JPH0279483A - Semiconductor laser driving device - Google Patents

Abstract

PURPOSE:To save the locating process for a condenser lens in a narrow package and obtain a semiconductor laser drive device excellent in mass producibility by furnishing a light sensor which in lump receives the emitted beams of light from a plurality of light sources, installing a laser driving means to light up only one light source one by one and put off the others, and allowing the light sensor to sense the output power of light source one by one. CONSTITUTION:Connection wires 18a, 18b supply current to operate a plurality of light sources of a semiconductor laser array 6 one after another. A light sensor 19 is arranged on a heater 5 so a to receive back lights 13a, 13b, and a photo-power signal of the array 6 is sensed. No.2 stem 20 senses current signals from this light sensor 19. A photo-power monitor signal sensed by the light sensor 19 is the sum of back lights 13a, 13b, and individual photo-powers can not be sensed. While photo-power at different spots are put off one after another, other light-intensity are sampled, and the output power of each laser is sensed. There is no need to sense a plurality of optical fluxes separated, which omits the locating process for a condenser lens, and a semiconductor laser drive device cheap and with ample mass producibility will be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor laser driving device, and more particularly, to a semiconductor laser used as a light source in an information recording/reproducing device that optically records and reproduces information. The present invention relates to a laser, and particularly to a semiconductor laser driving device having a plurality of light emitting sources.

[Conventional technology]

FIG. 5 is a diagram showing a conventional semiconductor laser driving device described in, for example, Japanese Patent Application Laid-Open No. 60-263349. As shown in the figure, this device mainly includes a light emitting section 1, a light receiving section 2,
It consists of a printed wiring board 3.

The light emitting unit 1 is mounted on a metal substrate 4 as a heat sink.
is attached to the flat upper end surface of the header 5.
A semiconductor laser array 6 consisting of two semiconductor laser light sources is attached. A cylindrical condensing lens 7 is fitted into the center hole 4a of the metal substrate 4. There are three first stems 8, but one is not shown. This first stem 8 is connected to each semiconductor laser light source of the semiconductor laser array 6 via connection lines (not shown).

Further, this first stem 8 extends below the metal substrate 4 through a through hole 9a filled with a glass filler 9 of the metal substrate 4, and is fixed to the printed wiring board 3. The package IO is fixed to the metal substrate 4 with a glass slope 11 pasted to its center hole 1Oa so as to cover the header 5. Then, the two semiconductor laser light sources of the semiconductor laser array 6 emit forward lights 12a, 12b and backward lights 13a, 13b, respectively. Front lights 12a, 12b
is irradiated onto the information recording medium, thereby recording and reproducing information. Also, a rear light 13a.

13b is used to control the light output of the forward lights 12a and 12b, as will be described later.

The light receiving unit 2 includes a pair of photodetectors 1 inside a transparent block 14.
5a and 15b are embedded. Three second stems 16 protrude from both ends of the transparent block 14 (one stem is not shown). The second stem 16 has its inner end connected to the photodetectors 15a and 15b inside the transparent block 14, and its outer end attached to the printed wiring board 3.

The printed wiring board 3 is provided with a through hole 3 a corresponding to the center hole 4 a of the metal substrate 4 .

Next, the operation will be explained.

In the above configuration, the center hole 4 of the metal substrate 4 of the light emitting part 1
A pair of photodetectors 15a, 15b of the light receiving section 2 are positioned at positions corresponding to the through holes 3a of the printed wiring board 3, and the rear lights 13a, 13b emitted from the semiconductor laser array 6 are detected by the cylindrical The forward lights 12a, 12b are separated by the condensing lens 7 and are separately focused on the photodetectors 15a, 15b, thereby controlling the optical output of the forward lights 12a, 12b emitted from each semiconductor laser light source of the semiconductor laser array 6. This is achieved by operating a drive circuit (not shown) that drives each semiconductor laser light source using output signals from a pair of photodetectors 15a, 15b that receive rear lights 13a, 13b.

[Problem to be solved by the invention]

Since the conventional semiconductor laser driving device is configured as described above, the rear lights 13a and 1 are transmitted to the photodetectors 15a and 15b.
3b, the condensing lens 7 is connected to the pan cage 10 to condense the condensing lens 7.
It is very difficult to position the device in the narrow interior of the device, and there is a problem in that it is extremely difficult to mass-produce.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a semiconductor laser driving device that can be easily mass-produced and can avoid the step of positioning a condensing lens inside a narrow pancage.

[Means to solve the problem]

The semiconductor laser driving device according to the present invention includes a photodetector that collectively receives light emitted from a plurality of semiconductor laser light sources, and only one light source among the plurality of semiconductor laser light sources is turned on sequentially, A laser drive means for driving all other light sources to be turned off is provided, and the light detector is configured to sequentially detect the optical power of each light source that is lit.

[Effect]

In this invention, a photodetector that collectively receives light emitted from a plurality of semiconductor laser light sources, and one light source among the plurality of semiconductor laser light sources is turned on sequentially, and all other light sources are turned on. Since the light source is provided with a laser drive means that drives the light to turn off, and the light detector is configured to sequentially detect the optical power of each light source that is lit, there is no need to separate and detect multiple light beams. , the step of positioning the condenser lens can be omitted.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing a semiconductor laser driving device according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG. , 8b is the first stem. Connection line 18a
, L8b supplies current to separately operate the plurality of light sources of the semiconductor laser array 6, and one end is connected to the semiconductor laser array 6, and the other end is connected to the first stems 8a and 8b, respectively. The photodetector 19 is the rear light 13a.

13b, and is arranged on the header 5 to detect the optical power monitor signal of the semiconductor laser array 6. The second stem 20 is a detection signal (current signal) of the photodetector 19.
The purpose is to detect

The current-voltage converter 21 converts the current signal of the photodetector 19 into a voltage signal. The output of the current-voltage converter 21 is connected to the sample-and-hold circuit 22 .

The output of the sample hold circuit 22 is connected to the switch circuit 23, and a plurality of output terminals of the switch circuit 23 are connected to laser drive circuits 24a and 24b, respectively. The output terminals of the laser drive circuits 24a, 24b are connected to the first stems 8a, 8b, respectively. Timing signal 25 output from timing control circuit 25
a to 25d are laser drive circuits 24a, 24b, respectively.
It is input to a switch circuit 23 and a sample hold circuit 22.

Next, the operation will be explained using FIGS. 1 and 2.

FIG. 2 is a timing chart showing the operation of this embodiment. In particular, a plurality of focused spots formed on the information recording medium by the forward lights 12a and 12b are positioned on the same trunk in the information recording direction, and When performing a real-time monitoring function in which information is recorded in a leading focused spot formed by the forward light 12a, and immediately reproduced in a subsequent focused spot formed by the forward light 12b to detect recording errors. It shows.

In this real-time monitor function, in principle, the subsequent playback spot is always lit with a constant power regardless of recording or playback, and from this spot the playback signal,
Focusing error signal.

It is only necessary to detect the tracking error signal and to light up the preceding recording spot with the recording power according to the recording signal only during recording. However, in order to improve recording characteristics, it is desirable to detect focusing error signals and tracking error signals from recording spots, and also to detect address signals on tracks with multiple spots to confirm that they are on the same track. Since it is necessary,
It is desirable for the recording spot to be lit with the same optical power as the reproduction spot other than when recording.Since it is more than 0, the preceding recording spot has a difference between the bottom power during reproduction and the optical power during recording. Lights up with peak power.

By the way, since the optical power monitor signal detected by the photodetector 19 is the sum of the backward lights 13a and 13b, the individual optical powers cannot be detected.

Therefore, in this embodiment, as described below, while the optical power of each spot is sequentially turned off, the optical power of the other spot is sampled and detected, thereby detecting the optical power of each laser. In FIG. 2, part A is a data part in which information is recorded, and part B is a part of a sector in which track address signals and the like are recorded. The 0 part is a no-signal part, and since such a part exists, although it is small, in a normal information recording medium, in this embodiment, this period is used to sample the optical power of each spot. At the sampling time SI of the reproduction spot, the recording spot that is lit is temporarily turned off using the bottom power.

As a result, only the optical power component of the reproduction spot is detected by the photodetector 19, and this is sampled by the sample and hold circuit 22. The switch circuit 23 is turned on to the side of the laser drive circuit 24b related to the reproduction spot in synchronization with the sampling time SI, and the monitor signal of the sampled optical power is input, and the laser drive circuit 24b changes the optical power of the reproduction spot. is controlled so that it is constant.

Next, at sampling time S2 of the recording spot, the reproduction spot is once turned off. This time, only the bottom power component of the recording spot is detected by the photodetector 19 and sampled by the sample and hold circuit 22. The switch circuit 23 is turned on to the laser drive circuit 24a side related to the recording spot in synchronization with the sampling time St, and is controlled so that the bottom power of the recording spot is constant. The above operation is performed for each sector, and the controlled optical power is held at a constant value until the next sampling. Also, a laser drive circuit 24a.

24b, switch circuit 23, sample hold circuit 22
The operation timing of is controlled by timing signals 25a to 25d output from the timing control circuit 25.

In the above description, the peak power of the recording spot is not controlled, but this can be done, for example, as follows.

FIG. 3 is a timing chart showing the operation of another embodiment of the present invention which also controls the peak power of the recording spot. The operation at the sampling times Sr and St is the second
This is the same as the one shown in the figure, and in the operation according to this embodiment, a sampling time S for the recording spot is further provided, and the reproduction spot is temporarily turned off again, and at the same time, the recording spot is lit in pulses unrelated to the recorded information. As a result, only the peak power component of the recording spot is detected by the photodetector 19, so that the peak power of the subsequent recording pulse can be controlled in the same manner as described above.

The real-time monitoring operation in this embodiment has been described above, but in this embodiment, the operation as shown in FIG. 4 can also be performed. FIG. 4 is a timing chart showing another operation of this embodiment, in which override is used to record new information while erasing old information using a rewritable medium such as a magneto-optical recording medium or a phase change recording medium. Indicates when the function is executed. In this case as well, a plurality of focused spots are positioned on the same track in the information recording direction, the preceding focused spot formed by the forward light 12a performs erasing, and the subsequent focused spot formed by the forward light 12b is The erasing spot, which immediately performs recording, is lit in a DC manner with a power approximately equal to the peak power of the recording spot. Similar to the explanation in FIG. 2, at the sampling time S1 of the recording spot, the bottom power of the recording spot is detected by temporarily turning off the erasing spot that is lit at the erasing power, -, and then the bottom power of the recording spot is detected. At the sampling time S2, the erasing power is detected by turning off the recording slot 7) which is lit at the bottom power.

Furthermore, if the peak power of the recording spot is also to be detected, the operation described in FIG. 3 may be performed.

Furthermore, even when executing the override real-time monitor function that forms three spots on a rewritable medium and performs erasing, recording, and playback at the same time, only one spot lights up in sequence as described above, and the other spots turn on. The optical power of the semiconductor laser can be controlled by driving the semiconductor laser so that it is turned off and detecting the optical power.

It goes without saying that the present invention can also be applied to a parallel recording/reproducing function in which multiple spots are positioned on adjacent tracks and recording/reproducing is performed simultaneously on multiple trunks.

In the above embodiment, the photodetector 19 is built into the light emitting section 17 and receives the rear lights 13a and 13b all at once.
2b may be used.

Further, in the above embodiment, an array structure is shown as a plurality of semiconductor laser light sources, but a hybrid type in which a single light emitting source is disposed close to each other within the same light emitting section may be used.

〔Effect of the invention〕

As described above, according to the present invention, a semiconductor laser driving device includes a photodetector that collectively receives light emitted from a plurality of semiconductor laser light sources, and a photodetector that receives light emitted from a plurality of semiconductor laser light sources sequentially. and a laser driving means for driving so that only the light source is turned on and all other light sources are turned off,
Since the above photodetector is configured to sequentially detect the optical power of each lit light source, there is no need to separate and detect multiple beams of light, and the process of positioning the condensing lens can be omitted, making mass production possible at low cost. This has the effect of making it possible to obtain a semiconductor laser drive device with excellent performance.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a semiconductor laser driving device according to an embodiment of the present invention, FIG. 2 is a timing chart diagram showing an example of operation in an embodiment of the present invention, and FIGS. 3 and 4 are diagrams according to the present invention. FIG. 5 is a timing chart diagram showing another example of the operation in one embodiment of the present invention, and FIG. 5 is a configuration diagram showing a conventional semiconductor laser driving device. 6 is a semiconductor laser array; 12a and 12b are laser front lights; 13a and 13b are laser rear lights; 19 is a photodetector; 21 is a current-voltage converter; 22 is a sample and hold circuit; 23 is a switch circuit; 24a; 24b is a laser drive circuit, and 25 is a timing control circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A semiconductor laser made up of a plurality of semiconductor laser light sources; a photodetector that collectively receives a plurality of emitted lights from the plurality of semiconductor lasers; It is equipped with a laser drive means for driving so that only the light source is turned on and all other light sources are turned off, and a sample-hold circuit that sequentially samples and holds the outputs of the photodetectors that receive the emitted light while they are sequentially turned on. A semiconductor laser drive device characterized by: