JPH02190815A - Image forming device - Google Patents

Abstract

PURPOSE:To facilitate adjustment in assembly and constitution and to miniaturize the device by turning the flux of laser light into nearly collimated flux of light by a collimator lens, making it incident on an optical scanning means, reflecting it in a direction opposite to the arranged direction of an image carrier and then conducting it to the image carrier by a reflecting mirror. CONSTITUTION:The optically modulated flux of laser light from a laser light source 2 is made nearly collimated flux of light by the collimator lens 3 and made incident on a rotary polygon mirror 4. Respective elements are set so that the flux of laser light deflected with the rotation of the polygon mirror 4 may be reflected in the direction opposite to the direction of the photosensitive drum 1. After the flux of the laser light 9 from the polygon mirror 4 is reflected by the reflecting mirror 6, it is conducted to the surface of the photosensitive drum 1 by optical lenses 7 and 8 so as to perform scanning with light on the surface of the photosensitive drum 1. Thus, floor space for an optical scanning device is made about half at the time of arranging the device on one plane. Since the collimated flux of light is made incident on the rotary polygon mirror, the adjustment in assembly is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image forming apparatus, and in particular to an image forming apparatus that is modulated by a signal based on image information from an image information output unit of a computer, facsimile, document reading device, word processor, etc. An image forming apparatus that guides a light beam to a light scanning means, such as a rotating polygon mirror, and rotates the rotating polygon mirror to scan the surface of an image carrier such as a photosensitive drum and form image information. It is something.

(Prior Art) Image forming apparatuses that utilize light beams from, for example, semiconductor lasers that are optically modulated based on image information have been disclosed in Japanese Patent Laid-Open No. 52-48331, Japanese Patent Laid-Open No. 61-13759, and Publication No. 57-102609 and JP-A No. 62
It has been proposed in Publication No.-49316 and the like.

In these image forming devices, image information is converted into current pulses, a semiconductor laser emits a modulated laser beam, and the laser beam is deflected through a rotating polygon mirror serving as an optical scanning means to transfer the photosensitive drum to a photosensitive drum or the like. It scans the surface of the body with light. Image information is formed on the surface of the photoreceptor while continuously rotating the photoreceptor in the sub-scanning direction.

(Problems to be Solved by the Invention) In many conventional image forming apparatuses that utilize laser beams, each element such as a laser unit, a rotating polygon mirror, and an optical scanning system is arranged in a flat manner. . As a result, the entire optical scanning device is expanded in the horizontal direction, occupying a large space within the image forming device, and the arrangement of other elements is also subject to various restrictions.

In addition, as the size of the output paper increases from F4 size to A3 size, the scanning width of the laser beam becomes wider, and the distance from the rotating polygon mirror to the photoreceptor must be increased accordingly. As a result, the entire device becomes larger.

Furthermore, as the scanning density on the photoreceptor surface becomes finer, the number of rotations of the rotation amount surface mirror increases accordingly, and the load placed on the bearing of the motor serving as the scanning drive means increases. Furthermore, if the number of reflective surfaces of the rotating polygon mirror is increased instead of increasing the number of rotations of the rotating polygon mirror, the angle that can be scanned by one reflective surface becomes smaller, and the distance from the surface to the photoconductor is further increased by the amount of one rotation. There were problems such as the overall size of the device had to be increased.

On the other hand, in JP-A-52-48331, the entire device is constructed three-dimensionally, but since the laser beam from the laser light source is focused and incident on the rotating polygon mirror, the assembly and adjustment of the rotating polygon mirror is difficult. There was a problem that the optical path became complicated, and it became difficult to adjust the 7A optical path in particular.

The present invention secures a scanning range of a predetermined size on the image carrier surface by appropriately arranging each element such as a laser unit, a rotating polygon mirror, and an optical scanning optical system, while making it easy to adjust the assembly configuration. It is an object of the present invention to provide an image forming apparatus which is capable of reducing the size of the entire apparatus.

(Means for Solving the Problems) In the present invention, a laser beam from a laser light source that has been optically modulated based on the image↑4 report is guided onto an image carrier via a light scanning means, and the image carrier is When optically scanning the body and forming the image information, the laser beam from the laser light source is made into a substantially parallel beam by a collimator lens, and is incident on the optical scanning means.4 The laser beam from the optical scanning means is converted into the image. It is characterized in that the light is reflected in a direction opposite to the direction in which the image carrier is arranged, and then guided onto the image carrier by a folding mirror.

(Example) FIG. 1 is a schematic diagram of main parts of a first embodiment of the present invention.

In the figure, 1 is a photosensitive drum as an image carrier.

Its surface is provided with organic photoconductor, amorphous silicon, and selenium-based materials. Reference numeral 2 denotes a laser light source, which is composed of, for example, a semiconductor laser or a gas laser, and emits a laser beam that is optically modulated based on an image information signal from an image information output section 21. The figure shows a case where a semiconductor laser is used. Reference numeral 3 denotes a spherical or cylindrical collimator lens, which converts the laser beam from the laser light source 2 into a one-dimensional or two-dimensional parallel beam. 3a
is the optical axis of the collimator lens 3; 4 is the optical scanning means, which is composed of a rotating mirror having 4 to 20 reflective surfaces;
The reflective surface of the three-rotation surface l114, which is rotated at a constant speed around the rotating shaft 5a by the motor-dedicated driving means 5, has a high reflectance for the light beam with an oscillation wavelength of 760 nm to 800 nm from the semiconductor laser 2. A multilayer coating is applied on a material such as copper or aluminum.

Each element 71 is set so that when the laser beam from the collimator lens 3 is reflected by the rotating polygon jJ14, it is reflected in a direction opposite to the direction in which the photosensitive drum 1 is arranged. Further, the rotation speed of the motor 5 is detected by, for example, a Hall element, and is controlled to maintain a constant rotation speed.

Reference numeral 6 denotes a folding mirror, and its surface is coated with copper or a multilayer coating on a substrate so that the laser beam from the semiconductor laser 2 is reflected with a high reflectance. The laser beam 9 reflected by the rotating polygon Ill 4 is reflected in the direction of the photosensitive drum 1. 7.8 are each optical lenses,
It has an f-θ characteristic, and by guiding the laser beam 10 reflected by the folding mirror 6 onto the surface of the photosensitive drum and rotating the rotating polygon mirror 4, the surface of the photosensitive drum is scanned with light. ing.

In the figure, the laser beam is incident on the photosensitive drum 1 at an angle slightly inclined from a right angle.

This avoids the adverse effects of exposure to light and reflection of the laser beam on the surface of the ram l. Also, optical lens 7.8 and rotating polygon jJ! 4 so that their centers substantially coincide with each other.

In this embodiment, the collimator lens 3 and the optical lens 7.8 constitute a tilt correction system using so-called optical scanning. That is, even if the reflective surface of the rotating polygon mirror 4 is tilted significantly and the laser beam moves somewhat, the configuration is such that the incident imaging position of the laser beam on the surface of the photosensitive drum 1 does not change at all.

In this embodiment, the rotation axis 5a of the rotating polygon mirror 4 is the optical axis 3a.
Each element is arranged so that it is tilted against the

In this embodiment, in the above-described configuration, the laser beam modulated from the laser light source 2 is made into a substantially parallel beam by the collimator lens 3, and is deflected as the six-rotation polygon mirror 4 rotates, which is incident on the rotation polygon mirror 4. The laser beam is applied to the photosensitive drum.
Each element is set to reflect in the opposite direction. After the laser beam 9 from the rotating polygon @4 is reflected by the folding mirror 6, it is guided onto the surface of the photosensitive drum 1 by the optical lens 7.8, and the surface of the photosensitive drum 1 is erroneously scanned with light. Further, a beam detector (not shown) placed near the photosensitive drum detects the writing start position of the image information in the main scanning direction, and synchronizes the cueing of the image information in the main scanning direction. In this way, the image information output from the image information output section is formed on one surface of the photosensitive drum.

2nd, 3rd. FIG. 4 is a schematic diagram of the main parts of the second, third, and fourth embodiments of the present invention, respectively.

In the figure, elements that are the same as those shown in FIG. 1 are numbered.

In the 2'X embodiment shown in FIG.
The rotation axis 5a is perpendicular to the optical axis 3a. This reduces the accuracy with respect to inclination and uneven rotation of the rotating shaft 5a of the rotating polygon jJl11.

In the third embodiment shown in FIG. 3, an optical lens 7.8 having r-.theta. characteristics is arranged between the rotating polygon mirror 4 and the folding mirror 6. In this way, the optical lens 7.8 is placed in an area where the scanning width of the laser beam is narrow, which is close to the rotating polygon mirror 4 and away from the photosensitive drum l.
We are trying to downsize the 8.

In the fourth embodiment shown in FIG. 4, the rotation axis 5a of the rotating polygon mirror 4 is
is substantially perpendicular to the substrate surface of the device, and 2
The laser beam is reflected twice using a folding mirror 6.19. In addition, the optical lens 7.8 is replaced by a rotating polygon mirror 4.
and the folding mirror 6, and the optical lens 7.8
We are trying to make it more compact.

In each of the above embodiments, instead of providing the optical lens 7.8 with f-θ characteristics, the electric signal is applied in stages so that the laser beam has a constant speed at the center and ends of the scanning width on the photosensitive drum. The electric circuit may be configured to change continuously.

Further, although the case where a single conductor laser is used as the light source is shown, a laser element in which mu semiconductor lasers are integrated may be used as the light source.

(Effect of the invention) According to the present invention, each element is configured as described above.

By arranging each element of the optical scanning device in a stacked manner within multiple planes, the floor area of the optical scanning device can be reduced to approximately 1/2 compared to when the optical scanning device is arranged on one vehicle surface. It is possible to achieve an image forming apparatus that can be easily assembled and adjusted by effectively reducing the size of the entire image forming apparatus and by allowing parallel light beams to enter the rotating polygon mirror.

[Brief explanation of the drawing]

1st, 2nd. Figures 3 and 4 show the first, second, and
FIG. 7 is a schematic diagram of the main parts of the optical system of the third and fourth embodiments. In the figure, 1 is a photosensitive drum, 2 is a laser light source, 3 is a collimator lens, 4 is a rotating polygon mirror, 5 is a driving means, 6.19 is a folding mirror, 7 and 8 are optical lenses, 9 and 0 are optical axes, respectively. It is.

Claims (1)

[Claims] (1) A laser beam from a laser light source that is optically modulated based on image information is guided onto an image carrier through an optical scanning means, and the image carrier is optically scanned to form the image information. edge,
After the laser beam from the laser light source is made into a substantially parallel beam by a collimator lens and is incident on the optical scanning means, the laser beam from the optical scanning means is reflected in a direction opposite to the direction in which the image carrier is arranged. An image forming apparatus characterized in that light is guided onto the image carrier by a folding mirror.