JPH04307511A - Optical writing unit - Google Patents

Abstract

PURPOSE:To allow the rapid and easy execution of the adjusting operation of a cylinder lens around its optical axis and in its optical axis direction with high accuracy. CONSTITUTION:The adjusting mechanism of the optical writing unit having the adjusting mechanism for the cylinder lens to move a lens barrel holding the cylinder lens in nearly its optical axis direction to the optical axis direction and turning this lens barrel around the optical axis has a housing 36 which has two reference planes intersecting with each other in parallel with the optical axis and are held with the intersected lines of the reference planes nearly in parallel with the optical axis, the front lens barrel 37 which has the outer peripheral part in contact with the two reference planes of the housing 36 and has a 1st long hole 41 long in the optical axis direction in the outer peripheral part and a 2nd long hole 42 long in the direction orthogonal with the optical axis, a pressing means 39 which presses the lens barrel 37 to the intersected line side, a turning means 44 which engages with the 1st long hole 41 and can turn the lens barrel 37 around the optical axis, and a moving means which engages with the 2nd long hole 42 and can move the lens barrel 37 in the optical axis direction.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing unit, for example, an optical writing unit of a laser printer, a digital copying machine, etc., which has a beam adjustment mechanism for adjusting the beam diameter of a laser beam.

0002

2. Description of the Related Art As a conventional optical writing unit, for example, there is an optical writing unit 2 that constitutes an optical writing system of a laser printer 1 as shown in FIG. 4(a), and the optical writing unit 2 adjusts a laser beam. It has a beam adjustment mechanism 3 for adjusting the beam. Figure (b) is a sectional view of the optical axis in figure (a). The optical writing unit 2 is shown in FIGS. 4(a) and 4(b).
The configuration will be explained below. The laser beam 5 emitted from the semiconductor laser 4 is shaped into parallel light 5A by a collimator lens 6 located on the optical axis, and enters a cylinder lens L1 7 in the beam adjustment mechanism 3. The beam adjustment mechanism 3 adjusts the cylinder lens L1 7 so that the beam waist of the incident parallel light 5A is formed on the ideal polygon reflection surface 8a of the polygon mirror 8A of the polygon scanner 8 which rotates at high speed. The Fθ lens 10 is a lens L2
, L3, and the lens L2 has a spherical surface of 10A.
The lens L3 is composed of a cylinder surface 10C and a toroidal surface 10D. The surface tilt of the ideal polygon reflecting surface 8a is corrected by the toroidal surface 10D of the lens L3. The corrected laser beam 5 passes through mirrors 11 and 12 and scans over the photosensitive drum 13.

As shown in FIG. 5, the conventional beam adjustment mechanism 3 includes a cylindrical lens holder 15 that holds a cylinder lens L17, and a lens holder 15 that holds the lens holder 15 rotatably around the optical axis A. a lens holder base 16;
The lens holder base 16 is aligned with the optical axis A by the guide groove 17A.
It has a flat housing 17 on which it is placed so as to be slidable in the direction. The cylinder lens L1 7 is inserted into the lens holder 15, and the upper and lower cylinder lenses L1 7 are held down by spring plates 18 provided at the end of the lens holder 15.
is screwed and fixed to the lens holder 15 with a set screw 19. The lens holder 15 is attached to this outer peripheral surface 1.
5a is pressed against and held by a slope 16A having a V-shaped cross section on the upper part of the lens holder base 16 by a pressing plate 21 that presses the upper part of the lens holder 15 downward. Further, the lens holder 15 has a lever 15A provided so as to protrude outward from the outer circumference of the lens holder 15.
A is the adjustment screw 2 against the spring force of the coil spring 22.
3 on the lens holder base 16. The lever 15A connects the adjustment screw 23 to the lens holder base 16.
Lens holder 1
5 and rotate the cylinder lens L1 7 around the optical axis for adjustment. 25 is a long hole;
The long hole 25 is provided in the lens holder base 16 in the optical axis direction, and by loosening the adjustment screw 26, the lens holder base 16 is moved along the guide groove 17A with the pin 16B at the bottom of the lens holder base 16. As a result, the cylinder lens L17 is moved and adjusted in the optical axis direction. The height of the cylinder lens L17 is adjusted by loosening the set screw 19, moving the cylinder lens L17 up and down, and then tightening the set screw 19 again to fix it.

[0004] In a laser printer for the purpose of creating printing plates, it is required to create highly accurate image samples. One of the factors for obtaining high-definition image samples is that the beam diameter formed by the optical writing unit 2 on the photosensitive drum 13 has little variation during scanning. However, the beam diameter is mainly affected by the accuracy of the optical element itself and the accuracy of the arrangement of the optical element.

In the above-mentioned optical writing system, the beam waist position is determined from the ideal polygon reflecting surface 8 due to the accuracy of the arrangement of the cylinder lens L1 7, that is, the positional deviation (error).
deviates from a. If the difference between the ideal beam diameter on the ideal polygon reflecting surface 8a and the beam diameter due to positional deviation is ΔX1, then the difference between the ideal beam diameter on the surface of the photoreceptor drum 13 and the beam diameter due to positional deviation is ΔX.
Then, the relationship between the two is expressed by the following formula ΔX=ΔX1 ・fs /ft
...It is expressed as (1).

[0006] However, fs: focal length ft of fθ lens
: Focal length of the toroidal surface of the lens L3 In equation (1), fs /ft is usually set to several times. Therefore, the error in the beam diameter on the surface of the photosensitive drum 13 is magnified several times as much as the error in the beam diameter on the ideal polygon reflecting surface 8a. Therefore, cylinder lens L
Adjust the positions of 1 and 7 with sufficient precision, and then
It is necessary to keep the beam diameter on 3 within the specified range.

[0007]

However, when adjusting the beam by the adjustment mechanism 3 in the optical axis direction, after the position of the lens holder base 16 in the optical axis direction is determined, the adjusting screw 26 is inserted into the housing. 17, the position of the lens holder base 16 changes. Also,
In adjusting the rotation of the optical axis, the center of rotation is the center of the cylindrical lens holder 15, but it is difficult to maintain the precision of the two slopes 16A that hold the lens holder 15, and the center of rotation may wobble, causing the cylinder It is difficult to adjust the lens L17 with high precision. Also, cylinder lens L
Since the height of 17 is determined by the set screw 19, highly accurate positioning is difficult. There is a problem.

[0008]

OBJECTS OF THE INVENTION The present invention has been made against the background of such prior art, and includes pressing the outer circumference of a lens holder barrel holding a cylinder lens so as to contact two reference surfaces of a housing; Adjustments are made using rotating means and moving means that respectively engage the first and second elongated holes provided on the outer circumference, eliminating the conventional tightening work after adjustment, and adjusting the rotation of the optical axis of the cylinder lens and the light. The adjustment work in the axial direction can be performed independently and with high precision using the elongated holes, and the adjustment work can be performed easily and quickly by using the eccentric pin for adjustment. Another object of the present invention is to provide an optical writing unit in which the height of the cylinder lens can be adjusted to its final position simply by rotating an adjustment screw, which can be done easily and with high precision.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a cylinder lens in which a lens barrel that holds the cylinder lens substantially in the optical axis direction is moved in the optical axis direction and rotated around the optical axis. An optical writing unit having an adjustment mechanism, wherein the adjustment mechanism has two reference planes that are parallel to the optical axis and intersect with each other, and a housing that holds the intersection line of the reference planes substantially parallel to the optical axis; The outer periphery is in contact with the two reference surfaces of the housing, and the first
a lens barrel having a second elongated hole elongated in a direction perpendicular to the elongated hole and the optical axis; a pressing means for pressing the lens barrel toward the intersection line side; The lens barrel is characterized by comprising a rotating means capable of rotating the barrel around the optical axis, and a moving means engaged with the second elongated hole and capable of moving the lens barrel in the optical axis direction. 2. In the optical writing unit according to claim 1, the rotation means includes a cylindrical member held in the housing so as to be rotatable around an axis perpendicular to the optical axis, and a cylindrical member provided at the tip of the cylindrical member that rotates around the axis. In the optical writing unit according to claim 1 or 2, the moving means has an eccentric pin that engages with the first elongated hole while being eccentric from the optical axis. A cylindrical member rotatably held in the housing; and an eccentric pin provided at a tip of the cylindrical member eccentrically from the axis and engaged with the second elongated hole. In the optical writing unit according to claim 1, 2 or 3, the lens barrel includes a first spring member that biases the cylinder lens in the optical axis direction and holds the cylinder lens slidably up and down; a second spring member biasing upward from the bottom perpendicular to the optical axis; and a second spring member screwed into a screw hole at the top of the lens barrel, the tip of which contacts the top of the cylinder lens to move the cylinder lens up and down. It is characterized by having a movable height adjustment screw.

0010

[Operation] According to claim 1 of the present invention, the outer circumferential portion of the lens holder lens barrel that holds the cylinder lens is pressed so as to come into contact with two reference surfaces of the housing, and the first and second lengths are provided on the outer circumferential portion. Since a rotating means and a moving means that respectively engage the holes are provided, the lens holder barrel has two parts.
The two reference planes are pressed against each other to ensure accurate positioning in the optical axis direction, and the two first and second elongated holes on the outer periphery of the lens barrel allow the elongated holes to be displaced independently of each other only in the direction perpendicular to the longitudinal direction. Then, the movement of the lens barrel in the optical axis direction and the rotation around the optical axis are independently and directly adjusted, and the adjustment work is completed.

Further, in claim 2, when the cylindrical member of the rotating means is slightly rotated about the axis, the first elongated hole that is engaged with the eccentric pin at the tip of the cylindrical member is moved in the longitudinal direction of the first elongated hole. The lens barrel is rotated only in the direction orthogonal to the optical axis, that is, only in the circumferential direction of the lens barrel, and the lens barrel is rotated around the optical axis. Further, in claim 3, when the cylindrical member of the moving means slightly rotates around the axis, the second elongated hole, which is engaged with the eccentric pin at the tip of the cylindrical member, is moved in a direction perpendicular to the longitudinal direction of the second elongated hole. In other words, the lens barrel is moved only in the optical axis direction.

Further, in claim 4, when the height adjustment screw at the top of the lens barrel is moved up and down, the top of the cylinder lens with which the tip of the height adjustment screw contacts is moved up and down, and the second height adjustment screw is moved up and down. The cylinder lens, which is biased upward by a spring member, is directly moved up and down against the biasing force for adjustment.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. 1 to 3 are diagrams showing optical writing units according to claims 1 to 4 of the present invention, and the same components as shown in FIG. 4 are given the same reference numerals. Optical writing unit 31 shown in FIG.
is the same as the optical writing unit shown in FIG. 4 except for the beam adjustment mechanism 33. In the optical writing unit 31,
The laser beam 5 adjusted by the beam adjustment mechanism 33 forms a beam waist on the polygon mirror 8A of the polygon scanner 8, is reflected by the polygon mirror 8A, and is formed into an ideal polygon reflecting surface by the lenses L2 and L3 of the two Fθ lenses 10. The tilt of the mirror 8a is corrected, and the mirrors 11 and 12
The photoreceptor drum 13 (not shown) is scanned.

As shown in FIGS. 1 and 2, the beam adjustment mechanism 33 has two reference surfaces parallel to the optical axis A and orthogonal to each other, a bottom surface 35a and a side surface 35b (referred to as reference surface 35 when representative). It has a housing 36 in which the intersection line B of the bottom surface 35a and the side surface 35b is held parallel to the optical axis A. The reference surface 35 is a reference when assembling a lens barrel 37, which will be described later. Two reference planes 35 of housing 36
A lens barrel 37 that holds the cylinder lens L17 substantially in the direction of the optical axis A is arranged so that its outer peripheral portion 37a is in contact with the lens barrel 37. The lens barrel 37 is perpendicular to the intersection line B.
The pressing plate 3
9, and is held in pressure contact with the reference surface 35. The pressing plate 39 is a pressing means made of a T-shaped spring member, and one end 39a is screwed to the bottom surface 35a of the housing 36, and the other end 39b is inserted into an eccentric pin (FIG. 3), which will be described later.
A loophole 39c shown in c) is provided.

The pressing plate 3 is located at the outer peripheral portion 37a of the lens barrel 37.
9, that is, the side pressed by the other end 39b of the pressing plate 3
3(a), (
As shown in b), a first long hole 41 long in the direction of the optical axis A and a second long hole 42 long in the direction perpendicular to the optical axis A are provided. 44 is an eccentric pin for adjustment;
As shown in FIG. 3(d), the cylindrical part 44 is a cylindrical member.
a, a grip part 44b on one end side that can rotate the cylindrical part 44a around an axis, and a cylindrical part 44 on the end surface of the other end side of the cylindrical part 44a.
It has a pin 44c which is an eccentric pin that is provided eccentrically by e from the axis of a and protrudes in the axial direction.

A supporting member 45 having a deformed L-shaped cross section is connected to the upper part of the housing 36, and the first elongated hole 41 and the second elongated hole 42 of the lens barrel 37 are formed at the tip of the supporting member 45.
Two holes 46A, 46 having a step at opposite positions.
B (referred to as 46 when representing) is provided. By inserting the other end of the cylindrical portion 44a into the stepped portion of the hole 46A of the support member 45, the adjusting eccentric pin 44 aligns the axis of the adjusting eccentric pin 44 with the center of the hole 46A, and rotates around the axis. At this time, the pin 44c at the tip of the adjustment eccentric pin is held by the first support member 45.
It is adapted to engage with the elongated hole 41. The adjustment eccentric pin 44 moves the first elongated hole 41 in the circumferential direction of the lens barrel 37 by rotating the grip portion 44b around the axis, and rotates the lens barrel 37 around the optical axis A. It is possible to move. The adjustment eccentric pin 44 and the hole 46A of the support member 45 constitute a rotating means.

Further, the adjustment eccentric pin 44 is attached to the support member 4.
By inserting the other end of the cylindrical portion 44a into the stepped portion of the hole 46B of No. 5, the axis of the adjusting eccentric pin 44 is aligned with the center of the hole 46B, and the adjusting eccentric pin 44 is rotatable around the axis. A pin 44c at the tip of the pin 44 is adapted to be engaged with the second elongated hole 42. Adjustment eccentric pin 44
By rotating the grip portion 44b around the axis, the second elongated hole 42 can be moved in the direction of the optical axis A of the lens barrel 37. Adjustment eccentric pin 44 and hole 46 in support member 45
B constitutes a means of transportation. 1 adjustment eccentric pin 4
4 can be used both as a moving means and a rotating means.

The lens holding portion 37b of the lens barrel 37 has a U-shaped peripheral frame that opens in the direction of the optical axis A and opens downward at the end of the lens barrel 37 on the semiconductor laser 4 side. A cylinder lens L is placed within the frame of the lens holding portion 37b.
1 7 are fitted and held by two presser springs 50. The presser spring 50 includes a first spring member 51 in the shape of two upper and lower claws that urges the periphery of the cylinder lens L1 7 in the direction of the optical axis A so that the cylinder lens L1 7 can freely slide up and down, and a first spring member 51 in the shape of an upper and lower claw that presses the cylinder lens L1 7 on the lower part. It has a curved second spring member 52 that urges upward from the bottom. Reference numeral 53 indicates an adjustment screw, and the adjustment screw 53 is screwed into a screw hole at the top of the lens holding portion 37b, and the tip of the adjustment screw 53 is in contact with the top of the cylinder lens L17. By screwing the adjustment screw 53 into the screw hole or returning it, the cylinder lens L17 can be moved up and down by the biasing force of the second spring member 52.

Next, the operation will be explained. Lens barrel 3
The cylinder lens L1 is placed within the frame of the lens holding portion 37b of No.7.
7 is assembled, and the cylinder lens L1 7 is screwed and held on the lens holding portion 37b by a presser spring 50. First elongated hole 41 and second elongated hole 42 of lens barrel 37
are the holes 46 on the side of the housing 36 far from the intersection line B.
A and the hole 46B, and is arranged so that the outer peripheral part 37a contacts the bottom surface 35a and the side surface 35b of the housing 36, and the lens barrel 37 is moved by the pressing plate 39 to the intersection line B.
It's pressed to the side. Since the outer circumferential portion 37a of the lens barrel 37 is in contact with the two reference surfaces 35 of the housing 36, the cylinder lens L17 is arranged substantially in alignment with the optical axis direction with high precision.

To adjust the direction of the optical axis A of the cylinder lens L17, the other end of the cylindrical portion 44a of the adjustment eccentric pin 44 is fitted into the hole 46B of the support member 45, and the pin 44
c is engaged with the second elongated hole 42 of the lens barrel 37. By grasping the gripping portion 44b of the adjustment eccentric pin 44 and rotating it by an angle θ around the axis, the pin 44c is moved to the second position.
Engaged with the long hole 42, the lens barrel 37, that is, the cylinder lens L17 is moved in the direction of the optical axis A by ΔH expressed by the following formula.
move only.

ΔH=e・sinθ
...(2) Also, cylinder lens L1
7 around the optical axis A, use the adjustment eccentric pin 4.
The other end of the cylindrical portion 44a of the lens barrel 37 is fitted into the hole 46A of the support member 45, and the pin 44c is inserted into the first elongated hole 41 of the lens barrel 37.
to engage. When the grip portion 44b of the adjustment eccentric pin 44 is gripped and rotated around the axis by an angle θ, the pin 4
4c engages with the first elongated hole 41 to move the lens barrel 37, that is, the cylinder lens L17, around the optical axis A by ΔL expressed by the following equation.

ΔL=e・sinθ
(3) If the radius from the optical axis A to the first elongated hole 41 is r, the cylinder lens L17 rotates around the optical axis A by Δθ expressed by the following equation. Δθ=ΔL/r
=e・sinθ/r... (4) The pin 44c engages with the second elongated hole 42, and rotates around the axis C by an angle θ while engaging with the engagement surface 42a of the second elongated hole 42. At this time, the pin 44c presses the second elongated hole 42 in the direction of the optical axis A while contacting the engagement surface 42a, and also contacts the engagement surface 42a and responds to the contact force in the longitudinal direction of the second elongated hole 42. However, the pin 44c and the engagement surface 42
The contact force with a is small and negligible, and the component in the direction perpendicular to the optical axis A direction is almost negligible. Therefore, when adjusting the direction of the optical axis A using the second elongated hole 42, the adjustment around the optical axis A is not affected. Similarly, when adjusting the rotation of the optical axis A using the first elongated hole 41,
Adjustment in the optical axis A direction is not affected. In other words, the adjustment in the direction of the optical axis A and the adjustment around the optical axis A can be performed independently and with high precision, and the adjustment work can be done quickly by using the eccentric adjustment pin and engaging and disengaging the first and second elongated holes. and can be easily adjusted.

Furthermore, in order to adjust the height of the cylinder lens L17, by screwing in or returning the adjustment screw 53, the cylinder lens L17 is urged upward at two locations at the bottom by the two second spring members 52. Because
The cylinder lens L17 moves up and down almost vertically by the amount of movement corresponding to the rotation of the adjustment screw 53, and no further adjustment is necessary.

[0024]

[Effects of the Invention] As explained above, according to the present invention,
In claim 1, the outer peripheral part of the lens holder lens barrel holding the cylinder lens is pressed so as to come into contact with two reference surfaces of the housing, and the circuit engages with the first and second elongated holes provided in the outer peripheral part, respectively. By adjusting using a moving means and a moving means, the conventional tightening work after adjustment is eliminated, and the adjustment work around the optical axis of the cylinder lens and in the direction of the optical axis can be performed independently and with high precision using a long hole. In addition, according to claims 2 and 3, the adjustment work can be easily and quickly performed by using an eccentric pin for adjustment. Further, in the fourth aspect, the height of the cylinder lens can be adjusted simply by rotating the adjustment screw, and can be easily performed with high precision.

[Brief explanation of drawings]

FIG. 1 is an explanatory overall plan view of an optical writing unit according to the present invention.

FIG. 2 is a diagram showing the beam adjustment mechanism in FIG. 1;
(a) is a front sectional explanatory view thereof, and (b) is a side view taken along the line B-B with the adjustment eccentric pin 44 of (a) removed.

3 is a diagram showing each part in FIG. 2, (a) is an explanatory view of the lens barrel viewed diagonally from above, (b) is a front view of (a), and (c) is a front view of the pressing plate. (d) is a front view of the eccentric pin for adjustment, (e) is a front view of the lens barrel with the presser spring attached, (f) is a side view of (e), and (g) is the front view of the presser spring. A front view, (h) a side view of (g).

FIG. 4 is a diagram showing a conventional optical writing unit, in which (a) is an explanatory overall plan view thereof, and (b) is an explanatory view showing an optical system in the optical axis direction of (a).

FIG. 5 is a diagram showing a beam adjustment mechanism of a conventional optical writing unit, in which (a) is an explanatory plan view thereof, and (b) is an explanatory front view thereof.

[Explanation of symbols]

7 Cylinder lens L1 31 Optical writing unit 33 Beam adjustment mechanism 35 Reference surface 36 Housing 37 Lens barrel 37a Outer periphery 39 Pressing plate (pressing means) 41 First elongated hole 42 Second elongated hole 44 Adjustment eccentric pin (rotating Means) 44a
Cylindrical part (cylindrical member) 44c Pin (eccentric pin) 45 Support member (rotating means) 50 Presser spring 51 First spring member 52 Second spring member 53 Adjustment screw A Optical axis B Line of intersection

Claims (4)

[Claims] 1. An optical writing unit comprising a cylinder lens adjustment mechanism for moving a lens barrel that holds a cylinder lens substantially in the optical axis direction in the optical axis direction and rotating it around the optical axis, the adjustment mechanism comprising: has two reference planes that are parallel to the optical axis and intersect with each other, and a housing whose intersection line between the reference planes is held substantially parallel to the optical axis; a lens barrel having a first elongated hole elongated in the optical axis direction and a second elongated hole elongated in the direction orthogonal to the optical axis; a pressing means for pressing the lens barrel toward the intersection line side; and the first elongated hole. a rotating means that engages with the lens barrel and is capable of rotating the lens barrel around the optical axis; and a moving means that engages with the second elongated hole and allows the lens barrel to move in the optical axis direction. An optical writing unit characterized by: 2. The rotation means includes a cylindrical member held in the housing so as to be rotatable about an axis perpendicular to the optical axis, and a cylindrical member provided eccentrically from the axis at the distal end of the cylindrical member, the first length being eccentric from the axis. The optical writing unit according to claim 1, further comprising an eccentric pin that engages with the hole. 3. The moving means includes a cylindrical member held in the housing so as to be rotatable around an axis perpendicular to the optical axis, and the second elongated hole provided eccentrically from the axis at the tip of the cylindrical member. 3. The optical writing unit according to claim 1, further comprising an eccentric pin that engages with the optical writing unit. 4. The lens barrel includes a first spring member that biases the cylinder lens in the optical axis direction and holds the cylinder lens slidably up and down; a second spring member that biases the cylinder lens; and a height adjustment screw that is screwed into a screw hole at the top of the lens barrel, a tip of which contacts the top of the cylinder lens, and is capable of moving the cylinder lens up and down. 4. The optical writing unit according to claim 1, wherein the optical writing unit comprises: