JP2001159738A - Multibeam scanning optical system and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multibeam scanning optical system which can realize high-grade printing at a high speed with a relatively simple constitution, and an image forming device using the same. SOLUTION: This scanning optical system has an incident optical means which guides plural luminous fluxes emitted from a light source means having plural light emitting parts arranged apart from each other in a main scanning direction to a deflecting means, a scanning optical means which images plural luminous fluxes deflected by the deflecting means onto a surface to be scanned and a synchronism detecting optical means which condenses a part of the plural luminous fluxes deflected by the deflecting means onto a slit surface via a return mirror by a lens section, then guides the luminous fluxes to the synchronism detecting element and controls the timing of the scanning start position on the surface to be scanned by using the signal from the synchronism detecting element. The respective elements are so set as to satisfy a condition equation (A) when the focus misalignment quantity within the main scanning section of the luminous fluxes guided to the synchronism detecting element viewed from the slit is defined as δM and the focus misalignment quantity at each image height on the surface to be scanned as δX.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam scanning optical system and an image forming apparatus using the same, and more particularly to a laser beam printer or a digital copying machine capable of high-speed and high-quality printing with a relatively simple structure. And the like.

[0002]

2. Description of the Related Art Conventionally, a scanning optical system used in an image forming apparatus such as a laser beam printer or a digital copying machine guides a light beam emitted from a light source to a deflecting means by an incident optical means, and the deflecting means uses the deflecting means. The deflected light beam is spot-formed on the photosensitive drum surface, which is the surface to be scanned, by the scanning optical means, and the light beam is optically scanned on the photosensitive drum surface.

[0003] In recent years, demands for higher speeds have been increasing along with higher performance and higher functions of image forming apparatuses. To meet this demand, the use of a plurality of light sources has been studied. For example, Japanese Patent Application Laid-Open No. 9-54263 proposes a multi-beam scanning optical system using a multi-beam laser chip that emits a plurality of laser beams aligned in a straight line from one chip as a light source.

[0004]

(Problem 1) In such a multi-beam scanning optical system, a synchronization detecting optical unit (BD optical system) immediately before an image signal is written in order to accurately control an image writing position. Is generally provided.

FIG. 22 is a sectional view (main scanning sectional view) of a main part of a conventional multi-beam scanning optical system in the main scanning direction. In the figure, reference numeral 51 denotes a light source unit, which has two light emitting units (light sources) made of, for example, semiconductor lasers. The two light emitting units are arranged apart from each other in the main scanning direction and the sub-scanning direction. Reference numeral 52 denotes an aperture stop, which shapes a light beam emitted from each light emitting unit into a desired optimum beam shape. 5
Reference numeral 3 denotes a collimator lens, which converts a light beam that has passed through the aperture stop 52 into a substantially parallel light beam. Numeral 54 denotes a cylindrical lens having a predetermined refractive power only in the sub-scanning direction. Each element such as the aperture stop 52, the collimator lens 53, and the cylindrical lens 54 constitutes one element of the incident optical means 62.

Reference numeral 55 denotes a deflecting means, which comprises, for example, a rotating polygon mirror, and is rotated at a constant speed in a direction indicated by an arrow A in the figure by a driving means (not shown) such as a motor. Reference numeral 56 denotes scanning optical means having fθ characteristics, and the first and second two fθ
It has a lens. The scanning optical means 56 has a tilt correction function by making the vicinity of the deflection surface 55a of the optical deflector 55 and the vicinity of the photosensitive drum surface 57 as the surface to be scanned conjugate in the sub-scan section.

Reference numeral 58 denotes a folding mirror (hereinafter, referred to as a “BD mirror”), which transmits a plurality of light fluxes (BD light fluxes) for detecting a synchronization signal for adjusting the timing of a scanning start position on the photosensitive drum surface 57. The light is reflected to a synchronization detection element 61 described later. Reference numeral 59 denotes a slit (hereinafter, referred to as a “BD slit”), which is disposed at a position equivalent to the photosensitive drum surface 57. Reference numeral 60 denotes an imaging lens (hereinafter, referred to as a “BD lens”) for making the BD mirror 58 and the synchronization detecting element 61 have a conjugate relationship, and corrects surface tilt of the BD mirror 58. I have. Reference numeral 61 denotes an optical sensor as a synchronization detecting element (hereinafter, referred to as a “BD sensor”).
It is. The folding mirror 58, the BD slit 59,
Each element such as the BD lens 60 and the BD sensor 61 constitutes one element of a synchronization detecting optical unit (BD optical system).

In FIG. 1, BD detection is performed for each BD light beam, and the timing of the scanning start position of image recording on the photosensitive drum surface 57 is adjusted for each BD light beam using the output from the BD sensor 61. I have.

In a multi-beam optical scanning optical system having a plurality of light-emitting portions (light sources), an image to be printed deteriorates when the interval between the light sources in the main scanning direction changes as the scanning proceeds for various reasons. Further, even if the interval between the light emitting units in the main scanning direction does not change during scanning, if the writing start position is shifted between the light emitting units, the printed image is also deteriorated.

One of the causes of the above-mentioned phenomenon may be that there is a difference between the amount of shift of the focus position of the BD light beam on the BD slit surface and the amount of shift of the focus position of the scanning light beam on the surface to be scanned.

A description will be given below with reference to FIGS. Note that, in order to prevent the figure from being difficult to see, FIG.
(A), FIG. 18 (A), FIG. 20 (A), and FIG. 21 (A) omit the marginal ray.

FIG. 16A shows a state in which each light beam (A and B rays in this case) is focused on one end on the BD slit in the main scanning direction. The A ray scanned from left to right in the drawing enters the BD sensor only when it reaches the right end of the BD slit. At this time, the BD sensor outputs a signal indicating that the A ray has entered. Next, the B ray scanned from left to right enters the BD sensor only when it reaches the right end of the BD slit just like the A ray,
The BD sensor outputs a signal indicating that the B ray has entered. By detecting the timing of these two signals, the timing of the writing start position of the A and B rays is adjusted.

However, when the focus position of the A and B rays passing through the BD optical system in the main scanning cross section is shifted by δM toward the near side, that is, toward the deflecting means as shown in FIG. A phenomenon occurs, and the writing start positions of the A and B rays are shifted. If there is no defocus, the light beam A condenses at the right end of the BD slit and finally arrives at the BD sensor at the timing when it begins to be defocused, and has already been incident on the BD sensor surface (the right broken line in the figure). Actually, the light beam starts to enter the BD sensor when the A light beam comes to the solid line on the right side in the drawing, and the writing timing of the A light beam is advanced by an amount corresponding to the deviation between the broken line and the solid line. Conversely, when the B ray should start to enter the BD sensor at the time of the broken line on the left side, it cannot be entered due to defocus.
Since the light can be incident on the sensor, the writing timing of the B ray is delayed by the amount of shift between the left broken line and the left solid line. As a result, the writing start positions of the A and B rays are shifted by the distance between the two broken lines on the BD slit surface.

A and B ray write start position deviation amounts δY
Is determined from the defocus amount δM and the incident angle θ [rad] (0 [rad] in a state parallel to the optical axis of the BD optical system), and can be approximately described as follows.

ΔY = δM × θ (1) Similarly, the maximum deviation amount δ of the write start position between the light emitting units.
Ytotal indicates the maximum angle difference between incident angles as θmax [rad
], ΔYtotal = δM × θmax ‥‥‥‥ (2)

Accordingly, when the maximum allowable deviation of the writing start position between the respective scanning lines is δYmax, and the maximum allowable defocus amount determined from δYmax is δMmax,
The multi-beam scanning optical system needs to be configured such that the defocus amount δM satisfies | δM | ≦ δMmax = δYmax / θmaxｍ (3).

It is preferable that δYmax is about half or less of the resolution in the sub-scanning direction. If it exceeds this, adjacent horizontal lines will start to appear shifted, and the printed result will be very hard to see.

Incidentally, δYmax = 10 μm (120
0 dpi), θmax = 0.5 [ra
d], δMmax = 1.15 mm.

However, the above equations (1) to (3) hold when only the BD optical system is out of focus, and the same amount of defocus is also present on the surface to be scanned as in the BD optical system. In the case where it occurs in the direction (in FIG. 17, on the deflecting unit side), the writing position shift of the A and B rays called the dot shift hardly occurs. FIG. 18 shows the focus position in the main scanning section of the A and B rays passing through the BD optical system.
Suppose that it is shifted by δM toward the near side, that is, the deflecting means side as shown in FIG. At this time, as described above, a dot shift occurs between the light beams A and B, but if the focus position is shifted by δM uniformly on the surface to be scanned, as shown in FIG. A shift will occur.

However, the ideal image plane (scanned surface) is δM
When the light beams A and B are incident on the ideal image plane (scanned surface), the distance between the light beams A and B almost disappears. FIG. 18C illustrates the positional relationship between the light rays near the axis, and a triangle having the principal ray of the A and B light rays as the hypotenuse and a straight line at the position δM from the surface to be scanned as the base, and FIG. ) Indicate that the original A and B rays indicated by broken lines and the triangle having the BD slit surface as the base are almost congruent, indicating that there is no dot shift. However, in such a case, the position of the best spot position and the position on the surface to be scanned are shifted. However, if the focus position is within the allowable depth range, the image quality is hardly affected.

Although the above description has been made on the case where the focus position is shifted to a position short of the BD slit, even if the focus position is shifted to the back of the BD slit, the same as described above can be understood from FIGS. I can say that.

From the above description, it can be seen that, if the focus position is uniformly shifted on the surface to be scanned, the image will be deteriorated unless the focus position in the BD optical system is similarly shifted. If the focus shift amount on the scanned surface and the focus shift amount in the BD optical system are separately standardized, a large dot shift may occur if the respective focus shifts occur in opposite directions. Can be expected. Further, when the image surface is greatly curved on the surface to be scanned, it can be easily predicted that the interval between the light beams changes according to the curvature. Therefore, it is necessary to configure the multi-beam scanning optical system so that the focus shift amount δX of each image height on the surface to be scanned satisfies | δX−δM | ≦ δMmax = δYmax / θmax (4) according to the equation (3). You can see that.

Of course, when the angles of incidence of the respective light beams on the surface to be scanned are exactly the same, the deviation of the write start position between the scanning lines is the same, and the write start position is shifted as a whole and the write start position for each light emitting unit is shifted. No deviation occurs.

However, in order to achieve the above-described state, the arrangement of the light emitting units is not shifted in the main scanning direction.
That is, this is only possible when the light beams are arranged in a line in the sub-scanning direction, or when the principal rays of each light beam are crossed on the polygon mirror surface using a relay optical system. With respect to the former, usually, when each light emitting unit is arranged in such a manner, particularly when the sub-scanning direction is configured as an enlargement system, the distance between each light emitting unit is too short, about several μm to about several tens μm (usually commercially available) (The distance between the light emitting units of the multi-laser is about 100 μm), crosstalk occurs, stable oscillation cannot be performed, such as a difference in the light amount of each light emitting unit, and the life tends to be shortened. Regarding the latter, if a relay optical system is used, the number of necessary optical elements increases, which is not preferable in terms of space and cost.

In the case of a multi-beam scanning optical system having no BD slit in the BD optical system, the BD
The edge of the sensor plays the role of a BD slit, the right end of the BD slit is the left end of the BD sensor effective section, and the BD slit is
What is necessary is just to read by replacing the slit surface with the light receiving surface of the BD sensor.

In the above description, the scanning direction is from the left to the right in the figure. However, even if the scanning direction is reversed, a BD slit for determining the writing start timing is provided from the right end to the right (not shown) from the right end. The same is true, except that it changes to the left end of the BD slit. (Problem 2) As shown in FIG. 22, in a multi-beam scanning optical system that performs BD detection for each BD light beam, the focus position of the BD light beam is changed to the BD slit surface due to a lens manufacturing error, an assembly error, a lens focus error, or the like. If not,
(Because it becomes difficult to understand when considering the timing of BD with a light beam having a width, it is considered as a main ray of each light beam in the following.) Except when the light beam is incident parallel to the optical axis of the BD optical system, There is a problem that the timing at which the principal ray of the BD light flux grazes the edge of the BD slit differs from before the defocusing, and the writing position of the image shifts.

FIGS. 29 (A), (B) and (C) show the positional relationship of the principal ray of a part of each light beam (BD light beam) emitted from two light emitting portions (light sources). FIG. FIG. 6A shows the positional relationship between the principal rays of each light emitting portion when the BD light flux is ideally free from defocus, and FIG. 6B shows each light emission when the BD light flux is out of focus. FIG. 4C shows the positional relationship of the principal rays of each light emitting unit when the focusing state on the BD slit surface is improved by some method.

Originally, the timing of the writing start position on the surface to be scanned is set by the light beam that blurs one end of the BD slit as shown in FIG. When the focus shift occurs, the original ray (indicated by a solid line in FIG. 4) of the A ray becomes B ray.
The actual writing position of the A ray which is shielded by the D slit is determined by the ray indicated by the broken line. In other words, the writing start position of the A ray shifts by an amount corresponding to the transition of the state of the A ray from the solid line to the state of the broken line. The same can be said for the B ray, and the writing start position is advanced by the difference between the solid line and the broken line. Therefore, the shift of the writing start position between the A and B rays is shifted by the width of the solid line on the BD slit surface.

Further, the write start position deviation amount δY of the A and B rays
Is determined from the defocus amount δM and the incident angle θ (0 ° in a state parallel to the optical axis of the BD optical system), and can be approximately described as follows.

ΔY = δM · tan (θ) (5) Similarly, the total write start position deviation amount δY tot
al is determined as follows: δY total = δM · tan (θmax) (6) where θmax is the maximum angle difference between the incident angles.

Accordingly, if the maximum allowable deviation of the writing start position between the respective scanning lines is δYmax and the maximum allowable deviation of the focus determined by δYmax is δMmax, the deviation δM of the focal point is | δM | ≦ δMmax = δYmax / It is necessary to configure the multi-beam scanning optical system so as to satisfy tan (θmax) (7).

By the way, δYmax = 11 μm, θmax
= 0.5 °, δMmax = 1.26 mm.

Of course, when the incident angles of the respective light beams on the surface to be scanned are exactly the same, the writing position shifts between the scanning lines are uniformly the same, and only the writing position shifts as a whole and the writing position shifts with respect to each light emitting portion. Does not occur.

An object of the present invention is to provide a multi-beam scanning optical system capable of realizing high-speed and high-quality printing with a relatively simple configuration and an image forming apparatus using the same.

[0035]

According to a first aspect of the present invention, there is provided a multi-beam scanning optical system which guides a plurality of light beams emitted from a light source having a plurality of light emitting portions arranged apart from a main scanning direction to a deflecting means. Incident optical means for emitting light, scanning optical means for forming a plurality of scanning lines by forming a plurality of light beams deflected by the deflecting means on a surface to be scanned, and a plurality of light beams deflected by the deflecting means. After a part of the light is condensed on the slit surface by the lens unit, the light is guided to the synchronous detection element, and the timing of the scanning start position on the surface to be scanned is adjusted using the signal from the synchronous detection element. A multi-beam scanning optical system comprising:
| ΔM1 | ≦ δYmax / tan (θmax) (where, δM1 is the focus position deviation amount in the main scanning cross-section of the light beam guided to the synchronous detection element viewed from the slit. ΔYmax: acceptable Dot position shift amount for each scanning line θmax: the maximum angle difference between the incident angles of the respective light beams used for the synchronization detection on the slit surface).

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, the permissible dot position shift amount for each scanning line is equal to or less than half the resolution in the sub-scanning direction.

According to a third aspect of the present invention, in the first aspect of the present invention, the focus position of the light beam guided to the synchronization detecting element in the main scanning section is relatively shifted from the slit to the optical axis of the synchronization detecting optical means. It is characterized by comprising a correcting means for shifting in the direction.

According to a fourth aspect of the present invention, in the first aspect of the present invention, there is provided a correcting means for moving the position of the slit or a unit including the slit in the optical axis direction of the synchronization detecting optical means. I have.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the lens portion is provided in an optical path between the deflecting means and the slit, and the lens portion is disposed in the optical axis direction of the synchronization detecting optical means. It is characterized in that it comprises a correction means for moving it.

According to a sixth aspect of the present invention, in the first aspect of the invention, at least a part of the lens constituting the lens unit is integrated with the scanning optical unit, and the lens unit is not integrated with the scanning optical unit. It is characterized in that at least a part of the lens and a correcting means for moving the slit in the optical axis direction of the synchronization detecting optical means are provided.

According to a seventh aspect of the present invention, in the first aspect, the lens unit is integrated with the scanning optical unit, and at least a part of the optical element of the scanning optical unit is moved in the optical axis direction of the scanning optical unit. And a correcting means for moving the slit in the optical axis direction of the synchronization detecting optical means.

According to an eighth aspect of the present invention, in the first aspect of the invention, at least a part of the lens constituting the lens unit is integrated with the scanning optical means, and at least a part of the lens constituting the scanning optical means is mainly used. It is characterized by comprising a correction means for moving in the scanning direction.

A multi-beam scanning optical system according to a ninth aspect of the present invention includes: an incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from the main scanning direction to a deflecting unit; A scanning optical unit for forming a plurality of scanning lines by forming an image on the surface to be scanned with the plurality of light beams deflected by the deflecting unit, and slitting a part of the plurality of light beams deflected by the deflecting unit by a lens unit After focusing on a surface, the light is guided to a synchronous detection element, and the timing of a scanning start position on the surface to be scanned is controlled for each of the plurality of light fluxes using a signal from the synchronous detection element. A multi-beam scanning optical system having a focus position shift amount δM1 in a main scanning section of a light beam guided to the synchronous detection element as viewed from the slit. On the scanning plane It is characterized by comprising a correction means for correcting the dot position deviation for each scan line.

According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the dot displacement amount is １ ／ of the resolution in the sub-scanning direction.
It is characterized as follows.

An eleventh aspect of the present invention is characterized in that, in the ninth aspect of the present invention, the plurality of light emitting units are arranged apart from each other in the main scanning direction and the sub-scanning direction.

A twelfth aspect of the present invention is characterized in that, in the eleventh aspect of the present invention, the slit is inclined in the sub-scanning direction in accordance with the amount of dot displacement for each scanning line on the surface to be scanned.

According to a thirteenth aspect of the present invention, in the eleventh aspect of the present invention, the optical axis of the optical means for synchronizing detection is provided by changing the slit or a unit including the slit in accordance with a dot position shift amount for each scanning line on the surface to be scanned. It is characterized by comprising rotating means for rotating around.

According to a fourteenth aspect of the present invention, there is provided a multi-beam scanning optical system, comprising: an incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from the main scanning direction to a deflecting unit; Scanning optical means for forming a plurality of scanning lines by forming a plurality of light beams deflected by the deflecting means on a surface to be scanned, and a part of the plurality of light beams deflected by the deflecting means by a lens unit Light is guided to the synchronous detection element,
A multi-beam scanning optical system comprising: a synchronization detection optical unit that controls a timing of a scanning start position on the surface to be scanned by using a signal from the synchronization detection element for each of the plurality of light fluxes. | ΔM2 | ≦ δYmax / tan (θmax) (where, δM2 is the focus position deviation amount in the main scanning section of the light beam guided to the synchronous detection element viewed from the light receiving surface of the synchronous detection element δYmax : Allowable dot position shift amount for each scanning line θmax: maximum angle difference between incident angles of light beams used for synchronization detection on the light receiving surface.

A fifteenth aspect of the present invention is characterized in that, in the fourteenth aspect of the present invention, the permissible dot shift amount for each scanning line is equal to or less than half the resolution in the sub-scanning direction.

According to a sixteenth aspect of the present invention, in the invention of the fourteenth or fifteenth aspect, the focus position of the light beam guided to the synchronization detecting element in the main scanning section is relatively set with respect to the light receiving surface of the synchronization detecting element. It is characterized in that a correction means for shifting the detection optical means in the optical axis direction is provided.

According to a seventeenth aspect, in the fourteenth or fifteenth aspect, the correction means for moving the position of the synchronization detecting element or a unit including the synchronization detecting element in the optical axis direction of the synchronization detecting optical means is provided. It is characterized by having.

According to an eighteenth aspect of the present invention, in the invention of the fourteenth or fifteenth aspect, the lens portion is provided in an optical path between the deflecting means and the synchronization detecting element. It is characterized by comprising a correction means for moving in the optical axis direction.

According to a nineteenth aspect of the present invention, in the invention of the fourteenth or fifteenth aspect, at least a part of the lens constituting the lens unit is integrated with the scanning optical unit, and the lens is not integrated with the scanning optical unit. And a correcting means for moving at least a part of the lens in the optical axis direction of the synchronization detecting optical means.

According to a twentieth aspect of the present invention, in the invention of the fourteenth or fifteenth aspect, the lens unit is integrated with the scanning optical unit, and at least a part of the optical elements of the scanning optical unit is moved in the optical axis direction of the scanning optical unit. And a correction means for moving to

According to a twenty-first aspect of the present invention, at least a part of the lens constituting the lens portion is integrated with the scanning optical means, and at least a part of the lens constituting the scanning optical means is provided. , In the main scanning direction.

A multi-beam scanning optical system according to a twenty-second aspect of the present invention includes: an incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from the main scanning direction to a deflecting unit; A scanning optical unit that forms an image of a plurality of light beams deflected by the deflecting unit on a surface to be scanned, and a part of the plurality of light beams deflected by the deflecting unit after being condensed on a slit surface by a lens unit. A synchronous detection optical device for guiding the light to the synchronous detection element and controlling the timing of the scanning start position on the surface to be scanned using a signal from the synchronous detection element. Assuming that δM1 is the focus position shift amount in the main scanning cross section of the light beam guided to the synchronous detection element viewed from the slit, and δX is the focus position shift amount of each image height on the scanned surface.
| ΔX−δM1 | ≦ δYmax / θmax (where, δYmax is an allowable dot displacement amount for each scanning line θmax: the maximum angle difference of the incidence angle of each light beam used for synchronous detection on the slit surface. ) Is characterized by satisfaction.

According to a twenty-third aspect of the present invention, in the twenty-second aspect, the permissible dot displacement for each scanning line is not more than half the resolution in the sub-scanning direction.

According to a twenty-fourth aspect of the present invention, in the twenty-second or twenty-third aspect, the focus position of the light beam guided to the synchronization detecting element in the main scanning section is relatively shifted from the slit by the synchronization detecting optical means. It is characterized in that a correction means for shifting in the optical axis direction is provided.

According to a twenty-fifth aspect of the present invention, in the twenty-second or twenty-third aspect of the present invention, there is provided a correcting means for moving the position of the slit or a unit including the slit in the optical axis direction of the synchronization detecting optical means. Features.

According to a twenty-sixth aspect, in the twenty-second or twenty-third aspect, the lens unit is provided in an optical path between the deflection unit and the slit, and the lens unit is connected to the optical axis of the synchronization detecting optical unit. It is characterized by comprising a correction means for moving in the direction.

A multi-beam scanning optical system according to a twenty-seventh aspect of the present invention includes: an incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from the main scanning direction to a deflecting unit; A scanning optical unit for forming a plurality of scanning lines by forming an image on the surface to be scanned with the plurality of light beams deflected by the deflecting unit, and slitting a part of the plurality of light beams deflected by the deflecting unit by a lens unit After focusing on a surface, the light is guided to a synchronous detection element, and the timing of a scanning start position on the surface to be scanned is controlled for each of the plurality of light fluxes using a signal from the synchronous detection element. In a multi-beam scanning optical system having an optical unit, a shift amount of a focus position in a main scanning section of a light beam guided to the synchronous detection element viewed from the slit is δM1, and each image on the surface to be scanned is High focus position When the shift amount is δX, a correction unit is provided for correcting a dot position shift for each scanning line on the surface to be scanned, which is caused by a difference between the focus position shift amounts δM1 and δX. And

According to a twenty-eighth aspect of the present invention, in the invention of the twenty-seventh aspect, the dot displacement amount is 1 / (1) of the resolution in the sub scanning direction.
2 or less.

A twenty-ninth aspect of the present invention is characterized in that in the invention of the twenty-seventh or twenty-eighth aspect, the plurality of light emitting units are arranged apart from each other in the main scanning direction and the sub-scanning direction.

The invention of claim 30 is characterized in that, in the invention of claim 29, the slit is inclined in the sub-scanning direction in accordance with the amount of dot displacement for each scanning line on the surface to be scanned.

According to a thirty-first aspect of the present invention, the optical axis of the optical means for synchronization detection according to the twenty-ninth aspect of the present invention is configured such that the slit or a unit including the slit is moved in accordance with the amount of dot displacement for each scanning line on the surface to be scanned. It is characterized by comprising rotating means for rotating around.

The multi-beam scanning optical system according to the invention of claim 32, wherein: an incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions disposed apart from the main scanning direction to a deflecting means; Scanning optical means for forming an image of a plurality of light beams deflected by the deflecting means on a surface to be scanned, and a part of the plurality of light beams deflected by the deflecting means being guided to a synchronization detecting element by a lens unit; A synchronous detection optical unit that controls the timing of a scanning start position on the surface to be scanned by using a signal from the synchronous detection element, and a multi-beam scanning optical system including the synchronous detection element as viewed from the light receiving surface of the synchronous detection element. Assuming that δM2 is the focus position shift amount of the light beam guided to the synchronous detection element in the main scanning cross section and δX is the focus position shift amount of each image height on the scanned surface, the following conditional expression is given as | δX. −δM2 | ≦ Ymax / .theta.max (where, [delta] Ymax: permissible dot position shift amount .theta.max for each scan line: maximum angle difference between the incident angle of the light receiving surface of the light beams used to detect synchronization) is characterized by satisfying.

A thirty-third aspect of the present invention is characterized in that, in the thirty-second aspect, the permissible amount of dot displacement for each scanning line is not more than の of the resolution in the sub-scanning direction.

According to a thirty-fourth aspect of the present invention, in the thirty-second or thirty-third aspect, the focus position of the light beam guided to the synchronization detecting element in the main scanning direction is relatively set from the light receiving surface of the synchronization detecting element. It is characterized in that a correcting means for shifting the optical means in the optical axis direction is provided.

In a thirty-fifth aspect of the present invention, in the thirty-second or thirty-third aspect, the correcting means for moving the position of the synchronization detecting element or a unit including the synchronization detecting element in the optical axis direction of the synchronization detecting optical means is provided. It is characterized by having.

According to a thirty-sixth aspect of the present invention, in the thirty-second or thirty-third aspect, the lens portion is provided in an optical path between the deflecting means and the synchronization detecting element. It is characterized by comprising a correction means for moving in the optical axis direction.

An image forming apparatus according to a thirty-seventh aspect of the present invention provides a multi-beam scanning optical system according to any one of the first to thirty-six aspects, a photosensitive member disposed on the surface to be scanned, and the multi-beam scanning optical system. A developing device for developing an electrostatic latent image formed on the photoconductor as a toner image by a light beam scanned by a system, a transfer device for transferring the developed toner image to a material to be transferred, and a transferred toner The image forming apparatus comprises a fixing device for fixing an image to a transfer material.

An image forming apparatus according to a thirty-eighth aspect of the present invention provides a multi-beam scanning optical system according to any one of the first to thirty-sixth aspects, wherein the multi-beam scanning optical system converts code data input from an external device into an image signal and converts the multi-beam scanning optical system into an image signal. The image forming apparatus comprises a printer controller for inputting to a scanning optical system.

The multi-beam scanning optical system according to the thirty-ninth aspect of the present invention comprises: an incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from the main scanning direction to a deflecting unit; A scanning optical unit for forming a plurality of scanning lines by forming an image on the surface to be scanned with the plurality of light beams deflected by the deflecting unit, and slitting a part of the plurality of light beams deflected by the deflecting unit by a lens unit After focusing on a surface, the light is guided to a synchronous detection element, and the timing of a scanning start position on the surface to be scanned is controlled for each of the plurality of light fluxes using a signal from the synchronous detection element. A multi-beam scanning optical system having an optical unit, wherein the light beam guided to the synchronous detection element viewed from the slit has a focus position shift amount δM1 in a main scanning cross section. On the scanning surface Kicking it is characterized in that the dot position deviation amount for each scan line is below half the resolution in the sub-scanning direction.

The multi-beam scanning optical system according to the forty-ninth aspect of the present invention includes: an incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from the main scanning direction to a deflecting unit; Scanning optical means for forming a plurality of scanning lines by forming an image of a plurality of light beams deflected by the deflecting means on a surface to be scanned and part of the plurality of light beams deflected by the deflecting means by a lens unit A multi-beam scanning optical system, comprising: a synchronization detection optical unit that guides light to a detection element and controls timing of a scanning start position on the surface to be scanned for each of the plurality of light fluxes using a signal from the synchronization detection element. System on the surface to be scanned which is caused by having a focus position deviation amount δM2 in a main scanning cross section of a light beam guided to the synchronous detection element as viewed from a light receiving surface of the synchronous detection element. For each scanning line It is characterized in that the dot position shift amount is 1/2 or less of the resolution in the sub-scanning direction.

The multi-beam scanning optical system according to the invention of claim 41, wherein an incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to a deflecting means; A scanning optical unit for forming a plurality of scanning lines by forming an image on the surface to be scanned with the plurality of light beams deflected by the deflecting unit, and slitting a part of the plurality of light beams deflected by the deflecting unit by a lens unit After focusing on a surface, the light is guided to a synchronous detection element, and the timing of a scanning start position on the surface to be scanned is controlled for each of the plurality of light fluxes using a signal from the synchronous detection element. In a multi-beam scanning optical system having an optical unit, a focus position shift amount in a main scanning cross section of a light beam guided to the synchronous detection element as viewed from the slit is δM1, and each image on the surface to be scanned is High focus Assuming that the displacement amount is δX, the dot position displacement amount for each scanning line on the surface to be scanned, which is caused by the difference between the focus position displacement amounts δM1 and δX, is 1/1 of the resolution in the sub-scanning direction. 2 or less.

The multi-beam scanning optical system according to claim 42, wherein: an incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from the main scanning direction to a deflecting unit; Scanning optical means for forming a plurality of scanning lines by forming an image of a plurality of light beams deflected by the deflecting means on a surface to be scanned and part of the plurality of light beams deflected by the deflecting means by a lens unit A multi-beam scanning optical system, comprising: a synchronization detection optical unit that guides light to a detection element and controls timing of a scanning start position on the surface to be scanned for each of the plurality of light fluxes using a signal from the synchronization detection element. In the system, δM2 is a focus position shift amount in a main scanning cross section of a light beam guided to the synchronous detection element as viewed from a light receiving surface of the synchronous detection element, and a focus position shift at each image height on the scanned surface. The amount is δX In this case, it is determined that the dot position shift amount for each scanning line on the scanned surface caused by the difference between the focus position shift amounts δM2 and δX is less than 以下 of the resolution in the sub-scanning direction. Features.

[0077]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 is a main portion in a main scanning direction when a multi-beam scanning optical system according to a first embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). It is sectional drawing (main scanning sectional drawing).

In this specification, the plane formed by the optical axis of the scanning optical means and the light beam deflected by the optical deflector is a main scanning section, and the plane including the optical axis of the scanning optical means and orthogonal to the main scanning section. Is defined as a sub-scan section.

In FIG. 1, reference numeral 1 denotes a light source unit (light source means), which has two light emitting units (light sources) 1a and 1b formed of, for example, semiconductor lasers. Note that three or more light emitting units may be provided. The two light emitting portions 1a and 1b are arranged apart from each other in the main scanning direction and the sub scanning direction as shown in FIG. As shown in FIG. 2, the distance between the light emitting units is longer in the main scanning direction than in the sub scanning direction. This is because the actual distance between the light emitting units is longer than the actually required distance between the light emitting units in the sub-scanning direction.
Is rotated to set the distance between the light emitting units in the sub-scanning direction to a desired value. 3 is an aperture stop,
The light beams emitted from the light emitting units 1a and 1b are shaped into a desired optimum beam shape. Reference numeral 2 denotes a collimator lens, which converts a light beam that has passed through the aperture stop 3 into a substantially parallel light beam. Reference numeral 4 denotes a cylindrical lens having a predetermined refractive power only in the sub-scanning direction. Each element such as the aperture stop 3, the collimator lens 2, and the cylindrical lens 4 constitutes one element of the incident optical means 14.

Reference numeral 5 denotes an optical deflector as a deflecting means, which comprises, for example, a rotating polygon mirror, and is rotated at a constant speed in the direction of arrow A in the figure by a driving means (not shown) such as a motor.
Reference numeral 6 denotes a scanning optical unit having an fθ characteristic.
And has a plurality of optical elements (fθ lenses) 6a and 6b, and forms a plurality of scanning lines by forming a plurality of light beams deflected by an optical deflector into a spot-like image on a surface to be scanned. The scanning optical means 6 has a tilt correction function by making the vicinity of the deflecting surface 5a of the optical deflector 5 and the vicinity of the photosensitive drum surface 7 conjugate in the sub-scan section.

Reference numeral 8 denotes a lens unit for detecting synchronization, which forms a plurality of light beams (BD light beams) for detecting a synchronization signal on a surface of a slit 9 provided in the vicinity of a synchronization detection element 10 to be described later.
Let me. Although the lens unit 8 in the present embodiment is configured integrally with the scanning optical unit 6, it may be provided independently. Reference numeral 12 denotes a folding mirror (hereinafter, referred to as a “BD mirror”), which reflects a plurality of BD light beams for adjusting the timing of a scanning start position on the photosensitive drum surface 7 to a synchronization detection element 10 described later. I have. This BD mirror 12
Is located on the incident optical unit 14 side with respect to the optical axis L of the scanning optical unit 6. 9 is a slit for synchronous detection (hereinafter, a slit)
It is described as "BD slit". ), And is disposed at a position equivalent to the photosensitive drum surface 7 to determine a writing position of an image. Reference numeral 11 denotes an imaging lens (hereinafter, referred to as a “BD lens”) for making the BD mirror 12 and the synchronization detecting element 10 conjugate with each other, and correcting the surface tilt of the BD mirror 12. I have. Reference numeral 10 denotes an optical sensor (hereinafter, referred to as a “BD sensor”) as a synchronization detection element. In the present embodiment, a synchronization signal (BD signal) obtained by detecting an output signal from the BD sensor 10 is used. The timing of the scanning start position of the image recording on the photosensitive drum surface 7 is
The adjustment is made for each D light flux.

The lens unit 8, the BD mirror 12, the BD slit 9, the BD lens 11, the BD sensor 10, and other components constitute one element of a synchronization detecting optical unit (BD optical system).

In the present embodiment, two light beams emitted from the light source unit 1 after being light-modulated in accordance with image information are limited in cross-sectional size by an aperture stop 3 and converted into substantially parallel light beams by a collimator lens 2. , And enters the cylindrical lens 4. The light beam incident on the cylindrical lens 4 is emitted as it is in the main scanning section. Further, within the sub-scan section, the light converges and forms an almost linear image (a linear image elongated in the main scanning direction) on the deflecting surface 5a of the optical deflector 5. And the deflecting surface 5 of the optical deflector 5
The two light beams reflected and deflected at a are formed into a spot-like image on the photosensitive drum surface 7 by the scanning optical means 6, and the light deflector 5 is rotated in the direction of arrow A, so that the light beam deviates on the photosensitive drum surface 7. Optical scanning is performed at a constant speed in the direction of arrow B (main scanning direction). Thus, an image is recorded on the photosensitive drum surface 7 as a recording medium.

At this time, in order to adjust the timing of the scanning start position on the photosensitive drum surface 7 before optically scanning the photosensitive drum surface 7, a part of the two light beams reflected and deflected by the optical deflector 5 is adjusted. After being condensed on the surface of the BD slit 9 via the BD mirror 12 by the lens unit 8, the light is guided to the BD sensor 10 via the BD lens 11. Then, a synchronization signal (BD) obtained by detecting an output signal from the BD sensor 10 is output.
), The timing of the scanning start position of the image recording on the photosensitive drum surface 7 is adjusted for each BD light beam.

At this time, as described above, the BD
If the focus position of the BD light beam on the surface of the slit 9 and the focus position of the light beam for scanning on the surface 7 to be scanned are shifted, the writing start position of the A and B rays is shifted as described above.
There is a problem that the printed image is deteriorated due to a change in the interval between the A and B rays in the main scanning direction during scanning.

Therefore, in this embodiment, each element is set so as to satisfy the following conditional expression (A). That is,
The amount of focus position shift in the main scanning section of the BD light beam guided to the BD sensor 10 as viewed from the BD slit 9 is δM,
The shift amount of the focus position at each image height on the scanned surface 7 is δX
| ΔX−δM | ≦ δYmax / θmax ‥‥‥ (A) (where, δYmax: allowable dot shift amount θmax: BD slit at the time when the BD light flux corresponding to each light emitting unit starts to enter the BD sensor) Is satisfied, the maximum angle difference [rad] of the incident angle of the BD light beam with respect to is satisfied.

As specific numerical values, the resolution in the sub-scanning direction is 1200 dpi, δYmax = 10 μm, θma
Assuming that x = 0.5 [rad], the maximum value of | δX−δM | is 1.15 mm. Thus, in the present embodiment, high-speed and high-quality printing is realized. In this embodiment, the allowable dot shift amount (write start position shift amount between each scanning line) δYmax is set so as to be １ ／ or less of the resolution in the sub-scanning direction.

In the present embodiment, each light beam emitted from the light source unit 1 is converted into a substantially parallel light beam by the collimator lens 2. However, the present invention is not limited to this. For example, the light beam may be converted into a convergent light beam or a divergent light beam. Effects can be obtained.

Next, the reason why the permissible dot displacement amount for each scanning line is preferably equal to or less than の of the resolution in the sub-scanning direction will be described below. If it is assumed that the number of light sources is two and the amount of dot shift is one dot, an image one dot before or after one dot is printed at the original printing position,
Sometimes it is printed at places where it should not be printed, or at other places it should not be printed.
The printed state becomes very difficult to see.

In consideration of the above-mentioned phenomenon, it is desirable that the dot shift amount is 0, but it is very difficult to actually perform the dot shift. Also, 1/2 dot (10 μm at 1200 dpi)
If it is a small amount (less than or equal to), the printed image does not feel difficult to see even if it is actually viewed. Conversely, when a dot shift exceeding 1/2 dot occurs, it becomes gradually recognizable by eyes, depending on the image actually printed, and it cannot be said that the printing state is good.

In the above description, the number of light sources is limited to two in order not to complicate the story much. However, since such a phenomenon occurs irrespective of the number of light sources, the maximum value of the dot shift amount is reduced to 1 /.
Must be 2 dots or less.

Further, in the present embodiment, the time interval from when the light beam A enters the BD sensor 10 and an output signal is generated from the BD sensor 10 to when printing on the photosensitive drum 7 is started, and the time when the B light beam is applied to the BD sensor 10. And the time interval from when an output signal is generated from the BD sensor 10 to when printing on the photosensitive drum 7 is started is assumed to be equal.

[0093] Although the case where two laser beams are used has been described, the number of laser beams may be three or more. Next, an image forming apparatus applied to the present invention will be described.

FIG. 31 is a sectional view of a main portion in the sub-scanning direction showing an embodiment of the image forming apparatus of the present invention. In FIG. 31, reference numeral 104 denotes an image forming apparatus. The image forming apparatus 104 includes an external device 1 such as a personal computer.
17, the code data Dc is input. The code data Dc is converted into image data (dot data) Di by the printer controller 111 in the apparatus. This image data Di is input to the optical scanning unit 100 having the configuration shown in the first embodiment. The optical scanning unit 100 emits a light beam 103 modulated in accordance with the image data Di.
As a result, the photosensitive surface of the photosensitive drum 101 is scanned in the main scanning direction.

The photosensitive drum 101 serving as an electrostatic latent image carrier (photoconductor) is rotated clockwise by a motor 115. Then, along with this rotation, the photosensitive surface of the photosensitive drum 101 moves in the sub-scanning direction orthogonal to the main scanning direction with respect to the light beam 103. Above the photosensitive drum 101, a charging roller 102 for uniformly charging the surface of the photosensitive drum 101 is provided so as to contact the surface.
The surface of the photosensitive drum 101 charged by the charging roller 102 is irradiated with a light beam 103 scanned by the optical scanning unit 100.

As described above, the light beam 103 is
The light is modulated based on the image data Di, and by irradiating the light beam 103, an electrostatic latent image is formed on the surface of the photosensitive drum 101. This electrostatic latent image is further moved from the irradiation position of the light beam 103 to the photosensitive drum 101.
Is developed as a toner image by a developing device 107 disposed so as to contact the photosensitive drum 101 on the downstream side in the rotation direction of the photosensitive drum 101.

The toner image developed by the developing unit 107 is transferred below the photosensitive drum 101 onto a sheet 112 as a material to be transferred by a transfer roller 108 disposed so as to face the photosensitive drum 101. The paper 112 is stored in a paper cassette 109 in front of the photosensitive drum 101 (the right side in FIG. 31), but can be fed manually. At the end of the paper cassette 109, the paper feed roller 1
10 are provided, and the paper 1 in the paper cassette 109 is provided.
12 to the transport path.

The sheet 112 onto which the unfixed toner image has been transferred as described above is further moved to the rear of the photosensitive drum 101 (FIG. 3).
1 is conveyed to the fixing device (left side). The fixing device has a fixing roller 113 having a fixing heater (not shown) therein.
And a pressure roller 114 disposed so as to be in pressure contact with the fixing roller 113. The paper 112 conveyed from the transfer unit is fixed to the fixing roller 113 and the pressure roller 1.
The unfixed toner image on the paper 112 is fixed by heating while applying pressure at the pressure contact portion 14. Further, a paper discharge roller 116 is disposed behind the fixing roller 113, and discharges the fixed paper 112 to the outside of the image forming apparatus.

Although not shown in FIG. 31, the print controller 111 not only converts the explanation data first, but also the motor 115 and other components in the image forming apparatus,
It controls a polygon motor and the like in the optical scanning unit described later.

[Embodiment 2] FIG. 3 shows Embodiment 2 of the present invention.
FIG. 2 is a cross-sectional view (main scanning cross-sectional view) of a main part in the main scanning direction when the multi-beam scanning optical system is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

The present embodiment is different from the first embodiment in that the focus position of the BD light beam guided to the BD sensor 10 in the main scanning section is relatively shifted from the BD slit 9 to the optical axis of the BD optical system. That is, the conditional expression (A) was satisfied by being shifted in the direction. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.

That is, when the degree of curvature of field of the scanning optical means 6 is considerably stable for each product and the BD slit 9 is arranged at the focus position, the difference value | δX−δM | of the conditional expression (A) cannot be ignored. In such a case, as shown in FIG. 3, the BD slit 9 is shifted from the focus position in the optical axis direction of the BD optical system from the focus position by the adjusting means (FIG. 30) from the beginning to satisfy the conditional expression (A). I have. This realizes high-speed and high-quality printing.

Next, a description will be given of the dot shift adjusting means applied to the present invention.

The BD slit 9 can be moved and adjusted in the optical axis direction of the BD lens 11 by adjusting means 220 constituting the multi-beam scanning optical system of the present invention. That is, FIG.
As shown in the figure, the BD slit 9 is fixed to the support 221 by bonding or the like. The support 221 is a guide 222
And is movable in the optical axis direction. The holder 223 is fixed in the image forming apparatus.

The guide 222 is fixed to a “U-shaped” holder 223 fixed to a stationary member of the apparatus. A compressible spring 22 is provided between the holder 223 and the support 221.
4 acts on the support 221 to exert an elastic force toward the left in the figure. Adjusting screw 2 screwed on holder 223
Reference numeral 25 indicates that the tip of the support abuts on the adjusting means 220 from the right side to stop the movement of the support by the elastic force of the spring 224. Therefore, when the adjusting screw 225 is sent, the support 221 is moved to the right side of the drawing, and when the adjusting screw 225 is loosened, the support 221 is sent.
Can be displaced to the left, and the position of the BD slit 9 is adjusted in the optical axis direction so as to satisfy the conditional expression (A) based on the measured write start position shift amount δY of the A and B rays on the scanned surface. Adjust the movement at.

[Embodiment 3] FIG. 4 shows Embodiment 3 of the present invention.
FIG. 2 is a cross-sectional view (main scanning cross-sectional view) of a main part in the main scanning direction when the multi-beam scanning optical system is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

This embodiment is different from the first embodiment in that the unit 13 including the BD slit 9 is moved in the direction of the optical axis of the BD optical system to satisfy the conditional expression (A), The rotation direction of the container is rotated in the opposite direction (the direction of arrow C in the figure). Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.

That is, in this embodiment, the optical deflector 5 is rotated at a constant speed in a direction indicated by an arrow C in a direction opposite to the rotation direction of the first embodiment by driving means (not shown) such as a motor. This is a measure to prevent the synchronization detecting optical unit (BD optical system) from being arranged between the scanning optical unit 6 and the incident optical unit 14 due to a space problem.

At this time, similarly to the first embodiment, the position of the focus of each BD light beam on the BD slit 9 surface and the scanning surface 7
If the focus position of the light beam for scanning is shifted, the writing start position of the A and B rays is shifted as described above, or the interval between the A and B rays during scanning is changed in the main scanning direction. There is a problem that the image is deteriorated.

In particular, in the present embodiment, in order to achieve high image quality, δY max = 6 μm and θmax = 0.5 [rad]
], The difference value | δX−δ of the conditional expression (A) is obtained.
M | must be set to 0.69 mm or less, and it is very difficult to stably configure a multi-beam scanning optical system having such optical performance without adjustment.

Therefore, in this embodiment, the adjusting means (FIG. 30)
By moving the unit 13 including the BD slit 9 in the optical axis direction of the BD optical system as shown by the arrow D in FIG. 4, the focusing state of the BD light beam on the surface of the BD slit 9 in the main scanning section is adjusted. Then, for example, the state shown in FIG. 17B is improved to the state shown in FIG. 18B. This satisfies the above specification, that is, the conditional expression (A), and realizes high-speed, high-quality printing.

[Embodiment 4] FIG. 5 shows Embodiment 4 of the present invention.
FIG. 2 is a cross-sectional view (main scanning cross-sectional view) of a main part in the main scanning direction when the multi-beam scanning optical system is applied to an image forming apparatus such as a laser beam printer (LBP). 4, the same elements as those shown in FIG. 4 are denoted by the same reference numerals.

The present embodiment is different from the third embodiment in that the BD slit 9 and the unit 13 including the BD slit 9 are fixed, and the first and second optical elements (fθ lens) constituting the scanning optical means 6 are fixed. In order to shorten the shape of 6a and 6b in the main scanning direction, the lens unit 8 is provided independently without being integrated with the scanning optical unit 6, and the lens unit 8 is moved in the optical axis direction of the BD optical system. That is, conditional expression (A) was satisfied. Other configurations and optical functions are substantially the same as those of the third embodiment, and thus, similar effects are obtained.

That is, in this embodiment, the BD slit 9 and the unit 13 including the BD slit 9 are fixed.
The lens unit 8 having a single lens is formed separately from the scanning optical unit 6 without being integrated. At this time, the first embodiment
Similarly to the above, if the focus position of each BD light beam on the surface of the BD slit 9 is shifted from the focus position of the scanning light beam on the surface to be scanned 7, the writing start positions of the A and B rays are shifted as described above. In this embodiment, there is a problem that the interval between the light beams A and B during scanning in the main scanning direction is changed, thereby deteriorating the printed image.
By moving the lens unit 8 in the direction of the optical axis of the BD optical system as shown by the arrow F in the figure, the focusing state of the BD light beam in the main scanning section on the surface of the BD slit 9 is adjusted. Satisfies the conditional expression (A), thereby realizing high-quality printing.

In this embodiment, the scanning optical means 6
If the degree of curvature of field is considerably stable for each product and the difference value | δX−δM | of the conditional expression (A) has a nonnegligible value when the BD slit 9 is disposed at the focus position, the lens unit 8 is set in advance. May be changed on the optical axis to change the focus position in the main scanning section, thereby satisfying conditional expression (A).

[Embodiment 5] FIG. 6 shows Embodiment 5 of the present invention.
FIG. 2 is a cross-sectional view (main scanning cross-sectional view) of a main part in the main scanning direction when the multi-beam scanning optical system is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

In the present embodiment, the focus position deviation amount δM in the main scanning section of the BD light beam guided to the BD sensor 10 as viewed from the BD slit 9 and the focus position of each image height on the surface 7 to be scanned The dot adjustment generated as a result of the difference between the shift amount δX and the focus position shift amounts δM and δX being different from each other is corrected by an angle adjustment unit 1 as a correction unit shown in FIG.
5, the rotation is adjusted by rotating the BD slit 9 or the unit 16 including the BD slit 9 around the optical axis of the BD optical system.

That is, the light source unit 1 in the present embodiment
As shown in FIG. 2, the light-emitting portions 1a and 1b are arranged apart from each other also in the sub-scanning direction, and the positions where light beams pass in the sub-scanning direction correspond to the light-emitting portions 1a and 1b. Different for B light.

In the present embodiment, the BD slit 9 is rotated by the angle adjusting means 15 as shown in FIGS. 8A and 8B and FIGS. The timing at which the B ray starts to enter the BD sensor 10 is changed. FIG. 8 is an explanatory view showing the inclination of the BD slit 9 and the printing position of each light beam (before adjustment), and FIG.
FIG. 4 is an explanatory diagram showing the inclination of a D slit and the printing position (after adjustment) of each light beam.

As described above, in the present embodiment, the BD
The focus position shift amounts δM and δX of the respective focus position shift amounts δM in the main scanning cross-section of each BD light beam guided to the sensor 10 and the focus position shift amounts δX of the respective image heights on the scanned surface 7. Due to the difference, the dot deviation that would otherwise occur is corrected (canceled) by rotating and adjusting the BD slit 9 using the angle adjusting means 15. This realizes high-speed and high-quality printing.

In this embodiment, the optical function of forming an image using the multi-beam scanning optical system is substantially the same as that of the first embodiment.

[Embodiment 6] FIG. 10 is a cross-sectional view (main part) in the main scanning direction when the multi-beam scanning optical system according to Embodiment 6 of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). FIG. 11 is a cross-sectional view of FIG.
FIG. 3 is a perspective view of a main part of a D slit 9. 10 and 11, the same elements as those shown in FIG. 6 are denoted by the same reference numerals.

The present embodiment is different from the above-described fifth embodiment in that it has no angle adjusting means, and the BD slit 9 or the unit 16 including the BD slit 9 is inclined in the sub-scanning direction from the beginning to reduce the dot deviation. This is the correction (cancellation). Other configurations and optical functions are substantially the same as those of the fifth embodiment, and thus, similar effects are obtained.

That is, if the degree of curvature of field of the scanning optical means 6 is considerably stable for each product, and the BD slit 9 is arranged at the focus position, the difference value | δX−δM | of the conditional expression (A) cannot be ignored. 10 and 11
As shown in (1), the dot shift is corrected (canceled) by inclining the BD slit 9 in the sub-scanning direction from the beginning. This realizes high-speed and high-quality printing.

[Embodiments 7, 8, 9, and 10] FIGS. 12, 13, 14, and 15 show Embodiment 7 of the present invention,
FIG. 9 is a cross-sectional view (main scanning cross-sectional view) of a main part in the main scanning direction when the 8, 9, and 10 multi-beam scanning optical systems are applied to an image forming apparatus such as a laser beam printer (LBP). In FIGS. 12, 13, 14, and 15, the same elements as those shown in FIGS. 1, 3, 4, and 5 are denoted by the same reference numerals.

The seventh embodiment corresponds to the first embodiment, the eighth embodiment corresponds to the second embodiment, the ninth embodiment corresponds to the third embodiment, and the tenth embodiment corresponds to the first embodiment. 4 corresponding to Embodiments 7, 8, 9, 1
0 is different from the first, second, third and fourth embodiments in that the BD slit 9 and the BD lens 11 are not used in order to simplify the entire apparatus and reduce the cost. Other configurations and optical functions are substantially the same as those of the corresponding embodiments 1, 2, 3, and 4, whereby similar effects are obtained.

That is, in each of the seventh, eighth, ninth and tenth embodiments, the effective end of the BD sensor 10 has a function corresponding to the BD slit 9 in the corresponding one of the first, second, third and fourth embodiments. Therefore, in each of the embodiments 7, 8, 9, and 10, the contents performed in the corresponding embodiments 1, 2, 3, and 4 are
This is implemented by replacing the surface of the D slit 9 with the light receiving surface of the BD sensor 10. As a result, the same effect as that of the corresponding embodiment is obtained.

As described above, in each of the seventh, eighth, ninth, and tenth embodiments, by using a structure without using a BD slit and a BD lens, a relatively simple structure can be achieved while simplifying the entire apparatus and reducing the cost. High-speed, high-quality printing is realized.

[Embodiment 11] FIG. 11 is a sectional view (main part) in the main scanning direction when a multi-beam scanning optical system according to Embodiment 11 of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). FIG.

At this time, as described above, when the focus position of each BD light beam is shifted and is not on the surface of the BD slit 9 due to an assembling error or a focus error of the lens, especially in this embodiment, as shown in FIG. Each light emitting part 1a, 1b
Are also separated in the main scanning direction, the timing at which the principal ray of each BD light flux grazes the edge of the BD slit 9 is different from before the defocusing, and the writing position of the image to each of the light emitting units 1a and 1b is shifted. I will.

Therefore, in the present embodiment, the following conditional expression (B) is satisfied: | δM | ≦ δYmax / tan (θmax) (B) (where, δM: the BD light flux used for synchronous detection from the BD slit surface) Distance in the optical axis direction of the BD optical system up to the converging point in the main scanning section δYmax: Allowable write start position shift amount (dot shift amount) between each scanning line θmax: BD of each BD light beam used for synchronization detection Each element is configured so as to satisfy the maximum angle difference of the incident angle to the slit surface.

As a concrete numerical value, δYmax = 11μ
m, θmax = 0.5 °, | δM | = δMmax =
1.26 mm. Thus, in the present embodiment, high-speed and high-quality printing is realized.

In this embodiment, the permissible dot shift amount δYmax is set so as to be １ ／ or less of the resolution in the sub-scanning direction.

In this embodiment, each light beam emitted from the light source unit 1 is converted into a substantially parallel light beam by the collimator lens 2. However, the present invention is not limited to this. For example, the light beam may be converted into a convergent light beam or a divergent light beam. Similar effects can be obtained.

[Twelfth Embodiment] FIG. 23 is a cross-sectional view (main part) in the main scanning direction when a multi-beam scanning optical system according to a twelfth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). FIG. In the figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

In the present embodiment, the optical deflector 5 is rotated at a constant speed by a driving means (not shown) such as a motor in a direction indicated by an arrow C in a direction opposite to the rotation direction of the first embodiment. This is a measure to prevent the synchronization detecting optical unit (BD optical system) from being arranged between the scanning optical unit 6 and the incident optical unit 14 due to a space problem.

At this time, as described in the eleventh embodiment, when the focus position of each BD light beam is shifted and is not on the surface of the BD slit 9, especially in this embodiment, the light emitting portions 1a and 1b as shown in FIG. Are also separated in the main scanning direction, the timing at which the principal ray of each BD light flux grazes the edge of the BD slit 9 is different from before the defocusing, and the writing position of the image to each of the light emitting units 1a and 1b is shifted. I will. In the present embodiment, further improvement in image quality is required, and therefore, the above-described writing start position shift becomes a problem.

Therefore, in this embodiment, the BD slit 9 is moved in the optical axis direction of the BD optical system as shown by an arrow D in FIG. By adjusting the light condensing state of the light beam in the main scanning section and thereby improving the state shown in FIG. 29B to the state shown in FIG. 29C, high-speed and high-quality printing can be realized. I have.

Further, in the present embodiment, each element is set so as to satisfy the above-mentioned conditional expression (B), and the specific numerical values are given as δYmax = 7 μm, θmax = 0.5 ° and | δM | = δMmax = 0.80 mm.

In this embodiment, the optical function of forming an image using a multi-beam scanning optical system is substantially the same as that of the eleventh embodiment.

Next, a description will be given of the dot shift adjusting means applied to the present invention.

The movement of the BD slit 9 in the direction of the optical axis of the BD lens 11 can be adjusted by the adjusting means 220 constituting the multi-beam scanning optical system of the present invention. That is, FIG.
As shown in the figure, the BD slit 9 is fixed to the support 221 by bonding or the like. The support 221 is a guide 222
And is movable in the optical axis direction. The holder 223 is fixed in the image forming apparatus.

The guide 222 is fixed to a "U-shaped" holder 223 fixed to a stationary member of the apparatus. A compressible spring 22 is provided between the holder 223 and the support 221.
4 acts on the support 221 to exert an elastic force toward the left in the figure. Adjusting screw 2 screwed on holder 223
Reference numeral 25 indicates that the tip of the support abuts on the adjusting means 220 from the right side to stop the movement of the support by the elastic force of the spring 224. Therefore, when the adjusting screw 225 is sent, the support 221 is moved to the right side of the drawing, and when the adjusting screw 225 is loosened, the support 221 is sent.
Can be displaced to the left, and the position of the BD slit 9 is adjusted in the optical axis direction so as to satisfy the conditional expression (B) based on the measured write start position shift amount δY of the A and B rays on the scanned surface. Adjust the movement at.

[Thirteenth Embodiment] FIG. 24 is a cross-sectional view (main part) in the main scanning direction when a multi-beam scanning optical system according to a thirteenth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). FIG. In the figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

The present embodiment is different from the above-described twelfth embodiment in that the BD slit 9, an optical element (BD lens) 11 disposed between the BD slit 9 and the BD sensor 10,
Then, the BD sensor 10 is held by the same holding member 13, and the holding member 13 is moved in the optical axis direction of the BD optical system by the adjusting means, so that the main scanning section of each BD light beam on the surface of the BD slit 9 is provided. That is, it is possible to adjust the state of condensing light. Other configurations and optical functions are substantially the same as those of the twelfth embodiment, and the same effects are obtained.

That is, in the present embodiment, the eleventh embodiment is described.
However, as described above, the BD lens 11 is disposed behind the BD slit 9, and has a conjugate relationship between the vicinity of the reflection surface of the BD mirror 12 and the vicinity of the BD sensor 10, thereby performing a tilt correction function. However, in order to obtain the above-described tilt correction function, it is particularly important to accurately obtain the distance between the BD lens 11 and the BD sensor 10. This is because the distance between the BD mirror 12 and the BD lens 11 is S, BD
Assuming that the distance between the lens 11 and the BD sensor 10 is T, B
The distance K from the D mirror 12 to the BD sensor 10 is K =
S + T.

On the other hand, B on the surface of the BD slit 9
The BD lens 11 is adjusted to the BD
If the holding member 13 is moved toward the sensor 10 by δS, the distance K ′ from the BD mirror 12 to the BD sensor 10 is K ′ = S + T + (1−f ² / (S−f) ² ) * δS. Here, f is the focal length of the BD lens 11.

In general, since the focal length f of the BD lens 11 is very small with respect to the distance S between the BD mirror 12 and the BD lens 11, the distance K 'is K' ≒ S + T + δS, and the distance T between the BD lens 11 and the BD sensor 10 is T.
Will hardly change. Therefore, in order to obtain the tilt correction function, it is necessary to always keep the original distance. Also, if the position of the BD slit 9 itself is shifted and the writing start position of the scanning line is shifted, the phenomenon described above occurs, which is not good. Moreover, since the distance from the BD slit 9 to the BD sensor 10 is practically negligible, the BD slit 9, the BD lens 11, and the BD
It is advantageous to incorporate the sensor 10 into the same one holding member 13 in order to obtain the positional accuracy.

Therefore, in the present embodiment, as described above, the BD slit 9, the BD lens 11, and the BD sensor 10 are held by the same holding member 13, and the holding member 13 is adjusted by an adjusting means (not shown) as shown in FIG. By moving in the optical axis direction of the BD optical system as shown at E, the focusing state of each BD light beam on the surface of the BD slit 9 in the main scanning section is adjusted. This realizes high-speed and high-quality printing.

[Embodiment 14] FIG. 25 is a cross-sectional view (main part) in a main scanning direction when a multi-beam scanning optical system according to Embodiment 14 of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). FIG. In this figure, the same elements as those shown in FIG. 23 are denoted by the same reference numerals.

The present embodiment differs from the twelfth embodiment in that the lens unit 8 is provided independently without being integrated with the scanning optical means 6 and that the BD slit 9 is fixed and the lens unit 8 is By moving the BD optical system in the optical axis direction of the BD optical system by the adjusting means, the focusing state of each BD light beam on the surface of the BD slit 9 in the main scanning section can be adjusted. Other configurations and optical functions are substantially the same as those of the twelfth embodiment, and the same effects are obtained.

That is, in the present embodiment, the lens unit 8 having a single lens is arranged separately from the scanning optical unit 6 without being integrated with the scanning optical unit 6, and the lens unit 8 is adjusted by the adjusting unit (FIG. 30). By moving in the optical axis direction of the BD optical system as indicated by arrow F shown in FIG.
The focusing state of the D light beam in the main scanning section is adjusted. Thereby, the state shown in FIG. 29B is improved to the state shown in FIG.

[Embodiment 15] FIG. 26 is a cross-sectional view (main part) in the main scanning direction when the multi-beam scanning optical system according to Embodiment 15 of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). FIG. In this figure, the same elements as those shown in FIG. 23 are denoted by the same reference numerals.

The present embodiment is different from the twelfth embodiment in that at least a part of the lens constituting the lens unit 8 is integrated with the scanning optical unit 6 and the lens unit not integrated with the scanning optical unit 6. By moving at least a part of the lens 8a and the BD slit 9 in the direction of the optical axis of the BD optical system by the adjusting means, each BD light beam on the surface of the BD slit 9 is condensed in the main scanning section. That is, the state can be adjusted. Other configurations and optical functions are substantially the same as those of the twelfth embodiment, and the same effects are obtained.

That is, in this embodiment, at least a part of the lens constituting the lens unit 8 is integrated with the scanning optical unit 6, and a part of the lens 8a of the lens unit 8 which is not integrated with the scanning optical unit 6. And the BD slit 9 is moved in the optical axis direction of the BD optical system by the adjusting means (FIG. 30) to adjust the light condensing state of each BD light beam on the surface of the BD slit 9 in the main scanning section. I have. Thereby, the state shown in FIG. 29B is improved to the state shown in FIG.

In this embodiment, the lens 8 of the lens unit 8 is used.
Although both the “a” and the BD slit 9 are moved, the present invention can be applied in the same manner as in the above-described fifth embodiment with only one of them.

[Embodiment 16] FIG. 27 is a cross-sectional view (main part) in the main scanning direction when the multi-beam scanning optical system according to Embodiment 16 of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). FIG. In this figure, the same elements as those shown in FIG. 23 are denoted by the same reference numerals.

This embodiment differs from the twelfth embodiment in that at least a part of the optical element (fθ lens) of the scanning optical means 6 integrated with the lens unit 8 is adjusted by the adjusting means to adjust the light of the scanning optical means 6. Axial movement and BD
By moving the slit 9 in the direction of the optical axis of the BD optical system, the focusing state of each BD light beam on the surface of the BD slit 9 in the main scanning section can be adjusted. Other configurations and optical functions are substantially the same as those of the twelfth embodiment.
Thereby, a similar effect is obtained.

That is, in this embodiment, the first optical element (fθ lens) 6a constituting the scanning optical means 6 is adjusted by the adjusting means (FIG. 30) within a range where the shape of the spot on the surface 7 to be scanned does not change much. The BD slit 9 is moved in the direction of arrow G (the optical axis direction of the scanning optical means 6) in the figure, and the BD slit 9 is moved in the direction of arrow D in the figure.
By moving in the direction (the optical axis direction of the BD optical system), the focusing state of each BD light beam on the surface of the BD slit 9 in the main scanning section is adjusted. As a result, FIG.
The state shown in FIG. 29B is improved to the state shown in FIG.

In this embodiment, the first optical element 6a is moved, but the second optical element (fθ lens) 6b may be moved, or the first and second optical elements 6a and 6a may be moved.
6b may be moved.

In the present embodiment, both the first optical element 6a and the BD slit 9 are moved. However, the present invention can be applied to only one of them, similarly to the sixth embodiment.

[Embodiment 17] FIG. 28 is a sectional view (main part) in the main scanning direction when the multi-beam scanning optical system according to Embodiment 17 of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). FIG. In the figure, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

The present embodiment differs from the twelfth embodiment in that the BD slit 9 is fixed and at least a part of the optical element (fθ lens) constituting the scanning optical unit 6 integrated with the lens unit 8 is mainly used. By moving in the scanning direction, the focusing state of each BD light beam on the BD slit 9 surface in the main scanning section can be adjusted, and the rotation direction of the optical deflector is changed in the opposite direction (arrow A in the figure). Direction). Other configurations and optical functions are substantially the same as those of the twelfth embodiment, and the same effects are obtained.

That is, in this embodiment, the BD slit 9 is fixed, and among the plurality of lenses constituting the scanning optical means 6 integrally formed with the lens section 8, local curvature in the main scanning direction, particularly, at the periphery. Is moved in the main scanning direction by the adjusting means (FIG. 30) within the range in which the shape of the spot on the scanned surface 7 does not change so much as shown by the arrow H in the figure. Thus, the longitudinal magnification of each BD light beam in the main scanning direction is changed, and the focusing state of each BD light beam on the BD slit 9 surface in the main scanning cross section is adjusted. Thereby, the state shown in FIG. 29B is improved to the state shown in FIG.

In the present embodiment, the first optical element 6a is moved in the main scanning direction, but the second optical element (fθ lens) 6b may be moved, or the first and second optical elements may be moved. Both the elements 6a and 6b may be moved.

[Embodiment 18] In this embodiment 18, scanning is caused by having a focus position shift amount δX in the main scanning cross section of the BD light beam guided to the BD sensor 10 viewed from the BD slit 9. Dot shift on the surface
The angle adjusting means 15 as a correcting means shown in FIG.
The correction is performed by rotating and adjusting the BD slit 9 or the unit 16 including the BD slit 9 around the optical axis of the BD optical system.

That is, the light source unit 1 in the present embodiment
As shown in FIG. 2, the light-emitting portions 1a and 1b are arranged apart from each other also in the sub-scanning direction, and the positions where light beams pass in the sub-scanning direction correspond to the light-emitting portions 1a and 1b. Different for B light.

In this embodiment, the BD slit 9 is rotated by the angle adjusting means 15 as shown in FIGS. 8A and 8B and FIGS. The timing at which the B ray starts to enter the BD sensor 10 is changed. FIG. 8 is an explanatory view showing the inclination of the BD slit 9 and the printing position of each light beam (before adjustment), and FIG.
FIG. 4 is an explanatory diagram showing the inclination of a D slit and the printing position (after adjustment) of each light beam.

As described above, in the present embodiment, the BD
Due to the amount of shift δX of the focus position of each BD light beam guided to the sensor 10 in the main scanning section, the dot shift on the surface to be scanned, which would otherwise occur, can be corrected using the angle adjusting means 15. Correction (cancellation) is made by adjusting the rotation of No. 9. This realizes high-speed and high-quality printing.

In this embodiment, the optical function of forming an image using the multi-beam scanning optical system is substantially the same as that of the eleventh embodiment.

[Embodiment 19] FIG. 10 is a sectional view (main part) in a main scanning direction when a multi-beam scanning optical system according to Embodiment 19 of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). FIG. 11 is FIG. 10.
3 is a perspective view of a main part of a BD slit 9 of FIG. 10 and 11
In FIG. 7, the same elements as those shown in FIG. 6 are denoted by the same reference numerals.

In this embodiment, the eighteenth embodiment is described.
The difference from this is that the dot shift on the surface to be scanned is corrected (canceled) by tilting the BD slit 9 or the unit 16 including the BD slit 9 in the sub-scanning direction from the beginning without having the angle adjusting means. . Other configurations and optical functions are substantially the same as those of the eighteenth embodiment, and the same effects are obtained.

That is, the degree of curvature of field of the scanning optical means 6 is considerably stable for each product, and when the BD slit 9 is arranged at the focus position, the difference value | δX | of the conditional expression (B) has a value that cannot be ignored. In such a case, as shown in FIGS. 10 and 11, the BD slit 9 is inclined in the sub-scanning direction from the beginning to correct (cancel) dot deviation on the scanned surface. This realizes high-speed and high-quality printing.

[Embodiments 20, 21, 22, 23, 2]
4, 25, 26] Embodiment 20, 21, 22, 2
3, 24, 25, and 26 correspond to the embodiments 11, 12, 1 respectively.
3, 14, 15, 16, and 17, and in the respective embodiments 20, 21, 22, 23, 24, 25, and 26, the aforementioned embodiments 11, 12, 13, 14, 15, and
The difference in common with the devices 16 and 17 is that the device is configured without using the BD slit 9 and the BD lens 11 in order to simplify the entire device and reduce the cost. Other configurations and optical functions are the same as those of the corresponding embodiments 11, 12, 13, 1.
4, 15, 16 and 17 are substantially the same, thereby obtaining similar effects.

That is, the embodiments 20, 21, 22, 2
In 3, 24, 25, and 26, the effective end of the BD sensor 10 corresponds to the corresponding embodiments 11, 12, 13, 1 described above.
It functions equivalent to the BD slit 9 in 4,15,16,17. Therefore, the embodiments 20, 21, 22, 2
In Embodiments 3, 24, 25, and 26, corresponding Embodiments 1
The contents performed in 1, 12, 13, 14, 15, 16, 17 are implemented by replacing the surface of the BD slit 9 with the light receiving surface of the BD sensor 10. As a result, the same effect as that of the corresponding embodiment is obtained.

As described above, the embodiments 20, 21, 22, 22
23, 24, 25, 26 BD slit and B
By configuring without using a D lens, high-speed and high-quality printing is realized by a relatively simple configuration while simplifying the entire apparatus and reducing the cost.

[0177]

According to the present invention, as described above, in the main scanning cross section of the light beam guided to the synchronous detection element viewed from the BD slit (if the BD slit is not provided, the light receiving surface of the synchronous detection element). Where δM is the focus shift amount of the image and δX is the focus shift amount of each image height on the surface to be scanned, each element is set so that the focus shift amount δX satisfies the conditional expression (A). Accordingly, it is possible to achieve a multi-beam scanning optical system capable of realizing high-speed printing at high speed with a relatively simple configuration, and an image forming apparatus using the same.

Further, according to the present invention, as described above, the focus position deviation amount δM in the main scanning section of the light beam guided to the synchronous detection element as viewed from the BD slit and the image height of each image height on the surface 7 to be scanned. By correcting the dot shift caused by the difference between the focus shift amount δX and the focus shift amounts δM and δX by the correcting means, high-quality printing can be realized at high speed with a relatively simple configuration. And a multi-beam scanning optical system and an image forming apparatus using the same.

According to the present invention, as described above, the incident optical means for making the plurality of light beams emitted from the light source means having a plurality of light emitting portions incident on the deflecting means, and the plurality of light beams deflected by the deflecting means are scanned onto the surface to be scanned. After forming an image on the scanning optical means for forming a plurality of scanning lines, a part of the plurality of light beams deflected by the deflecting means after condensing on a slit surface via a return mirror by a lens unit, A multi-beam scanning optical system comprising: a synchronization detection optical unit that guides light to a synchronization detection element and controls a timing of a scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detection element. In the system, by setting each element so as to satisfy the conditional expression (B), or by allowing the adjusting means to adjust the focusing state of a plurality of light beams in the main scanning section on the slit surface, ratio It is possible to achieve an image forming apparatus using the multi-beam scanning optical system and it is possible to realize high-quality printing at high speed by the manner simple configuration.

[Brief description of the drawings]

FIG. 1 is a main scanning sectional view of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of each light emitting unit.

FIG. 3 is a main scanning cross-sectional view according to a second embodiment of the present invention.

FIG. 4 is a main scanning sectional view according to a third embodiment of the present invention.

FIG. 5 is a main scanning cross-sectional view according to a fourth embodiment of the present invention.

FIG. 6 is a main scanning cross-sectional view according to a fifth embodiment of the present invention.

FIG. 7 shows an angle adjusting unit according to a fifth embodiment of the present invention.

FIG. 8 is an explanatory diagram showing the inclination of a slit and the printing position (before adjustment) of each light ray according to a fifth embodiment of the present invention.

FIG. 9 is an explanatory diagram showing the inclination of the slit and the printing position (after adjustment) of each light ray according to the fifth embodiment of the present invention.

FIG. 10 is a main scanning cross-sectional view according to a sixth embodiment of the present invention.

FIG. 11 is a perspective view of a main part of a slit according to a sixth embodiment of the present invention.

FIG. 12 is a main scanning cross-sectional view according to a seventh embodiment of the present invention.

FIG. 13 is a main scanning sectional view of Embodiment 8 of the present invention.

FIG. 14 is a main scanning sectional view of a ninth embodiment of the present invention.

FIG. 15 is a main scanning sectional view according to a tenth embodiment of the present invention.

FIG. 16 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted toward the near side (deflecting means);

FIG. 17 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted toward the near side (deflecting means);

FIG. 18 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted toward the near side (deflecting means);

FIG. 19 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted to the back (anti-deflection means) side.

FIG. 20 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted to the back (anti-deflection means) side.

FIG. 21 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted to the back (anti-deflection means) side.

FIG. 22 is a main scanning cross-sectional view of a conventional multi-beam scanning optical system.

FIG. 23 is a main scanning sectional view according to a twelfth embodiment of the present invention.

FIG. 24 is a main scanning cross-sectional view according to Embodiment 13 of the present invention.

FIG. 25 is a main scanning cross-sectional view of a fourteenth embodiment of the present invention.

FIG. 26 is a main scanning cross-sectional view according to Embodiment 15 of the present invention.

FIG. 27 is a main scanning cross-sectional view of a sixteenth embodiment of the present invention.

FIG. 28 is a main scanning cross-sectional view of a seventeenth embodiment of the present invention.

FIG. 29 is an explanatory diagram showing a relationship between defocus and each principal ray.

FIG. 30 is an explanatory view of an adjusting means according to the present invention.

FIG. 31 is a schematic diagram of an image forming apparatus of the present invention.

[Explanation of symbols]

 1a, 1b light emitting section (semiconductor laser) 1 light source unit 2 collimator lens 3 aperture stop 4 cylindrical lens 5 deflecting means (optical deflector) 5a deflecting surface 6 scanning optical means 6a first optical element 6b second optical element 7 Surface to be scanned (photosensitive drum surface) 8 Lens unit 9 Slit 10 Synchronous detection element 11 Imaging lens 12 Folding mirror 13 Unit 14 Incident optical means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 13/18 B41J 3/00 D H04N 1/113 H04N 1/04 104A

Claims (42)

[Claims] An incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from a main scanning direction to a deflecting unit; and a plurality of light beams deflected by the deflecting unit. Focusing the light beam on the surface to be scanned, scanning optical means for forming a plurality of scanning lines, and after condensing a part of the plurality of light beams deflected by the deflecting means on the slit surface by the lens unit, A synchronous detection optical unit for guiding light to a synchronous detection element and controlling the timing of a scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronous detection element. In the optical system, the following conditional expression is satisfied: | δM1 | ≦ δYmax / tan (θmax) (where, δM1 is the focus position of the light beam guided to the synchronous detection element as viewed from the slit in the main scanning section. Deviation amount δYmax: allowable Dot position shift amount for each scan line that can .theta.max: maximum angle difference between the incident angle to the slit surface of the light beams used to detect synchronization) multi-beam scanning optical system, characterized by satisfying. 2. The multi-beam scanning optical system according to claim 1, wherein the permissible dot position shift amount for each scanning line is equal to or less than の of the resolution in the sub-scanning direction. 3. A synchronizing device according to claim 1, further comprising a correcting unit for shifting a focus position of a light beam guided to the synchronization detecting element in a main scanning section in the optical axis direction of the synchronization detecting optical unit from the slit. The multi-beam scanning optical system according to claim 1 or 2, wherein: 4. The multi-beam according to claim 1, further comprising a correction unit that moves a position of the slit or a unit including the slit with respect to an optical axis direction of the synchronization detection optical unit. Scanning optical system. 5. The apparatus according to claim 1, wherein the lens unit is provided in an optical path between the deflecting unit and the slit, and includes a correcting unit for moving the lens unit in the optical axis direction of the synchronization detecting optical unit. 3. The multi-beam scanning optical system according to claim 1, wherein: 6. At least a part of the lens constituting the lens unit is integrated with the scanning optical unit, and at least a part of the lens unit not integrated with the scanning optical unit and the slit are formed. 3. The multi-beam scanning optical system according to claim 1, further comprising a correction unit that moves the synchronization detection optical unit in an optical axis direction. 7. The scanning optical unit is integrated with the lens unit, at least a part of the optical element of the scanning optical unit is moved in the optical axis direction of the scanning optical unit, and the slit is used for the synchronization detection. 3. The multi-beam scanning optical system according to claim 1, further comprising a correction unit that moves the optical unit in the optical axis direction. 8. At least a part of the lens forming the lens unit is integrated with the scanning optical unit, and a correcting unit for moving at least a part of the lens forming the scanning optical unit in the main scanning direction is provided. 2. The method according to claim 1, wherein
Or the multi-beam scanning optical system according to 2. 9. An incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units arranged apart from the main scanning direction to a deflecting unit, and a plurality of light beams deflected by the deflecting unit. After forming a plurality of scanning lines by forming an image on a surface to be scanned and a part of a plurality of light beams deflected by the deflecting means, the light is condensed on a slit surface by a lens unit, and then synchronized. A multi-beam scanning optical system, comprising: a synchronization detection optical unit that guides light to a detection element and controls timing of a scanning start position on the surface to be scanned for each of the plurality of light fluxes using a signal from the synchronization detection element. A dot for each scanning line on the surface to be scanned, which is generated by having a focus position deviation amount δM1 in a main scanning cross section of a light beam guided to the synchronous detection element as viewed from the slit. Correction to correct misalignment A multi-beam scanning optical system comprising: 10. The multi-beam scanning optical system according to claim 9, wherein said dot displacement amount is equal to or less than 1/2 of the resolution in the sub-scanning direction. 11. The multi-beam scanning optical system according to claim 9, wherein said plurality of light emitting units are arranged apart from each other in a main scanning direction and a sub-scanning direction. 12. The multi-beam scanning optical system according to claim 11, wherein said slit is inclined in the sub-scanning direction in accordance with a dot displacement amount for each scanning line on said surface to be scanned. 13. A rotating means for rotating the slit or a unit including the slit about the optical axis of the optical means for synchronization detection in accordance with the amount of dot displacement for each scanning line on the surface to be scanned. Claim 1 characterized by the following:
2. The multi-beam scanning optical system according to 1. 14. An incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from the main scanning direction to a deflecting unit, and a plurality of light beams deflected by the deflecting unit. A scanning optical unit that forms a plurality of scanning lines by forming an image of the light beam on the surface to be scanned, and a part of the plurality of light beams deflected by the deflecting unit is guided to a synchronization detection element by a lens unit, and the synchronization is performed. A synchronous detection optical means for controlling a timing of a scanning start position on the surface to be scanned for each of the plurality of light beams by using a signal from the detection element, wherein a multi-beam scanning optical system comprising: | ΔM2 | ≦ δYmax / tan (θmax) (where, δM2 is a focus position deviation amount in the main scanning cross-section of a light beam guided to the synchronous detection element viewed from the light receiving surface of the synchronous detection element. ΔYmax: allowable Each scanning line that can be The dot position deviation amount .theta.max: multi-beam scanning optical system, characterized in that the maximum angle difference) satisfy the incident angle to the light receiving surface of the light beams used to detect synchronization. 15. The multi-beam scanning optical system according to claim 14, wherein the permissible dot position shift amount for each scanning line is equal to or less than の of the resolution in the sub-scanning direction. 16. A correcting means for shifting a focus position of a light beam guided to the synchronization detecting element in a main scanning section relative to a light receiving surface of the synchronization detecting element in an optical axis direction of the synchronization detecting optical means. 16. The multi-beam scanning optical system according to claim 14, further comprising: 17. A correction means for moving a position of the synchronization detecting element or a unit including the synchronization detecting element in an optical axis direction of the synchronization detecting optical means. The multi-beam scanning optical system as described in the above. 18. The lens unit is provided in an optical path between the deflecting unit and the synchronization detecting element, and comprises a correcting unit for moving the lens unit in the optical axis direction of the synchronization detecting optical unit. 16. The multi-beam scanning optical system according to claim 14, wherein: 19. At least a part of the lens constituting the lens unit is integrated with the scanning optical unit, and at least a part of the lens unit not integrated with the scanning optical unit is used for the synchronization detection. 16. The multi-beam scanning optical system according to claim 14, further comprising a correction unit that moves the optical unit in the optical axis direction. 20. The lens unit according to claim 1, wherein the lens unit is integrated with the scanning optical unit, and the lens unit includes a correcting unit for moving at least a part of the optical element of the scanning optical unit in the optical axis direction of the scanning optical unit. 16. The multi-beam scanning optical system according to claim 14, wherein: 21. At least a part of the lens forming the lens unit is integrated with the scanning optical unit, and a correcting unit for moving at least a part of the lens forming the scanning optical unit in the main scanning direction is provided. 16. The multi-beam scanning optical system according to claim 14, wherein: 22. An incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units disposed apart from the main scanning direction to a deflecting unit, and a plurality of light beams deflected by the deflecting unit. Scanning optical means for forming an image on a surface to be scanned, and a part of a plurality of light beams deflected by the deflecting means are condensed on a slit surface by a lens unit, and then guided to a synchronous detection element. A synchronous detection optical means for controlling the timing of the scanning start position on the surface to be scanned by using a signal from the synchronous detection element. Assuming that the amount of focus shift of the emitted light beam in the main scanning section is δM1 and the amount of focus shift of each image height on the surface to be scanned is δX, the following conditional expression is given as | δX−δM1 | ≦ δYmax / Θmax (however ΔYmax: allowable dot position shift amount for each scanning line θmax: maximum angle difference of incidence angle of each light beam used for synchronization detection on the slit surface). 23. The multi-beam scanning optical system according to claim 22, wherein the permissible dot displacement for each scanning line is equal to or less than half the resolution in the sub-scanning direction. 24. A device comprising a correcting means for shifting a focus position of a light beam guided to the synchronous detecting element in a main scanning section in the optical axis direction of the synchronous detecting optical means relatively from the slit. 24. The multi-beam scanning optical system according to claim 22, wherein: 25. The apparatus according to claim 2, further comprising a correcting unit for moving a position of the slit or a unit including the slit in an optical axis direction of the synchronization detecting optical unit.
24. The multi-beam scanning optical system according to 2 or 23. 26. The apparatus according to claim 26, wherein said lens unit is provided in an optical path between said deflecting unit and said slit, and comprises a correcting unit for moving said lens unit in an optical axis direction of said synchronization detecting optical unit. The multi-beam scanning optical system according to claim 22, wherein: 27. An incident optical unit for guiding a plurality of light beams emitted from a light source unit having a plurality of light emitting units arranged apart from the main scanning direction to a deflecting unit, and a plurality of light beams deflected by the deflecting unit. After forming a plurality of scanning lines by forming an image on a surface to be scanned and a part of a plurality of light beams deflected by the deflecting means, the light is condensed on a slit surface by a lens unit, and then synchronized. A multi-beam scanning optical system, comprising: a synchronization detection optical unit that guides light to a detection element and controls timing of a scanning start position on the surface to be scanned for each of the plurality of light fluxes using a signal from the synchronization detection element. In the system, δM1 is the focus position shift amount in the main scanning cross section of the light beam guided to the synchronous detection element viewed from the slit, and δX is the focus position shift amount of each image height on the scanned surface. Sometimes, the focus position of both Is the amount of delta] M1, multi-beam scanning optical system, characterized by comprising correction means for correcting the dot position deviation for each scan line in the scanned plane generated by δX with the difference. 28. The apparatus according to claim 27, wherein the dot displacement amount is equal to or less than half the resolution in the sub-scanning direction.
A multi-beam scanning optical system according to any of the preceding claims. 29. The multi-beam scanning optical system according to claim 27, wherein the plurality of light emitting units are arranged apart from each other in the main scanning direction and the sub-scanning direction. 30. The multi-beam scanning optical system according to claim 29, wherein the slit is inclined in the sub-scanning direction according to a dot displacement amount for each scanning line on the surface to be scanned. 31. Rotating means for rotating the slit or a unit including the slit around the optical axis of the synchronization detecting optical means in accordance with the amount of dot displacement for each scanning line on the surface to be scanned. 3. The method according to claim 2, wherein
10. The multi-beam scanning optical system according to 9. 32. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to a deflecting means, and a plurality of light beams deflected by the deflecting means. Scanning optical means for forming an image on a surface to be scanned, and a part of a plurality of light beams deflected by the deflecting means are guided to a synchronization detecting element by a lens unit, and the signal is used by using a signal from the synchronization detecting element. A synchronous detection optical means for controlling the timing of the scanning start position on the surface to be scanned, and a multi-beam scanning optical system comprising: a light beam guided to the synchronous detection element as viewed from a light receiving surface of the synchronous detection element; The deviation of the focus position in the main scanning section is δ
M2, where δX is the focus position shift amount of each image height on the surface to be scanned, the following conditional expression is satisfied: | δX−δM2 | ≦ δYmax / θmax (where, δYmax: allowable dot position for each scanning line) A multi-beam scanning optical system that satisfies a deviation amount θmax: a maximum angle difference between incident angles of light beams used for synchronous detection on a light receiving surface. 33. The multi-beam scanning optical system according to claim 32, wherein the permissible dot shift amount for each scanning line is equal to or less than half the resolution in the sub-scanning direction. 34. A correcting means for shifting a focus position of a light beam guided to the synchronization detecting element in a main scanning direction relative to a light receiving surface of the synchronization detecting element in an optical axis direction of the synchronization detecting optical means. 34. The multi-beam scanning optical system according to claim 32, wherein: 35. The apparatus according to claim 32, further comprising correction means for moving a position of said synchronization detection element or a unit including said synchronization detection element in an optical axis direction of said synchronization detection optical means. A multi-beam scanning optical system according to any of the preceding claims. 36. The lens unit is provided in an optical path between the deflecting unit and the synchronization detecting element, and includes a correcting unit for moving the lens unit in the optical axis direction of the synchronization detecting optical unit. 34. The multi-beam scanning optical system according to claim 32, wherein: 37. The multi-beam scanning optical system according to claim 1, a photosensitive member disposed on the surface to be scanned, and a light beam scanned by the multi-beam scanning optical system. A developing device for developing the electrostatic latent image formed on the photoreceptor as a toner image, a transfer device for transferring the developed toner image to a transfer material, and fixing the transferred toner image to the transfer material An image forming apparatus comprising a fixing device. 38. A multi-beam scanning optical system according to any one of claims 1 to 36, and a printer controller for converting code data input from an external device into an image signal and inputting the image signal to the multi-beam scanning optical system. An image forming apparatus comprising: 39. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to a deflecting means, and a plurality of light beams deflected by the deflecting means. After forming a plurality of scanning lines by forming an image on a surface to be scanned and a part of a plurality of light beams deflected by the deflecting means, the light is condensed on a slit surface by a lens unit, and then synchronized. A multi-beam scanning optical system, comprising: a synchronization detection optical unit that guides light to a detection element and controls timing of a scanning start position on the surface to be scanned for each of the plurality of light fluxes using a signal from the synchronization detection element. A dot for each scanning line on the surface to be scanned, which is generated by having a focus position shift amount δM1 in a main scanning cross section of a light beam guided to the synchronous detection element as viewed from the slit. Position shift amount is side running A multi-beam scanning optical system, wherein the resolution is not more than 1/2 of the resolution in the scanning direction. 40. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions disposed apart from the main scanning direction to a deflecting means, and a plurality of light beams deflected by the deflecting means. A scanning optical unit for forming a plurality of scanning lines by forming an image on a surface to be scanned, and a part of a plurality of light beams deflected by the deflecting unit are guided to a synchronization detecting element by a lens unit, and the synchronization detection is performed. A multi-beam scanning optical system comprising: a synchronization detection optical unit that controls a timing of a scanning start position on the surface to be scanned for each of the plurality of light fluxes using a signal from an element. Focus shift amount δ in the main scanning section of the light beam guided to the synchronous detection element viewed from the light receiving surface
A multi-beam scanning optical system characterized in that the amount of dot displacement for each scanning line on the surface to be scanned caused by having M2 is equal to or less than half the resolution in the sub-scanning direction. 41. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions disposed apart from the main scanning direction to a deflecting means, and a plurality of light beams deflected by the deflecting means. After forming a plurality of scanning lines by forming an image on a surface to be scanned and a part of a plurality of light beams deflected by the deflecting means, the light is condensed on a slit surface by a lens unit, and then synchronized. A multi-beam scanning optical system, comprising: a synchronization detection optical unit that guides light to a detection element and controls timing of a scanning start position on the surface to be scanned for each of the plurality of light fluxes using a signal from the synchronization detection element. In the system, δM1 is a focus position shift amount in a main scanning cross section of a light beam guided to the synchronous detection element viewed from the slit, and δX is a focus position shift amount of each image height on the scanned surface. When both focus Location shift amount delta] M1, 1/2 dot position deviation amount for each scan line in the scanned plane generated by the δX has a difference in the sub-scanning direction resolution
A multi-beam scanning optical system characterized by the following. 42. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to a deflecting means, and a plurality of light beams deflected by the deflecting means A scanning optical unit for forming a plurality of scanning lines by forming an image on a surface to be scanned, and a part of a plurality of light beams deflected by the deflecting unit are guided to a synchronization detecting element by a lens unit, and the synchronization detection is performed. A synchronous detection optical means for controlling the timing of a scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from an element, wherein a light receiving surface of the synchronous detection element is provided. Assuming that the amount of focus shift in the main scanning cross section of the light beam guided to the synchronous detection element as viewed from above is δM2 and the amount of focus shift of each image height on the scanned surface is δX, Position shift amount δM
2. A multi-beam scanning optical system characterized in that the amount of dot misregistration for each scanning line on the scanned surface caused by the difference in .delta.X is not more than 1/2 of the resolution in the sub-scanning direction.