JPH09101471A - Optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compactly arrange an optical system which includes a photodetecting element for synchronizing light detection by providing one lens of a scanning image forming lens, consisting of >=1 lenses, with a reflection part at a part which does not contribute to optical scanning on the scanned surface of an end part on the side where deflected luminous flux is received in a deflecting direction. SOLUTION: A lens 52 on the side of the scanned surface 6 between two lenses 51 and 52 constituting the scanning image forming lens is provided with the reflection part 10 at the part which does not contribute to the optical scanning on the scanned surface on the side of the scanned surface at the end part where the deflected luminous flux is received in the deflecting direction. Consequently, the deflected luminous flux traveling to an optical scanning area L is reflected to the photodetecting element for synchronizing light detection. Therefore, the deflected luminous flux is photodetected by the photodetecting element 8 for synchronizing light detection prior to the optical scanning in the optical scanning area L and on the basis of the photodetection signal generated by the photodetecting element 8 for synchronizing light detection, the start points of the optical scanning are set uniformly to the lower end of the optical scanning area L. Thus, the deflected luminous flux is reflected by the reflection part to an optical deflector to reduce the size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical scanning device.

[0002]

2. Description of the Related Art In an optical scanning device for performing optical scanning by converging a deflected light beam deflected by an optical deflector having a deflecting / reflecting surface as a light spot on a surface to be scanned by a scanning imaging lens, the optical scanning is performed by the light spot. In order to align the optical scanning start points, the deflected light flux toward the optical scanning area is detected by a light receiving element for detecting synchronous light.

There is known an optical scanning device in which an optical system for condensing a deflected light beam on the light receiving element is integrated with a scanning and imaging lens to simplify the position adjustment of these optical systems (Japanese Patent Laid-Open No. Hei 5 (1998)). No. 19186). However, in such a device, the position of the optical system is limited by the scanning imaging lens,
Since the position where the light receiving element is arranged is also limited accordingly, it is difficult to make the layout of the device compact including the position where the light receiving element is arranged.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, it is an object of the present invention to enable compact arrangement of an optical system including a light receiving element for detecting synchronous light in an optical scanning device.

[0005]

The optical scanning device according to the present invention "contains a deflected light beam deflected by an optical deflector having a deflective reflection surface as a light spot on a surface to be scanned by a scanning imaging lens, An optical scanning device that optically scans a scanning surface "and has the following features (claim 1).

That is, one or more scanning image forming lenses, that is, one
It is composed of one or more lenses. One of the lenses forming the scanning imaging lens has a reflecting portion at a portion of the deflection direction (direction in which the deflected light flux is displaced by the deflection) on the side where the deflected light flux is received, which does not contribute to optical scanning of the surface to be scanned. Is provided.

The deflected light beam heading for the optical scanning region is reflected by the reflecting portion toward the light receiving element for detecting the synchronous light.

The reflecting portion may be provided on the optical deflector side of the lens forming the reflecting portion or on the scanned surface side (claim 2).

The reflection portion may be formed as a "reflection film" on the "portion of the surface to be scanned that does not contribute to the optical scanning", but reflection using "total reflection" without forming a reflection film. It can be a department.

That is, the reflecting portion is formed on the "scanned surface side",
The angle of incidence of the deflected light beam on the reflection part: ψ should satisfy the condition: (I) ψ> sin ~ ¹ (1 / N) for the refractive index of the material of the "lens having the reflection part": N (Claim 3).

The reflecting portion can be formed as a "single reflecting surface", or "a plurality of reflecting surfaces are formed at an angle to each other, and the deflected light flux is sequentially reflected by these reflecting surfaces toward the light receiving element". May be.

In particular, the reflecting portion can be constructed so as to "have two reflecting surfaces for reflecting and deflecting the deflected light beam toward the light receiving element for detecting the synchronous light".

In this case, these two reflecting surfaces are formed on the "scanned surface side", and the incident angles on the two reflecting surfaces are:
ψ ₁ and ψ ₂ are the refractive index of the material of the lens on which the reflection portion is formed: N, the condition is: (II) ψ ₁ > sin ~ ¹ (1 / N) (III) ψ ₂ > sin ~ ¹ ( 1 / N) can be satisfied (Claim 4).

In the optical scanning device according to the above-mentioned claim 1, 2 or 3 or 4, "a reflection part is provided on the optical path of the deflected light beam reflected by the reflection part, between the reflection part and the light receiving element for detecting the synchronous light. A refracting surface for condensing the deflected light flux reflected by the light-receiving element in the vicinity of the light-receiving surface can be formed as a part of the scanning imaging lens (claim 5).

In this case, when the scanning imaging lens is composed of one lens, the above-mentioned "refractive surface" can be provided on the lens surface side of this lens facing the optical deflector.

In the optical scanning device according to the fifth aspect, when the scanning image forming lens is composed of two or more lenses,
Of these, the reflecting portion is formed on the second and subsequent lenses counting from the optical deflector, and the deflected light flux reflected by the reflecting portion is directed to the lens on the optical deflector side of the lens on which the reflecting portion is formed. By the "refractive surface formed as a part of the lens", it is possible to condense light at least in the deflection direction in the vicinity of the light receiving surface of the light receiving element for detecting the synchronous light.

In the invention according to the sixth or seventh aspect, the deflected light beam reflected by the reflecting portion is focused near the light receiving surface of the light receiving element in the deflecting direction by the refracting surface and in the direction orthogonal thereto. It is possible (claim 7).

The shape of the refracting surface is a spherical surface or a coaxial aspherical surface,
Alternatively it can be an anamorphic surface.

In the optical scanning device according to any one of claims 1 to 7, when a laser beam is used as the deflected beam, the "width of the reflection portion in the main scanning corresponding direction" is defined as the beam of the incident deflected beam in the same direction. The width may be smaller than the width, and the light intensity distribution in the main scanning corresponding direction of the reflected light flux toward the light receiving element for detecting the synchronous light may be line-symmetric with respect to the main light ray.

In the optical scanning device according to any one of claims 1 to 8, the scanning image forming lens can have a "function of equalizing the optical scanning speed by the light spot" (claim 9). . That is, if the deflection of the deflected light flux is uniform angular velocity and the deflected light flux incident on the scanning imaging lens is a parallel light flux at least in the main scanning corresponding direction, the scanning imaging lens is an “fθ lens”.

When a "galvano mirror" is used as the light deflector, if the deflected light beam incident on the scanning / imaging lens is a parallel light beam at least in the main scanning corresponding direction, the scanning / imaging lens is "f.sin.theta. Lens". Is.

In the optical scanning device according to any one of claims 1 to 9, a light beam from the light source is transmitted in the vicinity of the deflection reflection surface of the optical deflector in the "main scanning corresponding direction (on the optical path from the light source to the scanned surface). In the direction parallel to the main scanning direction) as a long line image, and as a scanning imaging lens, it is parallel to the sub-scanning direction in the sub-scanning corresponding direction (on the optical path from the light source to the surface to be scanned). (A direction corresponding to each other), the position of the deflecting / reflecting surface and the position of the surface to be scanned have a geometrically-optically substantially conjugate relationship (claim 10).

In this case, the optical scanning device has a function of correcting the “facet tilt” of the deflective reflection surface of the optical deflector.

"Pyramid mirror" and "horizontal mirror"
As described above, when an optical deflector that does not substantially cause a surface tilt is used, the optical scanning device does not need a surface tilt correction function.

A parallel light beam or a convergent or divergent light beam can be incident on the light deflector according to the characteristics of the scanning and imaging lens.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows an embodiment of the invention described in claims 1, 2, 9 and 10. The light beam emitted from the LD 1 is coupled by the coupling lens 2 and then converged by the cylinder lens 3 only in the sub-scanning corresponding direction (the direction orthogonal to the drawing), and the deflecting reflection surface of the polygon mirror 4 serving as an optical deflector. An image is formed as a "long line image in the main scanning corresponding direction" near the position.

The deflected light beam deflected "constantly angularly" by the counterclockwise rotation of the polygon mirror 4 is condensed by the scanning imaging lens 5 as a light spot on the surface 6 to be scanned,
The surface 6 to be scanned is optically scanned. The photoconductive photosensitive drum 7 is in contact with the surface 6 to be scanned at its generatrix, so that the light spot actually optically scans the photosensitive drum 7.

The area indicated by the symbol L is an "optical scanning area" in which optical scanning is performed by a light spot.

The cylinder lens 3 is for forming the above-mentioned "line image" and can be replaced by a concave cylinder mirror.

Depending on the characteristics of the scanning imaging lens 5, the light beam coupled by the coupling lens 2 can be a "parallel light beam" or a "divergent or convergent light beam".

For the sake of concreteness of description, it is assumed in this embodiment that the light beam coupled to the coupling lens 2 is a "parallel light beam". In this case, the scanning and image forming lens 5 is an fθ lens and has a function of making the optical scanning at a constant speed (claim 9), and the deflection reflection surface position (line image forming position) with respect to the sub scanning corresponding direction. The position of the surface to be scanned 6 has a geometrically-optically substantially conjugate relationship (claim 10), and therefore this optical scanning device has a surface tilt correction function.

Of the two lenses 51 and 52 forming the scanning imaging lens, the lens 52 on the surface 6 to be scanned is
A reflecting portion 10 is provided on the scanned surface side of the end portion of the deflection direction where the deflected light flux is received, which portion does not contribute to the optical scanning of the scanned surface, and the deflected light flux toward the optical scanning region L is received for synchronous light detection. The light was reflected toward the element 8.

Therefore, the deflected light flux is received by the light receiving element 8 prior to the optical scanning of the optical scanning area L, and the starting point of the optical scanning is the optical scanning area L based on the light receiving signal emitted by the light receiving element 8 (see FIG. 1).
(At the bottom).

The reflecting portion 10 was formed by depositing a reflecting film.

In the embodiment of FIG. 1, the reflecting portion 10 is provided on the scanned surface 6 side of the lens 52 (claim 2), but it may be provided on the lens 51 or on either of the lenses 51 and 52. In this case also, it may be provided on the optical deflector (polygon mirror 4) side.

The light receiving element 8 for detecting the synchronous light is provided in the housing 9 together with optical elements such as the LD 1, the coupling lens 2, the cylinder lens 3, the polygon mirror 4, and the scanning image forming lens 5. If the deflected light flux that has passed through the scanning and imaging lens 5 is detected as the synchronous light without providing the reflecting portion 10, the light receiving element for detecting the synchronous light (indicated by reference numeral 8A in FIG. 1) is provided on the surface 6 to be scanned. I have no choice but to deploy it in the vicinity,
In this case, the light receiving element 8A cannot be arranged in the same housing 9 as other optical elements such as the LD 1, and if the light receiving element 8A is arranged in the same housing, the housing becomes large.

As in the embodiment shown in FIG. 1, the deflecting light beam detected as the synchronous light is reflected by the reflecting portion 10 so as to be folded back toward the optical deflector, so that the light receiving element 8 is not enlarged in size of the housing 9. Can be compactly arranged in the same housing together with other optical elements, and by arranging the light receiving element 8 and the polygon mirror 4 in the same housing,
The drive circuit for the polygon mirror 4 and the circuit for the light receiving element 8 can be arranged on the "same substrate", and the cost of the optical scanning device can be reduced.

FIG. 2 shows only a characteristic part of one embodiment of the invention according to claim 3. The parts not shown in the figure are similar to those of the embodiment shown in FIG.

In this embodiment, the reflection portion 52a is formed on the surface to be scanned of the lens 52A of the lenses 51 and 52A which form the scanning imaging lens.
The reflecting portion 52a is "planar" and reflects the deflected light beam incident on this portion toward the light receiving element 8 for detecting the synchronous light. However, the incident angle of the deflected light beam to the reflecting portion 52a is ψ. ,
The lens 52A is formed so as to satisfy the condition: (I) ψ> sin ~ ¹ (1 / N) for the refractive index of the material of the lens 52A: N (> 1).

Therefore, the deflected light beam incident on the reflecting portion 52a is totally reflected by the reflecting portion 52a. Therefore, it is not necessary to form a reflection film to provide the reflection portion, and the lens 52
The cost of A can be reduced.

FIG. 3 shows only a characteristic part of one embodiment of the invention described in claim 4. The parts not shown are the same as those in the embodiment of FIG.

Of the two lenses constituting the scanning image forming lens, the end of the side of the lens 52B on the surface to be scanned that receives the deflected light beam in the deflection direction is reflected on the portion of the surface to be scanned that does not contribute to optical scanning. The reflecting portion is provided with two reflecting surfaces 52b1 and 52b1 provided on the scanned surface side.
b1 and the incident angles of the deflected light beams on the reflecting surfaces 52b1 and 52b2: ψ ₁ and ψ ₂ are the conditions for the refractive index N of the material of the lens 52B: N: (II) ψ ₁ > sin ~ ¹ (1 / N) (III) ψ ₂ > sin ~ ¹ (1 / N) is satisfied.

Therefore, the deflected light beam entering the reflecting portion is sequentially totally reflected by the reflecting surfaces 52b1 and 52b2 and then enters the light receiving element 8 for detecting the synchronous light.

FIG. 4 shows a first embodiment of the invention according to claims 5 and 7.
Only the characteristic part of the form is shown. The parts not shown are the same as those in the embodiment of FIG.

In this embodiment, of the lenses 52 and 52C constituting the scanning imaging lens, the portion of the end of the lens 52C on the side where the deflected light beam in the deflection direction is received does not contribute to the optical scanning of the surface to be scanned. The reflection portion 52c is formed as a "reflection surface utilizing total reflection" on the surface to be scanned in "" and reflects the deflected light beam toward the light receiving element 8 for detecting the synchronous light.

The deflected light beam reflected by the reflecting portion 52c is emitted from the lens 52C toward the light receiving element 8, that is, "between the reflecting portion 52c and the synchronous light detecting light receiving element 8", and the reflecting portion 52c is formed. A refracting surface 52e for condensing the deflected light flux reflected by the light-receiving element 8 in the vicinity of the light-receiving surface is formed as a part of the lens 52C.

In this embodiment, the deflected light beam incident on the reflecting portion 52c is a light beam which "diverges in the direction corresponding to the sub-scanning" from the origin of the deflection deflected by the polygon mirror 4, and passes through the lens 51, and further the lens. It is transmitted through the incident side lens surface of 52C. However, since the lens surface of the lens 52C on the scanned surface side does not pass through, sufficient converging power does not act on the "direction orthogonal to the deflection direction" of the reflected deflected light beam.

Therefore, the refracting surface 52e having "positive power"
If the shape is a spherical surface or a coaxial aspherical surface, the power in the direction orthogonal to the deflection direction is not sufficient, so that the reflected deflected light beam is reflected by the light receiving surface of the light receiving element 8 as shown in FIG. In the vicinity of 8A, it converges in the deflection direction and forms an image in an elongated oval shape in the direction orthogonal to the deflection direction (vertical direction in the drawing). By thus collecting the reflected light flux in the deflection direction and making it incident on the light receiving element, it is possible to improve the accuracy of the synchronous light detection.

By making the shape of the refracting surface 52e "anamorphic refracting surface shape such that the positive power in the direction orthogonal to the deflecting direction is stronger than the positive power in the deflecting direction", FIG. 4 (c) is obtained. As shown, the deflected light flux reflected by the reflector 52c can be converged in the "deflection direction and the direction orthogonal thereto" in the vicinity of the light receiving surface 8A of the light receiving element (claim 7).

By thus converging the reflected light flux in the vicinity of the light receiving surface 8A in the deflecting direction and the direction orthogonal thereto, even if the polygon mirror 4 is tilted, the incident position on the light receiving surface 8A. Does not fluctuate in the “direction orthogonal to the deflection direction”, so that the synchronization light detection error due to the surface tilt can be completely prevented.

FIG. 5 shows only the characteristic part of the embodiment in which the inventions of claims 5 and 7 are applied to the embodiment shown in FIG.

Lens 52 on the surface to be scanned of the scanning imaging lens
The deflected light flux that has entered the reflecting portion of D is reflected by the reflecting surfaces 52d1, 5d.
The light is sequentially totally reflected by 2d2 and emitted toward the light receiving element 8 via the refracting surface 52f formed on the lens 52D.

By making the shape of the refracting surface 52f a spherical surface or a coaxial aspherical surface, the light flux incident on the light receiving element 8 can be condensed in the vicinity of the light receiving surface in the deflection direction, and the refracting surface 52f has an anamorphic shape. By doing so, the incident light beam can be condensed in the vicinity of the light receiving surface in the deflection direction and the direction orthogonal thereto.

FIG. 6 shows a first embodiment of the invention according to claims 6 and 7.
Only the characteristic part of the form is shown. Among the lenses 51A and 52E forming the scanning imaging lens, the lens 52E which is the second lens counted from the polygon mirror 4 has a lens 52E that is the second lens counted from the polygon mirror 4 and has an end portion on the side to accept the deflected light beam in the deflection direction. The reflective portion 52g is formed by vapor deposition of a reflective film on the "portion of the scanned surface that does not contribute to optical scanning".

On the other hand, to the lens 51A, which is closer to the polygon mirror 4 than the lens 52E, a "portion having a refracting surface 51a" is added as a part of the lens 51A at a position where the deflected light flux reflected by the reflecting portion 52g passes. Has been formed.

The deflected light beam reflected by the reflecting portion 52g is condensed near the light receiving surface of the light receiving element 8 by the positive power of the refracting surface 51a. By making the shape of the refracting surface 51a a spherical surface or a coaxial aspherical surface, the incident light beam to the light receiving element 8 can be condensed in the vicinity of the light receiving surface in the deflection direction, and the refracting surface 51a has an anamorphic shape. The incident light flux can be condensed near the light receiving surface in the "deflection direction and the direction orthogonal thereto".

Since the deflected light flux reflected by the reflecting portion passes through the "portion in which the refracting surface 51a is formed" in the lens 51A, "the one surface is the cylinder surface and the other surface is the spherical surface or the coaxial aspherical surface" of the above portion. In this way, the light flux incident on the light receiving element 8 can be condensed near the light receiving surface in the "deflection direction and the direction orthogonal thereto".

FIG. 7 is a diagram for explaining one embodiment in which the invention described in claim 8 is applied to the embodiment shown in FIG.

Synchronous light detection is performed on the start side of the optical scanning area. However, depending on the position where the reflecting portion 52g is provided and the light receiving element 8 is installed, as shown in FIG.
When the deflected light beam reflected by g is incident on the light receiving element 8, a part (hatched portion) of the light beam incident on the deflective reflection surface of the polygon mirror 4 may be eclipsed by the deflective reflection surface.

When the deflected light flux is a laser light flux, in this case, the light intensity distribution of the deflected light flux reflected by the reflecting portion is eclipsed by the deflective reflection surface, so that the principal ray (as shown in FIG. It becomes asymmetric with respect to the position 0 in the figure), and this asymmetry of the light intensity causes the detection error of the synchronous light.

Therefore, according to the invention of claim 8, the reflecting portion 5 is provided.
The width F in the deflection direction of 2 g was set to be smaller than the light flux width of the incident deflected light flux incident on the reflecting portion. In this way, the light intensity distribution in the deflection direction of the reflected light flux toward the light receiving element for synchronous light detection is shown in FIG. As shown in c), it can be made “axisymmetric with respect to the principal ray”, and it is possible to effectively prevent detection error of the synchronous light due to the asymmetry of the light intensity distribution.

In the embodiment shown in FIGS. 6 and 7, the reflecting portion may be provided on the side of the optical deflector. When the reflecting portion is provided on the scanned surface side, the reflecting portion "uses total reflection of one or more surfaces. Reflective surface ".

The "portion functioning as the scanning imaging lens" of the lens 51A is the same as the lens 51, and the "portion functioning as the scanning imaging lens" of the lenses 52A, 52B, 52C, 52D and 52E is the lens 52. Is the same as. The scanning / imaging lens may be composed of three or more lenses.

Further, the lenses 51A, 52A, 52B, 52
The C, 52D, 52E and the lens 51 can be easily manufactured by molding using plastic.

[0065]

As described above, according to the present invention, in the optical scanning device, the compact arrangement of the optical system including the light receiving element for detecting the synchronous light can be made possible, and the light receiving element can be provided. It can be compactly deployed in the same housing with other optical elements.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the invention described in claims 1, 2, 9 and 10.

FIG. 2 is a diagram for explaining an embodiment of the invention according to claim 3;

FIG. 3 is a diagram for explaining an embodiment of the invention according to claim 4;

FIG. 4 is a diagram for explaining one embodiment of the invention according to claims 5 and 7;

FIG. 5 is a diagram for explaining another embodiment of the invention according to claims 5 and 7;

FIG. 6 is a diagram for explaining one embodiment of the invention according to claims 6 and 7;

FIG. 7 is a diagram for explaining one embodiment of the invention according to claim 8;

[Explanation of symbols]

 4 Polygon Mirror 5 Scanning Imaging Lens 6 Scanned Surface 8 Synchronous Light Detection Light-Receiving Element 10 Reflector

Claims (10)

[Claims] 1. An optical scanning device for converging a deflected light beam deflected by an optical deflector having a deflecting / reflecting surface as a light spot on a surface to be scanned by a scanning imaging lens and optically scanning the surface to be scanned. The scanning / imaging lens is composed of one or more lenses, and does not contribute to the optical scanning of the surface to be scanned at the end of one of the lenses constituting the scanning / imaging lens on the side where the deflected light flux in the deflection direction is received. An optical scanning device characterized in that a reflecting portion is provided in a portion thereof, and a deflected light flux heading for an optical scanning region is reflected toward a light receiving element for detecting synchronous light. 2. The optical scanning device according to claim 1, wherein the reflecting portion is provided on the surface to be scanned of the lens. 3. The optical scanning device according to claim 2, wherein the incident angle of the deflected light beam to the reflecting portion: ψ is a condition with respect to the refractive index N of the material of the lens on which the reflecting portion is formed: N. An optical scanning device characterized by satisfying ψ> sin ¹ (1 / N). 4. The optical scanning device according to claim 2, wherein the reflecting portion has two reflecting surfaces for reflecting the deflected light beam back toward the light receiving element for detecting the synchronous light. Sequential incident angles of ψ ₁ , ψ ₂ are relative to the refractive index of the material of the lens on which the reflection part is formed: N: (II) ψ ₁ > sin ~ ¹ (1 / N) (III) ψ An optical scanning device characterized by satisfying ₂ > sin- ¹ (1 / N). 5. The optical scanning device according to claim 1, 2 or 3 or 4, wherein, on the optical path of the deflected light flux reflected by the reflecting portion, between the reflecting portion and the light receiving element for detecting the synchronous light, Optical scanning, characterized in that a refracting surface for converging the deflected light beam reflected by the reflecting portion in the vicinity of the light receiving surface of the light receiving element is formed at least as a part of the scanning imaging lens. apparatus. 6. The optical scanning device according to claim 5, wherein the scanning image forming lens is composed of a plurality of lenses, and among these, the second and subsequent lenses counted from the optical deflector have a reflecting portion. The deflected light beam reflected by the reflector is received by the light receiving element for synchronous light detection by the refracting surface formed as part of the lens on the lens on the optical deflector side of the lens on which the reflector is formed. An optical scanning device characterized in that light is condensed in the vicinity of a surface in at least a deflection direction. 7. The deflected light beam reflected by the reflecting portion is condensed in the vicinity of the light receiving surface of the light receiving element in the deflecting direction and in the direction orthogonal thereto by the action of the refracting surface, according to claim 5 or 6. Characteristic optical scanning device. 8. The optical scanning device according to any one of claims 1 to 7, wherein the deflected light beam is a laser light beam, and the width of the reflecting portion in the deflection direction is smaller than the light beam width of the incident deflected light beam in the same direction. An optical scanning device characterized in that a light intensity distribution in a deflection direction of a reflected light beam toward a light receiving element for detecting synchronous light is line-symmetric with respect to a principal ray. 9. The optical scanning device according to any one of claims 1 to 8, wherein the scanning imaging lens has a function of equalizing the optical scanning speed of the light spot. . 10. The optical scanning device according to any one of claims 1 to 9, wherein a light beam from the light source is formed as a long line image in the main scanning corresponding direction in the vicinity of the deflection reflection surface of the optical deflector. An optical scanning device, wherein the scanning imaging lens has a deflection reflection surface position and a scanned surface position in a geometrically-optically substantially conjugate relationship with respect to a sub-scanning corresponding direction.