JPS60213141A - Laser diode power control device - Google Patents

Abstract

PURPOSE:To control the oscillation power of each laser diode independently by oscillating each laser diode by a signal to which respectively different frequency is superposed. CONSTITUTION:Plural laser diodes 11-13 are unitedly formed on a stem 10 and respective diodes 11-13 are oscillated by modulators 21-23. Respective modulators 21-23 are modulated at frequency, e.g. 600MHz, 700MHz and 800MHz, extremely higher than that of recording/reproducing information. These superposed signals are detected by a photodetecting element arranged on the back of the laser diodes 11-13 and separated into respective frequency through filters 31-33. These separated signals are used to control the power of repective laser diodes 11-13. Thus, the power control of respective diodes 11-13 can be executed independently.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a laser diode (denoted as LD) as a light source for recording and reproducing information, such as a laser optical disc or a laser printer used for recording and reproducing information. Even under conditions, the luminous power changes due to temperature changes.

Therefore, a method is used in which a part of the laser light emitted backward is received by a light receiving element such as a solar cell or a photodiode, and the emitting power of the laser is kept constant so that the current flowing through the light receiving element is constant. It is being

In recent years, in order to record and reproduce information at high speed in optical discs and laser printers, a method of simultaneously irradiating multiple laser beams has been desired. In that case, it is convenient to integrate a large number of LDs into one chip. However, the laser light from such a one-chip multi-laser simultaneously contains light from many LDs, and the method of controlling the current flowing through the light receiving element described above does not allow the oscillation power of the laser light from each LD to be controlled independently. cannot be controlled.

OBJECTS OF THE INVENTION In view of the above drawbacks, the present invention provides means for independently controlling the oscillation power of each laser beam from a plurality of integrated laser diodes.

Structure of the invention A large number of laser diodes (LDs) are configured into one body,
Each LD is caused to oscillate with different frequencies superimposed on each other, and a light receiving element is provided to receive part or all of the laser light emitted forward or backward, and a signal of each superimposed frequency is extracted from the received light signal. The light emitting power of each LD is simultaneously and independently controlled to a constant value by separating the LDs so that their signal amplitudes are constant.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described in which three laser diodes (LDs) are integrated into one unit. In Figure 1, LDll, 12
．． 13 is formed on one stem jO, and each LD is modulated by modulators 21, 22, and 23 and oscillated. In the case of optical discs, the information to be recorded and reproduced is approximately 10&III, and higher frequencies, such as 600M+70
0WrL and 800WrL are superimposed to cause each LD to oscillate. As shown in FIG. 2, the light from each LD oscillates laser light forward and backward. Part or all of that light is received by a light receiving element such as a high-speed photodiode. In FIG. 2, a light receiving element 3o is installed to receive the rear laser beam. The received light signal is superimposed by the filters 31, 32, and 33 in FIG. 3 into a frequency signal S1. S2. S3
are separated and each signal amplitude A1. A2. Control A3 to be constant.

FIG. 4 shows the current and oscillation power characteristics δ of the KLD. A modulator (eg 21 in FIG. 1) modulates the current across the oscillation threshold current I, such as b).

The oscillation power at that time is represented by C. Since the light-receiving signal of the light-receiving element 3o is proportional to the oscillation power 〇, if the amplitude of the light-receiving signal (for example, A1 in FIG. 3) is made constant, the oscillation power amplitude can also be made constant. Since the frequencies b and C in Fig. 4 are much higher than the information frequency, they do not affect information reproduction, and are similar to the average value C of the oscillation power curve C.
It behaves as if it were regenerated with 0 power.

Since the light from multiple LDs does not interfere with each other, each L
If D is modulated at different frequencies, if a signal with a specific modulation frequency is extracted from the received light signal, it will represent the oscillation power of one LD out of many, and the power will be increased without affecting other LDs. can be kept constant, therefore, a large number of LD
power can be controlled simultaneously and independently.

Filters 31, 32, and 33 in FIG. 3 can be constructed of surface acoustic waves. Although the embodiment uses three LDs, as can be seen from the above description, the number of LDs is not limited.

As described in detail, according to the present invention, a large number of laser diodes (LDs) are integrated into one unit, and the oscillation laser power from each LD can be controlled simultaneously and independently.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a laser device in which three laser diodes (LDs) are integrated into one according to an embodiment of the present invention, and FIG.
The figure shows the arrangement of the oscillated laser light from each LD and the light-receiving element that receives a part of it in an embodiment of the laser diode power control device of the present invention, and Figure 3 is a block diagram of the main parts of the device. FIG. 4 is a diagram explaining the relationship between the modulation signal of the LD and the light emission power. 11.12.13... Laser diode, 2
1.22, 23...Modulator, 30...
Light receiving element, 31, 32, 33...filter.

Claims (1)

[Claims] When configuring a large number of laser diodes into one body and using each of the laser diodes simultaneously and independently,
Each LD is oscillated by superimposing different frequencies on each other, a part or all of each laser beam emitted forward or backward is received by one light receiving element, and a signal of each superimposed frequency is obtained from the received light signal. A laser diode power control device characterized in that the laser diode power control device simultaneously and independently controls each of the light emitting powers of the plurality of laser diodes so that the amplitude of each of the separated frequency signals becomes constant.