JP2001013004A - Device for measuring diameter of light spot of scanning optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-spot diameter measuring device in which measuring time is shortened and automation and accuracy are improved in measuring a scanning optical system. SOLUTION: This device comprises and optical sensor 6 for measurement to receive a laser luminous flux as a light spot capable of scanning by he rotary polygon mirror 4 of a scanning optical system 1, optical sensor displacement means 7 and 12 to displace the light receiving surface 6a of the optical sensor 6 to a desired point of measurement with respect to a surface to be scanned, a light spot location displacement means comprised by rotation-freely connecting the rotary polygon mirror 4 to a stepping motor 9 by a clamp-shaped member 16 capable of sandwiching two corner parts or more of the rotary polygon mirror 4, and a control means 11 to control the optical sensor displacement means 7 and 12 and the light spot location displacement means on the basis of a light reception signal of the optical sensor 6 and to compute the diameter of the light spot, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of condensing a light beam from a scanning optical system for performing laser scanning with a rotary polygon mirror as a light spot on a surface to be scanned, at a desired main scanning position on the surface to be scanned. The present invention relates to an apparatus for measuring a light spot diameter and the like.

[0002]

2. Description of the Related Art A scanning optical system for converging a laser beam as a light spot on a surface to be scanned and scanning the surface to be scanned is widely known for various image forming apparatuses such as laser printers and digital copying machines. Recently, “higher density and multi-beam scanning” by a scanning optical system are intended, and higher precision and automation are required for measuring the light spot diameter.

The light spot moves on the surface to be scanned and scans the surface to be scanned. The ideal movement direction of the light spot on the surface to be scanned is called a main scanning direction, and the light spot moves in the main scanning direction on the surface to be scanned. It is well known that the direction orthogonal to is called the sub-scanning direction. The “scanned surface” here is a virtual plane, and is actually a photosensitive surface of a photoconductive photoconductor. The movement locus of the light spot is called a “main scanning line”. The light spot diameter depends on the characteristics of the lens that composes the scanning optical system.
It cannot be constant over all of the main scan lines. Therefore, it is common practice to divide the main scanning line into several points and measure the light spot diameter at each point.

[0004]

Incidentally, the measurement of the light spot diameter is performed while the beam is stationary. Therefore, in the case of a scanning optical system that scans a beam using a rotating polygon mirror, the rotating polygon mirror must be stopped at an accurate position in order to accurately focus the light spot on a desired main scanning position on the surface to be scanned. Need to be done.

[0005] However, the rotary polygon mirror is usually directly connected to the motor, and is configured to rotate at high speed at tens of thousands of rpm, and does not have a function of stopping at an accurate position. Conventionally, the rotating polygon mirror was manually rotated while checking the beam position and stopped at a target position, so that it took a long time for measurement and the stop position accuracy of the rotating polygon mirror varied greatly. The present invention has been conceived in order to solve the above-described problems, and has as its object to provide a light spot diameter measuring apparatus for a scanning optical system that has reduced measurement time, automated measurement, and improved measurement accuracy. And

[0006]

In order to achieve the above object, a light spot diameter measuring apparatus for a scanning optical system according to the present invention is capable of scanning by a scanning optical system rotatably supporting a regular polygonal rotary polygon mirror. An apparatus for condensing a laser beam as a light spot on a surface to be scanned, and measuring a light spot diameter at a desired main scanning position on the surface to be scanned, and a measurement optical sensor for receiving the light spot. An optical sensor displacing means for displacing the light receiving surface of the optical sensor to the vicinity of a measurement surface equivalent to the surface to be scanned; and a driving source for driving the rotary polygon mirror by sandwiching a regular prism-shaped corner of the rotary polygon mirror. A light spot position displacement means for rotatably connecting the light spot position to an arbitrary position on the surface to be scanned and stopping the light spot position; the light sensor displacement means and the light based on a light reception information signal of the light sensor; Spot It is characterized by having a control means for calculating a light spot diameter and the like to control the position displacement means.

[0007] The light spot position displacing means may be configured by connecting the rotary polygon mirror to a drive source by a clamp-shaped member that sandwiches at least one corner of the rotary polygon mirror.

[0008] The clamp-shaped member may have a leaf spring-like elasticity, and may have a configuration in which a holding portion obtained by bending a plate-like end of the clamp at a substantially right angle is in contact with a corner of the rotary polygon mirror.

The above-mentioned clamp-shaped member has a configuration in which a clamping portion facing at least any two vertices on a diagonal line among corners of a rotary polygon mirror having an even number of surfaces, or
Of the corners of the rotating polygonal mirror whose number of faces is odd, it is possible to have a configuration in which a clamping portion facing at least any three vertices is provided, and in each case, a concave portion or a convex portion on the upper surface of the rotating polygonal mirror It is also possible to adopt a configuration having a guide portion that can be fitted.

It is preferable that the clamp-shaped member has a high friction material in contact with a corner of the rotary polygon mirror at a holding portion thereof. In this case, the clamp-shaped member has a rubber material or a high friction material as the high friction material. A configuration having emery can be adopted. Further, the clamp-shaped member may have a configuration in which the holding portion has a groove shape which engages with a corner of the rotary polygon mirror.

The driving source of the light spot position displacement means is
The stepping motor can be configured to be coaxially opposed to the rotary polygon mirror and to be a position-adjustable stepping motor supported outside the scanning optical system.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view schematically showing a measuring unit of the light spot diameter measuring device according to the present embodiment. FIG. 2 shows FIG.
It is a side view of the light spot diameter measuring device of FIG. A scanning optical system unit 1, which is a unit to be measured, includes a semiconductor laser 2,
A collimating lens and a cylindrical lens 3, a rotary polygon mirror 4, an fθ lens 5, and the like are provided.

In the scanning optical system unit 1, a so-called regular prism-shaped rotating polygon mirror 4 having mirror surfaces formed at regular intervals in the circumferential direction thereof is rotatably supported on the scanning optical system unit 1. I have. A laser beam emitted from the semiconductor laser 2 to the rotary polygon mirror 4 is transmitted to the rotary polygon mirror 4 by a collimating lens and a cylindrical lens 3.
Is condensed on the mirror surface of. The laser beam condensed on the rotary polygon mirror 4 is reflected by the mirror surface, passes through the fθ lens 5, and irradiates the light receiving portion 6a of the optical sensor 6 arranged at a position corresponding to the image plane, which is the surface to be measured. I do. As the optical sensor 6, a slit scanning method or an area CCD method can be used.

The apparatus of this embodiment for measuring the diameter of a light spot imaged on the surface to be measured from the scanning optical system unit 1 includes an optical sensor 6 and moving stages 7, 8, 1 of the optical sensor 6.
2. A stepping motor 9 as a driving source connected to the rotary polygon mirror 4, and a control means including a controller 10 and a personal computer 11 for controlling the stepping motor 9 and the moving stages 7, 8, 12, etc. Have been.

The optical sensor 6 can be moved by the X stage 7 in the main scanning area (X direction area in the figure) of the laser beam and can be displaced to an arbitrary image height. Similarly, the optical sensor 6 can be moved in the Y direction in the figure by the Y stage 8, and can be set on a scanned surface imagined as a measurement plane.

Further, as shown in FIG.
The stage 12 causes the sub-scanning direction Z on the surface to be scanned.
(A direction perpendicular to the main scanning direction X). And
The Z stage 12 plus the X stage 7 and the Y stage 8 can be displaced to a position required for measurement by three types of moving stages. The optical sensor 6 is connected to the personal computer 1 via the controller 10.
1 connected. The control of the personal computer 11 and the like controls the driving of the rotary polygon mirror 4 via the stepping motor 9 with respect to the optical sensor 6, thereby displacing the position of the light spot focused on the surface to be measured. Can be done.

In the actual measurement, a plurality of measurement points are appropriately selected from the entire main scanning line, and the measurement is performed with these measurement points as "desired main scanning positions". The laser beam reflected by the rotating polygon mirror 4 at this desired main scanning position is imaged as a light spot substantially at the center of the light receiving section 6a of the optical sensor 6. For this purpose, the X stage 7, the Y stage 8, and the Z stage 12 are driven and controlled based on the light reception information signal of the optical sensor 6, and the rotating polygon mirror 4 is rotated and stopped by the stepping motor 9, thereby controlling The light receiving position can be adjusted accurately. Then, the output from the optical sensor 6 is taken into the personal computer 11 via the controller 10. The personal computer 11 can calculate the light spot diameter, the center position of the light spot, and the like based on the output from the light sensor 6 by its calculation function.

As shown in FIG. 2, the scanning optical system unit 1 having the above-mentioned structure is fixed on a dedicated table 13, and an independent stepping motor separate from the scanning optical system unit 1 is provided above the rotary polygon mirror 4. 9 is disposed, and the stepping motor 9
Is connected to the rotary polygon mirror 4. The stepping motor 9 is attached to the tip of the arm 14, and the amount of protrusion and the height of the arm 14 can be adjusted by the stand 19. Thus, the drive shaft 9a of the stepping motor 9 positioned by the arm 14 from the outside of the scanning optical system unit 1 is substantially coaxial with the rotation axis of the rotary polygon mirror 4, and is positioned so as to face the rotary polygon mirror 4. ing.

FIG. 3 to FIG. 5 are perspective views of the connecting portion between the rotary polygon mirror 4 and the clamp-shaped member 16. Hereinafter, some embodiments of the configuration of the coupling unit will be described. FIG. 3 shows a first embodiment of the clamp-shaped member 16. The stepping motor 9 and the rotary polygon mirror 4 are connected by a coupling 15 and a clamp-shaped member 16 without play. The clamp-shaped member 16 can be constituted by a leaf spring or the like. In the clamp-shaped member 16 illustrated in FIG. And a shaft portion 16b connectable to the coupling 15 at a central position thereof. As shown by arrows in FIG. 3, the two holding portions 16a have a leaf spring-like elasticity centering on the shaft portion 16b, and the inner surface of each holding portion 16a is a side mirror of the rotary polygon mirror 4. The rotary polygon mirror 4 is held in a state in which the driving of the stepping motor 9 can be transmitted so as to abut against the corner portion 4a therebetween.

Further, the rotary polygon mirror 4 of the first embodiment is
Because of the surface configuration, two apexes (corners 4a) facing each other so as to sandwich the axis center can be sandwiched by the clamp-shaped member 16, so that they can be easily joined without play. By driving the stepping motor 9 in this state, the drive is transmitted to the rotary polygon mirror 4 and the light spot position is displaced, so that the rotary polygon mirror 4 can be driven with the same resolution as the resolution of the stepping motor 9 and can be moved to the desired main scanning position. It is possible to set a light spot. If the number of surfaces of the rotary polygon mirror 4 is an even number as described above, there is always one pair or more of two vertices in the regular prism shape. It is possible.

The clamp-shaped member 16 is a rigid plate-shaped member, but has a thickness such that it has elasticity in the vertical direction (almost right and left in the holding portion 16a). That is, since the rigidity is extremely high in the rotational direction, no bending which causes backlash or the like occurs in the rotational direction. According to the configuration in which the clamp-shaped member 16 coupled to the driving source sandwiches and connects the rotary polygon mirror 4, the rotary polygon mirror 4 can be easily held and the rotary polygon mirror 4 can be easily held.
Can be accurately controlled.

FIG. 4 shows a second embodiment of the clamp-shaped member 16. The rotary polygon mirror 4 of the second embodiment has a configuration of five surfaces, and there is no opposing vertex unlike the case of the even surface. For this reason, three suitable vertices are clamped by the clamp-shaped member 16 and connected without play. As described above, if the number of faces of the rotary polygon mirror 4 is an odd number, reliable coupling can be achieved by selecting three vertices. However, even if the number of surfaces is odd, a configuration in which only two vertices are sandwiched by the following method can be adopted.

FIG. 5 shows a third embodiment of the clamp-shaped member 16. The rotary polygon mirror 4 of the third embodiment also has a configuration of five surfaces, and the coupling method with three vertices can be performed as described above. Any part of the holding portion 16a necessarily covers any side surface. For this reason, when the laser beam is reflected at the end of the mirror surface, there is a possibility that the laser beam is damaged. Further, if only the two vertices are simply clamped, it is difficult to join the rotary polygon mirror 4 and the clamp-shaped member 16 without play even if the core is slightly displaced.

Therefore, in general, the rotary polygon mirror 4 often has a hole or a projection at the center thereof, and can be used as a projection or a recess for preventing misalignment. For example, in the third embodiment shown in FIG. 5, the rotary polygon mirror 4 has a hole 4b in the rotary shaft portion. A shaft member 16c as a guide portion that can be fitted into the hole 4b is provided on the clamp-shaped member 16. Then, the shaft member 16c of the clamp-shaped member 16 is inserted into the hole 4b of the rotary polygon mirror 4, and the two vertices of the corner 4a are clamped by the two clamping portions 16a using this as a fulcrum. If such a hole 4b of the rotary polygon mirror 4 is used,
The number of holding portions can be reduced, and the connection can be made without play. Of course, in the case of a rotary polygonal mirror having a configuration in which the shaft shape protrudes from the hole 4b without the hole 4b, a hole that can be fitted thereto is formed at the center of the clamp-shaped member 16 and the hole of the clamp-shaped member 16 is formed. It is preferable to adopt a configuration in which the shaft shape of the rotary polygon mirror is inserted.

The rotary polygon mirror 4 is generally made of a metal such as aluminum, and has a sharp apex. Slipping may occur due to the flat holding portion 16a. Therefore, it is desirable to provide a non-slip on each of the holding portions 16a.

FIG. 6 is a perspective view of the clamp-like member 16 having rubber as a high friction material in the holding portion 16a. A rubber plate 17 or the like is fixed to the inner surface of each of the holding portions 16a by bonding or the like to prevent slippage of the rotating polygon mirror 4 with respect to the apex.

FIG. 7 is a perspective view of the clamp member 16 having an emery 18 as a high friction material in the holding portion 16a.
As a high friction material, in addition to rubber, Emery 18 (Emer
y), that is, a file-like thing made of an abrasive or the like can be used. In particular, when an elastic member that is easily deformed, such as the rubber, is used, the rotation of the stepping motor 9 is not accurately transmitted due to its bending, and there is a possibility that a backlash may occur at the time of reverse rotation. Therefore, by providing a high friction material such as emery which is not easily deformed, slip and backlash can be prevented.

FIG. 8 is a perspective view of the clamp-shaped member 16 in which the groove 16d is formed in the holding portion 16a. If a high friction material such as emery is used for the holding portion 16a, slippage and backlash can be prevented, but in this case, the reflection surface of the rotary polygon mirror 4 may be damaged due to an operation error.

Therefore, in this example, the groove 16d is formed directly in the holding portion 16a. A groove 16d engageable with the corner 4a of the rotary polygonal mirror 4 is formed in each of the rigid holding portions 16a, and the top and bottom of the rotary polygonal mirror 4 are pressed to slide and back. The rush is prevented, and the reflective surface of the rotary polygon mirror 4 is not damaged.

[0030]

As described above, according to the light spot diameter measuring apparatus of the present invention, the rotary polygon mirror can be connected to its driving source without any play without any processing. Compared with a conventional device that determines the position of a rotary polygon mirror by work or the like, measurement time is reduced, measurement can be automated, and measurement accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic configuration of an embodiment of a light spot diameter measuring apparatus according to the present invention.

FIG. 2 is a side view of the light spot diameter measuring device of FIG.

FIG. 3 is a perspective view showing a first embodiment of the clamp-shaped member according to the present invention.

FIG. 4 is a perspective view showing a second embodiment of the clamp-shaped member according to the present invention.

FIG. 5 is a perspective view showing a third embodiment of the clamp-shaped member according to the present invention.

FIG. 6 is a perspective view of a clamp-shaped member having rubber in a holding portion.

FIG. 7 is a perspective view of a clamp-shaped member having emery in a holding portion.

FIG. 8 is a perspective view of a clamp-shaped member having a groove shape in a holding portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanning optical system 4 Rotating polygon mirror 4a Corner 4b Convex part or concave part 6 Optical sensor 6a Sensor light receiving surface 7, 8, 12 Optical sensor displacement means 9 Drive source, stepping motor 10, 11 Control means 16 Clamp-shaped member 16a Nipping Part 16c Guide part 16d Groove shape 17, 18 High friction material, rubber material, emery

Claims (11)

[Claims] 1. A laser beam that can be scanned by a scanning optical system rotatably supporting a regular polygonal rotary polygon mirror is focused as a light spot on a surface to be scanned, and a desired main scanning on the surface to be scanned is performed. An apparatus for measuring a light spot diameter at a position, comprising: an optical sensor for measurement for receiving the light spot; and an optical sensor displacing means for displacing a light receiving surface of the optical sensor to a vicinity of a measurement surface equivalent to a surface to be scanned. And the rotary polygon mirror is rotatably connected to a driving source by sandwiching a regular prism-shaped corner of the rotary polygon mirror, and the light spot position is displaced to an arbitrary position on the surface to be scanned and stopped. Light spot position displacing means, and control means for controlling the light sensor displacing means and the light spot position displacing means based on the light receiving information signal of the optical sensor and calculating a light spot diameter and the like. Light spot diameter measuring apparatus of the scanning optical system according to symptoms. 2. The light spot position displacing means is configured by connecting the rotary polygon mirror to a drive source by a clamp-shaped member that sandwiches at least one corner of the rotary polygon mirror. An optical spot diameter measuring device for a scanning optical system according to claim 1. 3. The clamp-shaped member is characterized in that it has a leaf spring-like elasticity, and a clamping portion having its plate-like end bent at a substantially right angle is brought into contact with a corner of the rotary polygon mirror. 3. The optical spot diameter measuring device for a scanning optical system according to claim 1, wherein 4. The clamping member according to claim 1, further comprising a clamping portion facing at least any two vertices on a diagonal line among corners of the rotating polygon mirror having an even number of surfaces. 4. The optical spot diameter measuring device for a scanning optical system according to any one of items 1 to 3. 5. The clamp-shaped member has at least one of three corners of a rotating polygonal mirror having an odd number of surfaces.
The optical spot diameter measuring device for a scanning optical system according to claim 1, further comprising a holding portion facing the vertex. 6. The scanning optical system according to claim 1, wherein the clamp-shaped member has a guide portion that can be fitted to a concave portion or a convex portion on the upper surface of the rotary polygon mirror. Light spot diameter measuring device. 7. The scanning optical system according to claim 1, wherein said clamp-shaped member has a high friction material in contact with a corner of said rotary polygon mirror at a holding portion thereof. Light spot diameter measuring device. 8. The optical spot diameter measuring device for a scanning optical system according to claim 7, wherein said clamp-shaped member has a rubber material in a holding portion thereof. 9. The optical spot diameter measuring apparatus for a scanning optical system according to claim 7, wherein said clamp-shaped member has an emery at a holding portion thereof. 10. The scanning optical system according to claim 1, wherein said clamp-shaped member has a groove shape at its holding portion to engage with a corner of said rotary polygon mirror. Light spot diameter measuring device. 11. A driving source for the light spot position displacing means is disposed coaxially with the rotary polygon mirror and opposed to the rotary polygon mirror.
2. A stepping motor which is supported outside the scanning optical system and whose position is adjustable.
0. A light spot diameter measuring device for a scanning optical system according to any one of 0 to 1.