JPS5827460A - Laser beam printer - Google Patents

Abstract

PURPOSE:To simpify the constitution, by switching one optical beam projected to a recording horizontal scanning direction at each picture element at a modulation scanner, in a laser beam printer recording through the use of a laser light. CONSTITUTION:A laser light from a laser generator 9 reaches a scanner 23 through a lens 20, a cylinder lens 21 and a mirror 22 via a mirror, and is modulated at a modulation scanner circuit 24, scans the surface of a photoreceptor drum 1 horizontally and gives a train of photo spots on the drum corresponding to each picture element. At the inside of transparent bodies 27 and 28 of a scanner 23, a block electrode 32 and a control electrode 33 are opposed near with a spacer 26 and an element changing the optical properties in response to a voltage such as liquid crystal is provided between them, and the laser beam light is projected as an input light 30 to an electrode 32 and a thin long beam modulated from the control electrode 33 is outputted as an output light 31. Each control electrode 33 acts like an optical shutter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser beam printer that records using laser light. When laser light is used to record information, recording media include silver salt photoreceptors, electrophotographic photoreceptors, photosensitive resins, etc., but electrophotographic recording is widely used as a method of high-speed, large-volume recording and easy handling. It is being used.

FIG. 1 shows a schematic configuration of a conventional laser beam printer that combines laser scanning technology and electrophotography technology.

A photoconductive drum 1 is uniformly charged with a charger 2, and then a laser beam 3 modulated with information is irradiated to form a charge latent image. Subsequently, the charged latent image is developed by a developing device 4, and a colored toner image is adhered to the drum surface. Next, this toner image is transferred onto recording paper 5 by the action of transfer device 6. The transferred toner image is finally fixed on the paper. After the transfer, the toner and charge remaining on the photoconductive drum 1 are removed by an erasing lamp and a cleaner, so that it can be used repeatedly again.

The laser beam 3 is a beam from a laser generator 9, which is passed through a mirror 10, a lens 11, an optical modulator 12, and lenses 13 and 1.
4, 15, a mirror 16, a polygon mirror 17, a scanning lens 18, and other optical systems for modulation and scanning.

An optical system with such a configuration uses expensive polygon mirrors, optical modulators, and scanning lenses, has low laser light usage efficiency, has a long optical path length and cannot be miniaturized, and requires a device to take timing of beam scanning. It had many drawbacks, such as poor beam scanning accuracy.

The present invention eliminates these drawbacks, simplifies the configuration of the optical system, and implements solid-state scanning without a rotating part.

FIG. 2 shows an example of the configuration of a printer according to the present invention.
The structure is the same as in FIG. 1 except for the laser optical system.

The laser optical system of this embodiment includes a laser generator 9, a mirror 1
9, a lens 20, a cylinder lens 21, a mirror 22, and a scanner 23''fr: The laser beam is modulated by the scanner 23 and the modulation scanner circuit 24, and scans the drum surface in the horizontal direction.

The main components of the optical system of this example are shown in FIG.
Lens 20. They are a cylinder lens 21 and a scanner 23. Suitable from gas laser generator or semiconductor laser generator?
- The laser beam 25id is emitted with the same diameter as the drum, and is expanded into a fan shape by the lens 20 and the cylinder lens 21, and is adjusted so that it forms a single thin line parallel to the drum axis on the photoconductive drum. The scanner 23 is provided close to the drum surface.

A long, thin beam of light focused on the drum in this way:
The image is modulated by the scanner 23 corresponding to each pixel.
Gives a row of light spots on the drum.

FIG. 4 is a sectional view of the scanner 23, in which the block electrode 27 and the control electrode 28 provided inside the transparent body 2728 are closer to the spacer 26 and face each other. A liquid crystal 29 whose optical properties change depending on the voltage is contained between the two electrodes. Electrochromic materials, PLZT (ferroelectric elements), etc. can be used instead of liquid crystals. The laser beam is projected onto the block electrode side as input light 30, and comes out as output light 31 from the control electrode side as a modulated elongated beam.

FIG. 5 shows the relationship between the block electrode 32 and the control electrode 33. The control electrode is made according to the dot density of the information desired to be recorded. For example, make it with a density of 8 pieces/throat. The block electrodes 32 are provided in a number divided by a plurality of control electrodes. For example, one block electrode is assigned to every 32 electrodes. If the number of recorded dots in the extra horizontal direction is 2048, then 64 block electrodes are required.

The scanner 23 is composed of a block electrode 27, a control electrode 28, and an electro-optic conversion material such as a liquid crystal.
Each piece acts as a light shutter, so the light beam 34 is
It becomes possible to modulate the light as a collection of light spots arranged in a row.

The modulation of light by the control electrode 28 and the block electrode 27 utilizes the modulation threshold of the electro-optic conversion material, and when the voltage between the block electrode and the control electrode exceeds a certain value, it operates as a light shutter. I'll keep it. The modulation scanner circuit 24 for optical modulation consists of pulse amplifiers for a group of control electrodes selectively connected in the same number as the number of block electrodes, and a switch circuit for switching and driving the pulse amplifiers.
128 loop amplifiers are required.

As described above, in this embodiment, a single light beam projected in the recording horizontal scanning direction is opened and closed for each pixel using a modulation scanner, and the optical system requires many lens groups and rotating mirrors. Therefore, it is possible to realize a solid-state optical system with a short optical path length. According to this embodiment, a small-sized, high optical efficiency, and highly reliable laser beam printer is possible.

FIG. 6 shows another embodiment of the present invention, which can be installed when the scanner 23 and the drum 1 cannot be brought close to each other, with little light loss and without deterioration of resolution. scanner 2
An optical fiber bundle 35 is provided between the scanner 23 and the drum to guide the point image of the scanner 23 onto the drum. As a special focus,
By using a phino whose refractive index changes in the axial direction and which has an imaging ability, the gap between the drum and the fiber 35 can be separated by 10 to 15 wm, which is advantageous in terms of the device configuration.

In the above description, the electrophotographic recording method has been described, but the present invention can also be applied to other recording methods.

[Brief explanation of the drawings] Figure 1 is a schematic diagram of the configuration of a conventional laser beam printer;
The figures are schematic diagrams of the structure of a laser beam printer according to the present invention, FIGS. 3, 4, and 5 are diagrams explaining the present invention in detail, and FIG. 6 is a schematic diagram of the structure of another embodiment of the present invention. - 1... Photoconductive drum, 9... Laser generator, 20...
...Shins, 21...Cylinder lens, 23...Scapoo, 1st country Figure 3 #, 4 Figure 23 5th and 6th figure

Claims (1)

[Claims] 1. In a laser beam printer that scans a photosensitive recording medium with laser light to record an image, there is a means for spreading the laser beam through a cylinder lens to form an elongated light beam in the horizontal scanning direction, and a means for spreading the light beam in the horizontal scanning direction. 1. A laser beam printer that records information by means of modulating the information using a plurality of electro-optical conversion elements arranged in a row and then projecting the information onto a photoreceptor.