JP2009049132A - Laser light source device and projector - Google Patents

Abstract

The response of laser output is improved.
A semiconductor chip is provided with a laser diode LD and a high-speed diode FD. The laser diode LD is supplied with a first drive current I1 according to a modulation command signal given from the outside. The high speed diode FD is supplied with the second drive current I2. The second drive current I2 is a value such that the sum total with the first drive current I1 is constant. With this configuration, since heat is generated from both the laser diode LD and the high-speed diode FD, a sufficient thermal lens effect can always be generated.
[Selection] Figure 1

Description

  The present invention relates to a laser light source device including a laser diode and a projector including the laser light source device.

  Conventionally, a laser diode (LD) is used as a light source for a projector or the like (Patent Document 1). Laser diodes enable laser oscillation by stably causing a thermal lens effect. The thermal lens effect means that when a laser diode is driven, the temperature rises locally to generate a refractive index distribution, which functions as a lens.

JP 2007-33576 A

  Some projectors use a method of modulating the intensity of output light by changing the drive current of the laser diode. However, in this type of projector, it is necessary to frequently change the drive current supplied to the laser diode. On the other hand, the laser diode has a long thermal time constant, and the thermal lens effect cannot be generated with good responsiveness in accordance with the drive current. As a result, the conventional laser diode may cause a delay in response to the laser output.

  The present invention has been made in order to solve the above-described conventional problems, and an object thereof is to improve the response of laser output.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A semiconductor chip comprising a laser diode;
In a laser light source device comprising: first driving means for supplying a first driving current corresponding to a command signal given from outside to the laser diode;
The semiconductor chip includes a temperature control diode,
further,
2. A laser light source device comprising: a second drive unit configured to supply a second drive current corresponding to the first drive current to the temperature control diode.

  According to the laser light source device described in the application example 1, the semiconductor chip includes the laser diode and the temperature control diode, and the laser diode supplies the first drive current according to the command signal given from the outside. The temperature control diode receives the second drive current corresponding to the first drive current. For this reason, since the semiconductor chip can be heated from both the laser diode and the temperature control diode, even when the thermal lens effect is not sufficiently generated only by driving the laser diode, the temperature control is performed. It is possible to generate a sufficient thermal lens effect by receiving heat from the diode for use.

  Therefore, according to the laser light source device described in the application example 1, it is possible to always generate a sufficient thermal lens effect, so that it is possible to perform laser output with high response according to the drive current.

[Application Example 2]
In the laser light source device according to Application Example 1, the second driving unit determines the second driving current so that a sum of the first driving current and the second driving current is constant. A laser light source device comprising a computing means.

  According to the laser light source device described in the application example 2, the sum of the first drive current supplied to the laser diode and the second drive current supplied to the temperature control diode is constant. The sum of heat generation from both the temperature control diode and the temperature control diode is constant. For this reason, the temperature of the semiconductor chip provided with both is kept constant. Therefore, according to the laser light source device described in the application example 2, it is possible to generate the sufficient thermal lens effect more reliably and always, so that the response of the laser output can be further improved.

[Application Example 3]
The laser light source device according to Application Example 2, comprising a drive current detection unit that detects a drive current actually supplied to the laser diode as the first drive current.

  According to the laser light source device described in Application Example 3, the second drive current can be calculated using the drive current actually measured by the drive current detection unit as the first drive current. Therefore, since the temperature of the semiconductor chip can be controlled with higher accuracy, the response of the laser output can be further improved.

[Application Example 4]
The laser light source device according to Application Example 2 or 3, wherein the first driving unit is connected to the laser diode and controls a current supplied from a power source to the laser diode in accordance with an input signal. And a means for outputting a first pulse signal corresponding to the command signal as the input signal to the first transistor, and the second driving means is connected to the temperature control diode. A second transistor for controlling a current supplied from a power source to the temperature control diode according to an input signal, and a second pulse signal corresponding to the second drive current calculated by the computing means. A laser light source device comprising: means for outputting to the second transistor as an input signal.

  According to the laser light source device described in the application example 4, the first driving unit and the second driving unit can be configured with a simple configuration.

[Application Example 5]
The laser light source device according to any one of Application Examples 1 to 4, control means for sending an image signal as the command signal to the laser light source device, and laser light from the laser light source device, A projector comprising image forming means for displaying an image according to an image signal.

  As described above, according to the projector described in application example 5, since the laser light source device with excellent responsiveness can be used, a high-quality image can be displayed.

  The present invention can be realized in various forms other than the above. For example, an illumination device including the laser light source device of the present invention, a display device including the laser light source device of the present invention, and a laser light source including the laser light source device of the present invention. It can be realized in the form of an apparatus system or the like.

Next, embodiments of the present invention will be described based on examples.
1. First embodiment:
FIG. 1 is a block diagram showing a schematic configuration of a laser light source apparatus 10 as a first embodiment of the present invention. As illustrated, the laser light source device 10 includes a semiconductor chip 20 having a laser diode LD and a high-speed diode FD.

  FIG. 2 is an explanatory diagram showing a schematic configuration of the semiconductor chip 20. The semiconductor chip 20 is roughly formed by sequentially stacking a p-type layer 22 and an n-type layer 23 on a GaAs substrate 21 (upper part on the left side in the drawing), and a first side on the surface side of the n-type layer 23. The electrode 24 has a structure in which a second electrode (back electrode) 25 electrically connected to the p-type layer 22 is attached to the back side of the GaAs substrate 21. Further, a p-type layer 31 and an n-type layer 32 are sequentially laminated on the GaAs substrate 21 (on the right side in the figure), and a third electrode 33 is disposed on the surface side of the n-type layer 32, and the GaAs substrate 21. The fourth electrode (back electrode) 34 that is electrically connected to the p-type layer 31 is attached to the back surface side of each. The structure thus formed is placed on a mount (not shown) via the submount 36.

  The p-type layer 22 and the n-type layer 23 stacked on the right side in the figure constitute a laser diode LD that emits the laser beam LB to the outside. The p-type layer 31 and n stacked on the left side in the figure are formed. The mold layer 32 constitutes a high speed diode FD. The anode of the laser diode LD corresponds to the second electrode 25, and the cathode of the laser diode LD corresponds to the first electrode 24. The cathode of the high speed diode FD corresponds to the third electrode 33, and the anode of the high speed diode FD corresponds to the fourth electrode 34. The high speed diode FD corresponds to the “temperature control diode” of the present invention.

  Returning to FIG. 1, the anode of the laser diode LD is connected to the positive electrode of the power source E, and the anode of the high speed diode FD is connected to the positive electrode of the power source E.

  The cathode of the laser diode LD is connected to the negative electrode of the power supply E via the first resistor R1 and the first transistor T1, and the cathode of the fast diode FD is connected via the second resistor R2 and the second transistor T2. Connected to the negative electrode of the power supply E. Specifically, the cathode of the laser diode LD is connected to the collector of the first transistor T1 via the first resistor R1, and the negative electrode of the power source E is connected to the emitter of the first transistor T1. The cathode of the high speed diode FD is connected to the collector of the second transistor T2 via the second resistor R2, and the negative electrode of the power source E is connected to the emitter of the second transistor T2.

  An arithmetic circuit 40 is connected to each base of the first transistor T1 and the second transistor T2, and control signals (pulse signals) S1, S2 are output from the arithmetic circuit 40 to the transistors T1, T2. Specifically, the arithmetic circuit 40 includes a first arithmetic unit 41 and a second arithmetic unit 42, and the control signal S1 is output from the first arithmetic unit 41 to the first transistor T1, and the second The control signal S2 is output from the calculation unit 42 to the second transistor T2. The first calculation unit 41 can control the first drive current I1 supplied to the laser diode LD by varying the pulse width and amplitude of the control signal S1 sent to the first transistor T1. The second arithmetic unit 42 can control the drive current I2 supplied to the high-speed diode FD by changing the pulse width and amplitude of the control signal sent to the second transistor T2.

  The arithmetic circuit 40 is composed of a discrete electronic circuit, and executes a logical operation process described later. The arithmetic circuit 40 may be configured by a microcomputer including a microprocessor and a memory instead of the above configuration, and the microprocessor executes a computer program stored in the memory, thereby executing processing described later.

  The connection part 50 between the first resistor R1 and the first transistor T1 is electrically connected to the second arithmetic part 42 of the arithmetic circuit 40. Thereby, the 2nd calculating part 42 can know the magnitude | size detected by the resistor R1. That is, the second calculation unit 42 can detect the drive current I1 that is actually supplied to the laser diode LD.

  The first and second calculation units 41 and 42 perform the following calculation process. The first calculation unit 41 receives the modulation command signal (command signal) of the laser diode LD, and outputs a pulse signal corresponding to the modulation command signal to the first transistor T1 as the first control signal S1. Do. As a result, the first drive current I1 corresponding to the modulation signal is supplied to the laser diode LD.

  The second arithmetic unit 42 uses i) the first driving current I1 detected by the first resistor R1, that is, the target driving current supplied to the high-speed diode FD using the driving current I1 supplied to the laser diode LD. TI2 is obtained, and ii) a process of outputting a pulse signal corresponding to the target drive current TI2 to the second transistor T2 as the second control signal S2. The calculation of the target drive current TI2 in the above i) follows the following formula (1).

TI2 = Iconst−I1 (1)
Here, Iconst is a constant current value, for example, the maximum value Imax that can be taken by the drive current I1 of the laser diode LD. Instead of Imax, a value larger than Imax can be used.

As a result of the processing of the second arithmetic unit 42, the second drive current I2 that satisfies the following formula (2) is supplied to the high-speed diode FD.
I1 + I2 = Iconst (2)

  The configuration of the first calculation unit 41 and the first transistor T1 corresponds to the first driving means of the present invention, and the configuration of the second calculation unit 42 and the second transistor T2 is the present invention. This corresponds to the second driving means.

  The operation of the laser light source device 10 configured as described above will be described based on the timing chart of FIG. As shown in FIGS. 3A and 3B, the drive current (first drive current) I1 of the laser diode LD and the drive current (second drive current) I2 of the high-speed diode FD are turned on / off with time. This is a pulse signal that is turned off, and its pulse width and amplitude change. The first drive current I1 and the second drive current I2 have shapes that are inverted from each other, and the sum of both is always a constant value Iconst (= Imax).

  In a period from time 0 to time t1 (hereinafter referred to as “first period”), the first drive current I1 has a value 0, and the second drive current I2 has Imax. When the first drive current I1 rises from the value 0 to Imax at time t1, the second drive current I2 falls from Imax to the value 0. In the period from time 1 to time t2 (hereinafter referred to as “second period”), the first drive current I1 is Imax, and the second drive current I2 is 0. At time t2, the first drive current I1 falls from Imax to the value 0, and the second drive current I2 rises from Imax to the value 0.

  FIG. 3C shows the temperature TE of the semiconductor chip 20. The broken line in this graph is for a conventional semiconductor chip that does not have the high-speed diode FD. In the conventional example, since the high-speed diode FD is not provided, the temperature of the semiconductor chip is the ambient temperature in the first period in which the first drive current I1 supplied to the laser diode is 0. After that, at time t1, the laser diode LD starts to generate heat as the first drive current I1 rises, and the semiconductor chip temperature starts to rise as shown by the broken line in the figure. In the second period, the temperature of the semiconductor chip gradually increases. Thus, in the conventional example, the temperature rise of the semiconductor chip is delayed with respect to the rise of the first drive current.

  On the other hand, in the semiconductor chip 20 of the present embodiment, the semiconductor chip temperature gradually increases in the first period as shown by the solid line in FIG. This is because, even if the laser diode LD is not driven, the high-speed diode FD is driven by being supplied with the second drive current I2. Thereafter, after the time t1, the temperature of the semiconductor chip 20 reaches a set temperature TE0 determined in advance at the time of design. Regardless of the subsequent change in the first drive current, the semiconductor chip temperature maintains the set temperature TE0. This is because the sum of the first drive current I1 and the second drive current I2 is always constant. That is, since the heat generation efficiency of the diode is not so different depending on the type of laser diode, high-speed diode, etc., by making the sum of the first drive current I1 and the second drive current I2 constant, The semiconductor chip temperature can be kept at the set temperature TE0. Therefore, in this embodiment, the temperature of the semiconductor chip 20 can be raised to the set temperature TE0 even when the first drive current rises.

  FIG. 3D shows the laser light amount LA. As described above, in the conventional laser diode, the temperature of the semiconductor chip rises with a delay with respect to the rise of the first drive current, so that the thermal lens effect is generated with good response according to the first drive current. I can't. For this reason, as indicated by a broken line, the amount of laser light gradually increases with a delay from time t1 when the first drive current rises to Imax. On the other hand, in the present embodiment, as indicated by the solid line, the temperature of the semiconductor chip 20 has substantially reached the set temperature TE0 even at time t1, so that the thermal lens effect has a good response according to the first drive current. Can be generated. Accordingly, the laser light amount LA immediately rises at time t.

  In the period from time t3 to t4 in the figure (hereinafter referred to as “third period”), the first drive current is about ½ of Imax. In the conventional example, in such a case, the semiconductor chip temperature is considerably lower than the set temperature TE0. For this reason, a sufficient thermal lens effect cannot be generated, and a sufficient amount of laser light corresponding to the first drive current cannot be obtained as shown. On the other hand, in this embodiment, the semiconductor chip temperature TE is the set temperature TE0 even in the third period in which the first drive current I1 is about ½ of Imax. A thermal lens effect can be generated, and a laser light amount LA corresponding to the first drive current I1 can be obtained.

  As described above in detail, the laser light source device 10 of this embodiment has good responsiveness to the rise of the first drive current I1 when the first drive current I1 supplied to the laser diode LD changes intermittently. The followed laser light amount LA can be obtained. Furthermore, even when the first drive current I1 is smaller than Imax, it is possible to obtain a laser light amount LA corresponding to the first drive current I1 with good responsiveness.

2. Second embodiment:
Next, a second embodiment of the present invention will be described. In the first embodiment, the laser light source device 10 has been described. However, the second embodiment is an example in which the laser light source device 10 of the first embodiment is employed in a projector.

  FIG. 4 is an explanatory diagram showing a schematic configuration of a scanning projector 100 as the second embodiment. As illustrated, the projector 100 emits a first color laser light source device 10R that emits a first color laser light, a second color laser light source device 10G that emits a second color laser light, and a third color laser light. A third color laser light source device 10B, a galvanometer mirror 120 (scanning unit), a control unit 130, and the like.

  The first to third color laser light source devices 10R, 10G, and 10B adopt the same configuration as the laser light source device 10 of the first embodiment, and as described above, the laser diode LD, the fast diode FD, and the arithmetic circuit. 40 etc. are provided. The difference is whether a red laser diode, a green laser diode, or a blue laser diode is used as the laser diode LD. That is, the first color laser light source device 10R uses a red laser diode, the second color laser light source device 10G uses a green laser diode, and the third color laser light source device 10B uses a blue laser diode.

  The control unit 130 outputs an image signal (video signal) as a modulation command signal to the arithmetic circuit 40 provided in each of the first to third color laser light source devices 10R, 10G, and 10B. As a result, the red (R) light, the green (G) light, and the blue (B) light emitted from the laser diodes LD provided in the first to third color laser light source devices 10R, 10G, and 10B are in accordance with the image signal. Modulated.

  Although not shown in FIG. 4, actually, the R light, G light, and B light emitted from the respective color laser light source devices 10R, 10G, and 10B are two dichroic mirrors 112 and 114 as shown in FIG. To the galvanometer mirror 120. That is, the first dichroic mirror 112 transmits R light and reflects G light, and the second dichroic mirror 114 transmits R light and G light and reflects B light, whereby R light, G light is reflected. Synthesize light and B light. In this way, modulated light of each color light of R, G, and B is emitted to the galvanometer mirror 120 that is an optical scanning unit.

  Returning to FIG. 1, the galvanometer mirror 120 scans the incident R light, G light, and B light in a two-dimensional direction by rotating the reflecting surface about two predetermined axes. This scanning is executed according to a command from the control unit 130. In FIG. 1, the galvanometer mirror 120 is shown rotating about the axis AX. Each color light from the galvanometer mirror 120 enters the screen 140. The screen 140 displays a projected image with each color light scanned by the galvanometer mirror 120. Image forming means for displaying an image corresponding to the image signal on the display surface using the laser light from the laser light source devices 10R, 10G, and 10B by the scanning control processing executed by the galvanometer mirror 120 and the control unit 130. Realized.

  According to the projector 100 of the second embodiment configured as described above, since the laser light source devices 10R, 10G, and 10B having excellent responsiveness can be used, a high-quality image can be displayed.

3. Other embodiments:
The present invention is not limited to the above-described first embodiment, second embodiment, and modifications thereof, and can be carried out in various modes without departing from the gist thereof. Such modifications are possible.

(1) In the above embodiment, the high-speed diode FD is formed as a temperature control diode provided in the semiconductor chip. However, this type of diode is not necessarily required, and a light-emitting diode, a laser diode (semiconductor laser), It can be replaced with a diversion diode. Although not specifically mentioned in the above embodiment, the laser diode LD may be of any type such as an edge emitting laser or a surface emitting laser (including VCSEL (Vertical Cavity Surface Emitting Laser)).

(2) In the above-described embodiment, the second calculation unit 42 measures the actual measured value of the first drive current I1 supplied to the laser diode LD, and supplies the high-speed diode FD based on the actual measured value. The drive current TI2 is obtained, and a process of outputting a pulse signal corresponding to the target drive current TI2 as the second control signal S2 to the second transistor T2 has been performed. Instead, the second calculation unit 42 May be configured to perform the following processing. Since the first and second drive currents I1 and I2 are basically linearly proportional to the control signals S1 and S2, the second calculation unit 42 sets Iconst, which is the sum of I1 and I2 described above. A corresponding control constant value is determined, and the value of the control signal S2 is obtained by subtracting the value of the control signal S1 obtained by the first calculation unit 41 from the control constant value, and the second control signal S2 is obtained as the second control signal S2. A process of outputting to the second transistor T2 is performed. Also with this configuration, as in the first embodiment, a sufficient thermal lens effect can always be generated, so that laser output can be performed with good responsiveness according to the drive current.

(3) In the second calculation unit 42 of the embodiment, the second drive current I2 is obtained so that the sum of the first drive current I1 and the second drive current I2 is constant. It is not necessarily required to be constant. Instead of this configuration, when the first drive current I1 is off (value 0), the second drive current is turned on and the first drive current I1 is turned on ( When >> 0), the second drive current may be turned off. Also with this configuration, it is possible to obtain the effect of improving the responsiveness compared to the conventional case. In short, the second drive current may be configured to correspond to the first drive current, and any configuration may be used.

(4) In the second embodiment, the laser light source device 10 of the first embodiment is applied to a scanning projector. However, the laser light source device 10 is not necessarily applied to a scanning projector. The projector (liquid crystal light valve, micromirror device, etc.) is used for a projector that modulates the laser light from the laser light source device with a light modulator to form an image and projects the image with a projection lens (projection unit). May be. Although the laser light source device 10 of the first embodiment is applied to the projector, it is not necessarily applied to the projector, and may be applied to other configurations such as an illumination device, a monitor device, and a communication device. .

(5) In the second embodiment, the image signal is represented by the video signals of the three primary colors R, G, and B. However, the image signal is not necessarily limited to the three primary colors, and the video signal is represented by other color components. The present invention can also be applied. A monochrome image may also be used. Furthermore, the present invention can also be applied to still image images instead of video signals that are moving images.

1 is a block diagram showing a schematic configuration of a laser light source device 10 as a first embodiment of the present invention. 2 is an explanatory diagram showing a schematic configuration of a semiconductor chip 20. FIG. 3 is a timing chart showing the operation of the laser light source device 10. It is explanatory drawing which shows schematic structure of the projector 100 as 2nd Example. It is explanatory drawing which shows the aspect which synthesize | combines the output light of 1st thru | or 3rd color laser light source apparatus 10R, 10G, 10B.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Laser light source apparatus 10R ... 1st color laser light source apparatus 10G ... 2nd color laser light source apparatus 10B ... 3rd color laser light source apparatus 20 ... Semiconductor chip 21 ... GaAs substrate 22 ... p-type layer 23 ... n-type layer 24 ... 1st DESCRIPTION OF SYMBOLS 1 electrode 25 ... 2nd electrode 31 ... p-type layer 32 ... n-type layer 33 ... 3rd electrode 34 ... 4th electrode 36 ... Submount 40 ... Arithmetic circuit 41 ... 1st and 2nd calculating part 41 DESCRIPTION OF SYMBOLS 1st calculating part 42 ... 2nd calculating part 50 ... Connection part 100 ... Projector 112 ... 1st dichroic mirror 114 ... 2nd dichroic mirror 120 ... Galvano mirror 130 ... Control part 140 ... Screen LD ... Laser diode FD ... fast diode R1 ... first resistor R2 ... second resistor T1 ... first transistor T2 ... second transistor E ... power supply I1 ... first Of the drive current I2 ... second driving current LB ... laser light

Claims (5)

A semiconductor chip comprising a laser diode;
In a laser light source device comprising: first driving means for supplying a first driving current corresponding to a command signal given from outside to the laser diode;
The semiconductor chip includes a temperature control diode,
further,
2. A laser light source device comprising: a second drive unit configured to supply a second drive current corresponding to the first drive current to the temperature control diode. The laser light source device according to claim 1,
The second driving means includes
A laser light source device, comprising: arithmetic means for determining the second drive current so that a sum of the first drive current and the second drive current is constant. The laser light source device according to claim 2,
A laser light source device comprising drive current detection means for detecting a drive current actually supplied to the laser diode as the first drive current. The laser light source device according to claim 2 or 3,
The first driving means includes
A first transistor connected to the laser diode and controlling a current supplied from a power source to the laser diode according to an input signal;
Means for outputting a first pulse signal corresponding to the command signal to the first transistor as the input signal;
The second driving means includes
A second transistor connected to the temperature control diode and controlling a current supplied from a power source to the temperature control diode according to an input signal;
A laser light source device comprising: a second pulse signal corresponding to the second drive current calculated by the calculation means; and a means for outputting the second pulse signal as the input signal to the second transistor. A laser light source device according to any one of claims 1 to 4,
Control means for sending an image signal to the laser light source device as the command signal;
A projector comprising: an image forming unit configured to display an image corresponding to the image signal on a display surface using laser light from the laser light source device.

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