JP3222217B2 - Semiconductor laser system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser system for performing electrophotographic exposure using a semiconductor laser device.

[0002]

2. Description of the Related Art On a chip of a semiconductor laser device used in a conventional semiconductor laser system, a heating element which merely consumes power without irradiating a laser beam is not provided.

[0003]

In a semiconductor laser system using such a conventional semiconductor laser device, a laser element of the semiconductor laser device emits laser light when the laser is turned on, so that a laser beam output is required to heat the chip. And when used as an exposure means in an electrophotographic apparatus such as a laser beam printer, it causes image density unevenness. In view of the above problems, the present invention uses a semiconductor laser device that keeps the power consumed by the chip constant even when the laser element is switched from the non-lighting state to the lighting state, and thus does not reduce the laser light output during lighting,
It is another object of the present invention to provide a semiconductor laser system capable of controlling the operation of the semiconductor laser.

[0004]

SUMMARY OF THE INVENTION A semiconductor laser system according to the present invention comprises a semiconductor laser device in which an element unit including a laser element and a heating element for heating the chip is formed on one chip, a constant current source, , The constant current source
These currents are supplied to the laser element when the laser is turned on.
When the laser is not lit, supply to the heating element
Semiconductor laser consisting of differential switch for switching drive
In the system, a heating element is connected in parallel with the heating element.
A resistor that bypasses part of the current flowing through the thermal element, or
Or connected in parallel with the laser element,
Provision of a resistor to bypass a part of the flowing current
It is characterized by .

Preferably, a plurality of the element units are formed on the chip, and the heating element is formed separately from the laser element so as not to emit laser light in a normal laser light emission direction. A heating laser element or a diode element, and the resistor is externally adjusted.
A possible variable resistor.

[0006]

The control device drives the laser element when the laser is turned on, and switches the heating element when the laser is not turned on, so that the chip on which both the laser element and the heating element are formed is kept at a constant temperature. Therefore, even if a certain laser element is turned on when not lit, the laser light output is not reduced when lit.

[0007]

Next, reference examples and embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an element unit of a semiconductor laser device used in a first reference example of the semiconductor laser system of the present invention, FIG. 2 is a block diagram showing a first reference example of the semiconductor laser system of the present invention, FIG. 3 is a block diagram showing the semiconductor laser driver of FIG. 2 in detail.

The element unit of the semiconductor laser device shown in FIG. 1 has an internal stripe structure semiconductor element (A) in which an n-type current blocking layer is deposited on a p-type substrate and a V-shaped groove is etched.
ppl. Phys. Lett. vol. 40,1 Ma
rch 1982, p. 312). In FIG. 1, reference numeral 1 denotes a P-type GaAs substrate;
Is an n-GaAs current blocking layer, and 3 and 4 are stripe grooves formed by a well-known photolithography technique. Inside the stripe grooves 3 and 4, the current blocking layer 2 is removed. Becomes 5 _{p-Ga 1-Y Al Y} A S cladding layer, 6 Ga _1-Y Al _X A _S active layer (0 <X <Y
<1), 7 _{n-Ga 1-Y Al Y} A S cladding layer, 8 forms a laser operation for multi-crystal layer of a double heterojunction is n-GaAs gap layer. P of Au-Zn of 9
A side electrode, 10 is an Au-Ge-Ni n-side electrode, 11 is a separation groove formed in parallel from the n-side electrode 10 to the GaAs substrate by etching, and 12 is a laser beam irradiated outside the chip. This is a plastic for shielding so as not to be shielded, and the one provided with this shield becomes a dummy laser element.

[0009] Next, a first reference example of the semiconductor laser system of the present invention FIG. 2 will be described with reference to FIG. The semiconductor laser device 100 includes an element unit 101 (see FIG. 1), which is a laser chip including a laser element 102 and a dummy laser element 103, and a pin photodiode 104 for detecting a laser output amount of the laser element 102. I have. 106 is a load resistance for setting the laser current,
107 is a load resistance for converting the current of the pin photodiode 104 into a voltage. Reference numeral 108 denotes a CPU which is a means for controlling the amount of laser light, and includes an analog / digital conversion input port 109 (hereinafter referred to as A / D converter).
D input port 109), digital / analog conversion output port 110 (hereinafter referred to as D / A output port 110), arithmetic unit 111 (hereinafter referred to as ALU 111),
Further, a ROM 112, a RAM 113, and the like as storage means are provided.

[0010] CPU108 of the D / A output port 110 and the semiconductor laser current setting voltage terminal V _L1, V _L2 of the laser driver 105 are connected, each terminal V _L1,
Output voltages V ₁ and V ₂ applied to V _L2 (V ₁ is for coarse adjustment,
V ₂ is the amount of laser light laser current is increased by increasing the fine for adjustment) is increased. The laser light amount is converted into a light amount and a current by the pin photodiode 104, and the current and the voltage are further converted by the load resistor 107.
08 is fed back to the A / D input port as an input voltage (signal name MO). The CPU changes the output voltage of the D / A output port 110 so that the input voltage MO becomes equal to the set target value, thereby making the laser light amount constant.

Next, as means for turning on / off the laser, as shown in FIG. 3, the switching data input terminal DATAL of the semiconductor laser driver 105 is set to a low level (hereinafter, L level).
In this case, the current I _LD flows through the built-in differential current switch 114 toward the laser element 102 connected to the laser connection terminal LD, causing the laser element 102 to emit light, and setting DATAL to a high level (hereinafter, H level). In this case, a current flows through the dummy laser element 103 connected to the laser current load resistance connection terminal RO.

FIG. 4 is a timing chart of switching of the element unit 101. The current I _LD flowing through the laser element 102 and the current I _RO flowing through the dummy laser element 103 are shown.
It is always a constant current I _L of the total.

As described above, at least one of the plurality of laser elements 102 and 103 provided on one chip is a dummy laser element 1 from which laser light is not emitted outside the laser element.
03, when the laser element 102 is not lit (non-energized), power is supplied to the dummy laser element 103 for power consumption, so that heat is consumed as a chip unit when the laser element is lit and when the laser element is not illuminated. Constant power consumption,
The temperature difference on the chip between when the laser element is turned on and when it is not turned on is reduced as much as possible. Thus, a change in power consumed as heat from when the laser element 102 is not lit to when it is lit is reduced, and a decrease in laser output when the laser element 102 is lit can be prevented. In the semiconductor laser device 100 used in the present embodiment , the element unit 10
Although only one laser element 102 and one dummy laser element 103 on one chip are shown, as long as the idea of not changing the temperature of the laser chip 101 from non-lighting to lighting is realized, the laser The element 102 and the dummy laser element 103 may be plural.

[0014] Next, a second exemplary embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 5A, the semiconductor laser device used in the semiconductor laser system of this embodiment includes a plurality of element units 201 formed on a substrate 21 and a pin photodiode. FIG. 5B is an enlarged sectional view showing the element unit 201 indicated by the symbol P in FIG. The element unit 201 is formed by depositing an n-type current blocking layer on a p-type
Semiconductor device having an internal stripe structure in which a groove is etched (Appl. Phys. Lett. Vol. 40, 1)
March 1982, p. 312). FIG.
In (b), 21 is a P-type GaAs substrate and 22 is n-type.
The GaAs current blocking layer 23 is a stripe groove formed by a known photolithography technique.
The current blocking layer 22 is removed from the inside of 3 and this portion becomes a current path. 25 is a p-Ga _{1 -Y} Al _Y As clad layer, 26 is a Ga _{1 -Y} Al _X As active layer (0 <X <Y <
1), 27 _{n-Ga 1-Y Al Y} As cladding layer, 28
Is an n-GaAs gap layer, which forms a double-heterojunction type multi-layer crystal layer for laser operation, and applies a laser between the Au-Zn p-side electrode 29 and the Au-Ge-Ni laser-side n-side electrode 30. Has formed.

On the other hand, reference numeral 31 denotes an n ⁺ type semiconductor layer which forms a diode PN junction at a portion 32. 33 is a current blocking layer for electrically separating the laser layer and the diode layer, and 34 is an n-side electrode on the diode side of Au.

A control circuit for one element unit 201 is configured as shown in FIG.
Each element unit 201 of the semiconductor laser device 200 includes a laser element 202 and a diode element 203, and the pin photodiode 104 detects the amount of light emitted from the laser element 202. The configuration and operation of the other circuit portions are the same as those shown in FIG.
The operation can be easily understood if 03 is replaced with a diode 203. Therefore, in this reference example , when the laser element 202 is not lit (non-energized), the diode element 203 is energized to turn on and off the laser element 202 in chip units. The power consumption is kept constant, the temperature difference on the chip between when the laser element is lit and when it is not lit is reduced as much as possible, and the change in the optical output due to the heat generated when the laser is lit can be reduced.

A first embodiment of the present invention will be described with reference to FIG. In the embodiment of FIG. 8, a variable resistor 215 is connected in parallel to the diode element 203 of the reference example of FIG. Therefore, the current flowing through the diode element 203 changes depending on the resistance value of the variable resistor 215. Of course, if it is known that the resistance value may be a predetermined value, it is obvious that a fixed resistor may be used instead of the variable resistor 215. When the same amount of current flows through the laser element 202 and the diode element 203, the power consumed by the diode element 203 is larger than the power consumed by the laser element 202. If the chip is overheated when the lamp 102 is not lit, by reducing the resistance value of the variable resistor 215, the current flowing through the diode element 203 can be reduced and the respective power consumptions can be matched. In this case, the resistance value of the variable resistor 215 is obtained by the following equation.

W _L = V _L × I _L W _L : Power consumed by the laser element 202 W _D = V _D × I _D W _D : Power consumed by the diode element 203 I _L = I _D × I _R V _L : forward voltage of laser element 202 V _D = I _R × RV _D : forward voltage of diode element 203 I _L : laser current required to obtain target light quantity I _D : current flowing through diode element 203 when laser is off _R : Current flowing through resistor 216 when laser is off _R : Resistance value of resistor 216 From W _D = W _L R = V _D ² / (V _D −V _L ) / I _L [where V _D > V _L ] Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, unlike the embodiment of FIG. 8, the variable resistor 216 is connected in parallel to the laser element 202 instead of the diode element 203. Therefore, when the same amount of current is applied to the laser element 202 and the diode element 203, the variable resistor 215
If the power consumed by the diode element 203 is smaller than the power consumed by the laser element 102 and the chip cannot be heated when the laser element 102 is not lit, the variable resistor 215
, The current flowing through the laser element 202 can be reduced, and the power consumption of each can be made equal. In this case, the resistance value of the variable resistor 215 is obtained by the following equation. W _L = V _L × I _L W _L : Power consumed by the laser element 202 W _D = V _D × I _D W _D : Power consumed by the diode element 203 I _D = I _L × I _R V _L : Laser Forward voltage V _L = I _R × RV _{D of} element 202: Forward voltage I _L of diode element 203: Laser current required to obtain target light intensity I _D : Current flowing through diode element 203 when laser is off I _R : Laser off Current flowing through the resistor 216 at the time R: From the resistance value of the resistor 216, W _D = W _L , R = V _D × V _L / (V _L −V _D ) / I _L [where V _L > V _D ] , the contents of the embodiment of FIG. 8, 9, ginseng shown in FIG. 2
It is clear that it can be applied to the example . That is, the dummy laser element 103 or the laser element 1
02 may be connected in parallel with a variable resistor or a fixed resistor.

[0019]

As described above, the present invention relates to a semiconductor laser system using a semiconductor laser device provided with a laser element for emitting laser light on one chip and a heating element for heating the chip. When the laser element is not lit (non-energized), the control device of the semiconductor laser system switches from the laser element to the heating element for power consumption and energizes. This reduces the change in power consumption for each chip between when the laser element is turned on and when it is not turned on, thereby reducing the temperature difference on the chip between when the laser element is turned on and when it is not turned on. There is an effect that a reduction in laser light output during lighting can be reduced by preventing extra power consumption during lighting. In addition, if the control device includes a resistor that bypasses the current supplied to the heating element or the laser element, the amount of heat generated by the heating element or the laser element can be freely adjusted, and the laser light output at the time of lighting can be adjusted. The decrease can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a laser chip constituting one element unit of a semiconductor laser device used in a first reference example of a semiconductor laser system of the present invention.

FIG. 2 is a block diagram showing a first reference example of the semiconductor laser system of the present invention.

FIG. 3 is a block diagram showing the semiconductor laser driver of FIG. 2 in detail.

FIG. 4 is a timing chart showing the operation of the differential current switch of FIG.

FIG. 5A is a diagram showing a semiconductor laser device used in a second reference example of the present invention, in which a plurality of element units are formed. (B) is a block diagram showing one of (a) in detail.

FIG. 6 is a block diagram showing a second reference example of the present invention, and is a block diagram showing a case where one element unit of FIG. 5 is driven.

7 is a block diagram showing the semiconductor laser driver of FIG. 6 in detail.

FIG. 8 is a block diagram showing a first embodiment of the present invention.

FIG. 9 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 1,21 substrate 2,22 current blocking layer 3,23 stripe groove 5,25 cladding layer 6,26 active layer 8,28 gap layer 9,29 p-side electrode 10,30 n-side electrode 12,32 diode PN junction 13, 33 Current blocking layer 100, 200 Semiconductor laser device 101, 201 Element unit 102, 202 Laser element 103 Dummy laser element 203 Diode element 104, 204 Pin photodiode 105 Semiconductor laser driver 108 CPU

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanori Ishizu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hitoshi Machino 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-4-115585 (JP, A) JP-A-62-257184 (JP, A) JP-A-4-17784 (JP, A) JP-A-4-54029 (JP, A) A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50 B41J 2/44

Claims (6)

(57) [Claims] 1. A semiconductor laser device in which an element unit including a laser element and a heating element for heating the chip is formed on one chip, a constant current source, and the constant current source.
The current from the source is supplied to the laser element when the laser is turned on.
Supply to the heating element when the laser is off.
Semiconductor laser consisting of differential switches
A current flowing through the heating element connected in parallel with the heating element.
A resistor that bypasses part of the
Semiconductor laser system that. 2. A laser device and a chip on one chip.
An element unit consisting of a heating element for heating the
Semiconductor laser device, a constant current source, and the constant current
The current from the source is supplied to the laser element when the laser is turned on.
Supply to the heating element when the laser is off.
Semiconductor laser consisting of differential switches
The system is connected in parallel with the laser element and flows to the laser element.
Features a resistor that bypasses part of the current
Semiconductor laser system that. 3. The variable resistor externally adjustable.
3. The semiconductor laser system according to claim 1, wherein the semiconductor laser system is a resistor . 4. The device according to claim 1, wherein the device unit is provided on the chip.
4. The recording device according to claim 1, wherein a plurality of the light emitting elements are formed.
Mounting semiconductor laser system. 5. The heating element is separate from the laser element.
Do not emit laser light to the body in the normal laser light emission direction
4. A heating laser element formed as described above.
5. The semiconductor laser system according to claim 4. 6. The heating element is a diode element.
The semiconductor laser system according to claim 1 .