JPH06148492A - Lens holding mechanism and light beam scanning optical system - Google Patents

Abstract

PURPOSE:To accurately position and hold a lens made of resin even when the trace (burr) of the parting line of a molding die is left. CONSTITUTION:The lens made of resin 31 is constituted of a lens part 31a and a holder part 31b, and the burr is left along a ridgeline A. Holding member 14 and 15 having projected line parts 14a and 15a, holding members 16 and 16 opposed to the projected line parts 14a and 15a, and small projections 17 and 17 on a floor surface are formed in a housing 10. The holder part 31b of the lens 31 is press-fitted between the projected line parts 14a and 15a and the holding members 16 and 16, and the lower surface 31d thereof abuts on the small projections 17 and 17, then the projecting piece 31e is fitted between the small projections 17 and 17. At such a time, the burr along the ridgeline A does not abut on any of the members 14, 15, 16 and 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens holding mechanism and a light beam scanning optical system. Specifically, the lens holding mechanism is for holding a lens in which a lens portion and a holder portion around the lens portion are integrally molded with a resin material. The light beam scanning optical system is for deflecting and scanning a light beam emitted from a light source in one direction on one plane by a deflecting means to read or write an image.

[0002]

2. Description of the Related Art Generally, a light beam scanning optical system is used as an image writing head for a photosensitive member of a laser printer. In the conventional print head, the printing start position of each scanning line of the laser beam deflected and scanned by the polygon mirror is guided to the SOS sensor by branching the laser beam at the leading end portion of the printing field angle from the main optical path toward the photoconductor. , Were synchronized based on this detection signal. A condenser lens for the laser beam is installed immediately before the SOS sensor,
For this condenser lens, a resin lens that is inexpensive and has high productivity is used. The resin condensing lens is integrally formed with a lens portion and a holder portion around the lens portion.

However, in the above-mentioned resin-made condenser lens, a parting line mark of the molding die, that is, a so-called "burr" remains, and this burr contacts the holding member of the condenser lens to correctly position the condenser lens. It had a problem that it could not be done.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a lens capable of accurately positioning and holding a lens made of resin even if a marking line (burr) of a molding die is left on the lens. It is to provide a holding mechanism. Still another object of the present invention is to provide a light beam scanning optical system capable of accurately positioning and holding a resin condenser lens.

In order to achieve the above object, the lens holding mechanism according to the present invention has a concave portion formed on the positioning surface with which the holder portion of the resin lens abuts, the portion facing the burr left on the holder portion. did. That is, the burr is positioned in the concave portion of the holding mechanism, does not come into contact with the positioning surface, and the lens is correctly positioned. Further, in the optical beam scanning optical system according to the present invention, a holding member for holding the resin condenser lens is integrally formed in a housing for mounting each component of the optical system, and the holding member is A concave portion was formed on the positioning surface with which the holder portion of the condenser lens abuts, and the portion facing the burr left on the holder portion. Even in this light beam scanning optical system,
Despite the burr remaining on the condenser lens, the burr does not come into contact with the positioning surface in the recess and the condenser lens is correctly positioned.

[0006]

Embodiments of a lens holding mechanism and a light beam scanning optical system according to the present invention will be described below with reference to the accompanying drawings. 1, 2 and 3 show the light beam scanning optical system according to the present invention applied as a print head for writing an image on a photoconductor of a laser printer. The print head includes a housing 10 integrally formed of a resin material, a light source unit 20, a print start position detection sensor 30 (hereinafter referred to as an SOS sensor), a polygon mirror 45, and a toric lens 50. , And toroidal mirror 53.

The laser beam emitted from the light source unit 20 is reflected by the plane mirror 40, passes through the cylindrical lens 41, and enters the polygon mirror 45. The polygon mirror 45 has four reflecting surfaces on its outer peripheral portion, and is rotationally driven by a motor 46 in the direction of arrow a at a constant speed. Therefore, the laser beam rotates the polygon mirror 4
Deflection scanning is performed in one plane at a constant angular velocity by each of the reflecting surfaces of 5. The toric lens 5 scans the laser beam.
The light passes through 0, is reflected by the plane mirrors 51 and 52, is further reflected by the toroidal mirror 53, is transmitted through the glass plate 54, and forms an image on the photosensitive drum 110. Photoconductor drum 1
Reference numeral 10 is rotationally driven in the direction of arrow c to perform main scanning of the laser beam in the direction of arrow b and the photosensitive drum 11 in the direction of arrow c
An image is formed as an electrostatic latent image on the photoconductor drum 110 by the rotation of 0 (sub scanning).

On the other hand, of the laser beams deflected and scanned by the polygon mirror 45, the laser beam at the front end in the main scanning direction is reflected by the plane mirror 51, then by the plane mirror 35, and passes through the condenser lens 31. It is incident on the SOS sensor 30. Then, the print start position for each scanning line on the photoconductor drum 110 is determined based on the detection signal of the laser beam from the SOS sensor 30.

The light source unit 20 has a casing in which a laser diode as a laser light source, a photodiode for monitoring a light amount, and a collimator lens (not shown) for condensing a laser beam are incorporated.
It is fixed on 5. The SOS sensor 30 is fixed on the circuit board 25. A drive circuit (not shown) for the laser diode is mounted on the substrate 25, and the output section of the SOS sensor 30 is electrically connected to the drive circuit on the substrate 25.

By the way, as is clear from FIGS. 1 and 3,
In this embodiment, the incident beam on the SOS sensor 30 has its optical path bent by the two mirrors 51 and 35, and enters the SOS sensor 30 in a state parallel to the emitted beam from the light source unit 20. That is, the optical axis of the incident beam is incident perpendicularly to the light receiving surface of the SOS sensor 30, the optical axis of the incident beam and the optical axis of the SOS sensor 30 coincide, and the light quantity and spot diameter of the incident beam are Stabilize. Therefore, the output signal from the SOS sensor 30 is also stabilized. Further, since the light source unit 20 and the SOS sensor 30 are mounted on the single substrate 25, the structure is simple and the mounting work and the position adjusting work are easy. Further, since the output signal from the SOS sensor 30 is output to the drive circuit of the light source unit 20 by the printed wiring on the substrate 25, intrusion of external noise into the output signal is extremely reduced as compared with the structure connected by the lead wire. It is not necessary to consider noise countermeasures.

Now, the condenser lens 31 for condensing the laser beam incident on the SOS sensor 30 and its mounting structure will be described. 4 and 5 show a first embodiment of the lens holding mechanism according to the present invention. The condenser lens 31 is
The spherical lens part 31 is integrally molded with a resin material.
a and a holder portion 31b around it, and small protrusions 31c are formed on both front sides of the holder portion 31b.
A protrusion 31e is formed on 1d. The molding die (not shown) is a two-part type, and its parting line is formed along the ridgeline A of the holder portion 31b, and a parting line mark (burr) remains on this ridgeline A. Further, the protrusion 31f on the upper surface of the holder portion 31b corresponds to a resin-molded nozzle portion. The spherical lens portion 31a is thinner than the holder portion 31b and is formed so as not to project to the outside. This is to prevent the lens surface from coming into contact with the table and being damaged when the lens surface is placed downward.

On the other hand, the housing 10 has a condenser lens 31.
Holding members 14, 15, 16, 17 of the housing 10
It is projected inside. The holding members 16 and 16 face the ridges 14a and 15a of the holding members 14 and 15, and the side surface of the holding member 14 is a guide surface 14 inclined upward.
It is assumed to be b. In addition, holding members (small protrusions) 17, 17
Is protrudingly provided on the floor between the holding members 14 and 15 and the holding members 16 and 16 in a semicircular cross section.

The condenser lens 31 is fixed by press-fitting the holder portion 31b between the holding members 14 and 15 and the holding members 16 and 16. This press-fitting is performed along the guide surface 14b of the holding member 14, and the back surface of the holder portion 31b presses against the ridge portions 14a and 15a, and the small protrusion 31c presses against the holding members 16 and 16 to hold the holder portion 31b. Bottom surface 31
d contacts the small protrusions 17 and 17, and the protruding piece 31e fits between the small protrusions 17 and 17. The holder portion 31b has a ridge portion 14 on its back surface due to the elastic force of the holding members 16 and 16 in a press-fitted state to the holding members 14, 15, 16 and 16.
The lens portion 31a is positioned in the optical axis direction x by being pressed against a and 15a. Further, the lens portion 31a is positioned in the vertical direction z by the lower surface 31d of the holder portion 31b contacting the small protrusions 17 and 17, and the protrusion 3
By fitting 1e between the small protrusions 17, 17, the positioning is performed in the lateral direction y orthogonal to the optical axis. Holder part 31b
Since the small protrusions 31c are formed on the front surface and the back surface is flat, that is, the front and back surfaces are asymmetrical, it is possible to prevent the mistake of setting the front and back at the time of assembly.

FIG. 5 shows a condenser lens 31 for holding members 14, 1
The state attached to Nos. 5, 16 and 17 is shown. In this state, the parting line traces (burrs) left on the ridgeline A of the condenser lens 31 are small protrusions 17, 17 and the holding member 1.
Located in the gap of 6, 16 and holding members 14, 15, 16,
It does not come into contact with any of the 17. Therefore, the condenser lens 31 is accurately positioned.

FIG. 6 shows a second embodiment of the lens holding mechanism. The condenser lens 61, like the condenser lens 31,
It is composed of a spherical lens portion 61a and a holder portion 61b, and the parting line of the molding die is formed along a ridge line A, and a burr remains on this ridge line A. In addition, the holder part 6
The protrusion 61f on the upper surface of 1b corresponds to the nozzle portion of resin molding. On the other hand, in the housing 10, the holding member 74 having the protruding portions 74a, the holding member 75 having the protruding portions 75a and 75b, and the holding member 7 facing the protruding portions 74a and 75a.
6, 76, a holding member 78 facing the protruding portion 75b is formed, and a projection 77 having a semicircular cross section is formed as a holding member on the floor surface.

The condenser lens 61 is fixed by press-fitting the holder portion 61b between the holding members 74, 75, 76 and 78. At the time of this press-fitting, the front surface of the holder portion 61b is held by the holding members 76, 7 in the optical axis direction x of the lens portion 61a.
6 is pressed by the elastic force of 6, and the back surface is pressed against the ridges 74a and 75a for positioning. With respect to the vertical direction z, the lower surface 61d of the holder portion 61b is brought into contact with the protrusion 77 for positioning. Further, in the y direction orthogonal to the optical axis, the side surface 61g of the holder portion 61b is pressed by the elastic force of the holding member 78, and the other side surface 61i is pressed against the ridge portion 75b to be positioned.

In the second embodiment, the condenser lens 61
Burrs left on the ridgeline A of the holding members 76, 76, 7
8, it is located in the gap between the protruding portion 75b and the protrusion 77, and does not abut on any of the holding members 74, 75, 76, 77, 78, and the positioning is not disturbed. FIG. 7 shows a third embodiment of the lens holding mechanism. The third embodiment has basically the same structure as the first embodiment shown in FIGS. 4 and 5, and the same members are designated by the same reference numerals. The different point is that the holder part 31b of the condenser lens 31 is formed with a parting line of the molding die over the entire circumference of the central part B, and burrs remain in this part. Therefore, on the floor surface of the housing 10, the small projections 17 'divided into two in the optical axis direction,
17 'was formed so that the burr was located in the gap 17a between the two.

FIG. 8 shows a fourth embodiment of the lens holding mechanism. This fourth embodiment also corresponds to the condenser lens 31 in which burrs are left over the entire circumference of the central portion B of the holder portion 31b, and the holding members 14 and 15 and the holding members 16 and 16 are provided.
And the table are continuously formed on the floor surface to form the mounting table 19, and the mounting table 19 is provided with the groove portion 19a for releasing burr.

The lens holding mechanism and the light beam scanning optical system according to the present invention are not limited to the above embodiment, but can be variously modified within the scope of its gist. In particular, the shapes of the condenser lenses 31 and 61, the respective holding members 14, 15, 16, 17, 17 ', 19, 74,
The configurations and shapes of 75, 76, 77 and 78 are arbitrary.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a print head which is an embodiment of a light beam scanning optical system according to the invention.

FIG. 2 is an elevational view showing the arrangement of optical elements and the laser beam optical path in FIG.

FIG. 3 is a plan view showing an arrangement of optical elements and a laser beam optical path in FIG.

FIG. 4 is a perspective view showing a first embodiment of a lens holding mechanism.

5 is a cross-sectional view showing the lens holding mechanism shown in FIG.

FIG. 6 is a perspective view showing a second embodiment of the lens holding mechanism.

FIG. 7 is a sectional view showing a third embodiment of the lens holding mechanism.

FIG. 8 is a sectional view showing a fourth embodiment of the lens holding mechanism.

[Explanation of symbols]

10 ... Housing 14, 15, 16, 17, 17 ', 19, 74, 75,
76, 77, 78 ... Holding member 30 ... Print start position detection sensor (light receiving element) 31 ... Resin condensing lens 31a ... Lens part 31b ... Holder part A, B ... Parting line mark (burr)

Claims (2)

[Claims] 1. A lens holding mechanism for holding a lens in which a lens part and a holder part around the lens part are integrally molded of a resin material, wherein a positioning surface with which the holder part of the lens abuts,
A lens holding mechanism, characterized in that a recess is formed in a portion of the molding die that faces the trace of the parting line left in the holder. 2. A light beam scanning optical system in which a deflecting means deflects and scans a light beam emitted in one direction on one plane, a light receiving element for receiving the deflected and scanned light beam, and a lens part and its surroundings. A holder part integrally molded of a resin material, a condenser lens for condensing the light beam incident on the light receiving element onto the light receiving element, a holding member for holding the condenser lens, and an optical system And a housing for mounting each part of the holding member, wherein the holding member is formed integrally with the housing and is a positioning surface with which the holder portion of the condenser lens abuts, and is formed on the holder portion. A light beam scanning optical system characterized in that a concave portion is formed in a portion facing a parting line trace of a die.