JPH07234370A - Method for adjusting scanning optical device - Google Patents

Abstract

PURPOSE:To obtain an output of high quality by suppressing the curvature and tilt of a scanned surface for the adjusting method of the optical scanning device. CONSTITUTION:In the assembling process of the adjusting method of the scanning optical device, an ftheta lens 16 which has its adhesion surface coated with a photosetting adhesive is mounted on a base 17 where all optical elements except the ftheta lens 16 are assembled, and while light is emitted by a light source 11, an optical deflector 15 is rotated to make an optical scan; and CCD sensors 21 arranged at plural positions on the scanned surface 20 measure the irradiated position and the curvature and tilt of the scanned surface 20 are calculated. A control circuit 22 calculates the movement quantity of the ftheta lens 16 to be corrected by using a prepared look-up table and moves up and down arms 18a and 18b independently to move up and down the ftheta lens 16, thereby correcting the curvature and tilt on the scanned surface 20. After the adjustment, the ftheta lens 16 is fixed to the base 17 by an ultraviolet ray irradiating mechanism.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an electrophotographic process for recording image information by deflecting a light beam emitted from a light source with a deflecting element and optically scanning the surface to be scanned through an f.theta. Lens. The present invention relates to a method for adjusting a scanning optical device suitable for a laser beam printer (LBP), a digital copying machine and the like.

[0002]

2. Description of the Related Art Conventionally, in a scanning optical device such as an LBP, a light beam emitted from a light source means is optically modulated according to an image signal. Then, this light-modulated light beam is periodically deflected by an optical deflector composed of a polygon mirror, and f
An image is recorded on a photosensitive recording medium surface in the form of a spot by an image forming optical system having a θ characteristic.

FIG. 5 is a schematic view of a conventional scanning optical device, in which a collimator lens 2 is provided in the emitting direction of a light source 1, and an optical deflector 5 comprising a diaphragm 3, a cylindrical lens 4 and a polygon mirror on the optical axis thereof. Are arranged in sequence. Further, in the reflection direction of the optical deflector 5, an imaging optical system 6 having an fθ characteristic and a surface to be scanned 7 such as a photosensitive drum are provided.

The divergent light beam emitted from the light source 1 is converted into a substantially parallel light beam by the collimator lens 2, and the parallel light beam is limited by the diaphragm 3 and enters the cylindrical lens 4.
The cylindrical lens 4 has a refracting power only in the sub-scanning direction, and the incident light beam is focused on the main scanning surface and is focused on the reflecting surface of the optical deflector 5 as a substantially linear image. The light beam reflected and deflected by the reflecting surface of the optical deflector 5 is condensed via the imaging optical system 6, and the surface to be scanned 7 is scanned by rotating the optical deflector 5 in the direction of the arrow in the figure. ing.

As another conventional example, as shown in FIG. 6, from the light source 1 to the cylindrical lens 4, especially f
There is also known a scanning optical device which is arranged in a plane including the optical axis of the θ lens 6 and the rotation axis of the optical deflector 5 and is configured to have symmetry with respect to the optical axis of the imaging optical system 6. ing.

[0006]

In order to obtain a high-quality output when the scanning optical device as described above is used by incorporating it into a device such as an LBP or a digital copying machine, the surface to be scanned in the scanning optical device is to be obtained. The bend and tilt of the must be suppressed. Since the bending and inclination of the surface to be scanned are caused by the positional deviation and inclination of the optical components within a predetermined range, conventionally, this is dealt with by increasing the precision of the optical components and the mounting base. Has the drawbacks of being limited and costly. Regarding the tilt of the scanned surface, the tilt of the base, folding mirror, etc. is adjusted,
It is difficult to obtain good linearity of the surface to be scanned, because there is no realistic adjustment method for bending.

Further, as in the conventional example described later, in the scanning optical device in which the light flux to the deflecting element is made incident from the surface including the rotation axis of the deflecting element and the optical axis of the fθ lens, the reflecting surface of the deflecting element moves forward and backward. However, there is a problem that the height of the line image on the reflecting surface changes and the surface to be scanned is bent.

The object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a method for adjusting a scanning optical device that can obtain a higher quality output.

[0009]

A method for adjusting a scanning optical device according to the present invention for achieving the above object comprises a first optical system for converting a light beam emitted from a light source, and the first optical system. A deflecting element for deflecting a light beam emitted from the scanning optical device; and a second optical system for forming a light beam deflected and scanned by the deflecting element into a spot on the surface to be scanned. The second optical system is placed on the base in a state where the adhesive is applied, the position of the first or second optical system is optically adjusted before the adhesive is cured, and the adhesive is applied after the adjustment. It is characterized in that the agent is cured to fix its position.

[0010]

In the method of adjusting the scanning optical device having the above-mentioned structure, the adhesive is used as a means for fixing the first or second optical system to the base, and the position of the optical element is adjusted before the adhesive is cured. After the adjustment, the adhesive is cured to fix the optical element and improve the output to the surface to be scanned.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is an explanatory diagram of an adjusting method for a scanning optical device according to a first embodiment of the present invention. A collimator lens 12 is provided in the emitting direction of a light source 11 made of a semiconductor laser, and a diaphragm 13 and a cylindrical lens 1 are provided on the optical axis thereof.
4. An optical deflector 15 composed of a polygon mirror is arranged.
The optical deflector 15 is rotatably held by a rotating shaft having a driving means such as a motor. In the reflection direction of the optical deflector 15, the fθ lens 16 is placed on the base 17 and is not fixed, and the arms 18 are provided on the upper left and right two positions of the fθ lens 16.
Attach a and 18b. Behind the fθ lens 16, a folding mirror 19 and a scanned surface 20 are provided.
The CCD sensor 2 is located at a plurality of positions through the objective lens.
Place 1 The output of the CCD sensor 21 is the control circuit 22.
The output of the control circuit 22 is connected to an elevating mechanism 23 incorporating a stepping motor, for example, and the arms 18a and 18b are connected to the elevating mechanism 23.

Here, the fθ lens 16 is composed of one lens having different curvatures in the main scanning direction and the sub-scanning direction, and the shape of the lens surface is an aspherical surface. This aspherical shape has an origin at the intersection of the fθ lens 16 and the optical axis, the optical axis direction is the X axis, the axis orthogonal to the optical axis in the main scanning plane is the Y axis, and the optical axis in the sub scanning plane is orthogonal to the optical axis. Is the Z axis,

Regarding the main scanning direction, R is the radius of curvature,
When K, B ₄ , B ₆ , B ₈ and B ₁₀ are aspherical coefficients, the following equation is obtained. X = (Y ² / R) / [1+ {1- (1 + K) ・ (Y /
R) ² } ^1/2 ] ＋ B ₄ Y ⁴ ＋ B ₆ Y ⁶ ＋ B ₈ Y ⁸ ＋ B ₁₀ Y ¹⁰

In the sub-scanning direction, r is the radius of curvature,
When D ₂ , D ₄ , D ₆ , D ₈ and D ₁₀ are aspherical coefficients, the following equation is obtained. ^{X = (z 2 / r)} / [1+ {1- (z / r ') 2} 1/2] However, r' = r (1 + D 2 Y 2 + D 4 Y 4 + D 6 Y 6 + D 8 Y
⁸ + D ^₁₀ Y ₁₀₎

The above equation indicates that the generatrix direction is an aspherical surface that can be expressed by a function up to the tenth order, and that the sagittal direction is a toric surface having a different curvature depending on the value of Y.

In this embodiment, in the assembling process of the scanning optical device as described above, as shown in FIG.
Fθ lens 1 in which the photo-curable adhesive B is applied to the bonding surface with the base 17 on the base 17 on which all optical elements other than
Place 6. Here, the light source 11 is caused to emit light and the optical deflector 15
Is rotated to perform optical scanning, the irradiation position is measured by CCD sensors 21 arranged at a plurality of positions on the surface 20 to be scanned, and the output is sent to the control circuit 22. The control circuit 22 bends the surface 20 to be scanned. And the slope is calculated.

When the surface to be scanned 20 is not bent or tilted within a certain range, the control circuit 22 calculates the amount of movement of the fθ lens 16 to be corrected from the look-up table prepared in advance, and the elevating mechanism 23. To move the two arms 18a and 18b connected to the elevating mechanism 23 up and down independently of each other.
Is moved to correct the bending and inclination on the surface 20 to be scanned. Further, by repeating this series of routines, it is possible to more accurately correct the bending and inclination of the surface 20 to be scanned. After the adjustment, the ultraviolet ray irradiation mechanism 24 irradiates the adhesive surface with ultraviolet rays to cure the adhesive B, thereby fixing the fθ lens 16 to the base 17.

In this embodiment, the photo-curing adhesive is used as the adhesive B, but the same effect can be obtained by using other adhesive such as thermosetting adhesive.

Table 1 shows design values of the adjusting method of the scanning optical device in this embodiment.

Table 1 Design values of the first embodiment Scanning width 210 mm Wavelength 780 mm fθ lens refractive index 1.52 Collimator light beam focusing position from polarizer 239 mm Polarizer-slit 27 mm Slit-fθ lens 1 surface 3 mm fθ lens meat Thickness 6 mm fθ lens 2 surface−scanned surface 111.9 mm fθ lens main scanning direction cross-sectional shape 1 surface 2 surface R 2.53125E + 01 R 2.796334E + 01 K −4.23698E + 00 K −5.30040E + 00 B ₄ −4.233617E _{-06 B 4 -4.67247E-06 B 6} 2.09448E-09 B 6 2.00841E-09 B 8 -5.83344E-13 B 8 -5.98012E-13 B 10 7.79461E-17 B 10 8 .93499E-17 f [theta] lens cross-sectional shape in the sub-scanning direction 1 surface 2 surface r -4.8 5318E + 01 r -1.11620E + 01 D 2 U 1.60939E-03 D 4 U -3.29657E-06 D 6 U 3.52198E-09 D 8 U -1.87739E-12 D 10 U 3.86902E-16 D 2 L 1.54392E-03 D ₄ L -3.01900E-06 D ₆ L 2.95771E-09 D ₈ L -1.41801E-12 D ₁₀ L 2.60958E-16

Table 2 shows that when the fθ lens 16 is rotated 5 ′ about its optical axis and in the height direction, it is 0.1 m.
It shows correction values for the irradiation position of each light beam, the tilt of the surface to be scanned, and the bending when the light is raised by m. As described above, by moving the fθ lens 16 in the vertical direction or rotating it about the optical axis, it is possible to correct the inclination and bending of the surface to be scanned.

Table 2 Irradiation position fθ lens Start side Central end side Tilt Bending height 0.1 up 0.306 0.398 0.308 -0.002 -0.091 5'rotation of optical axis center 0.106 0 -0.103 -0.209 0

FIG. 3 is a block diagram of the second embodiment.
Instead of the two arms 18a and 18b in the above embodiment, one arm 31 is attached to the center of the upper part of the fθ lens 16 and is connected to the elevating mechanism 23.

The second embodiment is different from the first embodiment in that the arms 18a and 18b are used to form the fθ lens 1.
6 does not move up and down independently left and right, but the arm 31
Therefore, the fθ lens 16 is moved up and down in parallel with the base 17, and the other points are the same as in the first embodiment. In this embodiment, the bending of the surface to be scanned can be corrected more easily than in the first embodiment, but as can be seen from Table 2, the tilt cannot be corrected, and therefore the folding mirror 19 or the base 17 has a tilt adjusting function. It is necessary to have.

FIG. 4 is a block diagram of the base portion of the cylindrical lens 14 in the third embodiment. The base 32 is fixed on the base 17, and the upper portion of the cylindrical lens 14 having the bottom surface coated with the adhesive B is adhered. An arm 33 is attached at the center, and this arm 33 is connected to the lifting mechanism 23.

The third embodiment differs from the first embodiment in that the f.theta. Lens 16 is fixed on the base 17 from the beginning and the f.theta. Lens 16 is moved, but the cylindrical lens 14 is moved vertically. This is the same as in the first embodiment except that the light beam is bent and tilted on the surface to be scanned 20 by moving it.

As in the first embodiment, the arm 33 is moved up and down, and the CCD sensor 21 is used to adjust the bending and inclination on the surface 20 to be scanned, and then the ultraviolet rays are irradiated to the adhesive B.
Is cured and the cylindrical lens 14 is fixed on the pedestal 32.

Table 3 shows the irradiation position of the light beam, the inclination of the surface to be scanned, and the correction value of the curve when the cylindrical lens 14 is shifted upward by 0.1 mm in the scanning optical device based on the design values of Table 1. It is a thing. Note that, in the present embodiment as well, as in the second embodiment, the inclination on the scanned surface 20 cannot be corrected, so it is necessary to perform the correction separately.

Table 3 Irradiation position Cylindrical lens Start side Center end side Tilt Bending height 0.1 up -0.186 -0.265 -0.184 -0.002 -0.08

After the adjustment is completed, the divergent light beam emitted from the light source 11 in FIG. 1 becomes a parallel light beam by the collimator lens 12, the light amount is limited by the diaphragm 13, and the light beam enters the cylindrical lens 14. Since the cylindrical lens 14 has a refracting power only in the sub-scanning direction, the light beam in the main scanning direction is incident on the optical deflector 15 as it is, but the light beam in the sub-scanning direction is in the cylindrical lens 1.
An image is formed in the vicinity of the deflecting / reflecting surface of the optical deflector 15 by 4. Therefore, the light beam incident on the optical deflector 15 becomes a long line image in the main scanning direction and is deflected by the rotation of the optical deflector 15 in the arrow direction. The light beam deflected by the optical deflector 15 enters the fθ lens 16 and is further reflected by the folding mirror 19.
And is imaged on the surface to be scanned 20, and the surface to be scanned 20 is optically scanned with high precision.

[0031]

As described above, in the method for adjusting the scanning optical device according to the present invention, when fixing the first optical system or the second optical system to the base, these positions are set before the adhesive is cured. Adjustment is performed and fixing is performed by curing the adhesive after the adjustment, and the correction on the surface to be scanned is performed easily and at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment.

FIG. 2 is an explanatory diagram of an fθ lens unit.

FIG. 3 is an explanatory diagram of a second embodiment.

FIG. 4 is an explanatory diagram of a third embodiment.

FIG. 5 is an explanatory diagram of a conventional example.

FIG. 6 is an explanatory diagram of another conventional example.

[Explanation of reference numerals] 11 light source 14 cylindrical lens 15 light deflector 16 fθ lens 17 base 18a, 18b, 31, 33 arm 21 CCD sensor 22 control circuit 23 lifting mechanism 24 ultraviolet irradiation device 32 pedestal

Claims (2)

[Claims] 1. A first device for converting a light beam emitted from a light source.
Optical system, a deflecting element for deflecting the light beam emitted from the first optical system, and a second optical system for forming a light beam deflected and scanned by the deflecting element into a spot on the surface to be scanned. In the scanning optical device having the above, the first or second optical system is placed on a base with an adhesive applied, and the position of the first or second optical system is set before the adhesive is cured. 2. The method for adjusting a scanning optical device, wherein the optical adjustment is performed, and after the adjustment, the adhesive is cured to fix the position. 2. The method for adjusting a scanning optical device according to claim 1, wherein the adhesive is a photocurable adhesive.