Light-emitting device and distance measurement device

Abstract

[Problem] To detect failure of a light-emitting element as quickly as possible. [Solution] This light- emitting device comprises: a plurality of light-emitting elements arranged in a two-dimensional array and each having first and second terminals; a plurality of first terminal wires including N first wires (N is an integer of 2 or more) extending in a first direction and N second wires extending in a second direction crossing the first direction and respectively electrically connected to the N first wires, the plurality of first terminal wires electrically connected to the first terminal of the light-emitting elements; a plurality of second terminal wires electrically connected to the second terminal of the light-emitting elements and each electrically connected to N of the light-emitting elements; and at least one failure detection circuit electrically connected to one of the plurality of first terminal wires and the plurality of second terminal wires and detecting abnormality in a light-emitting element that is not to emit light.

Description

Light emitting device and distance measuring device

[0001] The present disclosure relates to a light emitting device and a distance measuring device.

[0002] LiDAR (Light Detection and Ranging) is one method of obtaining distance information. LiDAR shines light onto an object for which distance information is desired, and estimates the distance based on information obtained from the light reflected by the object. In recent years, attention has been focused on solid-state LiDAR, which has no physically moving parts in the light-emitting and light-receiving units. In solid-state LiDAR, for example, an array of light-emitting units can be used to select the location from which light is emitted, and light is projected onto the intended irradiation area. By sequentially switching the light-emitting locations within the light-emitting unit, it is possible to realize a light-emitting system that scans light in a two-dimensional area without a physical scanning mechanism. The light of the light-emitting channel selected by the light-emitting system is reflected by the object and received at the location corresponding to the light-emitting channel of the light-receiving element.

[0003] This type of light-emitting system includes a light source with light-emitting elements arranged in an array and a drive circuit, and is capable of driving the light-emitting elements of a selected light-emitting channel. The absence of any physically moving parts reduces the risk of breakdowns in situations where high reliability is required (see Patent Document 1). Patent Document 1 proposes a method of arranging multiple anodes and cathodes in a matrix and driving them individually.

[0004] Special Publication No. 2022-526998

[0005] As in Patent Document 1, a problem with existing light-emitting systems in which multiple anodes and cathodes are arranged in a matrix and driven individually is that when one of the light-emitting elements emits light, a reverse bias is applied to the other light-emitting elements connected to the same cathode. The non-target light-emitting elements to which a reverse bias is applied may experience a reverse bias short circuit (hereinafter also referred to as a short circuit abnormality), in which the anode and cathode are short-circuited. When the cathode of a light-emitting element to emit light is connected to the cathode of a non-target light-emitting element that has experienced a short circuit abnormality, the current flowing from the anode to the cathode of the target light-emitting element may flow from the cathode of the non-target light-emitting element that has experienced the short circuit abnormality to the anode, preventing the capacitor provided to cause the target light-emitting element to emit light in a pulsed manner from being charged, potentially preventing the target light-emitting element from emitting light. Furthermore, if the current flowing from the anode to the cathode of the light-emitting element to be emitted flows from the cathode to the anode of the non-light-emitting element that has experienced a short circuit, the capacitor provided to cause the non-light-emitting element to emit pulsed light may be unintentionally charged, and the charge on this capacitor may cause the non-light-emitting element to emit light. In this case, the light-emitting element to be emitted and the non-light-emitting element may emit light simultaneously, causing the light intensity of the light-emitting device to be higher than expected, which may violate safety standards for laser light.

[0006] Therefore, from the viewpoint of eye safety, it is desirable to detect a fault such as a short circuit in a light-emitting element before the light-emitting element emits light. Also, before a complete short circuit occurs in a light-emitting element, there is a period during which a small amount of leakage current flows from the cathode to the anode, so it is desirable to be able to detect a fault within this period.

[0007] Therefore, the present disclosure provides a light emitting device and a distance measuring device that can quickly detect a failure in a light emitting element.

[0008] In order to solve the above problems, according to the present disclosure, there is provided a light emitting device including: a plurality of light emitting elements arranged in a two-dimensional array, each having a first and a second terminal; N first wirings (N is an integer of 2 or more) extending in a first direction; and N second wirings extending in a second direction intersecting the first direction and electrically connected to the N first wirings, respectively; a plurality of first terminal wirings electrically connected to the first terminals of the light emitting elements; a plurality of second terminal wirings electrically connected to the second terminals of the light emitting elements, each electrically connected to N of the light emitting elements; a plurality of selection circuits electrically connected to one of the plurality of first terminal wirings and the plurality of second terminal wirings, and selecting the light emitting elements to be light emitting; a plurality of drive circuits electrically connected to the other of the plurality of first terminal wirings and the plurality of second terminal wirings, and driving the plurality of light emitting elements; and a plurality of capacitors electrically connected to the one of the plurality of first terminal wirings and the plurality of second terminal wirings, and storing electric charges to be supplied to the plurality of light emitting elements. and at least one fault detection circuit electrically connected to one of the plurality of first terminal wirings and the plurality of second terminal wirings, for detecting an abnormality in a light-emitting element that is not a target for emitting light.

[0009] The failure detection circuit may detect the abnormality in which the first terminal and the second terminal of the light-emitting element that is not a target for emitting light are short-circuited.

[0010] The failure detection circuit may detect an abnormality caused by at least a part of the current flowing through the light emitting element that is a light emitting target being a leakage current flowing through the light emitting element that is not a light emitting target.

[0011] The failure detection circuit may detect the abnormality before the corresponding drive circuit drives the light emitting element that is the light emitting target.

[0012] The failure detection circuit may be disposed for each of the plurality of first terminal wirings or the plurality of second terminal wirings.

[0013] Each of the plurality of fault detection circuits may include a comparator that outputs an abnormality detection signal when the voltage of the corresponding first terminal wiring or second terminal wiring is equal to or higher than a predetermined threshold voltage.

[0014] The power supply may further include a threshold generating circuit that generates the threshold voltage based on a reference voltage that has a voltage level higher than the threshold voltage.

[0015] The threshold generation circuit may have a variable impedance element capable of adjusting a voltage division ratio of the reference voltage, and may generate the threshold voltage by dividing the reference voltage at the voltage division ratio adjusted by the variable impedance element.

[0016] The variable impedance element may include a variable resistor.

[0017] The failure detection circuit may be arranged for each of two or more of the first terminal wirings or the second terminal wirings.

[0018] The fault detection circuit may include: a plurality of analog-to-digital converters that convert the voltages of the plurality of first terminal wirings or the plurality of second terminal wirings into digital signals, respectively; and an abnormality detection signal generation unit that generates an abnormality detection signal based on the plurality of digital signals output from the plurality of analog-to-digital converters.

[0019] The plurality of analog-to-digital converters may generate the digital signals in parallel during a period when the plurality of light-emitting elements are performing light-emitting operation, and the fault detection circuit may generate the abnormality detection signal indicating that at least one of the light-emitting elements that is not a light-emitting element has experienced an abnormality.

[0020] The fault detection circuit may include a switch that selects one of the plurality of first terminal wirings or the plurality of second terminal wirings, and an analog-to-digital converter that performs analog-to-digital conversion on the voltage of the first terminal wiring or the second terminal wiring selected by the switch to generate an abnormality detection signal.

[0021] The switch may select the plurality of first terminal wirings or the plurality of second terminal wirings in turn, and the fault detection circuit may generate the abnormality detection signal for the light-emitting element that is not to emit light and is connected to the plurality of first terminal wirings or the plurality of second terminal wirings selected in turn by the switch.

[0022] The device may further include a failure control circuit that stops the selection by the selection circuit connected to at least one of the non-target light-emitting element connected to the first terminal wiring or the second terminal wiring where the abnormality is detected and the target light-emitting element connected to this light-emitting element, and stops the driving of the drive circuit.

[0023] The present invention may further include a pulse generator that generates a pulse signal indicating that the abnormality has been detected, and the selection circuit connected to the light-emitting element that is the target of light emission and is connected to the first terminal wiring or the second terminal wiring in which the abnormality has been detected via a light-emitting element that is not the target of light emission may discharge the corresponding capacitor based on the pulse signal.

[0024] The fault control circuit may comprise: a first synchronization signal generator that generates a first synchronization signal that defines the timing for causing the plurality of light-emitting elements arranged in a two-dimensional array to emit light in sequence; and a second synchronization signal generator that generates a second synchronization signal that defines the timing for causing two or more light-emitting elements arranged in the first direction to emit light in sequence; and when the abnormality is detected, the fault control circuit may cause the first synchronization signal generator to stop generating the first synchronization signal and the second synchronization signal generator to stop generating the second synchronization signal.

[0025] The plurality of light-emitting elements may be surface-emitting laser elements.

[0026] The plurality of light-emitting elements may be VCSELs (Vertical Cavity Surface Emitting Lasers).

[0027] Furthermore, according to the present disclosure, a distance measuring device includes: a light emitting unit that emits light toward a subject; a light receiving unit that receives light that is the emitted light reflected by the subject; and a distance measuring unit that detects a distance to the subject based on the light emitted by the light emitting unit and the light received by the light receiving unit, wherein the light emitting unit includes: a plurality of light emitting elements that are arranged in a two-dimensional array, each having a first and a second terminal; N first wirings (N is an integer of 2 or more) extending in a first direction, and N second wirings that extend in a second direction intersecting the first direction and are electrically connected to the N first wirings, respectively; a plurality of first terminal wirings that are electrically connected to the first terminals of the light emitting elements; a plurality of second terminal wirings that are electrically connected to the second terminals of the light emitting elements, each second terminal wiring being electrically connected to N of the light emitting elements; a plurality of selection circuits that are electrically connected to one of the first and second terminal wirings and that select the light emitting elements to be light emitting; and a plurality of drive circuits that are electrically connected to the other of the first and second terminal wirings and that drive the plurality of light emitting elements. A distance measuring device is provided, which includes: a plurality of capacitors electrically connected to one of the first and second terminal wirings and storing electric charges to be supplied to the plurality of light-emitting elements; and a fault detection circuit electrically connected to one of the first and second terminal wirings and detecting an abnormality in which the anode and cathode of a light-emitting element that is not to emit light are short-circuited.

[0028] 1 is a circuit diagram of a light-emitting device according to a first embodiment. FIG. 2 is a circuit diagram showing the connection relationship between a selection circuit, a light-emitting element, a drive circuit, and a failure detection circuit. FIG. 3 is a diagram showing the charging operation of a capacitor in normal conditions. FIG. 4 is a diagram showing the light-emitting operation of a light-emitting element in normal conditions. FIG. 5 is a diagram showing the charging operation of a capacitor when a light-emitting element has failed. FIG. 6 is a diagram showing a first configuration example of a failure detection circuit according to the first embodiment. FIG. 7 is a diagram showing a first configuration example of a failure detection circuit according to the first embodiment. Graphs showing electrical characteristics of a light-emitting element in normal and failed conditions. Graphs showing an example of adjusting a variable impedance element. Block diagram showing the configuration of a failure control circuit according to the first embodiment. Flowchart showing the light-emitting operation of the light-emitting device according to the first embodiment. Timing charts of each signal in the light-emitting operation of the light-emitting device according to the first embodiment. Timing charts of each signal when a light-emitting element has failed. Timing charts of each signal at a stage before a light-emitting element will fail. Cross-sectional view showing an example of the cross-sectional structure of a light-emitting device with a VCSEL structure. FIG. 8 is a diagram showing the configuration of a failure detection circuit according to a second embodiment. FIG. 9 is a diagram showing the configuration of a failure detection circuit according to a third embodiment. Cross-sectional view of a light-emitting device. Block diagram showing an example configuration of a distance measuring device as an implementation example of a light-emitting device according to the present embodiment. The present invention relates to a vehicle control system, a vehicle exterior information detection unit, and an imaging unit.

[0029] Hereinafter, embodiments of a light emitting device and a distance measuring device will be described with reference to the drawings. The following description will focus on the main components of the light emitting device and the distance measuring device, but the light emitting device and the distance measuring device may include components and functions that are not shown or described. The following description does not exclude components and functions that are not shown or described.

[0030] (First Embodiment) Fig. 1 is a circuit diagram of a light-emitting device 1 according to a first embodiment. As shown in Fig. 1, the light-emitting device 1 according to the first embodiment includes a plurality of light-emitting elements 23 arranged in a two-dimensional array and a plurality of transistors 24 electrically connected to these light-emitting elements 23. These transistors 24 are, for example, N-type MOS (Metal-Oxide-Semiconductor) transistors. Fig. 1 shows an example in which the light-emitting device 1 according to the first embodiment includes 9 x 9 light-emitting elements 23 and 9 x 9 transistors 24. Therefore, the light-emitting device 1 shown in Fig. 1 includes a 9ch x 9ch light-emitting element array. The number of channels in the light-emitting element array is arbitrary.

[0031] 1 , the light-emitting device 1 according to the first embodiment further includes a first anode wiring 31, a second anode wiring 32, a third anode wiring 33, a plurality of first capacitors 34, a plurality of second capacitors 35, a plurality of third capacitors 36, a first selection circuit 37, a second selection circuit 38, a third selection circuit 39, a plurality of cathode wirings 41, and a plurality of gate wirings 42. The first to third anode wirings 31 to 33 are an example of the first terminal wiring of the present disclosure, and the cathode wiring 41 is an example of the second terminal wiring of the present disclosure. The first to third capacitors 34 to 36 are an example of the first to Nth capacitors of the present disclosure, and the first to third selection circuits 37 to 39 are an example of the first to Nth selection circuits of the present disclosure (N is an integer of 2 or more). FIG. 1 shows an example where N is 3.

[0032] The first terminal wirings include N first wirings 31a, 32a, and 33a (N is an integer of 2 or greater) extending in a first direction X, and N second wirings 31b, 32b, and 33b extending in a second direction Y intersecting the first direction X and electrically connected to the N first wirings 31a, 32a, and 33a, respectively. FIG. 1 shows an example where N=3. The first terminal wirings are electrically connected to first terminals of a plurality of light-emitting elements 23. In this specification, the first wirings 31a and the second wirings 31b connected to each other are referred to as first anode wirings 31, the second wirings 32a and 32b connected to each other are referred to as second anode wirings 32, and the third wirings 33a and 33b connected to each other are referred to as third anode wirings 33. In this specification, the first direction X may be referred to as the horizontal direction, and the second direction Y may be referred to as the vertical direction.

[0033] The light emitting device 1 according to the first embodiment includes M (M is an integer of 1 or more) sets of the first to third anode wirings 31 to 33. Figure 1 shows an example where M=5.

[0034] The five sets of first anode wirings 31 include a plurality of (e.g., five) first wirings 31a each extending in the first direction X (horizontal direction) and arranged along the second direction Y (vertical direction), and a plurality of (e.g., five) second wirings 31b each extending in the second direction Y (vertical direction) and arranged along the first direction X (horizontal direction). In this specification, the first wirings 31a may be referred to as first horizontal wirings 31a, and the second wirings 31b may be referred to as first vertical wirings 31b.

[0035] The five sets of second anode wirings 32 each include a plurality of (e.g., five) first wirings 32a each extending in the first direction X (horizontal direction) and arranged along the second direction Y (vertical direction), and a plurality of (e.g., five) second wirings 32b each extending in the second direction Y (vertical direction) and arranged along the first direction X (horizontal direction). In this specification, the first wirings 32a may be referred to as second horizontal wirings 32a, and the first wirings 32b may be referred to as second vertical wirings 32b.

[0036] The five sets of third anode wirings 33 each include a plurality of (e.g., five) first wirings 33a each extending in the first direction X (horizontal direction) and arranged along the second direction Y (vertical direction), and a plurality of (e.g., five) second wirings 33b each extending in the second direction Y (vertical direction) and arranged along the first direction X (horizontal direction). In this specification, the first wirings 33a may be referred to as third horizontal wirings 33a, and the first wirings 33b may be referred to as third vertical wirings 33b.

[0037] 1 shows an example in which the light-emitting device 1 according to the first embodiment includes five first horizontal wires 31a, five first vertical wires 31b, five second horizontal wires 32a, five second vertical wires 32b, five third horizontal wires 33a, and five third vertical wires 33b. Fig. 1 also shows an example in which M sets of N first wires and N second wires are provided. The number of light-emitting elements 23 shown in Fig. 1 is N(M-2) x N(M-2), where N and M are symbols.

[0038] The first to third anode wirings 31 to 33 may include Ma sets of first to Nth horizontal wirings and Mb sets of first to Nth vertical wirings (Ma and Mb are integers of 2 or greater that satisfy Ma≠Mb). In this case, the number of light-emitting elements 23 in the light-emitting device 1 is N(Ma-2)×N(Mb-2).

[0039] The first selection circuit 37 includes transistors 37a and 37b connected in series. Similarly, the second selection circuit 38 includes transistors 38a and 38b connected in series. Similarly, the third selection circuit 39 includes transistors 39a and 39b connected in series. The transistors 37a, 38a, and 39a are, for example, P-type MOS transistors. The transistors 37b, 38b, and 39b are, for example, N-type MOS transistors. The transistors 37a, 38a, and 39a are examples of first switches of the present disclosure. The transistors 37b, 38b, and 39b are examples of second switches of the present disclosure.

[0040] [First to third anode wirings 31 to 33] In FIG. 1, in order to distinguish the first to third anode wirings 31 to 33 from one another, the first anode wiring 31 is shown by a thick solid line, the second anode wiring 32 is shown by a thick dashed line, and the third anode wiring 33 is shown by a thin solid line.

[0041] The first anode wiring 31 has a structure in which a plurality of first horizontal wirings 31a and a plurality of first vertical wirings 31b are arranged in a mesh pattern. These first horizontal wirings 31a and first vertical wirings 31b are electrically connected to each other at the locations where the first horizontal wirings 31a and first vertical wirings 31b intersect. Similarly, the second anode wiring 32 includes a plurality of second horizontal wirings 32a and a plurality of second vertical wirings 32b that are electrically connected to each other, and the third anode wiring 33 includes a plurality of third horizontal wirings 33a and a plurality of third vertical wirings 33b that are electrically connected to each other. Meanwhile, the first to third anode wirings 31 to 33 are electrically insulated from each other.

[0042] The first to third horizontal wirings 31a to 33a extend in the first direction X (horizontal direction) and are adjacent to each other in the second direction Y (vertical direction). Although the first to third horizontal wirings 31a to 33a extend linearly in the first direction X in FIG. 1, they may extend in a curved manner in the first direction X. That is, the first to third horizontal wirings 31a to 33a may include bent portions.

[0043] On the other hand, the first to third vertical wirings 31b to 33b extend in the second direction Y and are adjacent to each other in the first direction X. Although the first to third vertical wirings 31b to 33b extend linearly in the second direction Y in FIG. 1, they may also extend in a curved manner in the second direction Y. That is, the first to third vertical wirings 31b to 33b may also include bent portions.

[0044] FIG. 1 shows five sets of first to third horizontal wirings (first wirings) 31a to 33a. In FIG. 1, the first, second, third, fourth, and fifth sets of first to third horizontal wirings 31a to 33a are arranged in order from top to bottom. In each set, the first horizontal wiring 31a, the second horizontal wiring 32a, and the third horizontal wiring 33a are arranged in order from top to bottom. The first set of first to third horizontal wirings 31a to 33a and the fifth set of first to third horizontal wirings 31a to 33a are arranged so as to sandwich 9 × 9 light-emitting elements 23 therebetween. Each of the second to fourth sets of first to third horizontal wirings 31a to 33a is arranged along one row (nine light-emitting elements) 23.

[0045] FIG. 1 further shows five sets of first to third vertical wirings (second wirings) 31b to 33b. In FIG. 1, the first, second, third, fourth, and fifth sets of first to third vertical wirings 31b to 33b are arranged in order from left to right. In each set, the first vertical wiring 31b, the second vertical wiring 32b, and the third vertical wiring 33b are arranged in order from left to right. The first set of first to third vertical wirings 31b to 33b and the fifth set of first to third vertical wirings 31b to 33b are arranged so as to sandwich 9 × 9 light-emitting elements 23 therebetween. Each of the second to fourth sets of first to third vertical wirings 31b to 33b is arranged along one column (nine light-emitting elements) 23.

[0046] The anode of each light-emitting element 23 is electrically connected to one of the first to third vertical wirings 31b to 33b. For example, the light-emitting element 23 in the leftmost column is electrically connected to the first vertical wiring 31b in the second set of first to third vertical wirings 31b to 33b. The light-emitting element 23 in the rightmost column is electrically connected to the third vertical wiring 33b in the fourth set of first to third vertical wirings 31b to 33b. The anode of each light-emitting element 23 may be electrically connected to one of the first to third horizontal wirings 31a to 33a instead of being electrically connected to one of the first to third vertical wirings 31b to 33b. The anode is an example of a first terminal in the present disclosure.

[0047] [Cathode wiring 41] Each cathode wiring 41 extends in the first direction X and is electrically connected to the cathodes of three light-emitting elements 23. Specifically, each cathode wiring 41 is electrically connected to one light-emitting element 23 electrically connected to the first vertical wiring 31b, one light-emitting element 23 electrically connected to the second vertical wiring 32b, and one light-emitting element 23 electrically connected to the third vertical wiring 33b. These three light-emitting elements 23 are adjacent to each other in the first direction X. FIG. 1 shows 27 cathode wirings 41 for 81 light-emitting elements 23. The cathode is an example of a second terminal of the present disclosure.

[0048] Each light-emitting element 23 is provided between a corresponding anode wiring, i.e., any one of the first to third anode wirings 31 to 33, and a corresponding cathode wiring, i.e., any one of the plurality of cathode wirings 41. Each light-emitting element 23 emits light when a current flows between the corresponding anode wiring and the corresponding cathode wiring.

[0049] [Gate Wiring 42] Each gate wiring 42 extends in the first direction X and is electrically connected to the gates of three transistors 24. The sources of these three transistors 24 are electrically connected to the ground wiring (GND), and the drains of these three transistors 24 are electrically connected to the same single cathode wiring 41. These three transistors 24 form one drive circuit E. FIG. 1 shows 27 gate wirings 42 for 81 transistors 24.

[0050] Each drive circuit E is electrically connected to the cathodes of three light-emitting elements 23 via one cathode wiring 41. Each drive circuit E (output stage) E is used to drive the light-emitting elements 23 to generate (output) light from the light-emitting elements 23. For example, to generate light from a certain light-emitting element 23, a predetermined signal is applied to the gate wiring 42 of the drive circuit E for that light-emitting element 23. This brings the source and drain of each transistor 24 in that drive circuit E into conduction, allowing current to flow through that light-emitting element 23. When current flows through that light-emitting element 23, light is generated from that light-emitting element 23. The light-emitting device 1 shown in FIG. 1 includes 27 drive circuits E for 81 light-emitting elements 23.

[0051] [First to Third Selection Circuits 37 to 39] The first to third selection circuits 37 to 39 are electrically connected to the first to third horizontal wirings 31a to 33a of the first to third anode wirings 31 to 33, respectively. The first selection circuit 37 is used to select the light-emitting element 23 electrically connected to the first anode wiring 31 as the light-emitting element 23 that generates light. The second selection circuit 38 is used to select the light-emitting element 23 electrically connected to the second anode wiring 32 as the light-emitting element 23 that generates light. The third selection circuit 39 is used to select the light-emitting element 23 electrically connected to the third anode wiring 33 as the light-emitting element 23 that generates light. The first to third selection circuits 37 to 39 may be electrically connected to the first to third vertical wirings 31b to 33b of the first to third anode wirings 31 to 33, respectively, instead of the first to third horizontal wirings 31a to 33a of the first to third anode wirings 31 to 33.

[0052] The first selection circuit 37 includes a transistor 37a having a source electrically connected to the power supply wiring (VDD) and a transistor 37b having a source electrically connected to the ground wiring. The drains of the transistors 37a and 37b are electrically connected to the first anode wiring 31. The first selection circuit 37 is electrically connected to each of the first capacitors 34 via the first anode wiring 31.

[0053] The transistor 37a is used to store charge in each first capacitor 34. The transistor 37b is used to discharge charge from each first capacitor 34. When a predetermined signal is applied to the gate of the transistor 37a, charge is stored in each first capacitor 34. When a predetermined signal is applied to the gate of the transistor 37b, charge is discharged from each first capacitor 34. Therefore, according to this embodiment, by selectively storing charge in the first capacitor 34 of the first to third capacitors 34 to 36 using the first selection circuit 37, it is possible to pass a current to each light-emitting element 23 electrically connected to the first anode wiring 31.

[0054] 1 , the second and third selection circuits 38, 39 have the same structure as the first selection circuit 37. Therefore, according to this embodiment, by storing charge in each second capacitor 35 by the second selection circuit 38, it is possible to pass a current to each light-emitting element 23 electrically connected to the second anode wiring 32. Furthermore, according to this embodiment, by storing charge in each third capacitor 36 by the third selection circuit 39, it is possible to pass a current to each light-emitting element 23 electrically connected to the third anode wiring 33.

[0055] [First to Third Capacitors 34 to 36] The first to third capacitors 34 to 36 are electrically connected to the first to third anode wirings 31 to 33, respectively. Each first capacitor 34 stores charge to be supplied to the light-emitting element 23 electrically connected to the first anode wiring 31. Each second capacitor 35 stores charge to be supplied to the light-emitting element 23 electrically connected to the second anode wiring 32. Each third capacitor 36 stores charge to be supplied to the light-emitting element 23 electrically connected to the third anode wiring 33. According to this embodiment, by supplying charge to each light-emitting element 23 from the first to third capacitors 34 to 36, a current can be passed through each light-emitting element 23. Each of the first to third capacitors 34 to 36 has one electrode electrically connected to one of the first to third anode wirings 31 to 33 and the other electrode electrically connected to a ground wiring.

[0056] The light-emitting device 1 shown in FIG. 1 includes a light-emitting element array including 9×9 light-emitting elements 23 arranged in a two-dimensional array. As shown in FIG. 1, the shape of this light-emitting element array is roughly square in plan view. The light-emitting device 1 shown in FIG. 1 includes four sets of first to third capacitors 34-36 near the four sides of the square. Specifically, the light-emitting device 1 shown in FIG. 1 includes a first set of first to third capacitors 34-36 near the top side of the square, a second set of first to third capacitors 34-36 near the right side of the square, a third set of first to third capacitors 34-36 near the bottom side of the square, and a fourth set of first to third capacitors 34-36 near the left side of the square. These first to third capacitors 34-36 are examples of K sets of first to Nth capacitors of the present disclosure (K is an integer greater than or equal to 2). FIG. 1 shows an example where K is 4.

[0057] The first to third capacitors 34 to 36 of the first and third sets are electrically connected to the first to third horizontal wirings 31 a to 33 a of the first to third anode wirings 31 to 33, respectively. On the other hand, the first to third capacitors 34 to 36 of the second and fourth sets are electrically connected to the first to third vertical wirings 31 b to 33 b of the first to third anode wirings 31 to 33, respectively. As a result, the first to third capacitors 34 to 36 shown in FIG. 1 are electrically connected to the first to third anode wirings 31 to 33, respectively.

[0058] In each set, the first to third capacitors 34 to 36 are arranged in clockwise order. For example, the first capacitor 34, the second capacitor 35, and the third capacitor 36 of the first set are respectively arranged on the left, center, and right sides near the top edge of the square. The first capacitor 34, the second capacitor 35, and the third capacitor 36 of the second set are respectively arranged on the upper, center, and lower sides near the right edge of the square. As a result, the four sets of first to third capacitors 34 to 36 shown in FIG. 1 are arranged symmetrically with respect to the center of the square. The center of the square is approximately located at the position of the light-emitting element 23 in the fifth row and fifth column of the 9×9 light-emitting elements 23. In FIG. 1, the four sets of first to third capacitors 34 to 36 are arranged in four-fold rotational symmetry (90-degree rotational symmetry).

[0059] According to this embodiment, it is possible to set the average distance between each light-emitting element 23 and the corresponding four capacitors to a value close to the average distance between another light-emitting element 23 and the corresponding four capacitors.

[0060] For example, the light-emitting element 23 at the upper left is close to the first capacitor 34 above but far from the first capacitor 34 below. On the other hand, the light-emitting element 23 at the lower right is close to the third capacitor 36 on the right but far from the third capacitor 36 on the left. Therefore, the average distance between the light-emitting element 23 at the upper left and the four first capacitors 34 is close to the average distance between the light-emitting element 23 at the lower right and the four third capacitors 36. This is also true for the other 79 light-emitting elements 23. This makes it possible to reduce the difference in impedance between the wiring of different light-emitting elements 23 with respect to the anode wiring between each light-emitting element 23 and the corresponding four capacitors.

[0061] The light emitting device 1 of this embodiment may include the first to third capacitors 34 to 36 only near one, two, or three of the four sides of the square. However, in this case, it is desirable that the first to third capacitors 34 to 36 are also arranged symmetrically or nearly symmetrically with respect to the center of the square. Therefore, it is desirable that the light emitting device 1 of this embodiment include the first to third capacitors 34 to 36 on two or more of the four sides of the square. For example, by arranging two sets of the first to third capacitors 34 to 36 near the top and bottom sides of the square, it is possible to achieve an arrangement with two-fold rotational symmetry (180-degree rotational symmetry).

[0062] The light-emitting device 1 according to the first embodiment also includes a fault control circuit 70 and a first fault detection circuit, a second fault detection circuit, and a third fault detection circuit (not shown in FIG. 1 ). The first to third fault detection circuits are examples of the first to Nth fault detection circuits of the present disclosure. The first to third fault detection circuits are electrically connected to the first to third horizontal wirings 31a to 33a of the first to third anode wirings 31 to 33, respectively. The first fault detection circuit is used to detect an abnormality in a light-emitting element 23 that is not intended to emit light among the light-emitting elements 23 electrically connected to the first anode wiring 31. The second fault detection circuit is used to detect an abnormality in a light-emitting element 23 that is not intended to emit light among the light-emitting elements 23 electrically connected to the second anode wiring 32. The third fault detection circuit is used to detect an abnormality in a light-emitting element 23 that is not intended to emit light among the light-emitting elements 23 connected to the third anode wiring 33. In this specification, the first to Nth fault detection circuits may be collectively referred to as fault detection circuits 50. The failure control circuit 70 stops the light emitting operation of the light emitting device 1 based on the abnormality detected by the failure detection circuit 50 .

[0063] 2 is a circuit diagram showing the connection relationships among the selection circuits 37, 38, and 39, the light-emitting element 23, the drive circuit E, and the fault detection circuits 51, 52, and 53. Fig. 2 shows three selection circuits 37, 38, and 39 arranged in the second direction Y (vertical direction), and a plurality of light-emitting elements 23a, 23b, 23c, 23d, 23e, and 23f connected to two drive circuits Ea and Eb arranged in the first direction X (horizontal direction). Each of the two drive circuits Ea and Eb includes a transistor 24a or 24b.

[0064] 2, the first anode wiring 31 is called Anode1, the second anode wiring 32 is called Anode2, and the third anode wiring 33 is called Anode3. The current flowing through Anode1 is controlled by a first selection circuit 37 and a capacitor 34, the current flowing through Anode2 is controlled by a second selection circuit 38 and a capacitor 35, and the current flowing through Anode3 is controlled by a third selection circuit 39 and a capacitor 36. Also, in FIG. 2, the cathode wiring 41 connected to the drive circuit Ea is called Cathode1, and the cathode wiring 41 connected to the drive circuit Eb is called Cathode2.

[0065] As shown in Fig. 2, a first capacitor 34 is connected to a first selection circuit 37, a second capacitor 35 is connected to a second selection circuit 38, and a third capacitor 36 is connected to a third selection circuit 39. As shown in Fig. 1, a plurality of first capacitors 34 may be connected to the first selection circuit 37, but for simplicity, Fig. 2 shows an example in which one first capacitor 34 is connected to the first selection circuit 37. Similarly, one second capacitor 35 and one third capacitor 36 are connected to the second selection circuit 38 and the third selection circuit 39, respectively.

[0066] The first selection circuit 37 controls the charging and discharging of the first capacitor 34. The charge stored in the first capacitor 34 is used to cause all the light-emitting elements 23 (light-emitting elements 23a and 23d in FIG. 2 ) in the row connected to the first capacitor 34 to emit light. More specifically, the discharge current of the first capacitor 34 is supplied to the anodes (Anode 1) of the light-emitting elements 23a and 23d connected to the first capacitor 34. Similarly, the discharge current of the second capacitor 35 is supplied to the anodes (Anode 2) of all the light-emitting elements 23 (light-emitting elements 23b and 23e in FIG. 2 ) in the row connected to the second capacitor 35. Furthermore, the discharge current of the third capacitor 36 is supplied to the anodes (Anode 3) of all the light-emitting elements 23 (light-emitting elements 23c and 23f in FIG. 2 ) in the row connected to the third capacitor 36.

[0067] The drive circuit Ea controls the driving of the connected light-emitting elements 23 (light-emitting elements 23a, 23b, and 23c in FIG. 2). The drive circuit Ea includes a transistor 24a. The transistor 24a is connected between the cathodes of the light-emitting elements 23a, 23b, and 23c and a reference voltage (e.g., ground voltage) node. When the transistor 24a is turned on, the cathode (Cathode 1) voltage of the light-emitting elements 23 (23a, 23b, and 23c) connected to the drain of the transistor 24a drops to the reference voltage (e.g., GND). For example, if the first capacitor 34 is charged, the discharge current of the first capacitor 34 flows between the anode and cathode of the light-emitting element 23a connected to the first capacitor 34 and the drive circuit Ea, causing the light-emitting element 23a to emit light. Similarly, if the second capacitor 35 or the third capacitor 36 is charged, the drive circuit Ea drives the light-emitting element 23b or 23c to emit light. Similarly to the drive circuit Ea, the drive circuit Eb controls the driving of the light-emitting elements 23 (light-emitting elements 23d, 23e, and 23f in FIG. 2) connected to the drive circuit Eb by lowering the cathode (Cathode 2) voltage. The drive circuit Eb includes a transistor 24b. The transistor 24b is connected between the cathodes of the light-emitting elements 23d, 23e, and 23f and a reference voltage (e.g., ground voltage) node.

[0068] The first fault detection circuit 51 detects an abnormality in the light-emitting element 23 (light-emitting elements 23a and 23d in FIG. 2) connected to the first fault detection circuit 51. Normally, when the light-emitting element 23a is not the target for light emission, no current flows between the cathode and anode of the light-emitting element 23a because the resistance between the cathode and anode of the light-emitting element 23a is sufficiently large. However, if a fault causes the resistance value between the cathode and anode of the light-emitting element 23a to decrease, at least a portion of the current flowing through the light-emitting element 23 that is the target for light emission may flow between the cathode and anode of the light-emitting element 23a that is not the target for light emission. This current is referred to as leakage current in this specification.

[0069] The first fault detection circuit 51 detects an abnormality caused by a leakage current flowing between the cathode and anode of the light-emitting elements 23a and 23d when the anodes and cathodes of the light-emitting elements 23a and 23d are short-circuited and the light-emitting elements 23a and 23d are not intended to emit light. Similarly, the second fault detection circuit 52 detects an abnormality caused by the light-emitting elements 23 (light-emitting elements 23b and 23e in FIG. 2) connected to the second fault detection circuit 52. Furthermore, the third fault detection circuit 53 detects an abnormality caused by the light-emitting elements 23 (light-emitting elements 23c and 23f in FIG. 2) connected to the third fault detection circuit 53. While FIG. 2 shows an example in which two light-emitting elements 23 are connected to each of the first to third fault detection circuits 51 to 53, any number of light-emitting elements 23 may be connected to each of the first to third fault detection circuits 51 to 53.

[0070] As shown in FIG. 2, the fault detection circuits 51, 52, 53 (50) according to the first embodiment are arranged for each of the plurality of anode wirings.

[0071] 3A to 3C are diagrams illustrating the operation of the light-emitting device 1. FIGS. 3A and 3B show normal operation, while FIG. 3C shows operation during a fault. As an example, FIGS. 3A to 3C show operation when the light-emitting element 23a emits light. FIGS. 3A to 3C also illustrate the light-emitting element 23b, which is not intended to emit light. The anode (Anode 1) of the light-emitting element 23a, which is intended to emit light, is connected to the first capacitor 34, the first selection circuit 37, and the first fault detection circuit 51 via the anode wiring 31. The anode (Anode 2) of the light-emitting element 23b is connected to the second capacitor 35, the second selection circuit 38, and the second fault detection circuit 52 via the anode wiring 32. The cathodes (Cathode 1) of both the light-emitting element 23a and the light-emitting element 23b are connected to the drive circuit Ea.

[0072] 3A is a diagram showing the charging of the first capacitor 34. In the first selection circuit 37, the transistor 37a is turned on and the transistor 37b is turned off. As a result, charge is supplied to the first capacitor 34 from the power supply wiring (VDD), and the first capacitor 34 is charged. Also, in the drive circuit Ea, the transistor 24a is turned off. As a result, the cathode voltage of the light-emitting element 23a does not drop, and no current flows between the anode and cathode of the light-emitting element 23a.

[0073] 3A, the transistor 38a is turned off and the transistor 38b is turned on, thereby discharging the charge in the second capacitor 35 to the ground wiring GND and resetting the charge in the second capacitor 35.

[0074] 3B is a diagram showing the light emission of the light-emitting element 23a. After the first capacitor 34 is charged in FIG. 3A, the transistor 24a is turned on in the drive circuit Ea. This reduces the cathode voltage of the light-emitting element 23a. When the first capacitor 34 is discharged, a current flows between the anode and cathode of the light-emitting element 23a, causing the light-emitting element 23a to emit light.

[0075] 3A and 3B, when transistor 37a is turned on, the cathode of light-emitting element 23b, which is not the target for light emission, rises to a voltage level close to the power supply wiring (VDD) on the Anode1 side. Furthermore, when transistor 38b is turned on, the anode of light-emitting element 23b drops to a voltage level close to the ground voltage. This applies a reverse bias between the cathode and anode of light-emitting element 23b. However, since the resistance between the cathode and anode of light-emitting element 23b is sufficiently large in the normal state, no current flows between the cathode and anode of light-emitting element 23b.

[0076] 3C is a diagram showing the charging operation of the first capacitor 34 when the light-emitting element 23b has a short circuit. Compared to FIG. 3A, FIG. 3C differs from FIG. 3A in that the cathode and anode of the light-emitting element 23b are short-circuited. As described above, a reverse bias is applied to the light-emitting element 23b, and therefore the short circuit shown in FIG. 3C is also called a reverse bias short circuit.

[0077] The resistance between the cathode and anode of the light-emitting element 23b is approximately 0 due to the reverse bias short circuit. As a result, a leakage current (also called a reverse bias current) occurs, in which the current that should be supplied to the first capacitor 34 leaks to the cathode-anode side of the light-emitting element 23b via the light-emitting element 23a.

[0078] In FIG. 3C , the current that should be supplied to the first capacitor 34 flows to the ground wiring (GND) on the Anode 2 side via the light-emitting element 23b. As a result, the first capacitor 34 is not sufficiently charged, and when the drive circuit Ea drives the light-emitting element 23a, the amount of light emitted by the light-emitting element 23a decreases. Furthermore, the current that should be supplied to the first capacitor 34 is supplied to the second capacitor 35 via the light-emitting element 23b. As a result, the second capacitor 35 is charged, and when the drive circuit Ea drives the light-emitting element 23a, the light-emitting element 23b, which is not intended to emit light, may unexpectedly emit light. Furthermore, the first capacitor 34 is not sufficiently charged, and the light-emitting element 23a, which is intended to emit light, may emit light with reduced intensity or not emit light at all.

[0079] The second fault detection circuit 52 connected to the light-emitting element 23b detects an abnormality caused by leakage current flowing through the non-target light-emitting element 23b, while at least a portion of the current flowing through the target light-emitting element 23a is flowing through the non-target light-emitting element 23b, and outputs an abnormality detection signal. The abnormality detection signal output from the second fault detection circuit 52 turns off, for example, transistors 37a, 38a, and 24a. This stops the light-emitting operation of the failed light-emitting element 23b and the light-emitting element 23a affected by the failed light-emitting element 23b.

[0080] 3C , the second fault detection circuit 52 can detect leakage current before the corresponding drive circuit Ea drives the light-emitting element 23a to be emitted, i.e., at the stage of charging the first capacitor 34. This allows the light-emitting device 1 according to the first embodiment to stop the light-emitting operations of the light-emitting elements 23a and 23b before a decrease in the amount of light emitted by the light-emitting element 23a or unexpected light emission by the light-emitting element 23b that is not to be emitted becomes apparent.

[0081] 3A to 3C illustrate an example in which the fault detection circuit 50 detects a short-circuit abnormality in the light-emitting element 23, but the fault detection circuit 50 can also detect abnormalities (e.g., crosstalk) other than a short circuit in the light-emitting element 23. In other words, the fault detection circuit 50 can detect an abnormality in which the voltage of the corresponding anode wiring rises above a predetermined threshold value.

[0082] 4A is a diagram showing a first configuration example of the fault detection circuit 50 according to the first embodiment. The fault detection circuit 50 shown in FIG.

[0083] The comparator 61 compares a voltage signal input to a first input terminal with a voltage signal input to a second input terminal. The first input terminal is connected to a corresponding anode wiring, and the second input terminal is connected to an output node of a threshold generation circuit 62. The comparator 61 outputs an abnormality detection signal COUT when the voltage of the anode wiring is equal to or greater than a predetermined threshold voltage Vth output from the threshold generation circuit 62. For example, the comparator 61 in the fault detection circuit 52 of FIG. 3C outputs the abnormality detection signal COUT when the voltage of the corresponding anode wiring 32 is equal to or greater than the threshold voltage Vth.

[0084] The threshold generation circuit 62 generates the threshold voltage Vth based on a reference voltage LDVDD having a voltage level higher than the threshold voltage Vth. Specifically, the threshold generation circuit 62 has resistors R1 and R2. The resistors R1 and R2 are connected in series between a high-voltage node to which the reference voltage LDVDD is applied and a low-voltage (e.g., ground) node. One end of the resistor R1 is connected to the high-voltage node, and one end of the resistor R2 is connected to the low-voltage node. The other ends of the resistors R1 and R2 are connected to one of the input terminals of the comparator 61.

[0085] The threshold generation circuit 62 divides the reference voltage LDVDD using resistors R1 and R2 to generate a threshold voltage Vth, which is input to the comparator 61. While Fig. 4A shows an example in which the threshold generation circuit 62 has two resistors R1 and R2, the threshold generation circuit 62 may have three or more resistors. Furthermore, the threshold generation circuit 62 may divide the reference voltage LDVDD using an impedance element other than a resistor, such as a capacitor or an inductor, to generate the threshold voltage Vth.

[0086] The abnormality detection signal COUT output by the comparator 61 is input to a failure control circuit, which will be described later. The failure control circuit stops the light emitting operation of the light emitting device 1 based on the abnormality detected by the failure detection circuit 50.

[0087] FIG. 4B is a diagram illustrating a second exemplary configuration of the fault detection circuit 50 according to the first embodiment. The fault detection circuit 50a illustrated in FIG. 4B includes a threshold generation circuit 62a having a variable resistor RV instead of the resistor R2. The variable resistor RV constitutes a variable impedance element 63. The threshold generation circuit 62a can dynamically adjust the voltage division ratio of the reference voltage LDVDD by adjusting the impedance value (e.g., resistance value) of the variable impedance element 63 (variable resistor RV). The threshold generation circuit 62a divides the reference voltage LDVDD at the voltage division ratio adjusted by the variable impedance element 63 to generate a threshold voltage Vth, which is input to the comparator 61. The connection order of the variable impedance element 63 and the resistor R1 in FIG. 4B may be changed, or the resistor R1 may be replaced with another variable impedance element 63. The variable impedance element 63 may also be configured as a capacitor, an inductor, or the like.

[0088] As described above, the fault detection circuit 50 can detect an abnormality caused by a short circuit between the anode and cathode of the corresponding non-light-emitting light-emitting element 23. The fault detection circuit 50 outputs an abnormality detection signal. The abnormality detection signal is, for example, a binary signal. The abnormality detection signal is supplied to the fault control circuit 70 of FIG. 1. The fault detection circuit 50 can detect, as an abnormality, the stage at which the anode and cathode of the light-emitting element 23 are completely short-circuited and the resistance value becomes approximately zero. Alternatively, the fault detection circuit 50 can also detect, as an abnormality, the stage at which the anode and cathode of the light-emitting element 23 are about to be short-circuited, i.e., the stage at which the resistance value of the light-emitting element 23 gradually decreases and a small leakage current flows through the light-emitting element 23.

[0089] FIG. 5 is a graph showing the electrical characteristics of the light-emitting element 23 when it is normal and when it is faulty. In FIG. 5, the vertical axis represents current (I) and the horizontal axis represents voltage (V). FIG. 5 shows an IV curve W1 of the light-emitting element 23 in a normal state, an IV curve W2 of the light-emitting element 23 in a precursory state to a short-circuit anomaly, and an IV curve W3 of the light-emitting element 23 that has developed a short-circuit anomaly. Note that FIG. 5 shows an example in which the light-emitting element 23 has a linear IV curve (also called ohmic) in all states.

[0090] In a normal state, no current flows through the light-emitting element 23 unless a sufficiently high breakdown voltage VH (e.g., 10 V) is applied, as shown by curve W1. However, when the anode and cathode of the light-emitting element 23 begin to short-circuit, the breakdown voltage gradually decreases, and current begins to flow even at a voltage VM lower than VH, as shown by curve W2. This causes a small leakage current to be detected in the light-emitting element 23 that is not intended to emit light. Finally, when the anode and cathode of the light-emitting element 23 are completely short-circuited, leakage current is detected at a low voltage VL (e.g., approximately 0 V), as shown by curve W3.

[0091] The fault detection circuit 50a can detect minute leakage currents by adjusting the variable impedance element 63 to improve the resolution of fault detection. Figure 6 shows the anode voltage waveform of a light-emitting element 23 in which an abnormality has occurred. The vertical axis of Figure 6 represents the anode voltage of the light-emitting element 23 in which an abnormality has occurred, and the horizontal axis represents time. When a non-target light-emitting element 23, whose cathode is connected to the target light-emitting element 23, experiences a fault (e.g., a short-circuit fault), a leakage current flows through the anode wiring of the non-target light-emitting element 23 as the target light-emitting element 23 emits light, causing the anode voltage to rise. Therefore, a short-circuit fault may be determined to have occurred when the anode voltage of the non-target light-emitting element 23 exceeds a predetermined threshold voltage Vth (e.g., reference voltage LDVDD × 0.1). The threshold voltage Vth can be set arbitrarily, and as shown in Figure 6, the threshold voltage Vth can be as low as LDVDD × 0.00...01. Setting the threshold voltage Vth lower allows for faster fault detection, but there is also a risk of falsely identifying noise as a fault.

[0092] As described above, the variable impedance element 63 can arbitrarily vary the threshold voltage Vth, so the failure detection circuit 50a can detect both the stage when the light-emitting element 23 is completely short-circuited and the stage when there is a warning sign of a short-circuit. This allows the failure detection circuit 50a to stop the light-emitting operation of the light-emitting element 23 at the stage when there is a warning sign of a short-circuit anomaly.

[0093] 7 is a block diagram showing the configuration of a failure control circuit 70 according to the first embodiment. The failure control circuit 70 includes a failure detection control circuit 71, a master control circuit 72, a pulse generation control circuit 73, a charge control circuit 74, and a driver control circuit 75. The failure control circuit 70 controls the gate voltages of the PMOS transistors 37a, 38a, and 39a of the multiple selection circuits 37 to 39 and the gate voltages of the NMOS transistors 24 of the multiple drive circuits E. More specifically, the failure control circuit 70 controls the gate voltages of the PMOS transistors of the selection circuits connected to at least one of the non-emission light-emitting element 23 connected to the anode wiring in which an abnormality has been detected and the light-emitting element 23 connected to the non-emission light-emitting element, and the gate voltages of the NMOS transistors of the drive circuits, thereby stopping the light emission of these light-emitting elements 23.

[0094] The failure detection control circuit 71 inputs an error signal ERR to the pulse generation control circuit 73 based on the abnormality detection signal COUT input from the failure detection circuit 50, and instructs the failed light-emitting element 23 to stop emitting light. The failure detection control circuit 71 is also called a pulse generator because it generates a pulse signal (error signal ERR) indicating that an abnormality has been detected. The failure detection control circuit 71 has, for example, a latch unit that latches the abnormality detection signal COUT.

[0095] The master control circuit 72 controls the light emission timing of the light emitting device 1. The master control circuit 72 has a vertical synchronization signal generation circuit (first synchronization signal generator) 76, a horizontal synchronization signal generation circuit (second synchronization signal generator) 77, and a light emission control signal generation circuit 78. The vertical synchronization signal generation circuit 76 generates a vertical synchronization signal (first synchronization signal) VSYNC that determines the timing at which the plurality of light emitting elements 23 arranged in the light emitting element array are caused to emit light in sequence, and supplies the signal to the pulse generation control circuit 73. The horizontal synchronization signal generation circuit 77 generates a horizontal synchronization signal (second synchronization signal) HSYNC that determines the timing at which the plurality of light emitting elements 23 arranged in the first direction (horizontal direction) X are caused to emit light in sequence, and supplies the signal to the pulse generation control circuit 73. The light emission control signal generation circuit 78 generates a light emission trigger signal TRG_O that determines the timing at which the light emitting elements 23 are caused to emit light, and supplies the signal to the pulse generation control circuit 73. While the light emission trigger signal TRG_O is at a high level, the drive circuit E connected to the cathode of the light emitting element 23 to be emitted is driven, and while the light emission trigger signal TRG_O is at a low level, the capacitor on the anode wiring to which the anode of the light emitting element 23 to be emitted is connected is charged. The capacitor is discharged while the light emission trigger signal TRG_O is at a high level, and is then recharged when the light emission trigger signal TRG_O turns off.

[0096] The pulse generation control circuit 73 generates pulse signals for sequentially emitting light from the plurality of light-emitting elements 23 based on the vertical synchronization signal VSYNC, the horizontal synchronization signal HSYNC, and the light emission trigger signal TRG_O. The pulse generation control circuit 73 generates a pulse signal SEL_A for controlling the gate voltages of the plurality of PMOS transistors in the plurality of selection circuits and supplies it to the charge control circuit 74, and also generates a pulse signal SEL_C for controlling the gate voltages of the plurality of NMOS transistors in the plurality of drive circuits E and supplies it to the driver control circuit 75. When the error signal ERR is input, the pulse generation control circuit 73 generates the pulse signal SEL_A so as to stop charging of a capacitor connected to the light-emitting element 23 to be emitted that is connected to the light-emitting element 23 to be non-emitted and for which an abnormality has been detected, and generates the pulse signal SEL_C so as to prevent current from flowing to the cathode of the light-emitting element 23 to be non-emitted and for which an abnormality has been detected.

[0097] The charge control circuit 74 generates a control signal based on the anode selection signal SEL_A and the light-emission trigger signal TRG_O to control the gate of the PMOS transistor of the selection circuit connected to the corresponding anode wiring. More specifically, if no abnormality is detected, the control signal turns on the PMOS transistor of the selection circuit connected to the anode wiring to which the light-emitting element 23 to be emitted is connected during the period when the light-emission trigger signal TRG_O is low. As a result, during the period when the light-emission trigger signal TRG_O is low, current flows through the anode wiring to which the light-emitting element 23 to be emitted is connected, charging the capacitor on this anode wiring. On the other hand, if an abnormality is detected in a light-emitting element 23 not to be emitted, the control signal is forcibly set to low so that no current flows through the anode wiring to which the anode of the light-emitting element 23 to be emitted connected to this light-emitting element 23 is connected. As a result, charging of the capacitor on the anode wiring to which the anode of the light-emitting element 23 to be emitted connected to the abnormal light-emitting element 23 is connected is stopped.

[0098] Based on the cathode selection signal SEL_C and the light-emission trigger signal TRG_O, the driver control circuit 75 generates a control signal that controls the gate of the NMOS transistor of the drive circuit connected to the corresponding cathode wiring. More specifically, if no abnormality is detected, the driver control circuit 75 generates a control signal that turns on the NMOS transistor of the drive circuit connected to the cathode of the light-emitting element 23 to be emitted while the light-emission trigger signal TRG_O is at a high level. As a result, while the light-emission trigger signal TRG_O is at a high level, current from the capacitor flows between the anode and cathode of the light-emitting element 23 to be emitted, causing the light-emitting element 23 to emit light. On the other hand, if an abnormality is detected in a light-emitting element 23 that is not to be emitted, the control signal is forcibly set to a low level so that the NMOS transistor of the drive circuit E to which the cathode of the light-emitting element 23 to be emitted is connected is turned off. This stops the light-emission of the light-emitting element 23 to be emitted.

[0099] The pulse generation control circuit 73 supplies, for example, four anode selection signals SEL_A to the charge control circuit 74 in sequence. As a result, Anodes 1 to 3 in FIG. 2 and Anode 4 (not shown in FIG. 2) are selected in sequence, and the corresponding capacitors are charged except for the capacitor that has experienced a short-circuit abnormality. The pulse generation control circuit 73 also supplies four cathode selection signals SEL_C to the driver control circuit 75 in sequence. As a result, Cathodes 1 and 2 in FIG. 2 and Cathodes 3 and 4 (not shown in FIG. 2) are selected in sequence, and current is passed through the cathodes of the corresponding light-emitting elements except for the cathode of the light-emitting element that has experienced a short-circuit abnormality. As a result, the pulse generation control circuit 73 selects Anodes 1 to 4 and Cathodes 1 to 4 in sequence, causing the light-emitting elements 23 on the light-emitting element array to emit light in sequence.

[0100] The pulse generation control circuit 73 also inputs an error signal M_ERR to the master control circuit 72 to notify that a failure in the light emitting element 23 has been detected.

[0101] When the error signal M_ERR is input, the master control circuit 72 stops outputting the vertical synchronization signal VSYNC, the horizontal synchronization signal HSYNC, and the light emission trigger signal TRG_O.

[0102] 8 is a flowchart showing the light emitting operation of the light emitting device 1 according to the first embodiment. First, the pulse generation control circuit 73 identifies the light emitting element 23 to be emitted (e.g., the light emitting element 23a in FIG. 2) (step S1). Specifically, the pulse generation control circuit 73 determines the anode (first anode wiring 31) and cathode (cathode wiring 41) corresponding to the light emitting element 23a to be emitted, based on the light emission timing defined by the vertical synchronization signal VSYNC, the horizontal synchronization signal HSYNC, and the light emission trigger signal TRG_O.

[0103] Next, the selection circuit selects the light-emitting element 23 to be illuminated. More specifically, the charge control circuit 74 turns on a PMOS transistor (e.g., transistor 37a) in the selection circuit, thereby applying a voltage to the anode of the light-emitting element 23 (step S2). This charges a capacitor (e.g., first capacitor 34) connected to the anode of the light-emitting element 23 to be illuminated (step S3).

[0104] During charging of the capacitor, the fault detection circuit 50 detects the anode voltage of the light-emitting elements 23 that are not intended to emit light (e.g., light-emitting elements 23b and 23c) (step S4). The fault detection circuit 50 then compares the detected anode voltage with a threshold voltage Vth (step S5). Normally, no voltage is applied to the anodes of the light-emitting elements 23 that are not intended to emit light, so the anode voltage of the light-emitting elements 23 that are not intended to emit light has a voltage level lower than the threshold voltage Vth.

[0105] If, in step S5, the anode voltage detected by the fault detection circuit 50 is at a voltage level lower than the threshold voltage Vth, the fault detection circuit 50 determines that no fault has occurred in the light-emitting element 23. As a result, the drive circuit E drives the light-emitting element 23 (light-emitting element 23a) that is the target for light emission. More specifically, the driver control circuit 75 turns on a transistor (e.g., transistor 24a) in the drive circuit, connecting the cathode of the light-emitting element 23 that is the target for light emission to the ground wiring (GND) (step S6). As a result, current flows between the anode and cathode of the light-emitting element 23 that is the target for light emission, causing the light-emitting element 23 to begin emitting light (step S7).

[0106] After a predetermined time has elapsed since the light-emitting element 23 started emitting light, the transistors in the selection circuit that were turned on in step S2 and the transistors in the drive circuit that were turned on in step S6 are turned off, thereby causing the light-emitting element 23 to stop emitting light (step S8).

[0107] After the light-emitting element 23 has finished emitting light, the next light-emitting element 23 (e.g., light-emitting element 23b) to be emitted is identified again in step S1. The light-emitting device 1 causes the plurality of light-emitting elements 23 to emit light in turn by repeating steps S1 to S8 for each of the plurality of light-emitting elements 23 on the light-emitting element array.

[0108] If the anode voltage detected by the failure detection circuit 50 is at a voltage level higher than the threshold voltage Vth in step S5, the failure detection circuit 50 detects a failure in the light-emitting element 23. The failure includes a short circuit and a leakage current flowing from the cathode to the anode of the light-emitting element. This causes the failure detection control circuit 71 to send an error signal ERR to the pulse generation control circuit 73 (step S9). The error signal ERR is also called a failure flag.

[0109] The pulse generation control circuit 73, which has received the error signal ERR, stops outputting the anode selection signal SEL_A and the cathode selection signal SEL_C. This causes the driver control circuit 75 to stop driving by the drive circuit connected to the non-target light-emitting element for which the abnormality was detected. The charge control circuit 74 also stops selection by the selection circuit connected to the non-target light-emitting element 23 for which the abnormality was detected, and selection by the selection circuit connected to the target light-emitting element 23 for which the abnormality was detected is connected, which is connected to the drive circuit to which the non-target light-emitting element for which the abnormality was detected is connected. The charge control circuit 74 also discharges the capacitor corresponding to the selection circuit connected to the target light-emitting element 23 for which the abnormality was detected is connected to the drive circuit to which the non-target light-emitting element for which the abnormality was detected is connected (step S10).

[0110] Specifically, if the second fault detection circuit 52 of FIG. 3C detects an abnormality in the non-target light-emitting element 23b in step S9, the driver control circuit 75 turns off the transistor 24a in the drive circuit Ea to which the light-emitting element 23b is connected, thereby stopping its drive. The charge control circuit 74 stops the selection of the second selection circuit 38 connected to the light-emitting element 23b by not turning on the transistor 38a. The charge control circuit 74 also stops the selection of the first selection circuit 37 connected to the drive circuit Ea to which the light-emitting element 23b is connected, by turning off the transistor 37a and turning on the transistor 37b. With the transistor 37b turned on, the first capacitor 34 corresponding to the first selection circuit 37 discharges the charge stored in step S3 to the ground wiring GND.

[0111] The pulse generation control circuit 73 stops the emission of the failed light-emitting element 23 by causing the vertical synchronization signal generation circuit 76, horizontal synchronization signal generation circuit 77, and light-emitting control signal generation circuit 78 in the master control circuit 72 to stop generating the vertical synchronization signal VSYNC, horizontal synchronization signal HSYNC, and light-emitting trigger signal TRG_O, respectively (step S11).

[0112] 8, the failure detection circuit 50 can detect an abnormality in a non-target light-emitting element 23 (step S5) before the light-emitting element 23 emits light (step S7). As a result, when a light-emitting element 23 fails, the light-emitting operation of the light-emitting device 1 can be stopped before the effects of the failure become apparent (steps S9 to S11).

[0113] FIG. 9 is a timing chart of each signal during the light-emitting operation of the light-emitting device 1 according to the first embodiment. For simplicity's sake, FIG. 9 shows an example in which current alternately flows through the first anode wiring 31 (Anode 1) and the second anode wiring 32 (Anode 2). A plurality of light-emitting elements 23 are connected to each of Anode 1 and Anode 2, and current is supplied to the anodes of these light-emitting elements 23 in turn. The time charts in FIG. 9 and elsewhere also show an example in which a VCSEL (Vertical Cavity Surface Emitting Laser) is used, in which a plurality of light-emitting elements 23 are arranged two-dimensionally. In this case, the plurality of light-emitting elements 23 are also called surface-emitting laser elements.

[0114] First, at time t1, the master control circuit 72 sets the vertical synchronization signal VSYNC to a high level. The vertical synchronization signal VSYNC is a signal that indicates the scanning timing of the light-emitting element array. Synchronization between the output timing of the vertical synchronization signal VSYNC and the scanning timing of the light-emitting element array is also called frame synchronization.

[0115] Subsequently, at time t2, the master control circuit 72 sets the horizontal synchronization signal HSYNC to a high level. The horizontal synchronization signal HSYNC is a signal that indicates the timing for switching the anode wiring to be scanned. Multiple light-emitting elements 23 connected to the same anode wiring are collectively called a slot. Multiple slots in the light-emitting element array are selected in turn in synchronization with the output timing of the horizontal synchronization signal HSYNC. This synchronization is also called slot synchronization.

[0116] At time t2, the pulse generation control circuit 73 selects, for example, Anode1 and Cathode1 using the selection signals SEL_A and SEL_C. As a result, a voltage is applied to Anode1 from the power supply line VDD, and the voltage of Anode1 begins to rise. The voltage of Anode1 rises to, for example, the voltage level of the reference voltage LDVDD. At this time, the first capacitor 34 connected to Anode1 is charged.

[0117] At time t3, the master control circuit 72 sets the light emission trigger signal TRG_O to a high level. The light emission trigger signal TRG_O is a signal that indicates the light emission timing of the light emitting element 23. As a result, Cathode 1 is connected to the ground wiring GND. The light emitting element 23 connected to Anode 1 and Cathode 1 is driven to emit light, and the voltage level of Anode 1 drops. Note that in timing charts such as FIG. 9, the connection position of the light emitting element 23 to be emitted is represented as light emission coordinates (1, 1).

[0118] Between times t2 and t3, the fault detection circuit 50 monitors Anodes 2 to N other than Anode 1, and confirms that the anode voltage does not exceed a predetermined threshold voltage Vth.

[0119] At time t4, the master control circuit 72 sets the light emission trigger signal TRG_O to low level. This disconnects Cathode 1 from the ground wiring GND, causing the light emission of the light-emitting element 23a to end, and the voltage of Anode 1 begins to rise again to the voltage level of the reference voltage LDVDD. Also, at time t4, the pulse generation control circuit 73 selects the next cathode (e.g., Cathode 2) using SEL_C. The pulse generation control circuit 73 may select the next cathode in synchronization with the timing at which the light emission trigger signal TRG_O goes low level, or may select the next cathode at any timing between the end of light emission of the light-emitting element 23 and the time at which the next light-emitting element 23 is made to emit light.

[0120] At time t5, the light-emission trigger signal TRG_O goes high. As at time t3, Cathode 2 is connected to the ground wiring GND, the light-emitting element 23 at the light-emission coordinates (2, 1) emits light, and the voltage level of Anode 1 drops. At time t6, the light-emission trigger signal TRG_O goes low. As a result, as at time t4, Cathode 2 is disconnected from the ground wiring GND, the light emission of the light-emitting element 23 ends, and the voltage of Anode 1 begins to rise again to the voltage level of the reference voltage LDVDD. Furthermore, Cathode 3 is selected by the selection signal SEL_C. Similarly, at times t7 to t8, the light-emitting element 23 at the light-emission coordinates (3, 1) corresponding to Anode 1 and Cathode 3 emits light. Note that FIG. 9 omits the light-emission operation from Cathode 4 onwards.

[0121] At time t9, the horizontal synchronization signal HSYNC goes low. This connects Anode1 to the ground line GND, causing the voltage of Anode1 to drop to, for example, the ground voltage level. Also, the charge in the first capacitor 34 is discharged to the ground line GND.

[0122] Subsequently, at time t10, the horizontal synchronization signal HSYNC goes high. As a result, the next anode (e.g., Anode2) is selected by the selection signal SEL_A. Also, the cathode to be driven first (e.g., Cathode1) is selected. As a result, a voltage is applied to Anode2 from the power supply line VDD, and the voltage of Anode2 begins to rise. Also, the second capacitor 35 connected to Anode2 is charged.

[0123] At time t11, the light emission trigger signal TRG_O goes high. This connects Cathode 1 to the ground line GND, causing the light emitting element 23 at the light emitting coordinates (1, 2) connected to Anode 2 and Cathode 1 to emit light, and the voltage level of Anode 2 drops. From time t10 to t11, the fault detection circuit 50 monitors the anode voltages other than Anode 2.

[0124] At time t12, the light emission trigger signal TRG_O goes low. This disconnects Cathode 1 from the ground line GND, causing the light emission of the light emitting element 23 to cease. At time t12, the voltage of Anode 2 begins to rise again to the voltage level of the reference voltage LDVDD. Also, at time t12, the next cathode (for example, Cathode 2) is selected.

[0125] Similarly, from time t13 to t14, the light-emitting element 23 at the light-emitting coordinate (2, 2) emits light. Furthermore, from time t15 to t16, the light-emitting element 23 at the light-emitting coordinate (2, 3) emits light. At time t17, the horizontal synchronization signal HSYNC goes low, connecting Anode2 to the ground wiring GND and causing the voltage of Anode2 to drop to, for example, the ground voltage level. Furthermore, the charge in the second capacitor 35 is discharged to the ground wiring GND.

[0126] At time t18, the master control circuit 72 sets the vertical synchronization signal VSYNC to low level. The light-emitting operation from when the vertical synchronization signal VSYNC goes high until when it goes low level (i.e., from time t1 to t18) is also called the light-emitting operation for one frame. Note that the light-emitting operation from Anode 3 onwards is not shown in FIG. 9.

[0127] At time t19, the master control circuit 72 sets the vertical synchronization signal VSYNC to high level, and starts the light emitting operation for the next frame. Thereafter, similar to the light emitting operation for one frame from time t1 to t18, the horizontal synchronization signal HSYNC goes to high level at time t20. At times t21 to t22, times t23 to t24, and times t25 to t26, the light emitting elements 23 at light emitting coordinates (1,1), (2,1), and (3,1) respectively perform light emitting operations. At time t27, the horizontal synchronization signal HSYNC goes to low level.

[0128] 10 is a timing chart of each signal when a failure occurs in the light-emitting element 23 of the light-emitting device 1 according to the first embodiment. At time t31, the vertical synchronization signal VSYNC goes high, and at time t32, the horizontal synchronization signal HSYNC goes high. At time t32, as at time t2, Anode1 and Cathode1 are selected, and a voltage is applied to Anode1 from the power supply wiring VDD. However, in FIG. 10, due to a short-circuit failure in the light-emitting element 23 as described in FIG. 3C, a voltage is also applied to Anode2.

[0129] 10 shows an example in which the light-emitting element 23 is completely short-circuited at time t33. In this case, a voltage similar to that applied to the Anode 1 side is applied to the Anode 2 side. The fault detection circuit 50 monitors the voltage of the unselected Anode 2 and detects that the voltage of Anode 2 is equal to or higher than the threshold voltage Vth. As a result, at time t33, the fault detection circuit 50 sets the error signal ERR to a high level.

[0130] The pulse generation control circuit 73 stops outputting the selection signals SEL_A and SEL_C in response to the error signal ERR. As a result, Anode1 and Anode2 are connected to the ground wiring GND, and the voltages of Anode1 and Anode2 drop to the ground voltage level. In addition, the master control circuit 72 sets the vertical synchronization signal VSYNC and the horizontal synchronization signal HSYNC to low level at time t34. As a result, the light emitting device 1 stops emitting light.

[0131] If a short circuit occurs in the light-emitting element 23, the voltage applied to the Anode 1 side also drops due to voltage division. For example, FIG. 10 shows an example in which the voltage applied to Anode 1 is approximately half the desired voltage (reference voltage LDVDD). The light-emitting device 1 may monitor the anode voltage of the light-emitting element 23 on the light-emitting target side to detect an abnormality in which the anode voltage does not reach a predetermined voltage level. Also, a fault detection circuit may be provided that monitors the anode voltage of the light-emitting element 23 on the light-emitting target side.

[0132] 11 is a timing chart showing a case where an abnormality is detected before the light-emitting element 23 fails. At time t41, the vertical synchronization signal VSYNC goes high, and at time t42, the horizontal synchronization signal HSYNC goes high, and Anode1 and Cathode1 are selected, and a voltage is applied to Anode1 from the power supply wiring VDD. In FIG. 11, the light-emitting element 23 has begun to fail, and a small voltage is also applied to Anode2.

[0133] From time t43 to t44, the light-emitting element 23 at the light-emitting coordinates (1, 1) emits light. From time t44 to t45, voltage is again applied to Anode1, but the failure in the light-emitting element 23 progresses, and a voltage level equal to or greater than the threshold voltage Vth is also applied to Anode2. At time t45, the failure detection circuit 50 detects an abnormality in Anode2 and sets the error signal ERR to high level. At time t46, the vertical synchronization signal VSYNC and horizontal synchronization signal HSYNC go low level, and the light-emitting device 1 stops emitting light.

[0134] 11, an abnormality is detected at a stage before the light-emitting element 23 fails, and the light-emitting operation of the light-emitting device 1 is stopped. The threshold generation circuit 62 in FIG. 4A adjusts the voltage division ratio with respect to the reference voltage LDVDD to generate a threshold voltage Vth with higher resolution, thereby enabling earlier detection of an abnormality in Anode 2.

[0135] The light emitting device 1 according to the first embodiment has, for example, a VCSEL structure. Fig. 12 is a cross-sectional view showing an example of the cross-sectional structure of the light emitting device 1 having the VCSEL structure. The light emitting device 1 in Fig. 12 is configured, for example, by stacking an LD (Laser Diode) chip 46 on an LDD substrate 45. The LD chip 46 includes a substrate 21, a stacked film 22, a plurality of light emitting elements 23 formed using the stacked film 22, a plurality of anode electrodes 47, and a cathode electrode 48.

[0136] The substrate 21 of the LD chip 46 is made of a compound semiconductor such as GaAs (gallium arsenide). The surface of the substrate 21 facing the LDD substrate 45 is the front surface S2, and laser light is emitted from the back surface S3 of the substrate 21. The stacked film 22 includes a first multilayer reflector, a first spacer layer, an active layer, a second spacer layer, and a second multilayer reflector. The laser light generated in the active layer is resonated between the first and second multilayer reflectors to increase the light intensity and is emitted from the back surface S3 of the substrate. Thus, the LD chip 46 of FIG. 12 is a back-illuminated type. In this specification, a light-emitting element 23 having the layer structure shown in FIG. 12 is referred to as a VCSEL structure.

[0137] The plurality of light-emitting elements 23 have a mesa structure formed by processing the laminated film 22 into a mesa shape. As viewed from the substrate 21 side, an anode electrode (second pad) 47 is disposed on the upper surface of each light-emitting element 23. Similarly, as viewed from the substrate 21 side, a cathode electrode 48 is disposed on the upper and side surfaces of the laminated film 22 disposed on the end side of the LD chip 46. As viewed from the substrate 21 side, a cathode electrode 48 is also disposed on the lowermost layer of the laminated film 22 of the plurality of light-emitting elements 23. In FIG. 12 , the anode electrode 47 and the cathode electrode 48 may be reversed. While the common electrode in FIG. 12 is the cathode electrode 48, the common electrode may be the anode electrode 47, and a cathode electrode 48 may be provided on each mesa portion 20.

[0138] The LDD substrate 45 has a plurality of pads 49 for supplying drive signals to the plurality of light emitting elements 23 of the LD chip 46. The pads 49 are arranged along a surface S1 of the LDD substrate 45 that faces the LD chip 46. A bonding layer 49a is arranged on these pads 49, and the pads 49 of the LDD substrate 45 and the pads of the corresponding anode electrodes 47 of the LD chip 46 are bonded to each other via the bonding layer 49a.

[0139] The LDD substrate 45 may have a drive circuit that generates a drive signal. In this case, the LDD substrate 45 performs active driving. Alternatively, the LDD substrate 45 may supply a voltage corresponding to a drive signal generated by an external drive circuit to the pad 49. In this case, the LDD substrate 45 performs passive driving.

[0140] The substrate 21 is, for example, a compound semiconductor substrate such as a GaAs (gallium arsenide) substrate. Fig. 12 shows a front surface S2 of the substrate 21 facing the -Z direction and a back surface S3 of the substrate 21 facing the +Z direction. The front surface S1 and back surface S2 shown in Fig. 12 are perpendicular to the Z direction. In Fig. 12, the front surface S2 is the lower surface of the substrate 21, and the back surface S3 is the upper surface of the substrate 21.

[0141] 12, each light-emitting element 23 is provided between an anode electrode (anode wiring 31 to 33) 47 and a cathode electrode 48. When a current flows between the anode electrode 47 and the cathode electrode 48, each light-emitting element 23 emits light.

[0142] In this way, the light-emitting device 1 according to the first embodiment can detect an abnormality in the light-emitting element 23 before the light-emitting element 23 actually emits light. This eliminates the risk of the light-emitting device 1 emitting light at an emission brightness that exceeds the safety standards for laser light, improving safety from the perspective of eye safety. Furthermore, the light-emitting device 1 can detect an abnormality before the light-emitting element 23 is completely short-circuited by adjusting the voltage Vth generated by the threshold generation circuit 62. This allows the light-emitting element 23 related to the abnormality to be forcibly stopped from emitting light, while the other light-emitting elements 23 can continue to emit light, thereby enabling the light-emitting device 1 to be used effectively.

[0143] Second Embodiment Various modifications are possible for the configuration of the fault detection circuit 50. A fault detection circuit 50 according to the second embodiment is provided for each of two or more anode wirings. For example, the fault detection circuit 50 may be configured with an analog-to-digital converter. FIG. 13 is a block diagram showing the configuration of a fault detection circuit 50b according to the second embodiment. The fault detection circuit 50b includes multiple analog-to-digital converters that convert the voltages of the multiple anode wirings into digital signals. FIG. 13 and FIG. 14, which will be described later, show an example in which a light-emitting device includes multiple light-emitting element groups connected to first to fourth anode wirings. In FIGS. 13 and 14, the first anode wiring is referred to as Anode1, the second anode wiring as Anode2, the third anode wiring as Anode3, and the fourth anode wiring as Anode4. The fault detection circuit 50b in FIG. 13 has analog-to-digital converters (ADCs) 81, 82, 83, and 84 connected to Anode1, Anode2, Anode3, and Anode4, respectively.

[0144] In parallel with the period during which the plurality of light-emitting elements 23 are performing light-emitting operations, the ADCs 81 to 84 perform analog-to-digital conversion of the voltages of Anode1 to Anode4, respectively, to generate digital signals ADOUT1 to ADOUT4. These four digital signals ADOUT1 to ADOUT4 are combined, for example, by a wired OR to generate an abnormality detection signal ADOUT_ERR. This abnormality detection signal ADOUT_ERR is input to the fault detection control circuit 71. The process of combining the four digital signals ADOUT1 to ADOUT4 by a wired OR or the like to generate the abnormality detection signal ADOUT_ERR corresponds to the abnormality detection signal generation unit N.

[0145] Each of the ADCs 81 to 84 is configured similarly to, for example, Fig. 4A or 4B. That is, before the light-emitting element to be emitted starts emitting light, each of the analog-to-digital converters 81 to 84 compares the voltage level of each of the anode wirings Anode1 to Anode4 with a predetermined threshold value, and generates digital signals ADOUT1 to ADOUT4 indicating the comparison results.

[0146] An abnormality detection signal ADOUT_ERR obtained by combining digital signals ADOUT1 to ADOUT4 output from the plurality of ADCs 81 to 84 is input to the failure detection control circuit 71. The failure detection control circuit 71 generates an error signal ERR based on the abnormality detection signal ADOUT_ERR.

[0147] As described above, the fault detection circuit 50b according to the second embodiment provides an ADC for each anode wiring to perform abnormality detection, thereby enabling early detection of an abnormality in a non-target light-emitting element 23 connected to any of the anode wirings. The abnormality detection signal ADOUT_ERR is generated by combining, for example, a wired OR, multiple digital signals output from multiple ADCs corresponding to multiple anode wirings. The abnormality detection signal ADOUT_ERR is generated before the target light-emitting element 23 starts emitting light, preventing the light from emitting light at a brightness exceeding the laser light safety standard. This allows for the realization of a light-emitting device with excellent safety from an eye-safe perspective.

[0148] Third Embodiment In the second embodiment, multiple ADCs 81 to 84 are provided for each anode wiring, resulting in a larger circuit scale. In the third embodiment, a single ADC is used to detect abnormalities in multiple anode wirings. FIG. 14 is a block diagram showing the configuration of a fault detection circuit 50c according to the third embodiment. The fault detection circuit 50c includes an ADC 91 and a switch 92.

[0149] The switch 92 selects a plurality of anode wirings (Anode1 to Anode4 in FIG. 14). The ADC 91 converts the voltage of the anode wiring selected by the switch 92 into a digital signal. The fault detection circuit 50c generates an abnormality detection signal ADOUT_ERR based on the digital signal and inputs it to the fault detection control circuit 71. The ADC 91 is configured similarly to, for example, FIG. 4A or 4B, and compares the voltage of the anode wiring with a predetermined threshold value and outputs a digital signal indicating the comparison result as the abnormality detection signal ADOUT_ERR.

[0150] The switch 92 selects a plurality of anode wirings in turn. For example, when the light-emitting element 23 connected to Anode 1 is performing a light-emitting operation, the switch 92 selects Anode 2 to Anode 4 in turn. For example, during the charging period of the first capacitor 34 (for example, from time t2 to t3 in FIG. 9 ), the switch 92 selects Anode 2 to Anode 4 in turn during the period from time t2 to t3 so that the voltages of all the anode wirings other than Anode 1 connected to the first capacitor 34 can be detected.

[0151] In this way, the fault detection circuit 50c according to the third embodiment detects abnormalities in multiple anode wirings using a single ADC, thereby reducing the circuit size and power consumption. By providing a switch to quickly switch the multiple anode wirings in turn and connect them to the ADC, it is possible to detect abnormalities while minimizing the time delay after an abnormality occurs.

[0152] (Configuration of distance measuring device) The light emitting device 1 according to this embodiment can be used, for example, in a distance measuring device (also called a distance measuring module) 100 that measures the distance to an object in a non-contact manner. The distance measuring device 100 requires a light receiving device that receives the reflected light signal from the light emitting device 1, which is reflected by the object. The light emitting device 1 and the light receiving device may be arranged separately, or may be arranged on a common support member.

[0153] Fig. 15 is a cross-sectional view of a light emitting device 1a. The light emitting device 1a in Fig. 15 includes an LD (Laser Diode) chip 11 including the above-mentioned light emitting unit 2, an LDD (Laser Diode Driver) substrate 12 including the above-mentioned drive unit 3, a mounting substrate 13, a heat dissipation substrate 14, a correcting lens holder 15, one or more correcting lenses 16, and wiring 17. The LD chip 11 is also called a VCSEL substrate.

[0154] 15 shows X-axis, Y-axis, and Z-axis that are perpendicular to each other. The +Z direction corresponds to the upward direction, and the −Z direction corresponds to the downward direction. Note that the −Z direction may or may not strictly coincide with the direction of gravity.

[0155] The LD chip 11 is disposed on a mounting substrate 13 via a heat dissipation substrate 14, and the LDD substrate 12 is also disposed on the mounting substrate 13. The mounting substrate 13 is, for example, a printed circuit board. A light receiving unit and a signal processing unit may also be disposed on the mounting substrate 13. The heat dissipation substrate 14 is, for example, a ceramic substrate such as an aluminum oxide substrate or an aluminum nitride substrate.

[0156] The correction lens holding portion 15 is disposed on the heat dissipation substrate 14 so as to surround the LD chip 11, and holds one or more correction lenses 16 above the LD chip 11. These correction lenses 16 are included in the light-emitting side optical system 5 described above. Light emitted from the light-emitting portion 2 in the LD chip 11 is corrected by these correction lenses 16 and then irradiated onto the subject S described above. Figure 15 shows, as an example, two correction lenses 16 held by the correction lens holding portion 15.

[0157] The wiring 17 is provided on the front, back, or inside of the mounting substrate 13, and electrically connects the LD chip 11 and the LDD substrate 12. The wiring 17 is, for example, a printed wiring provided on the front or back of the mounting substrate 13, or a via wiring that penetrates the mounting substrate 13. In this embodiment, the wiring 17 also passes through the inside or near the heat dissipation substrate 14.

[0158] FIG. 16 is a block diagram showing an example of the configuration of a distance measuring device 100 as an example of implementation of the light emitting device 1 according to this embodiment.

[0159] As shown in the figure, the distance measuring device 100 includes an emitting unit 101, a driving unit 102, a power supply circuit 103, an emitting side optical system 104, a receiving side optical system 105, a light receiving unit 106, a signal processing unit 107, a control unit 108, and a temperature detection unit 109.

[0160] The light-emitting unit 101 emits light from a plurality of light sources. The light-emitting unit 101 and the light-emitting side optical system 104 correspond to the above-described light-emitting device 1. As will be described later, the light-emitting unit 101 of this example has light-emitting elements 23 using VCSELs as light sources, and these light-emitting elements 23 are arranged in a predetermined pattern, for example, in a matrix.

[0161] The driving unit 102 is configured to have a power supply circuit 103 for driving the light emitting unit 101. The power supply circuit 103 generates a power supply voltage (a driving voltage Vd, which will be described later) for the driving unit 102 based on an input voltage (an input voltage Vin, which will be described later) from, for example, a battery (not shown) or the like provided in the distance measuring device 100. The driving unit 102 drives the light emitting unit 101 based on the power supply voltage.

[0162] Light emitted from the light-emitting unit 101 is irradiated onto a subject (object) S, which is the object of distance measurement, via a light-emitting side optical system 104. The light thus irradiated is reflected from the subject S and enters the light-receiving surface of the light-receiving unit 106 via a light-receiving side optical system 105.

[0163] The light receiving unit 106 is a light receiving element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and receives reflected light from the subject S that enters through the light receiving side optical system 105 as described above, converts it into an electrical signal, and outputs it.

[0164] The light receiving unit 106 performs processes such as CDS (Correlated Double Sampling) and AGC (Automatic Gain Control) on the electrical signal obtained by photoelectrically converting the received light, and then performs A / D (Analog / Digital) conversion on the electrical signal, and outputs the resulting digital data to the signal processing unit 107 at the subsequent stage.

[0165] Furthermore, the light receiving unit 106 in this example outputs a frame synchronization signal Fs to the driving unit 102. This enables the driving unit 102 to cause the light emitting element 23 in the light emitting unit 101 to emit light at a timing according to the frame period of the light receiving unit 106.

[0166] The signal processing unit 107 is configured as a signal processor, for example, a DSP (Digital Signal Processor), etc. The signal processing unit 107 performs various signal processes on the digital signal input from the light receiving unit 106.

[0167] The control unit 108 is configured with, for example, a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., or an information processing device such as a DSP, and controls the drive unit 102 for controlling the light-emitting operation by the light-emitting unit 101, and controls the light-receiving operation by the light-receiving unit 106.

[0168] The control unit 108 has a function as a distance measuring unit 108a. The distance measuring unit 108a detects the distance to the subject S based on a signal input via the signal processing unit 107 (i.e., a signal obtained by receiving reflected light from the subject S). The distance measuring unit 108a in this example detects the distance to each part of the subject S in order to be able to identify the three-dimensional shape of the subject S.

[0169] A specific distance measurement method used by the distance measuring device 100 will be described later.

[0170] The temperature detection unit 109 detects the temperature of the light emitting unit 101. The temperature detection unit 109 may be configured to detect temperature using, for example, a diode.

[0171] In this example, information about the temperature detected by the temperature detection unit 109 is supplied to the drive unit 102, which enables the drive unit 102 to drive the light emitting unit 101 based on the temperature information.

[0172] (Range Measurement Method) The distance measurement method used in the distance measurement device 100 may be, for example, a STL (Structured Light) method or a ToF (Time of Flight) method.

[0173] The STL method is a method for detecting distance based on an image of a subject S illuminated with light having a predetermined light / dark pattern, such as a dot pattern or a grid pattern.

[0174] Fig. 17A is an explanatory diagram of the STL method. In the STL method, pattern light Lp having a dot pattern such as that shown in Fig. 17A is irradiated onto a subject S. The pattern light Lp is divided into a plurality of blocks BL, and a different dot pattern is assigned to each block BL (dot patterns are arranged not to overlap between blocks BL).

[0175] FIG. 17B is an explanatory diagram of the distance measurement principle of the STL system.

[0176] In this example, a wall W and a box BX placed in front of it are treated as the subject S, and pattern light Lp is irradiated onto the subject S. "G" in the figure schematically represents the angle of view of the light receiving unit 106.

[0177] In addition, "BLn" in the drawing denotes light of a certain block BL in the pattern light Lp, and "dn" denotes the dot pattern of the block BLn projected on the light-receiving image by the light-receiving unit 106.

[0178] Here, if there is no box BX in front of the wall W, the dot pattern of the block BLn is projected at the position "dn'" in the figure in the received light image. In other words, the position at which the pattern of the block BLn is projected in the received light image differs depending on whether the box BX is present or not, and specifically, the pattern is distorted.

[0179] The STL method utilizes the fact that the irradiated pattern is distorted by the object shape of the subject S to determine the shape and depth of the subject S. Specifically, this method determines the shape and depth of the subject S from the way the pattern is distorted.

[0180] When the STL system is adopted, for example, a global shutter type IR (Infrared) light receiving unit is used as the light receiving unit 106. In the case of the STL system, the distance measuring unit 108a controls the drive unit 102 so that the light emitting unit 101 emits pattern light, detects distortion of the pattern in the image signal obtained via the signal processing unit 107, and calculates the distance based on the distortion of the pattern.

[0181] Next, the ToF method is a method for detecting the distance to an object by detecting the time of flight (time difference) of light emitted from the light-emitting unit 101, reflected by the object, and reaching the light-receiving unit 106.

[0182] When a so-called direct ToF (dTOF) method is adopted as the ToF method, a SPAD (Single Photon Avalanche Diode) is used as the light receiving unit 106, and the light emitting unit 101 is pulse-driven. In this case, the distance measuring unit 108a calculates the time difference between light emission and reception of light emitted from the light emitting unit 101 and received by the light receiving unit 106, based on a signal input via the signal processing unit 107, and calculates the distance to each part of the subject S based on the time difference and the speed of light.

[0183] When the so-called indirect ToF (iTOF) method (phase difference method) is adopted as the ToF method, a light receiving unit capable of receiving, for example, IR light is used as the light receiving unit 106 .

[0184] (Application Example to a 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 as a device mounted on any type of mobile body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0185] FIG. 18 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0186] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 18, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (interface) 12053.

[0187] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0188] The body system control unit 12020 controls the operation of various devices equipped in 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 headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0189] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0190] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0191] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0192] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the inter-vehicle distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane departure warning, etc.

[0193] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0194] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0195] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying the passengers of the vehicle or the outside of the vehicle of information. In the example of Fig. 18, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0196] FIG. 19 is a diagram showing an example of the installation position of the imaging unit 12031.

[0197] In FIG. 19, a vehicle 12100 has imaging units 12101, 12102, 12103, 12104, and 12105 as the imaging unit 12031.

[0198] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The forward images acquired by the imaging units 12101 and 12105 are mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0199] 19 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0200] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0201] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which runs autonomously without relying on driver operation.

[0202] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0203] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0204] The above describes an example of a vehicle control system to which the technology according to the present disclosure can be applied. The technology according to the present disclosure can be applied to, for example, the image capturing unit 12031 among the components described above. Specifically, the light emitting device 1 according to the present disclosure can be provided together with the image capturing unit 12031. By applying the technology according to the present disclosure to the image capturing unit 12031, it is possible to improve the resolution of distance images while suppressing the generation of electromagnetic noise, thereby enhancing the functionality and safety of the vehicle 12100.

[0205] The present technology can be configured as follows: (1) A plurality of light-emitting elements arranged in a two-dimensional array, each having a first and second terminal; N first wirings (N is an integer of 2 or more) extending in a first direction, and N second wirings extending in a second direction intersecting the first direction and electrically connected to the N first wirings, respectively; a plurality of first terminal wirings electrically connected to the first terminals of the light-emitting elements; a plurality of second terminal wirings electrically connected to the second terminals of the light-emitting elements, each electrically connected to N of the light-emitting elements; a plurality of selection circuits electrically connected to one of the plurality of first terminal wirings and the plurality of second terminal wirings, and selecting the light-emitting elements to be light-emitting; a plurality of drive circuits electrically connected to the other of the plurality of first terminal wirings and the plurality of second terminal wirings, and driving the plurality of light-emitting elements; and a plurality of capacitors electrically connected to one of the plurality of first terminal wirings and the plurality of second terminal wirings, and storing electric charges to be supplied to the plurality of light-emitting elements. a light-emitting device comprising: at least one fault detection circuit electrically connected to one of the plurality of first terminal wirings and the plurality of second terminal wirings, and detecting an abnormality in a light-emitting element that is not a target for light emission. (2) The light-emitting device according to (1), wherein the fault detection circuit detects the abnormality in which the first terminal and the second terminal of the light-emitting element that is not a target for light emission are short-circuited. (3) The light-emitting device according to (1) or (2), wherein the fault detection circuit detects an abnormality in which at least a part of the current flowing through the light-emitting element that is a target for light emission is caused by a leakage current flowing through the light-emitting element that is not a target for light emission. (4) The light-emitting device according to any one of (1) to (3), wherein the fault detection circuit detects the abnormality before the corresponding drive circuit drives the light-emitting element that is a target for light emission. (5) The light-emitting device according to any one of (1) to (4), wherein the fault detection circuit is arranged for each of the plurality of first terminal wirings or the plurality of second terminal wirings. (6) The light emitting device according to (5), wherein each of the plurality of fault detection circuits has a comparator that outputs an abnormality detection signal when the voltage of the corresponding first terminal wiring or the corresponding second terminal wiring is equal to or higher than a predetermined threshold voltage.(7) The light-emitting device according to (6), further comprising a threshold generation circuit that generates the threshold voltage based on a reference voltage having a voltage level higher than the threshold voltage. (8) The light-emitting device according to (7), wherein the threshold generation circuit has a variable impedance element that is capable of adjusting a voltage division ratio of the reference voltage, and generates the threshold voltage by dividing the reference voltage at the voltage division ratio adjusted by the variable impedance element. (9) The light-emitting device according to (8), wherein the variable impedance element includes a variable resistor. (10) The light-emitting device according to any one of (1) to (4), wherein the fault detection circuit is disposed for each of two or more of the first terminal wirings or the second terminal wirings. (11) The light-emitting device according to (10), wherein the fault detection circuit has: a plurality of analog-to-digital converters that convert voltages of the plurality of first terminal wirings or the plurality of second terminal wirings into digital signals, respectively; and an abnormality detection signal generation unit that generates an abnormality detection signal based on the plurality of digital signals output from the plurality of analog-to-digital converters. (12) The light-emitting device according to (11), wherein the plurality of analog-to-digital converters generate the digital signals in parallel while the plurality of light-emitting elements are performing light-emitting operations, and the fault detection circuit generates the abnormality detection signal indicating that at least one of the light-emitting elements that is not a target for emitting light has developed an abnormality. (13) The light-emitting device according to (10), wherein the fault detection circuit has: a switch that selects one of the plurality of first terminal wirings or the plurality of second terminal wirings; and an analog-to-digital converter that performs analog-to-digital conversion on the voltage of the first terminal wiring or the second terminal wiring selected by the switch to generate an abnormality detection signal. (14) The light-emitting device according to (13), wherein the switch selects the plurality of first terminal wirings or the plurality of second terminal wirings in sequence, and the fault detection circuit generates the abnormality detection signal for the light-emitting element that is not a target for emitting light connected to the plurality of first terminal wirings or the plurality of second terminal wirings selected in sequence by the switch.(15) The light emitting device according to any one of (1) to (14), further comprising a failure control circuit that stops selection by the selection circuit connected to at least one of a light emitting element that is not an object to emit light and that is connected to the first terminal wiring or the second terminal wiring in which the abnormality has been detected and a light emitting element that is an object to emit light and that is connected to the light emitting element, and stops driving of the drive circuit. (16) The light emitting device according to (15), further comprising a pulse generator that generates a pulse signal indicating that the abnormality has been detected, and the selection circuit connected to the light emitting element that is an object to emit light and that is connected to the first terminal wiring or the second terminal wiring in which the abnormality has been detected via a light emitting element that is not an object to emit light discharges the corresponding capacitor based on the pulse signal. (17) The light emitting device according to (15) or (16), comprising: a first synchronization signal generator that generates a first synchronization signal that defines the timing of causing the plurality of light emitting elements arranged in a two-dimensional array to emit light in sequence; and a second synchronization signal generator that generates a second synchronization signal that defines the timing of causing two or more of the light emitting elements arranged in the first direction to emit light in sequence, wherein the failure control circuit, when detecting the abnormality, causes the first synchronization signal generator to stop generating the first synchronization signal and causes the second synchronization signal generator to stop generating the second synchronization signal. (18) The light emitting device according to any one of (1) to (17), wherein the plurality of light emitting elements are surface emitting laser elements. (19) The light emitting device according to (18), wherein the plurality of light emitting elements are VCSELs (Vertical Cavity Surface Emitting Lasers).(20) A light emitting device comprising: a light emitting unit that emits light toward a subject; a light receiving unit that receives light that is reflected by the subject; and a distance measuring unit that detects a distance to the subject based on the light emitted by the light emitting unit and the light received by the light receiving unit, wherein the light emitting unit includes: a plurality of light emitting elements arranged in a two-dimensional array, each having a first and a second terminal; N first wirings (N is an integer of 2 or more) extending in a first direction; and N second wirings that extend in a second direction intersecting the first direction and are electrically connected to the N first wirings, respectively; a plurality of first terminal wirings that are electrically connected to the first terminals of the light emitting elements; a plurality of second terminal wirings that are electrically connected to the second terminals of the light emitting elements and each are electrically connected to N of the light emitting elements; a plurality of selection circuits that are electrically connected to one of the first and second terminal wirings and select the light emitting elements to be emitted; and a plurality of drive circuits that are electrically connected to the other of the first and second terminal wirings and drive the plurality of light emitting elements. a plurality of capacitors electrically connected to one of the first and second terminal wirings for storing electric charges to be supplied to the plurality of light-emitting elements; and a fault detection circuit electrically connected to one of the first and second terminal wirings for detecting an abnormality in which the anode and cathode of a light-emitting element that is not to emit light are short-circuited.

[0206] The aspects of the present disclosure are not limited to the individual embodiments described above, but include various modifications that may be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present disclosure, which is derived from the contents defined in the claims and their equivalents.

[0207] REFERENCE SIGNS LIST 1, 1a light emitting device, 2 light emitting section, 3 driving section, 5 light emitting side optical system, 11 LD chip, 12 LDD substrate, 13 mounting substrate, 14 heat dissipation substrate, 15 correction lens holding section, 16 correction lens, 17 wiring, 20 mesa section, 21 substrate, 22 laminated film, 23, 23a, 23b, 23c, 23d, 23e, 23f light emitting element, 24, 24a, 24b, 37a, 37b, 38a, 38b, 39a, 39b transistor, 31 first anode wiring, 31a first horizontal wiring, 31b first vertical wiring, 32 second anode wiring, 32a second horizontal wiring, 32b second vertical wiring, 33 third anode wiring, 33a third horizontal wiring, 33b third vertical wiring, 34 first capacitor, 35 second capacitor, 36 Third capacitor, 37 First selection circuit, 38 Second selection circuit, 39 Third selection circuit, 41 Cathode wiring, 42 Gate wiring, 45 LDD substrate, 46 LD chip, 47 Anode electrode, 48 Cathode electrode, 49 Pad, 49a Bonding layer, 50, 50a, 50b, 50c Fault detection circuit, 51 First fault detection circuit, 52 Second fault detection circuit, 53 Third fault detection circuit, 61 Comparator, 62, 62a Threshold generation circuit, 63 Variable impedance element, 70 Fault control circuit, 71 Fault detection control circuit, 72 Master control circuit, 73 Pulse generation control circuit, 74 Charge control circuit, 75 Driver control circuit, 76 Vertical synchronization signal generation circuit, 77 Horizontal synchronization signal generation circuit, 78 Light emission control signal generation circuit, 81, 82, 83, 84, 91 ADC, 92 Switcher, 100 Distance measurement device, 101 Light emitting unit, 102 driving unit, 103 power supply circuit, 104 light emitting side optical system, 105 light receiving side optical system, 106 light receiving unit, 107 signal processing unit, 108 control unit, 108a distance measuring unit, 109 temperature detection unit

Claims

1. A plurality of light-emitting elements arranged in a two-dimensional array, each having a first and second terminal; N first wirings (N is an integer of 2 or more) extending in a first direction, and N second wirings extending in a second direction intersecting the first direction and electrically connected to the N first wirings, respectively, the plurality of first terminal wirings being electrically connected to the first terminals of the light-emitting elements; a plurality of second terminal wirings electrically connected to the second terminals of the light-emitting elements, each electrically connected to N of the light-emitting elements; a plurality of selection circuits electrically connected to one of the plurality of first terminal wirings and the plurality of second terminal wirings, for selecting the light-emitting elements to be light-emitting; a plurality of drive circuits electrically connected to the other of the plurality of first terminal wirings and the plurality of second terminal wirings, for driving the plurality of light-emitting elements; and a plurality of capacitors electrically connected to the one of the plurality of first terminal wirings and the plurality of second terminal wirings, for storing electric charge to be supplied to the plurality of light-emitting elements. at least one fault detection circuit electrically connected to one of the plurality of first terminal wirings and the plurality of second terminal wirings, the fault detection circuit detecting an abnormality in a light emitting element that is not a target for emitting light.

2. The light emitting device according to claim 1, wherein the fault detection circuit detects the abnormality in which the first terminal and the second terminal of the light emitting element that is not to emit light are short-circuited.

3. The light emitting device according to claim 1, wherein the failure detection circuit detects an abnormality caused by at least a portion of the current flowing through the light emitting element that is the light emitting target being a leakage current flowing through the light emitting element that is not the light emitting target.

4. The light emitting device according to claim 1, wherein the failure detection circuit detects the abnormality before the corresponding light emitting element that is to emit light is driven by the corresponding drive circuit.

5. The light emitting device according to claim 1, wherein the failure detection circuit is disposed for each of the plurality of first terminal wirings or the plurality of second terminal wirings.

6. The light emitting device according to claim 5, wherein each of the plurality of fault detection circuits has a comparator that outputs an abnormality detection signal when the voltage of the corresponding first terminal wiring or second terminal wiring is equal to or higher than a predetermined threshold voltage.

7. The light emitting device according to claim 6, further comprising a threshold generating circuit that generates the threshold voltage based on a reference voltage having a voltage level higher than that of the threshold voltage.

8. The light emitting device according to claim 7, wherein the threshold generating circuit has a variable impedance element capable of adjusting a voltage division ratio of the reference voltage, and divides the reference voltage at the voltage division ratio adjusted by the variable impedance element to generate the threshold voltage.

9. The light emitting device according to claim 8, wherein the variable impedance element includes a variable resistor.

10. The light emitting device according to claim 1, wherein the failure detection circuit is disposed for each of two or more of the first terminal wirings or the second terminal wirings.

11. The light-emitting device according to claim 10, wherein the fault detection circuit comprises: a plurality of analog-to-digital converters that convert the voltages of the plurality of first terminal wirings or the plurality of second terminal wirings into digital signals, respectively; and an abnormality detection signal generation unit that generates an abnormality detection signal based on the plurality of digital signals output from the plurality of analog-to-digital converters.

12. The light-emitting device according to claim 11, wherein the plurality of analog-to-digital converters generate the digital signals in parallel during a period when the plurality of light-emitting elements are performing light-emitting operation, and the fault detection circuit generates the abnormality detection signal indicating that at least one of the light-emitting elements that is not intended to emit light has experienced an abnormality.

13. The light-emitting device according to claim 10, wherein the fault detection circuit has: a switch that selects one of the plurality of first terminal wirings or the plurality of second terminal wirings; and an analog-to-digital converter that performs analog-to-digital conversion of the voltage of the first terminal wiring or the second terminal wiring selected by the switch to generate an abnormality detection signal.

14. The light emitting device according to claim 13, wherein the switch selects the plurality of first terminal wirings or the plurality of second terminal wirings in sequence, and the fault detection circuit generates the abnormality detection signal for the light emitting element that is not to emit light and is connected to the plurality of first terminal wirings or the plurality of second terminal wirings selected in sequence by the switch.

15. The light-emitting device according to claim 1, further comprising a failure control circuit which stops the selection by the selection circuit connected to at least one of a non-target light-emitting element connected to the first terminal wiring or the second terminal wiring in which the abnormality has been detected and a target light-emitting element connected to the non-target light-emitting element and stops the driving of the drive circuit.

16. A light-emitting device as described in claim 15, further comprising a pulse generator that generates a pulse signal indicating that the abnormality has been detected, and the selection circuit connected to the light-emitting element that is the target for emitting light and is connected to the first terminal wiring or the second terminal wiring in which the abnormality has been detected via a light-emitting element that is the target for not emitting light discharges the corresponding capacitor based on the pulse signal.

17. A light emitting device as described in claim 15, comprising: a first synchronization signal generator that generates a first synchronization signal that specifies the timing for causing the multiple light emitting elements arranged in a two-dimensional array to emit light in sequence; and a second synchronization signal generator that generates a second synchronization signal that specifies the timing for causing two or more of the light emitting elements arranged in the first direction to emit light in sequence; wherein the failure control circuit, when the abnormality is detected, causes the first synchronization signal generator to stop generating the first synchronization signal and causes the second synchronization signal generator to stop generating the second synchronization signal.

18. The light emitting device according to claim 1, wherein the plurality of light emitting elements are surface emitting laser elements.

19. The light emitting device according to claim 18, wherein the plurality of light emitting elements are VCSELs (Vertical Cavity Surface Emitting Lasers).

20. A device comprising: a light-emitting unit that emits light toward a subject; a light-receiving unit that receives light reflected by the subject from the emitted light; and a distance measuring unit that detects the distance to the subject based on the light emitted by the light-emitting unit and the light received by the light-receiving unit, wherein the light-emitting unit includes: a plurality of light-emitting elements arranged in a two-dimensional array, each having a first and a second terminal; N first wirings (N is an integer of 2 or more) extending in a first direction; and N second wirings that extend in a second direction intersecting the first direction and are electrically connected to the N first wirings, respectively; a plurality of first terminal wirings that are electrically connected to the first terminals of the light-emitting elements; a plurality of second terminal wirings that are electrically connected to the second terminals of the light-emitting elements and each are electrically connected to N of the light-emitting elements; a plurality of selection circuits that are electrically connected to one of the first and second terminal wirings and select the light-emitting elements to be emitted; and a plurality of drive circuits that are electrically connected to the other of the first and second terminal wirings and drive the plurality of light-emitting elements. a plurality of capacitors electrically connected to one of the first and second terminal wirings for storing electric charges to be supplied to the plurality of light-emitting elements; and a fault detection circuit electrically connected to the one of the first and second terminal wirings for detecting an abnormality in which the anode and cathode of a light-emitting element that is not to emit light are short-circuited.

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