JP4057197B2 - Optical spot diameter measuring device for scanning optical system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention condenses a light beam from a scanning optical system that performs laser scanning with a rotating polygon mirror as a light spot on a surface to be scanned, and measures a light spot diameter or the like at a desired main scanning position on the surface to be scanned. It relates to the device.
[0002]
[Prior art]
A scanning optical system that focuses a laser beam as a light spot on a surface to be scanned and scans the surface to be scanned is widely known for various image forming apparatuses such as a laser printer and a digital copying machine. In recent years, “high density and multi-beam” scanning by a scanning optical system is intended, and higher precision and automation are required for measuring the light spot diameter.
[0003]
The light spot moves on the surface to be scanned and scans the surface to be scanned. The ideal moving direction of the light spot on the surface to be scanned is called the main scanning direction and is orthogonal to the main scanning direction on the surface to be scanned. As is well known, the direction is referred to as a sub-scanning direction. The “scanned surface” referred to here is a virtual plane, and is essentially a photosensitive surface of a photoconductive photoreceptor. The movement trajectory of the light spot is called a “main scanning line”. The light spot diameter cannot be constant over the entire main scanning line due to the characteristics of the lenses constituting the scanning optical system. Therefore, it is common to divide the main scanning line into several points and measure the light spot diameter at each point.
[0004]
[Problems to be solved by the invention]
By the way, the measurement of the light spot diameter is performed with the beam stationary. Therefore, in the case of a scanning optical system that scans a beam using a rotating polygon mirror, the rotating polygon mirror is stopped at an accurate position in order to accurately focus the light spot at a desired main scanning position on the surface to be scanned. It is necessary to let
[0005]
However, the rotating polygon mirror is usually directly connected to the motor, and is configured to rotate at a high speed of tens of thousands of rpm, and does not have a function of stopping at an accurate position. Conventionally, the rotary polygon mirror is manually rotated while confirming the beam position and stopped at the target position, so that measurement takes time and variation in the stop position accuracy of the rotary polygon mirror is large.
Therefore, the present invention has been conceived to solve the above-described problems, and an object thereof is to provide a light spot diameter measuring device for a scanning optical system that shortens measurement time, automates measurement, and improves measurement accuracy. It is said.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an optical spot diameter measuring apparatus for a scanning optical system according to the present invention provides a laser beam that can be scanned by a scanning optical system that rotatably supports a regular prismatic rotary polygon mirror on a surface to be scanned. An apparatus for condensing light as a spot and measuring a light spot diameter at a desired main scanning position on the surface to be scanned, a measuring light sensor for receiving the light spot, and a light receiving surface of the light sensor. An optical sensor displacing means for displacing in the vicinity of a measurement surface equivalent to the scanning surface, and at least one or more corners of the regular prism shape of the rotary polygon mirror are clamped by an elastic leaf spring-like clamp member , A light spot position displacing means for connecting the rotary polygon mirror to the drive source by transmitting a driving force to displace and stop the light spot position at an arbitrary position on the surface to be scanned; Receiving Based on the information signal it is characterized by having a control means for calculating a light spot diameter and the like to control the optical sensor displacement means and the light spot position displacement means.
[0008]
The clamp member may be configured to contact the clamping portion bent substantially at a right angle to end plate wave Ne at the corners of the rotating polygon mirror.
[0009]
The clamp-shaped member has a structure having a clamping portion facing at least any two vertices on the diagonal line among the corners of the rotating polygon mirror having an even number of surfaces, or a rotating polyhedron having an odd number of surfaces. It can be set as the structure which has the clamping part which opposes at least any three vertex among the corner | angular parts of a mirror, and has the guide part which can be fitted with the recessed part or convex part of the said rotating polygon mirror upper surface in each case It can also be.
[0010]
The clamp-shaped member may be configured to have a friction material that contacts a corner portion of the rotary polygon mirror and prevents slippage with the rotary polygon mirror . In this case, the clamp-shaped member is it can be as the friction Kosuzai configured to have a rubber material or Emery. Moreover, the said clamp-shaped member is good also as a structure which has the groove shape engaged with the corner | angular part of the said rotary polygon mirror in the clamping part.
[0011]
The drive source of the light spot position displacing means is arranged to be coaxially opposed to the rotary polygon mirror, and can be configured as a position adjustable stepping motor supported outside the scanning optical system. .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a plan view illustrating an outline of a measurement unit of the light spot diameter measuring apparatus according to the present embodiment. FIG. 2 is a side view of the light spot diameter measuring apparatus 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 rotating polygon mirror 4, an fθ lens 5, and the like.
[0013]
A so-called regular prism-shaped rotating polygonal mirror 4 which is in the scanning optical system unit 1 and whose mirror surfaces are formed at equal intervals in the circumferential direction thereof is rotatably supported on the scanning optical system unit 1. The laser beam emitted from the semiconductor laser 2 to the rotating polygon mirror 4 is condensed on the mirror surface of the rotating polygon mirror 4 by the collimating lens and the cylindrical lens 3. The laser beam focused on the rotary polygon mirror 4 is reflected by the mirror surface, passes through the fθ lens 5, and irradiates the light receiving portion 6 a of the optical sensor 6 disposed at a position corresponding to the image plane as the measurement target surface. To do. As the optical sensor 6, a slit scanning method or an area CCD method can be used.
[0014]
The apparatus of this embodiment for measuring the diameter of the light spot imaged on the surface to be measured from the scanning optical system unit 1 includes the optical sensor 6, the moving stages 7, 8, 12 of the optical sensor 6, and the rotary polygon mirror 4. A stepping motor 9 as a driving source to be connected, 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 and the like.
[0015]
The optical sensor 6 can move in the main scanning area (X direction area in the drawing) of the laser beam by the X stage 7 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 thereby be set as a virtual scanning surface as a measurement plane.
[0016]
As shown in FIG. 2, the optical sensor 6 can be moved by the Z stage 12 in the sub-scanning direction Z (direction perpendicular to the main scanning direction X) on the surface to be scanned. The Z stage 12 can be displaced to a position required at the time of measurement by three kinds of moving stages including the X stage 7 and the Y stage 8 described above. The optical sensor 6 is connected to the personal computer 11 via the controller 10. In addition, the position of the light spot condensed on the surface to be measured is displaced by controlling the rotation of the rotary polygon mirror 4 via the stepping motor 9 by the control means including the personal computer 11 for the optical sensor 6. Can be made.
[0017]
In actual measurement, a plurality of measurement points are appropriately selected from the entire main scanning line, and measurement is performed with these measurement points as “desired main scanning positions”. The laser beam reflected by the rotary polygon mirror 4 at this desired main scanning position is imaged as a light spot at substantially the center of the light receiving portion 6 a of the optical sensor 6. For this purpose, the X stage 7, Y stage 8, and Z stage 12 are driven and controlled based on the light reception information signal of the optical sensor 6, and the rotary polygon mirror 4 is rotated and stopped by the stepping motor 9. The light receiving position can be accurately adjusted.
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 by the calculation function based on the output from the optical sensor 6.
[0018]
As shown in FIG. 2, the scanning optical system unit 1 configured as described above is fixed on a dedicated table 13, and an independent stepping motor 9 separate from the scanning optical system unit 1 is disposed above the rotary polygon mirror 4. 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 protrusion amount and 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 positioned substantially coaxially with the rotation axis of the rotary polygon mirror 4 so as to face the rotary polygon mirror 4. ing.
[0019]
3 to 5 are perspective views of a joint portion between the rotary polygon mirror 4 and the clamp-like member 16.
Hereinafter, several examples of the configuration of the coupling portion will be described.
FIG. 3 shows a first embodiment of the clamp-like member 16. The stepping motor 9 and the rotary polygon mirror 4 are connected without play by a coupling 15 and a clamp-like member 16. The clamp-like member 16 can be constituted by a leaf spring or the like. In the clamp-like member 16 illustrated in FIG. 3, a clamping portion 16a formed by bending both ends of one plate-like body downward substantially vertically. A shaft portion 16b connectable to the coupling 15 is provided at the center position. As shown by the arrows in FIG. 3, the two sandwiching portions 16 a have leaf spring-like elasticity around the shaft portion 16 b, and the inner surface of each sandwiching portion 16 a is a side mirror of the rotary polygon mirror 4. In order to come into contact with the corner 4a between them, the rotary polygon mirror 4 is held in a state where the drive of the stepping motor 9 can be transmitted.
[0020]
In addition, since the rotary polygon mirror 4 of the first embodiment has a six-surface configuration, two vertices (corner portions 4a) facing each other so as to sandwich the axis center can be sandwiched by the clamp-shaped member 16. Can be easily combined 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 the desired main scanning position is obtained. It is possible to set a light spot. In this way, if the number of surfaces of the rotating polygon mirror 4 is an even number, the regular prismatic shape always has a pair of two or more vertices. Is possible.
[0021]
The clamp-like member 16 is a rigid plate-like body, but is thick enough to have elasticity in the vertical direction (substantially in the left-right direction in the clamping portion 16a), and its horizontal direction, that is, the rotational direction. Because of its extremely high rigidity, there is no bending that causes backlash in the rotational direction. According to the configuration in which the clamp-like member 16 coupled to the drive source sandwiches and connects the rotary polygon mirror 4 in this way, the rotary polygon mirror 4 can be easily held and the position of the rotary polygon mirror 4 can be accurately controlled. Is possible.
[0022]
FIG. 4 shows a second embodiment of the clamp-like member 16. The rotary polygon mirror 4 of the second embodiment has a five-surface configuration, and unlike the even-numbered surface, there are no opposing vertices. For this reason, the appropriate three vertices are sandwiched by the clamp-like member 16 and joined without play. Thus, if the number of surfaces of the rotating polygonal mirror 4 is an odd number, reliable coupling is possible by selecting three vertices. However, even if the number of faces is odd, a configuration in which only two vertices are sandwiched by the following method can be adopted.
[0023]
FIG. 5 shows a third embodiment of the clamp-like member 16. The rotating polygonal mirror 4 of the third embodiment is also of a five-surface configuration, and the coupling method with three vertices can be implemented as described above. However, with the number of surfaces of five or less, the rotating polygonal mirror 4 Any part of the clamping portion 16a is always covered with any side surface. For this reason, there is a risk of scuffing when the laser beam is reflected at the end of the mirror surface. Further, if only the two vertices are clamped, it is difficult to connect without play when the cores of the rotary polygon mirror 4 and the clamp-like member 16 are slightly displaced.
[0024]
Therefore, since the rotary polygon mirror 4 generally has a hole or a protrusion shape at the center thereof, it can be used as a convex portion or a concave portion for preventing misalignment. For example, in the third embodiment of FIG. 5, there is a hole 4 b in the rotary shaft portion of the rotary polygon mirror 4. A shaft member 16c as a guide part that can be fitted into the hole 4b is provided in the clamp-like member 16. Then, the shaft member 16c of the clamp-like member 16 is inserted into the hole 4b of the rotary polygon mirror 4, and the two vertices of the corner portion 4a are held by the two holding portions 16a with this as a fulcrum. If the holes 4b of the rotating polygon mirror 4 are used, the number of places to be clamped can be reduced, and they can be joined without play. Of course, in the case of a rotary polygon mirror having a configuration in which there is no hole 4b and the shaft shape protrudes therefrom, a hole that can be fitted to this is formed at the center of the clamp-like member 16 and the hole of this clamp-like member 16 is formed. It is good to take the structure which inserts the axial shape of a rotary polygon mirror.
[0025]
The rotating polygonal mirror 4 is generally made of a metal such as aluminum, and since its apex has an acute angle, if it is directly pinched by the leaf spring-like clamp-like member 16 or the like, its smooth surface is clamped. There is a risk of slippage due to the portion 16a. Therefore, it is desirable to provide a slip stopper for each clamping portion 16a.
[0026]
FIG. 6 is a perspective view of the clamp-like member 16 having rubber as a high friction material in the clamping portion 16a. A rubber plate 17 or the like is fixed to the inner side surface of each sandwiching portion 16a by adhesion or the like to prevent slipping with respect to the apex of the rotary polygon mirror 4.
[0027]
FIG. 7 is a perspective view of the clamp-like member 16 having the emery 18 as the high friction material in the holding portion 16a. As the high friction material, in addition to rubber, emery 18 (filed) made of an abrasive or the like can be used. In particular, when an elastic member that is easily deformed, such as rubber, is used, the rotation of the stepping motor 9 is not accurately transmitted due to the bending, and backlash may occur during reverse rotation. Therefore, by providing a high friction material such as emery that is difficult to deform, backlash can be prevented along with slipping.
[0028]
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 the above-mentioned emery is used for the sandwiching portion 16a, there is no slip and it is possible to prevent backlash, but in this case, the reflective surface of the rotary polygon mirror 4 may be damaged due to an operation error.
[0029]
Therefore, in this example, the groove 16d is formed directly in the clamping portion 16a. Grooves 16d that can be engaged with the corners 4a of the rotary polygon mirror 4 are formed on the inner side of each of the sandwiching portions 16a that are rigid bodies. In addition to preventing rush, there is no problem of damaging the reflecting surface of the rotary polygon mirror 4.
[0030]
【The invention's effect】
As described above, according to the light spot diameter measuring apparatus of the present invention, the rotary polygon mirror can be coupled to the driving source without any play on the rotary polygon mirror side without any processing. Compared with the conventional apparatus for determining the position of the mirror, the measurement time is shortened, the measurement can be automated, and the 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 a 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-like member having rubber in a clamping part.
FIG. 7 is a perspective view of a clamp-like member having emery in a holding part.
FIG. 8 is a perspective view of a clamp-like member having a groove shape in a holding part.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Scanning optical system 4 Rotating polygon mirror 4a Corner | angular part 4b Convex part or recessed part 6 Optical sensor 6a Light-receiving surface 7, 8, 12 Photosensor displacement means 9 Drive source, stepping motor 10,11 Control means 16 Clamp-like member 16a Part 16c guide part 16d groove shape 17, 18 high friction material, rubber material, emery

Claims (10)

A laser beam that can be scanned by a scanning optical system that rotatably supports a regular prismatic rotary polygon mirror is condensed as a light spot on the surface to be scanned, and the light spot diameter at a desired main scanning position on the surface to be scanned A device for measuring
An optical sensor for measurement that receives the light spot;
Optical sensor displacement means for displacing the light receiving surface of the optical sensor to the vicinity of a measurement surface equivalent to the scanned surface;
At least one or more corners of the regular prismatic shape of the rotating polygon mirror are clamped by an elastic leaf spring-like clamp member , and the driving force of the driving source is transmitted to rotate the rotating polygon mirror with the driving source. A light spot position displacing means for displacing and stopping the light spot position at an arbitrary position on the surface to be scanned;
Control means for controlling the light sensor displacement means and the light spot position displacement means based on a light reception information signal of the light sensor and calculating a light spot diameter and the like;
An optical spot diameter measuring device for a scanning optical system, comprising: 2. The light spot diameter of a scanning optical system according to claim 1, wherein the clamp-shaped member is configured to abut a holding portion obtained by bending an end portion of a leaf spring at a substantially right angle with a corner portion of the rotary polygon mirror. measuring device.   3. The scanning according to claim 1, wherein the clamp-like member has a sandwiching portion facing at least two vertices on a diagonal line among corner portions of the rotary polygon mirror having an even number of surfaces. Optical spot diameter measuring device for optical system. 3. The scanning optical system according to claim 1 , wherein the clamp-like member has a sandwiching portion that faces at least any three of the corners of the rotary polygon mirror having an odd number of surfaces. Optical spot diameter measuring device. 5. The light spot diameter measuring apparatus for a 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. . 6. The clamp member according to claim 1, further comprising a friction material that contacts a corner portion of the rotary polygon mirror and prevents sliding with the rotary polygon mirror. Optical spot diameter measuring device for scanning optical system. 7. A light spot diameter measuring apparatus for a scanning optical system according to claim 6 , wherein the clamp-like member has a rubber material at a holding portion thereof. 7. The optical spot diameter measuring device for a scanning optical system according to claim 6 , wherein the clamp-like member has emeryness in a holding portion thereof. 9. The optical spot diameter measuring device for a scanning optical system according to claim 1 , wherein the clamp-like member has a groove shape that engages with a corner of the rotary polygon mirror at a holding portion thereof. .   The drive source of the light spot position displacing means is a stepping motor capable of being positioned and supported on the outside of the scanning optical system, which is coaxially opposed to the rotary polygon mirror. Item 10. A light spot diameter measuring device for a scanning optical system according to any one of Items 1 to 9.

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