Laser light emitting device

Abstract

The laser light emitting device (10) of the present invention comprises: a plurality of laser light emitting sections, namely a plurality of laser light emitting sections (40), each having a laser diode (44), a drive circuit (42) for controlling the supply of drive current to the laser diode to drive the laser diode, and a drive line (43) for flowing the drive current from the drive circuit toward the laser diode; and a light emitting detection section (60), having a detection pattern (62) configured to flow a current electromagnetically induced corresponding to the drive current flowing through each drive line when each laser light emitting section emits light, and detecting the light emission of the driven laser diode by detecting the current flowing through the detection pattern.

Description

Technical Field

[0001] The present disclosure relates to a laser light emitting device. Background Art

[0002] The laser radar device includes a laser light emitting device for irradiating laser light (see Japanese Patent Application Laid-Open No. 10-104341).

[0003] In a laser light-emitting device, there is a case where the laser light emission timing is controlled or a non-lighting fault is detected by detecting the light emission of the laser. In the detection of laser light emission, generally, (a) a method of detecting the actual light emission using a photodiode with high-speed response characteristics and (b) a method of detecting the current flowing through a current mirror circuit attached to the drive circuit as a current corresponding to the drive current flowing through the laser diode are used. In addition, as a method of detecting the drive current, (c) a method of configuring a detection coil in the wiring through which the drive current flows and detecting the current flowing through the detection coil can also be used (see Japanese Utility Model Publication No. 5-11468).

[0004] Here, in a laser light-emitting device equipped with multiple laser diodes, a circuit for executing one of the above methods (a), (b), or (c) must be configured for each laser diode. Therefore, in a laser light-emitting device equipped with multiple laser diodes, the number of structures for detecting the light emitted by the laser diodes must be proportional to the number of laser diodes, resulting in an increase in the device structure and cost. Therefore, in a laser light-emitting device equipped with multiple laser diodes, it is desirable to be able to detect the light emitted by each laser diode using a simple and inexpensive structure. Summary of the Invention

[0005] According to one embodiment of the present disclosure, a laser light-emitting device is provided. The laser light-emitting device comprises: a plurality of laser light-emitting units, each including a laser diode; a drive circuit for controlling the supply of drive current to the laser diode to drive the laser diode; and drive lines through which the drive current flows from the drive circuit to the laser diode; and a light emission detection unit having a detection pattern configured to cause a current to flow through each drive line when each laser light-emitting unit emits light, resulting from electromagnetic induction corresponding to the drive current flowing through the drive line. The light emission of the driven laser diode is detected by detecting the current flowing through the detection pattern.

[0006] According to this laser light emitting device, since the light emission of the driven laser diode can be detected by the detection unit having one detection pattern, the light emission of the driven laser diode can be detected with a simpler and cheaper structure than the structure described in the subject. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The above-mentioned object and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings.

[0008] Figure 1 This is a schematic diagram of the structure of a laser light emitting device.

[0009] Figure 2 It is an explanatory diagram showing the detection of laser light emission from a laser diode to be driven.

[0010] Figure 3 This is a schematic structural diagram of a laser light emitting device after the arrangement of the detection pattern is changed.

[0011] Figure 4 This is a schematic structural diagram of a laser light emitting device with a changed detection pattern structure.

[0012] Figure 5 It is an explanatory diagram showing the magnetic flux interlinked with the detection pattern. DETAILED DESCRIPTION

[0013] A. Implementation method:

[0014] like Figure 1 As shown, the laser light emitting device 10 of the embodiment includes a power supply (denoted as "VS" in the figure) 20, four laser light emitting units 40, a light emission detection unit 60, and a control unit 80. Figure 1 The mutually orthogonal x, y, and z axes shown in the figure represent directions along the surface of the circuit board on which the laser light-emitting device 10 is mounted, and z represents a direction perpendicular to the surface. The arrangement of the four laser light-emitting units 40 and the detection pattern 62 of the light emission detection unit 60 is subject to restrictions based on the x, y, and z axes, as described below. Otherwise, there are no particular restrictions on the arrangement of the power supply 20, the detection resistor 64 and comparator 66 of the light emission detection unit 60 (described below), and the control unit 80.

[0015] The laser light emitting unit 40 includes a laser diode 44 and a drive circuit 42 that controls the on / off switching of the power supply from the power supply 20 to the laser diode 44 to drive the laser diode 44. In the drive circuit 42, a field effect transistor (FET) is used as an element for switching the power supply to the laser diode 44 on / off. The drive circuit 42 and the laser diode 44 are connected via a drive line 43, and a drive current Idv flows from the drive circuit 42 to the laser diode 44 in the drive line 43. Figure 1 In the example, the output of the drive circuit 42 is connected to the anode side of the laser diode 44, but the anode side of the laser diode 44 may be connected to the power supply 20, while the cathode side thereof may be connected to the drive circuit 42.

[0016] In addition, Figure 1 In order to distinguish the four laser light emitting units 40 and the various components, the suffixes _1, _2, _3, and _4 are added to the respective reference numerals. The suffix numbers indicate the order of the four laser light emitting units 40 from the top to the bottom of the figure. However, in the following description, these suffixes may be omitted when the four laser light emitting units 40 are not specifically distinguished.

[0017] The four laser light emitting units 40_1 to 40_4 are arranged on the +Z direction side of a mounting circuit board (not shown) so that the respective driving lines 43_1 to 43_4 are parallel to each other at predetermined intervals. Figure 1 In the example shown in FIG. 1 , linear driving lines 43_1 to 43_4 along the x direction are arranged in parallel along the y direction perpendicular to the x direction.

[0018] The laser light emitting units 40_1 to 40_4 are controlled by the control unit 80 to operate the drive circuits 42_1 to 42_4 to drive the laser diodes 44_1 to 44_4 .

[0019] The control unit 80 is comprised of, for example, a microcomputer. The CPU executes a pre-prepared program to control the drive circuits 42_1 to 42_4 of each laser light emitting unit 40_1 to 40_4, causing the laser diodes 44_1 to 44_4 to emit light in numerical order. Furthermore, the control unit 80 also functions as the emission detection processing unit 68, described later, detecting the drive timing, or emission timing, of the laser diodes 44 of each laser light emitting unit 40. The detected drive timing is used to control the drive of the laser diodes 44 of each laser light emitting unit 40.

[0020] The light emitting detection unit 60 includes a detection pattern 62, a detection resistor 64, a comparator 66, and a light emitting detection processing unit 68 of the control unit 80. The detection pattern 62 is a wiring pattern in the shape of a ring coil. When looking down at the front surface (the surface on the +Z direction side) of the installation where the four laser light emitting units 40_1 to 40_4 are arranged, the detection pattern 62 is arranged to be located between the second drive line 43_2 and the third drive line 43_3. In addition, when the mounting circuit substrate is a double-layer substrate, the detection pattern 62 is arranged on the mounting front or back surface, and when it is a multi-layer substrate with three or more layers, it is arranged on any one of the mounting front surface, back surface, and inner layer. In addition, it can also be arranged across multiple layers.

[0021] When any of the drive circuits 42_1 to 42_4 operates under the control of the control unit 80 and the drive current Idv_1 to Idv_4 flows through any of the drive lines 43_1 to 43_4, a concentric magnetic field centered on the drive line is generated. The detection pattern 62 is configured to exist in the generated magnetic field, and a detection current Idt is generated in the detection pattern 62. This detection current Idt changes according to the electromagnetic induction corresponding to the change in the direction and magnitude of the magnetic flux linked by the generation of the magnetic field. Figure 1 The symbol "·" in the circle "○" represents the interlinkage flux Φ in the +Z direction, and the symbol "×" in the circle "○" represents the interlinkage flux Φ in the -Z direction. This detection current Idt flows through the detection resistor 64 having a resistance value Rdt, thereby converting the detection current Idt into a detection voltage Vdt (= Idt·Rdt). In the following description, the detection current Idt is considered positive when flowing from the + side to the - side of the detection resistor 64, and negative when flowing from the - side to the + side. The detection voltage Vdt is considered positive when the direction corresponds to a positive detection current Idt, and negative when the direction corresponds to a negative detection current Idt.

[0022] like Figure 2 As shown, when the driven object is the first laser diode 44_1 or the second laser diode 44_2, the crosslink magnetic flux Φ of the detection pattern 62 is oriented in the -Z direction, and the generated detection current Idt and detection voltage Vdt are negative. In contrast, when the driven object is the third laser diode 44_3 or the fourth laser diode 44_4, the crosslink magnetic flux Φ of the detection pattern 62 is oriented in the +Z direction, and the generated detection current Idt and detection voltage Vdt are positive. However, the magnitude of the crosslink magnetic flux Φ is inversely proportional to the distance from the drive line through which the drive current flows. Therefore, the second laser diode 44_2, which is closer to the detection pattern 62, has larger crosslink magnetic flux Φ, detection current Idt, and detection voltage Vdt than the first laser diode 44_1, which is also closer to the detection pattern 62. Similarly, the third laser diode 44_3 has larger crosslink magnetic flux Φ, detection current Idt, and detection voltage Vdt than the fourth laser diode 44_4.

[0023] As described above, by detecting the generation of the detection voltage Vdt corresponding to the detection current Idt, it is possible to indirectly detect the emission of any of the laser diodes 44_1 to 44_4. Furthermore, by detecting the difference in direction and magnitude of the voltage Vdt, it is possible to distinguish which of the laser diodes 44_1 to 44_4 is emitting light.

[0024] Light emission detection unit 60 (see Figure 1) comparator 66 outputs a pulsed differential signal indicating which of the laser diodes 44_1 to 44_4 is emitting light, based on the direction and magnitude of the input detection voltage Vdt. For example, when a negative detection voltage Vdt is generated, comparator 66 outputs a pulsed differential signal in which the negative output terminal of comparator 66 changes to a higher voltage than the positive output terminal. When a positive detection voltage Vdt is generated, comparator 66 outputs a pulsed differential signal in which the positive output terminal of comparator 66 changes to a higher voltage than the negative output terminal. Furthermore, the voltage difference between the positive and negative outputs of comparator 66 changes depending on the magnitude of the detection voltage Vdt. For example, the second laser diode 44_2, which is closer to the detection pattern 62, outputs a larger voltage difference than the first laser diode 44_1, which is also closer to the detection pattern 62. Similarly, the third laser diode 44_3 outputs a larger voltage difference than the fourth laser diode 44_4.

[0025] The light emission detection processing unit 68 can detect the driving timing, i.e., the light emission timing, of any of the laser diodes 44_1 to 44_4 by detecting the timing of changes in the differential output from the comparator 66. Furthermore, the light emission detection processing unit 68 can detect which laser diode 44_1 to 44_4 is being driven, i.e., emitting light, based on the state of the differential output, specifically the direction of change and the voltage difference. Thus, the light emission detection processing unit 68 can detect the driving timing, i.e., the light emission timing, of the laser diode 44 being driven. Consequently, the control unit 80 can control the driving, i.e., the light emission, of the laser diode 44 being driven.

[0026] Furthermore, the light emission detection processing unit 68 can detect a failure in the laser light emitting unit 40 being driven by detecting that the differential output obtained from the comparator 66 does not change during a period when a change should occur. Detectable failures include not only open-circuit failures in the drive circuit 42, where no drive current is supplied to the laser diode 44, but also short-circuit failures in the drive circuit 42 or the laser diode 44, where the drive current is constantly supplied to the laser diode 44. In the case of a short-circuit failure, since the interlinkage magnetic flux Φ of the detection pattern 62 does not change, no detection current Idt is generated, similar to an open-circuit failure. The detection current Idt is a current generated by electromagnetic induction corresponding to the change in interlinkage magnetic flux Φ caused by the drive current. Therefore, when the drive current is constantly flowing, the generation of the drive current for the laser diode 44 cannot be detected, but a failure in the drive circuit 42 can be detected. However, in order to distinguish between an open circuit fault and a short circuit fault, it is necessary to detect whether a driving current is generated, such as whether a driving current is actually always generated or whether light is actually always emitted.

[0027] As described above, in the laser light-emitting device 10 of this embodiment, a single detection pattern 62 can be used to detect the light emission and timing of each of the multiple laser light-emitting units 40, more specifically, the driving and timing of the laser diode 44. Therefore, the driving and timing of the driven laser diode 44 can be detected using a simpler and less expensive structure than the structure described in the previous section. Furthermore, since the structure does not use a photodiode to detect actual light emission as described in the previous section, the driving timing of the laser diode 44 can be detected with high precision without being affected by interfering light. Furthermore, since the structure does not use a current mirror circuit, the driving timing of the laser diode 44 can be detected with high precision without being affected by a decrease in the operating speed of the drive circuit 42. Furthermore, it is possible to identify which of the multiple laser light-emitting units 40 has a fault. Furthermore, as a fault, not only an open circuit fault in the drive circuit 42 but also a short circuit fault in the drive circuit 42 or the laser diode 44 can be detected.

[0028] B. Other implementation methods:

[0029] B1. Other Implementation Methods 1:

[0030] As described in the above embodiment, the detection pattern 62 is placed between the second drive line 43_2 and the third drive line 43_3. It detects which of the four laser diodes 44_1 to 44_4 is being driven based on the direction and magnitude of the detection current, or more specifically, the direction and magnitude of the detection voltage generated by converting the detection current into a voltage. This utilizes the differences in the direction and magnitude of the interlinkage magnetic flux generated by the positional relationship between the detection pattern 62 and the four drive lines 43_1 to 43_4. If the differences in the direction and magnitude of the interlinkage magnetic flux can be utilized, for example, the detection pattern 62 can be placed between the first drive line 43_1 and the second drive line 43_2, or between the third drive line 43_3 and the fourth drive line 43_4.

[0031] In addition, if Figure 3 As shown, the detection pattern 62 can also be arranged on the opposite side of the fourth drive line 43_4 from the other drive lines 43_1 to 43_3. In this case, while the direction of the detection voltage Vdt remains the same, its magnitude varies depending on the distance between the detection pattern 62 and the drive lines 43_1 to 43_4. By detecting this difference, it is possible to determine which of the four laser diodes 44_1 to 44_4 is being driven. Similarly, although not shown, the detection pattern 62 can also be arranged on the opposite side of the first drive line 43_1 from the other drive lines 43_2 to 43_4.

[0032] The arrangement is not limited to this example as long as the direction and magnitude of the interlinkage magnetic flux generated by the positional relationship between the detection pattern 62 and the four driving lines 43_1 to 43_4 can be different.

[0033] In short, the detection pattern 62 is configured relative to the multiple driving lines 43 so that different detection currents can be generated according to the different positional relationships between the multiple driving lines 43 and the detection pattern 62, for example, according to at least one of the differences in the distance between the detection pattern 62 and the driving line 43 and the direction of the cross-linked magnetic flux of the detection pattern 62 generated by the driving current flowing in the driving line 43.

[0034] B2. Other Implementation Methods 2:

[0035] In addition, the detection pattern 62 of the embodiment (see Figure 1 ) is described with an annular coil wiring pattern as an example. However, it is not limited to this. Figure 4 As shown in FIG. 4 , a detection pattern 62C may be formed in a closed loop shape including a wiring pattern along the driving line 43 and connected to the detection resistor 64. However, when the detection pattern 62C is used, as shown in FIG. Figure 4 As shown, it is preferable to arrange the detection pattern 62C on the opposite side of the fourth driving line 43_4 and the other driving lines 43_1 to 43_3. In addition, although not shown, it is preferable to arrange the detection pattern 62C on the opposite side of the first driving line 43_1 and the other driving lines 43_2 to 43_4. This is because, for example, Figure 4 In Figure 1 Similarly, when the detection pattern 62C is arranged between the second driving line 43_2 and the third driving line 43_3 , it is difficult to detect changes in the interlinkage magnetic flux caused by the driving current flowing through the third driving line 43_3 and the fourth driving line 43_4 .

[0036] B3. Other implementation methods 3:

[0037] In the above embodiment and other embodiments 1 and 2, the description is based on the assumption that the linear drive lines 43_1 to 43_4 are arranged in parallel. However, the drive current Idv flowing from the drive circuit 42 to the laser diode 44 in the drive line 43 is actually a so-called circular current. Specifically, the drive current Idv flows from the bypass capacitor of the AC power supply of the drive circuit 42 through the power line on one side, flows from the drive circuit 42 through the drive line 43 to the laser diode 44, and returns to the bypass capacitor via the return line to the AC power supply (the power line on the other side). In this case, the magnetic flux of the magnetic field generated by the drive current Idv is strictly speaking not only the magnetic flux of the magnetic field generated by the current flowing through the portion of the drive line 43.

[0038] Here, as Figure 5 As shown, each drive line is formed as a loop line 43r_1 to 43r_4 that returns from the power supply (bypass capacitor) via the drive circuits 42_1 to 42_4 and the laser diodes 44_1 to 44_4 to the power supply. In this case, the loop currents flowing through the loop lines 43r_1 to 43r_4, i.e., the drive currents Idv1 to Idv4, generate, for example, Figure 5 However, the magnetic flux that contributes to the detection current Idt of the detection pattern 62 is the magnetic flux that interlinks with the detection pattern 62 (interlinkage magnetic flux). Therefore, it is not necessary to consider the entire loop current flowing through the loop wire 43r; instead, it is sufficient to consider the current corresponding to the interlinkage magnetic flux that contributes to the generation of the detection current Idt of the detection pattern 62.

[0039] Therefore, in the above embodiment and other embodiments 1 and 2, for ease of explanation, the case is described in which only the magnetic flux of the magnetic field generated by the driving current Idv flowing through the driving line 43 connecting the driving circuit 42 and the laser diode 44 is considered, and the detection current Idt generated by the cross-linked magnetic flux passing through the detection pattern 62 is detected.

[0040] Furthermore, the driving lines 43_1 to 44_4 are not limited to parallel, straight lines. The shape of the driving lines is not particularly limited, as long as the magnitude and direction of the magnetic flux interlinked with the detection pattern 62 due to the driving current Idv flowing through the driving lines 43 results in a difference in the magnitude of the detection current Idt generated in the detection pattern 62.

[0041] Alternatively, each drive line can be treated as a loop line 43r that returns from the power supply via the drive circuit 42 and the laser diode 44, rather than being omitted as in the embodiment and other embodiments 1 and 2. In this case, each loop-shaped drive line can have any shape if the magnitude and direction of the cross-linkage magnetic flux of the detection pattern 62 are different, resulting in the magnitude of the detection current Idt generated by the detection pattern 62. Furthermore, as the wiring pattern of the loop line 43r in the mounting substrate, it is preferable that the return wiring pattern from the laser diode 44 to the bypass capacitor is not arranged on the same layer of the mounting substrate as the wiring pattern from the power supply (bypass capacitor) via the drive circuit 42 to the laser diode 44, but on another layer of the multi-layer mounting substrate. In this way, the forward wiring pattern and the return wiring pattern can be arranged in a direction perpendicular to the mounting substrate, thereby shortening the wiring of the loop line 43r and reducing the inductance. Furthermore, since the directions of magnetic fields generated by currents flowing through both wiring patterns can be aligned, the magnitude of the interlinkage magnetic flux of the detection pattern 62 can be increased, and the magnitude of the detection current Idt can be increased, the detection accuracy can be improved.

[0042] B4. Other Implementation Methods 4:

[0043] In the above embodiment and other embodiments 1 and 2, the four laser light emitting units 40_1 to 40_4 are described as emitting light in numerical order, but this is not limiting. Alternatively, the four laser light emitting units 40_1 to 40_4 may be caused to emit light one by one, not in numerical order. Alternatively, a plurality of laser light emitting units may be caused to emit light collectively. In this case, at least the driving timing of the driven laser diode 44, i.e., the emission timing, can be detected.

[0044] B5. Other implementation methods 5:

[0045] In the above embodiment and other embodiments 1 and 2, a configuration in which a single laser diode 44 is driven by a single driver circuit 42 is used as an example, but the present invention is not limited thereto. Alternatively, a configuration may be employed in which multiple laser diodes are treated as a single laser diode that emits light simultaneously and driven by a single driver circuit. Alternatively, a configuration may be employed in which a single laser diode, or multiple laser diodes that emit light simultaneously, are driven as a single laser diode by multiple driver circuits that are driven simultaneously.

[0046] B6. Other implementation methods 6:

[0047] In the above embodiment and other embodiments 1 and 2, the configuration including four laser light emitting units 40 is described as an example. However, the number of laser light emitting units 40 is not particularly limited as long as it is two or more.

[0048] B7. Other implementations 7:

[0049] The present disclosure can also be implemented using various methods other than laser light emitting devices. For example, it can be implemented using various devices such as an object detection device equipped with a laser light emitting device. Furthermore, the object detection device is a radar (also known as "LiDAR (Light Detection and Ranging)") that emits laser light as irradiation light, receives light including reflected light from an object, and detects information related to the object, such as the presence or absence of the object and the distance to the object.

[0050] B8. Other implementations 8:

[0051] The control unit and method thereof described in the present disclosure may also be implemented by a special-purpose computer, which is provided by constituting a processor and a memory programmed to perform one or more functions concretized by a computer program. Alternatively, the control unit and method thereof described in the present disclosure may also be implemented by a special-purpose computer, which is provided by constituting a processor composed of one or more special-purpose hardware logic circuits. Alternatively, the control unit and method thereof described in the present disclosure may be implemented by one or more special-purpose computers, which are constituted by a combination of a processor and a memory programmed to perform one or more functions, and a processor composed of one or more hardware logic circuits. In addition, a computer program may also be stored as an instruction executed by a computer in a non-transient tangible recording medium that is readable by a computer.

[0052] The present disclosure is not limited to the above-described embodiments and can be implemented through various structures within the scope of the above-described subject matter. For example, the technical features of the embodiments corresponding to the technical features in the various methods described in the Summary of the Invention section can be appropriately replaced or combined to solve part or all of the above-described technical problems or achieve part or all of the above-described effects. In addition, the above-described technical features may be appropriately deleted as long as they are not described as essential structures in this specification.

Claims

1. A laser light emitting device, wherein: The laser light emitting device has: a plurality of laser light emitting units, each including a laser diode, a drive circuit for controlling supply of a drive current to the laser diode to drive the laser diode, and a drive line for allowing the drive current to flow from the drive circuit to the laser diode; as well as The light emission detection unit includes a detection pattern configured to cause a current to flow through the detection pattern when each laser light emitting unit emits light, resulting from electromagnetic induction corresponding to the drive current flowing through each drive line. The light emission of the driven laser diode is detected using a combination of the direction and magnitude of the current flowing through the detection pattern. The detection pattern is configured in a loop coil shape and is disposed between the drive lines of the plurality of laser light emitting units.

2. The laser light emitting device according to claim 1, wherein: The plurality of laser light emitting units emit light in sequence.

3. The laser light emitting device according to claim 1 or 2, wherein: The driving lines of the plurality of laser light emitting units are arranged to have different positional relationships with respect to the detection pattern.

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