JPH04251815A - Optical scanner - Google Patents

Abstract

PURPOSE:To suppress scanning line curvature. CONSTITUTION:In the optical scanner which scans the surface of a photosensitive body 41Y for exposure by deflecting laser light by a polygon mirror 31Y rotated by a motor 32Y, the inclination of the deflector 33Y consisting of polygon mirrors 31Y and 32Y is varied by adjusting the screw-in quantity of a screw (SC2). Consequently, the curvature of the scanning line of the laser light on the surface of the photosensitive body 41Y is corrected.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device for printers, copiers, facsimile machines, etc. that use laser light.

0002

2. Description of the Related Art FIG. 7 shows an outline of the structure of a mechanical unit (RCM) of a conventional digital color printer. In this type of digital color printer, along the tensioning/moving direction of the transfer belt 40, there are a BK (black) optical scanning device 13BK, a C (cyan) optical scanning device 13C, and an M
A (magenta) optical scanning device 13M and a Y (yellow) optical scanning device 13Y are arranged in this order.

FIGS. 8 and 9 show the configuration of the exposure system of the optical scanning device 13Y. A laser beam emitted from a laser diode 43y is reflected by a polygon mirror 31Y, passes through an fθ lens 36Y, is further reflected by a mirror 37Y and MRY, and is irradiated onto the photosensitive drum 41Y through a dustproof glass 37WY. . Since the polygon mirror 31Y is rotated at a constant speed by the motor 32Y, the laser beam moves in a direction along the axis of the photoreceptor drum 41Y (main scanning direction). The base point for main scanning scanning position tracking is set by detecting laser light at a non-exposure position with the photo sensor 38Y.

[0004] The laser diode 43y outputs recording data (
Since the light emission is energized based on the binary data (recorded/non-recorded), the exposure corresponding to the recorded data is applied to the photoreceptor drum 41.
It is done on the surface of Y. The surface of the photosensitive drum 41Y is uniformly charged in advance by a charger 42Y, and an electrostatic latent image corresponding to the original image is formed by the exposure. The electrostatic latent image is Y
It is developed by the developing device 44Y to become a Y color toner image. This toner image is placed on the upper part of the transfer charger 45Y and placed in the cassette 46a.
Alternatively, the paper is fed out from the paper feed roller 47a or 47b from the paper feed roller 47a or 47b, and sent out to the transfer belt 40 by the registration roller 48 in synchronization with the toner image formation by the BK optical scanning device 13BK. Next, the image is transferred onto a recording sheet that is conveyed to the left by this transfer belt 40.

Other optical scanning devices 13BK, 13C and 1
3M also has the same configuration and function as the optical scanning device 13Y, but 13BK has a BK (black) toner developing device 44.
13C is a C (cyan) toner developing device 44C, and 13M is an M (magenta) toner developing device 44M.
, the recorded colors are different. Note that the optical scanning device 13
Among other members of BK, 13C, and 13M, optical scanning device 1
Components corresponding to 3Y are given the same reference numerals BK, C, and M in the drawings, and detailed explanations are omitted.

[0006]

[Problems to be Solved by the Invention] However, in an optical scanning device that performs line scanning using a laser beam, such as the above-mentioned printer,
If the polygon mirror 31Y serving as the deflector 33Y is tilted, the scanning line of the laser beam to the photoreceptor drum 41Y will be bent. The polygon mirror 31Y is tilted due to the inclination of the mounting surface of the deflector 33Y to the housing 30 and the inclination of the deflector mounting surface of the housing 30. If the polygon mirror 31Y is tilted, the laser beam
The light is incident obliquely to the optical axis of the θ lens 36Y, and in this case, as shown in FIG.
Distortion may occur in the scanning line (SLY) of the laser beam to Y.

Specifically, for example, if the distance between the mounting parts of the deflector 33Y in the optical system of FIG. 9 is 98 mm, and the dimensional tolerance of the deflector mounting surface of the housing 30 with respect to the reference surface is ±0.04 mm, The tolerance is converted into an angle as follows: θ1 = arctan (0.08/98) = 0.046
If the perpendicularity of the polygon mirror 31Y to the housing mounting surface is 90°±7', then 60'=1°, so θ2 =7/60=0.1167°. Therefore, the housing 3 of the polygon mirror 31Y
The slope θ with respect to the reference plane at 0 is: θ=θ1 +θ2 =0.0468°+0
．． 1167°=0.1634°. The relationship between the inclination angle θ (deg) of the polygon mirror 31Y and the bending amount (W) μm of the scanning line (SLY) is expressed by the following equation. W=K×θ

...(1) However, K=198 (μm/d
eg) ∴W = 198 x 0.1634° = 32.4 (μm), and in the above optical system, the deflector 33Y is
The tilt causes scanning line bending (distortion) of up to 32.4 μm.

On the other hand, the amount of distortion is
M, 13C, and 13BK may differ. For example, if optical scanning devices 13M, 13C, and 13BK have virtually no distortion, but if distortion (bending) occurs in optical scanning device 13Y as shown in FIG.
While the record of K becomes RSLY shown in Fig. 11, 1
Since the recording of 3Y becomes TSLY shown in FIG. 12, this results in color shift on the recording paper.

[0009] The above-mentioned recording deviation is caused by a change in hue (
(deterioration) or color bleeding or color shift, resulting in a decline in color recording quality. In the case of monochrome recording, there is no problem of color shift, but strictly speaking, it results in a decrease in the linearity of copying or distortion of the image, so it is desirable to improve this problem in the case of mixed color recording and monochrome recording as well. .

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical scanning device that can suppress scanning line bending and obtain high quality color recording.

[0011]

[Means for Solving the Problems] The above object is to deflect a laser beam modulated by an image signal using a deflector, and scan the deflected laser beam on a photoreceptor through an imaging lens. This is achieved by providing an adjustment means for adjusting the mounting angle of the deflector in the scanning device. Note that as the adjusting means, a screw means for attaching the deflector to the housing of the optical scanning device main body can be used, or a piezoelectric actuator provided between the deflector and the housing of the optical scanning device main body can be used.

0012

[Operation] The mounting angle of the deflector relative to the housing of the main body of the optical scanning device is adjusted by operating the adjusting means. Specifically, the voltage applied to the piezoelectric actuator provided between the deflector and the housing of the optical scanning device main body is controlled by rotating the screw means that attaches the deflector to the housing of the optical scanning device main body, or by rotating the screw means that attaches the deflector to the housing of the optical scanning device main body. It is done by changing.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing an outline of the structure of an image signal processing system of a digital color copying machine incorporating an embodiment of the present invention.

To explain the outline of image information processing with reference to the same figure, the reflected light of a document set in a color document reading device (not shown) is separated into R, G, and B, and the solid-state image sensor (
CCD) 1r, 1g, 1b. These outputs are analog/digital converted by A/D converters 2r, 2g, and 2b and input to the shading correction section 3. The shading correction circuit 100 made up of these parts includes a CCD
Color gradation data obtained by digitally converting the output signals of 1r, 1g, 1b, optical illuminance unevenness, CCD 1r, 1g, 1b
The color gradation data is created by correcting variations in sensitivity of the internal unit elements, etc., and then reading the data.

The γ correction circuit 4 of the various processing units 101 changes the shading-corrected color gradation data in accordance with the photoreceptor characteristics of the photoreceptor developing system RCM having the same configuration as that shown in FIG. The gradation is changed in response to an adjustment instruction input using an operation button (not shown).

The masking correction circuit 5 converts and corrects the read color information into density information of the recording colors C, M, Y, and BK in accordance with the characteristics of the spectral reflection wavelength of the toner for forming a recorded image. Here, a masking coefficient (color correction parameter) is changed in response to a hue adjustment instruction input from the console 103, and the above conversion and correction calculations are performed based on this masking coefficient.

The UCR processing circuit 6 performs correction for color balance in overlapping toners of each color. The magnification processing circuit 7 performs thinning (for reduction), interpolation (for enlargement), etc. of the recording density data (one data per pixel) in accordance with the designated copying magnification.

The dither processing circuit 8 converts each recording color density data into gradation recording data (binary signal: 1 bit/1 pixel) indicating recording/non-recording distribution in units of predetermined small areas.

The photoreceptor developing system RCM has a configuration similar to that shown in FIG. 7, and although not shown here, the surface of the photoreceptor drum is uniformly charged and the charged surface is exposed to laser light to form a latent image. These toner developing devices are arranged along the moving direction of the recording paper. That is, BK, C, M, and Y toner developing devices are arranged from the upstream side of the recording paper, and the laser diodes 43bk, 43 of the recording scanning system 102
c, 43m, and 43y are the respective optical scanning devices 13
The surface of the photosensitive drum is exposed and scanned via BK, 13C, 13M, and 13Y.

With the above arrangement of the optical scanning devices, the laser diode 43bk starts exposure first, and the laser diode 43y starts exposure last. Since there is a time difference in the order of exposure start between the optical scanning devices, in order to hold the recorded data (output of the dither processing circuit 8) during these time differences, the recording scanning system 102 includes three sets of buffer memories 9y.
, 9m, and 9c are equipped. Laser drivers 10y, 10m, 1 energize the laser diodes 43y, 43m, 43c, 43bk to emit light in accordance with the recording data.
0c and 10bk are provided.

In addition to the input/output elements of the copying machine, the console 103 is equipped with input means for tone adjustment and input means for hue adjustment. The input of the console 103 is the microprocessor (CPU) 1 of the control system 12.
4 reads. The microprocessor 14 provides timing data to a synchronous control circuit 15, and the synchronous control circuit 15 provides timing signals to the image processing systems 100, 101, 102, and RCM described above. The microprocessor 14 sends adjustment data and control signals to the image processing systems 100, 101, 10.
2. Give to RCM.

FIG. 1 is a sectional view of a first embodiment of the present invention, in which members corresponding to those explained with reference to FIG. 7 are given the same reference numerals. In FIG. 1, the housing 30 of the optical system of the Y light scanning device 13Y includes a polygon mirror 31Y and a motor 3.
A deflector 33Y consisting of 2Y is attached. This deflector 33Y has one end (lower side in FIG. 1) of its flange 34 screwed to the housing 30 with a screw (SC1). A spring 35 is interposed between the other end (upper side in FIG. 1) of the flange 34 and the housing 30, and by adjusting the screwing amount of the screw (SC2), which is an adjusting means, the distance between the housing 30 and the housing 30 at that position ( Figure 1
(in the horizontal direction) is adjusted. Through this adjustment, the deflector 33Y is rotationally adjusted using the lower part of the flange 34 as a fulcrum.

Therefore, even if the mounting surface of the deflector 33Y to the housing 30 is tilted, or even if the mounting surface of the deflector 33Y of the housing 30 is tilted, the screws (SC
By adjusting the screwing amount in 2), the inclination of the deflector 33Y is changed, the inclination of the polygon mirror 31Y of the deflector 33Y is corrected, and the laser beam is transferred to the fθ lens 36Y.
It is possible to accurately make the light incident on the 6Y optical axis. Therefore, the bending of the scanning line caused by the inclination of the polygon mirror 31Y of the deflector 33Y can be corrected.

BK, M, C optical scanning devices 13BK, 1
The configurations of 3M and 13C are also the same as the configuration of the Y-light scanning device 13Y described above, and similar curves of the scanning line are corrected, so that the scanning line of the all-light scanning device can be made straight.

Next, correction of scanning line curvature will be specifically explained. In the configuration of FIG. 1, the relationship between the rotation angle of the adjustment screw (SC2), the rotation angle of the polygon mirror 31Y, and the adjustment amount of scanning line bending due to the inclination of the polygon mirror 31Y is found to be as follows. Pitch P to 0
．． 5mm (M3 screw), the rotation (adjustment) angle of the screw is T°,
If the deflector mounting hole interval L is 98 mm, the screw (SC2
) advance amount A (mm) is A=P×T/360°, and the inclination angle S (°) of the polygon mirror 31Y, R(
minute) is S=arctan(A/L), R=60×
S...(2) Therefore, from equation (1), the relationship between the screw (SC2) and the scanning line bending adjustment amount W (μm) in this optical system is as shown in FIG. As can be seen from FIG. 3, when the rotation adjustment angle of the screw (SC2) is 30 degrees, the screw advancement amount is about 0.04 mm, and the adjustment amount of the scanning line bending is about 5 μm, making it possible to perform highly accurate adjustment.

FIG. 4 is a sectional view showing a second embodiment of the adjusting means, in which a piezoelectric actuator 50 is provided in place of the screw (SC2) at the same location. In FIG. 3, 51 is a leaf spring that movably supports the flange 34 by pressing the other end of the flange 34 against the piezoelectric quattuator 50, and SC3 is a fixed member that fixes the end of the leaf spring 51 to the housing 30. It's a screw.

The piezoelectric actuator 50 is of the laminated type shown in FIG.
(mm), the piezoelectric constant is d3 3 (m/V), the correction coefficient is M (m2 /V2), the thickness is t (m), and the number of layers is n, then A≒(d3 3 +M・V/ t)・n・V・100 holds true. And polygon mirror 3
The relationship between the tilt angles S (°) and R (minutes) of 1Y and the scanning line bending adjustment amount W (μm) in this optical system is as described in (1) above.
and (2).

Here, the piezoelectric material is P-7 (manufactured by Murata Manufacturing Co., Ltd.).
d3 3 =410×10-1 2 m/V, M=1
．． 08×10-16 m2/V2), t=0.
FIG. 6 shows specific values for the applied voltage V when using the piezoelectric actuator 50 of 2×10 −3 m and n=50. As can be seen from FIG. 6, by applying an appropriate voltage to the piezoelectric actuator 50, the tilt angle of the polygon mirror 31Y can be finely adjusted.

[0029]

As described above, according to the invention described in claim 1, the laser beam modulated by the image signal is deflected by the deflector, and the deflected laser beam is passed through the imaging lens. Since the optical scanning device that scans the photoconductor is provided with an adjusting means for adjusting the mounting angle of the deflector,
The adjustment means adjusts the deflector to the main body of the optical scanning device, thereby correcting the distortion of the laser beam from the deflector, thereby suppressing scanning line bending and obtaining high-quality color recording. It becomes possible. Further, as claimed in claim 2, the adjusting means according to claim 1 is constituted by screw means for attaching the deflector to a housing of a main body of the optical scanning device.
According to the invention described above, the distortion of the laser beam from the deflector can be easily corrected by simply rotating the screw means, so that the same effect as the invention described in claim 1 can be achieved. Furthermore, according to the invention as set forth in claim 3, wherein the adjusting means as set forth in claim 1 is constituted by a piezoelectric actuator provided between the deflector and the housing of the main body of the optical scanning device, the applied voltage applied to the piezoelectric actuator may be controlled. By controlling, the distortion of the laser beam from the deflector can be easily corrected, so that the same effect as the invention described in claim 1 can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of an optical scanning device of the present invention.

FIG. 2 is a configuration diagram of a digital color copying machine incorporating an embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the amount of scanning line bending and the amount of adjustment of the optical system in the first embodiment.

FIG. 4 is a sectional view of a second embodiment of the invention.

FIG. 5 is an explanatory diagram of a piezoelectric actuator.

FIG. 6 is a diagram showing the relationship between the voltage applied to the piezoelectric actuator and the amount of scanning line bending in the second embodiment.

FIG. 7 is a configuration diagram of a digital color printer.

FIG. 8 is a perspective view of the optical scanning device.

FIG. 9 is a cross-sectional view of a conventional optical scanning device.

FIG. 10 is an explanatory diagram showing distortion of scanning lines on a photoreceptor.

FIG. 11 is an explanatory diagram of a recording state on recording paper.

FIG. 12 is an explanatory diagram of a recording state on recording paper.

[Explanation of symbols]

31Y polygon mirror 32Y motor 33Y Deflector 41Y Photoreceptor SC2,50 Adjustment means

Claims (3)

[Claims] 1. An optical scanning device in which a laser beam modulated by an image signal is deflected by a deflector, and the deflected laser beam is scanned onto a photoreceptor through an imaging lens, wherein the deflector is attached to the optical scanning device. An optical scanning device characterized by comprising an adjusting means for adjusting an angle. 2. The optical scanning device according to claim 1, wherein the adjusting means comprises screw means for attaching the deflector to a housing of the optical scanning device main body. 3. The optical scanning device according to claim 1, wherein the adjusting means comprises a piezoelectric actuator provided between the deflector and a housing of the optical scanning device main body.