JPS61288478A - Semiconductor laser driving method - Google Patents

Abstract

PURPOSE:To enable to control driving of semiconductor lasers so as to uniform the light output irrespective of the interference between the laser lights, by lighting two or more semiconductor lasers sequentially, and by controlling each semiconductor laser so as to become a given light output. CONSTITUTION:When only the laser diode LD1 is driven, the switches SW1, SW3 are made off, and the switches SW2, SW4 are made on. Thus the transistor Tr1 may be conducted, and the collector current of the transistor Tr1 is flowed into the laser diode LD1, lighting only the laser diode LD1. The laser light from the laser diode LD1 may be received by the photo diode 1, and the laser light output of the laser diode 1 may be set by regulating the resistance value of the variable resistor VR. At this time, since the switch SW2 is conducted, the light current is fed back. Accordingly, the laser diode LD1 can be controlled so as to provide an uniform light output.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser driving method that is advantageously used in, for example, laser printers and high-speed processing of optical discs.

BACKGROUND ART A conventional semiconductor laser driving method uses one semiconductor laser and one P that receives laser light from the semiconductor laser.
The IN photodiode and the same parallax/semiconductor laser are controlled to have a constant optical output. In such a semiconductor laser driving method, only one semiconductor laser is used and a large optical output cannot be obtained, and therefore it is not suitable for laser printers or high-speed processing of optical discs. Therefore, it is conceivable to build two or more semiconductor lasers into one package to obtain a larger optical output, but when two or more semiconductor lasers are turned on at the same time, the laser beams interfere with each other and the light Current feedback makes it difficult to control the semiconductor laser to provide constant optical output.

Problems to be Solved by the Invention The purpose of the present invention is to solve the above-mentioned technical problems, to be able to use two or more semiconductor lasers, and to drive the semiconductor lasers to have a constant optical output. The present invention relates to a semiconductor laser driving method that makes it possible to drive a semiconductor laser.

Means for solving the problem: A light-receiving element that receives the laser light from the semiconductor laser, and a light-receiving element that receives the laser light from the semiconductor laser.The semiconductor lasers are sequentially driven so that each semiconductor laser has a predetermined optical output. 1. A method for driving a semiconductor laser, comprising: means for controlling the semiconductor laser so as to control the semiconductor laser.

Function According to the present invention, it is possible to drive two or more semiconductor lasers so that each has a constant optical output.

Example The drawing is an electrical circuit diagram of an embodiment of the present invention.

Electrical power 11Vcc (for example +5V) is line! 1, resistor R1, transistor Tri, resistor R2, laser diode LDI, and line! It is grounded through a series circuit with 2. Power supply VCC is also a line! 1 and resistance R
3, a transistor Tr2, a resistor R4, a laser diode LD2, and a line 12 in series. Laser diode LD1. Each laser beam from the LD 2 is received by a PIN photodiode 1 (hereinafter referred to as a photodiode). The cathode side of photodiode 1 is line 3 to line! 2, and its 7 node side is connected to line J! from line No. 4 through variable resistor VR. 5, the power supply Vε[(for example -5v
). Photodiode 1 and variable resistor VR
The connection point 2 in the middle of the line 14 connecting the
T ) 3 is connected to the base of capacitor C
1 to line 15. The input side of the field effect transistor 3 is connected to the power supply Vc c II line from the line through the resistor R5! 1, and the drain side is connected to the power supply ■E through the Zener diode 4.
EgA's line J! Connected to 5. Fin between field effect transistor 3 and resistor R5! The connection point 7 of 6 is grounded through a parallel circuit of a changeover switch SW1 and a capacitor C2. Further, the connection point 18 between the connection point 7 and the capacitor C2 is connected to the base of the transistor TRI.

Line 4 between photodiode 1 and variable resistor VR
The connection point 2 is also connected to the base of the field effect transistor 8 via the changeover switch SW3, and is also connected to the power supply ■εE' (line ! of II) via the capacitor C°3.
Connected to 5. The source side of the field effect transistor 8 is connected from the line node to line node 1 on the power supply VCC side via a resistor R6, and the drain side is connected to line node 5 on the power source ■εε side via a Zener diode 10. . The connection point 11 of the line 77 between the field effect transistor 8 and the resistor R6 is connected to the base of the transistor T'2, and is also grounded through a parallel circuit of the changeover switch SW4 and the capacitor C4.

A semiconductor laser driving method according to the present invention will be explained with reference to Table 1 below.

(Leaving space below) Table 1 First, when moving only the laser diode LDI, the changeover switches SWI and SW3 are shut off, respectively, and the changeover switches SW2... Each SW4 is made conductive. As a result, the transistor Tri becomes conductive, and the transistor Tr
A collector current of i flows through the laser diode LDI, so only the laser diode LDI lights up.

The laser light from the laser diode LDI is received by the photodiode 1, and the resistance value of the variable resistor VR is adjusted to set the output of the laser light from the laser diode LDI. At this time, since the changeover switch SW2 is conductive, the photocurrent is fed back, and thereby the laser diode LDI is controlled to have a constant optical output.

Next, after setting the optical output of the laser diode LDI, the changeover switches SWI and SW3 are turned on, respectively, and the changeover switches SW2. When SW4 is cut off, the transistor Tr2 becomes conductive, the collector current of the transistor Tr2 flows to the laser diode LD2, and only the laser diode LD2 lights up. At this time, the laser diode LDI is not lit, and the optical output of the laser diode LD2 is controlled to be the optical output determined by the variable resistor VR. At this time, since the changeover switch SW3 is conductive, the photocurrent is fed back, and thereby the laser diode LD2 is controlled to have a constant optical output. In this way, the changeover switches SW1 to SW4
By switching each laser diode LDI,
The LD2 can each obtain a constant optical output based on the set value of the variable resistor VR.

Next, the laser diode LD1. Turn on LD2 together,
To obtain large optical output, selector switch SW1
~ SW4 may all be set to the cut-off state. The laser beams from the laser diodes LDI and LD2 interfere with each other and are received by the photodiode 1, but when the changeover switch SW2 is turned on.

Since vSW3 is disconnected, the laser diode LD
1. No photocurrent is fed back to the LD2. Therefore, the laser diodes LDI, LD2
is driven and controlled with a constant optical output set by a variable resistor VR.

In this way, even if the laser diodes LDI and LD2 are built into one package and the light is received by one photodiode 1, the laser beams can be used regardless of whether the laser beams interfere with each other or not. It becomes possible to drive and control the diodes LDI and LD2 with constant optical output.

In the embodiment, two laser diodes LD1, LD
Although a large optical output can be obtained by using two laser diodes, the present invention is not limited to this, and a configuration in which two or more laser diodes are used to obtain a larger optical output may be used. Even with this configuration, the photodiode 1
Since only one variable resistor VR and one variable resistor VR are required, high costs can be prevented.

The semiconductor laser driving method according to the present invention can be used not only for high-speed processing of laser printers and optical discs, but also for a wide range of technical fields such as medical equipment.

Effects As described above, according to the present invention, two or more semiconductor lasers are sequentially turned on and controlled so that each semiconductor laser has a predetermined optical output, so that the mutual interaction of laser beams is controlled. It becomes possible to drive and control the semiconductor laser so that its optical output remains constant regardless of interference.

[Brief explanation of the drawing]

The drawing is an electrical circuit diagram of an embodiment of the present invention. 1... PIN photodiode, 3, 8... field effect transistor, Tri, Tr2... transistor,
LDI, LD2...Laser diode, VR...Convertible switch

Claims (1)

[Claims] A plurality of semiconductor lasers, a light receiving element that receives laser light from the semiconductor lasers, and means for sequentially driving the semiconductor lasers so that each semiconductor laser has a predetermined optical output. A method for driving a semiconductor laser, comprising: