Distance measuring device, switch device, and control chip

Abstract

The distance measuring device uses multiple light-emitting elements, each emitting light in a different direction, to enable the measurement of the distance to each part of an object within a predetermined field of view. [Solution] A distance measuring device is provided comprising a light-emitting unit, a light-receiving unit, and a control unit having a memory area, wherein the control unit is configured to communicate a status signal indicating the state of the light-receiving unit with the light-receiving unit, the status signal includes information indicating whether the light-receiving unit is in a state where it can measure light from the object, or information to enable the light-receiving unit to measure, the control unit outputs a channel selection signal and a light emission control signal to the light-emitting unit according to the status signal stored in the memory area, and the light-emitting unit is configured to receive the status signal from the light-receiving unit or the control unit.

Description

Technical Field

[0001] The present invention relates to a distance measuring device, a switch device, and a control chip.

Background Art

[0002] Patent Document 1 discloses a "laser array drive circuit" "applied to a distance detection device". Patent Document 2 discloses a "depth acquisition component" including a "laser driver array" and a "laser array". [Prior Art Documents] [Patent Documents] [Patent Document 1] U.S. Patent No. 7809037 [Patent Document 2] Japanese Patent Application Laid-Open No. 2023-517000

Summary of the Invention

[0003] In a first embodiment of the present invention, a distance measuring device is provided. The distance measuring device may have a light-emitting unit having a plurality of light-emitting elements that irradiate an object with light. Any of the distance measuring devices may have a light-receiving unit that receives light from the object, for example, reflected light when light emitted from the light-emitting unit is reflected off the object. Any of the distance measuring devices may include a control unit configured to communicate with the light-emitting unit and the light-receiving unit and having a memory area. In any of the distance measuring devices, the control unit may be configured to communicate with the light-receiving unit a status signal indicating the state of the light-receiving unit. The status signal in any of the distance measuring devices may include information indicating whether the light-receiving unit is in a state where it can measure light from the object, or information for making the light-receiving unit measurable. The memory area in any of the distance measuring devices may store the status signal. The control unit in any of the distance measuring devices may output a channel selection signal to the light-emitting unit to select which of the plurality of light-emitting elements to emit light, and a light emission control signal to control the timing of light emission of the light-emitting unit, in accordance with the status signal stored in the memory area. The light-emitting unit in any of the above-described distance measuring devices may be configured to receive the status signal from the light-receiving unit or the control unit. That is, the distance measuring device may include a light-emitting unit having a plurality of light-emitting elements that irradiate an object with light. The distance measuring device may include a light-receiving unit that receives light from the object. The distance measuring device may include a control unit that generates a channel selection signal to select a light-emitting element to emit light at the light-emitting timing corresponding to the light-emitting control signal, based on at least one of a status signal indicating the state of the light-receiving unit and a light-emitting control signal that controls the light-emitting timing of the light-emitting unit. In any of the above-described distance measuring devices, the status signal may include information indicating whether the light-receiving unit is in a state where it can measure light from the object, or information to enable the light-receiving unit to measure.

[0004] In any of the above-described distance measuring devices, the light-emitting unit may be driven in response to the input status signal being information indicating that the light-receiving unit is in a state where it can measure light from the object, or information that enables the light-receiving unit to measure.

[0005] In any of the above-described distance measuring devices, the control unit may output the light emission control signal to the light-emitting unit and stop outputting the channel selection signal to the light-emitting unit if the status signal stored in the memory area is information indicating that the light-receiving unit is in a state where it can measure light from the object, or information for enabling the light-receiving unit to measure. Furthermore, in any of the above-described distance measuring devices, the control unit may output the channel selection signal to the light-emitting unit and stop outputting the light emission control signal to the light-emitting unit if the status signal stored in the memory area is different from either information indicating that the light-receiving unit is in a state where it can measure light from the object or information for enabling the light-receiving unit to measure.

[0006] In any of the above-described distance measuring devices, the light receiving unit may generate a status signal indicating whether or not it is in a state where it can measure light from the object, and input it to the control unit. In any of the above-described distance measuring devices, the control unit may generate the channel selection signal based on the status signal.

[0007] In any of the above-described distance measuring devices, the light receiving unit may have a light-receiving element that measures light from the object. In any of the above-described distance measuring devices, the light receiving unit may have a state control circuit that generates a scan start signal to control the light-receiving element. In any of the above-described distance measuring devices, the state control circuit may input the scan start signal as the state signal to the control unit.

[0008] In any of the above-described distance measuring devices, the control unit may generate a status signal that controls the light receiving unit to a state in which it can measure light from the object. The control unit may input a scan start signal to the light receiving unit as the status signal to control the light receiving element. In any of the above-described distance measuring devices, the control unit may generate the channel selection signal based on the scan start signal.

[0009] In any of the above-described distance measuring devices, the control unit may generate a light-emitting pulse signal to be supplied to the light-emitting element selected by the channel selection signal, in synchronization with the channel selection signal.

[0010] In any of the above-described distance measuring devices, the control unit may generate the light emission pulse signal based on correction information for at least one of the light emission delay time, light emission intensity, and light emission pulse width for each channel.

[0011] In any of the above-described distance measuring devices, the light receiving unit may input the status signal to the light emitting unit and the control unit. In any of the above-described distance measuring devices, the light emitting unit may receive the status signal from the light receiving unit and the channel selection signal from the control unit.

[0012] In any of the above-described distance measuring devices, the control unit may input the status signal and the channel selection signal to the light-emitting unit in a synchronized manner.

[0013] In any of the above-described distance measuring devices, the control unit may have a channel control circuit that generates the channel selection signal. In any of the above-described distance measuring devices, the control unit may have a pulse generation circuit that generates the light emission pulse signal.

[0014] In any of the above-described distance measuring devices, the channel control circuit and the pulse generation circuit may be integrated on a single chip.

[0015] In any of the above distance measuring devices, the control unit may have a driver that is commonly provided for the plurality of light-emitting elements and causes any of the plurality of light-emitting elements to emit light based on a light emission pulse signal corresponding to the light emission control signal. In any of the above distance measuring devices, the light-emitting unit may have a plurality of switches provided corresponding to the plurality of light-emitting elements, a plurality of charging capacitors provided corresponding to the plurality of light-emitting elements, and a switch control circuit that controls the plurality of switches. In any of the above distance measuring devices, the switch selected by the channel selection signal from among the plurality of switches may be controlled to be in the ON state. In any of the above distance measuring devices, the charging capacitor corresponding to the switch controlled to be in the ON state from among the plurality of charging capacitors may be charged. In any of the above distance measuring devices, the light-emitting element corresponding to the charged charging capacitor from among the plurality of light-emitting elements may emit light in response to the light emission pulse signal. In any of the above distance measuring devices, the switch control circuit may detect the end timing of the emission of light from any of the light-emitting elements and, based on the end timing, control the switch corresponding to the light-emitting element to be emitted next to be in the ON state to pre-charge the corresponding charging capacitor.

[0016] In any of the above-described distance measuring devices, the light receiving unit may repeatedly switch between a state in which it can measure light from the object and a state in which it cannot measure light. In any of the above-described distance measuring devices, the switch control circuit may, after detecting the termination timing and before the light receiving unit next enters the state in which it can measure light, control the switch corresponding to the light-emitting element that should next emit light to be turned ON.

[0017] In any of the above-described distance measuring devices, the switch control circuit may detect the termination timing based on the status signal.

[0018] In any of the above-described distance measuring devices, the switch control circuit may detect the termination timing based on the light emission control signal.

[0019] In a second aspect of the present invention, a switch device is provided for use in a light-emitting section of a distance measuring device, which has a plurality of light-emitting elements and a plurality of charging capacitors that irradiate an object with light. The switch device may include a plurality of switches corresponding to the plurality of light-emitting elements. Any of the switch devices may include a switch control circuit for controlling the plurality of switches. In any of the switch devices, the switch corresponding to the light-emitting element that should emit light in response to an input channel selection signal may be controlled to be in the ON state. In any of the distance measuring devices, the charging capacitor corresponding to the switch controlled to be in the ON state may be charged. In any of the distance measuring devices, the light-emitting element corresponding to the charged charging capacitor may emit light in response to an input light emission pulse signal. In any of the distance measuring devices, the switch control circuit may detect the end timing of the emission of light from any of the light-emitting elements and, based on the end timing, control the switch corresponding to the next light-emitting element to emit light to be in the ON state to pre-charge the corresponding charging capacitor.

[0020] A third embodiment of the present invention provides a control chip for use in a distance measuring device comprising a light-emitting unit having a plurality of light-emitting elements that irradiate an object with light, and a light-receiving unit that receives light from the object. The control chip may include a channel control circuit that generates a channel selection signal for selecting a light-emitting element to emit light. Any of the control chips may include a pulse generation circuit that generates a light-emitting pulse signal to be supplied to the light-emitting element selected by the channel selection signal, in synchronization with the channel selection signal, based on correction information for at least one of the light emission delay time, light emission intensity, and light emission pulse width of the light-emitting element for each channel.

[0021] It should be noted that the above summary of the invention does not enumerate all of its features. Furthermore, subcombinations of these features may also constitute an invention. [Brief explanation of the drawing]

[0022] [Figure 1] It is a diagram showing a configuration example of a distance measurement device 100 according to one embodiment of the present invention. [Figure 2] It is a timing chart showing waveform examples of each signal. [Figure 3] It is a diagram showing an example of a distance measurement device 200 according to a comparative example. [Figure 4] It is a timing chart showing waveform examples of each signal in the distance measurement device 200. [Figure 5] It is a diagram explaining factors of variations in delay times of a light emission pulse signal LP and a channel selection signal CH in the distance measurement device 200 according to the comparative example and the distance measurement device 100 according to the example. [Figure 6] It is a diagram showing a configuration example of a light receiving unit 60 and a pulse generation circuit 30. [Figure 7] It is a timing chart explaining an operation example of the light receiving unit 60 and the pulse generation circuit 30 shown in FIG. 6. [Figure 8] It is a diagram showing another configuration example of the distance measurement device 100. [Figure 9] It is a diagram showing another configuration example of the distance measurement device 100. [Figure 10] It is a timing chart showing waveform examples of each signal in the example shown in FIG. 9 [Figure 11] It is a diagram explaining factors of variations in delay times of a light emission pulse signal LP and a channel selection signal CH in the distance measurement device 100 according to the example of FIG. 9. [Figure 12] It is a diagram showing a configuration example of the light receiving unit 60 and the pulse generation circuit 30 in the example of FIG. 9. [Figure 13] It is a timing chart showing waveform examples of each signal in the example shown in FIG. 12. [Figure 14] It is a diagram showing another configuration example of the distance measurement device 100. [Figure 15] It is a diagram showing another configuration example of the control unit 10. [Figure 16] It is a diagram showing a configuration example of a switch device 80. [Figure 17]This is a timing chart illustrating other operating examples of the switch device 80. [Figure 18] This figure shows another example configuration of the pulse generation circuit 30. [Figure 19] This diagram shows an example configuration in which a power supply circuit 110 that supplies power voltage to the light-emitting unit 70 and a power supply control unit 120 are provided. [Figure 20] This figure shows an example of the configuration of the power supply control unit 120. [Figure 21] This figure shows another example configuration of the switch device 80. [Modes for carrying out the invention]

[0023] The present invention will be described below through embodiments, but these embodiments are not intended to limit the scope of the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0024] Figure 1 shows an example of the configuration of a distance measuring device 100 according to one embodiment of the present invention. The distance measuring device 100 measures the distance L (m) to an object based on the time T (s) from when light is shone on the object until the reflected light from the object is received. For example, if the speed of light is c (m / s), the distance L is given by the following formula. L = cT / 2

[0025] The distance measuring device 100 in this example can measure the distance to each part of an object within a predetermined field of view by using multiple light-emitting elements that each emit light in different directions. By sequentially emitting light from each light-emitting element and measuring the reflected light, the control system and measurement system for the multiple light-emitting elements can be standardized, allowing the distance measuring device 100 to be miniaturized.

[0026] The distance measuring device 100 in this example comprises a light-emitting unit 70, a light-receiving unit 60, a control unit 10, and an MCU unit 20. The light-emitting unit 70 has a plurality of light-emitting elements 72 that irradiate an object with light. In the example in Figure 1, three light-emitting elements 72-0, 72-1, and 72-2 are shown, but the light-emitting unit 70 may have more light-emitting elements 72, or it may have two light-emitting elements 72. Each light-emitting element 72 is, for example, a laser diode, but is not limited to this. Each light-emitting element 72 may irradiate light in different directions from each other. The plurality of light-emitting elements 72 may be arranged in a line in one direction, or they may be arranged in a line in multiple directions. For example, the plurality of light-emitting elements 72 may be arranged at predetermined intervals in a predetermined plane or curved surface.

[0027] The light-receiving unit 60 receives light from the object. The light-receiving unit 60 receives reflected light that has been reflected by the object from the light-emitting unit 70. The light-receiving unit 60 may be provided in common for multiple light-emitting elements 72. The light-receiving unit 60 measures the time T from when the light-emitting element 72 emits light until it receives reflected light from the object, for each light-emitting element 72. This allows the distance to the object in the direction from which each light-emitting element 72 emits light to be measured.

[0028] The light-emitting unit 70 in this example has a switch device 80 including a plurality of switches 82, and a plurality of charging capacitors 74. The plurality of switches 82 and the plurality of charging capacitors 74 are provided corresponding to a plurality of light-emitting elements 72. That is, the switches 82 are provided in a one-to-one correspondence with the light-emitting elements 72, and the charging capacitors 74 are also provided in a one-to-one correspondence with the light-emitting elements 72. In this example, a configuration including one switch 82, one charging capacitor 74, and one light-emitting element 72 may be referred to as a channel. In each channel, the switch 82 and the light-emitting element 72 are provided in series between the power supply and a reference potential (e.g., ground potential). In the example in Figure 1, the switch 82 is positioned at a higher potential than the light-emitting element 72. The charging capacitor 74 is provided between the anode terminal of the light-emitting element 72 and the reference potential.

[0029] Of the multiple switches 82, the switch 82 corresponding to the channel selection signal CH, described later, is controlled to be in the ON state. When any of the switches 82 are controlled to be in the ON state, the corresponding light-emitting element 72 is connected to the power supply and becomes capable of emitting light. In this specification, the state in which the corresponding switch 82 is in the ON state may be referred to as "capable of emitting light." Also, when any of the switches 82 are controlled to be in the ON state, the corresponding charging capacitor 74 is charged by the power supply. This power supply may be a power supply provided in the distance measuring device 100, or it may be an external power supply.

[0030] In this example, the cathode terminal of each light-emitting element 72 is connected to a common driver 50. The driver 50 in this example is a Si MOS transistor. The driver 50 may also be a transistor made of a compound semiconductor such as GaN or SiC. When the driver 50 is turned on, the cathode terminal of each light-emitting element 72 is connected to a reference potential. When the driver 50 is turned on, the light-emitting element 72 whose corresponding switch 82 is turned on emits light. If the charging capacitor 74 is pre-charged before the driver 50 is turned on, the time from when the driver 50 is controlled to be turned on until the light-emitting element 72 actually emits light can be shortened.

[0031] In the configuration shown in Figure 1, it is preferable to precisely synchronize the timing of controlling the switch 82 to the ON state and the timing of controlling the driver 50 to the ON state. For example, if the timing of controlling the switch 82 to the ON state is delayed, even if the driver 50 is controlled to the ON state, the charge stored in the charging capacitor 74 may not be sufficient, and the light-emitting element 72 may not emit light or the light-emitting intensity may be insufficient. Also, if the timing of turning on the driver 50 is delayed, the period during which the light-emitting element 72 emits light may be shortened. In this specification, synchronization refers to setting the two signals to a predetermined phase difference. That is, in addition to the case where the edge timings of the two signals match, setting the edge timings of the two signals to a predetermined time difference is also referred to as synchronization.

[0032] In this example, the control unit 10 precisely synchronizes the timing of controlling the switch 82 to the ON state with the timing of controlling the driver 50 to the ON state. This allows the light-emitting element 72 to emit light accurately even if the channel switching period in the light-emitting unit 70 is shortened, enabling high-speed measurement of the distance to the target object. For this reason, the distance measuring device 100 in this example is also suitable for real-time distance measurement.

[0033] The control unit 10 controls the light-emitting unit 70. The control unit 10 controls the timing of when the light-emitting unit 70 emits light. For example, the control unit 10 controls the timing so that each light-emitting element 72 emits light during the period when the light-receiving unit 60 can receive reflected light.

[0034] The control unit 10 in this example includes a pulse generation circuit 30, a channel control circuit 40, and a driver 50. The MCU unit 20 may be, for example, a microcomputer. The MCU unit 20 may be provided on a circuit chip independent of the control unit 10. In this example, the MCU unit 20 functions as an operation control circuit 21 and outputs an operation instruction signal ST that defines the distance measurement timing for each channel of the light-emitting unit 70. The MCU unit 20 is configured to control the light-receiving unit 60 and controls the timing at which the light-receiving unit 60 becomes capable of receiving reflected light. In this example, the MCU unit 20 outputs an operation instruction signal ST to the light-receiving unit 60.

[0035] The light-receiving unit 60 is controlled to a state where it can receive reflected light in accordance with the operation instruction signal ST. For example, in accordance with the operation instruction signal ST, the light-receiving unit 60 resets the amount of charge accumulated by the photo-receiving element, such as a photodiode, through photoelectric conversion during the previous scan period, and prepares it for photoelectric conversion during the next scan period.

[0036] In this example, the light-receiving unit 60 generates and outputs a scan start signal SS indicating whether or not the light-receiving unit 60 is in a state where it can receive reflected light. In this example, the light-receiving unit 60 inputs the scan start signal SS to both the light-emitting unit 70 and the control unit 10.

[0037] For example, the scan start signal SS is a binary signal that indicates H logic when the light receiving unit 60 is in a state where it can receive reflected light, and L logic when it is not in a state where it can receive light. In this example, the scan start signal SS is a signal that alternates between periods of H logic and periods of L logic. One repetition of H logic and L logic in the scan start signal SS corresponds to distance measurement for one channel. For example, during the H logic period of the scan start signal SS, the light receiving unit 60 performs photoelectric conversion for distance measurement of that channel, resets the charge during the next L logic period, and performs photoelectric conversion for distance measurement of the next channel during the next H logic period. By repeating this operation, the light receiving unit 60 measures the distance for each channel.

[0038] In this example, the channel control circuit 40 generates a channel selection signal CH in synchronization with the scan start signal SS. The channel selection signal CH is a signal that specifies the next light-emitting element 72 to be illuminated. The channel control circuit 40 has information pre-set to indicate the order in which the light-emitting elements 72 are selected. For example, if the light-emitting unit 70 has channels 0 through n, the channel control circuit 40 may select each channel from 0 to n in ascending order of number. After the nth channel, the 0th channel may be selected. However, the selection order of the channels is not limited to this.

[0039] The light-emitting unit 70 is configured to receive status signals from the light-receiving unit 60 or the control unit 10. In this example, the light-emitting unit 70 receives a scan start signal SS from the light-receiving unit 60 and a channel selection signal CH from the channel control circuit 40. In this example, the switch device 80 controls each switch 82 based on the scan start signal SS and the channel selection signal CH. For example, the switch device 80 controls the switch 82 of the channel specified by the channel selection signal CH to the ON state during the period when the scan start signal SS indicates H logic. As a result, the charging capacitor 74 of that channel is charged, and the voltage of the charging capacitor 74 is applied to the light-emitting element 72 of that channel.

[0040] In this example, the light-receiving unit 60 further outputs a light emission instruction signal LC that causes the light-emitting element 72 to emit light. The light emission instruction signal LC is a signal synchronized with the scan start signal SS. For example, the light emission instruction signal LC is a binary signal that transitions to H logic at the timing when the light-emitting element 72 should emit light. The light-receiving unit 60 may transition the logic value of the light emission instruction signal LC to H logic when it becomes capable of receiving reflected light. This allows the light-emitting element 72 to emit light during the period when the light-receiving unit 60 is capable of receiving light.

[0041] The pulse generation circuit 30 generates a pulse signal LP containing a pulse of a predetermined pulse width in response to the light emission instruction signal LC. In this example, the pulse generation circuit 30 generates a pulse of a predetermined pulse width at the timing when the light emission instruction signal LC transitions to high logic. This pulse width is preset by the manufacturer or user of the distance measuring device 100. This pulse width corresponds to one light emission period of the light-emitting element 72.

[0042] The driver 50 is provided in common for multiple light-emitting elements 72. The driver 50 causes one of the light-emitting elements 72 to light up in response to a pulse signal LP corresponding to a light-emitting control signal (light-emitting instruction signal LC in this example). In this example, the driver 50 is a MOSFET to which the pulse signal LP is input as the gate terminal. For example, the driver 50 turns on during the period when the pulse signal LP indicates high logic, connecting the cathode terminals of the multiple light-emitting elements 72 to a reference potential. As a result, the light-emitting element 72 whose corresponding switch 82 is turned on lights up.

[0043] The control unit 10 in this example is configured to communicate with the light-emitting unit 70 and the light-receiving unit 60, and has a storage area 39, which will be described later. "Communication possible" means that at least one of the transmission and reception of information is possible. For example, the control unit 10 is configured to communicate with the light-receiving unit 60 a status signal indicating the state of the light-receiving unit 60. The control unit 10 may receive the status signal from the light-receiving unit 60, or it may transmit the status signal to the light-receiving unit 60. In either case, the control unit 10 is in a state where it can recognize the state of the light-receiving unit 60. The control unit 10 may recognize whether the light-receiving unit 60 is in a state where it can receive light, or is controlled to be in a state where it can receive light, or is in neither state. In this example, the control unit 10 recognizes the state of the light-receiving unit 60 when the status signal is stored in the storage area 39.

[0044] In this example, the control unit 10 generates a channel selection signal CH that selects a light-emitting element 72 to emit light at a timing corresponding to the light-emitting control signal, based on at least one of a status signal indicating the state of the light-receiving unit 60 and a light-emitting control signal that controls the light-emitting timing of the light-emitting unit 70. The status signal is a signal that includes information indicating whether the light-receiving unit 60 is in a state where it can measure light from an object, or information to enable the light-receiving unit 60 to measure. In this example, a scan start signal SS, which indicates whether the light-receiving unit 60 is in a state where it can receive reflected light, is an example of a status signal. Also, a light-emitting instruction signal LC is an example of a light-emitting control signal.

[0045] The memory area 39 is composed of memory elements such as RAM, ROM, registers, and flip-flops. As shown in Figures 6 and 12 described later, the memory area 39 is provided as part of the pulse generation circuit 30 and the channel control circuit 40, or in a memory shared by the pulse generation circuit 30 and the channel control circuit 40. The memory area 39 stores mode determination information and status signals (scan start signal SS in this example) from the light receiving unit 60 and the control unit 10. The mode determination information may be included in the scan start signal SS.

[0046] Mode determination information refers to information that determines whether the generation of the scan start signal SS is performed by the light receiving unit 60 or the control unit 10. For example, a specific bit of the mode determination information may be pre-assigned for use in communication determination. If the mode determination bit is "0", the light receiving unit 60 generates the scan start signal SS and inputs it to the control unit 10. Alternatively, if the mode determination bit is "1", the control unit 10 generates the scan start signal SS and inputs it to the light receiving unit 60. The logical value of the mode determination bit may be reversed. Mode determination processing using the mode determination bit determines which of the above modes the distance measuring device 100 will operate in. Mode determination information may be pre-set in the storage area 39 by the user, etc. In this example, the distance measuring device 100 has "0" set as the mode determination bit, and the scan start signal SS is generated by the light receiving unit 60. If the mode determination bit is "0", the control unit 10 may notify the light receiving unit 60 of this. The light receiving unit 60 may generate a scan start signal SS in response to an operation instruction signal ST, provided that the mode determination bit is "0".

[0047] In this example, the control unit 10 generates a channel selection signal CH in the channel control circuit 40 based on the scan start signal SS (status signal). Furthermore, the pulse generation circuit 30 generates a pulse signal LP in response to the light emission instruction signal LC, which is synchronized with the scan start signal SS. Therefore, the channel selection signal CH and the pulse signal LP can be synchronized with high precision.

[0048] Figure 2 is a timing chart showing example waveforms of each signal. In this example, the MCU unit 20 generates an operation instruction signal ST. In this example, the operation instruction signal ST repeatedly defines a period during which the light receiving unit 60 can receive light (for example, a period of logical value H) and a period during which it cannot receive light (for example, a period of logical value L).

[0049] The light-receiving unit 60 transitions between a light-receiving state and a light-receiving state in response to the operation instruction signal ST. In this example, the light-receiving unit 60 becomes light-receiving during the period when the operation instruction signal ST indicates H logic, and becomes light-receiving non-functioning during the period when the operation instruction signal ST indicates L logic. The light-receiving unit 60 outputs a scan start signal SS indicating whether or not it can receive light. In this example, the scan start signal SS indicates H logic when the light-receiving unit 60 is in a light-receiving state, and L logic when it is in a light-receiving non-functioning state. In this example, the scan start signal SS corresponds to the operation instruction signal ST delayed by a predetermined delay amount. In this specification, the period during which the light-receiving unit 60 is in a light-receiving state may be referred to as the scan period. One scan period is, for example, the period from when the scan start signal SS transitions to H logic until it transitions to L logic. As described above, the scan start signal SS is stored in the storage area 39 of the control unit 10.

[0050] In this example, the light-receiving unit 60 generates a light emission instruction signal LC to cause the light-emitting element 72 to emit light when it transitions to a light-receiving state. The light-receiving unit 60 may generate the light emission instruction signal LC such that the light-emitting element 72 emits light after a predetermined time has elapsed since the transition to a light-receiving state. The light emission instruction signal LC in this example has a pulse that is delayed by a predetermined time after the scan start signal SS transitions to high logic. The light-emitting element 72 emits light in response to this pulse. The light emission instruction signal LC may have multiple pulses during the period in which the scan start signal SS is maintained in high logic. In this case, any of the light-emitting elements 72 emit light multiple times during a single scan period. The light-receiving unit 60 may measure the intensity of the reflected light for each emission, or it may measure the sum of the intensities of the reflected light for multiple emission events.

[0051] The channel control circuit 40 outputs a channel selection signal CH in response to the scan start signal SS. In this example, the channel control circuit 40 stops outputting the channel selection signal to the light-emitting unit 70 when the status signal (scan start signal SS) stored in the memory area 39 is H logic (i.e., information indicating that the light-receiving unit 60 is in a state where it can measure light from an object, or information to enable the light-receiving unit 60 to measure). In this example, the channel control circuit 40 outputs a channel selection signal CH that sequentially specifies each channel of the light-emitting unit 70 each time the scan start signal SS transitions to L logic. The channel control circuit 40 may output a channel selection signal CH that is delayed by a predetermined time in relation to the edge of the scan start signal SS. When the scan start signal SS transitions to H logic, the channel control circuit 40 stops outputting the channel selection signal CH. This stops the updating of the channel selection signal CH input to the switch 82, preventing channel switching while the light-emitting unit 70 is running.

[0052] The channel control circuit 40 in this example outputs a digital signal indicating the channel number in binary or the like. In this case, the switch device 80 may have a decoder that converts the digital signal of the channel selection signal CH into control signals for each switch 82. For example, the switch device 80 may have multiple control lines that transmit control signals for each switch 82. The decoder may generate control signals that turn on one switch 82 and turn off the other switches 82 according to the channel selection signal CH, and transmit them to the respective control lines. The switch device 80 may have a register or the like that stores the channel number specified by the channel selection signal CH. By providing a decoder in the switch device 80, the control lines to each switch 82 can be shortened, and variations in the transmission delay time of the control signals for the switches 82 can be suppressed. As a result, the distance measuring device 100 can be operated at an even higher speed.

[0053] The switch device 80 turns on one of the switches 82 and off the other switches 82 in response to the scan start signal SS and the channel selection signal CH. In this example, when the input scan start signal SS transitions to high logic, the switch device 80 controls the switch 82 corresponding to the channel specified by the channel selection signal CH to be in the ON state and controls the other switches 82 to be in the OFF state. As described above, the switch device 80 may also read the channel number stored in a register or the like when the input scan start signal SS transitions to high logic. As described above, when one of the switches 82 is controlled to be in the ON state, the corresponding light-emitting element 72 becomes capable of emitting light. In the example in Figure 1, the corresponding charging capacitor 74 is charged.

[0054] The pulse generation circuit 30 generates a light emission pulse signal LP in response to the light emission instruction signal LC. The light emission instruction signal LC is generated in synchronization with the scan start signal SS. Therefore, the light emission pulse signal LP may be generated in synchronization with the scan start signal SS. The pulse generation circuit 30 may also generate the light emission pulse signal LP on the condition that the H logic scan start signal SS is stored in the memory area 39. In this example, the light emission pulse signal LP has pulses according to the timing when the light emission instruction signal LC transitions to H logic. In this example, the light emission pulse signal LP has pulses that are delayed by a predetermined time relative to each pulse of the light emission instruction signal LC. Each pulse of the light emission pulse signal LP is generated within the scan period. As shown in Figure 2, the light emission pulse signal LP may have multiple pulses in one scan period. The light emission pulse signal LP may have one or more pulses during the period in which any of the switches 82 is controlled to be ON, corresponding to one scan period.

[0055] As explained in Figure 1, the driver 50 is controlled to be ON during the period when the light emission pulse signal LP indicates H logic. When the driver 50 is controlled to be ON, the light-emitting element 72 (i.e., the light-emitting element 72 with the corresponding switch 82 ON) emits light.

[0056] As described above, the distance measuring device 100 in this example outputs a scan start signal SS to the control unit 10 indicating whether the light receiving unit 60 is in a state where it can measure light from an object. The control unit 10 stores the scan start signal SS in the storage area 39. The control unit 10 may update the scan start signal SS stored in the storage area 39 in response to the received scan start signal SS. In this case, the distance measuring device 100 may operate according to the logical value of the scan signal SS stored in the storage area 39. Alternatively, the control unit 10 may store a history of the received scan start signals SS. In this case, the distance measuring device 100 may operate according to the logical value of the latest scan start signal SS stored in the storage area 39.

[0057] The control unit 10 outputs a channel selection signal CH and an emission control signal (in this example, an emission pulse signal LP) to the light-emitting unit 70, in response to the scan start signal SS stored in the memory area 39 indicating that the light-receiving unit 60 is capable of receiving light. In other words, the light-emitting unit 70 in this example is driven according to the information that the scan start signal SS output from the light-receiving unit 60 indicates that the light-receiving unit 60 is in a state where it can measure reflected light from an object. Furthermore, in this example, both the timing at which the channel selection signal CH is generated and the timing at which the emission pulse signal LP is generated are based on the scan start signal SS. Therefore, the influence of variations in the operating time of the MCU unit 20 and the light-receiving unit 60 can be suppressed, and the channel selection signal CH and the emission pulse signal LP can be synchronized with high accuracy.

[0058] In response to the status signal stored in memory area 39 being different from both the information indicating that the light receiving unit 60 is in a state where it can measure light from an object and the information necessary to enable the light receiving unit 60 to measure (in this example, the scan start signal SS is L logic), the channel control circuit 40 outputs a new channel selection signal CH to the light emitting unit 70, and the pulse generation circuit 30 stops outputting the light emission control signal (light emission pulse signal LP) to the light emitting unit 70. As a result, the light emission process in that channel ends, and a channel selection signal CH is generated to specify the next channel. Then, the scan start signal SS transitions back to H logic, and processing is performed to emit light from the next channel.

[0059] In order to make the light-emitting element 72 emit light, it is necessary to generate a light emission pulse signal LC during the period when the corresponding switch 82 is in the ON state. Therefore, if there is a large variation in the delay time between the channel selection signal CH and the light emission pulse signal LP, a margin must be provided so that, for example, the period during which the switch 82 is controlled to be in the ON state is long enough to include the period of the light emission pulse signal LC. In this example, since the channel selection signal CH and the light emission pulse signal LP can be synchronized with high precision, this margin can be reduced, the scan period can be shortened, and the distance measuring device 100 can be operated at high speed.

[0060] Figure 3 shows an example of a distance measuring device 200 according to a comparative example. Components in Figure 3 that are denoted by the same reference numerals as in Figure 1 have the same functions as those in the example in Figure 1, unless otherwise specified. The distance measuring device 200 includes a control unit 10, an MCU unit 20, a light receiving unit 60, and a light emitting unit 70. The configuration of the light emitting unit 70 may be the same as that of the example in Figure 1. However, the MCU unit 20 in this example incorporates an operation control circuit 21 and a channel control circuit 40, and the light emitting unit 70 in this example does not have a decoder. The method of generating the channel selection signal CH and the light emission pulse signal LP in the distance measuring device 200 differs from that of the distance measuring device 100.

[0061] Figure 4 is a timing chart showing example waveforms of each signal in the distance measuring device 200. In this example, the operation control circuit 21 generates an operation instruction signal ST. The channel control circuit 40 generates a channel selection signal CH in response to the operation instruction signal ST. In this example, the channel control circuit 40 generates a channel selection signal CH for each channel of the light-emitting unit 70 and inputs it to the switch device 80.

[0062] In the example shown in Figure 4, the channel control circuit 40 generates selection signals from channel 0 to channel N, corresponding to channels 0 through N. During the period when each selection signal is in high logic, the corresponding switch 82 is controlled to the ON state. The channel control circuit 40 may transition the selection signal corresponding to the next channel to high logic each time the operation control signal ST transitions to low logic.

[0063] The light-receiving unit 60 generates a scan start signal SS in response to the operation instruction signal ST. The light-receiving unit 60 inputs the scan start signal SS to the switch device 80. The light-receiving unit 60 also generates a light emission instruction signal LC in response to the scan start signal SS.

[0064] The switch device 80 controls one of the switches 82 to the ON state and the other switch 82 to the OFF state in response to the scan start signal SS and the channel selection signal CH. The pulse generation circuit 30 generates a light emission pulse signal LP in response to the light emission instruction signal LC and inputs it to the driver 50.

[0065] In the distance measuring device 200, both the timing of the generation of the channel selection signal CH and the timing of the generation of the light emission pulse signal LP are based on the operation instruction signal ST. The channel selection signal CH is transmitted from the operation control circuit 21 to the switch device 80 via the channel control circuit 40. The phase of the channel selection signal CH changes according to the variation in delay time along the transmission path. The light emission pulse signal LP, which is input to the driver 50, is transmitted from the operation control circuit 21 to the driver 50 via the light receiving unit 60 and the pulse generation circuit 30. The phase of the light emission pulse signal LP changes according to the variation in delay time along the transmission path. For this reason, it is difficult to accurately synchronize the channel selection signal CH and the light emission pulse signal LP in the distance measuring device 200.

[0066] Figure 5 illustrates the factors contributing to the variation in delay times of the light emission pulse signal LP and the channel selection signal CH in the comparative example distance measuring device 200 and the embodiment distance measuring device 100. In the comparative example distance measuring device 200, the light emission pulse signal LP passes through the MCU unit 20 (operation control circuit 21), the light receiving unit 60, the pulse generation circuit 30, and the driver 50, and is therefore affected by delays in each component. On the other hand, the channel selection signal CH passes through the operation control circuit 21 and the channel control circuit 40, and is therefore affected by delays in each component. Thus, in the distance measuring device 200, the light emission pulse signal LP and the channel selection signal CH pass through separate circuits after the operation control circuit 21. For this reason, variations in delay times tend to be large.

[0067] In the distance measuring device 100 of this embodiment, the light emission pulse signal LP passes through the MCU unit 20 (operation control circuit 21), the light receiving unit 60, the pulse generation circuit 30, and the driver 50. On the other hand, the channel selection signal CH passes through the MCU unit 20 (operation control circuit 21), the light receiving unit 60, and the channel control circuit 40. In other words, since the light emission pulse signal LP and the channel selection signal CH pass through the same path up to the light receiving unit 60, variations in delay time can be suppressed.

[0068] Figure 6 shows an example configuration of the light receiving unit 60 and the pulse generation circuit 30. In this example, the light receiving unit 60 includes a light receiving element array 62, a state control circuit 64, a measurement unit 66, and a first timing control unit 68. The light receiving element array 62 has a plurality of light receiving elements arranged two-dimensionally in a plane or curved surface. The light receiving elements are, for example, photoelectric conversion elements such as photodiodes, but are not limited to these. In this example, the pulse generation circuit 30 includes a pulse generation unit 34 and a preamplifier 36, and is configured to access a memory area 39 built into the control unit 10. The memory area 39 may be provided in the pulse generation circuit 30, or it may be provided in a control unit 10 other than the pulse generation circuit 30.

[0069] Figure 7 is a timing chart illustrating an example of the operation of the light receiving unit 60 and pulse generation circuit 30 shown in Figure 6. In this example, the light receiving unit 60 generates a scan start signal SS based on a mode determination bit stored in the memory area 39. The light receiving unit 60 inputs the scan start signal SS to the control unit 10, and this scan start signal SS is stored as a status signal in the memory area 39. The pulse generation unit 34 makes it possible to receive the light emission instruction signal LC only during the period when the status signal is in high logic, that is, during the light-receiving period. The pulse generation unit 34 outputs a light emission pulse signal LP in response to the light emission instruction signal LC received during the light-receiving period.

[0070] The operation of the light receiving unit 60 and the pulse generation circuit 30 will be described in more detail. The state control circuit 64 inputs a scan start signal SS to the light receiving element array 62 in response to an operation instruction signal ST. The scan start signal SS is a signal that puts the light receiving element array 62 into a state where it can measure reflected light from an object. For example, the scan start signal SS is a signal that enables photoelectric conversion operation in a photoelectric conversion element. The scan start signal SS may be a signal that switches whether or not to connect the photoelectric conversion element to a power supply. The state control circuit 64 inputs the scan start signal SS to the channel control circuit 40 and the light emitting unit 70 by storing it in the memory area 39 of the control unit 10 as a state signal indicating the state of the light receiving unit 60.

[0071] The state control circuit 64 inputs a trigger signal TG to the first timing control unit 68 in response to the operation instruction signal ST. The trigger signal TG is a signal that defines the timing for illuminating the light-emitting element 72. The state control circuit 64 outputs the trigger signal TG in synchronization with the scan start signal SS. The trigger signal TG has a number of pulses corresponding to the number of times the light-emitting element 72 is illuminated during one scan period. The first pulse in the trigger signal TG may have a set delay amount with respect to the timing when the scan start signal SS transitions to H logic.

[0072] The first timing control unit 68 outputs a light emission instruction signal LC in response to the trigger signal TG. The light emission instruction signal LC may be a signal obtained by delaying the trigger signal TG.

[0073] The measurement unit 66 measures the distance to the object based on the light-receiving result of the reflected light in the light-receiving element array 62 and the light-emitting instruction signal LC. The measurement unit 66 may calculate the distance to the object based on the time from when light emission is instructed by the light-emitting instruction signal LC until the light-receiving element array 62 receives the reflected light.

[0074] The pulse generation unit 34 generates a light emission pulse signal LP with a preset pulse width in response to the light emission instruction signal LC. The preamplifier 36 adjusts the amplitude of the light emission pulse signal LP to a preset level and inputs it to the driver 50. When the driver 50 turns on in response to the light emission pulse signal LP, the light-emitting element 72 emits light.

[0075] In this example, the scan start signal SS, which controls the photodetector array 62 via the state control circuit 64, is used as the state signal for the photodetector 60. The channel control circuit 40 generates a channel selection signal CH in synchronization with the scan start signal SS. The trigger signal TG is also generated by the state control circuit 64 in synchronization with the scan start signal SS. Therefore, even if there is variation in the operating timing of the state control circuit 64, causing variation in the phase of the scan start signal SS, the influence on the relative phase between the channel selection signal CH and the light emission pulse signal LP can be suppressed.

[0076] Figure 8 shows another example of the configuration of the distance measuring device 100. The operation of the channel control circuit 40 in this example of the distance measuring device 100 differs from the other examples. Except for the operation of the channel control circuit 40, it is the same as any of the distance measuring devices 100 described herein.

[0077] The channel control circuit 40 in this example outputs a channel selection signal CH, similar to the example in Figure 1. The channel control circuit 40 also inputs the scan start signal SS and the channel selection signal CH to the light-emitting unit 70 in synchronization.

[0078] Since the channel control circuit 40 outputs the scan start signal SS and the channel selection signal CH in a synchronized state, the scan start signal SS and the channel selection signal CH can be synchronized with greater precision. In other words, since both the scan start signal SS and the channel selection signal CH are input to the switch device 80 via the channel control circuit 40, the effects of delay variations in the channel control circuit 40 can be suppressed, and the scan start signal SS and the channel selection signal CH can be synchronized with greater precision.

[0079] Figure 9 shows another example of the configuration of the distance measuring device 100. The distance measuring device 100 in this example differs from the other example in the MCU unit 20, pulse generation circuit 30, and light receiving unit 60. Except for the MCU unit 20, pulse generation circuit 30, and light receiving unit 60, it is the same as any of the distance measuring devices 100 described herein.

[0080] Figure 10 is a timing chart showing example waveforms of each signal in the example shown in Figure 9. In this example, based on the mode determination bit stored in the memory area 39, the control unit 10, more specifically the pulse generation circuit 30, generates a scan start signal SS and stores it in the memory area 39 as a status signal. The pulse generation circuit 30 enables the output of an emission pulse signal LP and outputs a pulse start signal PS only for the duration that the status signal is in H logic. This will be explained in more detail. In this example, the control unit 10 generates a status signal to control the light receiving unit 60 to a state where it can measure light from an object, and inputs it to the light receiving unit 60. In the example in Figure 9, the MCU unit 20 inputs an operation instruction signal ST to the pulse generation circuit 30. The pulse generation circuit 30 generates a scan start signal SS in response to the operation instruction signal ST. The scan start signal SS is an example of a status signal. The pulse generation circuit 30 inputs the scan start signal SS to the light receiving unit 60, the channel control circuit 40, and the switch device 80. The waveform of the scan start signal SS is similar to that of other distance measuring devices 100.

[0081] The pulse generation circuit 30 generates an emission pulse signal LP synchronized with the scan start signal SS. The waveform of the emission pulse signal LP is similar to that of other rangefinders 100.

[0082] The pulse generation circuit 30 may input a pulse start signal PS to the light receiving unit 60 in addition to the scan start signal SS. The pulse start signal PS may be the same signal as the light emission pulse signal LP. In other words, the pulse start signal PS is a signal that indicates the timing for emitting light from the light-emitting element 72. The measurement unit 66 of the light receiving unit 60 may measure the time from when the light-emitting element 72 emits light until the light receiving unit 60 receives the reflected light, based on the pulse start signal PS. That is, in this example, the distance measuring device 100 includes information that enables the light receiving unit 60 to measure when the scan start signal SS is received. The control unit 10 generates the scan start signal SS in response to the operation instruction signal ST and stores it in the memory area 39. In response to the storage of this scan start signal SS, the control unit 10 outputs a channel selection signal CH and a light emission control signal (light emission pulse signal LP in this example) to the light-emitting unit 70 to select which of the multiple light-emitting elements 72 to emit light. In other words, in this example, the light-emitting unit 70 is driven in response to the scan start signal SS output from the light-receiving unit 60 being information that enables the light-receiving unit 60 to measure.

[0083] The operation of the channel control circuit 40, the driver 50, and the light-emitting unit 70 is the same as in the example in Figure 2. For example, the channel control circuit 40 generates a channel selection signal CH based on a scan start signal SS, which is an example of a status signal. In the example in Figure 9, the light-receiving unit 60 is excluded from the transmission path between the light-emitting pulse signal LP and the channel selection signal CH. Therefore, the effects of delay variations and other factors within the light-receiving unit 60 are eliminated, and the light-emitting pulse signal LP and the channel selection signal CH can be synchronized with even greater precision.

[0084] Figure 11 is a diagram illustrating the factors causing variations in the delay times of the light emission pulse signal LP and the channel selection signal CH in the distance measuring device 100 according to the example in Figure 9. In the distance measuring device 100 of this example, the light emission pulse signal LP passes through the pulse generation circuit 30 and the driver 50. On the other hand, the channel selection signal CH passes through the pulse generation circuit 30 and the channel control circuit 40. In other words, since the light emission pulse signal LP and the channel selection signal CH pass through the same path up to the pulse generation circuit 30, variations in delay time can be suppressed.

[0085] Figure 12 shows an example configuration of the light receiving unit 60 and pulse generation circuit 30 in the example shown in Figure 9. The light receiving unit 60 in this example has a light receiving element array 62 and a measurement unit 66. The light receiving element array 62 in this example is the same as in other examples herein, except that it operates in response to a scan start signal SS from the pulse generation circuit 30. The measurement unit 66 in this example measures the time from the timing of the light emission pulse indicated by the pulse start signal PS from the pulse generation circuit 30 to the timing when the light receiving element array 62 receives reflected light.

[0086] Figure 13 is a timing chart showing example waveforms of each signal in the example shown in Figure 12. The configuration of the pulse generation circuit 30 in the example in Figure 12 is the same as in the example in Figure 6. However, in this example, the pulse generation unit 34 generates a scan start signal SS in response to the operation instruction signal ST and inputs it to the photodetector array 62, the channel control circuit 40, and the light-emitting unit 70.

[0087] The pulse generation unit 34 generates an illumination pulse signal LP and an illumination start signal PS in response to an operation instruction signal ST. The illumination pulse signal LP and the illumination start signal PS may be the same signal. The pulse generation unit 34 inputs the illumination pulse signal LP to the driver 50 via the preamplifier 36. As a result, the light-emitting element 72 emits light. The pulse generation unit 34 also inputs the illumination start signal PS to the measurement unit 66. As a result, the measurement unit 66 can detect the illumination timing of the light-emitting element 72.

[0088] Figure 14 shows another example configuration of the distance measuring device 100. This example differs from the example in Figure 9 in that the light receiving unit 60 outputs a light emission instruction signal LC in response to the scan start signal SS. The other structures are the same as those in Figure 9.

[0089] In this example, the light-receiving unit 60 controls the light-receiving element array 62 in accordance with the scan start signal SS. The light-receiving element array 62 may output a light emission instruction signal LC when it becomes ready to receive light in response to the scan start signal SS. In this example as well, a channel selection signal CH and a light emission pulse signal LP can be generated with the scan start signal SS as the reference.

[0090] Figure 15 shows another example of the configuration of the control unit 10. The control unit 10 in this example differs from the other examples described herein in that it includes a control chip 12. The structure other than the control chip 12 is the same as in any of the examples described herein. In Figure 15, the control chip 12 is applied to the structure shown in Figure 1, but the control chip 12 may also be applied to the structure of the other examples.

[0091] The control chip 12 includes a channel control circuit 40 and a pulse generation circuit 30. In other words, the channel control circuit 40 and the pulse generation circuit 30 in this example are formed on the same control chip 12. Forming them on the same control chip 12 may mean that they are formed on the same semiconductor substrate, or that they are integrated on the same semiconductor substrate. The control chip 12 may also be provided with other components of the control unit 10. For example, the control chip 12 may also be provided with a driver 50.

[0092] Each circuit formed inside the control chip 12 may operate in accordance with a common clock signal. This further reduces variations in the operating times of the channel control circuit 40 and the pulse generation circuit 30. As a result, the light emission pulse signal LP and the channel selection signal CH can be synchronized with even greater precision. In addition, each circuit formed inside the control chip 12 may be supplied with a common power supply voltage. Therefore, even if the power supply voltage fluctuates, the power supply voltage of each circuit will fluctuate similarly, and thus the operating timing of each circuit will fluctuate similarly.

[0093] In each example described herein, the channel control circuit 40 and the pulse generation circuit 30 may operate synchronously. As in this example, by providing the channel control circuit 40 and the pulse generation circuit 30 on a single chip, the operation of the two circuits can be easily synchronized. The control unit 10 may generate the light emission pulse signal LP in synchronization with the channel selection signal CH. For example, the light emission pulse signal LP and the channel selection signal CH may be output in synchronization with a common clock signal.

[0094] Figure 16 shows an example configuration of a switch device 80. In this example, the switch device 80 has multiple switches 82, a decoder 84, and a switch control circuit 86. The decoder 84 receives a channel selection signal CH as input. In this example, the channel selection signal CH is a digital signal that indicates the channel number in binary or the like. Based on the channel selection signal CH, the decoder 84 outputs a control signal having bits corresponding to each switch 82. In the example in Figure 16, the switch device 80 has three switches 82, and the control signal has 3 bits. For example, the control signal is a signal in which the bit corresponding to the switch 82 specified by the channel selection signal CH is 1, and the other bits are 0.

[0095] The switch control circuit 86 controls each switch 82 based on the scan start signal SS and the control signals from the decoder 84. For example, when the scan start signal SS transitions to L logic, the switch control circuit 86 reads which switch 82 is specified by the control signal from the decoder 84, and when the scan start signal SS transitions to H logic, it turns on the specified switch 82 and turns off the other switches 82.

[0096] Figure 17 is a timing chart illustrating another example of the operation of the switch device 80. The operation of the MCU unit 20 (operation control circuit 21), the light receiving unit 60, and the channel control circuit 40 is the same as in the example in Figure 2. As explained in Figure 1, etc., among the multiple light-emitting elements 72, the light-emitting element corresponding to the charged charging capacitor 74 emits light in response to the light emission pulse signal LP. As described above, the channel control circuit 40 sets the next channel (i.e., light-emitting element 72) to emit light when the scan start signal SS transitions to L logic.

[0097] In this example, the switch control circuit 86 detects the end timing of light emission from any of the light-emitting elements 72 and, based on the end timing, controls the switch 82 corresponding to the next light-emitting element 72 to be emitted to the ON state, thereby pre-charging the corresponding charging capacitor 74. In this example, the switch control circuit 86 starts charging the charging capacitor 74 of the next channel to be emitted, in accordance with the timing of the end of light emission from the currently emitted channel, regardless of the timing when the scan start signal SS transitions to H logic. This control shortens the time from the start of the next scan period until the start of light emission from the light-emitting elements 72. This allows the distance measuring device 100 to operate at an even higher speed.

[0098] As described above, the light-receiving unit 60 alternates between a state in which it can measure light from an object and a state in which it cannot measure light. This state can be detected by a status signal such as the scan start signal SS. The switch control circuit 86 may, after detecting the timing of the end of light emission from the light-emitting element 72, and before the light-receiving unit 60 becomes the next state in which it can measure light, control the switch 82 corresponding to the next light-emitting element 72 to be emitted to the ON state.

[0099] The switch control circuit 86 may detect the termination timing of light emission from the light-emitting element 72 based on a status signal. In the example shown in Figure 17, the switch control circuit 86 may detect the timing te3 when the scan start signal SS transitions to L logic as the termination timing. The switch control circuit 86 may also detect the timing te1 when the operation instruction signal ST transitions to L logic as the termination timing. The switch control circuit 86 may also detect the termination timing based on a light emission control signal such as a light emission pulse signal LP or a light emission instruction signal LC. For example, the switch control circuit 86 may detect the timing te2 of the trailing edge of the last pulse within the scan period among the pulses of the light emission pulse signal LP as the termination timing.

[0100] The switch control circuit 86 may control the switch 82 of the channel that should next emit light to the ON state when a preset time D1 has elapsed from the detected termination timing. Time D1 may be measured by a counter that counts clock pulses or the like. In the example in Figure 17, the switch 82 of the first channel is controlled to the ON state at timing ts1. Time D1 may be shorter than the time from when the scan start signal SS transitions to L logic until it transitions to H logic. Timing ts1 is earlier than timing ts2 when the switch 82 of the first channel is controlled to the ON state in examples such as Figure 2. Timing ts1 may be earlier than timing tp1 when the scan start signal SS transitions to H logic to start the next channel period. This type of control allows the timing at which the light-emitting element 72 can start emitting light to be advanced, and the operation of the distance measuring device 100 can be sped up. In addition, the charging time of the charging capacitor 74 can be extended, so even if the ON resistance of the switch 82 is relatively high, the amount of charge in the charging capacitor 74 can be secured. Therefore, the cost of switch 82 can be reduced, or the circuit size can be reduced by using a smaller switch 82.

[0101] In the example in Figure 17, the period 0ch_ON when switch 82-0 is ON and the period 1ch_ON when switch 82-1 is ON are separate. In other examples, the end of period 0ch_ON and the beginning of period 1ch_ON may overlap. In other words, there may be a period when both switches 82 are ON at the same time. However, even in this case, period 1ch_ON starts after the light emission of the light-emitting element 72 of channel 0 has finished.

[0102] Figure 18 shows another example of the configuration of the pulse generation circuit 30. The pulse generation circuit 30 in this example has a correction information storage unit 38. The structure other than the correction information storage unit 38 is the same as in any of the examples described herein.

[0103] The correction information storage unit 38 stores information for correcting the pulse characteristics of the light emission pulse signal LP generated by the pulse generation unit 34. The correction information storage unit 38 may store information for correcting at least one of the phase (or delay amount), pulse width, and pulse amplitude of each pulse in the light emission pulse signal LP.

[0104] For example, the correction information storage unit 38 may store a delay amount for the light emission pulse signal LP in order to correct for variations in the transmission time of the signal transmission path from the light receiving unit 60 to the driver 50. The transmission time of the transmission path may be measured when the distance measuring device 100 is shipped or during actual operation. The correction information storage unit 38 may store a delay amount for the light emission pulse signal LP so that the transmission time is within a predetermined allowable range. In addition, the correction information storage unit 38 may store a delay amount for the light emission pulse signal LP so that the difference between the timing at which the channel selection signal CH is input to the switch device 80 and the timing at which the light emission pulse signal LP is input to the driver 50 is within a predetermined allowable range. The correction information storage unit 38 may store information to correct the pulse width and pulse amplitude of the light emission pulse signal LP so that the light emission intensity and light emission time of the light-emitting element 72 are within a predetermined allowable range.

[0105] The correction information storage unit 38 may store correction information for each channel of the light-emitting unit 70. This correction information may be, for example, information that corrects for variations in at least one of the light emission delay time, light emission intensity, and light emission pulse width of the light-emitting element 72 of each channel. In this case, a channel selection signal CH may be input to the pulse generation circuit 30. The pulse generation unit 34 may correct the light emission pulse signal LP using the correction information corresponding to the channel selection signal CH. In this case, the correction information may be set by the manufacturer or user of the distance measuring device 100, and the correction information obtained by actually measuring the light emission and calculating the difference between the actual light emission characteristics for each channel of the light-emitting unit 70 and at least one of the ideal light emission delay time, light emission intensity, and light emission pulse width may be stored in the correction information storage unit 38. Alternatively, for example, a correction mode may be provided, a reference setting value may be given for at least one of the ideal light emission delay time, light emission intensity, and light emission pulse width, the channels may be automatically lit, data of the actual light emission characteristics may be acquired, the difference from the reference value may be automatically calculated and stored as correction information in the correction information storage unit 38.

[0106] The delay or pulse width of the light emission pulse signal LP can be adjusted, for example, by a DLL circuit. However, the means for adjusting the delay or pulse width is not limited to a DLL. Also, when adjusting the pulse amplitude, the power supply voltage supplied to the preamplifier 36 may be adjusted.

[0107] Figure 19 shows an example configuration in which a power supply circuit 110 that supplies power supply voltage to the light-emitting unit 70 and a power supply control unit 120 are provided. The power supply circuit 110 may have, for example, a DC-DC converter. The power supply control unit 120 adjusts the magnitude of the power supply voltage generated by the power supply circuit 110.

[0108] A channel selection signal CH may be input to the power control unit 120. The power control unit 120 may adjust the power supply voltage of the power supply circuit 110 for each channel specified by the channel selection signal CH. In other words, the power control unit 120 may change the power supply voltage of the power supply circuit 110 depending on which switch 82 the switch device 80 controls to be ON. By adjusting the power supply voltage for each channel of the light-emitting unit 70, variations in light intensity and other characteristics caused by variations in the characteristics of the light-emitting element 72, the charging capacitor 74, and the switch 82 can be suppressed.

[0109] Figure 20 shows an example of the configuration of the power control unit 120. In this example, the power control unit 120 includes a monitor circuit 122, an AD conversion unit 124, a comparison unit 126, and a reference voltage generation unit 128. The monitor circuit 122 detects analog values ​​in the light-emitting unit 70, such as the power supply voltage output by the power supply circuit 110, the amplitude and pulse width of the light-emitting pulse of the light-emitting element 72, and the voltage of the charging capacitor 74.

[0110] The AD conversion unit 124 converts the analog value detected by the monitor circuit 122 into a digital value. The comparison unit 126 compares the digital value output by the AD conversion unit 124 with a preset value. The reference voltage generation unit 128 adjusts the power supply voltage of the power supply circuit 110 based on the comparison result in the comparison unit 126. The reference voltage generation unit 128 adjusts the power supply voltage so that the digital value output by the AD conversion unit 124 approaches the preset value.

[0111] Figure 21 shows another example of the configuration of the switch device 80. The switch device 80 in this example has a charge adjustment circuit 87. The other structures are the same as in other examples described herein. The charge adjustment circuit 87 adjusts the amount of charge to each charging capacitor 74 by adjusting the duration for which each switch 82 is ON.

[0112] In the examples shown in Figures 1 to 20, during the scan period when the scan start signal SS indicates high logic, the switch 82 of the corresponding channel is controlled to be ON. In this example, the charging time to the charging capacitor 74 is shortened and the amount of charge is adjusted by transitioning the switch 82 to the OFF state during the scan period. If the light-emitting element 72 emits light multiple times during the scan period, the operation of turning the switch 82 ON, charging the charging capacitor 74, turning the switch 82 OFF, the light-emitting element 72 emitting light, turning the switch 82 ON, etc. is repeated according to the number of times the light is emitted. The charge adjustment circuit 87, like the power control unit 120, may adjust the amount of charge to each charging capacitor 74 based on the monitoring result of the analog value in the light-emitting unit 70. The amount of charge to the charging capacitor 74 may differ for each channel.

[0113] The period during which the charging adjustment circuit 87 controls switch 82 to the ON state may be measured by a counter or the like. Alternatively, the waveform of the scan start signal SS input to the switch control circuit 86 may be changed to L logic when switch 82 should be turned OFF, and to H logic when switch 82 should be turned ON.

[0114] In another example, the charge adjustment circuit 87 monitors the voltage of each charging capacitor 74 and may control the corresponding switch 82 to the OFF state when the voltage of the charging capacitor 74 reaches a set value. When the light-emitting element 72 stops emitting light, if there are still light emission counts remaining for the scan period, the switch 82 is switched to the ON state to recharge the charging capacitor 74. The amount of charge of the charging capacitor 74 can also be adjusted by this type of control.

[0115] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.

[0116] It should be noted that the execution order of operations, procedures, steps, and stages in the apparatus, systems, programs, and methods shown in the claims, specifications, and drawings is not explicitly stated as "before," "prior to," etc., and that these can be implemented in any order unless the output of a previous process is used in a later process. Even if the operation flow in the claims, specifications, and drawings is described using phrases such as "first," "next," etc. for convenience, it does not mean that it is essential to perform the operations in that order. [Explanation of symbols]

[0117] 10...Control unit, 12...Control chip, 20...MCU unit, 21...Operation control circuit, 30...Pulse generation circuit, 34...Pulse generation unit, 36...Preamplifier, 38...Correction information storage unit, 39...Storage area, 40...Channel control circuit, 50...Driver, 60...Light receiving unit, 62...Light receiving element array, 64...State control circuit, 66...Measurement unit, 68...First timing control unit 70...Light-emitting section, 72...Light-emitting element, 74...Charging capacitor, 80...Switching device, 82...Switch, 84...Decoder, 86...Switch control circuit, 87...Charging adjustment circuit, 100...Distance measuring device, 110...Power supply circuit, 120...Power supply control unit, 122...Monitor circuit, 124...AD conversion unit, 126...Comparison unit, 128...Reference voltage generation unit, 200...Distance measuring device

Claims

1. A light-emitting unit having multiple light-emitting elements that irradiate an object with light, A light-receiving unit that receives light from the aforementioned object, The system comprises a control unit configured to communicate with the light-emitting unit and the light-receiving unit, and having a memory area, The control unit is configured to communicate a status signal indicating the state of the light receiving unit with the light receiving unit, The status signal includes information indicating whether the light receiving unit is in a state where it can measure light from the object, or information to enable the light receiving unit to measure. The memory area stores the status signals, The control unit outputs to the light-emitting unit a channel selection signal to select which of the plurality of light-emitting elements to emit light, and a light emission control signal to control the light emission timing of the light-emitting unit, in accordance with the status signal stored in the memory area. The light-emitting unit is configured to receive the status signal from the light-receiving unit or the control unit. Ranging device.

2. The light-emitting unit is driven according to whether the input status signal is information indicating that the light-receiving unit is in a state where it can measure light from the object, or information that enables the light-receiving unit to measure. The distance measuring device according to claim 1.

3. The control unit, In accordance with the status signal stored in the memory area being information indicating that the light receiving unit is in a state where it can measure light from the object, or information that enables the light receiving unit to measure, the light emission control signal is output to the light emitting unit, and the output of the channel selection signal to the light emitting unit is stopped. If the status signal stored in the memory area is different from both the information indicating that the light receiving unit is in a state where it can measure light from the object and the information for enabling the light receiving unit to measure, the channel selection signal is output to the light-emitting unit and the output of the light emission control signal to the light-emitting unit is stopped. The distance measuring device according to claim 2.

4. The light receiving unit is A light-receiving element that measures light from the aforementioned object, A state control circuit that generates a scan start signal to control the light-receiving element, It has, The state control circuit inputs the scan start signal as the state signal to the control unit. A distance measuring device according to any one of claims 1 to 3.

5. The control unit, A scan start signal, which controls the light receiving unit to a state in which it can measure light from the object, is input to the light receiving unit as the status signal. The channel selection signal is generated based on the scan start signal. A distance measuring device according to any one of claims 1 to 3.

6. The control unit generates a light emission pulse signal to be supplied to the light-emitting element selected by the channel selection signal from among the plurality of light-emitting elements, in synchronization with the channel selection signal. A distance measuring device according to any one of claims 1 to 3.

7. The control unit generates the light emission pulse signal based on correction information for at least one of the light emission delay time, light emission intensity, and light emission pulse width of the light-emitting element for each channel. The distance measuring device according to claim 6.

8. The light receiving unit inputs the status signal to the light emitting unit and the control unit. The light-emitting unit receives the status signal from the light-receiving unit and the channel selection signal from the control unit. A distance measuring device according to any one of claims 1 to 3.

9. The control unit inputs the status signal and the channel selection signal to the light-emitting unit in a synchronized manner. A distance measuring device according to any one of claims 1 to 3.

10. The control unit, A channel control circuit that generates the channel selection signal, A pulse generation circuit that generates the aforementioned light emission pulse signal and A distance measuring device according to claim 6, having the following features.

11. The channel control circuit and the pulse generation circuit are formed on a single chip. The distance measuring device according to claim 10.

12. The control unit further includes a driver that is provided in common to the plurality of light-emitting elements and causes any of the plurality of light-emitting elements to emit light based on a light-emitting pulse signal corresponding to the light-emitting control signal, The light-emitting unit includes a plurality of switches provided corresponding to the plurality of light-emitting elements, a plurality of charging capacitors provided corresponding to the plurality of light-emitting elements, and a switch control circuit for controlling the plurality of switches. Of the plurality of switches, the switch selected by the channel selection signal is controlled to be in the ON state. Of the plurality of charging capacitors, the charging capacitor corresponding to the switch that is controlled to be in the ON state is charged. Among the plurality of light-emitting elements, the light-emitting element corresponding to the charged charging capacitor emits light in response to the light emission pulse signal. The switch control circuit detects the termination timing of light emission from any of the light-emitting elements, and based on the termination timing, controls the switch corresponding to the next light-emitting element to emit light to the ON state, thereby pre-charging the corresponding charging capacitor. A distance measuring device according to any one of claims 1 to 3.

13. The light receiving unit repeatedly switches between a state in which it can measure light from the object and a state in which it cannot measure light. The switch control circuit, after detecting the termination timing, controls the switch corresponding to the light-emitting element that should next emit light to be turned ON before the light-receiving unit becomes the next state capable of measurement. The distance measuring device according to claim 12.

14. The switch control circuit detects the termination timing based on the status signal. The distance measuring device according to claim 13.

15. The switch control circuit detects the termination timing based on the light emission control signal. The distance measuring device according to claim 14.

16. A switch device used in a distance measuring device, which has a light-emitting section having a plurality of light-emitting elements and a plurality of charging capacitors that irradiate an object with light, Multiple switches provided corresponding to the multiple light-emitting elements, A switch control circuit that controls the plurality of switches Equipped with, Of the aforementioned plurality of switches, the switch corresponding to the light-emitting element that should emit light according to the input channel selection signal is controlled to be in the ON state. Of the plurality of charging capacitors, the charging capacitor corresponding to the switch that is controlled to be in the ON state is charged. Among the plurality of light-emitting elements, the light-emitting element corresponding to the charged charging capacitor emits light in response to the input light emission pulse signal. The switch control circuit detects the termination timing of light emission from any of the light-emitting elements, and based on the termination timing, controls the switch corresponding to the next light-emitting element to emit light to the ON state, thereby pre-charging the corresponding charging capacitor. Switching device.

17. A control chip used in a distance measuring device comprising a light-emitting unit having multiple light-emitting elements that irradiate an object with light, and a light-receiving unit that receives light from the object, A channel control circuit that generates a channel selection signal to select the light-emitting element that should emit light, A pulse generation circuit generates a light emission pulse signal to be supplied to the light-emitting element selected by the channel selection signal, based on correction information for at least one of the light emission delay time, light emission intensity, and light emission pulse width of the light-emitting element for each channel, in synchronization with the channel selection signal. A control chip equipped with this feature.

Images