JPH08335740A - Laser having a plurality of light sources - Google Patents

Abstract

PURPOSE: To supply a stabilized laser light constantly by canceling thermal interference by self temperature rise among a plurality of light sources. CONSTITUTION: A semiconductor laser chip is fixed with writing light sources 14, 15 and temperature compensation light sources 16, 17 on the outside. The writing light sources 14, 15 emit laser lights L3, L4 forward and laser lights L5, L6 rearward, respectively. When an image is written on a photosensitive body using the writing light sources 14, 15, the temperature compensation light sources 16, 17 emit light at a timing exactly opposite to that of the writing light sources 14, 15. Consequently, any one of two light sources contiguous to the writing light sources 14, 15 emits light constantly thus supplying a stabilized laser light constantly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser generator having a plurality of light sources for a writing / scanning optical device used in a laser printer, a digital copying machine or the like.

[0002]

2. Description of the Related Art In a conventional laser generator used for writing laser light, a method of increasing the rotation speed of a rotary polygon mirror which is a deflecting means is known as a means for increasing the recording speed.

However, in this method, an expensive one such as an air bearing must be used as the deflecting means so as to adapt to high-speed rotation, and no matter how expensive the bearing is, the rotating speed of the rotary polygon mirror will be high. There is a limit. Also, when the rotating polygon mirror rotates at high speed, problems such as vibration, temperature rise, and dust entrapment become more serious. Therefore, make multiple laser beams incident on the rotating polygon mirror and simultaneously scan multiple scanning lines. Has proposed a scanning optical system that substantially increases the scanning speed without increasing the rotation speed of the rotary polygon mirror.

FIG. 6 is a block diagram of a conventional example. In the emitting direction of a semiconductor laser chip 3 in which light emitting point sources 1 and 2 are provided with an interval I, an optical system such as a lens system and a polarizing means is not shown. The photoconductors are sequentially arranged, and the laser beams L1 and L2 from the light emitting point sources 1 and 2 are recorded on the photoconductors via these lens systems and polarization means. The semiconductor laser chip 3 is sealed by a cap 4 and a stem 5, a lead wire 6 is connected to the stem 5, and light emission is controlled by a laser driving circuit (not shown). Instead of providing two light emitting point sources 1 and 2,
Further, a plurality of light emitting point sources may be provided.

As described above, when an array-shaped light source in which a plurality of light sources are arranged side by side in a row is used, a plurality of scanning lines can be recorded and displayed at the same time, so that the scanning speed becomes high.
Further, since the rotating speed of the deflecting means such as the rotary polygon mirror can be slowed down, the deflecting means can be inexpensive, and vibration, temperature rise,
Problems such as dust entrapment can be solved.

[0006]

However, in the above-mentioned conventional example, since the distances between the individual light sources are short, there is a problem that the self-heating caused by the light emission causes thermal interference with each other and the light emission efficiency changes. .

FIG. 7 is a timing chart showing changes in the temperature and the amount of emitted light of the light emitting point sources 1 and 2. The light emitting point sources 1 and 2 are subjected to thermal interference due to self-heating. When the drive signals A1 and A2 of the light emitting point sources 1 and 2 are turned on and light is emitted at the same time, for example, the drive signal A1 is turned on and the drive signal A2 is turned on.
The temperatures B1 and B2 of the light emitting point sources 1 and 2 are higher than in the case where only one of them is made to emit light by turning off. Temperature B1,
Since the luminous efficiency of laser light decreases as B2 increases,
When the light emitting point sources 1 and 2 are made to emit light at the same time, the emitted light amounts C1 and C2 are smaller than when only one of them is made to emit light, resulting in a difference in the emitted light amount.

Therefore, in the laser beam writing apparatus, there is a problem that the light energy irradiated on the photoconductor is varied, which leads to the variation of the potential on the photoconductor and the uneven density of the output image. .

The object of the present invention is to solve the above problems,
It is an object of the present invention to provide a laser generator having a plurality of light sources which cancel each other's thermal interference due to self-heating caused by light emission even though the laser generator has a plurality of light sources close to each other.

[0010]

A laser generator having a plurality of light sources according to the present invention for achieving the above object is a laser generator for writing a laser beam to a recording means via a lens means and a deflecting means. A plurality of laser generators and the same number of temperature compensating means as these laser generators are provided.

[0011]

In the laser generator having a plurality of light sources having the above-mentioned structure, the temperature compensating means emits light at the light emission timing opposite to that of the laser generator on the side which is not adjacent to each other. Cancel thermal interference,
A stable writing laser beam for writing is always supplied.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a configuration diagram of an embodiment, and FIG. 2 is a perspective view of a semiconductor laser chip. In FIG. 1, a semiconductor laser chip 13 as shown in FIG. 2 is attached on a frame 12 fixed to the stem 11. The semiconductor laser chip 13 is provided with writing light sources 14 and 15, a temperature compensating light source 16 is provided outside the writing light source 15, and a temperature compensating light source 17 is provided outside the writing light source 14. These writing light sources 14,
Reference numeral 15 is adapted to emit laser beams L3 and L4 to the front, and laser beams L5 and L6 to the rear. In addition, the writing light sources 14 and 15, the temperature compensation light source 16,
Numerals 17 are attached on a straight line at substantially equal intervals and all have substantially the same characteristics.

A photodiode 18 used to monitor the laser beams L5 and L6 emitted from the semiconductor laser chip 13 to the stem 11 side and adjust the light amount is fixed to the mount 12. Further, the stem 11 includes a mount 12, a semiconductor laser chip 13, and a photodiode 1.
A cap 19 for enclosing 8 is fixed, and the inside of the cap 19 is filled with an inert gas such as helium. The cap 19 is provided with a transparent emission window 20 formed of glass or the like for taking out the laser beams L3 and L4 from the semiconductor laser chip 13, and the laser beams L3 and L4 are provided with a lens system, a deflector, not shown. The latent image is formed by being irradiated onto the photoconductor through a mirror or the like.

A lead wire 21 is connected to a driver circuit (not shown) provided on the side of the stem 11 opposite to the cap 19 for driving the device, and the semiconductor laser chip 13, the photodiode 18 and the bonding wire are connected. It is connected by W.

Since the laser light generated from the temperature compensating light sources 16 and 17 must not be emitted from the emission window 20 or irradiated to the photodiode 18, the temperature compensating light sources 16 and 17 as shown in FIG. Light-shielding portions 22 are provided on the gantry 12 in front of and behind. Further, instead of providing the light shielding portion 22, the front and rear surfaces of the temperature compensating light sources 16 and 17 may be end face coded so that the laser light is not emitted.

FIG. 4 is a timing chart showing changes in the temperature and the amount of emitted light of the writing light sources 14 and 15 and the temperature compensating light sources 16 and 17.
The light sources 16 and 17 for temperature compensation are made to emit light at the light emission timings opposite to the light emission timings of 5 and 5, respectively. That is,
Drive signal A for writing light source 14 and temperature compensating light source 16
3 and A4 are turned on and off at timings opposite to each other, and drive signals A5 of the writing light source 15 and the temperature compensation light source 17,
A6 turns on and off at the exact opposite timing.

As a result, only one of the two adjacent light sources of the writing light sources 14 and 15 is always emitting light, and the writing light sources 14 and 15 are the other writing light sources 15 and 14. Regardless of whether or not the
A temperature compensating light source 16 which always has a constant heat energy,
Supplied from 17. At this time, the writing light source 14,
The temperatures B3 and B4 at the time of emitting light of 15 are the light sources 14 and 1 for writing.
5, the light emission amounts C3 and C4 of the writing light sources 14 and 15 are not affected by the on / off states of the other writing light sources 14 and 15, and are always stable. It is possible to supply the laser light of the specified light amount.

When the writing light sources 14 and 15 have different lasing wavelengths, and the temperature characteristics are different, the temperature compensating light source 16 is the writing light source 14 and the temperature compensating light source 17 is the writing light source. The same effect can be obtained by using a light source having the same characteristics as 15.

In this way, the writing light sources 14, 1
Temperature compensating light source 1 having characteristics equivalent to that in the vicinity of 5
6 and 17 are provided, and the light sources 14 and 15 are caused to emit light at timings opposite to each other, whereby mutual thermal interference between the light sources 14 and 15 for writing can be canceled and a stable laser beam can be always supplied.

In the embodiment, since the semiconductor laser light source having the same characteristics as those of the writing light sources 14 and 15 is used for temperature compensation of the writing light sources 14 and 15, lasers are provided before and after the temperature compensation light sources 16 and 17. Although the end face coat or the light shielding portion 22 is provided so that light does not leak, the writing light sources 14 and 15 are used as the temperature compensating light sources 16 and 17.
It is possible to prevent the laser light of the temperature compensating light sources 16 and 17 from being emitted to the outside of the device by using a semiconductor laser light source whose luminous efficiency is significantly lower than the above.

FIG. 5 shows the temperature compensating light sources 16 and 17.
Writing light sources 14, 15 and temperature compensating light sources 16, 1 when using a semiconductor laser light source of which generation efficiency is extremely low
7A and 7B are emission light amount characteristics and a self-heating characteristic diagram of FIG. 7, in which the horizontal axis represents the current I and the vertical axis represents the emission light amount L and the temperature T. A semiconductor laser light source with good generation efficiency has a light emission amount curve La and a self-temperature rise curve Ta, and emits laser light by passing a current of a relatively low current I1 or more, and emits laser light of high power with a small current. To do. Further, since the current loss is small, the self-heating curve Ta due to light emission is also low. On the other hand, a semiconductor laser light source with poor light emission efficiency has a light emission curve
Lb and the self-heating curve Tb are provided, and the laser light is emitted by the current I2 or higher and the current I2 or higher, and the self-heating curve Tb also rises.

Therefore, a semiconductor laser light source having the characteristics of the emission light amount curve La and the self-heating temperature curve Ta is used as the writing light sources 14 and 15, and the emission light amount curve Lb and the self-heating temperature curve Tb are used as the temperature compensating light sources 16 and 17. A semiconductor laser light source having the characteristics of is used. When the writing light sources 14 and 15 emit the laser light of the emitted light amount Lx shown in FIG. 5, a current I3 is passed through the writing light sources 14 and 15, and the writing light sources 14 and 15 are self-heated to cause a change in FIG. This produces the indicated temperature Tx. The temperature compensating light sources 16 and 17 are the writing light source 1.
Since it is necessary to have a self-temperature rise equivalent to that of Nos. 4 and 15, the current I4 may be passed so as to obtain the temperature Tx.

At this time, since the temperature compensating light sources 16 and 17 emit light only to the extent that recording on the photosensitive member is not affected,
It is not necessary to coat the front and rear of the temperature compensating light sources 16 and 17 with end faces or to provide the light shielding portion 22 as in the previous embodiment. Instead of using the semiconductor laser light source as the temperature compensating light sources 16 and 17, a heat source such as a heater having the same temperature characteristics as the writing light sources 14 and 15 can be used.

In this way, it is possible to obtain a laser generator that constantly supplies a stable amount of laser light without being affected by mutual self-temperature rise, as in the first embodiment.

[0025]

As described above, the laser generator having a plurality of light sources according to the present invention has a plurality of laser generators close to each other, and the same number of temperature compensators as the laser generators are provided. By emitting light at timings opposite to those of the laser generating portions on the side not adjacent to each other, it is possible to cancel the variation in the emitted light amount caused by mutual thermal interference due to self-heating of the laser generating portions.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment.

FIG. 2 is a perspective view of a semiconductor laser chip.

FIG. 3 is an explanatory diagram of a light shielding unit.

FIG. 4 is a timing chart of the temperatures and the emitted light amounts of the writing light source and the temperature compensating light source.

FIG. 5 is a diagram showing a light emission amount characteristic and a self-heating characteristic of a semiconductor laser light source.

FIG. 6 is a configuration diagram of a conventional example.

FIG. 7 is a timing chart of the temperature of a light emitting point source and the amount of emitted light.

[Explanation of symbols]

 11 Stem 12 Stand 13 Semiconductor Laser Chip 14 and 15 Writing Light Source 16 and 17 Temperature Compensating Light Source 18 Photodiode 19 Cap 20 Exit Window 21 Lead Wire 22 Light-shielding Part

Claims (4)

[Claims] 1. A laser generator for writing a laser beam to a recording means via a lens means and a deflection means, comprising a plurality of laser generators and the same number of temperature compensators as these laser generators. A laser generator with multiple light sources. 2. The laser generator and the temperature compensator are semiconductor laser light sources, and the two laser compensators in the center and the two temperature compensators on both outer sides are arranged in a straight line at substantially equal intervals. The laser generator having a plurality of light sources according to claim 1, wherein the temperature compensating means is driven at a timing opposite to that of the laser generator on the side not adjacent to each other. 3. A laser generator having a plurality of light sources according to claim 1, further comprising a light-shielding means for preventing the laser light generated by the temperature compensating means from being emitted to the outside. 4. A laser generator having a plurality of light sources according to claim 1, wherein the temperature compensating means is a semiconductor laser light source whose luminous efficiency is significantly lower than that of the laser generator.