JPH07118085B2 - Semiconductor laser drive - Google Patents

Description

TECHNICAL FIELD The present invention relates to a semiconductor laser driving device, and more specifically, it is used as a light source for an information recording / reproducing device for optically recording / reproducing information. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, and more particularly, to a driving device for a semiconductor laser having a plurality of light emission sources.

[Conventional technology]

FIG. 5 shows a conventional semiconductor laser driving device disclosed in, for example, Japanese Patent Application Laid-Open No. 60-263349, which is mainly composed of a light emitting portion (1), a light receiving portion (2), a pudding and a wiring board (3). . First, in the light emitting part (1), a hedder (5) is mounted as a heat sink on a metal substrate (4), and a semiconductor laser array (6) composed of two semiconductor laser light sources is provided on a planar upper end surface of the hedder (5). ) Is installed. A cylindrical condenser lens (7) is fitted and mounted in the center hole (4a) of the metal substrate (4). There are three first stems (8), but one is not shown. The first stem (8) is connected to each semiconductor laser light source of the semiconductor laser array (6) via a connecting wire (not shown). In addition, the first stem (8) extends below the metal substrate (4) through the through hole (9a) filled with the glass filler (9) of the metal substrate (4), It is fixed to the printed wiring board (3). Package (10)
Attach a glass plate (11) to its center hole (10a),
It is fixed to the metal substrate (4) so as to cover the header (5). Then, front light (12a) (12b) and rear light (13a) (13b) are emitted from the two semiconductor laser light sources of the semiconductor laser array (6), respectively. Forward light (12a)
The information recording medium is irradiated with (12b), and information is recorded / reproduced thereby. The rear lights (13a) (13b) are used to control the light output of the front lights (12a) (12b) as described later.

Next, the light receiving section (2) is placed inside the transparent block (14).
A pair of photodetectors (15a) (15b) are embedded. Three second stems (16) are projected from both ends of the transparent block (14) (one is not shown). This 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 (3a) corresponding to the center hole (4a) of the metal substrate (4).

In the above structure, the central hole (4a) of the metal substrate (4) of the light emitting part (1) and the through hole (3) of the printed wiring board (3).
A pair of photodetectors (15a) (15b) of the light receiving part (2) are positioned at positions corresponding to (a), and backward light (13a) (13b) emitted from the semiconductor laser array (6) is positioned. Are separated by a cylindrical condensing lens (7), and are individually incident on the photodetectors (15a) and (15b) and focused. Therefore, the control of the light output of the front light (12a) (12b) emitted from each semiconductor laser light source of the semiconductor laser array (6) is controlled by the pair of photodetectors (reception light of the rear light (13a) (13b) ( 15a)
This is achieved by operating the drive circuit (not shown) of each semiconductor laser light source using the output signal of (15b).

[Problems to be Solved by the Invention]

Since the conventional semiconductor laser drive device is configured as described above, the backward light (13a) (1a) (1a) (1a)
It is very difficult to position the condenser lens (7) within the narrow space of the package (10) for condensing 3b), and there is a problem that mass productivity is remarkably lacking.

The present invention has been made to solve the above problems, and an object thereof is to avoid the step of positioning a condenser lens inside a narrow package and to obtain a semiconductor laser driving device with mass productivity.

[Means for Solving the Problems]

A semiconductor laser driving device according to the present invention collectively receives a plurality of forward lights from a plurality of semiconductor laser light sources.
A divided photodetector is provided, and the optical output signals from the two-divided photodetector are calculated to detect the optical outputs of a plurality of semiconductor laser light sources separately.

[Action]

In the present invention, the light outputs of the plurality of semiconductor laser light sources are detected by collectively receiving a plurality of forward lights by the two-split photodetector, so that a plurality of light beams are separated and detected. No need.

〔Example〕

FIG. 1 shows an embodiment of the present invention. In the drawing, reference numerals (4A), (5), (6), (8a), (8b) constituting the light emitting section (17)
The forward lights (12a) and (12b) of (9), (9a), (10), (10a) and (11) and the semiconductor laser array (6) are the same as those in FIG. The connection lines (18a) and (18b) supply currents for individually operating a plurality of light sources of the semiconductor laser array (6), one end of which is connected to the semiconductor laser array (6) and the other end of which is connected to the first stem (6). 8a) and (8b), respectively. Collimator lens (19)
a) Make (12b) a parallel light beam. Beam Splitter (20)
Divides the parallel light flux into two. Beam Splitter (20)
The forward light (12a) (12b) that has passed through is guided to the direction of an information recording medium (not shown) such as an optical disk and used for recording and reproducing information. On the other hand, the forward light (12a) (12b) reflected by the beam splitter (20) is reflected by the lens (2
It is incident on the two-division light detection supply (22) via 1). The current-voltage converters (23) (24) convert the output signals of the two-division photodetection supply (22) into voltage signals. The outputs of the current-voltage converters (23) (24) are connected to the differential amplifier (25). The output of the current-voltage converter (24) is connected to the amplifier (26). Further, the output terminal of the amplifier (26) is connected to the addition input terminal of the differential amplifier (27). On the other hand, an amplifier (28) is connected to the next stage of the differential amplifier (25), and the output end of the amplifier (28) is connected to the amplifier (29) and the laser drive circuit (33b), respectively. Amplifier (2
The output terminal of 9) 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 (30a)
The output ends of (30b) are connected to the stems (8a) and (8b), respectively.

Next, the operation will be described. Semiconductor laser array (6)
Of the multiple light sources, the light source on the connection line (18a) side is LD
Let a, the light source on the side of the connection line (18b) be LDb, and let the respective light outputs be Pa and Pb. In addition, a two-part photodetector (22) and two
The operation of the output signal arithmetic circuit of the split photodetector (22)
It will be described with reference to the drawings. In FIG. 2, an optical spot (31
a) corresponds to the front light (12a) of LDa, and the light spot (31b)
Corresponds to the front light (12b) of LDb. The broken line (3
3) is a straight line that connects the centers of the optical spots (31a) (31b), and forms an angle with the dividing line (22c) of the light receiving surfaces (22a) (22b) of the two-divided photodetector (22). There is. Forward light from LDa receiving surface of (12a) (22a) and to the light receiving surface of the power transfer rate of up to (22b), respectively Ta _1, Ta ₂ forward light or from LDb, (12b) (22a) and (22b) Power transfer rates of Tb ₁ and Tb ₂ (O <Ta ₁ , Ta ₂ , Tb ₁ , T
b ₂ <1).

When LDa and LDb are emitting light at Pa and Pb at the same time,
The output voltage signals P ₁ and P ₂ of the current-voltage converters (23) and (24), respectively, generally have the following relational expression.

P ₁ = (Ta ₁ · Pa + Tb ₁ · Pb) · Kα · Kβa (1) P ₂ = (Ta ₂ · Pa + Tb ₂ · Pb) · Kα · Kβb (2) (1) In the formula (2), Kα is the light Photo-current conversion efficiency of the detector, Kβa in the equation (1) is the current-voltage conversion efficiency of the current-voltage converter (23), and Kβb in the equation (2) is the current-voltage conversion efficiency of the current-voltage converter (24). . here And put. P ₁ ′ and P ₂ ′ are the input optical signals to the photodetector light receiving surfaces (22a) and (22b). Substituting these into Eqs. (1) and (2), P ₁ ′ = Ta ₁ · Pa + Tb ₁ · Pb (5) P ₂ ′ = Ta ₂ · Pa + Tb ₂ · Pb (6) In the above equations (3) and (4), K
It is assumed that β = Kβa = Kβb, and that in the above equations (5) and (6), it is adjusted so that Ta ₁ = Ta ₂ . This condition means that the optical output components of LDa detected in the output voltage signals P ₁ and P ₂ of the current-voltage converters (23) and (24) match each other. Therefore, by performing the operations of (5)-(6), However, Next, the light output Pb of LDb is detected as the product of the difference between the output signal P ₂ of the output signal P ₁ and the current-voltage converter of the proportional constant K ₂ and the current-voltage converter (23) (24). Therefore LDa's optical output P
The optical output Pb of the LDb can be detected regardless of a, and the optical output of the LDb can be controlled to a constant value by operating the laser drive circuit (30b) so that the optical output signal becomes constant.

Next, using equations (7) and (2) However, Therefore, the optical output Pa of LDa is proportional to the constants K ₁ and K ₁₂ , the output signal Pb of the amplifier (28) and the output signal of the current-voltage converter (24).
Detected by calculation of P ₂ . Therefore amplifiers (26) and (2
The optical output Pa of LDa can be detected by adjusting the amplification factors K ₁ and K ₂ in 9) to the values of equations (10) and (11), respectively, and performing the calculation with the differential amplifier (27). By operating the laser drive circuit (30a) so that the optical output signal becomes constant, the optical output of LDa can be controlled to a constant value.

By the above calculation, the light source of the semiconductor laser array (6)
The light outputs of LDa and LDb can be detected separately, and the light sources can be individually driven based on these detection signals.

In addition, in the above embodiment, as a condition However, Even Is satisfied, and under the conditions of formulas (12) and (13),
The current-voltage conversion efficiencies Kβa and Kβb of the current-voltage converters (23) and (24) are set so as to satisfy the relational expression Ta ₁ · Kβa = Ta ₂ · Kβb (15), or K
With βa = Kβb, the current-voltage converter (23) and the amplifier (2
Inserting an amplifier with amplification factor K ₀ between 5) and adjusting K ₀ so that Ta ₁ · K ₀ = Ta ₂ (16) holds, the current-voltage converter (23) and ( Since the optical output components of LDa detected in the output voltage signals P ₁ and P ₂ in 24) are the same, the same effect as that of the above-described embodiment is obtained.

Further, in the above embodiment, the plurality of semiconductor laser light sources have an array structure, but a hybrid type light source in which a single light emitting source is closely arranged in the same light emitting portion (17) may be used. Good.

In the above embodiment, the beam splitter (2) is used to receive the front light (12a) (12b) by the two-division photodetector (22).
Although 0) is used, the configuration of FIG. 3 shown as another embodiment may be used. In FIG. 3, the light emitting part (17), collimator lens (19), forward light (12a) (12b), lens (21), and second photodetector (22) are the same as those in FIG. is there. The beam shaping prism (34) arranged on the exit side of the collimator lens (19) has an originally elliptical cross section by refracting and transmitting the forward light (12a) (12b) at its slope (34a). It acts so as to convert the luminous flux of the semiconductor laser exhibiting the intensity distribution into an isotropic cross-sectional intensity distribution. In the slope (34a) of the beam shaping prism (34), in addition to the above-mentioned component that is refracted and transmitted, there is a component that is reflected by the slope (34a), so the lens (2
1), the second photodetector (22) is sequentially arranged, and the slope (34a)
By receiving and detecting the forward lights (12a) and (12b) reflected by (1), the same effect as that of the embodiment shown in FIG. 1 can be obtained.

Further, in each of the above embodiments, the forward light (12a) (12b)
The light is converged and received by the two-division photodetector (22). However, as another embodiment, as shown in FIG. The light may be received at (22).

[Advantages of the Invention] As described above, the present invention is an optical device that divides a semiconductor laser including a plurality of semiconductor laser light sources and a plurality of forward lights emitted from the plurality of semiconductor laser light sources into two at an arbitrary ratio. And a two-division photodetector for collectively receiving light on one side of the plurality of halved emission lights, the division line of which is received on the two-division photodetector. Two-divided photodetectors arranged so as to receive a plurality of spots at different ratios, respectively, and different lights of the plurality of semiconductor laser light sources based on the light output signals detected by the two-divided photodetectors. And a plurality of semiconductor laser light sources are individually driven based on the respective optical outputs detected by the arithmetic circuit means. No optical system to separate Therefore, new position accuracy becomes unnecessary. As a result, there is an effect that an inexpensive and highly productive device can be obtained.

[Brief description of drawings]

FIG. 1 is an optical path diagram of an embodiment of the present invention, FIG. 2 is a connection diagram for explaining the operation of FIG. 1, and FIGS. 3 and 4 are partial optical path diagrams of other embodiments. 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) …… 2-split photodetector, [(23) (24) …… current-voltage converter, (25) (27) …… differential amplifier, (26) (28)
(29) …… Amplifier,] ………… Computing circuit means. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A semiconductor laser comprising a plurality of semiconductor laser light sources, an optical means for dividing a plurality of forward light beams emitted from the plurality of semiconductor laser light sources into two at an arbitrary ratio, and the two. A two-division photodetector that collectively receives light on one side of the plurality of emitted light, and the division lines have different proportions of the plurality of spots received on the two-division photodetector. A two-divided photodetector arranged so as to receive light, 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-divided photodetector. And a plurality of semiconductor laser light sources are individually driven based on the respective optical outputs detected by the arithmetic circuit means. 2. The semiconductor laser driving device according to claim 1, wherein the optical means is a beam splitter. 3. The triangular prism arranged in the optical path of the plurality of emitted lights of the semiconductor laser so that the optical means converts the cross-sectional shape of the light flux of the plurality of emitted lights of the plurality of semiconductor lasers. Claim 1 characterized by
A semiconductor laser drive device as described in the paragraph.