JP2021150422A - Driving device, light source, image projection device, and head-up display - Google Patents

Abstract

To provide a driving device, a light source, an image projection device, and a head-up display, capable of preventing a post card.SOLUTION: A driving device 1 making a semiconductor laser vibrate in a multi mode drive, contains a current control circuit 5 controlling a current flowing in the semiconductor laser. The current control circuit 5 performs a first control that the current is set to a threshold value or larger for vibrate the semiconductor laser, and a second control that the current is set to a predetermined value after the first control. The time when the current becomes the threshold value or larger in the first control is shorter than a pulse width.SELECTED DRAWING: Figure 1

Description

The present invention relates to a drive device for driving a semiconductor laser, a light source including the drive device, an image projection device, and a head-up display.

Today, light sources using semiconductor lasers have become widespread. Such a light source is configured to include a driving device for emitting a semiconductor laser.

By the way, in a semiconductor laser, even if a threshold current is input, it takes time to generate carriers having an oscillating concentration, so that light emission delay occurs. In particular, in the case of a high-power semiconductor laser that oscillates in multimode, the emission delay tends to be large because the threshold current is large. Therefore, in order to improve the light emission delay of the drive device, various techniques related to control have been developed.

Regarding this point, for example, Japanese Patent No. 4432459 (Patent Document 1) discloses a technique for controlling a drive current in two steps in order to increase the rising speed of light emission of a semiconductor laser.

However, in the prior art such as Patent Document 1, since a current having a value close to the threshold current is passed through the semiconductor laser at a time other than the timing of emitting light, an image is displayed by unintended light emission, that is, a so-called "postcard". "Appears.

Therefore, there has been a demand for a technique for preventing postcards while suppressing light emission delay.

The present invention has been made in view of the above problems in the prior art, and an object of the present invention is to provide a drive device, a light source, an image projection device, and a head-up display for preventing postcards.

That is, according to the present invention.
A drive device that drives a semiconductor laser that oscillates in multiple modes.
A control means for controlling the current flowing through the semiconductor laser is included.
The control means
The first control that sets the current to be equal to or higher than the threshold value at which the semiconductor laser oscillates,
After the first control, a second control is performed in which the current is set to a predetermined value with a predetermined pulse width.
In the first control, the time during which the current becomes equal to or higher than the threshold value is shorter than the pulse width.
A drive is provided.

According to the present invention, a drive device, a light source, an image projection device and a head-up display for preventing postcards can be provided.

The figure which shows an example of the drive current of the semiconductor laser and the amount of light in this embodiment. The figure which shows another example of the drive current of the semiconductor laser in this embodiment. The figure which shows the structure of the drive device of this embodiment. The figure which shows the example of the phase division and the phase selection by the drive device of this embodiment. The figure which shows the structure of the current control circuit in 1st Embodiment. The figure explaining the details of the bias circuit which comprises the current control circuit in 1st Embodiment. The figure which shows the control of the drive current of a laser diode in 1st Embodiment. The figure which shows the structure of the current control circuit in 2nd Embodiment. The figure which shows the control of the drive current of a laser diode in 2nd Embodiment. The figure which shows the example which generates the control signal in 2nd Embodiment. The schematic diagram of an example of an automobile equipped with a head-up display device. The schematic diagram of an example of a head-up display device. The schematic diagram explaining an example of the structure of a laser headlamp. The figure explaining the current light amount characteristic of a general semiconductor laser. The figure explaining the light emission delay in a general semiconductor laser.

As a premise for explaining the present invention, the light emitting characteristics of a general semiconductor laser will be described with reference to FIGS. 14 and 15.

First, FIG. 14 will be described. FIG. 14 is a diagram illustrating a current light amount characteristic of a general semiconductor laser. The horizontal axis represents the drive current I _op flowing through the semiconductor laser, and the vertical axis represents the amount of light of the semiconductor laser. The semiconductor laser oscillates at a threshold current _{I th.} As shown in FIG. 14, when a _{drive current equal to} or higher than the threshold current I th flows, the amount of light increases linearly as the drive current increases. For example, when the drive current becomes the target current I _T, the semiconductor laser emits light at a target light amount P _T.

On the other hand, as shown in FIG. 14, the semiconductor laser emits light with a minute amount of light even when the current is equal to or less than the threshold current. When a semiconductor laser that emits minute amounts of light with a low current as shown in FIG. 14 is used as a display device such as an image projection device, a postcard is generated. The generation of postcards is not preferable because it can give erroneous information to the user.

Next, FIG. 15 will be described. FIG. 15 is a diagram illustrating a light emission delay in a general semiconductor laser. FIG. 15A shows a change in the drive current with the passage of time, and shows an example in which a pulse current for driving the semiconductor laser is input for a time corresponding to one pixel section of the display device. The horizontal axis represents the time t, and the vertical axis represents the drive current I _op flowing through the semiconductor laser. Here, the one-pixel section refers to a time unit for driving a semiconductor laser for displaying an image for one pixel in a display device that scans the laser and displays an image. The value of one pixel section is not particularly limited, but as an example, the time may be on the order of several hundred MHz (about several nanoseconds). In the example of FIG. 15 (a), in the period from time t ₁ to time t _2, the target current I _T is an example flow as the drive current. The target current _IT is a value larger than the threshold current I _th.

FIG. 15B shows the amount of light of the semiconductor laser controlled by the drive current as shown in FIG. 15A. The horizontal axis represents the time t, and the vertical axis represents the light intensity P of the semiconductor laser. In such a case, although the threshold current I larger target current I _T than _th at time t ₁ is flowed to the semiconductor laser, as shown in FIG. 15 (b), the light amount of the semiconductor laser is delayed from time t ₁ A time when the target light amount is not reached after rising, that is, a light emission delay occurs. The light emission delay occurs because it takes time for the semiconductor laser to generate carriers having a concentration capable of oscillating even if a threshold current is input. In particular, a semiconductor laser that oscillates in a multi-mode takes a longer time to oscillate than a semiconductor laser that oscillates in a single mode.

Therefore, the present invention suppresses light emission delay and prevents postcards as described below. Hereinafter, the present invention will be described with reference to each embodiment, but the present invention is not limited to the embodiments described later. In each of the figures referred to below, the same reference numerals are used for common elements, and the description thereof will be omitted as appropriate. Further, in the following description, first, matters common to the first embodiment and the second embodiment will be described with reference to FIGS. 1 to 4.

FIG. 1 is a diagram showing an example of a driving current of a semiconductor laser and a light amount in the present embodiment. FIG. 1A shows an example of the passage of time of the drive current in this embodiment. In FIG. 1 (a), shall emit semiconductor laser in one pixel period from time t ₃ to t _4. In the present embodiment, in order to suppress the postcard, the drive current is gradually increased before the time corresponding to one pixel section. In the example of FIG. 1 (a), the driving current, the threshold current _{I th} at time _{t 1,} performs current value control for the I _{t 'between} the threshold current _{I th} and the target current _{I t} at time _{t 2.}
The value of I t _'is not limited to the embodiment, for example, it is an average of the threshold current I _th and the target current I _t. The current value before time t ₁ does not necessarily have to be 0, and may be any current value that can sufficiently suppress the generation of postcards.

Here, the time _{from time t 1} to t ₂ is preferably about several hundred ps (picoseconds) for one pixel section of about several hundred MHz. Similarly, the time from time t ₂ to t ₃ is preferably about several hundred ps. In this way, the postcard can be suppressed by passing a drive current equal to or larger than the threshold current for a sufficiently short time for one pixel section. In the example of FIG. 1A, the time _{from time t 2} to t _{3 is set to It',} and the current value is controlled to be increased in two steps. However, the control is not performed and the threshold current I _It may be possible to perform only the control of raising to th.

FIG. 1B shows an example of the amount of light in the current control of the present embodiment. As shown in FIG. 1 (b), by performing the current control as shown in FIG. 1 (a), the semiconductor laser has a target light amount _{PT in} the time from time t _{3 to time t 4 corresponding to one pixel section.} Can be made to emit light with.

Further, the control of the drive current is not limited to that shown in FIG. 1A, and may be controlled as shown in FIG. 2, for example. FIG. 2 is a diagram showing another example of the drive current of the semiconductor laser in the present embodiment.

Control of the driving current in the present embodiment, for example, as shown in FIG. 2 (a), before the time corresponding to one pixel period (time _{t 4} ~ time _{t 5),} the threshold current _{I th} at time _{t 1} and then, the current value I _{t 'between} the threshold current _{I th} and the target current _{I t} at time _{t 2, the} may be controlled to the target current _{I T} at time _{t 3.} Although the embodiment is not particularly limited, the time _{from time t 1} to time t ₂ , the time from time t ₂ to time t _3, and the time from time t ₃ to time t ₄ are about several hundred MHz. It is preferable that each of the 1 pixel sections is about several hundred ps (picoseconds). By performing such control as shown in FIG. 2 (a), the semiconductor laser can be driven so as to have the amount of light shown in FIG. 1 (b).

Further, as another example of controlling the drive current in the present embodiment, as shown in FIG. 2 (b), at time t _{1 before the time corresponding to one pixel section (time t 4} to time t ₅ ). and the threshold current _{I th, 'and} a high current value I _t than the target current _{I T} at time _{t 3'} current value I _t between the threshold current _{I th} and the target current _{I t} at time _{t 2} the control to _' You may do it. Although the embodiment is not particularly limited, the time _{from time t 1} to time t ₂ , the time from time t ₂ to time t _3, and the time from time t ₃ to time t ₄ are about several hundred MHz. It is preferable that each of the 1 pixel sections is about several hundred ps (picoseconds). By performing such control as shown in FIG. 2 (b), the semiconductor laser can be driven so as to have the amount of light shown in FIG. 1 (b).

It should be noted that the mode of drive current control according to the present embodiment is not limited to that shown in FIGS. 1 and 2. Further, the time for controlling the current before the one pixel section is not limited to several hundred ps as shown in FIGS. 1 and 2, and may be sufficiently short with respect to the time corresponding to the one pixel section. Here, the sufficiently short time is, for example, preferably a time in which the ratio to the one pixel section is shorter than 1:10.

Next, in the present embodiment, the drive device 1 that controls the drive current flowing through the semiconductor laser will be described. In the following description, the drive device 1 and the semiconductor laser that constitute an image projection device (hereinafter, simply referred to as a “display device”) that scans the laser to display an image will be described as an example. Further, in the display device according to the embodiment described, one pixel section is on the order of several hundred MHz.

FIG. 3 is a diagram showing the configuration of the drive device 1 of the present embodiment. As shown in FIG. 3, the drive device 1 of the present embodiment includes a phase dividing circuit 2, a phase selection circuit 3, a current control circuit 5, an on-current circuit 6, and an off-current circuit 7, and includes a semiconductor laser (laser). It is connected to the diode LD).

The phase division circuit 2 is a circuit that performs phase division processing on the input DATA_CLK signal. The DATA_CLK signal is a signal indicating one pixel section, and can be, for example, a pulse signal. The phase division process divides one pixel section into a plurality of phases. The phase dividing circuit 2 can be configured by a PLL circuit as an example, but the embodiment is not particularly limited. Therefore, the phase dividing circuit 2 may be configured by, for example, a delay circuit.

The phase selection circuit 3 is a circuit that selects which phase is used for control among the phases divided by the phase division circuit 2.

The signal generation circuit 4 is a circuit that outputs a control signal for controlling the drive current based on the DATA_CODE input from the outside and the phase selected by the phase selection circuit 3. The signal generation circuit 4 generates, for example, a signal for controlling on / off of the bias circuit, a signal for controlling the DAC circuit (DAC_CODE), and the like. The signal generation circuit 4 outputs the generated control signal to the current control circuit 5.

The current control circuit 5 is a circuit that controls the drive current flowing through the laser diode LD based on the control signal generated by the signal generation circuit 4. The current control circuit 5 can control the value of the output current and the timing. Further, the current control circuit 5 can select the on-current circuit 6 or the off-current circuit 7 as the current output destination. That is, when driving the laser diode LD, a current is passed through the on-current circuit 6, and when the laser diode LD is not driven, a current is passed through the off-current circuit 7. As a result, the output of the current can be switched in a short time, and the emission delay of the laser diode LD can be suppressed. DATA_CODE is a signal for controlling the laser diode LD. For example, in the case of a display device as described in the embodiment, data of an image to be displayed is input as DATA_CODE. The current control circuit 5 can be configured by a bias circuit, a DAC circuit, or the like, and the details will be described in the first and second embodiments.

The on-current circuit 6 is a circuit that allows the current output by the current control circuit 5 to flow through the laser diode LD. In the circuit shown in FIG. 3, the laser diode LD has a power supply connected to the anode side and an on-current circuit 6 connected to the cathode side. Here, the on-current circuit 6 is configured as a current mirror circuit in which two NMOS transistors are connected to each other by gates, and the current output by the current control circuit 5 is applied to the gate portion to obtain the current. A corresponding value of drive current I _op flows through the laser diode LD.

The off-current circuit 7 is a circuit that allows the current output by the current control circuit 5 to flow to the ground. At the timing when the laser diode LD is not driven, the drive current is passed through the off-current circuit 7.

Each circuit in the drive device 1 shown in FIG. 3 may be configured as an independent circuit, or may be configured as a circuit having a plurality of functions described above. Further, it may be realized by making each hardware function by executing a program corresponding to various functions by the CPU. Therefore, all of the functional means corresponding to each circuit may be realized by software, or some or all of them may be implemented as hardware that provides equivalent functions.

Next, the process performed by the drive device 1 will be described. FIG. 4 is a diagram showing an example of phase division and phase selection by the drive device 1 of the present embodiment. FIG. 4A shows an input clock signal (DATA_CLK). The clock signal shown in FIG. 4A is a pulse waveform signal, and the period from the rising edge of the clock to the next rising edge corresponds to one pixel section.

FIG. 4B shows an example of a clock signal whose phase is divided by the phase dividing circuit 2. In the example of FIG. 4B, the phase is divided into 16 phases, but the embodiment is not particularly limited. The phase division can be performed by, for example, dividing by a PLL circuit.

FIG. 4C shows an example in which the phase selection circuit 3 selects the phase at the timing of performing control from the phases divided by the phase division circuit 2. In the example of FIG. 4C, a case where three phases S1, S2, and S3 are selected is shown. Examples of the method of selecting the phase include a method of selecting by a preset register, a method of selecting by terminal control from the outside of the drive device 1, and the like. Three phases S1, the phase selecting circuit 3 selects, S2, S3, for example, as a timing corresponding to time _{t 1,} t 2, _{t 3} respectively, in FIG 1 (a), is outputted to the current control circuit 5.

Up to this point, the configurations common to the first and second embodiments have been described. The details of each embodiment will be described below.

First, the first embodiment will be described. In the first embodiment, the current control circuit 5 of the drive device 1 is configured by a bias circuit. FIG. 5 is a diagram showing the configuration of the current control circuit 5 according to the first embodiment. It should be noted that in FIG. 5, the phase dividing circuit 2 and the phase selection circuit 3 of the driving device 1 are omitted. Further, in the following description, the "bias circuit" refers to a circuit that outputs a predetermined current corresponding to the value of the bias current of the transistor.

In the example of the first embodiment shown in FIG. 5, the bias circuit 51a which outputs a current _{I 1} (BIAS1), the bias circuit 51b (BIAS2) for outputting a current _{I 2,} the bias circuit 51c for outputting a current _{I 3} (BIAS3) and is included. Signals (BI1ON, BI2ON, BI3ON) for outputting their respective currents are input to each bias circuit, and when the signals are input, each bias circuit outputs a current to the on-current circuit 6. Here, the signal that outputs the current is a control signal that is output by the signal generation circuit 4. FIG. 5 shows an example in which the current I ₁ , the current I _2, and the current I ₃ are output to the on-current circuit 6 because the on signal is input to each bias circuit. Here, since the on-current circuit 6 is configured as a current mirror circuit, _{the value of the drive current I op} flowing through the laser diode LD is the sum of the current I ₁ , the current I _2, and the current I ₃ . The number of bias circuits constituting the current control circuit 5 is not limited to that shown in FIG.

Next, the details of the bias circuit will be described. FIG. 6 is a diagram illustrating details of the bias circuit constituting the current control circuit 5 in the first embodiment. FIG. 6A shows an example in which an off signal is input, and FIG. 6B shows an example in which an on signal is input. Although one bias circuit is illustrated in FIG. 6, each bias circuit shown in FIG. 5 has the same configuration.

As shown in FIG. 6, the bias circuit includes a transistor to which a BI_CONT signal is input. The transistor can bias-control the value of the output current by the BI_CONT signal input to the gate. In the example of FIG. 6, the current I is output.

Here, referring to FIGS. 5 and 6, the current control circuit 5 in the first embodiment is controlled as follows. That is, the bias circuit 51a (BIAS1) is controlled to output a current value _{I 1} by a first BI_CONT signal. Further, the bias circuit 51b (BIAS2) is controlled to output the _{current value I 2 by the second BI_CONT signal.} The bias circuit 51c (BIAS3) is controlled to output the current value _{I 3} by the third BI_CONT signal.

Further, the bias circuit shown in FIG. 6 is configured to include two PRIVATE transistors TR1 and TR2 and two inverting elements. The bias circuit is configured by forming a so-called "differential gate" in which a High level is input to the gate of one transistor and a Low level is input to the gate of the other transistor. Therefore, as shown in FIG. 6A, when the OFF signal is input, the transistor TR2 operates and the current I flows through the OFF current circuit 7. Further, as shown in FIG. 6B, when the ON signal is input, the transistor TR1 operates and the current I flows through the on-current circuit 6, and the current I also flows through the laser diode LD having the current mirror circuit configuration. ..

By adopting a circuit having such a differential gate configuration, it is possible to switch on and off in a short time. Therefore, in controlling the drive current flowing through the laser current, it is possible to switch on the order of several hundred ps as described with reference to FIGS. 1 and 2.

Next, the control performed by the current control circuit 5 of the first embodiment will be described. FIG. 7 is a diagram showing control of the drive current of the laser diode LD in the first embodiment. As described with reference to FIGS. 1 and 2, in the present invention, control is performed in which a current equal to or higher than a threshold value is passed through the semiconductor laser for a very short time, and then a target current is passed through the semiconductor laser for a time corresponding to one pixel section. .. In the first embodiment illustrated in FIG. 5, the current control circuit 5 includes three bias circuits. Therefore, by combining the current values output by each bias circuit, for example, FIG. 7 (a) shows. It can be configured to output the current as shown.

As shown in FIG. 7A, the current I ₁ output by the bias circuit 51a is defined as the threshold current I _th . Further, the current _{I 2} bias circuit 51b is output (I _{T '-I th).} Further, the current I3 bias circuit 51c outputs the _{(I T -I T '-I th} ).

Here, the on-signal of each bias circuit is controlled by the timing chart as shown in FIG. 7B. That is, the bias circuit 51a is, BI1ON signal goes High level at time _{t 1,} and outputs the _{I 1.} As a result, the threshold current I _th flows through the laser diode LD. Further, the bias circuit 51b outputs _{I 2} when the BI 2ON signal becomes the High level at _{time t 2.} Thus, the time _{t 2} subsequent to the laser diode LD, a current flows I _{T 'that I 2} is superposed on the _{I 1.} Further, the bias circuit 51c is, BI3ON signal goes High level at time t3, the output _{I 3.} Thus, the time _{t 3} subsequent to the laser diode LD, flows target current _{I T to I 2} and _{I 3} is superimposed on _{I 1.} Therefore, the laser diode LD is driven by the drive current as shown in FIG. 7 (a), emits light with the amount of light shown in FIG. 1 (b), suppresses the light emission delay, and prevents the postcard. Can be done.

Next, the second embodiment will be described. In the second embodiment, the current control circuit 5 of the drive device 1 is configured by a DAC (Digital Analog Converter) control circuit. FIG. 8 is a diagram showing the configuration of the current control circuit 5 in the second embodiment. It should be noted that in FIG. 8, the phase dividing circuit 2 and the phase selection circuit 3 of the driving device 1 are omitted.

As shown in FIG. 8, the current control circuit 5 in the second embodiment controls the drive current by DAC control. The second current control circuit 5 according to the embodiment, ^{2 N} times the current I (N = 0,1,2 ···) and current plurality of outputs 52a that outputs shown in FIG. 8, 52b, 52c ·・ ・ It is configured with. Further, each output unit includes a transistor having a differential gate configuration, so that the current output destination can be switched in a short time. The drive device 1 in the second embodiment controls the drive current by a combination of currents output by each output unit of the DAC circuit.

A DAC_CODE signal for switching the output destination by a differential gate is input to each output unit. The DAC_CODE signal is a control signal generated by the signal generation circuit 4, and includes a DAC_CODE [N] that selects on and off of each output unit. For example, the output unit 52a outputs the current I to the on-current circuit 6 when the input DAC_CODE [0] is at the High level. Further, the output unit 52b outputs the current 2I to the on-current circuit 6 when the input DAC_CODE [1] is at the high level. By such control, the value of the current flowing on the on-current circuit 6 side becomes the sum of the currents output to the on-current circuit 6 by each output unit, and the drive current flowing through the laser diode LD can be controlled.

FIG. 9 is a diagram showing control of the drive current of the laser diode LD in the second embodiment. FIG. 9A is a table in which each DAC_CODE is associated with the current value. Further, FIG. 9B is a diagram in which the diagram showing the time change of the drive current and the DAC_CODE at each time are associated with each other.

In the example shown in FIG. 9A, when 0 is input as DAC_CODE, the drive current is controlled to be 0, that is, each output unit is controlled to pass a current through the off-current circuit 7. Further, when A is input as DAC_CODE, drive current so that the I _th, the control for selecting the combination of the output section that outputs a current to the on-current circuit 6 side is performed. Hereinafter, likewise, in the case where B as DAC_CODE is input, is selected a combination of the output section such that I _{T ',} when C is input as DAC_CODE becomes _{I T} as an output unit The combination of is selected.

In the second embodiment, as shown in the example of FIG. 9 (b), until time _{t 1} is DAC_CODE = 0 is input, DAC_CODE = A from time _{t 1} to time _{t 2} is entered, the time from time _{t 2} DAC_CODE = B is inputted to t _3, DAC_CODE = C is input from time _{t 3} to time _{t 4.} Thus, the laser diode LD, _{I th} flows period from time _{t 1} to time _{t 2,} I _{T 'flows} time from time _{t 2} to time _{t 3,} the time _{t 3} to time _{t 4 IT} flows at the time of. Therefore, the laser diode LD is driven by the drive current as shown in FIG. 9 (b), emits light with the amount of light shown in FIG. 1 (b), suppresses the light emission delay, and prevents the postcard. Can be done.

Next, the phase division process and the phase selection process in the second embodiment will be described with reference to FIG. FIG. 10 is a diagram showing an example of generating a control signal according to the second embodiment. FIG. 10 shows an example in which the DAC circuit generates a signal for controlling to output the drive current shown in FIG.

The upper figure of FIG. 10 shows an example of DATA_CODE, and after DATA_CODE = 0, DATA_CODE = X for one pixel section and DATA_CODE = 0 for one pixel section are input. Here, it is assumed that phase division and phase selection are performed, and S1, S2, and S3 are selected as timings for controlling the current value. Further, it is assumed that the target current at DATA_CODE = X for one pixel section is a value controlled by DAC_CODE = C.

In this case, the signal generating circuit 4, as shown in FIG. 10 below, in front of one pixel section is controlled by DAC_CODE = C, at the timing of S1, the drive current flowing to the laser diode LD is _{I th} DAC_CODE = A is generated. The signal generating circuit 4, DAC_CODE = a previous controlled by one pixel interval in C, and in S2 timing after S1, DAC_CODE driving current flowing through the laser diode LD is such that I _{T '=} Generate B. The signal generating circuit 4, the drive current flowing to the laser diode LD at a timing S3, 1 pixel period is started to generate a DAC_CODE = B such that _{I T.}

Up to this point, the first embodiment and the second embodiment of the present invention have been described. Hereinafter, more specific examples to which the present invention is applied will be described. The present invention may be applied to other than the examples described below.

[Example 1: Image projection device]
Next, the image projection device to which the drive device 1 of the present embodiment is applied will be described in detail with reference to FIGS. 11 and 12.

FIG. 11 is a schematic view of an embodiment of an automobile 400 equipped with a head-up display device 500, which is an example of an image projection device. Further, FIG. 12 is a schematic view of an example of the head-up display device 500.

The image projection device is a device that projects an image by optical scanning, for example, a head-up display device.

As shown in FIG. 11, the head-up display device 500 is installed near, for example, a windshield (windshield 401, etc.) of an automobile 400. The projected light L emitted from the head-up display device 500 is reflected by the windshield 401 and heads toward the observer (driver 402) who is the user. As a result, the driver 402 can visually recognize the image or the like projected by the head-up display device 500 as a virtual image. A combiner may be installed on the inner wall surface of the windshield so that the user can visually recognize the virtual image by the projected light reflected by the combiner.

As shown in FIG. 12, the head-up display device 500 emits laser light from red, green, and blue laser light sources 501R, 501G, and 501B. The emitted laser light passes through an incident optical system composed of collimating lenses 502, 503, 504 provided for each laser light source, two dichroic mirrors 505, 506, and a light amount adjusting unit 507. It is deflected by a movable device 13 having a reflecting surface 14. Then, the deflected laser beam is projected onto the screen via a projection optical system including a free-form surface mirror 509, an intermediate screen 510, and a projection mirror 511. In the head-up display device 500, the laser light sources 501R, 501G, 501B, the collimating lenses 502, 503, 504, and the dichroic mirrors 505 and 506 are unitized by an optical housing as a light source unit 530.

The head-up display device 500 projects the intermediate image displayed on the intermediate screen 510 onto the windshield 401 of the automobile 400, so that the driver 402 visually recognizes the intermediate image as a virtual image.

The laser light of each color emitted from the laser light sources 501R, 501G, and 501B is made substantially parallel light by the collimated lenses 502, 503, and 504, and is synthesized by two dichroic mirrors 505 and 506, which are synthesis units. The combined laser light is two-dimensionally scanned by the movable device 13 having the reflecting surface 14 after the light amount is adjusted by the light amount adjusting unit 507. The projected light L two-dimensionally scanned by the movable device 13 is reflected by the free-form surface mirror 509, corrected for distortion, and then condensed on the intermediate screen 510 to display an intermediate image. The intermediate screen 510 is composed of a microlens array in which microlenses are two-dimensionally arranged, and magnifies the projected light L incident on the intermediate screen 510 in microlens units.

The movable device 13 reciprocates the reflecting surface 14 in the biaxial direction, and two-dimensionally scans the projected light L incident on the reflecting surface 14. The drive control of the movable device 13 is performed in synchronization with the light emission timing of the laser light sources 501R, 501G, and 501B.

The head-up display device 500 as an example of the image projection device has been described above, but the image projection device may be a device that projects an image by performing optical scanning by a movable device 13 having a reflecting surface 14. .. For example, it is mounted on a projector that is placed on a desk or the like and projects an image on a display screen, or is mounted on a mounting member mounted on an observer's head or the like, and is projected onto a reflection / transmission screen of the mounting member, or an eyeball is used as a screen. The same can be applied to a head-mounted display device or the like that projects an image.

Further, the image projection device is not only a vehicle or a mounting member, but also, for example, a moving body such as an aircraft, a ship, or a mobile robot, or a work robot that operates a drive target such as a manipulator without moving from the place. It may be mounted on a non-moving body.

The head-up display device 500 is an example of the "head-up display" described in the claims.

[Example 2: Laser headlamp]
Next, the laser headlamp 50 in which the drive device 1 of the present embodiment is applied to the headlight of an automobile will be described with reference to FIG. FIG. 13 is a schematic view illustrating an example of the configuration of the laser headlamp 50.

The laser headlamp 50 includes a control device 11, a light source device 12, a movable device 13 having a reflecting surface 14, a mirror 51, and a transparent plate 52.

The light source device 12 is a light source that emits a blue laser beam. The light emitted from the light source device 12 enters the movable device 13 and is reflected by the reflecting surface 14. The movable device 13 moves the reflecting surface 14 in the XY directions based on the signal from the control device 11, and scans the blue laser light from the light source device 12 in the XY directions in two dimensions.

The scanning light from the movable device 13 is reflected by the mirror 51 and incident on the transparent plate 52. The front surface or the back surface of the transparent plate 52 is covered with a yellow phosphor. The blue laser beam from the mirror 51 changes to white within the legal range of the headlight color as it passes through the yellow phosphor coating on the transparent plate 52. As a result, the front of the automobile is illuminated with white light from the transparent plate 52.

The scanning light from the movable device 13 scatters in a predetermined manner when passing through the phosphor of the transparent plate 52. This alleviates the glare of the illuminated object in front of the vehicle.

When the movable device 13 is applied to the headlight of an automobile, the colors of the light source device 12 and the phosphor are not limited to blue and yellow, respectively. For example, the light source device 12 may be near ultraviolet rays, and the transparent plate 52 may be coated with a uniform mixture of blue, green, and red phosphors of the three primary colors of light. Even in this case, the light passing through the transparent plate 52 can be converted to white, and the front of the automobile can be illuminated with white light.

According to the embodiment of the present invention described above, it is possible to provide a drive device, a light source, an image projection device, and a head-up display that prevent postcards.

Each function of the embodiment of the present invention described above can be realized by a device executable program described in C, C ++, C #, Java (registered trademark), etc., and the program of the present embodiment is a hard disk device, a CD-. It can be stored and distributed in device-readable recording media such as ROM, MO, DVD, flexible disk, EEPROM (registered trademark), and EPROM, and can be transmitted via a network in a format that other devices can. ..

Although the present invention has been described above with embodiments, the present invention is not limited to the above-described embodiments, and as long as the present invention exerts its actions and effects within the range of embodiments that can be conceived by those skilled in the art. , Is included in the scope of the present invention.

1 ... Drive device, 2 ... Phase division circuit, 3 ... Phase selection circuit, 4 ... Signal generation circuit, 5 ... Current control circuit, 51a to c ... Bias circuit, 52a to c ... Output unit, 6 ... On current circuit, 7 ... Off-current circuit, 11 ... Control device, 12 ... Light source device, 13 ... Movable device, 14 ... Reflective surface, 50 ... Laser head lamp, 51 ... Mirror, 52 ... Transparent plate, 400 ... Automobile, 401 ... Front glass, 402 Driver, 500 ... Head-up display device, 501B: Laser light source, 501G: Laser light source, 501R: Laser light source, 502 ... Collimating lens, 503 ... Collimating lens, 504 ... Collimating lens, 505 ... Dycroic mirror, 506 ... Dycroic mirror , 507 ... Light amount adjustment unit, 509 ... Free curved mirror, 510 ... Intermediate screen, 511 ... Projection mirror, LD ... Laser diode

Japanese Patent No. 4432459

Claims (10)

A drive device that drives a semiconductor laser that oscillates in multiple modes.
A control means for controlling the current flowing through the semiconductor laser is included.
The control means
The first control that sets the current to be equal to or higher than the threshold value at which the semiconductor laser oscillates,
After the first control, a second control is performed in which the current is set to a predetermined value with a predetermined pulse width.
In the first control, the time during which the current becomes equal to or higher than the threshold value is shorter than the pulse width.
Drive device. The control means
After the first control and before the second control, at a time shorter than the pulse width.
A third control is performed in which the current is set to a value higher than the value of the current in the first control and lower than the value of the current in the second control.
The drive device according to claim 1. The control means
After the first control and before the second control, at a time shorter than the pulse width.
A fourth control is performed in which the current is set to a value higher than the current in the second control.
The drive device according to claim 1 or 2. A dividing means for dividing the phase of the clock signal corresponding to the pulse width, and
Among the phases divided by the dividing means, the control means includes a selection means for selecting a phase for performing each control.
The control means is characterized in that control is performed based on the phase selected by the selection means.
The drive device according to any one of claims 1 to 3. The control means is characterized in that it controls by a combination of currents output by a plurality of bias circuits.
The drive device according to any one of claims 1 to 4. The control means is characterized in that it is controlled by a control that outputs a current by a DAC circuit.
The drive device according to any one of claims 1 to 4. The driving device according to any one of claims 1 to 6, wherein the ratio of the time shorter than the pulse width to the pulse width is smaller than 1:10. A semiconductor laser that oscillates in multiple modes
Including a control means for controlling the current flowing through the semiconductor laser.
The control means
The first control that sets the current to be equal to or higher than the threshold value at which the semiconductor laser oscillates,
After the first control, a second control is performed in which the current is set to a predetermined value with a predetermined pulse width.
In the first control, the time during which the current becomes equal to or higher than the threshold value is shorter than the pulse width.
light source. An image projection device including the light source according to claim 8. A head-up display comprising the light source according to claim 8.

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