JPH0425810A - Lens position adjusting device - Google Patents

Abstract

PURPOSE:To easily attain a desired lens adjustment in a short time without any special knowhow by providing a lambda/4 plate, a polarization beam splitter, and a detector part on an optical path from a light source part which has a collimation optical system. CONSTITUTION:The cylindrical lens 2 to be adjusted has its plane to be adhered with the cut surface 12-1 of a lens holder 2 and has its optical axis aligned with an X axis, and the reference surface 13 in machining is parallel to the generating line of the lens. A scanning optical system and the lens adjusting device 100 are fixed on an adjusting jig and luminous flux from a light source part 7 passes through the polarization beam splitter 8 and lambda/4 plate 9, reflected by the surface 13 of the lens 2, and passes through the plate 9 again, and the light is changed in travel direction by 90 deg. through the splitter 8 and detected by the detector part 10. If the lens 2 is eccentric at this time, the luminous flux is deviated and does not reach the detector part 10, so the holder 12 is rotated to make the adjustment so that the light reaches the detector part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a lens position adjustment device used for an optical system having an anamorphic lens, and more specifically, it is applied to an optical scanning device of a laser beam printer. The present invention relates to a lens position adjustment device.

(Prior Art) Anamorphic lenses such as cylindrical lenses have various uses.

For example, in laser-based equipment such as laser beam printers, a cylindrical lens is sometimes used to correct the shape of a laser beam from a semiconductor laser. If the laser beam is not sufficiently compensated,
A situation arises in which the shape of the spot of the irradiated laser beam is not circular.

Further, in an optical scanning device installed in a laser beam printer or the like, a cylindrical lens is also used to correct errors caused by tilting of each reflective surface of a polygon mirror for scanning a laser beam.

When such a situation occurs, there is a risk that image deterioration may occur in a recording device such as a laser beam printer.

In other words, the power of a cylindrical lens is directional, so when installing it around the tip axis, the position is Igi!
need to be adjusted.

In this case, in order to linearly converge the laser beam onto the reflective surface of the polygon mirror, the direction of the generatrix of the cylindrical lens and the laser beam after being reflected by the reflective surface must be parallelized again. The direction of the generatrix of the cylindrical lens for rubbing (a toroidal lens is also used in some cases) must match.

If they do not match, the laser beam will be distorted and imaged on the surface to be scanned, such as a photoreceptor.

In addition, cylindrical lenses can also be used for the lasers mentioned above.
When used to correct the inclination of the reflective surface of a polygon mirror in a beam printer, the laser beam must be focused near the reflective surface of the polygon mirror. To do this, a cylindrical lens must be positioned in the optical axis direction. There is a need.

Conventionally, the following techniques are known as means for adjusting the lens position.

(a) A device in which the position of an adjusted body is adjusted using a conical surface attached to the tip of a screw member and a motion transmission member (see Japanese Utility Model Publication No. 173210/1983).

(b) A lens holder is attached to a holding substrate, and an eccentric pin is used to move the lens holder to adjust the lens (see Japanese Patent Laid-Open No. 1-96612).

(c) Piezoelectric elements are arranged on all sides of the lens, and the position of the lens is adjusted by applying a charge to the piezoelectric element using a spot image when the inspection beam passes through the lens (Japanese Unexamined Patent Publication No. 180313/1983). (see official bulletin).

(Problem to be Solved by the Invention) In an optical system using an anamorphic lens, particularly precise and subtle adjustment of the lens position is desired due to the lens characteristics.

However, in the prior art described above, it is up to the adjuster's experience how to operate these adjusting means in order to obtain the desired adjusted state.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lens position adjustment device that can easily and quickly obtain a desired lens adjustment state without requiring special know-how.

(Means for Solving the Problem) In order to achieve the above object, the lens position mli of the present invention is
The device includes a light source and a light source section having a collimating optical system that collimates the light beam emitted from the light source;
A λ/4 plate provided on the optical path of the light emitted from the light source, a polarizing beam splitter disposed between the λ/4 plate and the light source, and a light beam from the polarizing beam splitter. The detector is equipped with a detector section that detects the

(Function) When the lens is in the correct adjustment position, the light beam from the polarizing beam splitter is detected by the detector section.

(Example) First, in FIG. 5, which describes a scanning optical system to which the present invention is applied, reference numeral 1 indicates a light source or a light source device consisting of a light source and a collimating section.

The light beam emitted from this light source device 1 is transmitted through an anamorphic lens, for example, a cylindrical lens having a linear imaging function.
The light is made incident on lens 2. Further, the deflector 3 is arranged so that the deflection reflection surface 3a is located near the position where the light beam is converged into the linear image LI by this cylindrical lens.

Further, fθ lenses 4 and 5, which are a second imaging optical system, are arranged between the deflector 3 and the scanned medium 6.

During scanning, these composition systems combine the scanned medium 6 with
An imaged spot is formed on the medium 6 to be scanned, and this imaged spot is scanned onto the scanned medium 6 by rotating the deflector 3.

Next, according to FIG. 2, the lens adjustment device 10 according to the present invention
An overview of 0 will be explained. Reference numeral 7 designates a light source section that includes a light source for adjusting the cylindrical lens 2 and a collimating lens that converts the laser beam oscillated from this light source into a parallel beam.

A λ/4 plate 9 is provided on the optical path of the light emitted from the light source section 7, and a polarizing beam splitter 8 is further disposed between the λ/4 plate 9 and the light source section 7. In the direction in which the light beam is reflected by the polarizing beam splitter 8, a detector section 1o for detecting the polarized light beam is located.

When adjusting the lens, the light beam emitted from the light source section 7 enters the polarizing beam splitter 8, and the polarizing beam splitter 8 is arranged so that the polarization state at this time becomes P polarized light. Approximately 100% of the light beam incident on the polarizing beam splitter 8 passes through and enters the λ/4 plate 9.

The λ/4 plate 9 changes the light beam from linearly polarized light to circularly polarized light.

The light beam emitted from the λ/4 plate 9 hits the cylindrical lens 2 to be adjusted, is reflected, enters the λ/4 plate 9 again, and becomes linearly polarized light again. The light beam passing through the λ/4 plate 9 becomes S-polarized light, and approximately 100% of the light beam is reflected in the 90'' direction by the polarizing beam splitter 8 and reaches the detector unit 10.

Here, the attachment of the cylindrical lens 2 will be explained with reference to FIG. The cylindrical lens 2 is attached using a notch at one end of a cylindrical lens holder 12. Note that the central shaft portion of the lens holder 12 is hollowed out for the optical path. This lens holder 12 is rotatably attached to a holding substrate 11 having a hole into which it can fit. It is also provided with means for holding the position after one rotation.

Now, in the scanning optical system shown in FIG. 1, when the optical axis of the light beam traveling from the light source section 1 to the deflector 3 is the X axis, the rotation center axis of the holder 12 within the holding substrate 11 shown in FIG. is aligned with this X axis.

Further, it is assumed that orthogonal #AY and Z axes intersect with the X axis, and the Y axis is taken on the scanning plane of the scanning optical system.

Therefore, the Z axis is perpendicular to the X and Y planes, and these relationships are as shown in FIG.

When adjusting the lens position, the scanning optical system shown in FIG. 1 is placed on an adjustment jig (not shown). The lens adjustment device 100 is also placed on the same adjustment jig. At that time, the light flux for adjustment is Z
It is positioned to align with the axis.

As shown in an enlarged view in FIG. 3, the cylindrical lens 2 to be adjusted is located at
1 with its flat surface in close contact. During this installation, the optical axis of the lens is aligned with the X-axis with as much precision as possible, and the reference plane 13 during processing of the lens is processed to be parallel to the generatrix of the lens.

Under such conditions, a light beam is emitted from the light source section 7. Then, the emitted light beam passes through the polarizing beam splitter 8, λ/
4 passes through the plate 9, and the reference plane 1 of the cylindrical lens 2
3, passes through the λ/4 plate 9 again, and becomes a polarized beam.
The traveling direction of the light is changed by 90 degrees by the splitter 8, and the light reaches the detector section 10, where it is detected.

At this time, as shown in FIG. 4, the cylindrical lens 2 should be in the state shown by the solid line, that is, not decentered with respect to the X-axis (optical axis of the scanning optical system), but should be in the state shown by the broken line, that is, , when the light beam is eccentric with respect to the X axis, it is reflected from the reference surface 13, and λ/
4. It ends up heading in the direction of the arrow 17, which is off the board 9.

In this way, when the lens is eccentric, the light beam does not reach the detector section 10, so the lens holder 12 is rotated. The rotational position of the lens holder when the light beam reaches 1° of the detector section becomes the adjustment position of the lens.

Although the accuracy of adjustment may vary depending on the light detection area of the detector section 10 and the so-called beam diameter of the adjustment light beam, it is possible to improve the accuracy of adjustment by providing a pinhole or the like in front of the light receiving surface of the detector section. It is possible.

By using this method to adjust the cylindrical lens around the optical axis, even people without special adjustment know-how can easily perform the adjustment.

Furthermore, by making the lens holder 12 rotatable about the Y axis, the inclination of the cylindrical lens 2 can be adjusted.

Furthermore, by applying the adjustment light beam not only from the Z-axis direction but also from the Y-axis direction, rotational adjustment of the cylindrical lens 2 with respect to the two axes can be performed.

It is assumed that the cylindrical lens 2 has refractive power only in the xZ plane direction (sub-scanning direction).

(Effects of the Invention) According to the present invention, a desired lens adjustment state can be obtained simply and in a short time without requiring special know-how.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a lens position adjusting device according to the present invention together with a scanning optical system, FIG. 2 is a perspective view of a lens holder,
FIG. 3 is a partially enlarged view of the same figure as above, FIG. 4 is a diagram explaining the process of adjusting the lens position, and FIG. 5 is a perspective view of the scanning optical system including the lens to be adjusted. 7... Light source section, 8... Polarizing beam splitter, 9
...λ/4 plate, 10...detector section. (1 other person) Horse drawing Horse 2 drawing

Claims (1)

[Claims] 1. A light source, a light source section having a collimating optical system that collimates the light beam emitted from the light source, a λ/4 plate provided on the optical path of the light emitted from the light source section, and a λ/4 plate provided on the optical path of the light emitted from the light source section.
A lens position adjustment device comprising: a polarizing beam splitter disposed between the four plates and the light source section; and a detector section detecting a light beam from the polarizing beam splitter.