JPS61289366A - image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a so-called laser beam printer, a device that records information by scanning a photoreceptor with a laser beam modulated in accordance with a recorded signal, and particularly relates to a This invention relates to a laser beam printer using a laser.

(Prior Art) Conventionally, in the above-mentioned laser beam printer, the following methods have been used to compensate for the deterioration in image quality due to fluctuations in the oscillation wavelength caused by changes in the operating temperature of the semiconductor laser. In other words, an electronic cooling device that uses the Beltier effect (hereinafter referred to as a Peltier device) keeps the semiconductor laser at a constant temperature, stabilizes the single oscillation wavelength, and stabilizes the image quality, and a heater that stabilizes the semiconductor laser. A method has been proposed in which the temperature is controlled to a constant temperature near the upper limit of the operating environment temperature.

(Problem to be solved by the invention) However, in the case of the above-mentioned conventional technology, a Peltier element and a heater are used to adjust the temperature of the semiconductor laser, so special circuits and power supplies are required to drive them. There is a problem in that the cost is high. Further, there is a problem in that it requires time for the semiconductor laser to reach a predetermined temperature, that is, a wait time, and when a heater is used, printing has to wait for about two minutes.

Therefore, in order to solve the above problems,
As described in Japanese Patent No. 104486, a method has been proposed in which the temperature of the semiconductor laser is detected and the output of the semiconductor laser is continuously changed in accordance with changes in the operating temperature to improve image quality.

However, in the case of such conventional technology, since the output of the semiconductor laser is continuously changed depending on the change in operating temperature, the density changes on a single sheet of transfer paper, causing uneven shading and degrading the image quality. There was a problem with that.

The present invention has been made to solve the problems of the prior art, and aims to be inexpensive, do not require special temperature control means, do not require waiting time, and can be made in one sheet. To provide a laser beam printer capable of obtaining high-quality images without unevenness in shading on a transfer material.

(Means for Solving the Problems) In order to achieve the above object, the present invention scans a photoreceptor with a laser beam emitted from a semiconductor laser driven in accordance with a recorded information signal. In a laser beam printer that records information on a transfer material, output detection means for detecting the beam output of the semiconductor laser;
temperature detection means for detecting the temperature of the semiconductor laser;
and a control means for controlling the beam output of the semiconductor laser according to the temperature of the semiconductor laser, and is configured to control the beam output of the semiconductor laser before starting a recording operation on one sheet of transfer material. ing.

(Embodiments) The present invention will be explained below based on illustrated embodiments. Figures 1 to 3 show a laser beam printer according to the present invention.
In the figure, 1 is a semiconductor laser unit which is driven in blinking modulation by a recorded information signal from a computer, word processor, facsimile transmitter, etc. A laser beam 2 oscillated by a semiconductor laser unit 1 is deflected and scanned by a polygon mirror 4 that is rotationally driven by a motor 3, and is imaged in a spot shape by a lens 5 on an electrophotographic photosensitive drum 6 rotating in the direction of the arrow. The drum 6 is scanned. Note that 7 is a mirror that reflects the beam 2 downward and directs it toward the drum.

The photoconductor used is a photoconductor sensitive to the emission wavelength range of a semiconductor laser, such as a metal phthalocyanine organic photoconductor, an amorphous silicon photoconductor, a selenium photoconductor, or cadmium sulfide.

A charger 8 uniformly charges the photosensitive drum 6 covered with the organic photoconductor or the like.

The photosensitive drum 6 charged by the charger 8 is scanned by the laser beam 2 described above, and an electrostatic latent image is formed. In this embodiment, a portion to which toner is to be attached (that is, a portion to be visualized) is irradiated with a laser beam.

That is, a so-called image scanning method is used in which a portion irradiated with a laser beam is developed. because.

This is because the image scan method has clearer image quality than the background scan method, requires less laser light emission time, and is advantageous for the lifespan of the semiconductor laser.

This electrostatic latent image is visualized by the primary developing device 9.

- The sheet P on the force loading table S is fed onto the photoreceptor drum 6 by the feed roller 10 and the registration roller 11 which rotates in synchronization with the image on the photoreceptor drum 6. Then, the toner image on the photosensitive drum 6 is transferred onto the sheet P by the transfer charger 12.

Thereafter, the sheet P separated from the photoreceptor drum 6 by the separating means 13a is transferred to the fixing device 14 by the guide 13.
After the toner image on the sheet P is fixed, the toner image is discharged onto a tray 16 by a discharge roller 15.

On the other hand, the surface of the photoreceptor drum after transfer is cleaned by a cleaning device 1.
Cleaned by 7.

As shown in FIG. 2, the semiconductor laser unit 1 includes a semiconductor laser 18, and the semiconductor laser 18 is sealed by a laser package 19. This laser package 19 is screwed to a base 20 made of a material with good thermal conductivity such as aluminum. Further, a thermistor 21 as a temperature detection means for detecting the temperature of the semiconductor laser 18 is attached to the surface of the laser package 19, and an output detection means for detecting the output of the laser beam light is provided inside the laser package 19. A pin photodiode 22 is arranged to be able to receive laser beam light emitted from the rear of the semiconductor laser 18. Further, a collimator lens 23 for collimating the light beam emitted from the semiconductor laser 18 is fixed to a holder 25 with a nut 24, and the holder 25 is fixed to the base 20 with screws.

FIG. 3 shows the control circuit of this embodiment. The thermistor 21 and pin photodiode 22 attached to the semiconductor laser 22) are connected to the A-D converter 26.2.
7 to a CPU 28 as a control means, and a signal from a print switch 29 is also input to the CPU 28. This CPO 28 is connected to a laser drive circuit 30 that drives the semiconductor laser 18 . C
As shown in the flowchart of FIG. 4, the PU 18 controls the laser drive circuit 3o based on signals from the thermistor 21, pin photodiode 22, and print switch 29, and controls the drive current I flowing through the semiconductor laser 18.
change.

Next, the temperature characteristics of semiconductor lasers and the characteristics of photoreceptors used in laser beam printers will be described.

Figure 5 shows the temperature characteristics of a semiconductor laser. The wavelength λ of the laser beam it oscillates in a semiconductor laser varies stepwise along a certain straight line depending on the operating temperature T, and the rate of change Δλ/ΔT is approximately 0.2. ~0.3 n+w/deg. Therefore, the oscillation wavelength λ of a semiconductor laser at a temperature T is, if the oscillation wavelength at a certain temperature To is ON, then λ=ON 0 +Δλ/ΔT・(T−To) .
(I) makes you eat sweet potatoes.

Furthermore, the sensitivity characteristics of the photoreceptor are expressed when the horizontal axis is the laser wavelength λ and the vertical axis is the surface potential V of the photoreceptor.

Laser light output P+, P2, P3 (P
+ < P2 < P3 ), the sensitivity changes as shown in FIG. 6, and when the wavelength of the laser beam exceeds 790+ dust, the sensitivity rapidly decreases. Furthermore, in order to obtain the same potential on the surface of the photoreceptor, the longer the wavelength of the laser light, the greater the laser light output P is required.

In the above configuration, in the laser beam printer according to the present invention, output control of the semiconductor laser is performed as follows. The relationship shown in FIG. 6 is input into the CPU 28 in advance. In other words, assuming that the potential of the photoreceptor is approximately VO in order to obtain good image quality in a laser beam printer, as shown in FIG. It can be seen that a low laser light output is sufficient to achieve this, and as the temperature rises and the laser wavelength becomes longer, the laser light power required to bring the potential of the photoreceptor to vo increases rapidly. Therefore, the CPU 28 includes a semiconductor laser 18.
Even if the operating temperature of the semiconductor laser 1B changes and the laser wavelength changes, a laser output value that can maintain the potential of the photoreceptor at the value necessary to obtain good image quality is input for each operating temperature of the semiconductor laser 1B. ing.

First, as shown in FIG. 2, the temperature of the semiconductor laser 18 is detected by the thermistor 21 attached to the laser package 19.

CP02B calculates a laser output value corresponding to the temperature. The CPU 28 controls the laser drive circuit 3 while monitoring the actual laser output with the pin photodiode 22 in the laser package 19 so that the output of the semiconductor laser 18 becomes equal to the laser output value.
0 to control the drive current I of the semiconductor laser 18.

Incidentally, the above-described temperature measurement and laser light output control of the semiconductor laser 18 are performed before starting the recording operation for one sheet of transfer material. That is, after the print switch 29 is pressed until printing is performed on the transfer material, the CPU 28 controls the laser light output in accordance with the temperature measurement. As shown, the output control of the laser beam is performed in a non-image area 34 on the photoreceptor 31 before a latent image is formed on the image area 33 corresponding to one sheet of transfer paper 32 with the laser beam.

As described above, the image area 33 corresponding to one sheet of transfer paper 32
Since the output of the laser light is not controlled in
The image quality does not deteriorate due to changes in laser light output and print density changes on the same transfer paper.

Note that, in reality, the wavelength-temperature change rate Δλ/ΔT of the semiconductor laser 18 differs for each semiconductor laser 18 and therefore needs to be corrected. This correction is performed by measuring the wavelength of each semiconductor laser at two points, the upper and lower limits of the operating environment temperature, and
In addition to the method of determining ΔT and inputting this value to the CPO 28, a variable resistor connected in series to the pin photodiode 22 is used so that the laser light output characteristic is equal to the preset value of Δin/ΔT. This is achieved by a method of correcting the value of .

Further, correction of the sensitivity characteristics of the photoreceptor is similarly achieved by correcting the value of the variable resistance of the pin photodiode.

Furthermore, the semiconductor laser 18 has a maximum allowable output,
If the semiconductor laser 18 is driven beyond this range, there is a risk of damage. Therefore, when the output of the semiconductor laser 18 detected by the pin photodiode 22 reaches the above-mentioned maximum allowable output value, it is either continued to be used at an output value that does not exceed this value, or it is considered that the semiconductor laser 18 has deteriorated. Actions such as warning the operator are required.

(Effect of the invention) The present invention consists of the above structure and operation.

Since it does not require any special temperature control means, it is inexpensive and requires no waiting time. It also eliminates density unevenness caused by laser light output control on a single sheet of transfer material, and provides good image quality. Laser beam printers can be provided.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view showing an embodiment of a laser beam printer according to the present invention, FIG. 2 is a longitudinal sectional front view showing a laser unit, FIG. 3 is a block diagram showing a control circuit of the laser unit, and FIG. Figure 5 is a flowchart showing the program executed by the control circuit, Figure 5 is a graph showing the relationship between semiconductor laser temperature and emission wavelength, Figure 6 is a graph showing the relationship between laser wavelength and photoreceptor potential, and Figure 6 is a graph showing the relationship between laser wavelength and photoreceptor potential. FIG. 7 is an explanatory diagram showing the timing of laser output control on the photoreceptor. Explanation of symbols 18...Semiconductor laser 21...Thermistor 22
...Pin photodiode 28...CPU 32...Transfer paper 20 Fig. 3 Fig. 4 Fig. 5 Komoten r"c Fig. 6, -chi temporary length nm Fig. 7 Procedural amendment form ( jj power October 23, 1985

Claims (1)

[Claims] In a laser beam printer that records information on a transfer material by scanning a photoreceptor with a laser beam emitted from a semiconductor laser driven in response to a recorded information signal, an output for detecting the beam output of the semiconductor laser. comprising a detection means, a temperature detection means for detecting the temperature of the semiconductor laser, and a control means for controlling the beam output of the semiconductor laser according to the temperature of the semiconductor laser,
A laser beam printer characterized in that the beam output of the semiconductor laser is controlled before starting a recording operation on one sheet of transfer material.