JPH0258016A - Scanning optical device - Google Patents

Abstract

PURPOSE:To optimize an image formation state at the time of varying in environmental temperature and to facilitate the replacement of a laser element by mounting a solid laser element and a moving means for a beam convergence position on a photosensitive body on the same block. CONSTITUTION:The solid laser element 1 and the slide lens 3 which adjusts the image formation state of laser light on the photosensitive drum 8 are mounted on the same block 13. Further, a reflecting mirror 9 which detects the image formation state on the photosensitive drum 8 and a detecting means 10 such as a CCD camera are arranged at an equal distance to the photosensitive body 8. If the environmental temperature varies, the detection signal of a detecting means 10 which monitors the image formation state on the drum is sent to a control part 11, which moves the slide lens 3 through a stepping motor 5 with a specific signal so that the best image formation state is obtained. When the laser element 1 is replaced, the image formation state is adjusted automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a scanning optical device that scans a laser beam, and in particular detects a focal position shift of an imaging spot of a laser beam on a scanning surface due to environmental changes such as temperature. The present invention relates to a scanning optical device capable of correcting a focal position shift thereof.

C. Prior Art] In a device such as a laser beam printer that records a desired image by scanning a laser beam and blinking the laser beam to form a latent image on a photoreceptor drum, a human-powered image signal is transmitted to the laser beam. The customer control circuit switches and emits laser light from the solid-state laser element at a predetermined timing, and the collimator lens system converts it into a parallel beam of light, which is then horizontally (main scanning direction) sent by a rotating polygon mirror. While being scanned, the fθ lens group
A spot image is formed on the photoreceptor drum at a constant speed.

By scanning the laser beam in this manner, an exposure distribution for one line of the image is formed on the photoreceptor drum, and by scrolling the photoreceptor drum by a predetermined amount perpendicular to the scanning direction for each scan, An exposure distribution corresponding to the image signal can be obtained on the photoreceptor drum. A high-density image can be obtained by printing this latent image on recording paper using a well-known electrophotographic process.

In recent years, there has been a trend to increase the density of the above-mentioned images, and for this purpose, in order to reduce the size of the laser spot irradiated onto the photoreceptor drum, an imaging optical system (
As this value increases, the depth of focus of the imaging optical system becomes shallower. However, in such an imaging optical system, changes in environmental temperature cause thermal deformation of each member constituting the optical system, causing the focal plane to exceed the allowable depth of focus, resulting in the spot diameter not reaching the desired value. It may become larger. As a means to solve this problem, Japanese Unexamined Patent Publication No. 100113/1983 provides a detection means for detecting the image formation state of the laser beam on the photoreceptor drum, and the image formation of the laser beam is based on the signal obtained by this detection means. A scanning optical device that is characterized by position adjustment has been proposed.

Incidentally, in a scanning optical device, a solid-state laser element, which is a light source, must be replaced due to its lifespan or failure. In other words, during this exchange, if the positional relationship between the solid-state laser element and the lens for correcting focal position deviation deviates from the normal relationship, it will be impossible to correct the focal position deviation. . Furthermore, when replacing the solid-state laser element, it is always necessary to correctly adjust the positions of the solid-state laser element and the lens for correcting focal position deviation.

(Summary of the Invention) An object of the present invention is to provide a scanning optical device that eliminates the drawbacks of the conventional devices and eliminates the need for positional adjustment between the light source and the focal position 8 moving means when replacing the light source. be.

The object of the present invention is to provide a detection means for scanning a light beam from a light source on a scanning surface via a deflector and a lens system, and detecting a convergence state of the light beam on the scanning surface; In a scanning optical device equipped with a focal point positioning means for moving a light beam focusing position by 88 degrees, the light source and a focal position positioning means for moving a light beam focusing position on the scanning surface are mounted on the same block. This is achieved by being present.

(Example) Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 shows a schematic configuration of a scanning optical device according to the present invention. Reference numeral 1 denotes a solid-state laser element that blinks in response to an image signal, and the laser beam emitted from the solid-state laser element 1 passes through a collimator lens 2 and a sliding lens 3, which is a means for moving the imaging position of the laser beam, which will be described later. pass and further
It is reflected by the rotating polygon mirror 5 rotating at a constant speed in the direction of arrow B, passes through fθ lens groups 7a to 7C, and is scanned at a constant speed in the direction of arrow C (main scanning direction).
A latent image is formed on the photosensitive drum 8, which is a scanning surface. 9 and 10 are means for detecting the imaging state (focused state) of the laser beam on the photosensitive drum 8, 9 is a reflecting mirror, and 10 is a detection means (for example, a solid-state image sensor such as a CCD camera). ), and the reflecting mirror 9 and the detecting means 10 are arranged so as to be equal in distance to the photosensitive drum 8. Reference numeral 11 denotes a control section that determines the state of the imaging position of the laser beam from the signal detected by the detection means 10 and outputs a control signal to the imaging position (focal position) 9 function means to be described later.

Control signal output from the control section 11 (correction ff1)
Accordingly, in order to slide the sliding lens 3 in the direction of arrow A, a driving device 5 including a motor or the like is driven. 4 is a means for sliding the sliding lens in the direction of arrow A, and is constituted by, for example, a gear transmission mechanism, a feed screw mechanism, or the like. As described above, the sliding lens 3 is slid in the direction of the arrow A by the driving device 5 and the sliding means 4 in accordance with the control signal from the control unit 11, thereby forming an image of the laser beam on the photoreceptor drum 8. Adjust the conditions so that the spot-shaped laser beam is always in the optimal state regardless of environmental temperature fluctuations.

In Figure 1, the part within the 1-dot head line is the optical box, and 2
The portion within the dotted line is a block portion on which the solid-state laser element 1, collimator lens 2, sliding lens 3, and sliding means 4 are mounted. By separating the optical box and the block part, the present invention not only facilitates the replacement of the solid-state laser element 1 due to the lifespan of the solid-state laser element 1 or failure, but also improves the accuracy of assembly during installation. The structure also avoids being influenced by

Hereinafter, the contact portion between the optical box and the block portion will be explained with reference to FIGS. 2 and 3.

FIG. 2 is a diagram showing details of the joint between the optical box and the block, and FIG. 3 is a diagram showing details of the joint on the lower side of the block. 1 is a solid-state laser element, 2 is a collimator lens, 3 is a sliding lens, and 4 is a sliding means, which have already been explained in FIG.
4a is a correction lens support part, 4b is a sliding base, 4C is a sliding shaft, 4d and 4e are transmission gears, and 5 is a drive device, for example, a step motor. . 12 is a sliding part fixing part, 13 is a block, 1
4 is an optical box, 15a and 15b are bottles as positioning members, 16a and 16b are bottle holes, and 17a and 17b are a block-side reference surface and an optical box-side reference surface, respectively.

In the figure, a step motor 5 rotates in accordance with a signal output from a control unit 11 as shown in FIG. is converted into linear motion in the direction. As this sliding table 4a slides, the sliding lens 3 attached thereon slides on the optical axis to adjust the imaging state of the laser beam on the photosensitive drum shaft. Further, in the same figure, the solid-state laser element 1, the collimator lens 2, the sliding lens 3, the sliding means 4, and its fixing part 12 are mounted on a block 13, and the solid-state laser element 1 and the collimator lens 2 are mounted on the block. The optical box 14, which is solidly mounted above the block 13 and the correction lens driving device 5, has two alignment bins 15a, 15.
b and its two paired bottle holes 17a and 17
b, and further three sets of reference surfaces 16a and 16b
The parallelism between the reference plane and the optical axis E is maintained with high precision. Here, the accuracy of mounting the block 13 and the optical box 14 is such that the parallelism of the optical axis E from the reference plane is within 2 minutes and the amount of change in height is within 50 μm. In order to achieve such precision, the positioning bins 15a, 15"b and the reference surface 17a provided on the lower side of the block are
It is configured as shown in the figure.

In the example shown in the above figures, the sliding lens 3 is moved as a means for moving the focusing position of the light beam on the scanning surface, and the CCD is used as a means for detecting the focusing state of the light beam on the scanning surface. However, other known techniques may be used for the means for moving the focused position of the light beam and the means for detecting the focused state of the light beam.

Examples of means for moving the focusing position of the light beam include those that move a convex lens placed between a collimator lens and a rotating polygon mirror, as disclosed in JP-A-60-100113, and those that move a convex lens placed between a collimator lens and a rotating polygon mirror, as disclosed in JP-A-59-116,603. Place the imaging lens on B
Possible methods include a method in which the collimator lens is moved by force, and a method in which the collimator lens is moved as in Japanese Patent Application Laid-Open No. 112123/1983.

Further, as a means for detecting the convergence state of the light beam, a means for detecting the temperature of the lens is disposed near the lens, as disclosed in Japanese Patent Application Laid-open No. 100111/1983, and a means for detecting the temperature of the lens is arranged near the lens, and a signal from the detecting means is used to detect the temperature of the lens. It is also conceivable to detect the focused state of the light beam on the photosensitive drum.

(Effects of the Invention) With the above-described configuration, the present invention allows the image formation state of laser light on the photoreceptor drum to be always in an optimal state regardless of fluctuations in the environmental temperature, and also reduces the lifespan of the solid-state laser element. Replacement can be easily performed without being affected by the accuracy of positional adjustment between the solid-state laser element, which is a light source, and the focal position moving means, which is a problem when replacing due to failure or the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a scanning optical device according to the present invention, and FIG. 2 is a diagram showing a block section in which a solid-state laser element, a collimator lens, a sliding lens, etc. are mounted, and an optical box having an imaging lens, etc. joined together. FIG. 3 is a diagram showing details of the joint on the lower side of the block. 1... Solid-state laser element, 2... Collimator lens,
3...Sliding lens, 4...Correction lens sliding means, 4
a...Correction lens support stand, 4b...Sliding stand, 4C.
...Sliding shaft, 4d, 4e...Transmission gear, 5...Drive device, 6...Rotating polygon mirror, 7a, 7b, 7c...f
θ lens group, 8...photosensitive drum, 9...reflector,
10... Laser light detection means, 11... Control unit, 12
...Sliding part fixing part, 13...Block, 14...
Optical box, 15a, 15b... positioning member (pin,
block side), 16a, 16. b...Positioning member (bottle hole, optical box side), 17a, 17b=reference surface.

Claims (1)

[Claims] (1) Detection means for scanning a light beam from a light source on a scanning surface via a deflector and a lens system and detecting the state of focus of the light beam on the scanning surface, and focusing the light beam on the scanning surface A scanning optical device equipped with a focal position moving means for moving a position, characterized in that the light source and a focal position moving means for moving a light beam focusing position on the scanning surface are mounted on the same block. scanning optical device.