JPH029026A - Semiconductor laser driving device - Google Patents

Abstract

PURPOSE:To eliminate the need of the separate detection of each optical output, to relax the positioning accuracy and to improve the mass-producing property by receiving laser beams from plural pieces of light sources in a lump by a two-division photodetector, and calculating an optical output signal, and detecting separately optical outputs from each light source. CONSTITUTION:A front laser luminous flux from two pieces of laser light sources of a semiconductor laser array 6 is divided into two by a beam splitter 20, and one of them is received in a lump by a two-division photodetector 22. Subsequently, an optical output signal passes through current/voltage converters 23, 24 and processed by an arithmetic circuit means having differential amplifiers 25, 27 and amplifiers 26, 28 and 29, the corresponding output of the detector 22 corresponding to a front light 12b is calculated as the product of a difference output of the transducers 23, 24 and a proportional constant K2 corresponding to an amplification factor of the amplifier 28, and in the same way, the corresponding output of the front light 12a is calculated and optical outputs of each light source are detected separately. Next, based on the detected output, the intensity of a laser light from each light source is adjusted so as to be made constant through driving circuits 30a, 30b. According to such constitution, it is unnecessary to detect separately each optical output, and the constitution of an optical system is simplified.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor laser driving device, and more specifically, it is used as a light source for information recording/reproducing devices that optically record and reproduce information. The present invention relates to a driving device for a semiconductor laser, particularly a semiconductor laser having a plurality of light emitting sources.

[Conventional technology]

FIG. 5 shows a conventional semiconductor laser driving device described in, for example, Japanese Unexamined Patent Publication No. 60-263349, which mainly consists of a light emitting section (1), a light receiving section (2), and a printed wiring board (3). First, the light emitting unit (1) has a header (5) attached as a heat sink on a metal substrate (4), and this header (semiconductor laser array (6) consisting of two semiconductor laser light sources on five planar upper end faces). ) is attached to the center hole (4a) of the metal substrate (4).A cylindrical condensing lens (7) is fitted and attached to 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 eye (6) via a connection @ (not shown). This first stem (8) also extends below the metal substrate (4) through a through hole (9a) filled with a glass filler (9) of the metal substrate (4), and extends downwardly through the printed wiring. Board (3) K is fixed.

The package (10) is fixed to the metal substrate (4) by bonding a glass plate (11) to its center hole (10a) so as to cover the header (5). Then, from the two semiconductor laser light sources of the semiconductor laser array (6), forward light (12a) (12b) and backward light (13a) (1
3b) is emitted. The forward light (12a) (12b) is irradiated onto the information recording medium, thereby recording and reproducing information. Further, the rear lights (13a) (13b) are used to control the light output of the front lights (12a) (12b), as will be described later.

Next, the light receiving section (2) has a pair of photodetectors (15a) (15b) embedded inside a transparent block (14). Three second stems (16) protrude from both ends of the transparent block (143) (one not shown).

This second stem (16) has an inner end connected to the photodetectors (15a) (15b) inside the transparent block (14), and an outer end connected to the printed wiring board (3).
) is installed.

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

In the above configuration, the center hole (4a) of the metal substrate (4) of the light emitting part (1) and the through hole (
A pair of photodetectors (15a) (15b) of the light receiving section (2) is positioned at a position corresponding to 3a), and the backward light (13a') emitted from the semiconductor laser array (6)
(13b) are separated by a cylindrical condensing lens (7), and are separately incident on photodetectors (15a) and (15b) to be focused. Therefore, the semiconductor laser array (6)
Front light (12a) emitted from each semiconductor laser light source of
The control of the light output of (12b) is controlled by the rear light (13a) (13
b) is achieved by operating a drive circuit (not shown) for each semiconductor laser light source using the output signal of a pair of photodetectors (15a>(15b)) that receive light.

[Problem to be solved by the invention]

Since the conventional semiconductor laser driving device is configured as described above, the photodetectors (15a') (15b)K rear light (
13a) (13b) In order to build up the light, the coming lens (
7) is extremely difficult to position within the narrow interior of the package (10), which poses a problem in that mass production is significantly lacking.

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

[Means to solve the problem]

A semiconductor laser drive device according to the present invention receives a plurality of forward lights from a plurality of semiconductor laser light sources at once.
A split photodetector is provided, and the light output from a plurality of semiconductor laser light sources is detected separately by calculating the light output signal from the two-split photodetector.

[For production]

In this invention, since detection of the optical output of a plurality of semiconductor laser light sources is performed by receiving a plurality of forward lights at once with a two-split photodetector, it is necessary to separate and detect a plurality of light beams. do not have.

〔Example〕

Fig. 1 shows an embodiment of this invention, and in the figure, symbols (4A) (5) (6) (8a) constituting one light emitting section (17) are shown.
) (8b) (9) (9a) (10) (10a) (11)
and the forward light (12a) of the semiconductor laser array (6) (
12b) is similar to that in FIG. The connection lines (18a) and (18b) supply current to individually operate the plurality of light sources of the semiconductor laser array (6), and one end connects the semiconductor laser array (6) and the other end connects the first stem ( 8a) and (8b), respectively.

The collimator lens (19) provides front light (12a) (12b)
) into a parallel beam of light. The beam splitter (20) splits the parallel beam into two. The forward light (12a) (12b) transmitted through the beam splitter (20) is guided toward an information recording medium (not shown) such as an optical disk, and is used for recording and reproducing information. On the other hand, the forward light (12a) (12b) reflected by the beam splitter (20) enters the two-split photodetector (22) via the lens (21). Current-voltage converters (23) and (24) convert the output signal of the two-split photodetector (22) into a voltage signal. The differential amplifier (25) has 'f! L current voltage converter (23”1 (24)
output is connected. In addition, the amplifier (26) has 1
The output of the current voltage converter (24) is connected. Further, the output terminal of the amplifier (26) is connected to the addition input terminal of the differential amplifier (27). On the other hand, the differential amplifier (25
) is connected to the next stage of the amplifier (28), and the output end of the amplifier (28) is connected to the amplifier (29) and the laser drive circuit (33b) K, respectively. Amplifier (29
) is connected to the subtraction input terminal of the differential amplifier (27). The output end of the differential amplifier (27) is connected to the laser drive circuit (30a). Laser drive circuit (3
The output ends of 0a) and 30b are connected to stems 8a and 30b, respectively.
8b).

Next, the operation will be explained. Semiconductor laser array (6)
In the plurality of light sources, the light source on the connection line (18a) side is LDa + the light source on the connection i (18b) side is LDb,
Let the respective optical outputs be Pa and Pb. Further, the operation of the two-split photodetector (22) and the output signal calculation circuit section of the two-split photodetector (22) will be explained with reference to FIG. In Fig. 2, the optical spora) (31a) is the forward light of LDa (
12a), and the light spot (31b) corresponds to the front light (12b) of LDb. Note that the broken line (33) is a straight line connecting the centers of the light spots (31a) (31b), and the light receiving surfaces (22a) (22) of the two-split photodetector (22).
The dividing line (22c) in b) forms a certain angle with K. Tas is the power transmission rate of the forward light (12a) from LDa to the light receiving surfaces (22a) and (22b), respectively.
, Ta2m or I, the power transmission rate from Db to the light receiving surfaces (22a) and (22b) of the forward light (12b) is Tb1. Tb2 (0< Ta1.Ta
z, Tbt, Tbz < 1).

When LDa and LDb simultaneously emit light at Pa and Pb, respectively, the output voltage signals P of the current-voltage converters (23) and (24).11. In general, the following relational expression holds true for and P2.

P1= (Ta1・Pa + Tbt*Pb)*K
αa Kβa(1)Pg = (Ta2@Pa
+ Tbz*Pb) * Kα * Kβ
(2) In equations (1) and (2), Kα is the light-to-current conversion efficiency of the photodetector, βa in equation (1) is the current-voltage conversion efficiency of the current-voltage converter (23), and equation (2) pb is the current-voltage conversion efficiency of the current-voltage converter (24). I'll leave it here. P 1' and P 2/ are the photodetector light receiving surface (2
2a) is the input optical signal to (22b), which is converted into (1)
Substituting into formula (2), Pl'= T3t a Pa + Tbt * P
b (5) Pz'= Ta2@Pa + T
bz @ Pb (can be expressed as 61. In the above equation (31 (41), Kβ=, βa=, p
b, and the above formula (51 (61), Tax −T
a2, and by performing the calculations (5) - (6), Pl' - P2' = (Tbt - Tbz)φpbT
b1 - Tbz = Kz ・ (Pt - P2) (7), and LDb
The optical output pb of is determined by the proportionality constant 2 and the current-voltage converter (2
3) and the output signal P2 of the current-voltage converter (24). Therefore, regardless of the optical output Pa of LDa.

The optical output pb of LDb can be detected, and the laser drive circuit (30
By b), the optical output pb of the LDb can be controlled to a constant value.

The next K, (KsIIP2 − K2・pb according to equations 71 and (2), and the optical output Pa of the LDa is determined by the proportionality constant "eK12", the output signal pb of the amplifier (28), and the current-voltage converter (
24) is detected by calculating the output signal P2. Therefore, the amplification degrees Ks and Kg of the amplifiers (26) and (29) are adjusted to the values of (in (11)), respectively, and the calculation is performed using the differential amplifier (27). Pa can be detected, and the laser drive circuit (30a)
The optical output Pa of Da can be controlled to a constant value.

By the above calculation, the optical outputs of the light sources LDa and Lpb of the semiconductor laser array (6) can be detected separately and driven independently.

In the above embodiment, the condition is Ta1=Ta2 Tb1 @Tbz, but even if TaI Tbt holds, under the conditions of equations (12) and (13), current-voltage conversion βa and βb are the current-voltage conversion efficiencies of the devices (23) and (24).

Ta1IIKβ3 = Ta2-/b-” (15)
Either set it so that it satisfies the relational expression, or, more precisely, K
/a=βb, current-voltage converter (23) and amplifier (
25), insert an amplifier with amplification degree KO between
If KO is adjusted so that o=Tax (16) holds true, the same effects as in the above embodiment can be achieved.

Furthermore, 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 placed close to each other within the same light emitting section (17) is used. Good too.

Further, in the above embodiment, a beam splitter (20) was used in order to receive the forward light (12a) (12b) with the two-split photodetector (22), but the configuration shown in FIG. 3 as another embodiment is shown in FIG. It may be. In FIG. 3, the light emitting part (17
), collimator lens (19), forward light (12a) (1
2b), the lens (21) and the second photodetector (22) are the same as in FIG.

The beam shaping prism (34) disposed on the output side of the collimator lens (19) refracts and transmits the forward light (12a) (12b) at its slope (34a'l), so that the beam shaping prism (34) has an originally elliptical cross-sectional intensity. The beam shaping prism (34) acts to convert the light beam of the semiconductor laser showing a distribution into an isodirectional cross-sectional intensity distribution Kf.
), a lens (21) and a second photodetector (22) are sequentially arranged in the reflection direction of the slope (34a) to detect the forward light (12a) ( 1
By receiving and detecting light 2b), the same effect as the embodiment shown in FIG. 1 can be achieved.

Further, in each of the above embodiments, the forward light (12a) (1
2b'l is converged and received by the two-split photodetector (22), but in another embodiment, as shown in FIG. The light may be received by a split photodetector (22).

〔Effect of the invention〕

As described above, the present invention provides a two-split photodetector that collectively receives a plurality of forward lights from a plurality of semiconductor laser light sources, and of the two detection signals from the two-split photodetector, The light outputs of the plurality of semiconductor laser light sources are detected separately by means of matching the components from one of the plurality of semi-integrated laser light sources and by means of calculating the output signals from the two light receiving surfaces. This eliminates the need for an optical system for separating a plurality of light beams, and eliminates the need for high precision. This has the effect of providing an inexpensive and highly productive device.

[Brief explanation of the drawing]

Fig. 1 is an optical path diagram of one embodiment of this invention, Fig. 2 is a connection diagram for explaining the operation of the one shown in Fig. 1, and Figs. 3 and 4 are partial optical path diagrams of other embodiments. , FIG. 5 is a side sectional view of a conventional semiconductor laser driving device. (6) -- Semiconductor laser array, (12a) (12b)
...Front light, (20)...Beam splitter (optical means), (22)...Two-split photodetector, [(23) (24
)・Fist current voltage converter, (25)(27)・・Differential amplifier, (2i(28)(29)−・amplifier,]φ・Operation circuit means. In each figure, the same reference numerals are the same − or a corresponding portion.

Claims (1)

[Claims] A semiconductor laser comprising a plurality of semiconductor laser light sources, an optical means for dividing a plurality of forward lights of the plurality of semiconductor lasers into two at an arbitrary ratio, and the plurality of forward lights divided into two by the optical means. a two-split photodetector that collectively receives one of the light beams including the two-split photodetector, and a light output signal detected by the two-split photodetector that matches the light output signal of one of the plurality of semiconductor laser light sources. and arithmetic circuit means for detecting the respective optical outputs of the plurality of semiconductor laser light sources based on the optical output signals detected by the two-split photodetector. Device.