JPH05333283A - Light scanning device - Google Patents

Abstract

PURPOSE:To actualize space-reducing and miniaturization by allowing light from a third mirror to reach a scanning surface passing between the first and the second mirrors as for an optical path leading the light reflected and deflected by a scanning member to the scanning surface by means of successively turning it back by three mirrors. CONSTITUTION:A laser beam LB reflected and deflected by the reflecting surface of a polygon mirror 112 being the scanning member is successively bent and led to a photosensitive drum 160 by the respective first and second mirrors 113a and 113b and a third spherical mirror 114. Thus the laser beam LB from the spherical mirror 114 reaches the photosensitive drum 160 passing between reflecting mirrors 113a and 113b in order to scan the photosensitive drum 116. Consequently the optical path of the laser beam LB incident on the reflecting mirror 113b and reflected, reaching the spherical mirror 114 and heading for the photosensitive drum 160 is superposed on the optical path of the laser beam LB heading for the reflecting mirror 113a from the polygon mirror 112, and a detour optical path 120 is formed en route so that an optical path length is made sufficiently long.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly to an optical scanning device having a scanning member which reflects and deflects light to scan the surface to be scanned.

[0002]

2. Description of the Related Art This type of optical scanning device is incorporated as a printer head in an image forming apparatus such as a digital copying machine or a laser beam printer.

An optical scanning device for scanning light on a surface to be scanned by reflecting and deflecting light by a scanning member uses an fθ lens or a curved mirror to obtain fθ characteristics for obtaining uniform velocity in scanning. An image optical system is adopted, and miniaturization of the image optical system has a great influence on miniaturization of a printer or the like.

Therefore, various attempts have been made in the past to simplify the structure of the optical scanning device and reduce its size.

[0005]

However, in order to simplify the structure of the optical scanning device and reduce the size thereof, if an image forming optical system is constructed with a small number of lenses or curved mirrors, the scanning member will be used in terms of optical performance. It is necessary to increase the optical path length to the surface to be scanned. This hinders miniaturization.

Due to such conflicting problems, the miniaturization of the device has not been sufficiently achieved although the miniaturization of the device is strongly desired.

Therefore, the present invention aims to provide an optical scanning device which does not have the above-mentioned problems by making it possible to sufficiently obtain the optical path length from the scanning member to the surface to be scanned with a small number of mirrors and a small space. This is an issue.

[0008]

In order to achieve the above-mentioned object, the present invention provides an optical scanning device having a scanning member which reflects and deflects light to scan the surface to be scanned. There is an optical path in which the deflected and deflected light is sequentially turned back by the first, second, and third mirrors and guided onto the surface to be scanned, and the light from the third mirror is between the first and second mirrors. It is characterized in that it reaches the surface to be scanned through.

The third mirror may be set such that the distance between the scanning member and the first mirror in the direction perpendicular to the optical path is equal to or smaller than that of the second mirror. it can.

[0010]

According to the above-mentioned structure of the present invention, the light reflected and deflected by the scanning member is sequentially bent by the first, second and third mirrors and guided to the surface to be scanned, which is then scanned. In order to scan the surface, the light from the third mirror is made to pass through the space between the first and second mirrors and reach the surface to be scanned so that the light enters the second mirror. Is reflected,
The optical path of the light that reaches the third mirror and goes to the surface to be scanned is
The scanning member overlaps the optical path of the light traveling from the scanning member to the first mirror and has a detour optical path on the way, so that the scanning member scans within a limited small space with a small number of mirrors. The optical path length to the surface can be made sufficiently long.

If the distance of the third mirror in the direction perpendicular to the optical path between the scanning member and the first mirror is set to be equal to or smaller than that of the second mirror, the detour optical path is set in the middle. The optical path to be carried can be formed in the space between the first and second mirrors.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a laser beam to which the present invention is applied.
3 shows a cross-sectional view of the printer. As shown in FIG. 1, this printer generally has a printer main body frame 1 in which a sheet storage portion 50, a print head 100, and an image forming cartridge 150 are stored.

The operator operating portion is provided on the left side surface in FIG. 1, and the left side in FIG. 1 is hereinafter referred to as the front side and the right side as the back side.

A photosensitive drum 160, a charging brush 171, a developing device 172, a transfer roller 180, and a cleaning blade 185 are integrally housed in the image forming cartridge 150.

The photosensitive drum 160 is rotationally driven in the direction of arrow a, and the surface thereof is first charged to a predetermined potential by the charging brush 171, and then by the laser beam LB incident from the slit 152 formed in the housing 151. An electrostatic latent image is formed by receiving image exposure.

This electrostatic latent image is developed with toner by passing through the developing sleeve 173 of the developing device 172.

On the other hand, a maximum of about 50 sheets are stacked on the tray 55 of the sheet accommodating portion 50, and the sheet is fed between the pinch roller 70 based on the rotation of the sheet feeding roller 61 in the direction of arrow b. The sheet is sandwiched and sent obliquely upward to the right in FIG. 1, and is conveyed from the sheet guide slit 153 of the housing 151 to the nip portion between the photosensitive drum 160 and the transfer roller 180.

Here, the toner image on the photosensitive drum 160 is transferred to the sheet, and the sheet is sent to the thermal fixing device 200 through the sheet guide slit 153, and is discharged face down from the discharge roller 211 to the upper surface of the main body frame 1 or in FIG. The tray 220 which is almost upright as shown by the chain double-dashed line
Is discharged face up to the front side of.

After the transfer, the photosensitive drum 160 is continuously rotated in the direction of the arrow a, the residual toner is scraped off the surface of the drum by the cleaning blade 185, and is stored in the waste toner chamber 186 provided in the upper portion of the housing 151.

The sheet accommodating portion 50 is configured as a sheet accommodating chamber 51 with the tray 55 for holding the sheets in a stacked state and the bottom surface of the housing 101 of the print head 100 described in detail below.

The tray 55 can be extended to the front side (left side in FIG. 1), and its length is adjusted according to the sheet size.

A pair of width regulating plates 59 which are slidable in the width direction are installed on the tray 55 so that sheets of various sizes can be regulated in the width direction.

On the other hand, on the front side of the main body frame 1, an inclined portion in FIG. 1 is formed as an opening 10 for inserting a seat.
Are covered by a cover 11. The cover 11 can be opened and closed by being rotatable in the vertical direction with the pin 12 as a fulcrum.

By the way, in the sheet storage chamber 51, the lower surface is constituted by the tray 55, and the upper surface is constituted by the bottom surface of the housing 101 of the print head 100. It is inclined toward. Further, the accommodating portion 51 is tapered toward the back side.

The sheet is inserted onto the tray 55 through the opening 10 opened by the cover 11.

At this time, the operator can set the sheet on the tray 55 while being positioned on the front side of the main body frame 1, and the upper and lower surfaces of the accommodating portion 51 in which the leading end of the inserted sheet is tapered. Since it is guided by, it is easy to replenish the seat.

Also, the housing 1 of the print head 100
As shown in FIGS. 1 and 6, a rib 201 for guiding the sheet is provided on the bottom surface of 01. The arrow in FIG. 6 indicates the sheet feeding direction.

The inner spacing of the ribs 201 is a postcard size, and the ribs 201 guide both side edges of the postcard-sized sheet to be fed to prevent skew during feeding.

Further, in the case of a sheet of A4 size which is wider than the postcard size, the rib 201 prevents the rear end of the uppermost sheet to be fed from being turned up.

The spacing of the ribs 201 is not limited to the postcard size, but may be adapted to A4 size to prevent the trailing edge of the sheet of a larger size from curling up.

As shown in FIG. 7, postcard size and A4 size
It is also possible to provide a plurality of pairs of ribs 201, 202, etc. corresponding to sheets of a plurality of sizes such as sizes.

When the sheet guide is formed on the bottom surface of the housing 101 of the print head 100 as described above, the sheet feeding performance can be improved and no special member is required, so that the structure is not particularly complicated. ..

As shown in FIG. 2, the print head 100 includes a light source unit 110 including a semiconductor laser and a collimator lens in a housing 101, and a folding mirror 11.
1, a polygon mirror 112 as a scanning member, two folding mirrors 113a and 113b, a spherical mirror 114, a sensor 115 for detecting a scanning start position, and a cylindrical lens 117 for correcting a surface tilt of the polygon mirror 112 are accommodated.

The laser beam LB is modulated on the basis of image information, emitted from the light source unit 110, enters the polygon mirror 112 through the cylindrical lens 117 and the folding mirror 111, and rotates the polygon mirror 1.
The light is reflected by twelve reflecting surfaces 112a and is deflected on one plane at a constant angular velocity (FIGS. 2 and 5).

The deflected laser beam LB is further incident on the slit 152 of the image forming cartridge 150 from the spherical mirror 114 through the reflection mirrors 113a and 113b and the emission window 105 of the housing 101, and then onto the photosensitive drum 160. An image is formed, and this is scanned to perform image exposure. A window glass 106 is attached to the window 105.

The printhead 100 includes a housing 10
1 and a cover 203. FIG. 3 shows the state when the cover is attached, and FIG. 2 shows the state when the cover is removed.

Reference numeral 204 in the drawing denotes a print head mounting portion provided on the printer body frame 1, and the print head 100 is screwed to the printer body frame 1 at three points of mounting holes 205 to 207. Reference numeral 208 denotes a screw for fixing the screw.

Below the mounting hole 205, there is a print head mounting member (not shown) provided on the printer body frame 1.

The mounting holes 205 to 207 are holes not only for fixing the print head 100 to the printer body frame 1 but also for fixing the cover 203 to the housing 101.

In the other part of the cover 203, the mounting holes 206a and 207a adjacent to the mounting holes 206 and 207 of the print head 100 are used to fix the cover 203 to the print head mounting portion 204 with screws 209.

However, the mounting holes 206a, 2a of the cover 203,
07a mounting, these mounting holes 206a, 207a
By aligning the position of with the mounting holes 206 and 207 of the housing 101, the mounting screw 208 of the housing 101 can also be used for mounting.

Housing 101 of printhead 100
There are no holes except the mounting holes 205 to 207 so that the laser beam does not leak and the rigidity of the printer body frame 1 is enhanced. The window 105 for emitting the laser beam is provided on the cover 203 side.

(1) The position of the print head 100 with respect to the printer body frame 1 is determined in consideration of the following points.

The emission direction of the laser beam LB is set to the side of the print head 100.

The distance from the emission position of the print head to the photosensitive drum 160 is increased.

The reasons for this are as follows: a: In terms of rigidity, it is not desirable to make the slit of the exit window 105 in the housing 101.

B, The angle of the exit window 105 should be set to be 45 ° or more from the horizontal. This makes it difficult for the hair of the assembling operator to adhere to the window 105.

The other reason is that, a, if the distance is long, even if the toner is scattered around the photosensitive drum 160, it is difficult to reach the emitting portion of the laser beam LB.

B, the beam diameter at the position of the window 105 is increased, and the influence of dust such as toner is reduced.

C. If the positions of the polygon mirror and the exposure point are set as far as possible, the angle of view can be narrowed.
This is advantageous in terms of beam uniformity, accuracy in design and adjustment.

However, this is contrary to the miniaturization of the print head 100, the miniaturization of the image forming cartridge 150, and the miniaturization of the entire printer body frame 1.

Therefore, the print head 100 according to the present embodiment.
Is the polygon mirror 112 and the photosensitive drum 1 as described above.
The three mirrors 113 are provided in the optical path between the exposure point E on 60
The optical paths are bent by sequentially disposing a, 113b, and 114 as the first to third mirrors.

If the reflectance of the mirror is about 90% per sheet, the reflectance of three sheets is about 70%, but there is no particular problem at this level.

To increase the degree of freedom in the arrangement of the optical system,
It is possible to increase the number of mirrors to 3, 4, 5, and so on. However, it is preferable to use three in order to balance the relationship with the light attenuation.

In this embodiment, the three mirrors 113 are used.
One of the mirrors a, 113b and 114 is a spherical mirror, and the toric lens 116 and the spherical mirror 114 are used.
Fθ characteristic is provided by the combination with.

The bending of the scanning line caused by the incidence of the laser beam LB at an angle on the spherical mirror 114 is dealt with by offsetting the optical axis of the toric lens 116.

Particularly, the polygon mirror 11 which is a scanning member.
The laser beam LB reflected and deflected by the second reflection surface 112a is reflected by the first, second and third mirrors 113a, 11a.
The laser beam LB from the spherical mirror 114, which is the third mirror, is sequentially bent by 3b and 114 and guided onto the photosensitive drum 160 that is the surface to be scanned. The first and second folding mirrors 113a and 113b are passed between the folding mirrors 113a and 113b to reach the photosensitive drum 160.
The optical path of the laser beam LB which is incident on and reflected by the folding mirror 113b, which is a mirror of No. 3, reaches the spherical mirror 114, which is a third mirror, and travels toward the photosensitive drum 160.
The detour optical path 120 as shown in FIG. 4 overlaps with the optical path of the laser beam LB traveling from the polygon mirror 112 to the folding mirror 113a which is the first mirror.
Therefore, the polygon mirror 112, which is the scanning member, and the photosensitive drum 160, which is the surface to be scanned, are within a limited small space with a small number of mirrors.
The optical path length up to can be made sufficiently long.

In addition, since the distance between the toric lens and the spherical mirror can be relatively freely set in a limited space, the degree of freedom in the optical design itself is increased.

The spherical mirror 114, which is the third mirror.
The distance S between the polygon mirror 112 which is the scanning member and the folding mirror 113a which is the first mirror in the direction perpendicular to the optical path is equal to or greater than that of the folding mirror 113b which is the second mirror. If it is set small, the optical path having the bypass optical path 120 in the middle of the first optical path,
Folding mirrors 113a and 113b that are second mirrors
It can be formed in the space within the space.

(2) Correspondence regarding the rigidity of the optical housing.

The housing and cover material of the print head 100 are made of polycarbonate resin mixed with glass fiber.

The following two points are taken into consideration with respect to vibration.

A. The frequency of the first mode, that is, the resonance point is raised above the rotation frequency of the polygon mirror. If this is not possible, try not to match each other.

[0065] B, always the frequency of the first mode 100H _Z
More than that.

The resonance frequency Ω _n can be generally expressed by the following equation.

[0067]

[Equation 1]

From this equation, it can be seen that increasing h is most effective for increasing the resonance frequency. If h is increased, E and t can be decreased.

Therefore, this time, at the same time as designing with large h, the filling rate of the glass fiber is set to 40%.

The thickness t of the housing and the cover is set to 2
Set to mm. When the filling rate of the glass fiber is lowered to 40% as compared with the ordinary case, the cost is reduced.

B, the mass decreases. (The resonance frequency increases.) C, elasticity is generated, and this can be used for fixing the optical element.

D, The die lasts a long time.

There is an advantage.

Further, reducing the wall thickness t reduces the amount of material used in proportion to the wall thickness t, so that the effect of cost reduction is great and the weight can be reduced.

In addition to the above, the housing 101 of the print head 100 is not provided with a window 105 for emission, and the whole is continuous so as not to be divided in the middle, which greatly contributes to the strength. ..

Further, since the beam emission position is brought to the side, it is possible to greatly contribute to the improvement in rigidity.

The following table shows specific design values of the optical scanning optical system by the print head 100 of the present embodiment.

[0078]

[Table 1]

[0079]

According to the present invention, the light reflected and deflected by the scanning member is sequentially bent by the first, second, and third mirrors and guided onto the surface to be scanned, and the surface to be scanned is scanned. For scanning up, the light from the third mirror is arranged to pass between the first and second mirrors and reach the surface to be scanned, so that the light enters the second mirror. Reflected, third
The optical path of the light that reaches the mirror of (1) and is directed to the surface to be scanned overlaps the optical path of the light that travels from the scanning member to the first mirror,
Moreover, since it is formed so as to have a detour optical path on the way, the optical path length from the scanning member to the surface to be scanned can be made sufficiently long in a limited small space with a small number of mirrors, and a sufficient optical path can be obtained. It is possible to miniaturize the optical scanning device that guarantees the length and has a simple structure and high accuracy.

If the distance of the third mirror in the direction perpendicular to the optical path between the scanning member and the first mirror is set to be equal to or smaller than that of the second mirror, the detour optical path is set in the middle. The own optical path can be formed in the space between the first and second mirrors, and further miniaturization can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional view of a laser beam printer to which the present invention is applied.

FIG. 2 is a perspective view of the relationship between the print head and the photosensitive drum of FIG. 1 as viewed with the print head cover removed.

FIG. 3 is a perspective view of the relationship between the printer head and the photoconductor drum of FIG. 1 as viewed without removing the cover of the print head.

FIG. 4 is a side view of a scanning optical system.

FIG. 5 is a plan view of a scanning optical system.

FIG. 6 is a perspective view showing the bottom surface of the housing of the print head.

FIG. 7 is a bottom cross-sectional view showing another embodiment of a printhead housing.

[Explanation of symbols]

 112 polygon mirror 113a, 113b folding mirror 114 spherical mirror 160 photosensitive drum LB laser beam

Claims (2)

[Claims] 1. An optical scanning device having a scanning member for reflecting and deflecting light to scan a surface to be scanned, wherein the light reflected and deflected by the scanning member has three mirrors, first, second and third mirrors. The optical scanning has an optical path which is sequentially turned back at to guide the light to the surface to be scanned, and the light from the third mirror passes through between the first and second mirrors to reach the surface to be scanned. apparatus. 2. The third mirror is set such that the distance in the direction perpendicular to the optical path between the scanning member and the first mirror is equal to or smaller than that of the second mirror. The optical scanning device according to.