Patent Publication Number: US-2023145578-A1

Title: Distance measurement device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a distance measurement device. 
     BACKGROUND ART 
     For automated driving, face authentication, depth information detection and the like, the Time of Flight (ToF) method, which performs distance measurement in a contactless manner on the basis of the time of flight of light, is receiving attention. The ToF method includes a direct ToF method to directly measure the time of flight of pulsed optical signals and an indirect ToF method to indirectly measure a distance by using a phase difference between optical signals. 
     The direct ToF method is suitable for measuring a relatively long distance, while the indirect ToF method is suitable for measuring a short distance of several tens of cm or less. Recently, in an increasing number of cases, smartphones are provided with a sensor of the indirect ToF method for face recognition and acquiring depth information and the like. 
     The indirect ToF method involves more complicated signal processing than the direct ToF method, and often measures a distance by software processing. For example, in smartphones provided with a sensor of the indirect ToF method, it is typical that a signal processing processor (hereinafter, DSP: Digital Signal processor) performs distance measurement by software processing at an instruction from an application processor (AP). 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Application Laid-Open No. 2019-191119 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, a DSP provided to mobile devices such as smartphones has lower processing performance than a CPU for a personal computer (PC) or the like, and generates heat when performing signal processing with high load such as distance measurement processing. Mobile devices such as smartphones are provided with a temperature sensor, and when the temperature inside the enclosure rises too much, processing for relieving the processing load of the DSP by decreasing the frame rate is automatically performed. This causes a problem that it takes time for signal processing such as distance measurement. 
     Furthermore, performing signal processing such as distance measurement by software processing causes a problem of increase in power consumption. Mobile devices such as smartphones are driven by batteries, and increased power consumption lowers their usability. 
     Thus, the present disclosure provides a distance measurement device capable of performing signal processing such as distance measurement with high speed and low power consumption. 
     Solutions to Problems 
     In order to solve the problem described above, according to the present disclosure, a distance measurement device is provided, including: 
     a first semiconductor element including a first light-reception section that receives light and performs photoelectric conversion to generate an electric signal; 
     a second semiconductor element including a distance calculation section that performs calculation of distance information regarding a distance to an object on the basis of the electric signal; and 
     a third semiconductor element including a signal processing section that performs predetermined information processing on the basis of an output signal of the distance calculation section. 
     The second semiconductor element may include a bypass circuit, and 
     the signal processing section may perform the information processing on the electric signal output via the bypass circuit. 
     The bypass circuit may output the electric signal output from the first semiconductor element without performing processing at the distance calculation section. 
     The first semiconductor element may output the electric signal of multiple phases in which a phase difference changes with the distance to the object, and 
     the distance calculation section may calculate the distance information on the basis of the electric signal of the multiple phases. 
     The distance calculation section may calculate the distance information from a time difference between a timing at which a light-emitting section emits light and a timing at which the first light-reception section receives light. 
     A light-emitting section that emits light in response to control from the first light-reception section may be included. 
     The first semiconductor element and the light-emitting section may be implemented on a same substrate. 
     A first substrate on which the first semiconductor element is implemented, and 
     a second substrate on which the second semiconductor element is implemented are included, and 
     the first substrate and the second substrate may be laminated on each other. 
     The first substrate and the second substrate may be laminated together by a Chip on Chip (CoC) method, a Chip on Wafer (CoW) method, or a Wafer on Wafer (WoW) method. 
     A memory implemented on the second substrate and used by the distance calculation section for performing the calculation of the distance information may be included. 
     A third substrate on which a memory used by the distance calculation section for performing the calculation of the distance information is implemented may be included, and 
     the first substrate, the second substrate, and the third substrate may be laminated in a predetermined order. 
     The memory may be a volatile memory or a rewritable non-volatile memory. 
     The distance calculation section may include a digital circuit that performs digital signal processing on the electric signal including the calculation of the distance information. 
     A fourth semiconductor element including a second light-reception section that receives light and performs photoelectric conversion to generate an electric signal may be included. 
     An electric signal output from the second light-reception section may be input to the third semiconductor element without passing through the second semiconductor element. 
     The third semiconductor element may control whether or not to synchronize an electric signal output from the first light-reception section and an electric signal output from the second light-reception section. 
     The fourth semiconductor element may transmit, to the first semiconductor element and the second semiconductor element, a synchronization signal synchronized with an electric signal output from the second light-reception section. 
     The first light-reception section and the second light-reception section may receive light of respective different wavelength bands. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1 A  is a block diagram showing a schematic configuration of a distance measurement device according to an embodiment. 
         FIG.  1 B  is a block diagram showing a schematic configuration of a distance measurement device including a light-emitting section. 
         FIG.  2    is a block diagram showing an example of an internal configuration of a second semiconductor element in  FIG.  1   . 
         FIG.  3    is a block diagram showing a basic configuration of the distance measurement device according to the present embodiment. 
         FIG.  4 A  is a diagram showing two semiconductor devices separately implemented on a substrate. 
         FIG.  4 B  is a diagram showing a first example of a laminated chip. 
         FIG.  4 C  is a diagram showing a second example of a laminated chip. 
         FIG.  4 D  is a diagram showing a third example of a laminated chip. 
         FIG.  4 E  is a diagram showing a fourth example of a laminated chip. 
         FIG.  5    is a diagram showing an example of electronic equipment according to the present disclosure. 
         FIG.  6    is a diagram showing an example of electronic equipment according to the present disclosure. 
         FIG.  7    is a block diagram showing an example of a schematic configuration of a vehicle control system. 
         FIG.  8    is an illustrative diagram showing an example of installation positions of a vehicle external information detection section and image-capturing sections. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Embodiments of a distance measurement device will be described below with reference to the drawings. Although main components of the distance measurement device will be mainly described below, the distance measurement device may include components and functions that are not shown in the drawings or described. The following description does not exclude components and functions that are not shown in the drawings or described. 
       FIG.  1 A  is a block diagram showing a schematic configuration of a distance measurement device  10  according to an embodiment. The distance measurement device  10  in  FIG.  1 A  includes a first semiconductor element  11 , a second semiconductor element  12 , and a third semiconductor element  13 . 
     The first semiconductor element  11  includes a first light-reception section  11   a  that receives light and performs photoelectric conversion to generate an electric signal. The first semiconductor element  11  may output a Phase signal of multiple phases in which a phase difference changes with the distance to an object, that is, a Phase signal of the indirect ToF method. Alternatively, the first semiconductor element  11  may output a signal indicating a time difference between a timing at which a light-emitting section as described later emits light and a timing at which the first light-reception section  11   a  receives light. 
     The second semiconductor element  12  includes a signal processing circuit  12   a  that performs signal processing including calculation of distance information regarding the distance to the object on the basis of the electric signal output from the first semiconductor element  11 . The second semiconductor element  12  may also include a bypass path (bypass circuit) as described later that outputs the electric signal output from the first semiconductor element  11  without performing signal processing at the signal processing circuit  12   a . For example, in a case where the processing capability of the second semiconductor element  12  is inferior to that of the third semiconductor element  13 , and it is necessary to perform signal processing with excessively high processing load for the second semiconductor element  12 , the electric signal output from the first semiconductor element  11  is transmitted to the third semiconductor element  13  through the bypass path. Therefore, the signal processing can be performed by the third semiconductor element  13 , which has higher processing capability than the second semiconductor element  12 , instead of the second semiconductor element  12 . 
     The third semiconductor element  13  performs predetermined information processing on the basis of the distance information calculated by the second semiconductor element  12 . The third semiconductor element  13  may have higher signal processing functionality than the signal processing circuit  12   a  in the second semiconductor element  12 . A specific example of the third semiconductor element  13  is a high-performance application processor (AP) or a central processing unit (CPU). 
     The specific details of the information processing performed by the third semiconductor element  13  are arbitrary. For example, the third semiconductor element  13  may generate a distance image with colors and luminance varying with the distance to the object on the basis of the distance information calculated by the second semiconductor element  12 . Alternatively, the third semiconductor element  13  may estimate gesture actions of the object on the basis of the distance information. Alternatively, the third semiconductor element  13  may generate a three-dimensional image on the basis of the distance information. 
     In the example of  FIG.  1 A , the first semiconductor element  11  and the second semiconductor element  12  are implemented on a common substrate (hereinafter, a first substrate  21 ), and the third semiconductor element  13  is implemented on a second substrate (second module)  22  arranged at a distance from the first substrate (first module)  21 . The substrate configuration of  FIG.  1 A  is an example, and the first semiconductor element  11 , the second semiconductor element  12  and the third semiconductor element  13  may be implemented on a common substrate. Alternatively, the first semiconductor element  11  and the second semiconductor element  12  may be arranged on separate substrates. 
     As shown in  FIG.  1 A , in addition to the third semiconductor element  13 , a power supply IC  25 , a DRAM chip  26 , a FRASH memory chip  27  and the like may be implemented on the second substrate  22 . The DRAM chip  26  and the FRASH memory  27  may be provided inside the third semiconductor element  13  in some cases. 
     Although the distance measurement device  10  in  FIG.  1 A  does not include a light-emitting section therein, a light-emitting section is needed for performing distance measurement using light, and the light-emitting section is provided separately from the distance measurement device  10  in  FIG.  1 A . The light-emitting section  15  is arranged near the first semiconductor element  11 , for example. By arranging the light-emitting section  15  near the first semiconductor element  11 , reflected light resulting from the reflection of the light emitted from the light-emitting section  15  at the object can be efficiently received by the light-reception section. By separating the distance measurement device  10  and the light-emitting section, a user can substitute or select a light-emitting section that emits light of a desired emission wavelength as necessary. However, a configuration in which the light-emitting section is arranged inside the distance measurement device is also possible. 
       FIG.  1 B  is a block diagram showing a schematic configuration of a distance measurement device  10   a  including a light-emitting section  15 . In the example of  FIG.  1 B , the light-emitting section  15  and the first semiconductor element  11  are arranged on the same auxiliary substrate  26 , and the auxiliary substrate  26  is further implemented on the first substrate  21 . The light-emitting section  15  and the first semiconductor element  11  are implemented on the auxiliary substrate  26 . By implementing the auxiliary substrate  26  on the first substrate  21  as a ToF sensor module in this manner, the manufacturing of the distance measurement device  10 B is facilitated. 
     The first semiconductor element  11  includes a communication unit (not shown) or the like, in addition to including the first light-reception section  11   a  therein. The first semiconductor element  11  has a plurality of input/output terminals. For example, the input/output terminals provided to the first semiconductor element  11  are an I2C terminal, an XVS terminal, an MIPI_Tx terminal, an INCK terminal, an XCLR terminal, an LED_EN terminal, an SPI_Master terminal and the like. 
     The I2C terminal is a terminal for receiving two signals for Inter-Integrated Circuit (I2C) communication from the third semiconductor element  13 . One of the two signals is a clock signal, and the other is a serial signal. In the distance measurement devices  10 ,  10   a  of  FIGS.  1 A and  1 B , the third semiconductor element  13  is a master of the I2C communication, and the first semiconductor element  11  and the second semiconductor element  12  are slaves. Thus, the first semiconductor element  11  and the second semiconductor element  12  perform transmission and reception of the serial signal according to a command from the third semiconductor element  13 . 
     The XVS terminal is a terminal for receiving a synchronization signal. By receiving the synchronization signal at the XVS terminal, the first semiconductor element  11  can operate in synchronization with another semiconductor element (for example, a fourth semiconductor element  14 ) that transmits the synchronization signal. The XVS terminal performs transmission and reception of the synchronization signal in a case of synchronizing a plurality of semiconductor elements with each other. A specific example of the synchronization will be described later. 
     The MIPI_Tx terminal is a terminal compliant with the Mobile Industry Processor Interface (MIPI) standards and for transmitting the output signal of the first semiconductor element  11  (for example, a Phase signal of multiple phases). 
     The INCK terminal is a terminal for receiving an internal clock signal output from the second semiconductor element  12 . The first semiconductor element  11  operates in synchronization with the internal clock signal. Therefore, the first semiconductor element  11  can operate in synchronization with the second semiconductor element  12 . 
     The XCLR terminal is a terminal for receiving a clear signal output from the second semiconductor element  12 . The clear signal is a signal for initializing the first semiconductor element  11 . 
     The LED_EN terminal is a terminal for outputting an enable signal for putting the light-emitting section  15  into an enabled state. The SPI_Master terminal is a terminal for transmitting a serial signal from the first semiconductor element  11  as the master to the light-emitting section  15  as the slave via a Serial Peripheral Interface (SPI) bus. 
     The second semiconductor element  12  has an XVS terminal, an MIPI_Rx terminal, an INCK terminal, an XCLR terminal and the like as terminals for performing transmission and reception of various signals to/from the first semiconductor element  11 . 
     The XVS terminal is a terminal for receiving a synchronization signal for synchronization with another semiconductor element, as described above. 
     The MIPI_Rx terminal is a terminal compliant with the MIPI standards and for receiving a Phase signal of multiple phases or the like, for example. The INCK terminal is a terminal for transmitting an internal clock signal to the first semiconductor element  11 . The XCLR terminal is a terminal for transmitting a clear signal to the first semiconductor element  11 . 
     Furthermore, the second semiconductor element  12  has an I2C Slave terminal, an INCK terminal, an XCLR terminal, an MIPI_Tx terminal, an SPI_Rx terminal, and a GPI/O terminal as terminals for performing transmission and reception of various signals to/from the third semiconductor element  13 . 
     The I2C Slave terminal is a terminal for receiving two signals for I2C communication from the third semiconductor element  13 . The INCK terminal is a terminal for receiving an internal clock signal from the third semiconductor element  13 . The XCLR terminal is a terminal for receiving a clear signal from the third semiconductor element  13 . The MIPI_Tx terminal is a terminal for transmitting distance information to the third semiconductor element  13  in the MIPI standards. The SPI_Rx terminal is a terminal for receiving a serial signal from the third semiconductor element  13  via an SPI bus. The GPI/O terminal is a terminal for transmitting various signals to the third semiconductor element  13  through a general I/O interface. 
     The third semiconductor element  13  has an I2C_Master terminal, an INCK terminal, an XCLR terminal, an MIPI_Rx terminal, an SPI_Tx terminal, and a GPI/O terminal. 
     The I2c_Master terminal is a terminal for transmitting two signals for I2C communication from the third semiconductor element  13  to the first semiconductor element  11  and the second semiconductor element  12 . 
     The INCK terminal is a terminal for transmitting an internal clock signal to the second semiconductor element  12 . The XCLR terminal is a terminal for transmitting a clear signal to the second semiconductor element  12 . The MIPI_Rx terminal is a terminal for receiving the distance information from the second semiconductor element  12  or the like in the MIPI standards. The SPI_Tx terminal is a terminal for transmitting a serial signal to the second semiconductor element  12  via an SPI bus. The GPI/O terminal is a terminal for receiving various signals from the second semiconductor element  12  through a general I/O interface. 
     The light-emitting section  15  has an SPI_Slave terminal, an LED_EN terminal, and an LDD_XCLR terminal. The SPI_Slave terminal is a terminal for receiving a serial signal from the first semiconductor element  11  as the master via an SPI bus. The LED_EN terminal is a terminal for receiving an enable signal from the first semiconductor element  11 . When the enable signal is in a predetermined logic state, the light-emitting section  15  can emit light. The LDD_XCLR terminal is a terminal for receiving a clear signal from the second semiconductor element  12 . 
     The distance measurement device  10 ,  10   a  according to the present embodiment may include a fourth semiconductor element  14 , in addition to the first to third semiconductor elements  11  to  13 , as shown in  FIGS.  1 A and  1 B . The fourth semiconductor element  14  includes a second light-reception section  14   a  that receives light and performs photoelectric conversion to generate an electric signal. 
     The fourth semiconductor element  14  may be implemented on the first substrate  21  or the second substrate  22 , or may be implemented on a third substrate  23  separate from the first substrate  21  and the second substrate  22 . The electric signal output from the second light-reception section  14   a  in the fourth semiconductor element  14  is input to the third semiconductor element  13  without passing through the second semiconductor element  12 . Therefore, the electric signal output from the second light-reception section  14   a  is subjected to various signal processing at the third semiconductor element  13 . Alternatively, the electric signal output from the second light-reception section  14   a  in the fourth semiconductor element  14  may be input to the second semiconductor element  12  and subjected to signal processing at the second semiconductor element  12 . 
     The electric signal output from the first light-reception section  11   a  in the first semiconductor element  11  and the electric signal output from the second light-reception section  14   a  in the fourth semiconductor element  14  may be synchronized or asynchronous. To synchronize both electric signals, it is possible to transmit a synchronization signal from the fourth semiconductor element  14  to the first semiconductor element  11  and the second semiconductor element  12  for synchronization, for example. In this case, the synchronization signal is output from the XVS terminal of the fourth semiconductor element  14  and input to the XVS terminals of the first semiconductor element  11  and the second semiconductor element  12 . Note that, inversely, a synchronization signal may be transmitted from the first semiconductor element  11  to the second semiconductor element  12  and the fourth semiconductor element  14 . 
     The wavelength band of light received by the first light-reception section  11   a  in the first semiconductor element  11  may be different from the wavelength band of light received by the second light-reception section  14   a  in the fourth semiconductor element  14 . For example, the reception light band of the first light-reception section  11   a  in the first semiconductor element  11  may be 800 to 2000 nm, which is a wavelength band of infrared light, while the reception light band of the second light-reception section  14   a  in the fourth semiconductor element  14  may be 360 to 800 nm, which is a wavelength band of visible light. 
     Thus, the second light-reception section  14   a  in the fourth semiconductor element  14  may be an image sensor generally used in a camera or the like. 
     By synchronizing the electric signal output from the first light-reception section  11   a  and the electric signal output from the second light-reception section  14   a , depth information can be added to at least some pixels in the captured image of visible light, and a three-dimensional image can be generated, for example. 
     The fourth semiconductor element  14  has an I2C terminal and an XVS terminal. The I2C terminal is a terminal for receiving two signals for I2C communication as described above from the third semiconductor element  13 . The XVS terminal is a terminal for transmitting a synchronization signal. 
     Although the first light-reception section  11   a  in the first semiconductor element  11  and the second light-reception section  14   a  in the fourth semiconductor element  14  normally performs a light-reception operation in an asynchronous manner, the second light-reception section  14   a  in the fourth semiconductor element  14  transmits a synchronization signal via the XVS terminal in a case where there is a command for synchronization by I2C communication from the third semiconductor element  13 . This synchronization signal is input to the XVS terminal of the first semiconductor element  11 , and the first light-reception section  11   a  performs the light-reception operation in synchronization with the second light-reception section  14   a  and outputs a Phase signal. Therefore, the Phase signal is also synchronized with the synchronization signal. The Phase signal is input to the second semiconductor element  12  in compliance with the MIPI standards, and the synchronization signal is also input to the XVS terminal of the second semiconductor element  12 . Therefore, the second semiconductor element  12  also performs signal processing in synchronization with the light-reception operation of the second light-reception element in the fourth semiconductor element  14  and generates distance information. The generated distance information is also synchronized with the light-reception operation of the second light-reception section  14   a  in the fourth semiconductor element  14 . 
     The second light-reception section  14   a  in the fourth semiconductor element  14  updates image data at 60 frames per second, for example. Due to the synchronization by the synchronization signal described above, the second semiconductor element  12  can generate distance information in accordance with the timing of the image data output by the second light-reception section  14   a . In order for the third semiconductor element  13  to generate a three-dimensional image, for example, it is necessary to synchronize the image data output by the second light-reception section  14   a  in the fourth semiconductor element  14  and the distance information output by the second semiconductor element  12 , and in such a case, the third semiconductor element  13  instructs the fourth semiconductor element  14  to perform synchronization by I2C communication. 
       FIG.  2    is a block diagram showing an example of an internal configuration of the second semiconductor element  12  in  FIGS.  1 A and  1 B . As shown in  FIG.  2   , the second semiconductor element  12  performs signal processing including calculation of distance information at the signal processing circuit  12   a , which is hardware. Although the calculation of distance information is conventionally performed by software processing of a DSP, for example, the hardware implementation of the software processing that has been performed by the DSP allows the calculation of the distance information to be performed with high speed and low power consumption. The signal processing circuit  12   a  can be formed by a digital circuit using a logical operation gate, F/F and the like, and thus it is possible to reduce the power consumption and to easily perform the automation and optimization of design by using a logic synthesis tool or the like. 
     The second semiconductor element  12  shown in  FIG.  2    includes a processing control circuit  12   b  and a memory  12   c , in addition to the signal processing circuit  12   a.    
     The processing control circuit  12   b  includes a CPU  12   d , ROM  12   e , RAM  12   f  and the like. A plurality of CPUs  12   d  may be used to perform parallel processing. The internal configuration of the processing control circuit  12   b  is arbitrary, and various variations are possible. 
     The signal processing circuit  12   a  includes MIPI_Rx  12   g , MIPI_Rx_IF  12   h , a signal processing section  12   i , MIPI_Tx IF  12   j , MIPI_Tx  12   k , and a bypass path (bypass circuit)  12   m.    
     The MIPI_Rx  12   g  receives a signal output from the first semiconductor element  11 . More specifically, the MIPI_Rx  12   g  receives a Phase signal of the indirect ToF method or the like. 
     The MIPI_Rx_IF  12   h  switches between transmitting the signal output from the first semiconductor element  11  the signal processing section  12   i  and transmitting it to the bypass path  12   m.    
     The signal processing section  12   i  performs noise processing, calibration processing, pre-processing, post-processing, interpolation processing, and the like. The signal processing circuit  12   a  may not only perform the processing of calculating the distance information from the Phase signal but also perform other general signal processing, for example, shading processing or the like. 
     The bypass path  12   m  is a signal path for allowing the signal output from the first semiconductor element  11  to be output from the second semiconductor element  12  without performing signal processing in the signal processing circuit  12   a . The bypass path  12   m  is provided for causing the third semiconductor element  13  in a later stage to perform signal processing in a case where it is necessary to perform signal processing with excessive processing load for the signal processing circuit  12   a , signal processing that results in insufficient performance with the signal processing circuit  12   a , or the like, for example. A resistor, an inductor, a capacitor or the like may be connected on the bypass circuit  12   m  as necessary. 
     The MIPI_Tx 12   k _IF  12   j  selects one of the output signal of the signal processing section  12   i  and the output signal of the bypass path  12   m . The selected signal is output from the second semiconductor element  12  via the MIPI_Tx  12   k.    
       FIG.  3    is a block diagram showing a basic configuration of the distance measurement device  10 ,  10   a  according to the present embodiment. As shown in  FIG.  3   , the distance measurement device  10 ,  10   a  according to the present embodiment includes, in the minimal configuration, the first semiconductor element  11  including the first light-reception section  11   a , the second semiconductor element  12  including the signal processing circuit  12   a , and the third semiconductor element  13 . The third semiconductor element  13  is assumed to have higher signal processing capability than the second semiconductor element  12 , and a high-performance AP or the CPU  12   d  is implemented, for example. 
     The signal processing circuit  12   a  performs signal processing including the calculation of the distance information, for example. The signal processing circuit  12   a  in the second semiconductor element  12  may be provided with the bypass path  12   m  as described above. 
     As an optional function, the light-emitting section  15  may be implemented in or connected to the first semiconductor element  11 . Similarly, the distance measurement device  10 ,  10   a  according to the present embodiment may include the fourth semiconductor element  14  including the second light-reception section  14   a  as an optional function. In this case, the first light-reception section  11   a  and the second light-reception section  14   a  may perform the light-reception operation in synchronization with each other, or may perform the light-reception operation in an asynchronous manner. 
     Each semiconductor element in the distance measurement device  10 ,  10   a  performs master-slave communication by I2C communication. The third semiconductor device is a master, and the other semiconductor elements are slaves. The third semiconductor element  13  as a master transmits control signals to the other semiconductor elements. The first, second and fourth semiconductor elements  11 ,  12 ,  14  perform transmission and reception of various signals under control of the third semiconductor element  13 . 
     Furthermore, the electric signals obtained by the light reception and photoelectric conversion by the first light-reception section  11   a  and the second light-reception section  14   a  are transmitted in compliance with the MIPI standards. 
     The distance measurement device  10  according to the present embodiment can be formed by a laminated chip. In the distance measurement device  10  the light-emitting section is usually provided separately from the distance measurement device  10  instead of being provided in the distance measurement device  10 , as shown in  FIG.  1 A . In this case, as shown in  FIG.  4 A , it is possible to form it by two semiconductor devices (hereinafter, a first semiconductor device  8  and a second semiconductor device  9 ) separately implemented on the substrate  7 . The first semiconductor device  8  is a laminated chip including the distance measurement device  10  shown in  FIG.  1 A . The second semiconductor device  9  is a chip including a light-emitting section. 
       FIG.  4 B  is a diagram showing a first example of the laminated chip forming the first semiconductor device  8  in  FIG.  4 A , and has a bilayer structure of a first chip (first substrate)  31  and a second chip (second substrate)  32 . The first semiconductor element  11  including the first light-reception section  11   a  is implemented on the first chip  31 . The light-emitting section  15  may be implemented on the first chip  31 . 
     The second semiconductor element  12  is implemented on the second chip  32 . The memory  12   c  used by the second semiconductor element  12  may be implemented on the second chip  32 . Although it is possible that the third semiconductor element  13  is implemented on a substrate separate from the first chip  31  and the second chip  32 , the third semiconductor element  13  may also be implemented on the second chip  32 . Alternatively, the third semiconductor element  13  may be laminated in a different layer than the first chip  31  and the second chip  32 . 
     The first chip  31  and the second chip  32  are electrically connected via a connection such as a via, Cu—Cu bonding, or a bump. That is, the first chip  31  and the second chip  32  are laminated together by a Chip on Chip (CoC) method, a Chip on Wafer (CoW) method, or a Wafer on Wafer (WoW) method. 
       FIG.  4 C  is a diagram showing a second example of the laminated chip forming the first semiconductor device  8  in  FIG.  4 A . In  FIG.  4 C , a trilayer structure is formed by providing the memory  12   c  used by the second semiconductor element  12  in a different, third chip (third substrate)  33 .  FIG.  4 C  shows an example in which the third chip  33  is arranged below the second chip  32 . The second chip  32  and the third chip  33  are connected by a via, Cu—Cu bonding, a bump or the like, as described above. The chip configuration in  FIG.  4 C  is adopted such as in a case where the memory  12   c  has a large capacity and cannot be implemented in the second chip  32 . 
       FIG.  4 D  is a diagram showing a third example of the laminated chip forming the first semiconductor device  8  in  FIG.  4 A . In  FIG.  4 D , the first semiconductor element  11  and the fourth semiconductor element  14  are implemented on the first chip  31 . The second chip  32  is similar to that in  FIG.  4 B . 
       FIG.  4 E  is a diagram showing a fourth example of the laminated chip forming the first semiconductor device  8  in  FIG.  4 A . In  FIG.  4 E , a fourth chip (fourth substrate)  34  on which the fourth semiconductor element  14  including the second light-reception section  14   a  is implemented is provided separately from the first chip  31 . The chip configuration in  FIG.  4 E  is adopted such as in a case where the fourth semiconductor element  14  has a large footprint and it is difficult to provide it on the same chip as the first semiconductor element  11 . Although the fourth chip  34  is laminated on the first chip  31  in  FIG.  4 E , the order of lamination may be inverse. The first chip  31  and the fourth chip  34  are connected by a via, Cu—Cu bonding, a bump or the like, as described above. 
     As a variation of  FIG.  4 E , the third chip  33  on which the memory  12   c  is implemented may be provided as in  FIG.  4 C . In this case, a structure in which four chips are laminated is formed. 
     Thus, in the present embodiment, since the second semiconductor element  12  including the signal processing circuit  12   a , which performs signal processing by hardware such as calculating the distance information from the Phase signal of the indirect ToF method, is provided, it is possible to perform signal processing with higher speed and lower power consumption than performing signal processing by software processing. 
     Furthermore, since the bypass path  12   m  is provided in the second semiconductor element  12 , for signal processing for which the processing performance of the signal processing circuit  12   a  in the second semiconductor element  12  is insufficient, it is possible to bypass the signal processing circuit  12   a  so that the signal processing is performed by the third semiconductor element  13  in a later stage. Therefore, it is possible to reduce the hardware cost of the distance measurement device  10 ,  10   a  without the necessity of improving the processing performance of the second semiconductor element  12  more than necessary. 
     Example Configuration of Electronic Equipment 
       FIGS.  5  and  6    show an example of electronic equipment provided with the distance measurement device  10 ,  10   a  according to the present disclosure.  FIG.  5    shows a configuration of electronic equipment  1  as viewed from the positive side of the z-axis. On the other hand,  FIG.  6    shows a configuration of the electronic equipment  1  as viewed from the negative side of the z-axis. The electronic equipment  1  has a substantially flat plate shape, for example, and includes a display section  1   a  on at least one surface (herein, the surface at the positive side of the z-axis). The display section  1   a  can display images by liquid crystal, micro LED, or organic electroluminescence, for example. However, the display manner of the display section  1   a  is not limited. Furthermore, the display section  1   a  may also include a touch panel and a fingerprint sensor. 
     On a surface of the electronic equipment  1  at the negative side of the z-axis, a first image-capturing section  110 , a second image-capturing section  111 , a first light-emitting section  112 , and a second light-emitting section  113  are implemented. For example, the first image-capturing section  110  is a camera module capable of capturing color images. For example, the camera module includes a lens system and an image-capturing device that performs photoelectric conversion of light collected by the lens system. For example, the first light-emitting section  112  is a light source used as a flash unit of the first image-capturing section  110 . For example, a white LED can be used as the first light-emitting section  112 . However, the type of the light source used as the first light-emitting section  112  is not limited. 
     For example, the second image-capturing section  111  is an image-capturing device capable of performing distance measurement by the indirect ToF method. For example, the image-capturing device according to the present disclosure can be implemented as the second image-capturing section  111 . For example, the second image-capturing section  111  corresponds to the first light-reception section  11   a  in  FIG.  1 B . The second light-emitting section  113  is a light source that can be used for distance measurement by the indirect ToF method. For example, the second light-emitting section  113  corresponds to the light-emitting section  15  in  FIG.  1 B . That is, the distance measurement device  10   a  in  FIG.  1 B  may be implemented in the electronic equipment  1 . The electronic equipment  1  can perform various processing on the basis of the distance image output from the distance measurement device  10   a.    
     A case where the electronic equipment according to the present disclosure is a smartphone or a tablet has been described herein. However, the electronic equipment according to the present disclosure may also be another type of device such as a game machine, in-vehicle equipment, a PC, or a surveillance camera, for example. 
     The distance measurement device  10 ,  10   a  according to the present disclosure may include a signal generator, a plurality of flip-flops connected in cascade, a circuit block, a pixel array, and a signal processing section. The signal generator is configured to generate a clock signal. The circuit block is configured to supply a first signal to respective clock terminals of the plurality of flip-flops according to the clock signal and supply a second signal to an input terminal of a first-stage flip-flop of the plurality of flip-flops. The pixel array includes pixels configured to be driven by pulse signals supplied from different stages of the plurality of flip-flops. The signal processing section is configured to generate a distance image on the basis of charges generated by photoelectric conversion in the pixels of the pixel array. 
     The electronic equipment according to the present disclosure may include a signal generator, a plurality of flip-flops connected in cascade, a circuit block, and a pixel array. The signal generator is configured to generate a clock signal. The circuit block is configured to supply a first signal to respective clock terminals of the plurality of flip-flops according to the clock signal and supply a second signal to an input terminal of a first-stage flip-flop of the plurality of flip-flops. The pixel array includes pixels configured to be driven by pulse signals supplied from different stages of the plurality of flip-flops. 
     Example Application to Mobile Body 
     The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized by a device provided to any type of mobile body such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility vehicle, an airplane, a drone, a ship, or a robot. 
       FIG.  7    is a block diagram showing an example schematic configuration of a vehicle control system as an example of a mobile body control system to which the technology according to the present disclosure can be applied. 
     A vehicle control system  12000  includes a plurality of electronic control units connected via a communication network  12001 . In the example shown in  FIG.  7   , the vehicle control system  12000  includes a drive system control unit  12010 , a body system control unit  12020 , a vehicle external information detection unit  12030 , a vehicle internal information detection unit  12040 , and an integrated control unit  12050 . Furthermore, as functional components of the integrated control unit  12050 , a microcomputer  12051 , a sound/image output section  12052 , and an in-vehicle network interface (I/F)  12053  are shown in the figure. 
     The drive system control unit  12010  controls the operation of devices related to the drive system of the vehicle according to various programs. For example, the drive system control unit  12010  functions as a control device for a driving force generation device for generating driving force of the vehicle such as an internal combustion engine or a driving motor, a driving force transmission mechanism for transmitting the driving force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, a braking device for generating braking force of the vehicle, and the like. 
     The body system control unit  12020  controls the operation of various devices provided to the vehicle body according to various programs. For example, the body system control unit  12020  functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as a headlamp, a backup lamp, a stop lamp, a blinker, or a fog lamp. In this case, radio waves emitted from mobile device substituting a key or signals from various switches can be input to the body system control unit  12020 . The body system control unit  12020  receives the input of the radio waves or signals and controls the door locking device, power window device, lamps, and the like of the vehicle. 
     The vehicle external information detection unit  12030  detects information external to the vehicle provided with the vehicle control system  12000 . For example, an image-capturing section  12031  is connected to the vehicle external information detection unit  12030 . The vehicle external information detection unit  12030  causes the image-capturing section  12031  to capture an image of the space external to the vehicle and receives the captured image. The vehicle external information detection unit  12030  may perform object detection processing or distance detection processing on a person, vehicle, obstacle, sign, characters on the road surface, or the like on the basis of the received image. 
     The image-capturing section  12031  is an optical sensor that receives light and outputs an electric signal corresponding to the amount of light received. The image-capturing section  12031  can output the electric signal as an image or as distance measurement information. Furthermore, the light received by the image-capturing section  12031  may be visible light or may be non-visible light such as infrared light. 
     The vehicle internal information detection unit  12040  detects information about the interior of the vehicle. For example, a driver condition detection section  12041  for detecting the conditions of the driver is connected to the vehicle internal information detection unit  12040 . The driver condition detection section  12041  includes a camera for capturing an image of the driver, for example, and the vehicle internal information detection unit  12040  may calculate the degree of fatigue or the degree of concentration of the driver on the basis of detection information input from the driver condition detection section  12041 , or may determine whether the driver is dozing. 
     The microcomputer  12051  can compute a control target value for the driving force generation device, the steering mechanism, or the braking device on the basis of the information about the interior or exterior of the vehicle acquired by the vehicle external information detection unit  12030  or the vehicle internal information detection unit  12040  and output a control command to the drive system control unit  12010 . For example, the microcomputer  12051  can perform cooperative control for the purpose of realizing the function of the Advanced Driver Assistance System (ADAS) including collision avoidance or shock mitigation for the vehicle, follow-up driving based on the following distance, vehicle speed maintaining driving, collision alert for the vehicle, lane deviation alert for the vehicle, or the like. 
     Furthermore, the microcomputer  12051  can perform cooperative control for the purpose of automated driving or the like for autonomously traveling without relying on operations of the driver by controlling the driving force generation device, the steering mechanism, the braking device, or the like on the basis of information about the surroundings of the vehicle acquired by the vehicle external information detection unit  12030  or the vehicle internal information detection unit  12040 . 
     Furthermore, the microcomputer  12051  can output a control command to the body system control unit  12020  on the basis of the information about the exterior of the vehicle acquired by the vehicle external information detection unit  12030 . For example, the microcomputer  12051  can perform cooperative control for the purpose of glare reduction such as controlling the headlamp according to the position of a leading vehicle or an oncoming vehicle detected by the vehicle external information detection unit  12030  to switch high beam to low beam. 
     The sound/image output section  12052  transmits an output signal of at least one of a sound and an image to an output device capable of visually or auditorily notifying an occupant of the vehicle or the external of the vehicle of information. In the example of  FIG.  7   , an audio speaker  12061 , a display section  12062 , and an instrument panel  12063  are illustrated as output devices. The display section  12062  may include at least one of an onboard display and a head-up display, for example. 
       FIG.  8    is a diagram showing an example of installation positions of the image-capturing section  12031 . 
     In  FIG.  8   , a vehicle  12100  includes image-capturing sections  12101 ,  12102 ,  12103 ,  12104 ,  12105  as the image-capturing section  12031 . 
     For example, the image-capturing sections  12101 ,  12102 ,  12103 ,  12104 ,  12105  are provided at positions such as a front nose, a door mirror, a rear bumper, a back door, and the upper portion of a windshield inside the cabin, of the vehicle  12100 . The image-capturing section  12101  provided at the front nose and the image-capturing section  12105  provided at the upper portion of the windshield inside the cabin mainly acquire images of the space in front of the vehicle  12100 . The image-capturing sections  12102 ,  12103  provided at the door mirrors mainly acquire images of the space at the sides of the vehicle  12100 . The image-capturing section  12104  provided at the rear bumper or the back door mainly acquires an image of the space in the rear of the vehicle  12100 . The images of the front space acquired by the image-capturing sections  12101  and  12105  are mainly used for detection of a leading vehicle or a pedestrian, an obstacle, a traffic signal, a traffic sign, a lane, or the like. 
     Note that  FIG.  8    shows an example of image-capturing areas of the image-capturing sections  12101  to  12104 . An image-capturing area  12111  indicates the image-capturing area of the image-capturing section  12101  provided at the front nose, an image-capturing areas  12112 ,  12113  indicate the image-capturing areas of the image-capturing sections  12102 ,  12103  provided at the door mirrors, respectively, and an image-capturing area  12114  indicates the image-capturing area of the image-capturing section  12104  provided at the rear bumper or the back door. For example, pieces of image data captured by the image-capturing sections  12101  to  12104  are overlaid to obtain a look-down image of the vehicle  12100  as viewed from above. 
     At least one of the image-capturing sections  12101  to  12104  may have a function of acquiring distance information. For example, at least one of the image-capturing sections  12101  to  12104  may be a stereo camera including a plurality of image-capturing devices, or may be an image-capturing device having pixels for phase difference detection. 
     For example, the microcomputer  12051  can extract, as a leading vehicle, a three-dimensional object that in particular is closest on the road on which the vehicle  12100  travels and is traveling in substantially the same direction as the vehicle  12100  at a predetermined speed (for example, 0 km/h or more) by calculating the distance to each three-dimensional object in the image-capturing areas  12111  to  12114  and a temporal change of the distance (a relative speed to the vehicle  12100 ) on the basis of the distance information obtained from the image-capturing sections  12101  to  12104 . Moreover, the microcomputer  12051  can set a following distance to be kept in advance in front of a leading vehicle and perform automatic brake control (including following stop control), automatic acceleration control (including following start control), and the like. Thus, it is possible to perform cooperative control for the purpose of automated driving or the like for autonomously traveling without relying on operations of the driver. 
     For example, the microcomputer  12051  can classify and extract three-dimensional object data relating to three-dimensional objects into a two-wheeled vehicle, a standard vehicle, a large vehicle, a pedestrian, and other three-dimensional objects such as a telegraph pole on the basis of the distance information obtained from the image-capturing sections  12101  to  12104 , and use them for automatic obstacle avoidance. For example, the microcomputer  12051  divides obstacles around the vehicle  12100  into obstacles that can be visually recognized by the driver of the vehicle  12100  and obstacles that are difficult to visually recognize. The microcomputer  12051  can then determine a collision risk indicating the degree of risk of collision with each obstacle and, in a case where the collision risk is greater than or equal to a set value and collision is possible, perform driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker  12061  or the display section  12062  or by performing forced deceleration or avoidance steering via the drive system control unit  12010 . 
     At least one of the image-capturing sections  12101  to  12104  may be an infrared camera that detects infrared light. For example, the microcomputer  12051  can recognize a pedestrian by determining whether or not a pedestrian is present in the captured images of the image-capturing sections  12101  to  12104 . For example, the recognition of a pedestrian is performed by a procedure of extracting feature points in the captured images of the image-capturing section  12101  to  12104  as infrared cameras and a procedure of performing pattern matching processing on a series of feature points indicating the contour of an object and discriminating whether or not it is a pedestrian. In a case where the microcomputer  12051  determines that a pedestrian is present in the captured images of the image-capturing sections  12101  to  12104  and recognizes the pedestrian, the sound/image output section  12052  controls the display section  12062  to display a rectangular contour line for highlight superimposed on the recognized pedestrian. Furthermore, the sound/image output section  12052  may control the display section  12062  to display an icon or the like indicating the pedestrian at a desired position. 
     An example of the vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to the image-capturing section  12031 , for example, among the components described above. Specifically, the image-capturing device according to the present disclosure can be implemented in the image-capturing section  12031 . By applying the technology according to the present disclosure to the image-capturing section  12031 , it is possible to improve the resolution of the distance image while suppressing the generation of electromagnetic noise and to enhance the functionality and safety of the vehicle  12100 . 
     Note that the present technology can assume the following configurations. 
     (1) A distance measurement device including: 
     a first semiconductor element including a first light-reception section that receives light and performs photoelectric conversion to generate an electric signal; 
     a second semiconductor element including a distance calculation section that performs calculation of distance information regarding a distance to an object on the basis of the electric signal; and 
     a third semiconductor element including a signal processing section that performs predetermined information processing on the basis of an output signal of the distance calculation section. 
     (2) The distance measurement device according to (1), 
     in which the second semiconductor element includes a bypass circuit, and 
     the signal processing section performs the information processing on the electric signal output via the bypass circuit. 
     (3) The distance measurement device according to (2), in which the bypass circuit outputs the electric signal output from the first semiconductor element without performing processing at the distance calculation section. 
     (4) The distance measurement device according to any one of (1) to (3), 
     in which the first semiconductor element outputs the electric signal of multiple phases in which a phase difference changes with the distance to the object, and 
     the distance calculation section calculates the distance information on the basis of the electric signal of the multiple phases. 
     (5) The distance measurement device according to any one of (1) to (3), in which the distance calculation section calculates the distance information from a time difference between a timing at which a light-emitting section emits light and a timing at which the first light-reception section receives light. 
     (6) The distance measurement device according to any one of (1) to (5), further including a light-emitting section that emits light in response to control from the first light-reception section. 
     (7) The distance measurement device according to (6), in which the first semiconductor element and the light-emitting section are implemented on a same substrate. 
     (8) The distance measurement device according to any one of (1) to (7), further including: 
     a first substrate on which the first semiconductor element is implemented; and 
     a second substrate on which the second semiconductor element is implemented, 
     in which the first substrate and the second substrate are laminated on each other. 
     (9) The distance measurement device according to (8), in which the first substrate and the second substrate are laminated together by a Chip on Chip (CoC) method, a Chip on Wafer (CoW) method, or a Wafer on Wafer (WoW) method. 
     (10) The distance measurement device according to (8) or (9), further including a memory implemented on the second substrate and used by the distance calculation section for performing the calculation of the distance information. 
     (11) The distance measurement device according to (8) or (9), further including a third substrate on which a memory used by the distance calculation section for performing the calculation of the distance information is implemented, 
     in which the first substrate, the second substrate, and the third substrate are laminated in a predetermined order. 
     (12) The distance measurement device according to (10) or (11), in which the memory includes a volatile memory or a rewritable non-volatile memory. 
     (13) The distance measurement device according to any one of (1) to (12), in which the distance calculation section includes a digital circuit that performs digital signal processing on the electric signal including the calculation of the distance information. 
     (14) The distance measurement device according to any one of (1) to (13), further including a fourth semiconductor element including a second light-reception section that receives light and performs photoelectric conversion to generate an electric signal. 
     (15) The distance measurement device according to (14), in which an electric signal output from the second light-reception section is input to the third semiconductor element without passing through the second semiconductor element. 
     (16) The distance measurement device according to (14) or (15), in which the third semiconductor element controls whether or not to synchronize an electric signal output from the first light-reception section and an electric signal output from the second light-reception section. 
     (17) The distance measurement device according to (16), in which the fourth semiconductor element transmits, to the first semiconductor element and the second semiconductor element, a synchronization signal synchronized with an electric signal output from the second light-reception section. 
     (18) The distance measurement device according to any one of (14) to (17), in which the first light-reception section and the second light-reception section receive light of respective different wavelength bands. 
     The aspects of the present disclosure are not limited to the individual embodiments described above and include various modifications that can be conceived by those skilled in the art, and also the effects of the present disclosure are not limited to those described above. In other words, various additions, modifications, and partial deletions are possible without departing from the conceptual idea and spirit of the present disclosure derived from the definitions of the claims and their equivalents. 
     REFERENCE SIGNS LIST 
     
         
           1  Electronic equipment 
           10  Distance measurement device 
           11  First semiconductor element 
           12  Second semiconductor element 
           13  Third semiconductor element 
           21  First substrate 
           22  Second substrate 
           23  Third substrate 
           25  Power supply IC 
           26  DRAM chip 
           27  FRASH memory chip 
           31  First chip 
           32  Second chip 
           33  Third chip 
           34  Fourth chip 
           110  First image-capturing section 
           111  Second image-capturing section 
           112  First light-emitting section 
           113  Second light-emitting section