JPS6179285A - Control method of temperature of semiconductor laser - Google Patents

Abstract

PURPOSE:To display predetermined functions in a semiconductor laser by controlling the temperature of the semiconductor laser so as to obtain a preset temperature when the temperature of a dew point is low and keeping the temperature of the semiconductor laser at a temperature as it is when the temperature thereof exceeds the preset one. CONSTITUTION:Laser beams projected from a semiconductor laser 1 are projected to a polygonal columnar rotary mirror 3 through a condenser 2, and laser beams reflected from the mirror 3 are condensed to a condenser 4 and projected to the surface of a photosensitive body 5. In the constitution, the intensity of laser beams reflected from the mirror 3 is detected by a photosensor 6, and the atmospheric temperature of the photosensitive body 5 is detected by a temperature sensor 7. A temperature sensor 8 detecting the density of the laser, a temperature sensor 8' detecting the atmospheric temperature of the laser and a humidity sensor 9 detecting the temperature of an atmosphere are mounted near the laser 1, output signals from these sensors are inputted to a micro-computer 10, and outputs from the micro-computer are added to the laser 1 connected to the computer 10 and a Peltier element 11 positioned near the laser 1, thus removing moisture condensation generated on a laser output window.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a temperature control method for a semiconductor laser (hereinafter abbreviated as LD), and relates to a temperature control method particularly suitably applied to an LD used as a light source of a laser printer.

<Prior Art> In recent years, laser printers that use laser light as a light source have been developed. The use of LDs to generate laser light is increasing from the viewpoint of miniaturization of light sources.

By the way, this LD has a characteristic that the output changes when the temperature changes even if the injection current is held constant, so in order to prevent the output change of the LD and maintain a predetermined output, Various techniques have been proposed to maintain the temperature of the LD at a constant value (Japanese Patent Application Laid-open No. 13343/1983,
JP-A-57-63879, JP-A-57-9979
(See Publication No. 1, Japanese Unexamined Patent Publication No. 57-136382, etc.).

That is, by installing several Peltier elements in the LD, the temperature is maintained at a constant temperature, for example, 20° C., regardless of the ambient temperature.

Therefore, regardless of external conditions, the LD can be maintained at a constant temperature and the output can be maintained constant. However, if the difference between the ambient temperature and the maintenance temperature becomes large, due to the influence of humidity conditions, etc. There is a possibility that the maintenance temperature becomes lower than the dew point temperature, causing dew condensation on the surface of the LD.

In this case, water droplets due to condensation will also adhere to the exit window of the LD, and the laser light will be scattered by the water droplets, resulting in the fatal inconvenience that it cannot function as a laser light source. Become.

<Purpose> This invention was made in view of the above problems,
It is an object of the present invention to provide a temperature control method that allows an ID to fulfill its function as a SIA light source, regardless of the ambient temperature, humidity, etc.

<Configuration> In order to achieve the above object, the temperature control method of the present invention is such that when the dew point temperature is low, the temperature of the semiconductor laser is
The temperature is maintained at a predetermined temperature at which the set output is obtained, and when the dew point temperature is above the predetermined temperature, the temperature of the semiconductor laser is set to a temperature higher than the dew point temperature. Therefore, it is necessary to control the temperature of the semiconductor laser so that the temperature of the semiconductor laser does not fall below the dew point temperature, thereby preventing dew condensation on the surface of the semiconductor laser, especially on the emission window, and fulfilling its function as a laser light source. can be done.

<Example> Embodiments will be described in detail below with reference to the accompanying drawings, in which examples are shown.

FIG. 1 is a schematic diagram showing the configuration of a laser printer, in which a laser beam from LD (1) is irradiated onto a mirror (3) through a condenser (2), and the laser beam reflected by the mirror (3) is The light is irradiated onto the photoconductor (9) through the condenser (4).Then, the optical sensor (6) detects the intensity of the laser beam reflected by the mirror (3), and the atmosphere of the photoconductor (5) is detected. A temperature sensor (8) that detects the temperature of the temperature sensor (sword, LD fi) that detects the temperature, a temperature sensor (8') that detects the temperature of the atmosphere of LD (11), LD (
Each output signal of the humidity sensor (9) that detects the humidity of the atmosphere in step 1) is applied to the microcomputer 00), and the image signal is applied to the microcomputer (10), and the output of the microcomputer flo) is applied to the microcomputer 00). A signal is applied to L D (1,1) and the Peltier element (11).

The mirror (3) is a polygonal columnar body whose outer surface is mirror-finished, and is rotated in the direction shown by the arrow in the figure by a drive mechanism (not shown), so that the photoreceptor (5) is rotated in the direction shown by the arrow in the figure.
) can be irradiated with laser light over the entire width of the area.

The microcomputer (10) stores the sensitivity-temperature curve of the photoreceptor (5) (see Figure 3), the output-temperature curve of the LD (1) (see Figure 4), and the dew point temperature curve for each humidity. The temperature sensor (7) changes the sensitivity of the photoreceptor (5) to the temperature sensor (8).
The temperature of D(1) can be calculated.

Figure 2 shows the mounting structure of L D (1), in which the heat sink (15) is attached to the mounting base (12),
2) through the hole (13) formed in the Peltier element (
11) to the heat sink (15), and attach the Peltier element (11) to the heat sink (15).
) with a holder (14) interposed therebetween.

With the above configuration, the dew point temperature can be calculated based on the output signals from the temperature sensor (8') and the humidity sensor (9), and the difference temperature between the temperature of the LD (1) and the dew point temperature can also be calculated. This means that it can be calculated.

Therefore, as shown by the solid line in FIG. 5, the Peltier element (
11) to control the temperature of L D [11], it is possible to reliably prevent dew condensation on the surface 1 of L D [11, particularly on the exit window portion.

In the above case, the sensitivity of the photoreceptor (5) can be calculated based on the output signal of the temperature sensor (sword), and the output of 1-D (1) can be calculated based on the output signal of the optical sensor (6). Therefore, the amount of change in sensitivity of the photoreceptor (5) due to temperature change can be calculated, and only the amount of change in the output of L D (1) that is greater than the amount that can compensate for the amount of change in sensitivity is calculated. The injection current of L D (1) can also be controlled to correct, in which case the injection current of L D (11 and photoreceptor (9)
It also has the effect that the overall characteristics can be maintained constant and good printing characteristics can always be exhibited.

<Effects> As described above, the present invention maintains the temperature of the semiconductor laser at a predetermined temperature at which the set output is obtained when the dew point temperature is low, and maintains the temperature of the semiconductor laser at a predetermined temperature at which the set output is obtained when the dew point temperature is below the predetermined temperature. Since the temperature is set higher than the dew point temperature,
Regardless of the ambient temperature, humidity, etc., it has the unique effect of preventing dew condensation from occurring on the surface of the semiconductor laser, especially at the emission window, and allowing it to function as a laser light source.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the configuration of the laser printer, Figure 2 is a diagram showing how the semiconductor laser is mounted, Figure 3 is a diagram showing the sensitivity-temperature curve of the photoreceptor (5), and Figure 4 is a diagram showing the sensitivity-temperature curve of the photoreceptor (5). A diagram showing the output-temperature curve of the semiconductor laser (1) when the injection current is kept constant. Figure 5 is the semiconductor laser (1).
FIG. 3 is a diagram showing the relationship between temperature and dew point temperature. (1)... Semiconductor laser, (5)... Photoreceptor.

Claims (1)

[Claims] 1. When the dew point temperature is low, the semiconductor laser temperature to a predetermined temperature at which the set output is obtained. temperature and the dew point temperature is below the specified temperature. In the above case, expose the temperature of the semiconductor laser. It is especially important to set the temperature higher than the point temperature. A temperature control method for semiconductor lasers.