Light-emitting device and distance measuring device

Abstract

To provide a light-emitting device including a light-emitting element and enabling quick detection of the fault of the light-emitting element.SOLUTION: A light-emitting device comprises: a plurality of light-emitting elements arranged in a two-dimensional array, each of the light-emitting elements having a first terminal and a second terminal; N-lines of first wiring lines (N is an integer of 2 or more) extending in a first direction, and N-lines of second wiring lines extending in a second direction crossing the first direction and electrically connected to the N -lines of the first wiring lines respectively. The light-emitting device includes: a plurality of first terminal wiring lines electrically connected the first terminal of the light-emitting element; a plurality of second terminal wiring lines the electrically connected to the second terminal of the light-emitting element, each of the plurality of second terminal wiring lines electrically connected to N light-emitting elements of the plurality of light-emitting elements, and at least one failure detection circuit electrically connected to either of the plurality of first terminal wiring lines and the plurality of second terminal wiring lines, the failure detection circuit detects failure in a light-emitting element not light emission-matter.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] LiDAR (Light Detection and Ranging) is one of the methods to obtain distance measurement information. LiDAR irradiates light to an object for which distance measurement information is to be obtained, 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 does not have any physically movable parts in the light emitting unit and light receiving unit. In Solid State LiDAR, for example, an array-shaped light emitting unit is used to select the location to emit light, and light is projected onto the intended irradiation area. By sequentially switching the light emitting locations in the light emitting unit, a light emitting system that scans light in a two-dimensional area without a physical scanning mechanism can be realized. 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 is equipped with a light source in which light-emitting elements are arranged in an array, and a driving circuit, and is capable of driving the light-emitting elements of a selected light-emitting channel to emit light. By not having any physically moving parts, the risk of failure can be reduced 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2022-526998 Summary of the Invention [Problem to be solved by the invention]

[0005] As in Patent Document 1, an issue with the existing light-emitting system in which a plurality of anodes and cathodes are arranged in a matrix and driven individually is that when any of the light-emitting elements emits light, a reverse bias is applied to the non-target light-emitting element connected to the same cathode. The non-target light-emitting element to which the reverse bias is applied may cause 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 the target light-emitting element is connected to the cathode of the non-target light-emitting element that has a short circuit abnormality, the current flowing from the anode to the cathode of the target light-emitting element flows from the cathode of the non-target light-emitting element that has a short circuit abnormality to the anode, and the capacitor provided to make the target light-emitting element emit light in a pulsed manner is no longer charged, and the target light-emitting element may not be able to emit light. In addition, if a 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 abnormality, a capacitor provided to cause the non-light-emitting element to emit light in a pulsed manner may be unintentionally charged, and the non-light-emitting element may emit light due to the charge stored in the capacitor. In this case, the light-emitting element to be emitted and the non-light-emitting element may emit light at the same time, causing the light-emitting intensity of the light-emitting device to be higher than expected, which may violate the 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 of a light-emitting element before the light-emitting element emits light. In addition, since there is a period during which a slight leakage current flows from the cathode to the anode before a complete short circuit occurs in a light-emitting element, 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. [Means for solving the problem]

[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 terminal and a second terminal; a plurality of first terminal wirings including 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 of the second terminal wirings being 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 element to be a light emitting target; 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 configured to drive the plurality of light-emitting elements; a plurality of capacitors electrically connected to the one of the plurality of first terminal wirings and the plurality of second terminal wirings, and configured to store 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 light-emitting target. A light emitting device is provided.

[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 a current flowing through the light emitting element that is an object of emitting light being a leakage current flowing through the light emitting element that is not an object of emitting light.

[0011] The failure detection circuit may detect the abnormality before the corresponding light-emitting element that is to emit light is driven by the corresponding drive circuit.

[0012] The fault 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 the corresponding 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 is higher in voltage level 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 fault detection circuit may be disposed for each of two or more of the first terminal wirings or the second terminal wirings.

[0018] The fault detection circuit includes: 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; The digital signal generating unit may further include an abnormality detection signal generating 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 generate the digital signals in parallel during a period when the plurality of light-emitting elements are performing a light-emitting operation; The failure detection circuit may generate the abnormality detection signal indicating that at least one of the light-emitting elements that is not a light-emitting object has experienced an abnormality.

[0020] The fault detection circuit includes: a switch that selects one of the plurality of first terminal wirings or the plurality of second terminal wirings; The device may further include 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 selects the plurality of first terminal wirings or the plurality of second terminal wirings in sequence, The failure detection circuit may generate the abnormality detection signal for the light-emitting element that is not an object 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.

[0022] The device may further include a failure control circuit that 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 is detected and a target light-emitting element connected to the non-target light-emitting element, and stops driving of the drive circuit.

[0023] a pulse generator for generating a pulse signal indicating that the abnormality has been detected; The selection circuit connected to the light-emitting element that is an object to emit light and is connected to the first terminal wiring or the second terminal wiring in which the abnormality is detected via a light-emitting element that is an object to not emit light may discharge the corresponding capacitor based on the pulse signal.

[0024] a first synchronization signal generator that generates a first synchronization signal that defines a timing for sequentially causing the plurality of light-emitting elements arranged in a two-dimensional array to emit light; a second synchronization signal generator that generates a second synchronization signal that defines a timing for causing two or more of the light-emitting elements arranged in the first direction to emit light in sequence; When the abnormality is detected, the failure 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] According to the present disclosure, there is also provided an image capturing apparatus comprising: a light emitting unit that emits light toward a subject; a light receiving unit that receives light that is emitted and reflected by the subject; 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; Equipped with The light emitting unit is A plurality of light emitting elements arranged in a two-dimensional array, each having a first terminal and a second terminal; a plurality of first terminal wirings including 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 of the second terminal wirings being electrically connected to N of the light emitting elements; a plurality of selection circuits electrically connected to one of the first and second terminal wirings and configured to select the light emitting element to be a light emitting target; a plurality of drive circuits electrically connected to the other of the first and second terminal wirings and configured to drive the plurality of light-emitting elements; a plurality of capacitors electrically connected to the one of the first and second terminal wirings and configured to store electric charges to be supplied to the plurality of light-emitting elements; a fault detection circuit electrically connected to the one of the first and second terminal wirings and configured to detect an abnormality in which an anode and a cathode of a light-emitting element that is not a target for emitting light are short-circuited; A ranging device is provided. [Brief description of the drawings]

[0028] [Figure 1] FIG. 2 is a circuit diagram of the light emitting device according to the first embodiment. [Diagram 2]FIG. 4 is a circuit diagram showing the connections among a selection circuit, a light-emitting element, a drive circuit, and a failure detection circuit. [Figure 3A] FIG. 4 is a diagram showing a normal charging operation of a capacitor. [Figure 3B] 4A and 4B are diagrams showing light emitting operations of light emitting elements in a normal state; [Figure 3C] 13A and 13B are diagrams showing a charging operation of a capacitor when a light-emitting element fails. [Figure 4A] FIG. 2 is a diagram showing a first configuration example of the failure detection circuit according to the first embodiment. [Figure 4B] FIG. 2 is a diagram showing a first configuration example of the failure detection circuit according to the first embodiment. [Diagram 5] 4 is a graph showing electrical characteristics of a light-emitting element in a normal state and in a fault state. [Figure 6] 11 is a graph showing an example of adjusting a variable impedance element. [Figure 7] FIG. 2 is a block diagram showing the configuration of a failure control circuit according to the first embodiment. [Figure 8] 4 is a flowchart showing a light emitting operation of the light emitting device according to the first embodiment. [Figure 9] 4 is a timing chart of each signal during light emitting operation of the light emitting device according to the first embodiment. [Figure 10] 6 is a timing chart of each signal when a light-emitting element fails. [Figure 11] 11 is a timing chart of each signal at a precursor stage to a failure of a light-emitting element. [Figure 12] FIG. 1 is a cross-sectional view showing an example of a cross-sectional structure of a light emitting device having a VCSEL structure. [Figure 13] FIG. 13 is a diagram showing the configuration of a failure detection circuit according to a second embodiment. [Figure 14] FIG. 13 is a diagram showing the configuration of a failure detection circuit according to a third embodiment. [Figure 15] FIG. [Figure 16] FIG. 2 is a block diagram showing an example of the configuration of a distance measuring device as an implementation example of the light emitting device according to the embodiment. [Figure 17A] An explanatory diagram of the STL method. [Figure 17B] An explanatory diagram of the distance measurement principle of the STL method. [Figure 18] FIG. 1 is a block diagram showing an example of a schematic configuration of a vehicle control system. [Figure 19] FIG. 4 is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, an embodiment 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 have 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 the 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 9×9 light emitting elements 23 and 9×9 transistors 24. Thus, the light emitting device 1 shown in FIG. 1 includes a 9ch×9ch light emitting element array. The number of channels of the light emitting element array is arbitrary.

[0031] As shown in Fig. 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 wiring includes N first wirings (N is an integer of 2 or more) 31a, 32a, 33a extending in a first direction X, and N second wirings 31b, 32b, 33b extending in a second direction Y intersecting the first direction X and electrically connected to the N first wirings 31a, 32a, 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 wiring 31a and the second wiring 31b connected to each other are referred to as the first anode wiring 31, the second wiring 32a and the second wiring 32b connected to each other are referred to as the second anode wiring 32, and the third wiring 33a and the third wiring 33b connected to each other are referred to as the third anode wiring 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, each set consisting of the first to third anode wirings 31 to 33. Fig. 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 a first direction X (horizontal direction) and arranged along a 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 include a plurality (e.g., five) of first wirings 32a each extending in a first direction X (horizontal direction) and arranged along a second direction Y (vertical direction), and a plurality (e.g., five) of 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 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] Fig. 1 shows an example in which the light emitting device 1 according to the first embodiment includes five first horizontal wirings 31a, five first vertical wirings 31b, five second horizontal wirings 32a, five second vertical wirings 32b, five third horizontal wirings 33a, and five third vertical wirings 33b. Fig. 1 shows an example in which M sets of N first wirings and N second wirings are provided. The number of light emitting elements 23 shown in Fig. 1, represented by N and M, is N(M-2) x N(M-2).

[0038] The first to third anode wirings 31 to 33 may include Ma sets of the first to Nth horizontal wirings and Mb sets of the first to Nth vertical wirings (Ma and Mb are integers of 2 or more satisfying 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 the first switch of the present disclosure. The transistors 37b, 38b, and 39b are examples of the second switch 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 indicated by a thick solid line, the second anode wiring 32 is indicated by a thick dashed line, and the third anode wiring 33 is indicated 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 shape. These first horizontal wirings 31a and first vertical wirings 31b are electrically connected to each other at the points where the first horizontal wirings 31a and the 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 wires 31a to 33a extend in a first direction X (horizontal direction) and are adjacent to each other in a second direction Y (vertical direction). Although the first to third horizontal wires 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 wires 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 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 (9 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 to sandwich 9×9 light emitting elements 23. Each of the second to fourth sets of first to third vertical wirings 31b to 33b is arranged along one row (9 light emitting elements 23).

[0046] The anode of each light emitting element 23 is electrically connected to any 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 the 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 the first to third vertical wirings 31b to 33b. The anode of each light emitting element 23 may be electrically connected to any one of the first to third horizontal wirings 31a to 33a instead of being electrically connected to any 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 the 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 wire 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 a 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 element 23 to generate (output) light from the light-emitting element 23. For example, when light is to be generated from a certain light-emitting element 23, a predetermined signal is applied to the gate wiring 42 of the drive circuit E for this light-emitting element 23. This causes conduction between the source and drain of each transistor 24 in this drive circuit E, making it possible to pass a current through this light-emitting element 23. When a current flows through this light-emitting element 23, light is generated from this 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 drain of the transistor 37a and the drain of the transistor 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 accumulate charge in each of the first capacitors 34. The transistor 37b is used to discharge charge from each of the first capacitors 34. When a predetermined signal is applied to the gate of the transistor 37a, charge is accumulated in each of the first capacitors 34. When a predetermined signal is applied to the gate of the transistor 37b, charge is discharged from each of the first capacitors 34. Therefore, according to this embodiment, by selectively accumulating 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 through each of the light-emitting elements 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 charges in the second capacitors 35 by the second selection circuit 38, it is possible to pass a current through each light-emitting element 23 electrically connected to the second anode wiring 32. Furthermore, according to this embodiment, by storing charges in the third capacitors 36 by the third selection circuit 39, it is possible to pass a current through each light-emitting element 23 electrically connected to the third anode wiring 33.

[0055] [1st to 3rd 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 accumulates electric charge to be supplied to the light-emitting element 23 electrically connected to the first anode wiring 31. Each second capacitor 35 accumulates electric charge to be supplied to the light-emitting element 23 electrically connected to the second anode wiring 32. Each third capacitor 36 accumulates electric charge to be supplied to the light-emitting element 23 electrically connected to the third anode wiring 33. According to this embodiment, electric charge is supplied from the first to third capacitors 34 to 36 to each light-emitting element 23, so that a current can flow to each light-emitting element 23. Each of the first to third capacitors 34 to 36 has one electrode electrically connected to any 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 approximately square in a 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 of 2 or more). FIG. 1 shows an example where K is 4.

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

[0058] In each group, the first to third capacitors 34 to 36 are arranged in order in a clockwise direction. For example, the first capacitor 34, the second capacitor 35, and the third capacitor 36 of the first group are arranged on the left side, the center, and the right side, respectively, near the top side of the square. The first capacitor 34, the second capacitor 35, and the third capacitor 36 of the second group are arranged on the upper side, the center, and the lower side, respectively, near the right side of the square. As a result, the four groups of the 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 the fifth column among the 9×9 light emitting elements 23. In FIG. 1, the four groups of the 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 top left is close to the first capacitor 34 on the top side, but far from the first capacitor 34 on the bottom side. On the other hand, the light emitting element 23 at the bottom right is close to the third capacitor 36 on the right side, but far from the third capacitor 36 on the left side. Therefore, the average distance between the light emitting element 23 at the top left and the four first capacitors 34 is close to the average distance between the light emitting element 23 at the bottom right and the four third capacitors 36. This is similar 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 the present embodiment may include the first to third capacitors 34-36 only near one, two, or three of the four sides of the square. However, in this case, the first to third capacitors 34-36 are also desirably arranged symmetrically or nearly symmetrically with respect to the center of the square. Therefore, the light emitting device 1 of the present embodiment desirably includes the first to third capacitors 34-36 on two or more of the four sides of the square. For example, by arranging two sets of the first to third capacitors 34-36 near the top and bottom sides of the square, it is possible to realize an arrangement with two-fold rotational symmetry (180-degree rotational symmetry).

[0062] The light emitting device 1 according to the first embodiment includes a fault control circuit 70, and a first fault detection circuit, a second fault detection circuit, and a third fault detection circuit, which are 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 of the light emitting element 23 that is not 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 of the light emitting element 23 that is not 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 of the light emitting element 23 that is not 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] Fig. 2 is a circuit diagram showing the connection relationship between the selection circuits 37, 38, 39, the light-emitting element 23, the drive circuit E, and the failure detection circuits 51, 52, 53. Fig. 2 shows three selection circuits 37, 38, 39 arranged in the second direction Y (vertical direction) and a plurality of light-emitting elements 23a, 23b, 23c, 23d, 23e, 23f connected to two drive circuits Ea, Eb arranged in the first direction X (horizontal direction). Each of the two drive circuits Ea, Eb has transistors 24a, 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 simplification, Fig. 2 shows an example in which one first capacitor 34 is connected to the first selection circuit 37. Similarly, in Fig. 2, 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 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 (Anode1) 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 (Anode2) 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. Moreover, the discharge current of the third capacitor 36 is supplied to the anodes (Anode3) 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 driving circuit Ea controls the driving of the light-emitting element 23 (light-emitting elements 23a, 23b, and 23c in FIG. 2) connected thereto. The driving circuit Ea has a transistor 24a. The transistor 24a is connected between the cathodes of the light-emitting elements 23a, 23b, and 23c and a reference voltage (for example, ground voltage) node. When the transistor 24a is turned on, the cathode (Cathode 1) voltage of the light-emitting element 23 (23a, 23b, and 23c) connected to the drain of the transistor 24a drops to the reference voltage (for example, GND). For example, when 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 driving circuit Ea, causing the light-emitting element 23a to emit light. Similarly, when the second capacitor 35 or the third capacitor 36 is charged, the driving 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 has 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 emitting light, 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, when 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 emitting light may flow between the cathode and anode of the light-emitting element 23a that is not the target for emitting light. This current is referred to as a leakage current in this specification.

[0069] The first failure 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 subject to light emission. Similarly, the second failure 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 failure detection circuit 52. Moreover, the third failure 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 failure detection circuit 53. FIG. 2 shows an example in which two light-emitting elements 23 are connected to each of the first to third failure detection circuits 51 to 53, but the number of light-emitting elements 23 connected to each of the first to third failure detection circuits 51 to 53 is arbitrary.

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

[0071] 3A to 3C are diagrams for explaining the operation of the light emitting device 1. FIGS. 3A to 3B show the operation in a normal state, and FIG. 3C shows the operation in a fault state. FIGS. 3A to 3C show the operation when the light emitting element 23a emits light, as an example. Also, FIGS. 3A to 3C show the light emitting element 23b that is not to emit light. The light emitting element 23a that is to emit light has an anode (Anode1) connected to the first capacitor 34, the first selection circuit 37, and the first fault detection circuit 51 via the anode wiring 31. The light emitting element 23b has an anode (Anode2) 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 (Cathode1) 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 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 decrease, 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, so that the charge of the second capacitor 35 is discharged to the ground wiring GND and the charge of the second capacitor 35 is reset.

[0074] Fig. 3B is a diagram showing the 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 causes the cathode voltage of the light-emitting element 23a to drop. When the charge is discharged from the first capacitor 34 and a current flows between the anode and cathode of the light-emitting element 23a, the light-emitting element 23a emits light.

[0075] 3A and 3B, when the transistor 37a is turned on, the cathode of the non-emission light-emitting element 23b rises to a voltage level close to the power supply wiring (VDD) on the Anode1 side. When the transistor 38b is turned on, the anode of the light-emitting element 23b drops to a voltage level close to the ground voltage. As a result, a reverse bias is applied between the cathode and anode of the light-emitting element 23b. However, in the normal state, the resistance between the cathode and anode of the light-emitting element 23b is sufficiently large, so that no current flows between the cathode and anode of the light-emitting element 23b.

[0076] Fig. 3C is a diagram showing the charging operation of the first capacitor 34 when the light-emitting element 23b has a short circuit. 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. This causes a leakage current (also called a reverse bias current) in which the current to 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 to be supplied to the first capacitor 34 flows to the ground wiring (GND) on the Anode2 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. In addition, the current to 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 that is not to be emitted may unexpectedly emit light. In addition, the first capacitor 34 is not sufficiently charged, and the light-emitting intensity of the light-emitting element 23a that is to be emitted decreases or the light-emitting element 23a does not emit light.

[0079] Here, the second failure detection circuit 52 connected to the light-emitting element 23b detects an abnormality caused by at least a part of the current flowing through the light-emitting element 23a that is the target of light emission being a leakage current flowing through the light-emitting element 23b that is not the target of light emission, and outputs an abnormality detection signal. For example, the transistors 37a, 38a, and 24a are turned off by the abnormality detection signal output from the second failure detection circuit 52. This makes it possible to stop the light-emitting operation of the broken light-emitting element 23b and the light-emitting element 23a that is affected by the light-emitting element 23b.

[0080] 3C, the second failure detection circuit 52 can detect a leakage current at a stage 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 element 23a and the light-emitting element 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 of the light-emitting element 23, but the fault detection circuit 50 can detect abnormalities (e.g., crosstalk) other than a short circuit of the light-emitting element 23. That is, 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 higher than a predetermined threshold voltage Vth output from the threshold generation circuit 62. For example, the comparator 61 in the fault detection circuit 52 in FIG. 3C outputs an abnormality detection signal COUT when the voltage of the corresponding anode wiring 32 is equal to or higher than the threshold voltage Vth.

[0084] The threshold generating circuit 62 generates a threshold voltage Vth based on a reference voltage LDVDD having a voltage level higher than the threshold voltage Vth. Specifically, the threshold generating 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, and inputs it to the comparator 61. Although 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 showing a second configuration example of the fault detection circuit 50 according to the first embodiment. The fault detection circuit 50a shown in FIG. 4B has a threshold generation circuit 62a in which a variable resistor RV is provided 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, and inputs it 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 be composed of 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 0. 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, that is, 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 electrical characteristics of the light-emitting element 23 in a normal state and when it has failed. In Fig. 5, the vertical axis shows current (I) and the horizontal axis shows 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 precursor state to a short circuit, and an IV curve W3 of the light-emitting element 23 that has experienced a short circuit. Note that Fig. 5 shows an example in which the light-emitting element 23 has a linear I-V curve (also called ohmic) in all states.

[0090] In the normal state, no current flows through the light-emitting element 23 unless a breakdown voltage of a sufficiently high 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 a current begins to flow even at a voltage VM lower than voltage 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, a leakage current is detected from 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 the fault detection. FIG. 6 is a diagram showing the anode voltage waveform of the light emitting element 23 in which an abnormality has occurred. The vertical axis of FIG. 6 indicates the anode voltage of the light emitting element 23 in which an abnormality has occurred, and the horizontal axis indicates time. When the light emitting element 23 to be emitted and the non-light emitting element 23 to be connected at the cathode to each other cause a fault (for example, a short circuit fault), a leakage current flows in the anode wiring of the non-light emitting element 23 as the light emitting element 23 to be emitted emits light, and the anode voltage also rises. Therefore, when the anode voltage of the non-light emitting element 23 to be emitted exceeds a predetermined threshold voltage Vth (for example, a reference voltage LDVDD×0.1), it may be determined that a short circuit fault has occurred. The threshold voltage Vth can be set arbitrarily, and as shown in FIG. 6, the threshold voltage Vth can be set as small as LDVDD×0.00...01. The smaller the threshold voltage Vth is set, the faster the fault can be detected, but there is also a risk of misjudging noise as a fault.

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

[0093] 7 is a block diagram showing the configuration of the 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 where 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 a 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 generating circuit (first synchronization signal generator) 76, a horizontal synchronization signal generating circuit (second synchronization signal generator) 77, and a light emission control signal generating circuit 78. The vertical synchronization signal generating circuit 76 generates a vertical synchronization signal (first synchronization signal) VSYNC that specifies the timing at which the multiple 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 generating circuit 77 generates a horizontal synchronization signal (second synchronization signal) HSYNC that specifies the timing at which the multiple 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 generating circuit 78 generates a light emission trigger signal TRG_O that specifies 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, a 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 is turned 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 a pulse signal SEL_A so that charging of a capacitor connected to the light emitting element 23 to be connected to the non-light emitting element 23 to be connected to the abnormality is stopped, and generates a pulse signal SEL_C so that no current flows to the cathode of the non-light emitting element 23 to be connected to the abnormality is detected.

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

[0098] The driver control circuit 75 generates a control signal for controlling the gate of the NMOS transistor of the drive circuit connected to the corresponding cathode wiring based on the cathode selection signal SEL_C and the light emission trigger signal TRG_O. More specifically, when no abnormality is detected, a control signal is generated for turning on the NMOS transistor of the drive circuit connected to the cathode of the light emitting element 23 to be emitted during the period when the light emission trigger signal TRG_O is at a high level. As a result, during the period when the light emission trigger signal TRG_O is at a high level, a current from the capacitor flows between the anode and cathode of the light emitting element 23 to be emitted, and the light emitting element 23 emits light. On the other hand, when an abnormality is detected in the light emitting element 23 that is not the object of emission, the control signal is forcibly controlled 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 to the light emitting element 23 is connected to the light emitting element 23 is turned off. As a result, the light emission of the light emitting element 23 to be emitted is stopped.

[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 to charge the corresponding capacitors except the capacitor that has caused the short circuit. 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 to pass current to the cathodes of the corresponding light-emitting elements except the cathode of the light-emitting element that has caused the short circuit. As a result, the pulse generation control circuit 73 selects Anodes 1 to 4 and Cathodes 1 to 4 in sequence, respectively, to cause the light-emitting elements 23 on the light-emitting element array to emit light in sequence.

[0100] Furthermore, the pulse generation control circuit 73 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 (for example, 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 to apply 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] When the capacitor is being charged, the failure detection circuit 50 detects the anode voltage of the light-emitting element 23 that is not intended to emit light (for example, the light-emitting elements 23b and 23c) (step S4). The failure detection circuit 50 also compares the detected anode voltage with a threshold voltage Vth (step S5). Normally, no voltage is applied to the anode of the light-emitting element 23 that is not intended to emit light, so that the anode voltage of the light-emitting element 23 that is not intended to emit light has a voltage level lower than the threshold voltage Vth.

[0105] In step S5, if the anode voltage detected by the failure detection circuit 50 is at a voltage level lower than the threshold voltage Vth, the failure detection circuit 50 determines that no failure 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) to be emitted. More specifically, the driver control circuit 75 turns on a transistor (e.g., transistor 24a) in the drive circuit, so that the cathode of the light-emitting element 23 to be emitted is connected to the ground wiring (GND) (step S6). As a result, a current flows between the anode and cathode of the light-emitting element 23 to be emitted, and the light-emitting element 23 starts emitting light (step S7).

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

[0107] After the light emitting element 23 finishes 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 multiple light emitting elements 23 to emit light in sequence by repeating steps S1 to S8 in sequence for the multiple light emitting elements 23 on the light emitting element array.

[0108] In step S5, if the anode voltage detected by the failure detection circuit 50 is at a voltage level higher than the threshold voltage Vth, the failure detection circuit 50 detects a failure of the light-emitting element 23. The failure includes a short circuit anomaly and an anomaly in which a leak current flows from the cathode to the anode of the light-emitting element. As a result, the failure detection control circuit 71 transmits 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 to which the error signal ERR is input stops outputting the anode selection signal SEL_A and the cathode selection signal SEL_C. As a result, the driver control circuit 75 stops driving by the drive circuit to which the non-emission target light-emitting element in which the abnormality is detected is connected. In addition, the charge control circuit 74 stops selection by the selection circuit connected to the non-emission target light-emitting element 23 in which the abnormality is detected and selection by the selection circuit connected to the light-emitting element 23 to be emitted, which is connected to the drive circuit to which the non-emission target light-emitting element in which the abnormality is detected is connected. In addition, the charge control circuit 74 discharges the capacitor corresponding to the selection circuit connected to the light-emitting element 23 to be emitted that is connected to the drive circuit to which the non-emission target light-emitting element in which the abnormality is detected is connected (step S10).

[0110] Specifically, when the second fault detection circuit 52 in FIG. 3C detects an abnormality in the light-emitting element 23b that is not to be emitted 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, and stops driving. The charge control circuit 74 stops the selection by not turning on the transistor 38a in the second selection circuit 38 connected to the light-emitting element 23b. In addition, the charge control circuit 74 stops the selection by turning off the transistor 37a and turning on the transistor 37b in the first selection circuit 37 connected to the drive circuit Ea to which the light-emitting element 23b is connected, and connected to the light-emitting element 23a that is to be emitted and identified in step S1. As the transistor 37b is turned on, the first capacitor 34 corresponding to the first selection circuit 37 discharges the charge charged 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, the horizontal synchronization signal generation circuit 77, and the light emission control signal generation circuit 78 in the master control circuit 72 to stop generating the vertical synchronization signal VSYNC, the horizontal synchronization signal HSYNC, and the light emission trigger signal TRG_O, respectively (step S11).

[0112] 8, the failure detection circuit 50 can detect an abnormality in the non-target light-emitting element 23 (step S5) before the light-emitting element 23 emits light (step S7). As a result, when the 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 in the light emitting operation of the light emitting device 1 according to the first embodiment. For simplification, Fig. 9 shows an example in which a current flows alternately through the first anode wiring 31 (Anode1) and the second anode wiring 32 (Anode2). A plurality of light emitting elements 23 are connected to each of Anode1 and Anode2, and a current is supplied to the anodes of these light emitting elements 23 in turn. The time chart of Fig. 9 etc. shows an example in which a VCSEL (Vertical Cavity Surface Emitting LASER) in which a plurality of light emitting elements 23 are arranged two-dimensionally is used. 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. A plurality of light-emitting elements 23 connected to the same anode wiring are collectively called a slot. A plurality of slots in the light-emitting element array are selected in turn in synchronization with the output timing of the horizontal synchronization signal HSYNC. Such synchronization is also called slot synchronization.

[0116] At time t2, the pulse generation control circuit 73 selects, for example, Anode1 and Cathode1 by 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 starts 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. Anode 1 and the light emitting element 23 connected to Cathode 1 are 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 failure detection circuit 50 monitors Anodes 2 to N other than Anode 1, and confirms that the anode voltages do 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 a low level. This disconnects Cathode 1 from the ground wiring GND, and the light emission of the light-emitting element 23a ends, 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 (for example, Cathode 2) by 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 becomes a low level, or may select the next cathode at any timing from the end of the light emission of the light-emitting element 23 to the time when the next light-emitting element 23 is caused to emit light.

[0120] At time t5, the light emission trigger signal TRG_O becomes high level. As at time t3, Cathode 2 is connected to the ground wiring GND, the light emitting element 23 at the light emission coordinate (2,1) emits light, and the voltage level of Anode 1 drops. At time t6, the light emission trigger signal TRG_O becomes low level. 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 starts to rise again to the voltage level of the reference voltage LDVDD. In addition, 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 coordinate (3,1) corresponding to Anode 1 and Cathode 3 emits light. Note that the light emission operation of Cathode 4 and subsequent elements is omitted in FIG. 9.

[0121] At time t9, the horizontal synchronization signal HSYNC goes low. This causes Anode1 to be connected to the ground line GND, and the voltage of Anode1 drops to, for example, the ground voltage level. Also, the charge of the first capacitor 34 is discharged to the ground line GND.

[0122] Subsequently, at time t10, the horizontal synchronization signal HSYNC becomes high level. 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 starts to rise. Also, the second capacitor 35 connected to Anode2 is charged.

[0123] At time t11, the light emission trigger signal TRG_O becomes high level. As a result, Cathode1 is connected to the ground wiring GND, the light emitting element 23 at the light emission coordinate (1,2) connected to Anode2 and Cathode1 emits light, and the voltage level of Anode2 drops. From time t10 to t11, the failure detection circuit 50 monitors the anode voltages other than Anode2.

[0124] At time t12, the light emission trigger signal TRG_O becomes low level. This disconnects Cathode 1 from the ground wiring GND, and the light emission of the light emitting element 23 ends, and the voltage of Anode 2 starts 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, so that Anode2 is connected to the ground wiring GND and the voltage of Anode2 drops to, for example, the ground voltage level. Furthermore, the charge of 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 level to 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 after Anode 3 is not shown in FIG. 9.

[0127] At time t19, the master control circuit 72 sets the vertical synchronization signal VSYNC to high level to start the light emitting operation of 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, t23 to t24, and t25 to t26, the light emitting elements 23 at the 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] Fig. 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, a voltage is also applied to Anode2 due to a short-circuit failure of the light emitting element 23 as described in Fig. 3C.

[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 Anode1 side is applied to the Anode2 side. The fault detection circuit 50 monitors the voltage of the unselected Anode2 and detects that the voltage of Anode2 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 a 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 Anode1 side also drops due to voltage division. For example, Fig. 10 shows an example in which the voltage applied to Anode1 is about 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, and detect an abnormality in which the anode voltage does not reach a predetermined voltage level. Also, a failure detection circuit may be provided that monitors the anode voltage of the light-emitting element 23 on the light-emitting target side.

[0132] Fig. 11 is a timing chart for detecting an abnormality at a precursor stage to failure of the light-emitting element 23. 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 line VDD. In Fig. 11, the light-emitting element 23 has begun to fail, and a minute voltage is also applied to Anode2.

[0133] From time t43 to t44, the light emitting element 23 at the light emitting coordinates (1,1) performs a light emitting operation. From time t44 to t45, a voltage is applied to Anode1 again, but the failure of the light emitting element 23 progresses, and a voltage level equal to or higher 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 a high level. At time t46, the vertical synchronization signal VSYNC and the horizontal synchronization signal HSYNC go to a low level, and the light emitting device 1 stops its light emitting operation.

[0134] 11, an abnormality is detected at a precursor stage to a breakdown of the light-emitting element 23, 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 has 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 a substrate 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 the laser light is emitted from the back surface S3 side of the substrate 21. The laminated film 22 includes a first multilayer reflector, a first spacer layer, an active layer, a second spacer layer, and a second multilayer reflector, and the laser light generated in the active layer is resonated between the first multilayer reflector and the second multilayer reflector to improve the light intensity, and is emitted from the back surface S3 side of the substrate. In this specification, the LD chip 46 in FIG. 12 is a back-illuminated type. In this specification, the light emitting element 23 having the layer structure as shown in FIG. 12 is called 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. When 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, when viewed from the substrate 21 side, a cathode electrode 48 is disposed on the upper surface and side surface of the laminated film 22 disposed on the end side of the LD chip 46. When viewed from the substrate 21 side, the cathode electrode 48 is also disposed on the lowermost layer side 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 disposed in reverse. In FIG. 12, the common electrode is the cathode electrode 48, but the common electrode may be the anode electrode 47 and the 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 drive. 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 drive.

[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 wirings 31 to 33) 47 and a cathode electrode 48. Each light-emitting element 23 emits light when a current flows between the anode electrode 47 and the cathode electrode 48.

[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 emits light. This eliminates the risk of the light emitting device 1 emitting light at an emission luminance exceeding the safety standard for laser light, improving safety from the viewpoint 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 generating circuit 62. This makes it possible to forcibly stop the light emitting operation of the light emitting element 23 related to the abnormality, while allowing the light emitting operation of the other light emitting elements 23 to continue, thereby enabling the light emitting device 1 to be used effectively.

[0143] Second embodiment Various modifications of the configuration of the fault detection circuit 50 are possible. The fault detection circuit 50 according to the second embodiment is disposed for each of two or more anode wirings. For example, the fault detection circuit 50 may be configured by 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 has a plurality of analog-to-digital converters that convert the voltages of the plurality of anode wirings into digital signals, respectively. FIG. 13 and FIG. 14 described later show an example in which a light emitting device includes a plurality of light emitting element groups connected to the first to fourth anode wirings. In FIG. 13 and FIG. 14, the first anode wiring is called Anode1, the second anode wiring is called Anode2, the third anode wiring is called Anode3, and the fourth anode wiring is called Anode4. The fault detection circuit 50b in FIG. 13 has analog-to-digital converters (ADC: Analog to Digital Converters) 81, 82, 83, and 84 connected to Anode1, Anode2, Anode3, and Anode4, respectively.

[0144] The ADCs 81 to 84 perform analog-to-digital conversion of the voltages of Anode1 to Anode4, respectively, in parallel with a period during which the plurality of light-emitting elements 23 are performing light-emitting operations, to generate digital signals ADOUT1 to ADOUT4. These four digital signals ADOUT1 to ADOUT4 are combined, for example, by a wired OR to generate the abnormality detection signal ADOUT_ERR. This abnormality detection signal ADOUT_ERR is input to the failure 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, each of the analog-digital converters 81 to 84 compares the voltage levels of the anode wirings Anode1 to Anode4 with a predetermined threshold value before the light emitting element to be emitted starts a light emitting operation, and generates digital signals ADOUT1 to ADOUT4 indicating the comparison results.

[0146] An abnormality detection signal ADOUT_ERR obtained by combining the 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] In this way, the fault detection circuit 50b according to the second embodiment provides an ADC for each anode wiring to perform abnormality detection, and therefore can quickly detect an abnormality in a light-emitting element 23 that is not a target for light emission and is connected to any of the anode wirings. A plurality of digital signals output from a plurality of ADCs corresponding to a plurality of anode wirings are combined, for example, by a wired OR to generate an abnormality detection signal ADOUT_ERR, and therefore the circuit scale can be reduced. The abnormality detection signal ADOUT_ERR is generated before the light-emitting element 23 that is a target for light emission starts a light-emitting operation, so that a malfunction in which light is emitted at a light emission brightness that exceeds the safety standard for laser light can be prevented, and a light-emitting device that is excellent in safety from the viewpoint of eye safety can be realized.

[0148] (Third embodiment) In the second embodiment, multiple ADCs 81-84 are provided for each anode wiring, resulting in a large circuit scale. In the third embodiment, one ADC detects 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 FIG. 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 the multiple anode wirings in sequence. For example, when the light-emitting element 23 connected to Anode1 is performing a light-emitting operation, the switch 92 selects Anode2 to Anode4 in sequence. For example, during a charging period to the first capacitor 34 (for example, times t2 to t3 in FIG. 9), the switch 92 selects Anode2 to Anode4 in sequence within times t2 to t3 so that the voltages of all the anode wirings other than Anode1 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 one ADC, thereby reducing the circuit size and power consumption. By providing a switch to quickly switch between multiple anode wirings in order 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. In the distance measuring device 100, a light receiving device is required to receive the reflected light signal from the light emitting device 1 that is reflected by the object. The light emitting device 1 and the light receiving device may be disposed separately or 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 driving unit 3, a mounting substrate 13, a heat dissipation substrate 14, a correction lens holding portion 15, one or more correction 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 section and a signal processing section may be further 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 part 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 above-mentioned light-emitting side optical system 5. The light emitted from the light-emitting part 2 in the LD chip 11 is corrected by these correction lenses 16, and then irradiated onto the above-mentioned subject S. FIG. 15 shows two correction lenses 16 held by the correction lens holding part 15 as an example.

[0157] The wiring 17 is provided on the front, back, inside, etc. 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 surface of the mounting substrate 13, or a via wiring penetrating the mounting substrate 13. The wiring 17 of this embodiment further passes 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 mounting the light emitting device 1 according to this embodiment.

[0159] As shown in the figure, the distance measuring device 100 includes a light emitting unit 101, a driving unit 102, a power supply circuit 103, a light emitting side optical system 104, a light 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 described later, the light-emitting unit 101 in this example has light-emitting elements 23 using VCSELs as the respective light sources, and the light-emitting elements 23 are arranged in a predetermined manner, for example, in a matrix shape.

[0161] The driving unit 102 is configured to include 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, described later) for the driving unit 102 based on an input voltage (an input voltage Vin, 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 as a distance measurement target via a light-emitting side optical system 104. Then, the light thus irradiated is reflected from the subject S and enters a light-receiving surface of a 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 incident via the light receiving optical system 105 as described above, converts it into an electrical signal, and outputs it.

[0164] The light receiving unit 106 performs, for example, CDS (Correlated Double Sampling) processing, AGC (Automatic Gain Control) processing, etc., on the electrical signal obtained by photoelectrically converting the received light, and further performs A / D (Analog / Digital) conversion processing. Then, the signal is output as digital data to the signal processing unit 107 at the downstream side.

[0165] Moreover, 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 corresponding 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 types of signal processing on the digital signal input from the light receiving unit .

[0167] The control unit 108 is configured with, for example, a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., or an information processing device such as a DSP, and controls the drive unit 102 for controlling the light emission 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 enable identification of the three-dimensional shape of the subject S.

[0169] A specific distance measurement method used by 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 on 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] (Distance measurement method) The distance measuring method used in the distance measuring device 100 may be, for example, a Structured Light (STL) method or a Time of Flight (ToF) 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, a pattern light Lp having a dot pattern as 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 prevented from overlapping between blocks B).

[0175] FIG. 17B is a diagram illustrating the distance measurement principle of the STL method.

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

[0177] In addition, in the drawing, “BLn” means light of a certain block BL in the pattern light Lp, and “dn” means a 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 block BLn in the received light image is projected at the position of "dn'" in the figure. In other words, the position where the pattern of block BLn is projected in the received light image differs depending on whether or not there is a box BX; specifically, the pattern is distorted.

[0179] The STL method uses 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 method is adopted, for example, an IR (Infrared) light receiving unit using a global shutter method is used as the light receiving unit 106. In the case of the STL method, the distance measuring unit 108a controls the driving 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 way the pattern is distorted.

[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 when the light emitted by the light emitting unit 101 and received by the light receiving unit 106 is emitted and when it is received, 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 a 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] (Example of application to moving objects) 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 moving body such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility device, an airplane, a drone, a ship, a robot, etc.

[0185] FIG. 18 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a moving 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, as functional configurations of the integrated control unit 12050, a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (interface) 12053 are illustrated.

[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 mounted on 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 head lamps, back lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves or signals of various switches transmitted from a portable device that replaces a key may be input to the body system control unit 12020. The body system control unit 12020 receives the input of these radio waves or signals and controls the door lock device, power window device, lamps, and the like of the vehicle.

[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 an image outside the vehicle and receives the captured image. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for a person, a car, an obstacle, a sign, or characters on a road surface, based on the received image.

[0190] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal according 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.

[0192] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, the steering mechanism, or the braking device based on the information inside and outside the vehicle acquired by the outside-of-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output a control command to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control 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 the driver's operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle acquired 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-vehicle 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-vehicle information detection unit 12030, and perform cooperative control for the purpose of preventing glare, such as switching from high beams to low beams.

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

[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 an imaging unit 12031.

[0198] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided at positions such as the front nose, side mirrors, rear bumper, back door, and the upper part of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided at the front nose and the imaging unit 12105 provided at the upper part of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided at the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided at the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The images of the front acquired by the imaging units 12101 and 12105 are mainly used to detect a preceding vehicle, a pedestrian, an obstacle, a traffic light, a traffic sign, a lane, or the like.

[0199] 19 shows an example of the imaging ranges of the imaging units 12101 to 12104. An 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 an imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, an overhead image of the vehicle 12100 viewed from above is obtained by superimposing the image data captured by the imaging units 12101 to 12104.

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

[0201] For example, the microcomputer 12051 can extract, as a preceding vehicle, a three-dimensional object that is the closest three-dimensional object on the travel path of the vehicle 12100 and travels at a predetermined speed (for example, 0 km / h or more) in approximately the same direction as the vehicle 12100, by calculating the distance to each three-dimensional object in the imaging ranges 12111 to 12114 and the change over time of this distance (relative speed with respect to the vehicle 12100) based on the distance information obtained from the imaging units 12101 to 12104. Furthermore, the microcomputer 12051 can set a vehicle distance to be secured in advance in front of the preceding vehicle, and perform automatic brake control (including follow-up stop control) and automatic acceleration control (including follow-up start control). In this way, cooperative control can be performed for the purpose of automatic driving that travels autonomously without relying on the driver's operation.

[0202] For example, the microcomputer 12051 classifies and extracts three-dimensional object data on 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. Then, the microcomputer 12051 determines a collision risk indicating 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 imaging 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 or not a pedestrian is present in the captured images of the imaging units 12101 to 12104. The recognition of such a pedestrian is performed, for example, by a procedure of extracting feature points in the captured images of the imaging units 12101 to 12104 as infrared cameras, and a procedure of performing pattern matching processing on a series of feature points that indicate the contour of an object to determine whether or not the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the captured images of the imaging units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular contour line for emphasis on the recognized pedestrian. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating a pedestrian at a desired position.

[0204] An example of a vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to, for example, the imaging unit 12031 among the configurations described above. Specifically, a light emitting device 1 according to the present disclosure may be provided together with the imaging unit 12031. By applying the technology according to the present disclosure to the imaging unit 12031, it is possible to improve the resolution of a distance image while suppressing the generation of electromagnetic noise, and to improve 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 terminal and a second terminal; a plurality of first terminal wirings including 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 of the second terminal wirings being 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 element to be a light emitting target; 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 configured to drive the plurality of light-emitting elements; a plurality of capacitors electrically connected to the one of the plurality of first terminal wirings and the plurality of second terminal wirings, and configured to store 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 light-emitting target. Light emitting device. (2) 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 light emitting target are short-circuited. The light-emitting device according to (1). (3) The fault detection circuit detects an abnormality caused by a leakage current flowing through the light emitting element that is a non-light emitting element, in which at least a part of the current flowing through the light emitting element that is a light emitting element. A light-emitting device according to (1) or (2). (4) The fault detection circuit detects the abnormality before the corresponding light emitting element to be emitted is driven by the corresponding drive circuit. A light emitting device according to any one of (1) to (3). (5) the fault detection circuit is arranged for each of the plurality of first terminal wirings or the plurality of second terminal wirings; A light emitting device according to any one of (1) to (4). (6) 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. (5) A light-emitting device according to the present invention. (7) a threshold generating circuit that generates the threshold voltage based on a reference voltage having a voltage level higher than the threshold voltage; (6) A light-emitting device according to the present invention. (8) the threshold generation 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. (7) A light-emitting device according to (7). (9) The variable impedance element includes a variable resistor. (8) A light-emitting device according to (8). (10) the fault detection circuit is arranged for each of two or more of the first terminal wirings or the second terminal wirings; A light emitting device according to any one of (1) to (4). (11) The fault detection circuit includes: 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; an abnormality detection signal generating unit that generates an abnormality detection signal based on the plurality of digital signals output from the plurality of analog-to-digital converters; The light emitting device according to (10). (12) 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 a light-emitting operation; The malfunction detection circuit generates the malfunction detection signal indicating that at least one of the light emitting elements that is not a light emitting element has malfunctioned. The light emitting device according to (11). (13) The fault detection circuit includes: a switch that selects one of the plurality of first terminal wirings or the plurality of second terminal wirings; 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; The light emitting device according to (10). (14) The switch selects the plurality of first terminal wirings or the plurality of second terminal wirings in sequence, the fault detection circuit generates the abnormality detection signal for the light emitting element that is not a light emitting target connected to the plurality of first terminal wirings or the plurality of second terminal wirings selected in sequence by the switch; The light-emitting device according to (13). (15) a failure control circuit that stops the selection by the selection circuit connected to at least one of a non-emission target light-emitting element connected to the first terminal wiring or the second terminal wiring in which the abnormality is detected and a light-emitting element to be emitted connected to the non-emission target light-emitting element and stops the driving of the drive circuit; A light emitting device according to any one of (1) to (14). (16) a pulse generator for generating a pulse signal indicating that the abnormality has been detected; The selection circuit connected to the light-emitting element to be emitted that is connected to the first terminal wiring or the second terminal wiring in which the abnormality is detected via a light-emitting element to be not emitted discharges the corresponding capacitor based on the pulse signal. The light-emitting device according to (15). (17) a first synchronization signal generator that generates a first synchronization signal that defines a timing for sequentially causing the plurality of light-emitting elements arranged in a two-dimensional array to emit light; a second synchronization signal generator that generates a second synchronization signal that defines a timing for causing two or more of the light-emitting elements arranged in the first direction to emit light in sequence; When the abnormality is detected, the failure control circuit 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. A light-emitting device according to (15) or (16). (18) The plurality of light-emitting elements are surface-emitting laser elements. A light emitting device according to any one of (1) to (17). (19) The plurality of light-emitting elements are VCSELs (Vertical Cavity Surface Emitting Lasers), The light-emitting device according to (18). (20) A light emitting unit that emits light toward a subject; a light receiving unit that receives light that is emitted and reflected by the subject; 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; Equipped with The light emitting unit is A plurality of light emitting elements arranged in a two-dimensional array, each having a first terminal and a second terminal; a plurality of first terminal wirings including 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 of the second terminal wirings being electrically connected to N of the light emitting elements; a plurality of selection circuits electrically connected to one of the first and second terminal wirings and configured to select the light emitting element to be a light emitting target; a plurality of drive circuits electrically connected to the other of the first and second terminal wirings and configured to drive the plurality of light-emitting elements; a plurality of capacitors electrically connected to the one of the first and second terminal wirings and configured to store electric charges to be supplied to the plurality of light-emitting elements; a fault detection circuit electrically connected to the one of the first and second terminal wirings and configured to detect an abnormality in which an anode and a cathode of a light-emitting element that is not a target for emitting light are short-circuited; Ranging device.

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

[0207] 1, 1a light emitting device, 2 light emitting section, 3 driving section, 5 light emitting 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 sync signal generation circuit, 77 Horizontal sync signal generation circuit, 78 Light emission control signal generation circuit, 81, 82, 83, 84, 91 ADC, 92 Switch, 100 Distance measurement device, 101 Light emission unit, 102 Driving section, 103 power supply circuit, 104 light emitting optical system, 105 light receiving optical system, 106 light receiving section, 107 signal processing section, 108 control section, 108a distance measuring section, 109 temperature detection section

Claims

1. A plurality of light emitting elements arranged in a two-dimensional array, each having a first and a second terminal; a plurality of first terminal wirings including 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, and 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 of the second terminal wirings being 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 configured to select the light emitting element to be a light emitting target; 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 configured to drive the plurality of light-emitting elements; a plurality of capacitors electrically connected to the one of the plurality of first terminal wirings and the plurality of second terminal wirings, the capacitors storing electric charges 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, for detecting an abnormality in a light-emitting element that is not a target for emitting light; Light emitting device.

2. 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 light emitting target are short-circuited; The light emitting device according to claim 1 .

3. The fault detection circuit detects an abnormality caused by a leakage current flowing through the light emitting element that is a non-light emitting element, in which at least a part of the current flowing through the light emitting element that is a light emitting element. The light emitting device according to claim 1 .

4. The fault detection circuit detects the abnormality before the corresponding light emitting element to be emitted is driven by the corresponding drive circuit. The light emitting device according to claim 1 .

5. the fault detection circuit is arranged for each of the first terminal wirings or the second terminal wirings; The light emitting device according to claim 1 .

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

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

8. the threshold generation 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. The light emitting device according to claim 7.

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

10. the fault detection circuit is arranged for each of two or more of the first terminal wirings or the second terminal wirings; The light emitting device according to claim 1 .

11. The fault detection circuit includes: 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; an abnormality detection signal generating unit that generates an abnormality detection signal based on the plurality of digital signals output from the plurality of analog-digital converters; 11. The light emitting device according to claim 10.

12. The plurality of analog-to-digital converters generate the digital signals in parallel during a period in which the plurality of light-emitting elements are performing light-emitting operations; The failure detection circuit generates the abnormality detection signal indicating that at least one of the light emitting elements that is not a light emitting element has an abnormality.

12. The light emitting device according to claim 11.

13. The fault detection circuit includes: a switch that selects one of the plurality of first terminal wirings or the plurality of second terminal wirings; 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; 11. The light emitting device according to claim 10.

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

15. a failure control circuit that 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 is detected and a target light-emitting element connected to the non-target light-emitting element and stops driving the drive circuit; The light emitting device according to claim 1 .

16. a pulse generator for generating a pulse signal indicating that the abnormality has been detected; The selection circuit connected to the light emitting element to be a light emitting target 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 to be a non-light emitting target discharges the corresponding capacitor based on the pulse signal.

16. The light emitting device according to claim 15.

17. a first synchronization signal generator that generates a first synchronization signal that defines a timing for sequentially causing the plurality of light-emitting elements arranged in a two-dimensional array to emit light; a second synchronization signal generator that generates a second synchronization signal that defines a timing at which two or more of the light-emitting elements arranged in the first direction are caused to emit light in sequence; When the abnormality is detected, the failure control circuit 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.

16. The light emitting device according to claim 15.

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

19. The plurality of light-emitting elements are VCSELs (Vertical Cavity Surface Emitting Lasers), 20. The light emitting device of claim 18.

20. A light emitting unit that emits light toward a subject; a light receiving unit that receives light that is emitted and reflected by the subject; 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; Equipped with 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; a plurality of first terminal wirings including 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, and 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 of the second terminal wirings being electrically connected to N of the light emitting elements; a plurality of selection circuits electrically connected to one of the first and second terminal wirings and configured to select the light emitting element to be a light emitting target; a plurality of drive circuits electrically connected to the other of the first and second terminal wirings and configured to drive the plurality of light-emitting elements; a plurality of capacitors electrically connected to the one of the first and second terminal wirings and configured to store electric charges to be supplied to the plurality of light-emitting elements; a fault detection circuit electrically connected to the one of the first and second terminal wirings and configured to detect an abnormality in which an anode and a cathode of a light emitting element that is not a target for emitting light are short-circuited; Ranging device.

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