the object recognition system <NUM> according to the present embodiment is used as a face recognition system, for example, the shift amount of the dot light having a reflection dot pattern based on the dot pattern light emitted to the object is predictable to a certain degree as a human face has a slight unevenness. Thus, according to the signal processing of Example <NUM>, it is possible to remove an event detected at a location shifted by, for example, one pixel from the unit that includes four pixels <NUM> in which one dot light beam is to be detected as a noise event.

It is to be noted that, although the combination of units each including four pixels <NUM> includes two units adjacent to each other at the interval corresponding to one dot light beam in the row direction, the combination may include two units adjacent to each other at the interval corresponding to one dot light beam in the column direction or two units adjacent to each other at the interval corresponding to one dot light beam in both directions. Further, the combination should not be limited to the combination of two units. As with the case of the signal processing of Example <NUM>, the signal processing of Example <NUM> is performed by the signal processor <NUM> illustrated in <FIG>.

In Example <NUM>, the number of pixels included in one unit in which one dot light beam <NUM> is to be detected is changed on the basis of the distance to the object (i.e., the distance between the object and the event detection sensor <NUM>).

Since the object recognition system <NUM> according to the present example embodiment uses the structured light method, the signal processor <NUM> illustrated in <FIG> has a function of measuring the distance to the object. Using the distance measurement function, it is possible to measure the distance between the object and the event detection sensor <NUM>.

It is to be noted that the measurement of the distance between the object and the event detection sensor <NUM> should not be limited to using the distance measurement function of the signal processor <NUM>. Alternatively, a proximity sensor such as a time of flight (ToF) sensor may be used, for example.

<FIG> is a functional block diagram of the signal processor <NUM> for implementing signal processing according to Example <NUM>. <FIG> is a conceptual diagram illustrating the difference in size (dimension) of spotlight incident on the event detection sensor <NUM> due to the difference in distance to the object.

The dot pattern light emitted from the vertical cavity surface emitting laser <NUM> to the object is reflected by the object, and spotlight is incident on the event detection sensor <NUM>. The size (dimensions) of the spotlight becomes relatively small as the object is located closer, and becomes relatively large as the object is located farther.

When the object recognition system <NUM> according to the present embodiment is used as a face recognition system mounted on a smartphone, for example, the size of a light spot reflected by the human face located close to the smartphone is relatively small, and the size of a light spot reflected by the background behind the face is relatively large, as illustrated in <FIG>. In this case, a threshold for removing the noise event is set between the sizes of the two light spots. Accordingly, the light spot reflected by the human face and having a small size is detected as the event information (true event) originated from the dot pattern light, and other light spots are removed as the noise events.

However, the distance to the object, i.e., the distance between the object and the event detection sensor <NUM> is not always constant. For example, the distance differs depending on the user of the smartphone. Thus, in the signal processing according to Example <NUM>, the number of pixels included in one unit in which one dot light beam <NUM> is to be detected is changed on the basis of the distance to the object. The number of pixels in one unit in which one dot light beam <NUM> is to be detected may be regarded as a filtering condition for filtering processing performed by the signal processor <NUM>. That is, in the signal processing according to Example <NUM>, the information on the distance to the object is acquired, and the filtering condition is changed on the basis of the result of acquisition.

As illustrated in <FIG>, a functional unit of the signal processor <NUM> for implementing the signal processing according to Example <NUM> includes a distance measurement unit <NUM>, a filtering condition setting unit <NUM>, and a filtering processing unit <NUM>.

The distance measurement unit <NUM> includes the distance measurement function of the object recognition system <NUM> or a proximity sensor such as a ToF sensor, and measures the distance to the object, i.e., the distance between the object and the event detection sensor <NUM>.

On the basis of the results of measurement by the distance measurement unit <NUM>, the filtering condition setting unit <NUM> sets the filtering condition, i.e., the number of pixels included in one unit in which one dot light beam <NUM> is to be detected. For example, in a case where the distance to the human face is smaller than a predetermined threshold, the number of pixels is set to a relatively small value; for example, four pixels in total, including two pixels adjacent to each other in the row direction by two pixels adjacent to each other in the column direction, are set as the filtering condition. In contrast, in a case where the distance to the human face is larger than the predetermined threshold, the number of pixels is set to a relatively large value; for example, nine pixels in total, including three pixels adjacent to each other in the row direction by three pixels adjacent to each other in the column direction, are set as the filtering condition.

The filtering processing unit <NUM> performs filtering processing on the basis of the filtering condition set by the filtering condition setting unit <NUM>. In the filtering processing, the event information originated from the dot pattern light is read as the true event, and the other event information is removed as the noise event.

In the signal processing according to Example <NUM> described above, the number of pixels included in one unit in which one dot light beam <NUM> is to be detected, i.e., the filtering condition is changed on the basis of the distance to the object (i.e., the distance between the object and the event detection sensor <NUM>). Accordingly, even when the distance to the object changes, it is possible to certainly read the event information originated from the dot pattern light as the true event and remove the other event information as the noise event.

The distance to the object is measured using the distance measurement function of the object recognition system <NUM> or the proximity sensor such as a ToF sensor in the present embodiment; however, it is to be noted that, when the object recognition system <NUM> is mounted on a smartphone, for example, an approximate distance to a human face may be determined on the basis of an average size of a human face without directly measuring the distance.

Accordingly, the shape of the face may be detected on the basis of an output of the event detection sensor <NUM>, and the filtering condition may be set on the basis of the outline size. Specifically, the distance to the face is determined to be relatively short when the outline size of the face is greater than a predetermined threshold, and four pixels adjacent to each other are set as the filtering condition, for example. In contrast, the distance to the face is determined to be relatively long when the outline size of the face is less than or equal to the predetermined threshold, and nine pixels adjacent to each other are set as the filtering condition, for example.

Further, more detailed adaptive control may be achieved by setting different filtering conditions for different regions of the object in the signal processing according to Example <NUM>. For example, in a case where the object recognition system <NUM> is applied to face recognition, the shape of a face is detected on the basis of an output of the event detection sensor <NUM>, and thereafter, different filtering conditions are set to a nose portion located relatively close to the event detection sensor <NUM> and a cheek portion located relatively far from the event detection sensor <NUM>. This achieves more detailed adaptive control.

Example <NUM> is exemplary processing for face recognition in a case where the object recognition system <NUM> is applied to face recognition, for example.

<FIG> is a flowchart illustrating exemplary processing for signal processing according to Example <NUM>, i.e., face recognition. In a case where the function of the system controller <NUM> illustrated in <FIG> is implemented by a processor, the processing is performed by the signal processor <NUM> under the control of the processor of the system controller <NUM>.

The processor of the system controller <NUM> (hereinafter simply referred to as "processor") uses the vertical cavity surface emitting laser <NUM> and the event detection sensor <NUM> to detect an object at a certain position, e.g., a human face in this example (Step S11).

Since the human face is present in a limited region within an imaging range in this object detection processing, only the point light sources <NUM> within a certain region of the pixel arrays in the vertical cavity surface emitting laser <NUM> are operated. In response to this, only the pixels <NUM> including the light receiving elements <NUM> within a certain region of the pixel array in the event detection sensor <NUM> are operated.

As described above, the vertical cavity surface emitting laser <NUM> and the event detection sensor <NUM> are partly operated to perform the distance measurement at low power consumption upon the object detection. It is to be noted that the operation of the event detection sensor <NUM> at low power consumption is achieved by on/off control of the power source in each pixel <NUM>.

The object detection using the vertical cavity surface emitting laser <NUM> and the event detection sensor <NUM> is achieved by, for example, a known triangulation system that measures the distance to the object using a triangulation method.

Next, the processor performs recognition processing of recognizing the features of the face acquired by the object detection (Step S12). In this face recognition processing, the vertical cavity surface emitting laser <NUM> operates the point light sources <NUM> in a wide-angle region rather than a partial region. In contrast, the event detection sensor <NUM> operates the pixels <NUM> including the light receiving elements <NUM> in a certain region of interest (ROI). Additionally, in the face recognition processing, the event detection sensor <NUM> performs a gray scale reading operation using the pixel signal generating unit <NUM> illustrated in <FIG>. It is possible to acquire a high-resolution image by the gray-scale reading operation.

As described above, in the face recognition processing in Step S12, a high-resolution image of the face obtained by the object detection is acquired by the wide-angle irradiation by the vertical cavity surface emitting laser <NUM> and the gray-scale reading operation by the event detection sensor <NUM>. Thereafter, the feature points of the face are extracted for the face recognition on the basis of the high-resolution image.

The face recognition uses a pattern recognition technique involving machine learning such as a neural network. For example, a technique involving comparing the feature points of a face provided as teacher's data with the feature points of a captured face image is used to perform the recognition processing.

Next, the processor performs shape recognition on the basis of the face recognized (Step S13). In this shape recognition processing, the shape of the face is recognized by a ranging system using a structured light method. Specifically, the vertical cavity surface emitting laser <NUM> configured to control emission/non-emission of each pixel emits pattern light on a time-series basis to the face recognized by dot emission or line emission.

In contrast, the event detection sensor <NUM> uses the event data outputted from the address event detection unit <NUM> illustrated in <FIG> or <FIG>. The event data includes the time stamp that is time information indicating relative time when the event occurs. The location where the event has occurred is identified on the basis of the time stamp or the time information.

As described above, in the shape recognition processing in Step S13, the shape of the face is recognized by chronological high-definition matching in a spatial direction using the vertical cavity surface emitting laser <NUM> configured to control emission/non-emission of each pixel and the event detection sensor <NUM> that reads the location where the event has occurred.

Lastly, the processor recognizes the face acquired by the shape recognition using a known face recognition technique (Step S14). For example, the known face recognition technique involves extracting multiple feature points of the face image, and checking the feature points against feature points preliminarily registered to perform the face recognition.

The signal processing according to Example <NUM> described above is a process for the face recognition performed by the object recognition system <NUM> including a combination of the vertical cavity surface emitting laser <NUM> and the event detection sensor <NUM> and using the structured light method. The object recognition system <NUM> makes it possible to remove the noise events and read only the event information originated from the dot pattern light emitted to the face. Thus, according to the signal processing of Example <NUM>, it is possible to perform the face recognition processing more certainly.

Although the technology according to the disclosure is described above referring to some preferred embodiments, the technology according to the disclosure should not be limited to these embodiments. The configuration and structure of the object recognition system described in the foregoing embodiments are examples and may be changed as appropriate.

The object recognition system according to the disclosure described above may be used as a face recognition system mounted in various electronic apparatuses having a face recognition function. Examples of the electronic apparatuses having the face recognition function may include mobile devices such as smartphones, tablets, and personal computers.

It is to be noted that the apparatus (system) including the object recognition system of the disclosure as the face recognition system should not be limited to these mobile devices, and may be other devices than the mobile devices. For example, the apparatus may be a security system or an automobile that unlocks a door by face recognition.

Here, a smartphone is described as an example of the electronic apparatus of the disclosure to which the object recognition system of the disclosure is applicable. <FIG> is an external view, seen in the front direction, of a smartphone in which the object recognition system according to any one of the embodiments described above is mounted as the face recognition system.

A smartphone <NUM> according to the present example includes a casing <NUM> and a display unit <NUM> on the front side of the casing <NUM>. The smartphone <NUM> in which the object recognition system according to any one of the embodiments described above is mounted as the face recognition system includes a light emitting unit <NUM> and a light receiving unit <NUM> at a front upper portion of the casing <NUM>. An exemplary arrangement of the light emitting unit <NUM> and the light receiving unit <NUM> illustrated in <FIG> is an example and not restrictive.

The smartphone <NUM>, which is an example mobile device having the configuration described above, includes the vertical cavity surface emitting laser (VCSEL) <NUM> described above as the light emitting unit <NUM>, and the event detection sensor (DVS) <NUM> in the object recognition system <NUM> as the light receiving unit <NUM>. That is, the smartphone <NUM> according to the present example includes the object recognition system <NUM> according to any of the embodiments described above, and is produced as a smartphone having the face recognition function.

Claim 1:
An object recognition system (<NUM>) comprising:
a light source (<NUM>) for emitting dot light having a predetermined pattern to an object (<NUM>);
an event detection sensor (<NUM>) for receiving the dot light having the predetermined pattern reflected from the object (<NUM>) and for detecting a fact that a change in luminance of a pixel has exceeded a predetermined threshold as an event; and
a signal processor (<NUM>) for performing a process of removing information other than event information originated from the dot light emitted from the light source (<NUM>) and having the predetermined pattern among event information detected by the event detection sensor (<NUM>), wherein, the event detection sensor (<NUM>) is configured to detect one dot light beam in units of a plurality of pixels adjacent to each other, and where the plurality of pixels adjacent to each other detects the event within a certain period of time, the signal processor reads the event as the event information originated from the dot light having the predetermined pattern.