JPH036512A - Light beam scanning device - Google Patents

Abstract

PURPOSE:To attain a continuous optical scan with a laser beam which has stable wavelength by providing a guiding means which guides the laser beam and a driving switching means which switches driving so that one of plural semiconductor lasers is put in operation. CONSTITUTION:A deflecting prism 6 guides the outgoing beams of the semiconductor lasers 1a - 1c so that they are made incident on a hologram lens 2 at a fixed incidence angle and is driven to rotate around the intersection of the projection directions of the respective projection beams of the semiconductor lasers 1a - 1c associatively with the switching operation of the driving switching means 4. Namely, one of the semiconductor lasers 1a - 1c is switched by the driving switching means 4 at specific intervals of times to be operated. For the purpose, the time intervals are so set that the driving of the semiconductor lasers 1a - 1c is switched before the temperature at which mode hopping is generated is arrived and then semiconductor lasers which are not in operation do not oscillate and a cooling period is provided, so that the temperature returns to the initial state. Consequently, the optical scan is attained by the laser beam with stable wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light beam scanning device that is used in a laser printer or the like and is equipped with a hologram lens.

[Conventional technology]

2. Description of the Related Art Conventionally, a light beam scanning device used in a laser printer or the like has been equipped with a polygon mirror to guide a laser beam to a predetermined position on a scanning surface. However, polygon mirrors are difficult to process and expensive, and require a large number of optical components, so as an alternative, research is being conducted on the use of hologram lenses, which can be constructed at low cost with fewer optical components. There is.

[Problems to be Solved by the Invention] However, in the conventional light beam scanning device described above, when a semiconductor laser is used as a light emitting means, as shown in FIG. The oscillation wavelength of the semiconductor laser changes to O53nm due to temperature changes.
A phenomenon called mode hopping, which deviates by several nanometers, occurs. In general, the diffraction angle of a hologram is determined by the wavelength of coherent light such as a laser beam, the angle of incidence on the hologram, and the hologram pitch. The position of the scanning line drawn by the scanning beam on the scanning plane shifts by about 0.4 nm per 0.1 nm shift in the wavelength of the beam emitted from the semiconductor laser.

Therefore, when a semiconductor laser is used in a high-precision linear scanner such as a laser printer, although the device can be constructed at low cost, there is a problem in that printing quality deteriorates. For this reason, in the past, methods for controlling the temperature of semiconductor lasers and wavelength stabilized lasers (DFB lasers) have been actively developed, but at present these methods are too costly and are not suitable for practical use.

[Means to solve the problem]

In order to solve the above problems, a light beam scanning device according to the present invention is a light beam scanning device including a light emitting device and a hologram lens that guides light emitted from the light emitting device to a predetermined position on a scanning surface. , the light emitting means is provided with a plurality of semiconductor lasers, and a guiding means guides the laser beams so that each laser beam emitted from the semiconductor lasers is incident on the hologram lens at a constant angle of incidence and position; The present invention is characterized by comprising a drive switching means for sequentially switching drive at predetermined time intervals so as to operate any one of the plurality of semiconductor lasers.

[For production]

According to the above configuration, the drive of any one of the plurality of semiconductor lasers is sequentially switched and operated at predetermined time intervals by the drive switching means, so that the semiconductor laser is operated before reaching the temperature at which mode hopping occurs. If the time interval of the switching operation in the drive switching means is set so as to switch the drive, the semiconductor laser which is not operating is given a cooling period without oscillating, and its temperature returns to the initial state. In this way, by sequentially switching the drive of the semiconductor laser before mode hopping occurs, optical scanning can be performed with a laser beam of a stable wavelength.

Further, even if the light emitting means is provided with a plurality of semiconductor lasers and the laser beams are emitted from different positions, these laser beams are incident on the hologram lens at a constant incident angle and position by the guiding means. Therefore, high accuracy can be maintained in optical scanning using a plurality of semiconductor lasers without causing any positional deviation in the scanning lines.

[Example 1] The first example of the present invention will be described below based on FIGS. 1 and 3.

As shown in FIGS. 3(a) and 3(b), the light beam scanning device includes a light emitting means 1, a hologram lens 2, and a scanning surface 3. The hologram lens 2 is driven to rotate around a predetermined axis, and a diffraction grating having a lens effect is usually formed in a plurality of areas divided into fan shapes, although not shown, on the incident surface of the laser beam. has been done. Thereby, the laser beam emitted from the light emitting means 1 is made to linearly scan the scanning surface 3.

As shown in FIG. 1, the light emitting means 1 is composed of, for example, three semiconductor lasers 1a, 1b, and an IC, and these semiconductor lasers 1a, 1b, 1. c is drive switching means 4
It is connected to the drive control circuit 5 via. The drive switching means 4 switches the semiconductor lasers 1a and 1 at predetermined time intervals.
The drive control circuit 5 of the b-IC is provided to switch the drive by the drive control circuit 5, and several methods can be considered for the switching as shown below.

-a, the semiconductor laser is designed to oscillate and emit a laser beam in both directions, one of which is irradiated to the irradiation target, and the other laser beam is In order to monitor this, it is detected by a photodiode or the like. Therefore, the drive output of the drive control circuit 5 is switched by detecting the photodiode output signals from each of the semiconductor lasers 1a, 1b, and IC.

Further, the semiconductor laser is configured such that the drive switching means 4 switches the drive output within the time required for the temperature change ΔT by utilizing the fact that the oscillation wavelength is stable during a change in temperature ΔT within a certain range. It may be something that has been done.

It is also conceivable that each of the semiconductor lasers 1a, 1b, and IC is provided with a temperature sensor (not shown) to read the temperature, and when the temperature reaches the temperature immediately before a mode hop occurs, the drive output is switched. Furthermore, among the diffracted beams diffracted by the hologram lens 2 shown in FIG. The switching means 4 is not particularly limited in the drive switching method, and various configurations are possible.

On the other hand, as shown in FIG.
A deflection prism 6 serving as a guide means is provided in front of the laser beam 1c. The deflection prism 6 has a trapezoidal shape, and guides the emitted beams of the semiconductor lasers 1a, 1b, and 1c so that they are incident on the hologram lens 2 at a constant angle of incidence, and also guides the laser beams emitted from different directions. In conjunction with the switching operation of the drive switching means 4, the semiconductor lasers 1a and 1a change their directions accordingly.
The beams 1b and 1c are rotated around the intersection point P of the emission directions of the respective emission beams.

In the above configuration, when the drive is switched by the drive switching means 4 and the semiconductor laser 1c is driven,
The emitted beam of the semiconductor laser 1c is refracted by the deflection prism 6 rotated to the position shown in FIG. 2(a) and travels in the direction of arrow A. Further, when the drive is switched from the semiconductor laser 1c and the semiconductor laser 1b is driven, the emitted beam of the semiconductor laser lb passes through the deflection prism 6 rotated to the position shown in FIG. Go in six directions. Furthermore, when the drive is switched from the semiconductor laser 1b and the semiconductor laser la is being driven, the beam emitted from the semiconductor laser 1a is refracted by the deflection prism rotated to the position shown in FIG. Go in the direction.

By repeating the above operations, a laser beam that always travels in a fixed direction is obtained, and this laser beam is diffracted by the rotating hologram lens 2 and irradiated onto the scanning surface 3 so as to draw a scanning line.

In this way, by deflecting the emitted beams of the semiconductor lasers 1a, 1b, and IC by the deflection prism 6 and guiding them in a fixed direction, it is possible to make the beams incident on the hologram lens 2 at the optimum incident angle and position. Laser 1a
- The output beams 1b and 1c can also be diffracted at the same diffraction angle. Furthermore, since the drive switching means 4 is switched at a timing that does not cause mode hopping, optical scanning can be performed using a laser beam with a stable wavelength.

In addition, in the second to fourth embodiments described below, the same reference numerals are added to the constituent members having the same functions as in the present embodiment, and the explanation thereof will be omitted.

[Example 2] Next, a second embodiment of the present invention will be described.

In the second embodiment shown in FIG. 4, the semiconductor lasers 1a, 1b, and 1c of the light emitting means 1 are arranged at intervals of 90 degrees, and although not shown, the semiconductor lasers 1a, 1b, and 1c of the light emitting means 1 are arranged at intervals of 90 degrees. The drive control circuit 5 shown in FIG. Further, a half mirror 7 serving as a guide means is provided at a position where the output beams of the semiconductor lasers 1a, 1b, and 1c intersect. The half mirror 7 is operated in conjunction with the switching operation of the drive switching means 4 so that the mirror surface 7a is inclined with respect to the output beam of the semiconductor lasers 1a-1c, and the mirror surface 7a is orthogonal to the output beam of the semiconductor laser 1b. It is driven to rotate.

In the above configuration, the emitted beams of the semiconductor lasers 1a and 1c are transmitted through a half mirror whose mirror surface 7a is inclined with respect to the semiconductor lasers 1a and 1c.
7 and travels in the direction of the arrow 6, and the semiconductor laser 1
The emitted beam b passes through a half mirror 7 having a mirror surface 7a orthogonal thereto, and proceeds in the six directions of arrows. In this way, the emitted beams of the semiconductor lasers 1a, 1b, and IC enter the hologram lens 2 at a constant incident angle and position, as shown in FIG. 3, and optical scanning is performed on the scanning surface 3. .

[Example 3] Next, a third embodiment of the present invention will be described.

In the third embodiment shown in FIGS. 5(a) and (b),
The semiconductor lasers 1aib and 1c of the light emitting means 1 are arranged at 90° intervals, as in the second embodiment.
The difference is that a cylindrical mirror 8 is provided as a guide means. The cylindrical mirror 8 has a mirror surface 8a tilted with respect to the axial direction formed at the upper end thereof, and the semiconductor lasers 1a, 1b, I
It is arranged at a position where the output beams of C intersect. Also,
The cylindrical mirror 8 is rotated in forward and reverse directions in conjunction with the switching operation of the drive switching means 4.

In the above configuration, the cylindrical mirror 8 rotates in accordance with the drive switching of the semiconductor lasers 1a, 1b, and IC, and its mirror surface 8a is directed toward any one of the semiconductor lasers 1a, 1b, and IC that emits a laser beam. . The emitted beam is then reflected by the mirror surface 8a of the cylindrical mirror 8 and travels in the six directions of arrows, and as shown in FIG. 3, optical scanning is performed on the scanning surface 3 via the hologram lens 2.

[Example 4] Furthermore, a fourth embodiment of the present invention will be described.

In the fourth embodiment shown in FIG. 6, four semiconductor lasers 1a, 1b, 1c, and 1d whose driving is switched by a drive switching means 4 (not shown) are provided as the light emitting means 1, and 900 yen of each semiconductor laser is mounted on a disk 9. They are placed at intervals of 1°. The disk 9 includes semiconductor lasers 1a, 1b, and 1c.
-1d is rotated so that the driven one is located at point B.

In the above configuration, the semiconductor laser la, 1b, 1cm1d
Since one of them that emits the laser beam is located at point B, the laser beam continues in the direction of arrow A, and as shown in FIG. A scan is performed. In this manner, in this embodiment, since the laser beam already advances in the direction of arrow A from the time of emission, there is no need to deflect the laser beam.

As explained above in the first to fourth embodiments, the guide means only needs to be able to make the emitted beams of the semiconductor lasers 1a, lb-IC, and 1d enter the hologram lens 2 at the optimum position and angle of incidence. , but is not limited to the above configuration.

Similarly, the drive switching means 4 switches the semiconductor lasers 1a-1b, 1c, and 1d at time intervals in which mode hopping does not occur.
It is sufficient if the drive of the drive can be switched, and a method other than that exemplified in the first embodiment may be used.

〔Effect of the invention〕

As described above, the light beam scanning device according to the present invention includes a light emitting device and a hologram lens that guides light emitted from the light emitting device to a predetermined position on a scanning surface. a plurality of semiconductor lasers, and a guide means for guiding the laser beams so that each laser beam emitted from the semiconductor lasers is incident on the hologram lens at a constant angle of incidence and at a constant position; The configuration includes drive switching means that sequentially switches the drive at predetermined time intervals so as to operate one of the lasers.

As a result, the driving of one of the plurality of semiconductor lasers is sequentially switched at predetermined time intervals by the drive switching means to operate, so that the driving of the semiconductor laser can be switched before mode hopping occurs. is cooled, allowing continuous optical scanning with a laser beam of a stable wavelength.

In addition, since the laser beams emitted from multiple semiconductor lasers are all incident on the hologram lens at a constant angle of incidence and position by the guiding means, stable optical scanning can be performed without shifting the scanning line, and the cost is low. The present invention has the advantage that a highly accurate optical beam scanning device can be provided using a semiconductor laser.

[Brief explanation of drawings]

1 and 2 show a first embodiment of the present invention. FIG. 1 is a plan view showing the structure of the light emitting means and the guiding means. FIGS. 2(a) to 2(c) are plan views showing a state in which a laser beam is guided by a guiding means. FIG. 3 is common to the first to fourth embodiments. FIG. 3(a) is a front view showing the configuration of the light beam scanning device. FIG. 3(b) is a side view showing the configuration of the light beam scanning device. FIG. 4 is a plan view showing the structure of the light emitting means and the guiding means in the second embodiment of the present invention. FIG. 5 shows a third embodiment of the invention. FIG. 5(a) is a plan view showing the structure of the light emitting means and the guiding means. FIG. 5(b) is a front view of FIG. 5(a) showing the structure of the light emitting means and the guiding means. FIG. 6 is a plan view showing the structure of a light emitting means and a guiding means in a fourth embodiment of the present invention. FIG. 7 is a graph showing the relationship between the temperature of the semiconductor laser and the wavelength of the laser beam. 1 is a light emitting means, 1a, 1b, 1c, and 1d are semiconductor lasers, 2 is a hologram lens, 3 is a scanning surface, 4 is a drive switching means, 6 is a deflection prism (guiding means), and 7 is a half mirror.
(guiding means), 8 is a cylindrical mirror (guiding means), and 9 is a disk (guiding means).

Claims (1)

[Claims] 1. A light beam scanning device comprising a light emitting means and a hologram lens that guides light emitted from the light emitting means to a predetermined position on a scanning surface, wherein the light emitting means is provided with a plurality of semiconductor lasers. guiding means for guiding the laser beams so that each laser beam emitted from the semiconductor lasers is incident on the hologram lens at a constant angle and position;
A light beam scanning device comprising: drive switching means for sequentially switching drive at predetermined time intervals so as to operate any one of the plurality of semiconductor lasers.