JP3287033B2 - Light beam scanning optical system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning optical system,
Specifically, a light beam emitted in one direction from a light source is deflected and scanned on one plane by a deflecting unit, and an image is read,
The present invention relates to a light beam scanning optical system for writing.

[0002]

2. Description of the Related Art Generally, a light beam scanning optical system of this type is mainly used as a head for writing an image on 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 determined by branching the laser beam at the leading end of the printing angle of view from the main optical path toward the photoconductor.
The operation is guided to the OS sensor, and synchronization is performed based on the detection signal. A condenser lens for a laser beam is provided immediately before the SOS sensor, and a resin lens that is inexpensive and has high productivity is used as the condenser lens. In a resin condenser lens, a lens part and a holder part around the lens part are integrally formed.

[0003] However, the resin condensing lens has a problem that a laser beam having an angle of view that is not correct for detecting an SOS signal due to irregular reflection or irregular refraction of the laser beam at an edge portion of the lens portion enters the SOS sensor. Had occurred. In this case, there is a possibility that the printing start position is shifted or the SOS signal is detected twice and an image error occurs. Therefore, a countermeasure for providing a slit for limiting the incidence of an extra laser beam is known. However, if a slit member is separately provided, the number of parts and the number of assembling steps increase.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide irregular reflection other than a light beam passing through the center of a light-collecting element.
An object of the present invention is to provide a light beam scanning optical system that can reliably prevent light, diffused light, and the like from entering a light receiving element with a simple configuration.

In order to achieve the above object, a first light beam scanning optical system according to the present invention is a light beam scanning optical system which deflects and scans a light beam emitted in one direction onto one plane by a deflecting means. An imaging element for forming an image of the deflected and scanned light beam on the surface to be scanned, a light receiving element for receiving the deflected and scanned light beam, and condensing the light beam passing through the imaging element on the light receiving element A light collecting element, and a housing for mounting each component of the light receiving element and the optical system, and a light receiving element mounting portion of the housing between the light collecting element and the light receiving element ; Pass through the center
Together to incident light beam to the light receiving element, irregularly reflected light at the edge portion of the condensing element, to form a light beam introduction cylinder portion for shielding the diffuse light. According to the first light beam scanning optical system according to the present invention, the light beam introduction tube prevents external dust and dust from adhering to the light receiving element and also prevents external light from entering. Further, the cylindrical portion absorbs irregularly reflected light and the like other than the regular (passed through the center of the light-collecting element) light beam, and prevents leakage to the outside. Further, since the light beam introducing cylinder is located closer to the light receiving element than the light collecting element, it is possible to prevent diffused light generated when passing through the light collecting element from entering the light receiving element.

Further, a second light beam scanning optical system according to the present invention is a light beam scanning optical system which deflects and scans a light beam emitted in one direction onto one plane by a deflecting means. An imaging element for forming an image of the beam on the surface to be scanned, and a light receiving element for receiving the deflected and scanned light beam,
A light-condensing element for condensing the light beam that has passed through the imaging element on the light-receiving element, and a housing for mounting each of the light-receiving element and each component of the optical system, wherein the light-condensing element and the light-receiving element A slit for blocking irregularly reflected light and diffused light at the edge of the light condensing element is provided in the light receiving element mounting portion of the housing in a direction substantially orthogonal to the scanning direction of the light beam. In the second light beam scanning optical system according to the present invention, the slit is narrow its width to the scanning direction of the light beam, normally by the small width (light condensing element
Only the light beam ( passing through the center of the element) is incident on the light receiving element. On the other hand, the slit is formed large in a direction substantially orthogonal to the scanning direction. The scanning line of the light beam is adjusted in a direction orthogonal to the scanning direction and may be shifted in this direction. Such a displaced light beam can surely pass through the slit as long as it is within the range in the longitudinal direction of the slit. Further, since the slit is located closer to the light receiving element than the light collecting element, it is possible to prevent diffusely reflected light and diffused light generated at the edge portion of the slit when passing through the light collecting element from entering the light receiving element.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a light beam scanning optical system according to the present invention will be described below with reference to the accompanying drawings. The following embodiment shows an embodiment in which the present invention is applied to a print head for writing an image on a photosensitive member of a laser printer.
1, 2 and 3, the print head is schematically illustrated
A housing 10 integrally formed from a resin material, a light source unit 20, and a print start position detecting sensor 30 (hereinafter, referred to as a print start position sensor 30).
SOS sensor), a polygon mirror 45, a toric lens 50, and a toroidal mirror 53.

[0008] 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 reflection surfaces on the outer peripheral portion, and is rotationally driven at a constant speed in the direction of arrow a by a motor 46. Therefore, the laser beam is transmitted to the rotating polygon mirror 4.
Deflected scanning is performed at a constant angular velocity in one plane by each of the reflecting surfaces 5. The scanned laser beam is applied to the toric lens 5.
0, is reflected by the plane mirrors 51 and 52, further reflected by the toroidal mirror 53, passes through the glass plate 54, and forms an image on the photosensitive drum 110. Photoconductor drum 1
Reference numeral 10 denotes a rotary drive in the direction of arrow c, 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 photosensitive drum 110 by the rotation of 0 (sub-scan).

On the other hand, of the laser beam deflected and scanned by the polygon mirror 45, the laser beam at the leading end in the main scanning direction is reflected by the plane mirror 51, is reflected by the plane mirror 35, and passes through the condenser lens 31. The light enters the SOS sensor 30. Then, a printing start position for each scanning line on the photosensitive 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 (all not shown) for condensing a laser beam are incorporated.
5 fixed. The SOS sensor 30 is fixed on the circuit board 25. A drive circuit (not shown) for a laser diode is mounted on the substrate 25, and an output section of the SOS sensor 30 is electrically connected to the drive circuit on the substrate 25.

By the way, as is apparent from FIGS. 1 and 3,
In the present embodiment, the beam incident 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 beam emitted from the light source unit 20. That is, the optical axis of the incident beam is perpendicular to the light receiving surface of the SOS sensor 30, the optical axis of the incident beam coincides with the optical axis of the SOS sensor 30, and the light amount and spot diameter of the incident beam 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 one substrate 25, the configuration is simple, and the mounting work and the position adjusting work are also easy. In addition, 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, the intrusion of external noise into the output signal is extremely small as compared with a structure in which the output signal is connected by a lead wire. Therefore, it is not necessary to consider noise measures.

Here, the condensing lens 31 for condensing the laser beam incident on the SOS sensor 30 and its mounting structure will be described. As shown in FIG. 4, the condenser lens 31 includes a spherical lens portion 31a and a holder portion 31 around the spherical lens portion 31a.
b and are integrally formed of a resin material.
On the other hand, the holding member 1 of the condenser lens 31 is provided in the housing 10.
The four, fourteen and fifteen project from the inside of the housing 10. The holding member 15 faces the holding members 14, 14, and the holding member 15 has an arc-shaped light shielding portion 15 a. A small projection 1 is provided on the floor between the holding members 14 and 15.
6, 16 are protrudingly provided. The condenser lens 31 is fixed by press-fitting the holder portion 31b between the ridges 14a, 14a of the holding members 14, 14 and the holding member 15.
A small projection 31c is formed on the holder portion 31b, and the back surface of the holder portion 31b is pressed against the ridge portion 14a.
When the small projection 31c is pressed against the back surface of the holding member 15, the spherical lens portion 31a is positioned in the optical axis direction.
Further, the lower surface 31d of the holder portion 31b is
By contacting the upper side, the spherical lens portion 31a is positioned in the height direction. Further, the positioning of the spherical lens portion 31a in the width direction is such that the lower projecting piece 31e is
6 is performed.

FIG. 5 shows that the condenser lens 31 is attached to the holding members 14 and 1.
FIG. In this state, the light blocking portion 15a of the holding member 15 covers the lower edge portion of the spherical lens portion 31a. The laser beam is applied to the lens unit 3 in the direction indicated by the arrow B.
Scan 1a. Therefore, the edge portion E of the lens portion 31a
However, the light-shielding portion 15a is located at the edge portion E, and the laser beam is shielded. Therefore, irregular reflection and irregular refraction do not occur at the edge portion E, and only a normal laser beam enters the SOS sensor 30.

Incidentally, irregular reflection and irregular refraction occur at the edge portion E 'opposite to the edge portion E. However, since the detection of the SOS signal is based on the starting point of incidence on the sensor 30, the scanning direction is small. It is sufficient to prevent the laser beam from diffusing at the edge E on the upstream side of B. In order to obtain the above effects, the radius R of the light shielding portion 15a is equal to the diameter D of the lens portion 31a.
It suffices that the relationship of D2 ≦ 2 · R <D1 be satisfied between 1 and the effective diameter D2 (see FIG. 6).

Next, the condenser lens 31 and the SOS sensor 30
The light-shielding means provided between them will be described. As shown in FIGS. 4 and 6, the light-shielding tubular portion 12 protrudes from the outer wall of the housing 10. I do. That is, the cylindrical portion 12 is covered with the circuit board 25, and external light is prevented from entering the SOS sensor 30.
Further, the cylindrical portion 12 prevents dust and dust from adhering to the light receiving surface of the SOS sensor 30 and also prevents the laser beam from leaking outside.

Further, a slit 17 is formed at the bottom of the cylindrical portion 12, that is, between the condenser lens 31 and the SOS sensor 30. The slit 17 extends in a direction orthogonal to the scanning direction B of the laser beam. In other words,
The width of the slit 17 is narrow in the scanning direction B, and only a normal laser beam enters the light receiving element due to the narrow width. On the other hand, the slit 17 is in the scanning direction B
It is formed large in a direction perpendicular to the direction. The scanning line of the laser beam is adjusted by changing the inclination angle of the mirror 35 described above. This adjustment is performed by displacing the scanning line in a direction orthogonal to the scanning direction B. The scanning line may be shifted due to an error in mounting the mirrors 51, 35, etc., but at this time, the scanning line is shifted in a direction orthogonal to the scanning direction B. Therefore, the slit 17
Extends in the direction orthogonal to the scanning direction B, the laser beam can pass through the slit 17 even when the scanning line is shifted. It should be noted that the laser beam is
Is slightly deviated from the center, the lens 31 is formed of a spherical lens, so that the light is appropriately focused on the light receiving surface of the SOS sensor 30.

The width of the slit 17 is SO
The setting is made so as to cut out a widened portion other than the effective area incident on the S sensor 30. That is, as shown in FIG. 6, the distance between the condenser lens 31 and the SOS sensor 30 is L1, the distance between the condenser lens 31 and the slit 17 is L2,
Assuming that the diameter of D1 is D1 and its effective diameter is D2, the slit width d falls within the range of the following expression.

{(L1−L2) · D2} / L ≦ d <{(L1−L2) · D1} / L By setting the slit width in this way, a normal beam within the effective area is transmitted to the SOS sensor 30. Incident. The diffused light B1 generated at the edge of the condenser lens 31 is
Can not pass through. Further, the diffused light B2 that has passed through the slit 17 is absorbed by the inner wall surface of the cylindrical portion 12 without being incident on the SOS sensor 30. The inner wall surface of the cylindrical portion 12 is subjected to a treatment such as painting capable of absorbing a laser beam.

That is, in this embodiment, the condenser lens 3
1 is provided with a light shielding portion 15a on the holding member 15;
By providing the slit 2 and the slit 17, external light, irregularly reflected light and irregularly refracted light are cut off, and only a normal and effective laser beam is incident on the SOS sensor 30, and the printing start position can be accurately and reliably detected. . The light beam scanning optical system according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the invention.

For example, the SOS sensor 30 does not necessarily need to be provided on the circuit board 25 together with the light source unit 20, and may be provided on a dedicated board.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show a print head which is an embodiment of a light beam scanning optical system according to the present invention.

FIG. 1 is a perspective view illustrating a schematic configuration of a print head.

FIG. 2 is an elevation view showing an arrangement of each optical element and a laser beam optical path.

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

FIG. 4 is a perspective view showing a condenser lens and a mounting structure thereof.

FIG. 5 is an elevation view showing a state in which a condenser lens is attached to a holding member.

FIG. 6 is a cross-sectional view showing a state where a laser beam is regulated by a slit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Housing 12 ... Light shielding cylinder part 14, 15 ... Holding member 15a ... Light shielding part 17 ... Slit 30 ... Printing start position detection sensor (light receiving element) 31 ... Condensing lens 45 ... Polygon mirror

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akika Hamada 2-3-113 Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Camera Co., Ltd.

Claims (2)

(57) [Claims] 1. A light beam scanning optical system for deflecting and scanning a light beam radiated in one direction onto one plane by a deflecting means, comprising: an imaging element for forming an image of the deflected and scanned light beam on a surface to be scanned; A light receiving element that receives a light beam that has been deflected and scanned; a light collecting element that focuses the light beam that has passed through the imaging element on the light receiving element; and a housing for attaching the light receiving element and each component of the optical system with the door, the light receiving element mounting portion of the housing between the light focusing element and the light receiving element, dissipate incident <br/> light beam passing through the center of the light focusing element to the light receiving element, the current Optical element
A light beam scanning optical system, characterized in that a light beam introducing cylinder portion for blocking irregularly reflected light and diffused light at an edge portion is formed. 2. A light beam scanning optical system for deflecting and scanning a light beam radiated in one direction onto one plane by a deflecting means, comprising: an imaging element for forming an image of the light beam deflected and scanned on a surface to be scanned; A light receiving element that receives a light beam that has been deflected and scanned; a light collecting element that focuses the light beam that has passed through the imaging element on the light receiving element; and a housing for attaching the light receiving element and each component of the optical system with the door, the light receiving element mounting portion of the housing between the light focusing element and the light receiving element, turbulence at the edge portion of the light focusing element
A light beam scanning optical system, wherein a slit for blocking reflected light and diffused light is provided in a direction substantially orthogonal to a scanning direction of the light beam.