Light source device, light emitting device and measuring device

Abstract

To provide a light source device or the like in which an ON state is not maintained when an ON signal to turn on a thyristor is not required.SOLUTION: A light source device includes: a light emitting part including a light emitting element having a thyristor; a setting part for setting the light emitting part as the light emitting element which emits light; and a control part which shifts the ON setting from the setting part to OFF after the light emitting element has been shifted to a light emittable state and makes the light emitting element emit light a plurality of times by turning on / off a light emitting current for making the light emitting element emit light.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a light source device, a light emitting device, and a measurement device. [Background technology]

[0002] Patent document 1 describes a light emitting device including a light source having a plurality of light emitting elements, a plurality of driving elements provided corresponding to the plurality of light emitting elements and driving the light emitting elements to light up when turned on, and a control unit that switches between a sequential lighting operation for lighting up the plurality of light emitting elements in sequence and a simultaneous lighting operation for lighting up the plurality of light emitting elements simultaneously in parallel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-158160 A Summary of the Invention [Problem to be solved by the invention]

[0004] 2. Description of the Related Art There is a light emitting device that includes a light emitting element having a thyristor, and causes the light emitting element to emit light by turning on the thyristor. The present invention provides a light source device and the like that does not maintain an on signal when an on signal for turning on a thyristor is not necessary. [Means for solving the problem]

[0005] The invention described in claim 1 includes a light-emitting unit including a light-emitting element having a thyristor, a setting unit that sets the light-emitting unit as a light-emitting element that emits light, and a control unit that, after the light-emitting element is brought into a state capable of emitting light, turns the on setting from the setting unit to off and turns on / off a light-emitting current that causes the light-emitting element to emit light, causing the light-emitting element to emit light a plurality of times. 、 Preparation The light emission interval when the light is emitted a plurality of times is set according to a predetermined period during which light can be emitted again after the light emission current to the light emitting element is turned off in a state in which there is no on setting from the setting unit. It is a light source device. Claim 2The invention described in claim 1 is the light source device according to claim 1, in which the light emitting element is caused to emit light one or more times before the on setting from the setting unit is shifted to off. Claim 3 In the invention described in the above, the control unit includes a driver that turns on / off a light-emitting current on the ground side of a power source that supplies a light-emitting current to the light-emitting element, and the off resistance of the driver is The above 2. The light source device according to claim 1, wherein the power supply voltage is set according to a period of time. Claim 4 In the present invention, the off-resistance of the driver is composed of a driver element and a resistor connected in parallel to the driver element. 3 2 is a light source device according to the first embodiment. Claim 5 The invention described in the above is characterized in that the off-resistance of the driver can be switched to a plurality of values. 3 2 is a light source device according to the first embodiment. Claim 6 The invention described in is a light source device as described in claim 1, characterized in that the control unit supplies a pulse having a current value smaller than the light-emitting current while the light-emitting element is being caused to emit light multiple times or before the light is emitted. Claim 7 The invention described in is a light source device as described in claim 1, characterized in that the setting unit is a shift unit that performs a shift operation to set the light-emitting element to be emitted by the light-emitting unit, and the control unit transitions the shift unit to an off state by setting the shift signal supplied to the shift unit to a ground potential. Claim 8 The invention described in is the light source device according to claim 1, characterized in that the control unit supplies to the light-emitting unit an erasing pulse that disables the light-emitting element from re-emitting light. Claim 9The invention described in the above is characterized in that the control unit includes a first driver that turns on / off a light-emitting current to the light-emitting element and the ground side of a power supply that supplies a light-emitting current, and a second driver that supplies the erase pulse, and the second driver has an on-resistance smaller than the off-resistance of the first driver and is set to a value that disables re-emission by turning on when the first driver is off. 8 2 is a light source device according to the first embodiment. Claim 10 The invention described in is a light-emitting device comprising a light-emitting section having a plurality of light-emitting elements each having a thyristor, and a setting section to which an on state is transferred in sequence and which sets the light-emitting elements to be caused to emit light in the light-emitting section when they become on, wherein the gates of the thyristors of the light-emitting elements are connected to a voltage supply line which supplies a light-emitting current to the light-emitting elements via a resistor. Claim 11 The invention described in the above is characterized in that the setting section is composed of a thyristor. 10 The light emitting device according to the present invention is Claim 12 The invention described in the item (1) has a substrate, the light emitting element is provided on the substrate by stacking a surface light emitting element and a thyristor in this order, and the thyristor of the setting portion is provided on a structure equivalent to the light emitting element on the substrate. 11 The light emitting device according to the present invention is Claim 13 In the present invention, the surface light emitting element and the thyristor are electrically separated from each other. 12 The light emitting device according to the present invention is Claim 14 The invention described in claims 1 to 9 and a light receiving unit that receives light emitted from the light emitting unit of the light source device and reflected by an object to be measured. Effect of the Invention

[0006] According to the invention recited in claim 1, when it is not necessary to maintain the ON signal, the ON signal can be prevented from being maintained. Claim2 According to the invention described in the above, repeated emission of light from the light emitting element can be ensured. Claim 3 According to the invention described in the above, the light-emitting current rises faster than when it is not supplied from the ground side. Claim 4 According to the invention described in the above, the off-resistance can be set with a simple configuration. Claim 5 According to the invention described in the above, the period during which re-emission is possible can be selected. Claim 6 According to the invention described in the above, the period during which re-emission is possible can be adjusted. Claim 7 According to the invention described in the above, the supply of current to the shift section can be stopped. Claim 8 According to the invention described in the above, the light emitting section can be initialized. Claim 9 According to the invention described in the above, the light emitting section can be easily initialized. Claim 10 According to the invention described in the above, the period during which the light emitting element is capable of re-emitting light can be set by the resistance value. Claim 11 According to the invention described in the above, the shift operation is easier to perform than in the case where a thyristor is not used. Claim 12 According to the invention described in the above, the characteristics of the light emitting element are improved as compared with the case where the light emitting element is provided on a thyristor. Claim 13 According to the invention described in the above, the light emitting element can be turned on / off on the ground side, compared to a case where the light emitting element is not electrically isolated. Claim 14 According to the invention described in the above, a measuring device capable of measuring a three-dimensional shape is provided. [Brief description of the drawings]

[0007] [Figure 1] 1A and 1B are diagrams illustrating a light source device to which a first embodiment is applied. [Diagram 2]1A and 1B are diagrams illustrating the operation of a light-emitting device including a shift thyristor, a coupling transistor, a light-emission control thyristor, and a VCSEL, where (a) is an equivalent circuit, and (b) is a cross-sectional view of a portion of the shift thyristor and the coupling transistor. [Diagram 3] 1A and 1B are diagrams illustrating a layout and a cross section of a light emitting device, where (a) is the layout, and (b) is a cross section taken along line IIIB-IIIB in (a). [Figure 4] 4 is a timing chart showing the operation of the light source device to which the first embodiment is applied. [Diagram 5] 5 is a timing chart showing an operation of a light source device to which the first embodiment is not applied. [Figure 6] 13 is a diagram showing the voltage in the emission control thyristor and the emission current of the VCSEL in a series connection of the emission control thyristor and the VCSEL, where (a) is a set timing chart, and (b) is the voltage in the emission control thyristor and the emission current of the VCSEL. [Figure 7] 1 shows an equivalent circuit of a light-emission control thyristor and a VCSEL, where (a) is a diagram showing the equivalent circuit and (b) is a diagram showing the parasitic capacitance of a semiconductor layer and a pn junction. [Figure 8] 13 is a diagram showing the cathode voltage of the light-emission control thyristor and the light-emission current of the VCSEL when the off-resistance of the driver is changed. FIG. [Figure 9] 11 is another diagram showing the cathode voltage of the light-emission control thyristor and the light-emission current of the VCSEL when the off-resistance of the driver is changed, where (a) shows the entire light-emission current, and (b) is an enlarged view of the light-emission current in (a). [Figure 10] 11 is a timing chart illustrating a method for setting a longer period during which the VCSEL is capable of re-emitting light. [Figure 11] 11A and 11B are diagrams illustrating a light source device to which a second embodiment is applied. [Figure 12] 13A and 13B are diagrams illustrating a light source device to which a third embodiment is applied. [Figure 13] 11 is a timing chart illustrating the timing of providing an erase pulse. [Figure 14] FIG. 2 is a block diagram illustrating a configuration of a measurement device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Here, a light source device will be described which does not maintain the on state when it is not necessary to maintain the on state of a setting unit or a thyristor in a light emitting element having a thyristor. Until now, it was thought that the light-emitting element would not turn on unless the setting unit or the thyristor in a light-emitting element having a thyristor was maintained in the on state. However, there was a risk that unnecessary power would be consumed if the setting unit or the thyristor in a light-emitting element having a thyristor was maintained in the on state. In addition, it was thought that the on state of the light-emitting element could be cleared by turning off ("L") the light-emitting signal that causes the light-emitting element to emit light. However, if the light-emitting signal is turned on ("H") when the light-emitting element is in an on state or can transition to an on state, there was a risk of malfunction, such as a light-emitting element that should not be emitted emitting light.

[0009] [First embodiment] Fig. 1 is a diagram for explaining a light source device 1 to which the first embodiment is applied. In Fig. 1, the right direction on the paper surface is the +x direction. Thyristors and transistors are indicated by symbols, and resistors are indicated by rectangles. The same applies to other cases. The light source device 1 shown in FIG.

[0010] (Light emitting device 10) The light emitting device 10 includes a GND terminal, a VGK terminal, a φ1 terminal, a φ2 terminal, a VLD terminal, and a Vdrv terminal on one side (the −x direction side). Note that GND is a ground potential that is a reference voltage (hereinafter, referred to as ground potential GND, and the same applies below), VGK is a power supply potential (power supply potential VGK), VLD is a light emitting voltage VLD that supplies a light emitting current, and Vdrv is a driver voltage Vdrv that is output by a driver that turns on / off the light emitting current.

[0011] The light emitting device 10 includes a light emitting section 11 and a shift section 12. The light emitting section 11 includes a plurality of vertical cavity surface emitting lasers VCSELs (Vertical Cavity Surface Emitting Lasers) and emission control thyristors S. Hereinafter, the vertical cavity surface emitting lasers VCSELs are referred to as VCSELs. In FIG. 1, six VCSELs (VCSEL(1) to VCSEL(6)) and six emission control thyristors S (emission control thyristors S(1) to S(6)) are shown. The anodes of the VCSELs and the cathodes of the emission control thyristors S are connected. That is, the VCSELs and the emission control thyristors S of the same number are connected in series. The six VCSELs and the six emission control thyristors S are arranged from one side (-x direction side) to the other side (+x direction side). The series-connected VCSELs and the emission control thyristors S are an example of a light emitting element having a thyristor. The light emitting element may be an element in which the pn junction of a thyristor emits light, and this element is also a light emitting element having a thyristor.

[0012] The shift section 12 includes a plurality of shift thyristors T, coupling transistors Q, power supply line resistances Rg, current limiting resistances RL, and coupling resistances Rc. Six shift thyristors T (shift thyristors T(1) to T(6)) and six coupling transistors Q (coupling transistors Q(1) to Q(6)) are shown. Note that six power supply line resistances Rg, six current limiting resistances RL, and six coupling resistances Rc are included, but are not numbered. One shift thyristor T, coupling transistor Q, power supply line resistance Rg, current limiting resistance RL, and coupling resistance Rc constitute a shift unit 12a. Six shift units 12a are arranged from one side (-x direction side) to the other side (+x direction side). The shift section 12 includes a power supply line resistance Rg and a start resistance at an end on one side (-x direction side). Furthermore, the light emitting device 10 includes current limiting resistances R1 and R2.

[0013] In the shift unit 12a, the light-emission control thyristor S and the coupling transistor Q are connected. The coupling transistor Q in the shift unit 12a is connected to the light-emission control thyristor S of the light-emitting section 11. In other words, the light-emission control thyristors S(1) to S(6) are connected to the coupling transistors Q(1) to Q(6), and the coupling transistors Q(1) to Q(6) are connected to the same numbers as the light-emission control thyristors S(1) to S(6). Here, six light-emission control thyristors S, coupling transistors Q, light-emission control thyristors S, and VCSELs are shown, but other numbers may be used.

[0014] In the light emitting device 10, the VGK terminal is connected to a power supply line 71, the GND terminal is connected to a ground line 73, the φ1 terminal is connected to a shift signal line 72-1, the φ2 terminal is connected to a shift signal line 72-2, the VLD terminal is connected to a voltage supply line 74, and the Vdrv terminal is connected to a driver voltage line 75. When there is no need to distinguish between the shift signal lines 72-1 and 72-2, they are referred to as shift signal lines 72.

[0015] The control unit 50 includes buffers Buf1 and Buf2, power supplies VS1 and VS2, a driver Drv, and a light-emitting current limiting resistor RI. The buffer Buf1 supplies a shift signal p1 to the φ1 terminal of the light-emitting device 10. The buffer Buf2 supplies a shift signal p2 to the φ2 terminal of the light-emitting device 10. The power supply VS1 generates a power supply potential VGK and supplies it to the VGK terminal of the light-emitting device 10. The power supply VS1 also serves as a power supply for the buffers Buf1 and Buf2. That is, when the shift signals p1 and p2 are at the H level, the buffers Buf1 and Buf2 output a voltage that is approximately equal to the power supply VS1, and when the shift signals p1 and p2 are at the L level, they output a voltage that is approximately equal to the ground potential GND. The power supplies for the buffers Buf1 and Buf2 may be independent of the power supply potential VGK.

[0016] The power supply VS2 generates a light-emitting voltage VLD and supplies it to the VLD terminal of the light-emitting device 10. The driver Drv uses, for example, an NMOS transistor as a driver element, and is turned on / off by a light-emitting signal pI applied to the gate. The source of the NMOS transistor is grounded, and the drain is connected to the Vdrv terminal via a light-emitting current limiting resistor RI. When the driver Drv is turned on, it supplies a ground potential GND to the Vdrv terminal of the light-emitting device 10. By turning on / off the light-emitting current on the ground potential side (ground side), the rise of the light-emitting current becomes faster. As described later, the driver Drv has a preset on-resistance Ron and off-resistance Roff. The on-resistance Ron is the resistance when the driver Drv is on, and the off-resistance Roff is the resistance when the driver Drv is off. The off-resistance Roff may be configured by the structure of an NMOS transistor, or may be configured by controlling the gate voltage of the NMOS transistor. The off-resistance Roff may be configured by providing a resistor between the source and drain of the NMOS transistor that has a smaller resistance value than when the NMOS transistor is off. In this way, the off-resistance Roff can be easily set. Note that other elements such as an insulated gate bipolar transistor (IGBT) may be used instead of the NMOS transistor. Note that the NMOS transistor and the IGBT are examples of the driver element.

[0017] The connection relationship in the light emitting device 10 will be explained using an enlarged view. The light-emission control thyristor S may be referred to as the light-emission control thyristor, the shift thyristor T as the shift thyristor, and the coupling transistor Q as the coupling transistor. The light-emission control thyristor S and the shift thyristor T may be referred to as the thyristor without distinction.

[0018] (Operation of shift thyristor, coupling transistor, VCSEL and light emission control thyristor) Here, the basic operation of the light emitting device 10 will be described. The shift thyristor and the light-emission control thyristor are thyristors with an npnp structure. The thyristors are equipped with an n-type cathode K (hereinafter, written as cathode K, and the same applies below), a p-type gate Gp (p-gate Gp), an n-type gate Gn (n-gate Gn), and a p-type anode A (anode A). Note that the light-emission control thyristor S does not use the p-gate Gp for control, so it is not shown.

[0019] The coupling transistor is a multi-collector npn bipolar transistor. The coupling transistor has an n-type emitter E (emitter E), a p-type base B (base B), and n-type collectors Cf, Cs (collector Cf, Cs).

[0020] The above symbols are used without distinction between thyristors and coupling transistors. The same applies to the bipolar transistors that make up the thyristors described below. However, as described below, the thyristor is composed of a combination of single-collector npn bipolar transistors and pnp bipolar transistors. Therefore, they are written as emitter E, base B, and collector C. In the following, even if symbols are not attached to the figures, the symbols are used as anode A, cathode K, n-gate Gn, p-gate Gp, emitter E, base B, and collector C.

[0021] The shift thyristor T, the coupling transistor Q, the light-emission control thyristor S, and the VCSEL are composed of a III-V compound semiconductor such as GaAs. Here, the forward voltage (diffusion potential) Vd of the junction of this compound semiconductor is 1.5V, and the saturation voltage Vc of the bipolar transistor composed of the compound semiconductor is 0.3V. The ground potential GND is 0V, the power supply potential VGK, and the light-emission voltage VLD are 5V. The shift signals p1, p2, and the light-emission signal pI are signals whose L level is 0V ("L" (0V)) and whose H level is 5V ("H" (5V)). The driver Drv is turned off when the light-emission signal pI becomes "L" (0V), and turned on when the light-emission signal pI becomes "H" (5V).

[0022] 2 is a diagram explaining the operation of the light emitting device 10 using the shift thyristor T(1), the coupling transistor Q(1), the light emitting control thyristor S(1), and the VCSEL(1). Fig. 2(a) is an equivalent circuit, and Fig. 2(b) is a cross-sectional view of the shift thyristor T(1) and the coupling transistor Q(1). Fig. 2(a) also shows the shift thyristor T(2).

[0023] As shown in FIG. 2(a), the shift thyristor T(1) is composed of a combination of an npn bipolar transistor Tr1 (hereinafter, referred to as npn transistor Tr1) and a pnp bipolar transistor Tr2 (hereinafter, referred to as pnp transistor Tr2). The base B of the npn transistor Tr1 is connected to the collector C of the pnp transistor Tr2, and the collector C of the npn transistor Tr1 is connected to the base B of the pnp transistor Tr2. The emitter E of the npn transistor Tr1 is the cathode K of the shift thyristor T(1), the collector C of the npn transistor Tr1 (the base B of the pnp transistor Tr2) is the n gate Gn of the shift thyristor T(1), the collector C of the pnp transistor Tr2 (the base B of the npn transistor Tr1) is the p gate Gp of the shift thyristor T(1), and the emitter E of the pnp transistor Tr2 is the anode A of the shift thyristor T(1). The emitter E of the npn transistor Tr1, which is the cathode K of the shift thyristor T(1), is connected to a ground line 73 connected to a GND terminal to which a ground potential GND is supplied. The emitter E of the pnp transistor Tr2, which is the anode A of the shift thyristor T(1), is connected to a shift signal line 72-1 connected to the φ1 terminal. The n gate Gn is connected to a connection point between the start resistor Rs and the power supply line resistor Rg connected in series. The other side (the side that is not the connection point) of the start resistor Rs is connected to a shift signal line 72-2 connected to the φ2 terminal. The other side (the side that is not the connection point) of the power supply line resistor Rg is connected to a power supply line 71 connected to a VGK terminal to which a power supply potential VGK is supplied. A shift signal p1 is supplied to the φ1 terminal. A shift signal p2 is supplied to the φ2 terminal.

[0024] The coupling transistor Q(1), which is an npn transistor, has a base B connected to the p gate Gp (the base B of the npn transistor Tr1 and the collector C of the pnp transistor Tr2) of the shift thyristor T(1), and an emitter E connected to a ground line 73. The collector Cf is connected to a power supply line 71 to which a power supply potential VGK is supplied via a coupling resistor Rc and a power supply line resistance Rg connected in series. The connection point between the coupling resistor Rc and the power supply line resistance Rg is connected to the n gate Gn of the shift thyristor T(2).

[0025] The npn transistor Tr1 in the shift thyristor T(1) and the coupling transistor Q(1) form a current mirror circuit. That is, a current proportional to the current flowing through the npn transistor Tr1 flows through the coupling transistor Q(1).

[0026] The collector Cs of the coupling transistor Q(1) is connected to the n-gate Gn of the light-emitting control thyristor S(1), and is also connected, via a current-limiting resistor RL, to a voltage supply line 74 that is connected to a VLD terminal to which a light-emitting voltage VLD is supplied.

[0027] As described above, the VCSEL(1) and the light-emission control thyristor S(1) are connected in series. In other words, the anode A of the VCSEL(1) and the cathode K of the light-emission control thyristor S(1) are connected. The anode A of the light-emission control thyristor S(1) is connected to a voltage supply line 74. The cathode K of the VCSEL(1) is connected to a driver voltage line 75 that is connected to a Vdrv terminal to which a driver voltage Vdrv is supplied.

[0028] The anode A of the shift thyristor T(2) is connected to the shift signal line 72-2 connected to the φ2 terminal. As shown in FIG. 1, the anode A of the odd-numbered shift thyristors T is connected to the shift signal line 72-1, and the anode A of the even-numbered shift thyristors T is connected to the shift signal line 72-2. Except for the connection relationship between the shift thyristors T and the shift signal lines 72-1 and 72-2, the connection relationships of the shift thyristors T numbered 2 or more, the coupling transistors, the light-emission control thyristors S, and the VCSELs are the same as those of the shift thyristor T(1), the coupling transistor (1), the light-emission control thyristor S(1), and the VCSEL(1). Hereinafter, they may be referred to as a shift signal p1(φ1) and a shift signal p2(φ2).

[0029] First, the operation of the shift thyristor T(1) will be described. First, the power supply line 71 is set to a power supply potential VGK (5V), the ground line 73 is set to a ground potential GND (0V), and the shift signals p1 (φ1) and p2 (φ2) are set to "L" (0V). At this time, the npn transistor Tr1 and the pnp transistor Tr2 constituting the shift thyristor T(1) are in an off state. The n gate Gn of the shift thyristor T(1) is connected to the connection point between the start resistor Rs and the power supply line resistance Rg connected in series. The other side (the side other than the connection point) of the start resistor Rs is connected to the shift signal line 72-2 of "L" (0V), and the other side (the side other than the connection point) of the power supply line resistance Rg is connected to the 5V power supply line 71. Therefore, the n gate Gn becomes a voltage obtained by dividing the voltage difference (5V) between the start resistor Rs and the power supply line resistance Rg. If the resistance ratio between the start resistor Rs and the power supply line resistor Rg is 1:5, for example, the n gate Gn becomes 0.83V. Note that the light emission signal pI is "L" (0V) and the driver Drv is off. Therefore, the driver voltage Vdrv is not supplied to the driver voltage line 75. This state is referred to as the initial state.

[0030] Here, when the shift signal p1 (φ1) transitions from "L" (0V) to "H" (5V), the voltage difference between the emitter E ("H" (5V)) and base B (p-gate Gp) (0.83V) of the pnp transistor Tr2 of the shift thyristor T(1) of 4.17V becomes equal to or greater than the forward voltage Vd (1.5V), the emitter E-base B becomes forward biased, and the pnp transistor Tr2 transitions from the OFF state to the ON state. Then, the collector C (base B of the npn transistor Tr1) of the pnp transistor Tr2 becomes 4.7V, which is the emitter E ("H" (5V)) minus the saturation voltage Vc (0.3V). The voltage difference (4.7V) between the emitter E (0V) and base B (4.7V) of the npn transistor Tr1 becomes equal to or greater than the forward voltage Vd (1.5V), and the emitter E and base B become forward biased, so the npn transistor Tr1 transitions from the off state to the on state. The npn transistor Tr1 and the pnp transistor Tr2 in the shift thyristor T(1) transition to the on state, so the shift thyristor T(1) transitions from the off state to the on state. The transition of the shift thyristor T from the off state to the on state is referred to as turning on. The transition of the shift thyristor T from the on state to the off state is referred to as turning off.

[0031] In the initial state, when the shift signal p1 (φ1) transitions from "L" (0V) to "H" (5V), the shift thyristor T(1) turns on and transitions from the off state to the on state. Therefore, the state in which the anode A can turn on when it becomes "H" (5V) is expressed as the state in which it can transition to the on state. The same applies to other cases.

[0032] When the shift thyristor T(1) turns on, the n gate Gn of the shift thyristor T(1) becomes 0.3V, which is the saturation voltage Vc. Also, the anode A becomes a voltage determined by the sum of the forward voltage Vd and the saturation voltage Vc (Vd+Vc) and the voltage drop due to the internal resistance of the shift thyristor T. Here, it is assumed that the anode A becomes 1.9V. In other words, when the shift thyristor T(1) turns on, the shift signal line 72-1 transitions from 5V to 1.9V. Then, the p gate Gp of the shift thyristor T(1) becomes 1.6V.

[0033] As described above, the shift thyristor T(1) turns on when the voltage of the n gate Gn becomes lower than the voltage of the anode A by the forward voltage Vd (1.5 V) or more. The shift thyristor T(1) turns off when the voltage of the shift signal line 72-1 (the voltage between the anode A and the cathode K) becomes less than the above 1.9 V. For example, when the anode A becomes "L" (0 V), the voltage difference between the anode A and the cathode K becomes 0 V, so the shift thyristor T(1) turns off. On the other hand, if the voltage of the shift signal line 72-1 (the voltage difference between the anode A and the cathode K) is 1.9 V or more, the shift thyristor T(1) is maintained in the on state. Therefore, 1.9 V is represented as the holding voltage. Even if the holding voltage is applied, if there is no current flowing to maintain the shift thyristor T(1) in the on state, the shift thyristor T(1) is not maintained in the on state. The current that maintains the on-state is referred to as the holding current.

[0034] Next, the operation of the coupling transistor Q(1) will be described. If the shift thyristor T(1) is in the off state, the npn transistor Tr1 is in the off state. Therefore, the coupling transistor Q(1) is also in the off state. At this time, in the coupling transistor Q(1), the emitter E is set to the ground potential GND (0V). The collector Cf is at the power supply potential VGK (5V) via the power supply line resistance Rg and the coupling resistance Rc, which are connected in series. In addition, the collector Cs is at the light-emitting voltage VLD (5V) via the current limiting resistance RL.

[0035] When the shift thyristor T(1) turns on, that is, when the npn transistor Tr1 is turned on, the p-gate Gp of the shift thyristor T(1) becomes 1.6V as described above. Then, since the base B of the coupling transistor Q(1) is connected to the p-gate Gp of the shift thyristor T(1), the forward voltage Vd (1.5V) or more is applied between the emitter E and base B, that is, the coupling transistor Q(1) transitions from the off state to the on state. Then, the collector Cf becomes the saturation voltage Vc (0.3V) (the collector Cs will be described later). The connection point between the power supply line resistance Rg and the coupling resistance Rc (the n-gate Gn of the shift thyristor T(2)) becomes a voltage obtained by dividing the voltage difference (4.7V) between the voltage of the power supply line 71 (5V) and the voltage of the collector Cf (0.3V) by the power supply line resistance Rg and the coupling resistance Rc. If the resistance ratio of the power supply line resistance Rg and the coupling resistance Rc is 5:1 as an example, the connection point between the power supply line resistance Rg and the coupling resistance Rc (the n gate Gn of the shift thyristor T(2)) becomes 1.08V.

[0036] The anode A of the shift thyristor T(2) is connected to the shift signal line 72-2 to which the shift signal p2 (φ2) is supplied. Since the shift signal p2 (φ2) is "L" (0V), the shift thyristor T(2) does not turn on. However, when the shift signal p2 (φ2) transitions from "L" (0V) to "H" (5V), the anode A of the shift thyristor T(2) becomes "H" (5V), and the voltage difference (3.92V) with the n gate Gn (1.08V) becomes equal to or greater than the forward voltage Vd (1.5V), that is, the n gate Gn-anode A becomes forward biased, and the shift thyristor T(2) turns on. In this way, there are a plurality of elements, and the operation in which the elements that are turned on among the plurality of elements transition one after another is the shift operation. Also, in the embodiment in this specification, the element that is turned on or off by this shift operation is the shift element. By using the shift thyristor T, the shift operation is easy to perform.

[0037] Finally, the operation of the light-emission control thyristor S(1) and the VCSEL(1) will be described. The collector Cs of the coupling transistor Q(1) is connected to the n-gate Gn of the light-emitting control thyristor S(1). Therefore, when the coupling transistor Q(1) is turned on, the pn junction between the anode An and gate Gn of the light-emitting control thyristor S becomes forward, and the collector Cs draws in a current from the light-emitting voltage VLD through the pn junction between the anode An and gate Gn of the light-emitting control thyristor S, resulting in a voltage of approximately 3.5V obtained by subtracting the forward voltage Vd (1.5V) from the light-emitting voltage VLD (5V). Here, when the driver Drv is turned on and the driver voltage Vdrv becomes the GND voltage (0V), the cathode K of the VCSEL(1) becomes 0V. Therefore, the voltage difference (5V) between the light-emitting voltage VLD (5V) and the driver voltage Vdrv (0V) is applied between the anode A of the light-emitting control thyristor S(1) and the cathode K of the VCSEL(1). As a result, the light-emission control thyristor S(1) is turned on, and a current flows through the series-connected light-emission control thyristor S(1) and VCSEL(1), causing the VCSEL(1) to emit light. When the coupling transistor Q(1) is turned on and the n-gate Gn of the light-emission control thyristor S(1) is at 3.5V, the VCSEL(1) emits light when the driver Drv is turned on. Therefore, this state, in which the coupling transistor Q(1) is turned on and the anode An and gate Gn of the light-emission control thyristor S(1) are forward biased (3.5V), is referred to as a state in which the VCSEL(1) is capable of emitting light. The light-emission control thyristor S controls the light emission of the VCSEL by the potential of the n-gate Gn, and is therefore referred to as the light-emission control thyristor. Here, when the shift thyristor T and coupling transistor Q of the shift unit 12 are turned on and the anode An and gate Gn of the light-emission control thyristor S are forward biased, this is referred to as an on-setting from the shift unit 12. The turning off of the shift thyristor T and the coupling transistor Q of the shift unit 12 is expressed as the ON setting from the shift unit 12 transitioning to OFF. Furthermore, the saturation voltage Vc (here, 0.3 V) supplied from the collector Cs to the n-gate Gn of the light-emission control thyristor S when the coupling transistor Q is turned on is expressed as an ON signal. The ON signal transitions the light-emission control thyristor S to a state in which it can emit light.

[0038] That is, the initial state is a state in which the power supply line 71 is set to the power supply potential VGK (5V), the ground line 73 is set to the ground potential GND (0V), the shift signals p1 (φ1) and p2 (φ2) are "L" (0V), the driver Drv is off, and the driver voltage Vdrv is not supplied to the driver voltage line 75. In the initial state, the shift thyristor T(1) is in a state in which it can transition to the ON state. Here, when the shift signal p1 (φ1) (shift signal line 72-1) transitions from "L" (0V) to "H" (5V), the shift thyristor T(1) turns on and transitions from the OFF state to the ON state. When the shift thyristor T(1) turns on, the coupling transistor Q(1) transitions from the OFF state to the ON state. Then, the anode A and the n-gate Gn of the light-emission control thyristor S(1) are forward biased, and the VCSEL(1) is in a state in which it can emit light. Furthermore, when the coupling transistor Q(1) is turned on, the shift thyristor T(2) is able to transition to the on state. When the shift signal p2 (φ2) (shift signal line 72-2) transitions from "L" (0V) to "H" (5V), the shift thyristor T(2) turns on. When the shift signal p1 (φ1) (shift signal line 72-1) transitions from "H" (5V) to "L" (0V), the cathode K and anode A of the shift thyristor T(1) become "L" (0V), and the shift thyristor T(1) is turned off. The other shift thyristors T, coupling transistors Q, light-emission control thyristors S and VCSELs operate in the same manner.

[0039] As shown in FIG. 2(b), the light emitting device 10 is configured by stacking a plurality of semiconductor layers (see FIG. 3 described later). FIG. 2(b) shows a portion where an n-type semiconductor layer 85, a p-type semiconductor layer 86, an n-type semiconductor layer 87, and a p-type semiconductor layer 88 constituting the shift thyristor T(1) and the coupling transistor Q(1) are stacked. The shift thyristor T(1) is configured with the n-type semiconductor layer 85 as the cathode K, the p-type semiconductor layer 86 as the p-gate Gp, the n-type semiconductor layer 87 as the n-gate Gn, and the p-type semiconductor layer 88 as the anode A. On the other hand, the coupling transistor Q(1) is configured with the n-type semiconductor layer 85 as the emitter E, the p-type semiconductor layer 86 as the base B, and the n-type semiconductor layer 87 as the collectors Cf and Cs. Here, the cathode K of the shift thyristor T(1) and the emitter E of the coupling transistor Q(1) are electrically connected via the n-type semiconductor layer 85. Similarly, the p-gate Gp of the shift thyristor T(1) and the base B of the coupling transistor Q(1) are electrically connected via a p-type semiconductor layer 86. And, the n-gate Gn of the shift thyristor T(1) and the collectors Cf, Cs of the coupling transistor Q(1) are both composed of an n-type semiconductor layer 87, but are separated. The same is true for the other shift thyristors T and coupling transistors Q.

[0040] Fig. 3 is a diagram illustrating the layout and cross section of the light emitting device 10. Fig. 3(a) is the layout, and Fig. 3(b) is a cross section taken along line IIIB-IIIB in Fig. 3(a). Fig. 3(a) mainly illustrates the shift thyristors T(1)-(4), the coupling transistors Q(1)-(4), the light emission control thyristors S(1)-S(4), and the VCSEL(1)-(4). Fig. 3(b) illustrates a cross section of the light emission control thyristor S(1), the VCSEL(1), the shift thyristor T(1), the coupling transistor Q(1), the coupling resistor Rc connected to the coupling transistor Q(1), and the power line resistor Rg.

[0041] As shown in FIG. 3(b), the light emitting device 10 is configured by stacking an n-type semiconductor layer 81, an active layer 82, a p-type semiconductor layer 83, a tunnel junction layer 84, an n-type semiconductor layer 85, a p-type semiconductor layer 86, an n-type semiconductor layer 87, and a p-type semiconductor layer 88 on an n-type semiconductor substrate 80. The n-type semiconductor substrate 80 is an example of a substrate. Elements such as the shift thyristor T, the coupling transistor Q, the light emission control thyristor S, and the VCSEL are configured from a plurality of islands separated by removing a part of the semiconductor layer by etching. The island may be referred to as a mesa, and the etching for forming the island (mesa) may be referred to as mesa etching. In the following, the islands (islands 300, 301 to 307) will be described, focusing on the island 301 on which the light emission control thyristor S(1) and the VCSEL(1) are provided, and the island 302 on which the shift thyristor T(1) and the coupling transistor Q(1) are provided.

[0042] The island 300 is a portion in which the shift section 12 (see FIG. 1) such as the shift thyristor T(1) and the coupling transistor Q(1) is provided, and an n-type semiconductor layer 81, an active layer 82, a p-type semiconductor layer 83, a tunnel junction layer 84, and an n-type semiconductor layer 85 are left on an n-type semiconductor substrate 80 without being removed.

[0043] A VCSEL(1) and a light-emission control thyristor S(1) are stacked on an island 301. A shift thyristor T(1) and a coupling transistor Q(1) shown in FIG. 2(b) are provided on an island 302. A current-limiting resistor RL is provided on an island 303, and a power supply line resistor Rg and a coupling resistor Rc are provided on an island 304. A power supply line resistor Rg and a start resistor Rs are provided on an island 305. A current-limiting resistor R1 is provided on an island 306, and a current-limiting resistor R2 is provided on an island 307.

[0044] The layout and cross section will be described below with reference to FIGS. Around the island 301, the n-type semiconductor layer 81, the active layer 82, the semiconductor layer 83, the tunnel junction layer 84, and the semiconductor layers 85 to 88 are removed by etching. A p-ohmic electrode 321 that easily makes ohmic contact with the p-type semiconductor layer is provided on the p-type semiconductor layer 88. An n-ohmic electrode 331 that easily makes ohmic contact with the n-type semiconductor layer is provided on the n-type semiconductor layer 87 that is exposed by removing the p-type semiconductor layer 88. In the VCSEL (1), the n-type semiconductor layer 81 is the cathode K (see FIG. 2(a)), the active layer 82 is the active layer, and the p-type semiconductor layer 83 is the anode A. In the light-emitting control thyristor S (1), the n-type semiconductor layer 85 is the cathode K, the p-type semiconductor layer 86 is the p-gate Gp (p-gate layer), the n-type semiconductor layer 87 is the n-gate Gn (n-gate layer), and the n-type semiconductor layer 88 is the anode A. The n-ohmic electrode 331 is the n-gate Gn of the light-emission control thyristor S(1).

[0045] As shown in FIG. 3(b), a VCSEL(1) is provided on an n-type semiconductor substrate 80, and an emission control thyristor S(1) is provided on the VCSEL(1) via a tunnel junction layer 84. The tunnel junction layer 84 prevents a p-type semiconductor layer 83 of the VCSEL(1) and an n-type semiconductor layer 85 of the emission control thyristor S(1) from being reverse biased, making it difficult for a current to flow. The tunnel junction layer 84 is an n-type semiconductor layer doped with a high concentration of n-type impurities. ++ layer and p-type highly doped p ++ Even in the case of reverse bias, a current flows due to the tunnel effect.

[0046] The island 301 is cylindrical except for the portion where the n-ohmic electrode 331 is provided. The p-ohmic electrode 321 is provided in an annular shape on the p-type semiconductor layer 88 of the cylindrical island 301. A part of the semiconductor layer constituting the p-type semiconductor layer 83 exposed by etching is oxidized from the cylindrical outer periphery, forming a current blocking portion β through which current does not easily flow in an annular shape. On the other hand, the central portion that is not oxidized becomes a current passing portion α through which current easily flows. Light is emitted from the central portion of the annular p-ohmic electrode 321. The current blocking portion β is formed by providing an AlAs layer or an AlGaAs layer with a high Al concentration in the p-type semiconductor layer 83, and oxidizing the exposed outer periphery to oxidize Al. The peripheral portion of the VCSEL (1) has many defects due to etching, and non-radiative recombination is likely to occur. Therefore, by providing the current blocking portion β, the power consumed by non-radiative recombination is suppressed. By providing the current blocking portion β, it is possible to reduce power consumption and improve light extraction efficiency. The light extraction efficiency is the amount of light that can be extracted per unit of electric power.

[0047] 3(a) and 3(b), the VCSEL(1) emits light through the light-emission control thyristor S(1). Note that the light-emission control thyristor S(1) (tunnel junction 84, semiconductor layers 85-88) in the portion of the island 301 from which the light is emitted may be removed. In this case, the light-emission control thyristor S(1) becomes cylindrical. This prevents the light emitted by the VCSEL(1) from being absorbed by the light-emission control thyristor S(1) and causing a decrease in the amount of light.

[0048] Around the island 302, the p-type semiconductor layer 86, the n-type semiconductor layer 87, and the p-type semiconductor layer 88 are removed by etching (see FIG. 2(b)). A p-ohmic electrode 322 is provided on the p-type semiconductor layer 88. The p-ohmic electrode 322 is an electrode (anode A electrode) connected to the anode A of the shift thyristor T(1), and is connected to a shift signal line 72-1 to which a shift signal p1 (φ1) is supplied. N-ohmic electrodes 332, 333, and 334 are provided on the n-type semiconductor layer 87 exposed by removing the p-type semiconductor layer 88. The n-ohmic electrodes 332 and 334 are electrodes (collector Cf and Cs electrodes) connected to the collectors Cs and Cf of the coupling transistor Q(1). The n-type semiconductor layer 87 between the p-ohmic electrode 322 and the n-ohmic electrodes 332 and 334 is removed (see FIG. 2(b)). The n-ohmic electrode 333 is an electrode (n-gate Gn electrode) connected to the n-gate Gn of the shift thyristor T(1).

[0049] Around the island 303, the p-type semiconductor layer 86, the n-type semiconductor layer 87, and the p-type semiconductor layer 88 are removed by etching. Furthermore, in the island 303, two n-ohmic electrodes 335, 336 are provided on the exposed n-type semiconductor layer 87. The n-type semiconductor layer 87 between the two n-ohmic electrodes 335, 336 is a current limiting resistor RL.

[0050] Island 304 is configured similarly to island 303. Three n-ohmic electrodes 337, 338, and 339 are provided on n-type semiconductor layer 87 exposed by removing p-type semiconductor layer 88. The n-type semiconductor layer 87 between n-ohmic electrodes 337 and 338 is a coupling resistance Rc, and the n-type semiconductor layer 87 between n-ohmic electrodes 338 and 339 is a power line resistance Rg.

[0051] The island 305 is configured similarly to the island 304, and is provided with a start resistor Rs and a power line resistor Rg. The islands 306 and 307 are configured similarly to the island 303, and are provided with current limiting resistors R1 and R2.

[0052] An n-ohmic electrode 338 is provided on the exposed n-type semiconductor layer 85 of the island 300. On the back surface of the n-type semiconductor substrate 80, a back surface electrode 79 is provided.

[0053] Next, the connections will be described. In Fig. 3(a), the wiring used for the connections (power supply line 71, shift signal lines 72-1 and 72-2, and voltage supply line 74) are shown as straight lines. A p-ohmic electrode 321 which is an anode A electrode of the light-emission control thyristor S(1) of the island 301 is connected to a voltage supply line 74 to which a light-emission voltage VLD is supplied. An n-ohmic electrode 331 which is an n-gate Gn electrode of the light-emission control thyristor S(1) of the island 301 is connected to an n-ohmic electrode 332 which is a collector Cs electrode of the coupling transistor Q(1) of the island 302. The n-ohmic electrode 332 is connected to an n-ohmic electrode 336 of a current limiting resistor RL provided in the island 303. An n-ohmic electrode 335 of the island 303 is connected to the voltage supply line 74.

[0054] A p-ohmic electrode 322 which is an anode A electrode of the shift thyristor T(1) of the island 302 is connected to a shift signal line 72-1. The shift signal line 72-1 is connected to a φ1 terminal to which a shift signal p1 is supplied via a current limiting resistor R1 provided in the island 306. An n-ohmic electrode 333 which is an n-gate Gn electrode of the shift thyristor T(1) of the island 302 is connected to an n-ohmic electrode (without symbol) which is a connection point between the power supply line resistor Rg and the start resistor Rs provided in the island 305. An n-ohmic electrode 334 which is a collector Cf electrode of the coupling transistor Q(1) of the island 302 is connected to one n-ohmic electrode 337 of the coupling resistor Rc of the island 304.

[0055] The other n-ohmic electrode 338 of the coupling resistance Rc of the island 304 is connected to an n-ohmic electrode (no symbol) which is the n-gate Gn electrode of the shift thyristor T(2). The other n-ohmic electrode 339 of the power supply line resistance Rg of the island 304 is connected to the power supply line 71 to which the power supply potential VGK is supplied.

[0056] One n-ohmic electrode (no symbol) of the start resistance Rs of the island 305 is connected to the shift signal line 72-2. The other n-ohmic electrode (no symbol) of the power supply line resistance Rg of the island 305 is connected to the power supply line 71. The shift signal line 72-2 is connected to a φ2 terminal to which a shift signal p2 (φ2) is supplied via a current limiting resistance R2 provided in the island 307.

[0057] The shift signal line 72-1 is connected to the p-ohmic electrode which is the anode A electrode of the odd-numbered shift thyristors T, and the shift signal line 72-2 is connected to the p-ohmic electrode which is the anode A electrode of the even-numbered shift thyristors T.

[0058] The other shift thyristors T, coupling transistors Q, light-emission control thyristors S, and VCSELs are configured similarly to the shift thyristor T(1), coupling transistor Q(1), light-emission control thyristor S(1), and VCSEL(1).

[0059] The n-ohmic electrode 338 of the exposed n-type semiconductor layer 85 of the island 300 serves as a GND terminal to which the ground potential GND is supplied, and the rear surface electrode 79 on the rear surface of the n-type semiconductor substrate 80 serves as a Vdrv terminal to which the driver voltage Vdrv is supplied.

[0060] The shift thyristor T and the coupling transistor Q are provided on a laminated semiconductor layer (structure) equivalent to the layer in which the light-emitting control thyristor S and the VCSEL are configured. However, an n-ohmic electrode 338 is provided on the n-type semiconductor layer 85 and set to the ground potential GND. On the other hand, a driver voltage Vdrv (≧0V) is supplied to the back electrode 79 on the back surface of the n-type semiconductor substrate 80. That is, the potential of the anode A of the p-type semiconductor layer 83 is always lower than the potential of the cathode K of the n-type semiconductor layer 81, and the pn junction formed by the n-type semiconductor layer 81, the active layer 82, and the p-type semiconductor layer 83 does not have a forward direction. Therefore, the semiconductor layer 85 included in the island 300 is insulated from the back electrode 79. In this way, the light-emitting section 11 and the shift section 12 are electrically separated from each other, and the light-emitting current supplied to the VCSEL is turned on / off on the ground potential side (ground side).

[0061] As described above, the light emitting device 10 is provided on a semiconductor substrate 80 made of a single semiconductor.

[0062] FIG. 4 is a timing chart for operating the light source device 1 to which the first embodiment is applied. The horizontal axis represents time, which progresses in alphabetical order from time a to time r. Note that times c1 to c6 are provided between time c and time d, and times q1 to q6 are provided between time q and time r. FIG. 4 shows changes over time in the shift signals p1, p2 and the light-emission signal pI, and indicates the numbers of the shift thyristor T, light-emission control thyristor S, and VCSEL that are turned on. Note that the light-emission control thyristor S and VCSEL are indicated as S / VCSEL.

[0063] Here, in the light emitting device 10 shown in Fig. 1, VCSEL(1) and VCSEL(6) are caused to emit light. After VCSEL(1) is caused to emit light from the initial state, the light emitting device 10 is returned to the initial state, and then VCSEL(6) is caused to emit light. In other words, VCSEL(1) and VCSEL(6) are caused to emit light. In this manner, the VCSELs can be arbitrarily selected to emit light. In other words, the VCSELs can be caused to emit light randomly.

[0064] As described in FIG. 2, the VCSEL (1) emits light by turning on the shift thyristor T (1). The VCSEL (6) emits light by turning on the shift thyristor T (6). The VCSEL (1) emits light intermittently at time b, time c1, time c2, time c3, time c4, time c5, and time c6. The VCSEL (6) emits light intermittently at time p, time q1, time q2, time q3, time q4, time q5, and time q6. Each intermittent emission is referred to as an emission pulse. The interval between the emission pulses (for example, the period from time c when the emission pulse is extinguished to time c1 when the next emission pulse is emitted) is the same between the emission pulses. Furthermore, the pulse width of the emission pulse (for example, the period from time b when the emission pulse is emitted to time c when the emission pulse is extinguished) is the same between the emission pulses. By emitting light intermittently in this manner, it becomes easier to maintain the light-emitting control thyristor S in a state in which it can emit light, and once the shift thyristor T has been put in a state in which it can emit light, it becomes easier to cause it to emit light again regardless of whether the shift thyristor T is on or not. The pulse width of the light-emitting pulse is sometimes referred to as the light-emitting pulse width, and the interval between the light-emitting pulses is sometimes referred to as the light-emitting pulse interval. Note that as long as light is emitted intermittently, the pulse width and pulse interval of each light-emitting pulse may be made different. The pulse width and pulse interval of each light-emitting pulse do not have to be the same, but it is easier to control if they are the same. Note that if the light-emitting pulse interval is made longer than the period in which it is possible to re-emit light, it will become impossible to re-emit light, so the light-emitting pulse interval is set so that the light-emitting pulse comes again while it is possible to re-emit light.

[0065] The timing chart of FIG. 4 will be described in detail with reference to FIG. Before time a, the state is the initial state. The initial state is a state in which the power supply line 71 is set to the power supply potential VGK (5V), the ground line 73 is set to the ground potential GND (0V), the shift signals p1 (φ1) and p2 (φ2) are "L" (0V), the driver Drv is off, and the driver voltage Vdrv is not supplied to the driver voltage line 75. At this time, the shift thyristor T(1) is in a state in which it can transition to the on state.

[0066] At time a, when the shift signal p1 transitions from "L" (0 V) to "H" (5 V), the shift thyristor T(1) turns on and transitions from the OFF state to the ON state. Then, a forward bias is applied between the anode An and gate Gn of the light-emission control thyristor S(1), and the VCSEL(1) enters a state in which it can emit light. At time b, the light-emitting signal pI transitions from "L" (0 V) to "H" (5 V). The driver Drv changes from off to on, and the driver voltage Vdrv becomes the ground potential GND (0 V). This turns on the light-emitting control thyristor S(1), and a light-emitting voltage VLD (5 V) is applied between the anode A of the light-emitting control thyristor S(1) and the cathode K of the VCSEL(1). This causes a current to flow through the light-emitting control thyristor S(1) and VCSEL(1), which are connected in series, and the VCSEL(1) emits light.

[0067] At time c, when the shift signal p1 transitions from "H" (5V) to "L" (0V), the shift thyristor T(1) turns off and transitions from the on state to the off state. Furthermore, at time c, when the light emission signal pI transitions from “H” (5 V) to “L” (0 V), no current flows between the anode A of the light emission control thyristor S(1) and the cathode K of the VCSEL(1), and the VCSEL(1) stops emitting light (becomes quenched). After that, between time c and time d, the light emission signal pI is changed four times, from “L” (0 V) to “H” (5 V) and from “H” (5 V) to “L” (0 V). This causes the VCSEL(1) to emit light four times.

[0068] Between time c and time d, the shift signal p1 (φ1) is “L” (0 V), the shift thyristor T(1) is in the off state, and no current flows through the shift thyristor T(1) and the coupling transistor Q(1). The same is true for the other shift thyristors T. Therefore, power consumption in the shift section 12 (see FIG. 1) is suppressed. In other words, when it is not necessary to maintain the on signal from the coupling transistor Q(1), the on signal is not maintained.

[0069] At time d, the initial state is reached. At this time, the shift thyristor T(1) is in a state in which it can transition to the ON state.

[0070] At time e, when the shift signal p1 transitions from "L" (0V) to "H" (5V), the shift thyristor T(1) turns on and transitions from the OFF state to the ON state, similar to the time a. At time f, when the shift signal p2 transitions from "L" (0V) to "H" (5V), the shift thyristor T(2) is turned on.

[0071] At time g, when the shift signal p1 transitions from "H" (5V) to "L" (0V), the shift thyristor T(1) is turned off. In this order, at time h, the shift thyristor T(3) is turned on, and at time i, the shift thyristor T(2) is turned off. Furthermore, at time j, the shift thyristor T(4) is turned on, and at time k, the shift thyristor T(3) is turned off. At time l, the shift thyristor T(5) is turned on, and at time m, the shift thyristor T(4) is turned off. At time n, the shift thyristor T(6) is turned on, and at time o, the shift thyristor T(5) is turned off. At this time, a forward bias is applied between the anode An and gate Gn of the light-emission control thyristor S(6), and the VCSEL(6) is able to emit light.

[0072] At time p, the light emission signal pI transitions from "L" (0 V) to "H" (5 V). The driver Drv turns from off to on, and the driver voltage Vdrv becomes the ground potential GND (0 V). Then, just like at time b, the VCSEL (6) emits light.

[0073] At time q, when the shift signal p2 transitions from "H" (5V) to "L" (0V), the shift thyristor T(6) is turned off. Furthermore, at time q, when the light emission signal pI transitions from "H" (5 V) to "L" (0 V), the VCSEL (6) stops emitting light (becomes quenched). After that, between time q and time r, the light emission signal pI is changed four times, from “L” (0 V) to “H” (5 V) and from “H” (5 V) to “L” (0 V), causing the VCSEL (6) to emit light four times.

[0074] Between time q and time r, the shift signal p2 (φ2) is “L” (0 V), the shift thyristor T(6) is in the off state, and no current flows through the shift thyristor T(6) and the coupling transistor Q(6). The same is true for the other shift thyristors T and the coupling transistors Q. Therefore, power consumption in the shift section 12 (see FIG. 1) is suppressed. In other words, when it is not necessary to maintain the on signal from the coupling transistor Q(6), the on signal is not maintained.

[0075] As described above, the shift section 12 turns on the shift thyristor T located upstream of the two adjacent shift thyristors T, then turns on the shift thyristor T located downstream of the shift, and then turns off the shift thyristor T located upstream of the shift. In this way, in the shift section 12, the on state is shifted by the shift operation of the shift thyristors T by shift signals (shift signal p1 and shift signal p2) with a phase difference of 180 degrees, during which two adjacent shift thyristors T are simultaneously turned on (for example, from time f to time g).

[0076] 5 is a timing chart for operating the light source device 1 to which the first embodiment is not applied. This timing chart is referred to as a conventional example. The light emitting device 10 is the same, and the horizontal axis of FIG. 5 is the same as that of FIG. 4.

[0077] In the conventional example shown in FIG. 5, the shift thyristor T(1) is maintained in the on state during the period from time c to time d when the VCSEL(1) intermittently emits light. Similarly, the shift thyristor T(6) is maintained in the on state during the period from time q to time r when the VCSEL(6) intermittently emits light. During these periods, a current that maintains the on state continues to flow through the shift thyristor T(1) or the shift thyristor T(6). Therefore, the conventional example consumes more power than the operation of the light source device 1 shown in the timing chart to which the first embodiment is applied shown in FIG.

[0078] Next, the intermittent emission of light from the VCSEL during the period in which the shift thyristor T is in the OFF state (for example, the period from time c to time d in FIG. 4) will be described.

[0079] FIG. 6 is a diagram showing the voltage at the light-emission control thyristor S(1) and the light-emission current of the VCSEL(1) in a series connection of the light-emission control thyristor S(1) and the VCSEL(1). FIG. 6(a) is a set timing chart, and FIG. 6(b) is the voltage at the light-emission control thyristor S(1) and the light-emission current of the VCSEL(1). FIG. 6(a) is a part of the timing chart shown in FIG. 4 starting from time a. Note that between time c and time d (see FIG. 4), times s to y are added in alphabetical order. In FIG. 6(b), the horizontal axis is time (ns), and the left vertical axis is the voltages (V) of the p-gate Gp, n-gate Gn, and cathode K of the light-emission control thyristor S(1). The right vertical axis is the light-emission current (mA) of the VCSEL(1).

[0080] The timing chart set in FIG. 6(a) will be explained. At time a, the shift signal p1 is shifted from "L" (0V) to "H" (5V) to turn on the shift thyristor T(1). At time b, the light-emitting signal pI is shifted from "L" (0V) to "H" (5V) to make the VCSEL(1) emit light. This time is set to 100 ns on the time axis of FIG. 6(b). Then, at time c, 10 ns after time b, the shift signal p1 is shifted from "H" (5V) to "L" (0V) to turn off the shift thyristor T(1). At time s, 10 ns after time c, the light-emitting signal pI is shifted from "H" (5V) to "L" (0V) to turn off the VCSEL(1). At time t, 100 ns after time s, the light-emitting signal pI is shifted again from "L" (0V) to "H" (5V) to make the VCSEL(1) emit light again. After this, the light emission signal pI is repeated from time b to time t. That is, the VCSEL (1) emits light for 20 ns from time b, which is 100 ns, then goes dark, pauses for 100 ns, and then emits light again for 20 ns. Then, the light emission is repeated at the same time interval. Here, the period from time b to time s is the light emission pulse, the period from time b to time s is the width of the light emission pulse, and the period from time s to time t is the pulse interval of the light emission pulse. The same applies to other cases. The pulse interval of the light emission pulse may be referred to as the light emission interval.

[0081] Figure 6(b) shows the results of a simulation in which the light emission current limiting resistor RI in Figure 1 is 100Ω, the power supply potential VGK supplied by the power supply VS1 and the light emission voltage VLD supplied by the power supply VS2 are both 5V, the on-resistance Ron of the driver Drv is 1Ω, and the off-resistance Roff is 1MΩ. The p-gate Gp is ​​not extracted, but Figure 6(b) shows the voltage of the p-gate Gp.

[0082] FIG. 7 shows an equivalent circuit of the light-emission control thyristor S(1) and the VCSEL(1). FIG. 7(a) shows the equivalent circuit, and FIG. 7(b) shows the parasitic capacitance of the semiconductor layers and the pn junction. FIG. 7(b) shows an n-type semiconductor layer 81 constituting the cathode K and a p-type semiconductor layer 83 constituting the anode A in the VCSEL(1), and an n-type semiconductor layer 85 constituting the cathode K, a p-type semiconductor layer 86 constituting the p-gate Gp, an n-type semiconductor layer 87 constituting the n-gate Gn, and a p-type semiconductor layer 88 constituting the anode A in the light-emission control thyristor S (see FIG. 3(b)). The active layer 82 and the tunnel junction layer 84 are omitted.

[0083] In the VCSEL(1), a parasitic capacitance Cv exists at the pn junction between the cathode K (n-type semiconductor layer 81) and the anode A (p-type semiconductor layer 83). In the light-emission control thyristor S(1), a parasitic capacitance Cgk exists at the pn junction between the cathode K (n-type semiconductor layer 85) and the p-gate Gp (p-type semiconductor layer 86), a parasitic capacitance Cgg exists at the pn junction between the p-gate Gp (p-type semiconductor layer 86) and the n-gate Gn (n-type semiconductor layer 87), and a parasitic capacitance Cag exists at the pn junction between the n-gate Gn (n-type semiconductor layer 87) and the anode A (p-type semiconductor layer 88). Note that a tunnel junction layer 84 exists between the anode A (p-type semiconductor layer 83) of the VCSEL(1) and the cathode K (n-type semiconductor layer 85) of the light-emission control thyristor S(1), and these have the same potential. Therefore, no parasitic capacitance occurs between the anode A (p-type semiconductor layer 83) of the VCSEL and the cathode K (n-type semiconductor layer 85) of the light-emission control thyristor S(1).

[0084] The timing chart of FIG. 6(a) will be described with reference to FIGS. 7(a) and 7(b). At time a, when the shift thyristor T(1) is turned on, the collector Cs of the coupling transistor Q(1) starts to draw current from the n-gate Gn of the light-emission control thyristor S. Here, since the light-emission voltage VLD (voltage supply line 74) is 5V, the voltage of the anode A of the light-emission control thyristor S(1) is 5V. Therefore, a forward bias is applied between the anode A and the n-gate Gn of the light-emission control thyristor S(1), and the voltage of the n-gate Gn becomes 3.5V, which is the voltage of the anode A minus the forward voltage Vd (1.5V). The voltage of the p-gate Gp becomes 4.7V, which is the voltage of the anode A minus the saturation voltage Vc (0.3V). In addition, the voltage of the cathode K becomes 1.7V, which is lower than the voltage of the p-gate Gp by 2×Vd, taking into account the forward voltage Vd (1.5V) of the VCSEL(1). This is the state immediately before time b in FIG. 6(a), and the state immediately before 100 ns on the time axis in FIG. 6(b).

[0085] At time b, when the light emission signal pI changes from "L" (0V) to "H" (5V) and the driver Drv is turned on, the driver voltage line 75 to which the cathode K of the VCSEL is connected becomes the ground potential GND via the driver Drv and the light emission current limiting resistor RI. This turns on the light emission control thyristor S(1) and the VCSEL(1) emits light. In the simulation results shown in Figure 6(b), the light emission current flows, causing the voltages of the n gate Gn, p gate Gp, and cathode K to be approximately 3.2V, 4.7V, and 1.7V, respectively.

[0086] Even if the shift signal p1 transitions from "H" (5V) to "L" (0V) at time c, the voltage of the n gate Gn does not change because the VCSEL(1) is emitting light.

[0087] At time s, when the light emission signal pI changes from "H" (5V) to "L" (0V) and the driver Drv turns off, the driver Drv switches from an on-resistance Ron of 1Ω to an off-resistance Roff of 1MΩ. If the off-resistance Roff is large, the current between the anode A of the light emission control thyristor S(1) and the cathode K of the VCSEL(1) becomes equal to or less than the holding current, the light emission control thyristor S turns off and transitions from the on state to the off state, and the VCSEL(1) goes out of light. At this time, since the n gate Gn is connected to the voltage supply line 74 of the light emission voltage VLD (5V) via the current limiting resistor RL, the voltage of the n gate Gn rises toward the light emission voltage VLD (5V). That is, the parasitic capacitance Cag (capacity is Cag) discharges via the current limiting resistor RL (resistance value is RL) with a time constant of RL x Cag. On the other hand, the charges stored in the parasitic capacitances Cgg, Cgk, and Cv cannot move, so the voltages of the p gate Gp and cathode K rise by the amount that the voltage of the n gate Gn rises. In Figure 6(b), the voltages of the n gate Gn, p gate Gp, and cathode K are about 5V, 6V, and 3V.

[0088] At time t, when the light-emitting signal pI changes from "L" (0 V) to "H" (5 V) and the driver Drv turns on again, the driver voltage line 75 to which the cathode K of VCSEL(1) is connected suddenly changes toward the ground potential GND (0 V). As a result, a displacement current flows through the parasitic capacitances Cag, Cgg, and Cgk, and with this as the threshold current, the light-emitting control thyristor S(1) turns on, causing the VCSEL(1) to emit light. At time u, when the light-emission signal pI changes from "H" (5 V) to "L" (0 V) and the driver Drv turns off, the light-emission control thyristor S turns off in the same manner as at time s, and the VCSEL (1) ceases to emit light. By repeating the process from time s to time t, the VCSEL (1) emits light intermittently multiple times.

[0089] The off state (OFF) of the light-emission control thyristor S, or turning off the light-emission control thyristor S, means that a signal that maintains the light-emission control thyristor S in the on state is not being supplied, and does not mean that a signal that turns off the light-emission control thyristor S is being supplied. As described above, when the collector Cs of the coupling transistor Q is turned off, a signal that makes the light-emission control thyristor S in a state in which it can be switched to the on state is no longer supplied to the n-gate Gn of the light-emission control thyristor S. However, the light-emission control thyristor S maintains a state in which it can be switched to the on state for a while due to the accumulated charge.

[0090] In FIG. 6(a), at time c, the shift signal p1 is shifted from "H" (5V) to "L" (0V) to turn off the shift thyristor T(1), and then at time s, the light-emission signal pI is shifted from "H" (5V) to "L" (0V) to extinguish the VCSEL(1). In this manner, the cathode K of the light-emission control thyristor S(1) is set to a high voltage, ensuring that the VCSEL(1) emits light again. In FIG. 6(a), the VCSEL(1) emits light once before the shift thyristor T(1) is turned off, but it may emit light multiple times.

[0091] Fig. 8 is a diagram showing the voltage of the cathode K of the light-emission control thyristor S(1) and the light-emission current of the VCSEL(1) when the off-resistance Roff of the driver Drv is changed. Fig. 8 shows the results of a simulation in which the off-resistance Roff is set to 50 kΩ, 100 kΩ, 200 kΩ, 500 kΩ, and 1 MΩ. The timing chart set is that shown in Fig. 6(a).

[0092] The smaller the off-resistance Roff is, the greater the drop in voltage at the cathode K of the light-emission control thyristor S(1) after the VCSEL(1) is turned off. When the off-resistance Roff is set to 100 kΩ, 200 kΩ, 500 kΩ, and 1 MΩ, the light-emission control thyristor S(1) in FIG. 6(a) emits light again at time t after the light-emission control thyristor S(1) is turned off, that is, after the shift unit 12 is turned off. In other words, even after the shift unit 12 is turned off, the VCSEL(1) can be made to emit light intermittently multiple times (re-emission is possible).

[0093] On the other hand, when the off-resistance Roff is set to 50 kΩ, no light is emitted at time t after the light-emission control thyristor S(1) in Fig. 6(a) is turned off, that is, after the shift unit 12 is turned off. This is because even if the driver Drv is turned on, the light-emission control thyristor S(1) does not turn on because the voltage change in the driver voltage line 75 to which the cathode K of the VCSEL(1) is connected is small and the displacement current is small.

[0094] In the simulation, the voltage of the cathode K at which the light-emission control thyristor S(1) does not turn on was less than 0.9 V. When the light-emission control thyristor S does not turn on, the VCSEL(1) does not emit light again (it becomes unable to emit light again). The voltage of the cathode K is determined by the parasitic capacitance of each pn junction (parasitic capacitances Cgg, Cgk, and Cv in FIG. 7(b)), the threshold current of the light-emission control thyristor S, and the speed dV / dt of voltage change of the driver voltage line 75. The light-emission control thyristor S is an example of a capacitance unit, and the light-emission control thyristor S and the VCSEL connected in series are an example of a light-emitting element having a capacitance unit.

[0095] In order to make the VCSEL emit light intermittently after the shift unit 12 is turned off, it is preferable that the off-resistance Roff of the driver Drv is large. As described above, once a VCSEL is turned on, it becomes unable to emit light again when the voltage of the cathode K of the light-emission control thyristor S becomes less than 0.9 V. As shown in FIG. 8, the voltage of the cathode K of the light-emission control thyristor S decreases less as the off-resistance Roff increases. However, if the off-resistance Roff is too large, the period during which the VCSEL once turned on can emit light again becomes longer. In other words, in order to make another VCSEL emit light after the VCSEL once turned on becomes unable to emit light again, if the period during which the VCSEL once turned on can emit light again is long, the period (pause period) until the other VCSEL is made to emit light is set long.

[0096] 9 is another diagram showing the voltage of the cathode K of the light-emission control thyristor S(1) and the light-emission current of the VCSEL(1) when the off-resistance Roff of the driver Drv is changed. FIG. 9(a) shows the entire light-emission current, and (b) is an enlarged view of the light-emission current in FIG. 9(a). FIGS. 9(a) and (b) show the results of a simulation in which the off-resistance Roff is set to 50 kΩ and 30 kΩ. The set timing chart is that of FIG. 6(a), and the off-resistance Roff of 50 kΩ is the same as the off-resistance Roff of 50 kΩ in FIG. 8.

[0097] If the off-resistance Roff is made small, after the driver Drv is turned off, the voltage of the cathode K of the light-emission control thyristor S quickly approaches 0 V. However, if the off-resistance Roff is made too small, a current equal to or greater than the holding current continues to flow through the light-emission control thyristor S even after the driver Drv is turned off, and the light-emission control thyristor S(1) does not turn off.

[0098] As shown in FIG. 9(a), when the off resistance Roff is 50 kΩ, the second light emission does not occur at time t. However, when the off resistance Roff is 30 kΩ, light emission occurs again at time t. Then, light emission occurs again at the following times v and x. As shown in FIG. 9(b), when the light emission current is enlarged, when the off resistance Roff is 50 kΩ, the light emission current decreases during the period when the driver Drv is off, and becomes almost 0 A after time u. On the other hand, when the off resistance Roff is 30 kΩ, the light emission current flows at 0.07 mA during the period when the driver Drv is off. In other words, a current equal to or greater than the holding current continues to flow through the light-emission control thyristor S(1), and the light-emission control thyristor S(1) maintains the on state.

[0099] From the above, the off-resistance Roff of the driver Drv must be set so that the VCSEL is maintained in a state in which it can re-emit light during the period in which the VCSEL can re-emit light, and the period (pause period) until re-emission is no longer possible is not too long. Furthermore, the off-resistance Roff of the driver Drv must be set so that a current equal to or greater than the holding current does not flow through the light-emission control thyristor S during the period in which the driver Drv is off. In other words, the off-resistance Roff of the driver Drv is set according to a predetermined period until re-emission is no longer possible (pause period).

[0100] As described above, the period during which the VCSEL can re-emit light and the period until re-emission is no longer possible (pause period) are determined by the off-resistance Roff of the driver Drv. However, there are cases where it is desired to set the period during which re-emission is possible longer than the period determined by the off-resistance Roff of the driver Drv.

[0101] FIG. 10 is a timing chart for explaining a method for setting a longer period during which the VCSEL can emit light again. FIG. 10 is the same as the timing chart shown in FIG. 4. In the timing chart of FIG. 4, light emission pulses are provided at times c1, c2, c4, c5, q1, q2, q4, and q5. However, in the timing chart of FIG. 10, the light emission signal pI is made smaller at times c1, c2, c4, c5, q1, q2, q4, and q5 so that the current flowing through the VCSEL is smaller than that in FIG. 4. In this way, the voltage of the cathode K of the light emission control thyristor S rises in the same way as when the VCSEL is made to emit light, while suppressing the amount of light emitted by the VCSEL, and the state becomes one in which light emission can be made again. The light emission pulse in this case is referred to as a sustain pulse. That is, the pulses at time b, time c3, time c6, time p, time q3, and time q6 are emission pulses, but the pulses at time c1, time c2, time c4, time c5, time q1, time q2, time q4, and time q5 are hold pulses. If the period during which VCSEL(1) can re-emit light is from time c to time c1 when the hold pulse of FIG. 4 is not used, when the hold pulse of FIG. 10 is used, the period during which VCSEL(1) can re-emit light is from time c to time c3, which is three times longer. In FIG. 10, two hold pulses are provided between emission pulses, but more than two hold pulses may be provided. By providing a hold pulse, the period during which VCSEL can re-emit light can be extended to any period.

[0102] In FIG. 10, the interval between the hold pulses and the interval between the hold pulse and the light emission pulse (when not distinguished, they are referred to as pulse intervals) for VCSEL(1) and VCSEL(6) are the same. The width of the light emission pulse and the hold pulse are also the same. However, the pulse interval may be set so that the period during which light emission is possible again continues. Similarly, the width of the hold pulse may be set so that the period during which light emission is possible again continues. The amount of light emitted by the VCSEL due to the hold pulse should be smaller than that of the light emission pulse, and the speed of voltage change dV / dt should be large enough to allow the light emission control thyristor S to be in a state in which light emission is possible. If this condition is satisfied, a state in which light is not actually emitted is also possible. If light emission due to the hold pulse is not desired, the current value may be selected so that it is equal to or less than the threshold current of the VCSEL. The hold pulse may be inserted before the first light emission pulse. In that case, it is even better to turn off the shift thyristor T after the first light emission pulse.

[0103] [Second embodiment] In the first embodiment, the driver Drv has one off resistance Roff. In the second embodiment, the value of the off-resistance Roff of the driver Drv is switchable.

[0104] FIG. 11 is a diagram for explaining a light source device 2 to which the second embodiment is applied. The control unit 50 of the light source device 2 includes two drivers Drv1 and Drv2 instead of the driver Drv in the first embodiment. The driver Drv1 has an on-resistance Ron1 and an off-resistance Roff1. The driver Drv2 has an on-resistance Ron2 and an off-resistance Roff2. The on-resistance Ron1 and the on-resistance Ron2 may be the same or different. On the other hand, the off-resistance Roff1 and the off-resistance Roff2 are different (for example, Roff1>Roff2). The drivers Drv1 and Drv2 are connected to a light emission current limiting resistance RI via a switch SW. The driver Drv1 and the driver Drv2 are switched by switching the switch. The switch may be an NMOS transistor or the like having a resistance value larger than both the off-resistance Roff1 and the off-resistance Roff2.

[0105] In the driver Drv2 with a small off-resistance Roff2, the voltage of the cathode K of the light-emission control thyristor S decreases faster than in the driver Drv1 with a large off-resistance Roff1. This shortens the period during which the VCSEL emits light intermittently. This shortens the period (pause period) until light cannot be emitted again. Therefore, the period during which light is emitted intermittently may be set by switching between the driver Drv1 and the driver Drv2. The pause period may also be set by switching between the driver Drv1 and the driver Drv2.

[0106] As a method for changing the off-resistance Roff value, multiple resistors with different resistance values, each of which has a smaller resistance value than the resistance of the NMOS transistor when it is off, may be connected in parallel between the source and drain of the NMOS transistor via a switch. By switching the switch, the off-resistance Roff value of the driver Drv is changed, making it possible to select the period during which re-emission is possible.

[0107] [Third embodiment] In the light source device 1 to which the first embodiment is applied and the light source device 2 to which the second embodiment is applied, the period (pause period) until re-emission becomes impossible is determined by the off resistance Roff of the driver Drv. In the light source device 3 to which the third embodiment is applied, an erase pulse is provided to erase the state in which re-emission is not possible in order to set the pause period to be short. When an erase pulse is provided, erroneous emission of the VCSEL is suppressed in cases where the light-emission control thyristor is likely to be kept on due to intermittent multiple light emission, or where the light-emission control thyristor has been turned on due to a malfunction. Furthermore, if an erase pulse is not provided, in order to suppress re-emission of the VCSEL that has previously emitted light, it is necessary to wait for a period (pause period) until the light-emission control thyristor S connected to this VCSEL is depleted of charge. This delays the timing of emitting another VCSEL, making it difficult to drive at high speed when switching between VCSELs to be emitted one after another. Therefore, by providing an erase pulse, the pause period is shortened, making it easier to drive at high speed.

[0108] FIG. 12 is a diagram for explaining a light source device 3 to which the third embodiment is applied. The control unit 50 of the light source device 3 further includes a driver Drv3 and an erase current limiting resistor RJ in addition to the control unit 50 of the light source device 1 shown in FIG. 1. The driver Drv3 is turned on / off by an erase signal pJ applied to the gate, for example, using an NMOS transistor as a driver element. The source of the NMOS transistor of the driver Drv3 is grounded, and the drain is connected to the Vdrv terminal via the erase current limiting resistor RJ. The erase signal pJ is a signal having a ground potential GND ("L" (0V)) and a power supply potential VGK ("H" (5V)). Here, the driver Drv3 is turned off when the erase signal pJ is "L" (0V), and turned on when the erase signal pJ is "H" (5V). In other words, the period when the erase signal pJ is "H" (5V) is an erase pulse, and this period is the pulse width of the erase pulse. The driver Drv is an example of a first driver, and the driver Drv3 is an example of a second driver.

[0109] The driver Drv3 has an on-resistance Ron close to 0Ω and an off-resistance Roff close to infinity. The erase current limiting resistor RJ is set to a value that, when the driver Drv3 is turned on, reduces the voltage of the cathode K of the light-emission control thyristor S during a preset erase period (pulse width of the erase pulse) and renders the VCSEL unable to emit light again. For example, the off resistance Roff shown in FIG. 8(b) is 50 kΩ. As described above, the erase current limiting resistor RJ is set to a value that prevents a current greater than the holding current from flowing through the light-emission control thyristor S.

[0110] Fig. 13 is a timing chart for explaining the timing of providing an erase pulse. As an example of erasing the effect of turning on the light-emission control thyristor S(1) / VCSEL(1), Fig. 13 cuts out the vicinity of time n to time r in the timing chart shown in Fig. 4 and adds an erase pulse. For this reason, times aa and ab are added between times o and p.

[0111] The erase pulse should be placed after the end of the series of VCSEL light emission (time d in FIG. 4) and before the next VCSEL to be emitted (time p in FIG. 4). In FIG. 12, it is assumed that VCSEL (6) is to be emitted. At time n, the shift signal p2 changes from "L" (0V) to "H" (5V), turning on the shift thyristor T(6) and changing from the off state to the on state. At time o, the shift signal p1 changes from "H" (5V) to "L" (0V), turning off the shift thyristor T(5) and changing from the on state to the off state. At time aa, the erase signal pJ is shifted from "L" (0V) to "H" (5V) to turn on the driver Drv3. Then, in the period until time ab, the VCSEL is placed in a state in which it cannot emit light again. Time aa is the timing when only the shift thyristor T(6), which sets the VCSEL(6) to emit light, is in the on state.

[0112] At time ab, the erase signal pJ transitions from "H" (5V) to "L" (0V) to turn off the driver Drv3. Then, at time b after time ab, the light emission signal pI transitions from "L" (0V) to "H" (5V) to cause the VCSEL (6) to emit light. The period from time aa to time ab during which the erase signal pJ is "H" (5V) is the erase pulse. Here, the VCSEL (6) is described as emitting light, but other VCSELs may be used.

[0113] More preferably, the erase pulse is provided after the time when only the shift thyristor T that sets the VCSEL to be emitted is turned on (time o in FIG. 12) and before the VCSEL to be emitted is emitted (time p in FIG. 12). This is because, when the on state is shifted in the shift section 12, the erase pulse resets (initializes) the effect of lowering the voltage of the n-gate Gn of the light-emission control thyristor S other than the set VCSEL and the fluctuation in the voltage of the n-gate Gn of the light-emission control thyristor S due to noise during shifting. Therefore, the erase pulse may be used not only to disable the re-emission of a previously emitted VCSEL, but also before the first emission of a VCSEL in order to disable emission of any VCSEL in the light-emitting device 10.

[0114] In addition, when the driver Drv is composed of an NMOS transistor, the erase pulse may be generated by connecting multiple resistors having different resistance values, each resistor having a smaller resistance value than the off resistance of the NMOS transistor, in parallel between the source and drain of the NMOS transistor, and one of the resistors may be used as the erase current limiting resistor RJ. The multiple resistors may be connected via a switch, and the erase pulse may be generated by switching the switch.

[0115] By making the pulse width of the erase pulse narrower than the pulse width of the light-emitting pulse and / or making the current value of the erase pulse smaller than the current value of the light-emitting pulse, light emission from the VCSEL due to the erase pulse is suppressed.

[0116] It is advisable to supply a pulse with a slow voltage change rate dV / dt to the driver voltage line 75 as the erase pulse. Even when the light-emitting control thyristor S is turned on and off, charge remains. The light-emitting voltage VLD is applied to the n-gate Gn by the current limiting resistor RL. Therefore, charge in the n-gate layer 87, which is the n-gate Gn, is likely to escape. On the other hand, charge is likely to remain in the p-gate layer 86, which is the p-gate Gn (see FIG. 3) (see FIG. 7(b)). The threshold voltage of the light-emitting control thyristor S changes depending on the amount of remaining charge. In this way, a pulse with a slow voltage change rate dV / dt may be supplied to the driver voltage line 75 to increase the threshold voltage of the light-emitting control thyristor S, making it difficult to turn on the light-emitting control thyristor S.

[0117] Although the light emitting device 10 described above has a common cathode, it may have a common anode. In this case, an n-ohmic electrode is provided on the n-gate layer (n-type semiconductor layer 87), but a p-ohmic electrode may be provided on the p-gate layer (p-type semiconductor layer 86). Furthermore, in the shift section 12 of the light emitting device 10, the shift thyristors T are connected by the coupling transistors Q, but may be connected by diodes or resistors.

[0118] In the above embodiment, the light emitting device 10 including a plurality of light emitting elements that emit light at different timings has been described as an example. However, the above embodiment may be applied to a single light emitting element or a single light emitting element group in which a plurality of light emitting elements emit light simultaneously. Also, an example has been described in which the shift section 12 is the setting section, but instead of a shift section that performs a shift operation, the setting section may be configured to send a signal directly from the driver to the thyristor of the light-emitting element.

[0119] (Measuring device 100) The light source devices 1, 2, and 3 shown in the first to third embodiments can be applied to a measurement device that measures a three-dimensional shape (hereinafter, referred to as a 3D shape) of a measurement object. The measurement device is a device that measures a 3D shape based on a so-called ToF (Time of Flight) method using the time of flight of light. The measurement device includes a light source device and a three-dimensional sensor (hereinafter, referred to as a 3D sensor). In the ToF method, the time from the timing when light is emitted from the light source device to the timing when the light is reflected by the measurement object and received by the 3D sensor is measured. Then, the distance to the measurement object is calculated from the time acquired from the three-dimensional sensor, and the 3D shape of the measurement object is specified. In addition, measuring a three-dimensional shape may be referred to as three-dimensional measurement, 3D measurement, or 3D sensing. The three-dimensional sensor is an example of a light receiving unit.

[0120] Such a measuring device is applied to recognize a measurement target from a specified 3D shape. For example, it is mounted on a portable information processing device and used to recognize the face of a user who is trying to access the device. In other words, the 3D shape of the face of the user who has accessed the device is acquired, and it is determined whether the user is permitted to access the device. Only when the user is recognized as being permitted to access the device, is the device (portable information processing device) permitted to be used. This measuring device is also applicable to cases where the 3D shape of an object is continuously measured, such as in augmented reality (AR).

[0121] Such a measuring device can be applied to information processing devices other than portable information processing devices, such as personal computers (PCs).

[0122] FIG. 14 is a block diagram for explaining the configuration of the measurement device 100. The measurement device 100 includes light source devices 1, 2, and 3 each including a light emitting device 10 and a control unit 50, and a 3D sensor 5. The light source devices 1, 2, and 3 emit light toward the object to be measured. The 3D sensor 5 acquires light (reflected light) reflected by the object to be measured. The 3D sensor 5 outputs information (distance information) about the distance to the object to be measured based on the time from emission to reception of the reflected light measured by the ToF method. The measurement device 100 may include a measurement control unit 200. The measurement control unit 200 is configured as a computer including a CPU, a ROM, a RAM, and the like, and identifies the three-dimensional shape of the object to be measured based on the distance information acquired from the 3D sensor 5.

[0123] The present invention may be understood as follows. In the light-emitting device, the shift section is configured with transfer elements to which the ON state is transferred in the order of the arrangement. In this way, the shift section is easier to configure than when the ON state is not transferred. In the light emitting device, when the thyristor in the shift section is turned on, the light emitting element is brought into a state in which it can emit light by the thyristor function. In this way, the control of the shift section and the control of the light emitting section are separated. The light emitting device is characterized in that the light emitting element is composed of a surface light emitting element and a thyristor connected in series, which makes it easy to improve the light emitting characteristics. [Explanation of symbols]

[0124] 1, 2, 3...light source device, 5...3D sensor, 10...light emitting device, 11...light emitting section, 12...shift section, 12a...shift unit, 50...control section, 71...power supply line, 72, 72-1, 72-2...shift signal line, 73...ground line, 74...voltage supply line, 75...driver voltage line, 79...rear electrode, 100...measurement device, 200...measurement control section, Buf1, Buf2...buffer, Drv, Drv1, Drv2, Drv3...driver, GND...ground potential, p1, p2...shift signal, pI...light emission signal, pJ...erase signal, S...light emission control thyristor, T...shift thyristor, VCSEL...vertical cavity surface emitting laser, Vc...saturation voltage, Vd...forward voltage (diffusion potential), Vdrv...driver voltage, VGK...power supply potential, VLD...light emission voltage, VS1, VS2...power supply

Claims

1. a light emitting unit including a light emitting element having a thyristor; A setting unit that sets the light emitting unit as a light emitting element that emits light; After the light emitting element is switched to a state in which it can emit light, the ON setting from the setting unit is switched to OFF; A control unit that turns on / off a light-emitting current that causes the light-emitting element to emit light, causing the light-emitting element to emit light a plurality of times, The light emission interval when the light is emitted multiple times is set according to a predetermined period during which light emission can be resumed after the light emission current to the light emitting element is turned off in a state where no on setting is made from the setting unit. Light source device.

2. The light source device according to claim 1 , wherein the light emitting element is caused to emit light one or more times before the on setting from the setting unit is shifted to off.

3. the control unit includes a driver that turns on / off a light-emitting current on the ground side of a power source that supplies a light-emitting current to the light-emitting element, 2. The light source device according to claim 1, wherein an off-resistance of the driver is set in accordance with the period.

4. 4. The light source device according to claim 3, wherein the off-resistance of the driver is composed of a driver element and a resistor provided in parallel with the driver element.

5. 4. The light source device according to claim 3, wherein the off-resistance of the driver can be switched to a plurality of values.

6. 2 . The light source device according to claim 1 , wherein the control unit supplies a pulse having a smaller current value than the light emission current while the light emitting element is caused to emit light a plurality of times or before the light emitting element is caused to emit light.

7. The setting unit is a shift unit that performs a shift operation to set a light-emitting element to be emitted by the light-emitting unit, The control unit sets a shift signal to be supplied to the shift unit to a ground potential, thereby causing the shift unit to transition to an off state.

2. The light source device according to claim 1.

8. The control unit is 2. The light source device according to claim 1, further comprising: a clearing pulse for disabling the light emitting element from emitting light again, the clearing pulse being supplied to the light emitting portion.

9. The control unit is a first driver for turning on / off a light-emitting current on the ground side of a power supply that supplies the light-emitting element and a light-emitting current, and a second driver for supplying the erase pulse; The light source device according to claim 8, characterized in that the second driver has an on-resistance smaller than the off-resistance of the first driver, and is set to a value that disables re-emission by turning on when the first driver is off.

10. a light emitting unit including a plurality of light emitting elements each having a thyristor; a setting unit that sets a light emitting element to be emitted in the light emitting unit by being sequentially transferred to the on state and being turned on; The gate of the thyristor of the light-emitting element is connected to a voltage supply line that supplies a light-emitting current to the light-emitting element via a resistor. Light emitting device.

11. 11. The light emitting device according to claim 10, wherein the setting section is formed of a thyristor.

12. A substrate is provided. The light-emitting device according to claim 11, characterized in that the light-emitting element is stacked on the substrate in the order of a surface-emitting element and a thyristor, and the thyristor of the setting section is provided on a structure equivalent to the light-emitting element on the substrate.

13. 13. The light emitting device according to claim 12, wherein the surface light emitting element and the thyristor are electrically separated from each other.

14. A light source device according to any one of claims 1 to 9; a light receiving unit that receives light emitted from the light emitting unit of the light source device and reflected by an object to be measured; A measuring device comprising:

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