JPS60100111A - Laser beam printer - Google Patents

Abstract

PURPOSE:To obtain a laser printer which is inexpensive and has a good picture quality by detecting a temperature of the vicinity of a plastic lens, and moving the lens along the optical axis. CONSTITUTION:A temperature is detected by a temperature detecting element 6 placed in the vicinity of a lens. When a temperature is higher than a reference value, a collimator lens 2a is moved to a rotary polyhedral mirror 3 side, and when a temperature is lower than the reference value, said lens is moved to a semiconductor laser 1 side by a lens moving device 2b, by which a beam diameter of a laser beam for forming an image on a photosensitive body 5 can always be kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention scans an optical boom using a plastic lens optical system and a light deflector to form an electrostatic latent image on a photoreceptor and visualize the latent image. A laser beam printer that obtains an image level by [5 iJ t le.

Conventional technology In general, plastic lenses are easier to produce aspherical surfaces than glass lenses, but since the curvature changes due to temperature, when plastic lenses are used in laser beam printers, the focal position of the boom is 1 it. There was a drawback that the 111 was misaligned and the quality of the 111 was deteriorated.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a laser beam printer with good image quality and low cost, which eliminates the above drawbacks.

According to the present invention, in a laser printer having a plastic lens optical system, a temperature detection means for determining the temperature of the plastic lens is arranged near the plastic lens, and a signal from the temperature detection means is arranged. A lens moving device is provided which compares the temperature with a preset reference temperature and moves the plastic lens in the direction of light 1il11+ by moving the output.

Example Examples of the present invention will be described in detail below according to one aspect.

FIG. 1 is a configuration diagram of a laser beam printer of the present invention. A laser beam 6 emitted from a semiconductor laser 1 is passed through a collimator lens 2a to form a parallel beam, and this parallel beam is deflected by a rotating mirror 3 II'e. An image is formed on the photoreceptor 5 through the lens 4.

On the other hand, 1) fJ As mentioned above, what about plastic lenses? m 1
．． 1), the refractive index changes as the temperature increases, and the refractive index decreases as the temperature decreases. Therefore, the focal length changes and the Since the diameter of the beam formed on the lens changes, the humidity is detected by the temperature detection signal B placed near the lens, and if the humidity is higher than the reference value, the frimeter lens 2
The laser beam formed on the photoreceptor 5 is moved by the lens moving device 12b along the light [lq'' towards the rotating polygon mirror 6 side, or towards the semiconductor laser 1 side if the temperature is lower than the reference value. beam diameter can always be kept constant.

The specific operation of the apparatus of the present invention will be explained with reference to the block diagram of FIG.

Lens temperature detection means, for example, a thermistor output number 4M, an output number indicating a non-image area, and a print number 4P3 are inputted to the CPU (processing device t> and a program for operating the OPU according to a predetermined procedure). A lens moving device fd (' 2 b is shown) is used to force the collimator lens 2-a to an appropriate position 1a in response to the stored ROM and the OPU.

The CPU executes the non-II! program according to the ROM program. When there is an output signal indicating the II image area and there is no human power to print the signal, input No. 4a from lens temperature detector 1-6, and combine this signal with the base 1 to j+ temperatures stored in the ROM. A signal is output to the lens moving device 2b according to the result, and the collimator lens 21L is moved back and forth so that the semiconductor laser beam Ji always remains constant on the photoreceptor. What is the travel distance of this collimator lens in advance for that temperature? It is determined by the tl' calculation, and this value is also stored in the FIOM.

Above, we have described a method in which the non-image area output signal and the 1:1 hand signal are given priority over the signal from the lens temperature detection means. When the area is exceeded, the position of the collimator lens may be changed by 1]1 in response to the non-image area output signal and the print signal output.

Incidentally, as a specific example of the lens moving device, the one shown in FIG. 6 can be considered. As shown in the figure, there are two guide rods 7, a screw shaft 8 with a spiral groove, a lens holder 9 that moves in parallel with the rotation of the screw shaft 8, and a motor that rotates the screw hammer 8. 10 and a support stand 11.

Further, in this embodiment, the same effect can be obtained by moving the Fθ lens 4 along the optical axis instead of moving the collimator lens along the optical axis.

Effects of the Invention As detailed above, the present invention provides an optical system for a laser beam printer using a plastic lens, in which a lens temperature detection means is arranged near the plastic lens, the temperature near the lens is detected, and the detected value is Since the lens is moved along the light beam i11+, an inexpensive laser printer with good quality can be produced.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention;
% Fig. 2 is a block diagram showing the operation of the device of the present invention, and Fig. 6 is a -! of the lens moving device. 191υ "Front side j blood diagram, code in the figure; 1... Semiconductor laser 2a... Frimeter lens 2
b...Lens moving device 6...Rotation pattern, j14...
IPe lens 5...Photoconductor 6...Lens temperature gJ: Detection means 7...Guide rod 8...Screw shaft

Claims (1)

[Claims] α) In a laser beam printer equipped with an optical system in which at least one or more plastic lenses are arranged,
A lens temperature detection means for measuring the temperature of the plastic lens is arranged near the plastic lens, and the signal from the temperature detection means described in 011 is compared with a preset reference temperature, and the output is used to move the plastic lens. A laser beam printer is equipped with a lens moving device that moves in the optical axis direction, and is characterized in that the lens is moved in accordance with temperature to always maintain a constant beam diameter on a photosensitive material. (2) Laser beam printers characterized in that the lens is moved into a non-image area.