JPS58127955A - Electrophotographic printer - Google Patents

Abstract

PURPOSE:To obtain images of high quality by providing a temp. detecting part which measures the temp. of a photoreceptor, an acouto-optic modulator which modulates laser light, and a control part which receives the detection signal from the temp. detecting part and feeds a control signal to the optical modulator. CONSTITUTION:When the surface temp. of a photoreceptor 1 rises, for example, the electric resistance of a temp. sensor 2 increases, and the change in the voltage corresponding to said increase is applied to an amplification factor calculator 11, where the voltage is amplified and is transmitted to a multiplier 12. In the multiplier 12, the on-off signal from a video signal generator 13 and the amplification signal from the calculator 11 are multiplied, and the product thereof is transmitted to an FM modulator 14. The level of the modulation signal from the modulator 14 is decreased, and as a result, the quantity of the laser light is decreased with an acousto-optic modulator 5. In such a way, the increase in the sensitivity owing to an increase in the temp. of the photoreceptor 1 is compensated by the decrease in the exposure of the laser light with the modultor 5, thus the electrostatic latent images formed on the surface of the photoreceptor 1 are maintained constant irrespectively of the rise in the temp. of the photoreceptor 1, and the images of high quality are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a light beam modulated according to recorded information, which is generally referred to as a laser printer! The present invention relates to an electrophotographic printing device that can obtain an image by scanning the surface of a colored light body.

In general, the initial surface potential of a photoconductor is high at low temperatures, and the sensitivity (potential difference between bright and dark areas) tends to be high in pyrometers, and such changes in characteristics due to temperature affect the sensitivity of the photoconductor. The higher the value, the more noticeable it is.

For this reason, the background and image contrast of images are not constant due to temperature changes, making it difficult to obtain images with uniform image quality.

The present invention relates to an improvement of an electrophotographic printing device that overcomes these difficulties, and includes a temperature detection unit that measures the temperature of a photoconductor and a light beam that scans the surface of the photoconductor. It is characterized by comprising an exposure amount adjustment means disposed between the scanning means and the light source, and a control section that receives a detection signal from the temperature detection section and sends a control signal to the exposure amount adjustment means. The purpose of this invention is to provide an electrophotographic printing device that can form uniform images even under various humidity conditions.

As described above, the present invention provides an electrophotographic printing apparatus in which a temperature detection section for measuring the temperature of a photoreceptor is provided, and an exposure amount adjustment means is arranged near a light source that scans a light beam on the surface of the photoreceptor. and a control section that receives a detection signal from the temperature detection section and sends a control signal to the exposure sensitivity adjustment means, so that temperature changes occur in the photoconductor and the surface potential of the photoconductor fluctuates. However, in response to a detection signal from the temperature detection section, a control signal is sent from the control section to the exposure amount adjustment means, and the photoreceptor is exposed to light with an exposure amount that matches this temperature change, and the temperature is adjusted. Images of uniform quality are obtained regardless of variations.

An embodiment of the present invention illustrated in the drawings will be described below.

1 is a drum-shaped photoreceptor with high sensitivity;
A temperature sensor 2 that can detect temperature changes as changes in electrical resistance is disposed adjacent to the circumferential surface of the sensor.

The laser optical system 3 includes a gas laser tube 4 that generates laser light, an acousto-optic modulator 5 that modulates the laser light, a lens 6, a mirror 7, and a rotating mirror 8.
In the laser optical system 3, the laser beam emitted by the laser tube 4 is modulated and separated into zero-order light and first-order light by the acousto-optic modulator 5 in accordance with the video signal. Only the primary light is taken out by a slit, diffused and focused by a lens 6, reflected by a mirror 7, focused into a spot by a rotating mirror 8, and projected and scanned onto the peripheral surface of a drum-shaped photoreceptor. It has become.

The temperature sensor 2 is incorporated into a bridge circuit which is the temperature-voltage converter IO of the control unit 9, and a change in electrical resistance of the temperature sensor 2 corresponding to a temperature change is detected as a voltage change. ing.

Further, the output terminal of the temperature-voltage converter IO is connected to the amplification factor calculator 11, the output terminal of the amplification factor calculator 11 is connected to one input terminal of the multiplier 12, and the amplification factor calculator 11 is connected to one input terminal of the multiplier 12. calculator 1
The other input terminal of 2 is connected to a video signal generator 13, and the multiplier 12 multiplies the video signal from the video signal generator 13 and the temperature detection signal, and the product is subjected to 7M modulation. The data is transmitted to the device 14.

Furthermore, the FM modulator 14 receives a high frequency signal from a high frequency oscillator 15, and the multiplier transmits a modulated signal with an amplification factor corresponding to the output from the multiplier 12 to the acousto-optic modulator 5. .

Since the illustrated embodiment is configured as described above, when the surface temperature of the drum-shaped photoreceptor 1 changes and becomes, for example, high temperature, the electrical resistance of the temperature sensor 2 increases, and the voltage changes corresponding to the increase in resistance. is applied to the amplification factor calculator 11,
The voltage is amplified by an amplification rate set according to the characteristics of the photoreceptor 1, and the multiplication is sent to the calculator 12. In the multiplier 12, the on/off signal transmitted from the video signal generator 13 is multiplied by the amplification signal from the amplification factor calculator 11, and the product is transmitted to the 7M modulator 14, and the FM
The level of the modulation signal emitted from the modulator 614 is reduced compared to the case of low temperature, and as a result, the amount of laser light converted into dot laser light by the acousto-optic modulator 5 is reduced.

In this way, the increase in sensitivity due to the temperature rise of the photoreceptor 1 is compensated for by the reduction in laser exposure to the photoreceptor 1 by the acousto-optic modulator 5, and therefore, the increase in sensitivity due to the temperature increase of the photoreceptor 1 is compensated for by the reduction in laser exposure to the photoreceptor 1. The electrostatic latent image formed on the surface of the photoreceptor 1 is maintained constant, resulting in a high quality image with constant image contrast and background.

In the above embodiment, an acousto-optic modulator is used as the exposure adjustment means, but an electro-optic modulator, a magneto-optic modulator, or a filter may be used instead.

Although the present invention has been described above in detail with respect to the embodiments shown in the drawings and the embodiments not shown in the drawings, the present invention is not limited to such embodiments and can be modified without departing from the spirit of the invention. The design can be freely modified as necessary.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram illustrating an embodiment of an electrophotographic printing apparatus according to the present invention, and FIG. 2 is a block diagram of its essential parts. 1...Tram-shaped photoreceptor, 2...Temperature sensor, 3...
... Laser optical system, 4... Laser tube, 5... Acousto-optic light modulator, 6... Lens, 7... Mirror, 8...
- Rotating mirror, 9... Control unit, IO... Temperature-voltage converter, 11... Amplification factor calculator, 12... Multiplication calculator, 13... Video signal generator, 14...'F
M modulator. Agent: Patent attorney Nozomi Ehara (1 person)

Claims (1)

[Claims] ? Ii? In a photographic printing device, a temperature detection unit that measures the temperature of a photoconductor, an exposure amount adjustment unit that is disposed between a light source and a scanning unit that scans a light beam on the surface of the photoconductor, and a temperature detection unit that measures the temperature of the photoconductor. 1. An electrophotographic printing apparatus comprising: a control section that receives a detection signal from the section and sends a control signal to the exposure amount adjustment section.