JPS61295526A - Photoscanner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical scanning device that can easily correct image formation positional deviations on a recording medium caused by various manufacturing errors in a light source and a lens system.

"Prior Art" Conventionally, as shown in FIG. 2, for example, a light source 1 that oscillates a laser beam modulated according to input information, and an image of the laser beam oscillated from the light source 1 as linear focused light. Collimating lens 22 and plano-convex cylindrical lens 21
an imaging lens system 2 consisting of a rotating polygon mirror or other deflector 3 disposed near the imaging position by the imaging lens system 2;
, an fθ lens system 4 that converts the beam reflected and deflected by the deflector 3 into uniform motion, and a recording medium 5 such as a photoreceptor drum that scans the deflected beam from the deflector 3 on a generatrix. , for a composite system with the fθ lens system 4, the fθ lens system 4 and the recording medium 5 are arranged so that the deflection surface of the deflector 3 and the imaging position of the recording medium 5 can maintain a conjugate relationship.
and a surface tilt correction lens system 6 disposed between the
A laser beam oscillated from the light source 1 passes through the imaging lens system 2 and enters the deflector 3 as a linear focused light parallel to the main scanning direction, and is deflected and reflected at a predetermined angle by the rotation of the deflector 3, and is then directed to the fθ lens. After the deflection is converted into a uniform motion by the system 4, the surface tilt of the deflection surface in the sub-scanning direction is corrected by the surface tilt correction lens system 6, and an optical dot pattern corresponding to the input information is formed on the generatrix of the recording medium 5. Optical scanning devices for imaging and scanning are already known.

In this type of device, if processing errors such as surface accuracy or wall thickness accuracy of the various lens systems occur, the laser beam will not be imaged on the photoreceptor generating line, and the image formation position will be shifted in the optical axis C direction. As a result, a problem has arisen in that a clear imaging spot cannot be obtained.

In order to eliminate this drawback, Japanese Patent Application Laid-Open No. 57-144517
In No. 3, the imaging lens system 2 is configured to be movable in the direction of the optical axis C, and as its moving means, for example, as shown in FIG. 3A, the imaging lens system 2 is movable in the direction of the optical axis C. The fixed base 1 is placed on the moving stage +01 and is rotated by the adjustment screw 1.02 connected to the moving stage 101.
Moving the moving stage 101 forward and backward along the sliding surface of 03,
Means for moving the imaging lens system 2, and as shown in FIG. 3B, the imaging lens system 2.

The holding table 110 is clamped and fixed by the vertical reference surface 111 and the leaf spring 112, and a washer 113 is interposed between the reference surface 111 and the imaging lens system 2, and the washer 113 can be removed or additionally inserted. A means has been proposed in which the image lens system 2 is movable in the direction of the optical axis C, and according to this technical means, the deviation (ΔS) between the image forming position on the generatrix line and the actual image forming position can be accommodated. Length ΔS/β,
By moving the imaging lens system 2 in the direction of the optical axis C by β: imaging magnification), the imaging position shift is corrected, and an optimal image can be obtained.

"The problem that the invention attempts to solve" However, in the former case, screws 102 are used.

In order to configure the imaging lens system 2 to be movable, a screw 10 is used.
It is difficult to make fine adjustments due to the backlash of 2 itself, and the latter has the disadvantage that it is impossible to continuously correct the amount of movement because the washer 113 is used to adjust the movement. /+0Il+! It is not suitable as a correction means that requires fine adjustment of one unit.

In addition, in the latter technical means, when the washer 113 is inserted and removed, the force of the plate spring 112 changes or loosens, and the variation in the pressing force causes uneven load and play in the imaging lens system 2. This tends to occur, and it may be difficult to move in the direction of the optical axis C while maintaining the perpendicularity between the exit surface of the lens system 2 and the optical axis C.

Furthermore, even in the former technical means, parallel movement of the imaging lens system 2 may become difficult due to the fixed table 103, the movable stage 101, and the accumulation of images on the movable stage 101.

In addition, in the former technical means, since it is necessary to arrange an adjustment screw 102 for moving the imaging lens system 2 in the exit direction or the entrance direction of the imaging lens system 2, that part inevitably becomes a dead space. , leading to an increase in the size of the device.

Note that due to the characteristics of a laser beam, a beam waist inevitably occurs at its focal position, and the width (2ω) of the beam waist is determined by the focal pressure gi (
f).

ω=(input/πW) f 2W: Beam parallel incidence width, entrance: wavelength Therefore, as in this prior art, the imaging lens system 2 is aligned with the optical axis C.
In the configuration in which the imaging lens system 2 moves in the direction, the imaging spot area on the recording medium 5 also changes in response to the movement of the imaging lens system 2, resulting in a thick or thin line image being formed.

In view of the drawbacks of the prior art, the present invention corrects the amount of deviation of the image formation position on the recording medium 5 caused by processing errors and assembly errors of the light source and various lens systems by fine adjustment and continuous correction. The object of the present invention is to provide an optical scanning device that is configured to be able to perform the following steps.

Another object of the present invention is to provide an optical scanning device that can appropriately select the amount of correction per unit in accordance with the imaging magnification β.

A further object of the present invention is to provide an optical scanning device with extremely high reproducibility, in which the amount of correction does not vary even when correction is repeated.

A further object of the present invention is to provide an optical scanning device that has a small number of parts and can easily be provided with a correction mechanism that has little room for assembly errors.

Another object of the present invention is to provide an optical scanning device that can obtain a uniform line image as a result of almost no change in the imaging spot area on the photoreceptor even when the above correction is performed. shall be.

"Means for Solving the Problems" In order to achieve the above technical problems, the present invention provides a plano-convex cylindrical lens 21 or other components constituting the imaging lens system 2, as shown in FIGS. It has a rotating means for rotating the focusing lens 21 in the sub-scanning direction, and the deviation in the sub-scanning direction between the apex position of the lens entrance surface and the optical axis C that occurs when the lens 21 is rotated is calculated as a minute deviation amount. In order to suppress this, we propose a technical means in which the rotation center A is formed at a predetermined position on the exit surface 2IA side of the lens 21 from a position near the apex of the entrance surface.

In this case, the rotation center A does not necessarily have to be located on the optical axis C;
It may be set at the top or bottom.

"Action" According to this technical means, the plano-convex cylindrical lens 2
1 By rotating the other focusing l/lens in the sub-scanning direction, the imaging position S° is aligned with the recording medium 5 along the optical axis C.
As a result, the image formation deviation of the recording medium 5 is corrected.

Optimal images can be obtained.

In this case, if the cylindrical lens 21 is disposed at a position perpendicular to the optical axis C, the image forming position S'' will be aligned with the recording medium 5 when the cylindrical lens 21 is rotated in either direction. For example, depending on manufacturing tolerances of cylindrical lenses, the lens may be placed upright on the optical axis C and then rotated to match the short focal length of the lens.
Furthermore, if the cylindrical lens 21 is tilted at a predetermined angle and arranged in advance, the imaging position S° will move in a direction away from the recording medium 5 until it reaches a position perpendicular to the tilt angle position. Beyond the right angle position, there is a back that is configured to move close to each other.

In addition, in the present technical means, the plano-convex cylindrical lens 2
Rather than moving the entire lens forward and backward in the optical axis direction, it is sufficient to simply rotate it in the sub-scanning direction, so it is necessary to repeatedly rotate the lens using the large slope side or the center of rotation as a support surface (support point). As a result, even though the support position is stable even if the rotation is repeated, the amount of correction is small. Continuous adjustment is easy and the number of parts is small.
Furthermore, there is less room for assembly errors.

Furthermore, in the configuration in which correction is performed by rotation, since the focal pressure a (f) of the laser beam hardly changes, the width of the beam waist (2ω), that is, the area of the imaged spot on the recording medium 5 is also virtually ignored. It is as small as possible, and a uniform line image can be formed.

In addition, this technical means sets the rotation center A position to the output surface 21A.
In addition, the configuration is such that the deviation in the sub-scanning direction between the apex position of the lens entrance surface and the optical axis C that occurs when the lens 21 rotates is suppressed to zero or to a minute deviation amount.

The reason for this is that since the main surface of the plano-convex cylindrical lens 21 coincides with the apex of the front surface of curvature, the sub-scanning direction between the apex position of the lens entrance surface and the optical axis C that occurs when the lens 21 rotates. If the deviation can be suppressed to zero or to a minute deviation, there will be no linear contact with the deflection surface.

Further, the amount of correction is determined by the inclination angle of the exit surface 2IA side of the plano-convex cylindrical lens 21, and therefore, as shown in FIGS. (Fig. 1a), exit surface 2LA
Assuming that they are set on the optical axis C of the side (Fig. 1b) and at the lower end position of the exit surface 21A side of the lens (Fig. 1c),
In the order of Fig. 1a, Fig. 1b, and Fig. 1C, each correction amount becomes larger due to a slight rotation, and in all cases the lens 2
The deviation in the sub-scanning direction between the apex position of the lens entrance surface and the optical axis C that occurs during one rotation can be suppressed to zero or to a minute deviation amount.

Therefore, by determining the rotation center A position in accordance with the imaging magnification β, the correction amount per unit can be appropriately selected.

Incidentally, astigmatism occurs due to the rotation of the cylindrical lens 21, but since the light beam incident on the plano-concave cylindrical lens 21 is very small in the optical scanning device, the astigmatism generated in the lens is generated on the generatrix. It does not appear as a distortion of the spot image, and there is no problem in practical use.

"Embodiments" Hereinafter, preferred embodiments of the present invention will be described in detail by way of example with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in this example are not intended to limit the scope of this invention, but are merely illustrative examples. It's nothing more than that.

5 and 6 show an optical scanning device according to an embodiment of the present invention. Reference numeral 51 denotes a housing with an upper cover 52 that can be opened and closed, and a rotating polygon mirror 53 on a bottom surface 51a of the housing 51.
The side of the mounting position is turned inward, and the partition wall 51b and the side wall 51
A mounting path 51d for the semiconductor laser 54 etc. sandwiched between c.
form.

A housing 54 housing a semiconductor laser and a collimating lens and a cylindrical lens unit 20 are disposed in the mounting passage 51d in order from the open end side, and are rotated at a predetermined angle via a reflection mirror 56 disposed on the exit side of the semiconductor laser d. polygon mirror 5
The beam is made incident on the deflection surface 53a of No. 3.

A synchronous motor 57 is connected to the rotating polygon mirror 53, and while rotating in synchronization with the photoreceptor drum 58, it sweeps the scanning beam lO incident on the deflection surface 53a in the main scanning direction and converts fθ
The light is made incident on the lens 59.

The swept scanning beam 10 is converted from constant angular velocity motion to uniform velocity motion by the fθ lens 5θ, and then the first and second deflection mirrors 82 attached to the side plate 61 of the housing 51 and the upper cover 52 ．． The photosensitive drum 58 located below the optical axis C of the toroidal lens 64 is made incident on a toric lens such as a toroidal lens 64 or a cylindrical lens through E13, and after correcting the inclination of the rotating polygon mirror 53 in the sub-scanning direction. The image is scanned on the generatrix of .

On the other hand, a detection mirror 65 is disposed on the starting end side of the beam scanning area on the output side of the fθ lens 58, and is deflected by the front 65 and guided to a photodiode 66. The emission timing of the scanning beam 1o from the semiconductor laser is controlled based on the signal.

The scanning beam 10 of the semiconductor laser emitted based on the horizontal synchronization signal is repeatedly scanned on the photosensitive drum 58 generatrix in the manner described above.
By rotating the polygon mirror 53 in the sub-scanning direction in synchronization with the rotation of the rotating polygon mirror 53, a clear image corresponding to the input information on the photoreceptor drum 58 is formed without causing jitter or the like.

4A and 4B show the configuration of the cylindrical lens unit 20 used in the optical scanning device, which includes an outer frame 23 fixed to the housing 51, and a sub-frame fitted into the cylindrical cavity 231 of the outer frame 23. A lens fixing frame 24 rotatable in the scanning direction, a plano-convex cylindrical lens 21 mounted on an L-shaped reference surface 241 of the fixing frame 24, and the lens 2
1 is rotated together with the fixed frame 24 to open the opening 233, and at the same time, a long hole 234 extending along the sub-scanning direction is bored on the diagonally upward exit side of the hole 233, and the radius of curvature is the same as that of the outer peripheral surface of the lens fixed frame 24. A cylindrical cavity 231 is formed.

The lens fixing frame 24 has a substantially semi-cylindrical shape, and has an L-shaped reference surface 2 on which the cylindrical lens 21 can be positioned at a predetermined position.
41 and a screw hole 242 into which the adjustment screw 25 is screwed.
and has.

The cylindrical lens 21 has a vertical plane on the exit surface 21A side, and is fixed in contact with the L-shaped reference surface 241 of the lens fixing frame 24.

The head 251 of the adjustment screw 25 is inserted into the elongated hole 23 of the outer frame 23.
4, and can be fixed in a predetermined position by a set screw 26 at any point within the extending angle α range of the elongated hole 234, and by rotation of the adjustment screw 25, the lens fixing frame 24 and the cylindrical lens 21 are fixed. It can be rotated integrally in the sub-scanning direction.

According to this embodiment, the adjustment screw 25 is inserted into the elongated hole 234.
By rotating the cylindrical lens 21 along the sub-scanning direction, the cylindrical lens 21 can be easily rotated in the sub-scanning direction without causing a rotational error even with repeated operations, and the effects of the present invention can be smoothly achieved. .

Further, the amount of correction by the adjusting screw 25 can be freely determined by the extension angle α of the elongated hole 234.

"Effects of the Invention" As described above, the present invention is capable of correcting the amount of deviation of the image formation position on the recording medium caused by processing errors and assembly errors of the light source and various lens systems by WL adjustment and continuous correction. Therefore, the clarity of the imaged spot formed on the generatrix of the recording medium can be further improved.

Further, according to the present invention, by appropriately determining the rotation center position of the cylindrical lens or other focusing lens in accordance with the imaging magnification β of the optical scanning device, the amount of correction per unit can be freely determined, and as a result, maintenance can be reduced. This makes it possible to make it easier.

Further, according to the present invention, it is possible to provide an optical scanning device with a high rotation speed of a cylindrical lens.

Furthermore, since the present invention has fewer parts and less room for assembly errors, it is possible to reduce manufacturing costs and maintenance costs.

Furthermore, in the present invention, since the focal length of the cylindrical lens does not change even if the correction is performed, the change in the imaging spot area on the photoreceptor is minute, and as a result, a uniform line image is obtained. I can do things. It has the same effect as the above.

[Brief explanation of drawings]

1A to 1C are operational diagrams illustrating in detail the present invention in which the rotational center position of the focusing lens is changed respectively.

Claims (1)

[Claims] In an optical scanning device having an imaging lens system that makes a laser beam oscillated from a light source enter a deflector as linear focused light, the focusing lens constituting the imaging lens system is configured to be rotatable in a sub-scanning direction. At the same time, in order to suppress the deviation in the sub-scanning direction between the apex position of the lens entrance surface and the optical axis that occurs when the lens rotates, to a minute deviation, the center of rotation is set to exit from the apex position of the entrance surface of the lens. An optical scanning device characterized by being formed at a predetermined position on the surface side.