JP3214944B2 - Optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly, to a method in which a deflecting light beam deflected by a deflecting means having a deflecting / reflecting surface rotating at a constant speed is scanned on a surface to be scanned by an image forming operation of a reflection image forming element. The present invention relates to an optical scanning device that converges light beams as light spots and performs substantially constant-speed scanning. INDUSTRIAL APPLICABILITY The present invention can be used for a writing optical system in a digital copying machine, an optical printer, and the like, and a scanning optical system in a measuring machine, a display, and the like.

[0002]

2. Description of the Related Art As an optical system for condensing a deflected light beam as a light spot on a surface to be scanned in an optical scanning apparatus, an "fθ lens" has been widely known. (An optical element having a function of reflecting a deflected light beam and condensing it as a light spot on a surface to be scanned, which is referred to as a reflection imaging element in this specification) is intended. For example, JP-A 1-220
221). It has also been proposed to make the mirror surface shape of the "reflection imaging element in place of the fθ lens" an aspherical surface shape and satisfactorily correct field curvature and linearity.

In an optical scanning device using such a reflective imaging element, the deflected light beam deflected by the deflecting means is turned back to the deflecting means by the reflective imaging element. "Optical path separating means" for separating an optical path from the reflective imaging element toward the surface to be scanned is required.

One of the means for separating the optical path is, for example, "a light beam is incident from a direction inclined with respect to the rotation axis of the deflecting / reflecting surface of the deflecting means, and the direction of the deflecting light beam is from a plane perpendicular to the rotation axis. To make it lean. " By doing so, the direction of the deflected light beam incident on the reflective imaging element is separated from the direction of the reflected light beam, so that the optical path of the incident deflected light beam and the optical path of the reflected light beam can be separated. However, when the optical path separation is performed only by the above means, in order to make the layout of each optical element possible, the angle of the incident light beam with respect to the deflecting / reflecting surface must be increased to some extent with respect to the plane, and the angle is large. If so, a large bend occurs in the “trajectory of the light spot on the surface to be scanned”, that is, the “scanning line”, which hinders good optical scanning.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has as its object to provide a novel optical scanning device that performs refraction or optical path separation by refraction and reflection. Another object of the present invention is to provide a novel optical scanning device capable of effectively correcting the bending of a scanning line due to the optical path separation. Another object of the present invention is to provide an optical scanning device having "a function of correcting a surface tilt of a deflecting reflection surface in a deflecting means" in addition to achieving the above objects.

[0006]

According to the optical scanning apparatus of the present invention, a light beam from a light source is deflected by a deflecting means having a deflecting / reflecting surface which rotates at a constant speed, and the deflecting light beam is made incident on a reflection / imaging element. An apparatus that converges the light beam reflected by the imaging element as a light spot on the surface to be scanned by the imaging operation of the reflection imaging element to perform substantially constant speed optical scanning.

As described above, the "deflecting means" deflects a deflected light beam, and specifically includes a pyramidal mirror,
Mortise mirror, rotating polygon mirror, etc.

According to a first aspect of the present invention, a light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting and reflecting surface rotating at a constant speed, and the deflected light beam is deflected with respect to the beam deflecting surface. The reflected light beam from the reflective imaging element is reflected by the half mirror, and is collected as a light spot on the surface to be scanned by the reflective imaging element. An apparatus for performing optical scanning by light, wherein a "reflection imaging element" has a function of performing optical scanning with a light spot at a substantially constant speed, and bends a scanning line on a surface to be scanned. In order to perform the correction, the reflective imaging element is arranged so as to be shifted by a predetermined “shift amount” in a direction orthogonal to the “beam deflecting surface”.

The "beam deflection surface" is defined in the present invention as follows. As described above, in the optical scanning device according to the present invention, the deflecting unit that deflects the light beam has the deflecting / reflecting surface that rotates at a constant speed. The light beam from the light source is reflected by the deflecting / reflecting surface, and the reflected light beam is deflected by rotation of the deflecting / reflecting surface.

Therefore, the incident position of the principal ray in the light beam incident on the deflecting reflection surface in the state where the image spot of the light spot condensed on the surface to be scanned is “0” is defined as “incident reference position”.
A “plane that passes through the incident reference position and is orthogonal to the rotation axis of the deflecting / reflecting surface (ideal rotation axis that does not take into account the shaft runout)” is defined as the beam deflecting surface. The “shift amount” means a distance between an intersection (referred to as a center point of the reflection imaging element) between the optical axis of the reflection imaging element and the reflection surface and the beam deflection surface.

According to a second aspect of the present invention, a light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting reflection surface rotating at a constant speed, and the deflected light beam is deflected with respect to the beam deflecting surface. The reflected light beam from the reflective imaging element is reflected by the half mirror, and is collected as a light spot on the surface to be scanned by the reflective imaging element. A device that performs optical scanning by light, wherein the reflective imaging element has a function of performing optical scanning with a light spot at a substantially constant speed, and corrects the bending of the scanning line on the surface to be scanned. For this purpose, the reflective imaging element is characterized in that “the optical axis is arranged so as to be inclined by a predetermined tilt amount with respect to the beam deflecting surface”. The “tilt amount” is an angle between the optical axis of the reflective imaging element and the beam deflecting surface as described above.

In the optical scanning device according to the first and second aspects, the "half mirror" may be configured such that one surface (either surface) is a semi-transparent mirror, or the semi-transparent mirror surface is formed on both sides. May be sandwiched between transparent parallel plates.

According to a third aspect of the present invention, there is provided an optical scanning apparatus comprising: a light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting / reflecting surface which rotates at a constant speed; The light is transmitted through the inclined half mirror to be incident on the reflection imaging element, and the light beam reflected by the reflection imaging element is reflected by the half mirror, and is condensed as a light spot on the surface to be scanned by the imaging operation of the reflection imaging element. A device for performing optical scanning by causing a reflective imaging element to perform optical scanning with a light spot at a substantially constant speed, and a "half mirror for semi-transmitting a surface on the deflecting means side". Mirror surface ".

In the optical scanning device according to the third aspect, in order to correct the bending of the scanning line on the surface to be scanned,
It may be arranged such that "the reflective imaging element is arranged with a predetermined shift amount in a direction orthogonal to the beam deflecting surface" (claim 4). In such a manner as to be tilted by a predetermined tilt amount "(claim 5).

In the optical scanning device according to the second or fifth aspect, in order to correct the bending of the scanning line on the surface to be scanned, the optical axis of the reflection image forming element is tilted by a predetermined tilt amount with respect to the beam deflection surface. Tilt and dispose the reflective imaging element with a predetermined shift amount in a direction perpendicular to the beam deflecting surface. " That is, in order to correct the bending of the scanning line, "tilting the reflective imaging element with respect to the beam deflecting surface" and "displacing the reflective imaging element from the beam deflecting surface" can be used in common.

According to the optical scanning device described in any one of the first to sixth aspects, "the deflecting means has a deflecting / reflecting surface parallel to the rotation axis, and the deflecting means includes a deflecting means. The deflecting reflection surface position and the surface to be scanned are geometrically conjugated in the sub-scanning direction, and the light beam from the light source is transmitted in the sub-scanning direction (the optical path from the light source to the surface to be scanned is the optical axis). Direction on the virtual optical path developed linearly along the sub scanning direction)
, An image is formed in the vicinity of the deflecting reflection surface as a long line image in the main scanning corresponding direction (in the virtual optical path, a direction corresponding to the main scanning direction in parallel). '' Item 7).

According to another aspect of the present invention, a light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting / reflecting surface that rotates at a constant speed, and the deflecting light beam is an anamorphic reflective imaging element. And a device for performing optical scanning by converging a reflected light beam as a light spot on a surface to be scanned by an image forming operation of a reflective image forming device, wherein the reflective image forming device performs optical scanning by a light spot. And a transparent parallel plate is disposed between the deflecting means and the reflective imaging element so as to be inclined by a finite inclination angle with respect to the rotation axis of the deflecting means. The optical path from the deflecting means to the reflective imaging element and the optical path from the reflective imaging element to the surface to be scanned are separated, and the material, thickness, and tilt angle of the parallel plate are corrected for the bending of the scanning line. The feature is that it is determined that The angle ", as described above, mutually parallel surfaces of the parallel plate is an angle with respect to the rotational axis of the deflecting means. The fact that the parallel flat plate is “transparent” means that it is transparent to a light beam used for optical scanning, and does not necessarily need to be transparent to light in all wavelength regions.

In the optical scanning device according to the eighth aspect, it is also possible that "the deflected light beam incident on the reflection imaging element and the light beam reflected by the reflection imaging element both pass through the parallel flat plate". (Claim 9), "Only the deflected light beam incident on the reflective imaging element among the deflected light beam incident on the reflective imaging element and the reflected light beam from the reflective imaging element is transmitted through the parallel flat plate". Often (claim 10), in the optical scanning device according to claims 8 to 10, "the tilt angle of the parallel plate is determined so that the incident angle of the deflected light beam incident on the parallel plate substantially satisfies the Brewster angle. (Claim 11).

In the optical scanning device according to the ninth aspect, both the deflected light beam and the reflected light beam pass through the parallel flat plate. In this case, "a reflective film is formed on a part of the surface of the parallel flat plate on the deflection means side. Then, only the reflected light flux reflected by the reflective imaging element and transmitted through the parallel plate is selectively reflected by the reflective film.

In the optical scanning device according to the tenth aspect, the light beam reflected by the reflective imaging element may be guided to the surface to be scanned as it is, but may be reflected on a part of the surface of the parallel plate on the reflective imaging element side. A film may be formed, and only the reflected light beam reflected by the reflective imaging element may be selectively reflected by the reflective film.

According to a fourteenth aspect of the present invention, there is provided an optical scanning device according to any one of the eighth to thirteenth aspects, wherein the deflecting means has a deflecting / reflecting surface parallel to the rotation axis. The light flux from the light source is formed as a long line image in the main scanning corresponding direction in the vicinity of the deflecting / reflecting surface, and the position of the deflecting / reflecting surface and the position of the surface to be scanned are related to the sub-scanning corresponding direction by the reflective imaging element. It is made to have a substantially conjugate relationship in geometrical optics. "

According to a fifteenth aspect of the present invention, there is provided an optical scanning device comprising: a light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means; a deflected light beam is reflected by a reflection imaging device; A device that performs light scanning by condensing light as a light spot on a surface to be scanned by the image forming function, wherein the reflective imaging element has a function of performing light scanning by the light spot at a substantially constant speed. A long prism having a wedge-shaped cross section is provided between the deflecting means and the reflective imaging element in parallel with the main scanning direction, and an optical path from the deflecting means to the reflective imaging element; The optical path from the element to the surface to be scanned is separated. "

In this case, in order to correct the bending of the scanning line, it is possible to "deploy the reflective imaging element with a predetermined shift amount in a direction orthogonal to the beam deflecting surface".
6) Or, "the reflective imaging element is arranged so that its optical axis is inclined by a predetermined tilt amount with respect to the beam deflecting surface."
(Claim 17). Further, in the optical scanning device according to the sixteenth aspect, it is possible to "the reflective surface shape of the reflective imaging element is a coaxial spherical or aspherical surface" (claim 18).

Further, claim 15 or 16 or 17
In the optical scanning device described above, `` a device having a deflecting / reflecting surface parallel to the rotation axis is used as the deflecting means, and the deflecting / reflecting surface position of the deflecting means and the surface to be scanned are anamorphically scanned in the sub-scanning direction. By using one having a geometrically conjugate relationship in the corresponding direction, the light beam from the light source is formed as a long line image in the main scanning corresponding direction near the deflecting reflection surface. " 19).

According to a twentieth aspect of the present invention, there is provided an optical scanning device comprising: a light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting / reflecting surface which rotates at a constant speed; And a light beam is condensed as a light spot on the surface to be scanned by the image forming function of the reflection image forming element, thereby performing light scanning. It has the function of performing substantially constant speed, and `` provided between the deflecting means and the reflective imaging element, a transparent parallel flat plate is arranged so as to be inclined by a finite inclination angle with respect to the rotation axis of the deflecting means. The optical path from the deflecting means to the reflective imaging element and the optical path from the reflective imaging element to the surface to be scanned are separated, and the reflective imaging element is tilted by a predetermined tilt amount with respect to the beam deflecting surface. Material, thickness, tilt angle, reflection imager The inclination angle of relative to the beam deflecting surface,
It has been determined that the curvature of the scanning line is corrected ".

In the optical scanning device according to the twentieth aspect, it is also possible that "the deflected light beam incident on the reflection imaging element and the light beam reflected by the reflection imaging element both pass through the parallel flat plate". (Claim 21), "Of the deflected light flux incident on the reflection imaging element and the reflection light flux by the reflection imaging element,
Only the deflected light beam incident on the reflective imaging element may pass through the parallel flat plate ”(claim 22). Further, in the optical scanning device according to any one of claims 20 to 22,
"The tilt angle of the parallel plate is determined so that the angle of incidence of the deflected light beam incident on the parallel plate satisfies the Brewster angle."
(Claim 23).

In the optical scanning device according to the twenty-first aspect, both the light incident on the reflection imaging element and the light beam reflected by the element transmit through the parallel flat plate. A reflection film may be formed on a part, and only the reflected light beam reflected by the reflection imaging element and transmitted through the parallel flat plate is selectively reflected by the reflection film. In the optical scanning device according to claim 22, the light beam reflected by the reflective imaging element may be directly guided to the surface to be scanned. And only the reflected light flux reflected by the reflective imaging element is selectively reflected by the reflective film "(claim 25).

According to a twenty-sixth aspect of the present invention, in the optical scanning device according to the twentieth to twenty-fifth aspects, "the deflecting means uses a deflecting means having a deflecting and reflecting surface parallel to the rotation axis,
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 deflecting / reflecting surface, and the position of the deflecting / reflecting surface and the position of the surface to be scanned are changed with respect to the sub-scanning corresponding direction by the reflective imaging element. It is made to have a substantially conjugate relationship in geometrical optics. "

As described above, in the optical scanning device according to any one of the first to twenty-sixth aspects, the deflection of the light beam by the deflecting means is performed "in a plane". That is, the surface on which the principal ray of the deflected light beam ideally deflected by the deflector is swept with the deflection is a plane orthogonal to the rotation axis of the deflective reflection surface, and this surface coincides with the “beam deflection surface”. I do.

The optical scanning device according to any one of claims 27 to 35,
`` The light beam from the light source is deflected by a deflecting means having a deflecting / reflecting surface rotating at a constant speed, the deflected light beam is reflected by an anamorphic reflection imaging element, and the reflected light beam is scanned by the imaging action of the reflection imaging element. An apparatus for performing optical scanning by condensing light as a light spot on a surface ", wherein the reflective imaging element has a function of performing optical scanning by the light spot at a substantially constant speed.

According to a twenty-seventh aspect of the present invention, a transparent parallel plate is disposed between the deflecting means and the reflective imaging element so as to be inclined by a finite inclination angle with respect to the rotation axis of the deflecting means. At the same time, the incident light beam is incident on the deflecting / reflecting surface of the polarization means at an angle to the beam polarization plane, thereby separating the optical path from the deflecting means to the reflective imaging element and the optical path from the reflective imaging element to the surface to be scanned. The material, thickness, tilt angle, and amount of light beam shift of the deflected light beam with respect to the reflective imaging element are determined so as to correct the bending of the scanning line. "

The intersection of the reflection surface of the reflection imaging element and the optical axis of the reflection imaging element is called the center of the reflection imaging element. When the image height of the light spot on the non-scanning surface is 0, the deflected light flux The distance between the position at which the principal ray of light enters the reflecting surface and the central portion is referred to as the "ray shift amount".

According to a twenty-eighth aspect of the present invention, in the optical scanning device, a transparent parallel flat plate is disposed between the deflecting means and the reflective imaging element so as to be inclined by a finite inclination angle with respect to the rotation axis of the deflecting means. In addition, by making the incident light flux incident on the deflection reflecting surface of the polarizing means obliquely with respect to the beam polarizing surface,
The optical path from the deflecting means to the reflective imaging element is separated from the optical path from the reflective imaging element to the surface to be scanned, and the reflective imaging element is tilted so that its optical axis is tilted by a predetermined tilt with respect to the beam deflection surface. And the material, thickness, tilt angle, and tilt amount of the reflective imaging element of the parallel plate are determined so that the scanning line bend is corrected. "

In the optical scanning device according to the twenty-seventh aspect, "the reflective imaging element is provided so that its optical axis is inclined by a predetermined tilt angle with respect to the beam deflecting surface.
The thickness, the tilt angle, the amount of light shift, and the amount of tilt can be determined so as to correct the bending of the scanning line ”(claim 29).

In the optical scanning device according to the twenty-seventh, twenty-eighth, or thirty-ninth aspects, "the deflected light beam incident on the reflective imaging device and the reflected light beam reflected by the reflective imaging device both pass through the parallel flat plate". (Claim 30),
Alternatively, of the deflection light beam incident on the reflection imaging element and the reflection light beam reflected by the reflection imaging element, only the deflection light beam incident on the reflection imaging element may pass through the parallel flat plate. 31). Furthermore, in the optical scanning device according to the twenty-seventh to thirty-first aspects, it is also possible to "determine the inclination angle of the parallel plate so that the incident angle of the deflected light beam incident on the parallel plate satisfies the Brewster angle" ( Claim 3
2).

[0036] In the optical scanning device according to the thirtieth aspect,
"A reflective film is formed on a part of the plane of the parallel plate on the side of the deflecting means, and only the reflected light flux reflected by the reflective imaging element and transmitted through the parallel plate is selectively reflected by the reflective film."
Alternatively, a reflective film may be formed on a part of the surface of the parallel plate on the side of the reflective imaging element, and only the reflected light beam reflected by the reflective imaging element may be selectively reflected. (Reflected by the film) (claim 34).

Further, in the optical scanning device according to the present invention, the deflecting means having a deflecting / reflecting surface parallel to the rotation axis is used, and the light beam from the light source is mainly located near the deflecting / reflecting surface. An image is formed as a long line image in the scanning corresponding direction, and the position of the deflecting / reflecting surface and the position of the surface to be scanned have a geometrically optically conjugate relationship with respect to the sub-scanning corresponding direction by the reflective imaging element. " (Claim 35).

In the optical scanning device according to claims 27 to 35,
The light beam is incident on the deflecting and reflecting surface of the deflecting means at an angle to the beam deflecting surface. Therefore, at this time, the surface on which the principal ray of the deflected light beam ideally deflected sweeps has a curved surface like a “conical surface”.

[0039]

When a reflective imaging element is arranged with the optical axis coincident with the beam deflecting surface, and a half mirror is arranged between these deflecting means and the reflective imaging element with an inclination with respect to the beam deflecting surface,
Due to the “thickness” of the half mirror, the deflected light beam transmitted through the half mirror is shifted in a direction orthogonal to the beam deflection surface. For this reason, the position of incidence of the deflected light beam on the reflective imaging element is deviated from the optical axis, and this causes "bending of the trajectory of the light spot".

In the optical scanning device according to the first to seventh aspects, as shown in each of the specific examples described later, the reflection imaging element is "shifted" in a direction orthogonal to the beam deflecting surface, or the reflection imaging element is "Tilt" the optical axis with respect to the beam deflection surface
In addition, by arranging such that “the semi-transparent mirror surface of the half mirror is positioned on the deflection unit side”, it is possible to effectively correct the curvature of the “scanning line” that is the trajectory of the light spot.

Further, in the optical scanning device according to the present invention, a parallel flat plate is provided between the deflecting means and the reflective imaging element, and at least the deflecting light beam by the deflecting means is incident upon the reflective imaging element. It passes through the parallel plate beforehand. By adjusting the material and thickness of the parallel plate and the tilt angle with respect to the rotation axis of the deflecting means as shown in each embodiment described later, it is possible to effectively correct the scan line bending.

In the optical scanning device according to the fifteenth aspect, a long prism is provided between the deflecting means and the reflective imaging element, and the direction of the deflected light beam is inclined with respect to the beam deflection surface due to refraction. Since both the direction of incidence on the imaging element and the direction of reflection by the same element are inclined with respect to the beam deflection surface,
Good optical path separation can be performed. In the optical scanning device according to claims 16 to 19, as shown in each specific example described later, the reflection imaging element is "shifted" in a direction orthogonal to the beam deflecting surface, or the optical axis of the reflection imaging element is changed by the beam. By arranging it “tilted” with respect to the deflecting surface, it is possible to effectively correct the curvature of the “scanning line” that is the trajectory of the light spot.

Further, in the optical scanning device according to the twentieth to twenty-sixth aspects, a parallel plate is provided between the deflecting means and the reflective imaging element, and at least the deflecting light beam by the deflecting means is incident upon the reflective imaging element. It passes through the parallel plate beforehand. Further, the reflection imaging element is inclined with respect to the beam deflection surface. As shown in each embodiment described later, by adjusting the material and thickness of the parallel plate, the tilt angle with respect to the rotation axis of the deflecting means, and the tilt angle of the reflective imaging element with respect to the beam deflecting surface,
It is possible to effectively correct the scan line bending.

Further, in the optical scanning device according to the present invention, a parallel plate is provided between the deflecting means and the reflective imaging element, and at least the deflecting light beam by the deflecting means is incident upon the reflective imaging element. It passes through the parallel plate beforehand. The light beam incident on the deflecting reflecting surface is inclined with respect to the beam deflecting surface.

The amount of light beam shift of the deflected light beam with respect to the reflection imaging element and / or the amount of tilt of the reflection imaging element are adjusted together with the material and thickness of the parallel plate and the inclination angle with respect to the rotation axis of the deflection means. " Can be effectively corrected.

As in the optical scanning device according to the seventh aspect, "a deflection means having a deflecting / reflecting surface parallel to the rotation axis is used, and a light beam from a light source is main-scanned in the vicinity of the deflecting / reflecting surface. The image should be formed as a long line image in the corresponding direction, and the position of the deflecting / reflecting surface of the deflecting means and the position of the surface to be scanned should be geometrically conjugated with respect to the sub-scanning corresponding direction by the reflective imaging element. " Thereby, "surface tilt" of the deflecting reflection surface can be corrected. As can be seen from each specific example, since the shift amount and the tilt amount of the reflection imaging element are both small, the position of the deflecting reflection surface of the deflecting means and the position of the surface to be scanned can be more accurately adjusted by the reflection imaging element with respect to the sub-scanning corresponding direction. Can have a conjugate relationship.

If the relationship with the light source is devised, the above-mentioned surface tilt can be corrected even when using a deflecting means (such as a pyramidal mirror) in which the deflecting / reflecting surface is inclined at 45 degrees with respect to the rotation axis. Is possible.

[0048]

FIG. 1A schematically shows only an essential part of an example of an optical scanning apparatus to which the inventions of claims 1 to 7 can be applied. The light source denoted by reference numeral 1 in the drawing is an LD, an LED, or the like. The luminous flux emitted from the light source 1 is suppressed from diverging by the lens 2 having a positive power. When the luminous flux passes through the lens 2, it becomes either a parallel luminous flux, a convergent luminous flux, or a divergent luminous flux. The convergence tendency is given only in the sub-scanning corresponding direction, and an image is formed as a "long line image in the main scanning corresponding direction" near the deflecting reflection surface of the deflecting means 4 which is a "mortise mirror".

The "mortise type mirror" serving as the deflecting means 4 forms a so-called "mortise" at the top of the rotation axis, the surface of the "mortise" parallel to the rotation axis is a deflecting reflection surface, and the rotation axis is a motor. It is designed to rotate. The luminous flux from the light source 1 side is such that the principal ray is incident on the deflecting / reflecting surface at "in a plane perpendicular to the rotation axis" of the deflecting means 4, and is therefore deflected by the deflecting means 4 at a constant angular velocity. The plane on which the principal ray of the deflected light beam sweeps is orthogonal to the rotation axis and coincides with the “beam deflection plane”.

The deflected light beam deflected at a constant angular velocity by the deflecting means 4 is transmitted through the half mirror 5 and is incident on a reflection imaging element 6 which is a concave mirror. And irradiates the surface of the recording medium 7. This illuminating light beam is condensed as a light spot on the peripheral surface of the recording medium 7 by the action of the reflective imaging element 6.
The light spot follows the deflection of the deflected light beam and "ideally" optically scans on the optical scan line L. Therefore, the scanning line ideally matches the optical scanning line L, but actually bends and deviates from the optical scanning line L. The tangential plane on the peripheral surface of the recording medium 7 that includes the optical scanning line L is the “scanned surface”.

The reflection image forming element 6 has a function of condensing the deflected light beam onto a light spot on the surface to be scanned, and makes the light scanning by the light spot substantially uniform (shift of the light spot from the constant speed light scanning). (To such an extent that optical scanning errors due to the above can be corrected by electrical signal processing). Further, as described above, the light beam incident on the deflecting means 4 forms an image near the deflecting and reflecting surface as a long linear image in the main scanning corresponding direction. The position of the surface to be scanned is set as a geometric optical conjugate relationship. That is, the imaging function of the reflective imaging element 6 differs in the main scanning corresponding direction and the sub-scanning corresponding direction, and the reflective imaging element 6 is “anamorphic”.

The reflection imaging element 6 has the following mirror surface shape. That is, the optical axis of the reflective imaging element (the axis of symmetry of the mirror surface)
And a straight line orthogonal to the optical axis and parallel to the main scanning direction (referred to as a main symmetry plane), the mirror surface of the reflective imaging element 6 has coordinates in the optical axis direction: X, Assuming that the coordinates in the direction perpendicular to the optical axis with the optical axis position as the origin are: Y, the general formula is expressed by Y ² = 2R _m X− (K + 1) X ² (R _m : radius of curvature on the optical axis, K: conical constant). It has the shape to be made. The three-dimensional shape of the mirror surface is
The “concave barrel-shaped surface” formed by rotating the above-described shape with the “axis that is separated from the mirror surface by R _s on the optical axis and orthogonal to the optical axis in the main symmetry plane” as a rotation axis. Therefore, the reflective imaging element 6
Is determined by three parameters “R _m , R _s , K”. In addition, that the mirror surface of the reflective imaging element has a shape represented by the above general formula means that the shape of the mirror surface is substantially represented by the above general formula.

FIG. 1B shows the first embodiment of the present invention.
An embodiment applied to the optical scanning device of FIG. In this case, the beam deflecting surface indicated by the symbol BS coincides with a virtual plane swept by the principal ray of the deflected light beam ideally deflected by the deflecting means 4.

The half mirror 5 provided between the deflecting means 4 and the reflection imaging element 6 has a surface 5b on the reflection imaging element 6 side which is a "semi-transparent mirror surface" and is inclined with respect to the beam deflection surface BS. Provided. The deflected light beam passes through the half mirror 5 and is reflected by the reflective imaging element 6 so that the surface 5b of the half mirror 5
The light is reflected by the semi-transparent mirror surface formed on the recording medium 7 and condensed on the recording medium 7 as a light spot.

In the embodiment shown in FIG. 1B, the optical axis AX of the reflection imaging element 6 is parallel to the beam deflection surface BS, and the entire reflection imaging element 6 is shifted in a direction perpendicular to the beam deflection surface BS. : Shifted by ΔZ. In this case, since the optical axis AX of the reflective imaging element is parallel to the beam deflecting surface BS, the shift amount: ΔZ is the shift amount of the optical axis AX with respect to the beam deflecting surface BS. The upper side of the surface BS is defined as +.

The three parameters for determining the mirror surface shape of the reflection imaging element 6 are R _m = −277 mm and R _s = −.
A mirror having a refractive index of n = 1.51118 and a thickness of t = 7 mm is used as the half mirror 5 as the half mirror 5. Angle of inclination of the half mirror 5 with respect to the beam deflection surface BS: α (the angle between the normal to the surface 5a (which is parallel to the surface 5b) and the beam deflection surface BS) =
Deploy at 45 degrees. From the deflecting / reflecting surface 4a to the reflective imaging element 6
Distance: L ₀ = 87.42 mm, light scanning width: S
= 216 mm.

In this case, the shift amount of the reflective imaging element 6 is Δ
Assuming that Z is 0, the bending of the scanning line due to the light spot is as shown in FIG. That is, the bending of the scanning line is
There is almost no problem in the vicinity of the central portion of the optical scanning region, but it becomes extremely large at both ends of the optical scanning region, preventing proper optical scanning.

Example 1 Using the above-mentioned half mirror and reflective imaging element, FIG.
As shown in (B), the reflective imaging element 6 is arranged so as to be shifted by a shift amount ΔZ in a direction orthogonal to the same surface BS. When the shift amount: ΔZ = −0.36 mm, the bending of the scanning line was suppressed to a relatively small value over the entire optical scanning region as shown in FIG. 2B, and was corrected well.

FIG. 1C shows the second embodiment of the present invention.
An embodiment applied to the optical scanning device of FIG. The position of the intersection of the optical axis AX and the mirror surface of the reflective imaging element 6 is on the beam deflection surface BS, and the optical axis AX is inclined with respect to the beam deflection surface BS by a tilt amount: Δθ.
The tilt amount: Δθ is + when the mirror surface of the reflection imaging element 6 is rotated clockwise.

Example 2 The same half mirror and reflective imaging element as in Example 1 were tilted at an inclination angle α = 45 degrees and a distance L ₀ = 87.42.
mm, the optical scanning width: S = 216 mm, and the tilt amount of the reflective imaging element 6 was set to Δθ = −0.22 degrees. The bending of the scanning line was as shown in FIG. 2C. As in the case of the specific example 1, the bending of the scanning line was satisfactorily corrected.

Next, as the reflective imaging element 6, three parameters for determining the mirror surface shape are as follows: R _m = −218.6 mm,
R _s = -109.4mm, used as given by K = -1.89, a half mirror 5, the refractive index: n = 1.
51118, thickness: t = 8.4 mm, and the half mirror 5 is tilted with respect to the beam deflection surface BS at an inclination angle: α = 5.
Deploy 6 times. Distance from the deflecting / reflecting surface 4a to the reflective imaging element 6: L ₀ = 66.1 mm, light scanning width: S = 2
16 mm.

In this case, the shift amount from the beam deflecting surface BS of the reflective imaging element 6 is ΔZ = 0, and the tilt amount is Δθ = 0.
Then, the scanning line of the light spot bends as shown in FIG. 3A, and the bending of the scanning line increases sharply from near the center of the light scanning area toward both ends of the light scanning area. Hinder.

Example 3 Under the above conditions, as in Example 1, the amount of shift of the reflective imaging element 6 in the direction orthogonal to the same surface BS: Δ
When shifted by Z = + 0.33 mm, the bending of the scanning line was suppressed to a relatively small value over the entire optical scanning area, as shown in FIG.

Embodiment 4 Under the conditions of Embodiment 3, as in Embodiment 2, the optical axis of the reflective imaging element 6 is tilted with respect to the beam deflecting surface BS by an amount of tilt: Δθ = + 0.17 degrees. As a result, the curvature of the scanning line was as shown in FIG. 3C, and the curvature of the scanning line was corrected well.

In the example described above, the half mirror 5
The surface 5b on the reflective imaging element 6 side is a semi-transparent mirror surface. FIG.
(D) schematically shows only an essential part of an embodiment in which the invention of claim 3 is applied to the optical scanning device of FIG. 1 (A). In the half mirror 5, the surface 5a on the deflecting means 4 side is a semi-transparent mirror surface.
The reflection imaging element 6 is provided so that its optical axis is located within the beam deflection surface BS.

As the reflective image forming element 6, three parameters for determining the mirror surface shape as in the first and second embodiments are Rm = −2.
A half mirror having a refractive index of n = 1.51118 and a thickness of t = 3.5 mm is used as the half mirror 5. The half mirror 5 is arranged at an inclination angle α = 45 degrees with respect to the beam deflection surface BS. The distance from the deflecting / reflecting surface 4a to the reflective imaging element 6 is L ₀ = 87.42 mm, and the light scanning width is S = 216 mm.

Under these conditions, the semi-transparent mirror surface of the half mirror 5 is set to the reflective imaging element 6 side, and the shift amount: ΔZ = 0 and the tilt amount: Δθ = 0.
(A).

Example 5 Under the above conditions, the semi-transparent mirror surface of the half mirror 5 is shown in FIG.
As shown in FIG. 4D, when the scanning line was arranged toward the deflecting means 4, the scanning line bending was improved as shown in FIG. 4B. When the semi-transparent mirror surface of the half mirror is set to the deflecting means side, the deflected light beam passes through the semi-transparent mirror surface and then passes through the half mirror to 3.
As a result, the optical path length can be increased because the optical path in the half mirror becomes longer, but at the same time, as shown in FIG. Occurs.

In this case, as shown in the specific example 5, the bending of the scanning line is improved "without shifting or tilting" the reflective imaging element 6. The correction of “scanning line bending” by turning the semi-transparent mirror surface of the half mirror toward the deflecting means can be shared with the correction by “shift” or “tilt” of the reflective imaging element.

For example, as the reflective imaging element 6, three parameters for determining the mirror shape are as follows: R _m = −252 _m
m, R _s = −96 mm, K = −1.0, and the refractive index: n = 1.51 as the half mirror 5
118, the thickness: t = 3.2 mm, and the semi-transparent mirror half mirror 5 is tilted with respect to the beam deflection surface BS at an inclination angle α
= Deploy at 45 degrees. Distance from the deflecting / reflecting surface 4a to the reflective imaging element 6: L ₀ = 76.5 mm, light scanning width: S
= 216 mm.

Under these conditions, the reflective imaging element 6
When the shift amount of ΔZ = 0, the tilt amount: Δθ = 0, and the semi-transparent mirror surface of the half mirror 5 is on the reflective imaging element 6 side, the scanning line bends as shown in FIG. Become.

Specific Example 6 At this time, when the semi-transparent mirror surface of the half mirror 5 is set to the deflecting means side and the reflection imaging element 6 is shifted by a shift amount ΔZ = + 0.25 mm with respect to the beam deflecting surface, the scanning line The bending is satisfactorily improved as shown in FIG.

Specific Example 7 Under the conditions of the specific example 6, instead of “shifting” the reflection imaging element, even if the reflection imaging element is arranged with a tilt of Δθ = + 0.15 degrees, even if the scanning line is The bending is satisfactorily improved as shown in FIG.

Incidentally, in order to correct the bending of the scanning line,
It is also possible to tilt the reflection imaging element 6 with respect to the beam deflection surface BS and to displace it in a direction perpendicular to the beam deflection surface BS.

FIG. 6A schematically shows only an essential part of an embodiment of the optical scanning device according to the present invention. In order to avoid complication, the same reference numerals as those in FIG.

The luminous flux radiated from the light source 1 is suppressed from diverging by the lens 2 having positive power, and the luminous flux transmitted through the lens 2 is converted into a parallel luminous flux or a condensing light depending on the power and arrangement of the lens 2. Or a divergent light flux. The light beam transmitted through the lens 2 may be any of the above-described parallel light beam, condensed light beam, and divergent light beam. In this example, the light beam is a divergent light beam. The divergent light flux transmitted through the lens 2 is given a tendency to converge only in the sub-scanning corresponding direction by the cylinder lens 3, and is formed near the deflecting reflection surface of the deflecting means 4 as a long line image in the main scanning corresponding direction.

The deflection light beam deflected by the deflection means 4 is
Next, the light enters the reflective imaging element 6 via the parallel plate 5A,
When reflected by the element 6, it becomes a reflected light flux. The reflected light flux is applied to the surface of the recording medium 7, but is condensed as a light spot on the peripheral surface of the recording medium 7 by the operation of the reflection imaging element 6. The light spot optically scans the optical scanning line L "ideally" according to the deflection of the deflected light beam. The scanning line ideally matches the optical scanning line L, but in practice, it generally bends and deviates from the optical scanning line L.

The reflection imaging element 6 is an anamorphic concave mirror 6 similar to that described with reference to FIG. 1A described above, and is a “concave barrel-shaped surface”. Is determined by the three parameters “R _m , R _s , K”.

Further, as described above, the light beam incident on the deflecting means 4 forms an image as a long linear image in the main scanning direction in the vicinity of the deflecting / reflecting surface. The position of the surface and the position of the surface to be scanned have a geometrical conjugate relationship (therefore, this embodiment is also an embodiment of the optical scanning device according to claim 14).

FIG. 6B shows a state where the optical path from the deflecting means 4 of the optical scanning device of FIG. 6A to the recording medium 7 is viewed from the main scanning corresponding direction. Specular shape of the reflective image forming element 6 that appear in Figure radius: an arc of R _s. Reference symbol BS denotes a beam deflecting surface, and reference symbol AX denotes an optical axis of the reflective imaging element 6. The optical axis AX is parallel to the beam deflection surface BS,
Therefore, the tilt amount: Δθ = 0.

The light beam deflected by the deflecting means 4 is parallel plate 5A.
Is transmitted to the reflective imaging element 6, and when reflected by the element 6, the light passes through the parallel flat plate 5A to perform optical scanning of the recording medium 7 (therefore, in this example, the optical scanning apparatus according to claim 9). Is also an example).

FIGS. 7 to 9 show modified examples. In order to avoid complication, the same reference numerals as those in FIG. 6 are used for those which do not seem to be confused. In these modifications, the optical arrangement on the optical path from the light source to the deflecting means is shown in FIG.
In the same manner as in the example described above, the position of the deflecting / reflecting surface and the position of the surface to be scanned are set to “geometrically and substantially conjugate with respect to the sub-scanning corresponding direction” by the reflective imaging element 6. This is the same as the embodiment of FIG.

The embodiment shown in FIG. 7 is an embodiment of the optical scanning device according to claim 10, wherein the parallel flat plate 5B is provided so as to transmit "only the deflected light beam" toward the reflection imaging element 6.

The modified embodiment shown in FIG. 8 is an embodiment of the optical scanning device according to the twelfth aspect. A reflection film 5M is formed on a part of the surface of the parallel plate 5A on the side of the deflecting means 4, and a light beam reflected by the reflection imaging element 6 is transmitted through the parallel plate 5 and then reflected.
The light is reflected by M, passes through the parallel flat plate 5 again, and travels toward the recording medium 7.

The modified embodiment shown in FIG. 9 is an embodiment of the optical scanning device according to the thirteenth aspect. A reflection film 5m is formed on a part of the surface of the parallel flat plate 5A on the side of the reflective imaging element 6, and a light beam reflected by the reflective imaging element 6 is reflected by the reflective film 5m and travels toward the recording medium 7.

Hereinafter, specific examples of the optical scanning in the respective embodiments shown in FIGS. 6 to 9 will be described. In each of the specific examples, the reflective imaging element 6 has the three parameters “R _m , R _s , K” described above.
To specify the shape, and for a parallel plate, the refractive index:
The material is specified by n, and the shape is specified by thickness: t. The deployment state of the parallel plate is specified by giving its “tilt angle (angle of inclination from a direction parallel to the rotation axis of the deflecting means): α”. Incidentally, the refractive index: n of the parallel plate is n = 1.5118 throughout all the specific examples. The beam deflecting surface is a plane in this case.

The luminous flux from the light source is converted into a divergent luminous flux by the lens 2, and the starting point of the divergence (the position on the geometrical optics where the divergent luminous flux is considered to have started to diverge) is reflected by the reflective imaging element 6. Gives the distance from the mirror surface: S ₀ (this gives
The position of the light source in the main scanning corresponding direction of the incident deflected light beam incident on the reflective imaging element 6 is determined). Since the starting point of the divergence is located in front of the mirror surface of the reflective imaging element 6, it is represented by a negative distance.

Further, the reflective imaging element 6 has the following specific examples 8 to
At 30, the optical axis is parallel to the beam deflection plane;
The distance between the optical axis and the beam deflecting surface is given as the "shift amount" of the reflective imaging element. The distance reaches the reflective image forming element from the deflection origin: L _0, in embodiments 8 to 30, L ₀
= 66.1079 mm. The arrangement of the reflective imaging element is determined by the shift amount and L ₀ . "Separation amount"
Represents the distance between the beam deflecting surface and the reflected light beam in either the position of the deflecting / reflecting surface or the plane of the parallel plate. “Scanning line bending” represents the maximum value of the deviation between the actual scanning line and the above-described optical scanning line L.

The first specific examples 8 to 19 are specific examples in the embodiment of FIG. “Separation amount” indicates the distance between the beam deflecting surface and the reflected light beam at the position of the deflecting / reflecting surface.

Specific Example 8 t = 4 mm, α = 15 degrees, S ₀ = −314.089, K
_{= -1.87, R m = -223.0,} R s = -110.
5, shift amount: 0.41 mm, separation amount = 0.91 mm,
Scan line bending = 4 μm.

Specific Example 9 t = 4 mm, α = 30 degrees, S ₀ = −314.089, K
_{= -1.87, R m = -223.0,} R s = -110.
5, shift amount: 0.71 mm, separation amount: 1.75 mm,
Scan line bending = 11 μm.

Specific Example 10 t = 4 mm, α = 45 degrees, S ₀ = −314.089, K
_{= -1.87, R m = -223.0,} R s = -110.
5, shift amount: 0.70 mm, separation amount = 2.36 mm,
Scan line bending = 21 μm.

Specific Example 11 t = 4 mm, α = 60 degrees, S ₀ = −314.089, K
_{= -1.89, R m = -223.0,} R s = -110.6
3, shift amount: 0.00 mm, separation amount = 2.35 mm,
Scan line bending = 31 μm.

Specific Example 12 t = 8 mm, α = 15 degrees, S ₀ = −292.339, K
_{= -1.85, R m = -218.7,} R s = -108.
8, shift amount: 0.86 mm, separation amount = 1.84 mm,
Scan line bending = 7 μm.

Specific Example 13 t = 8 mm, α = 30 degrees, S ₀ = −292.339, K
_{= -1.85, R m = -218.6,} R s = -108.
0, shift amount: 1.50 mm, separation amount = 3.50 mm,
Scan line bending = 19 μm.

Specific Example 14 t = 8 mm, α = 45 degrees, S ₀ = −292.339, K
_{= -1.88, R m = -218.6,} R s = -108.
2, shift amount: 1.48 mm, separation amount: 4.72 mm,
Scan line bending = 40 μm.

Specific Example 15 t = 8 mm, α = 60 degrees, S ₀ = −292.339, K
_{= -1.81, R m = -218.8,} R s = -108.
7, shift amount: 0.11 mm, separation amount: 4.69 mm,
Scan line bending = 62 μm.

Specific Example 16 t = 12 mm, α = 15 degrees, S ₀ = −249.97,
_{K = -1.81, R m = -210.0} , R s = -105.
5, shift amount: 1.42 mm, separation amount = 2.94 mm,
Scan line bend = 6 μm.

Specific Example 17 t = 12 mm, α = 30 degrees, S ₀ = −259.68,
_{K = -1.83, R m = -211.6} , R s = -104.
2, shift amount: 2.50 mm, separation amount: 5.70 mm,
Scan line bending = 24 μm.

Specific Example 18 t = 12 mm, α = 45 degrees, S ₀ = −286.93,
_{K = -1.86, R m = -216.5} , R s = -104.
2, shift amount: 2.47 mm, separation amount: 7.41 mm,
Scan line bending = 60 μm.

Specific Example 19 t = 12 mm, α = 60 degrees, S ₀ = −292.339,
_{K = -1.89, R m = -217.2} , R s = -105.
1, shift amount: 0.38 mm, separation amount = 7.20 mm,
Scan line bending = 93 μm.

The following specific examples 20 to 23 are specific examples in the embodiment shown in FIG. The "separation amount" indicates the distance between the beam deflecting surface on the side of the deflecting means of the parallel plate and the reflected light beam.

Specific Example 20 t = 8 mm, α = 15 degrees, S ₀ = −292.339, K
_{= -1.85, R m = -218.7,} R s = -108.
7, shift amount: 0.95 mm, separation amount = 1.32 mm,
Scan line bending = 8 μm.

Specific Example 21 t = 8 mm, α = 30 degrees, S ₀ = −292.339, K
_{= -1.86, R m = -218.6,} R s = -107.
9, shift amount: 1.67 mm, separation amount: 2.47 mm,
Scan line bending = 23 μm.

Specific Example 22 t = 8 mm, α = 45 degrees, S ₀ = −292.339, K
_{= -1.89, R m = -218.6,} R s = -107.
9, shift amount: 1.72 mm, separation amount: 3.12 mm,
Scan line bending = 45 μm.

Specific Example 23 t = 8 mm, α = 60 degrees, S ₀ = −292.339, K
_{= -1.91, R m = -218.8,} R s = -108.
0, shift amount: 0.40 mm, separation amount = 2.93 mm,
Scan line bending = 66 μm.

In the following specific examples 24 to 26, in the embodiment shown in FIG. 6, the incident angle of the deflected light beam to the parallel flat plate satisfies the Brewster angle. This is a specific example. The “separation amount” indicates the distance between the beam deflection surface and the reflected light beam at the deflection start position.

Specific Example 24 t = 4 mm, α = 56.506 degrees, S ₀ = −314.0
_{89, K = -1.89, R m} = -223.0, R s = -1
10.65, shift amount: 0.24 mm, separation amount = 2.4
2 mm, scan line bending = 29 μm
.

Specific Example 25 t = 8 mm, α = 56.506 degrees, S ₀ = −292.3
_{39, K = -1.89, R m} = -218.6, R s = -1
09.0, shift amount: 0.58 mm, separation amount = 4.81
mm, scanning line bending = 58 μm
.

Specific Example 26 t = 12 mm, α = 56.506 degrees, S ₀ = −292.
_{339, K = -1.88, R m} = -217.2, R s = -
105.6, shift amount: 1.05 mm, separation amount = 7.3
5 mm, scanning line bending = 86 μm
.

A specific example 27 of the optical scanning device according to claim 11, wherein the incident angle of the deflected light beam to the parallel flat plate satisfies the Brewster angle in the embodiment shown in FIG. It is. The "separation amount" indicates the distance between the beam deflecting surface on the side of the deflecting means of the parallel plate and the reflected light beam.

Specific Example 27 t = 8 mm, α = 56.506 degrees, S ₀ = −292.3
_{39, K = -1.9, R m} = -218.6, R s = -10
8.0, shift amount: 0.86 mm, separation amount = 3.05 m
m, scanning line bending = 62 μm
.

Specific examples 28 to 30 are specific examples in the embodiment shown in FIGS. The “separation amount” represents the distance between the deflecting light beam and the reflected light beam on the side of the reflection imaging element of the parallel plate in the direction of the rotation axis of the deflecting means.

Specific Example 28 t = 12 mm, α = 30 degrees, S ₀ = −292.339,
_{K = -1.71, R m = -218.8} , R s = -113.
3, shift amount: 1.8 mm, separation amount: 2.28 mm, scanning line bending = 37 μm.

Specific Example 29 t = 12 mm, α = 45 degrees, S ₀ = −292.339,
_{K = -1.74, R m = -218.8} , R s = -112.
0, shift amount: 1.8 mm, separation amount = 3.28 mm, scanning line bending = 83 μm.

Specific Example 30 t = 12 mm, α = 60 degrees, S ₀ = −292.339,
_{K = -1.85, R m = -219.5} , R s = -108.
45, shift amount: -0.1 mm, separation amount: 3.93 m
m, scanning line bending = 83 μm
.

FIGS. 10 to 32 show field curvature (left figure) and scanning characteristics (right figure) for the above Examples 8 to 30. In the figure of the field curvature, a solid line represents a sagittal ray, and a broken line represents a meridional ray. When the ideal image height for the deflection angle θ of the deflected light beam is H (θ) and the actual image height is H ′ (θ), the scanning characteristics are as follows: [{H ′ (θ) −H (θ)} / H ( θ)] × 100%, and corresponds to the fθ characteristic of the fθ lens. In each of the specific examples, both the curvature of field and the scanning characteristics are good, and as described above, the curvature of the scanning line is at most 0.
It is corrected very well to 1 mm or less.

In each of the above specific examples, the reflection image forming element
Although the mirror surface shape is specified by the three parameters “R _m , R _s , K”, the present invention is of course applicable to the case where a reflective imaging element having another mirror surface shape is used.

FIG. 33A schematically shows only an essential part of an embodiment of the optical scanning device according to the present invention. In order to avoid complication, the same reference numerals as those in FIG.

The luminous flux emitted from the light source 1 is suppressed from diverging by the lens 2 having a positive power, and the luminous flux transmitted through the lens 2 is converted into a parallel luminous flux or a condensing light depending on the power and arrangement of the lens 2. Or a divergent light flux. The light beam transmitted through the lens 2 may be any of the above-mentioned parallel light beam, condensed light beam, and divergent light beam. In this example, the light beam is a divergent light beam. The divergent light beam transmitted through the lens 2 is given a tendency to converge only in the sub-scanning corresponding direction by the cylinder lens 3, and forms an image near the deflecting reflection surface of the deflecting means 4 as a long line image in the main scanning corresponding direction.

The deflection light beam deflected by the deflection means 4 is
Next, the light enters the reflective imaging element 6 via the long prism 50 and is reflected by the element 6 to become a reflected light flux. The reflected light beam is applied to the surface of the recording medium 7 and is condensed as a light spot on the peripheral surface of the recording medium 7 by the operation of the reflection imaging element 6. The light spot optically scans the optical scanning line L "ideally" according to the deflection of the deflected light beam. The scanning line ideally matches the optical scanning line L, but in practice, it generally bends and deviates from the optical scanning line L.

The reflection imaging element 6 is an anamorphic concave mirror 6 similar to that described with reference to FIG. 1A, and is a “concave barrel-shaped surface”. Is determined by the three parameters “R _m , R _s , K”.

As described above, the light beam incident on the deflecting means 4 forms an image as a long linear image in the direction corresponding to the main scanning near the deflecting / reflecting surface, and the reflecting / image forming element 6 deflects and reflects light in the direction corresponding to the sub-scanning. The position of the surface and the position of the surface to be scanned have a geometrical conjugate relationship (therefore, this embodiment is also an embodiment of the optical scanning device according to claim 19).

FIG. 33B shows a state in which the optical path from the deflecting means 4 of the optical scanning device of FIG. 33A to the recording medium 7 is viewed from the main scanning corresponding direction. Specular shape of the reflective image forming element 6 that appear in Figure radius: an arc of R _s. Reference symbol BS indicates a “beam deflection surface”, and reference symbol AX indicates an optical axis of the reflective imaging element 6. The optical axis AX is parallel to the beam deflection surface BS. The light beam deflected by the deflecting means 4 is converted into a long prism 50.
Is transmitted to the reflection image forming element 6, and when reflected by the element 6, optical scanning of the recording medium 7 is performed. The long prism 50 is provided with its longitudinal direction parallel to the main scanning direction, and has a wedge-shaped cross section. However, the surface on the side of the deflecting means 4 is orthogonal to the beam deflecting surface, and therefore, on the exit side. The plane is inclined with respect to the beam deflection plane BS.

For this reason, the deflected light beam emitted from the long prism 50 is tilted in the optical path direction with respect to the beam deflection surface BS due to refraction at the emission surface, and is tilted with respect to the optical axis AX with respect to the reflection imaging element 6. As a result, the reflected light flux forms an angle with respect to the incident light flux in a direction perpendicular to the beam deflecting surface (the vertical direction in the drawing), and the optical path is separated.

FIG. 34A shows the incident position of the deflected light beam on the reflective imaging element 6 in the optical arrangement shown in FIG.
When the deflection angle of the deflected light beam is 0 (when the direction of the deflected light beam from the deflecting means 4 toward the long prism 50 is parallel to the optical axis of the reflection imaging element 6, indicated by a solid line), the deflection angle is large. At the time (indicated by a broken line). When the deflection angle is 0, the deflected light beam refracted by the long prism 50 is incident on the optical axis position of the reflective imaging element 6, but is deflected to the exit surface of the long prism 50 as the deflection angle increases. Since the angle of incidence of the light beam changes, the angle of refraction at the exit surface also changes gradually, and as the deflection angle increases, the position of the light spot on the surface to be scanned shifts in the direction corresponding to sub-scanning, as indicated by the broken line. , The bending of the scanning line becomes large.

FIG. 34B shows an embodiment of the optical scanning device according to the sixteenth aspect. In this embodiment, the reflective imaging element 6 is shifted from the state of FIG. 34A in a direction orthogonal to the beam deflecting surface BS, and the optical axis A is parallel to the beam deflecting surface BS.
The position of X is the incident position of the deflected light beam (solid line) with a deflection angle of 0 on the reflective imaging element 6, and the incident position of the deflected light beam (dashed line) with the maximum deflection angle in the effective optical scanning area on the reflective imaging element 6. Thus, the bending of the scanning line is corrected.

FIG. 34C shows an embodiment of the optical scanning device according to the seventeenth aspect. In this embodiment, from the state of FIG. 34 (A), the reflection imaging element 6 is parallel to the main scanning corresponding direction (the direction orthogonal to the drawing) and has an angle Δβ with a straight line passing through the intersection of the mirror surface and the optical axis as an axis. By being tilted, the curvature of the scanning line is corrected.

The following specific example 31 is a specific example of the optical scanning device according to claim 16 shown in FIG. The shape of the reflective imaging element 6 is specified by the aforementioned three parameters “R _m , R _s , K”. For the long prism 50, the refractive index is n.
, The thickness at the incident position of the deflected light beam: t and the apex angle: δ. L ₀ is the distance from the deflection starting point of the deflecting means to the reflective imaging element 6 as before, and the writing width of the optical scanning is 216 mm.

In this embodiment, the "shift amount" is the shift amount 0 in the state of FIG. 34A, and (+) in FIG. 34 when the reflective imaging element 6 is displaced upward. Represents

Specific Example 31 t = 4 mm, δ = 10 degrees, n = 1.5118, L ₀ =
_{66.11, K = -1.72, R m} = -222.0, R s
= -108.3, shift amount: 6.45 mm.

The following specific example 32 is a specific example of the optical scanning device according to claim 17 shown in FIG.
“R _m , R _s , K”, n, t, and L ₀ have the same meanings as in the specific example 30. Writing width of optical scanning is 216mm
It is.

In this embodiment, the tilt amount of the reflection imaging element is set to 0 in the state shown in FIG. 34A, and the reflection imaging element 6 is rotated counterclockwise as shown in FIG. Is represented as (-).

Specific Example 32 t = 4 mm, δ = 10 degrees, n = 1.5118, L ₀ =
_{66.11, K = -1.72, R m} = -222.0, R s
= -108.3, tilt amount: -3.4 degrees.

FIG. 35 (a) shows the bending of the scanning line when both the shift amount and the tilt amount are set to 0 in the specific examples 31 and 32. Figures (b) and (c) respectively. The situation of the scanning line after correcting the bending of the scanning line by specific examples 31 and 32 is shown. It can be seen that the curvatures of the scanning lines are effectively corrected in both the specific examples 31 and 32.

In the example described with reference to FIG. 33, the reflective imaging element 6 is anamorphic, and the deflecting means has a conjugate relationship between the position of the deflecting reflective surface of the deflecting means and the surface to be scanned in the sub-scanning corresponding direction. Is corrected.

The "mortise mirror" described as a deflecting means
Unlike the rotary polygon mirror, the tilt of the mirror is relatively small, and therefore, it is often not necessary to correct the tilt. In such a case, it is not necessary to make the reflective imaging element anamorphic, and the mirror surface shape of the reflective imaging element should be a coaxial spherical surface or a coaxial aspheric surface, that is, a spherical or aspherical surface rotationally symmetric with respect to the optical axis. (Claim 18).

The following specific example 33 is a specific example of the optical scanning device according to claim 18. The reflective imaging element is a coaxial aspherical surface, and its shape is specified by a radius of curvature on the optical axis: R and a conical constant: K. n, t, δ, and L ₀ have the same meanings as in the specific example 31. Write width of optical scanning is 216m
m.

Specific Example 33 t = 4 mm, δ = 10 degrees, n = 1.5118, L ₀ =
137.76, K = 2.14, R = -387.0, shift amount = 29.62 mm.

In this specific example 33, when the shift amount is set to 0, that is, the reflection imaging element having a coaxial aspherical shape is used as shown in FIG.
4 (A), when the scanning line is bent,
Although it is large as shown in FIG. 36A, a shift amount of 29.62 mm is given to the reflective imaging element as in the specific example 33,
With the arrangement as shown in FIG. 34B, it is possible to effectively reduce and correct the bending of the scanning line as shown in FIG. 36B.

FIG. 37A schematically shows only an essential part of an embodiment of the optical scanning device according to the present invention. In order to avoid complication, the same reference numerals as those in FIG.

The luminous flux radiated from the light source 1 is suppressed from diverging by the lens 2 having positive power, and the luminous flux transmitted through the lens 2 is converted into a parallel luminous flux or a condensing light depending on the power and arrangement of the lens 2. Or a divergent light flux. The light beam transmitted through the lens 2 may be any of the above-mentioned parallel light beam, condensed light beam, and divergent light beam. In this example, the light beam is a divergent light beam. The divergent light beam transmitted through the lens 2 is given a tendency to converge only in the sub-scanning corresponding direction by the cylinder lens 3, and forms an image near the deflecting reflection surface of the deflecting means 4 as a long line image in the main scanning corresponding direction.

The deflected light beam deflected by the deflecting means 4 is
Next, the light enters the reflective imaging element 6 via the parallel plate 5A,
When reflected by the element 6, it becomes a reflected light flux. The reflected light flux is applied to the surface of the recording medium 7, but is condensed as a light spot on the peripheral surface of the recording medium 7 by the operation of the reflection imaging element 6. The scanning line generally bends and deviates from the optical scanning line L.

The reflection imaging element 6 is an anamorphic concave mirror 6 similar to that described with reference to FIG. 1A, and is a “concave barrel-shaped surface”. 3
It is determined by the parameters “R _m , R _s , K”.

As in the example of FIG. 6A, the light beam incident on the deflecting means 4 forms an image as a long line image in the main scanning direction in the vicinity of the deflecting reflection surface, and the reflection image forming element 6 in the sub-scanning direction. The position of the deflecting / reflecting surface and the position of the surface to be scanned have a geometrical conjugate relationship.

FIG. 37 (B) shows the optical path from the deflecting means 4 of the optical scanning device of FIG. 37 (A) to the recording medium 7 as viewed from the main scanning corresponding direction. Specular shape of the reflective image forming element 6 that appear in Figure radius: an arc of R _s. Reference symbol BS indicates a “beam deflection surface”, and reference symbol AX indicates an optical axis of the reflective imaging element 6.

The difference from the embodiment of FIG. 6 is that in this embodiment, the optical axis AX is at a predetermined angle with respect to the beam deflection surface BS:
This is a point inclined by Δθ. The light beam deflected by the deflecting means passes through the parallel plate 5A and is incident on the reflective imaging element 6, and when reflected by the element 6, passes through the parallel plate 5A to perform optical scanning of the recording medium 7 (accordingly, in this example). Is claim 21
It is also an embodiment of the described optical scanning device).

FIGS. 38 to 40 show modified examples. In order to avoid complication, the same reference numerals as those in FIG. 37 are used for those which do not seem to be confused. In these modified examples, the optical arrangement on the optical path from the light source to the deflecting means is the same as the example described with reference to FIG.
37, the position of the deflecting reflecting surface and the position of the surface to be scanned are set to have a "geometrically optically conjugate relationship with respect to the sub-scanning corresponding direction."

The embodiment shown in FIG. 38 is an embodiment of the optical scanning device according to claim 22, wherein the parallel flat plate 5B is provided so as to transmit only the deflected light beam directed to the reflective imaging element 6.

The modified embodiment shown in FIG. 39 is an embodiment of the optical scanning device according to claim 24. A reflection film 5M is formed on a part of the surface of the parallel plate 5A on the side of the deflecting means 4, and a light beam reflected by the reflective imaging element 6 passes through the parallel plate 5, is reflected by the reflection film 5M, and is again formed. To the recording medium 7.

The modified embodiment shown in FIG. 40 is an embodiment of the optical scanning device according to claim 25. A reflection film 5m is formed on a part of the surface of the parallel flat plate 5A on the side of the reflective imaging element 6, and a light beam reflected by the reflective imaging element 6 is reflected by the reflective film 5m and travels toward the recording medium 7.

Hereinafter, specific examples of the optical scanning in the respective embodiments shown in FIGS. 37 to 40 will be described. In each of the specific examples, the reflective imaging element 6 has the three parameters “R _m , R _s ,
K "is given to specify the shape. For a parallel plate, the material is specified by the refractive index: n, and the shape is specified by the thickness: t.
The deployment state of the parallel plate is specified by giving its “tilt angle (angle of inclination from a direction parallel to the rotation axis of the deflecting means): α”. Incidentally, the refractive index: n of the parallel plate is n = 1.5118 throughout all the specific examples.

The luminous flux from the light source is converted into a divergent luminous flux by the lens 2, and the starting point of the divergence (the position on the geometrical optics where the divergent luminous flux is considered to have started to diverge) is reflected by the reflection imaging element 6. Gives the distance from the mirror surface: S ₀ (this gives
The position of the light source in the main scanning corresponding direction of the incident deflected light beam incident on the reflective imaging element 6 is determined). Since the starting point of the divergence is located in front of the mirror surface of the reflective imaging element 6, it is represented by a negative distance.

In the following specific examples 34 to 43, the optical axis of the reflective imaging element 6 is tilted by Δ with respect to the beam deflection surface.
It is inclined by θ (unit: degree). The distance reaching the reflective image forming element from the deflection origin and L _0, located state position of the reflective image forming element is determined by the Δθ and L _0.

The "separation amount" represents the distance between the beam deflecting surface and the reflected light beam in either the position of the deflecting / reflecting surface or the plane of the parallel plate. “Scanning line bending” represents the maximum value of the deviation between the actual scanning line and the above-described optical scanning line L.

The first specific examples 34 to 39 are shown in FIG.
It is a specific example in the embodiment of the present invention. In these specific examples, the “separation amount” indicates the distance between the beam deflecting surface and the reflected light beam at the position of the deflecting and reflecting surface.

Specific Example 34 t = 4 mm, α = 15 degrees, S ₀ = −306.11, L ₀ =
_{66.11, K = -1.87, R m} = -223.0, R s
= −110.5, Δθ = 0.4, separation amount = 1.0 mm,
Scan line bending = 7 μm.

Specific Example 35 t = 4 mm, α = 60 degrees, S ₀ = −296.11, L ₀ =
_{66.11, K = -1.89, R m} = -221.2, R s
= −109.7, Δθ = 1.1, separation amount = 2.4 mm,
Scan line bending = 27 μm.

Specific Example 36 t = 8 mm, α = 15 degrees, S ₀ = −296.11, L ₀ =
_{66.11, K = -1.89, R m} = -218.7, R s
= −108.8, Δθ = 0.8, separation amount = 1.8 mm,
Scan line bending = 22 μm.

Specific Example 37 t = 8 mm, α = 60 degrees, S ₀ = −296.11, L ₀ =
_{66.11, K = -1.86, R m} = -218.8, R s
= −108.7, Δθ = 2.20, separation amount = 4.6 m
m, scanning line bending = 54 μm
.

Specific Example 38 t = 12 mm, α = 15 degrees, S ₀ = −296.61, L ₀
= 68.61, K = -1.77, R m = -218.0,
_{R s = -109.05, Δθ = 1.2} , amount of separation = 2.7
mm, scanning line bending = 6 μm
.

Specific Example 39 t = 12 mm, α = 60 degrees, S ₀ = −296.11, L ₀
= 66.11, K = -1.87, R m = -217.2,
R _s = -105.1, Δθ = 3.6, separation amount = 7.3 m
m, scanning line bending = 54 μm
.

The following specific examples 40 to 41 are specific examples of the embodiment shown in FIG. In these specific examples, the “separation amount” indicates the distance between the beam deflecting surface on the side of the deflecting means of the parallel plate 5A and the reflected light beam.

Specific Example 40 t = 8 mm, α = 30 degrees, S ₀ = −292.339, L ₀
= 66.11, K = -1.86, R m = -218.6,
R _s = -111.2, Δθ = 1.63, separation amount = 2 m
m, scanning line bending = 23 μm
.

Specific Example 41 t = 8 mm, α = 60 degrees, S ₀ = −292.339, L ₀
= 66.11, K = -1.91, R m = -218.6,
R _s = -108.0, Δθ = 2.4, separation amount = 3 mm,
Scan line bending = 65 μm.

The following specific example 42 is a specific example of the optical scanning device according to claim 23, wherein the incident angle of the deflected light beam to the parallel flat plate satisfies the Brewster angle in the embodiment of FIG. is there. In this specific example, the "separation amount"
Represents the distance between the beam deflection surface and the reflected light beam at the deflection starting position.

Concrete Example 42 t = 8 mm, α = 56.506 degrees, S ₀ = −296.1
1, L ₀ = 66.11, K = −1.89, R _m = −21
8.6, R _s = -109.0, Δθ = 2.25, separation amount = 4.8 mm, scanning line bending = 44 μm
.

The last specific example 43 is a specific example of the embodiment of FIG. The “separation amount” represents the distance between the deflecting light beam and the reflected light beam on the side of the parallel-plate reflective imaging element in the direction perpendicular to the beam deflecting surface.

Specific Example 43 t = 12 mm, α = 45 degrees, S ₀ = −299.11, L ₀
= 66.11, K = -1.74, R m = -218.8,
R _s = -112.0, Δθ = 2.9, separation amount = 3.0 m
m, scanning line bending = 54 μm
.

FIGS. 41 to 50 show the field curvature (left figure) and the scanning characteristics (right figure) of the above Examples 34 to 43. In all of the specific examples 34 to 43, the curvature of field and the scanning characteristics are satisfactorily corrected, and even those having a large scanning line curve are corrected very well at 0.1 mm or less.

FIG. 51A schematically shows only an essential part of an embodiment of the optical scanning device according to the twenty-seventh aspect. In order to avoid complication, the same reference numerals as those in FIG. 37 (A) are used for those which are considered to be free from confusion.

The luminous flux radiated from the light source 1 is suppressed from diverging by the lens 2 having a positive power, and the luminous flux transmitted through the lens 2 is converted into a parallel luminous flux or a condensing light depending on the power and arrangement of the lens 2. Or a divergent light flux. The light beam transmitted through the lens 2 may be any of the above-mentioned parallel light beam, condensed light beam, and divergent light beam. In this example, the light beam is a divergent light beam. The divergent light beam transmitted through the lens 2 is given a tendency to converge only in the sub-scanning corresponding direction by the cylinder lens 3, and forms an image near the deflecting reflection surface of the deflecting means 4 as a long line image in the main scanning corresponding direction.

The deflection light beam deflected by the deflecting means 4 is
Next, the light enters the reflective imaging element 6 via the parallel plate 5A,
When reflected by the element 6, it becomes a reflected light flux. The reflected light flux is applied to the surface of the recording medium 7, but is condensed as a light spot on the peripheral surface of the recording medium 7 by the operation of the reflection imaging element 6. The scanning line generally bends and deviates from the optical scanning line L.

The reflection image forming element 6 is an anamorphic concave mirror 6 similar to that described with reference to FIG. 1A, and is a “concave barrel-shaped surface”. 3
It is determined by the parameters “R _m , R _s , K”.

As in the example of FIG. 37A, the light beam incident on the deflecting means 4 forms an image as a long line image in the direction corresponding to the main scanning in the vicinity of the deflecting and reflecting surface, and the reflection imaging element 6 operates in the direction corresponding to the sub scanning. , The position of the deflecting reflection surface and the position of the surface to be scanned have a geometrical conjugate relationship.
It is also an embodiment of the described optical scanning device).

FIG. 51B shows a state where the optical path from the deflecting means 4 of the optical scanning device of FIG. 51A to the recording medium 7 is viewed from the main scanning corresponding direction. Specular shape of the reflective image forming element 6 that appear in Figure radius: an arc of R _s. Reference symbol BS indicates a “beam deflection surface”, and reference symbol AX indicates an optical axis of the reflective imaging element 6.

The difference from the embodiment shown in FIG. 37 is that, in this embodiment, a light beam from the light source side is obliquely incident on the deflecting / reflecting surface BS. As described above, the amount of "ray shift amount" is used as an index indicating the relative relationship between the inclination of the light beam incident on the deflection reflecting surface from the light source side with respect to the beam deflection surface and the reflection imaging element.

That is, as shown in FIG. 51B, the deflected light beam enters the reflecting surface of the reflecting and imaging element 6 via the parallel plate 5A, but the image height of the light spot on the surface to be scanned is zero. The distance between the incident position: P and the central portion of the above-described reflective imaging element 6: O (the intersection of the optical axis AX and the reflective surface): Δl
Is called “ray shift amount (unit: mm)”, and the incident position:
When P is below the center: O, it is defined as “positive”.

The light beam deflected by the deflecting means passes through the parallel flat plate 5A and is incident on the reflective imaging element 6, and when reflected by the same element 6, passes through the parallel flat plate 5A and scans the recording medium 7 (accordingly. This example is also an embodiment of the optical scanning device according to claim 30).

FIGS. 52 to 54 show modified examples. In order to avoid complication, the same reference numerals as those in FIGS. 38 to 40 are used for those which do not seem to be confused. In these modified examples, the optical arrangement on the optical path from the light source to the deflecting means is the same as the example described with reference to FIG. 51. Is substantially "conjugated geometrically and optically with respect to the sub-scanning corresponding direction" as in the embodiment of FIG.

The embodiment shown in FIG. 52 is an embodiment of the optical scanning device according to claim 31, wherein the parallel flat plate 5B is provided so as to transmit only the deflected light beam directed to the reflective imaging element 6.

The modified embodiment shown in FIG. 53 is an embodiment of the optical scanning device according to claim 33. A reflection film 5M is formed on a part of the surface of the parallel plate 5A on the side of the deflecting means 4, and a light beam reflected by the reflective imaging element 6 passes through the parallel plate 5, is reflected by the reflection film 5M, and is again formed. To the recording medium 7.

The modified embodiment shown in FIG. 54 is an embodiment of the optical scanning device according to claim 34. A reflection film 5m is formed on a part of the surface of the parallel flat plate 5A on the side of the reflective imaging element 6, and a light beam reflected by the reflective imaging element 6 is reflected by the reflective film 5m and travels toward the recording medium 7.

In FIGS. 51 to 54, the optical axis AX of the reflective imaging element 6 is parallel to the beam deflecting surface BS and the “tilt amount” is zero. The tilt amount may be used.
8) Both the light shift amount and the tilt amount can be finite.

Hereinafter, specific examples of the optical scanning in the respective embodiments shown in FIGS. 51 to 54 will be described. In each of the specific examples, the reflective imaging element 6 has the three parameters “R _m , R _s ,
K "is given to specify the shape. For a parallel plate, the material is specified by the refractive index: n, and the shape is specified by the thickness: t.
The deployment position of the parallel plate is specified by giving its “tilt angle (angle of tilt from the direction parallel to the rotation axis of the deflecting means = angle between the normal of the parallel plate and the beam deflecting surface): α”. I do. The refractive index of the parallel plate: n is n = n through all the following specific examples.
1.51118.

The luminous flux from the light source is converted into a divergent luminous flux by the lens 2, and the starting point of the divergence (the position on the geometrical optics where the divergence of the divergent luminous flux is considered to have started) is reflected by the reflection imaging element 6. Gives the distance from the mirror surface: S ₀ (this gives
The position of the light source in the main scanning corresponding direction of the incident deflected light beam incident on the reflective imaging element 6 is determined). Since the starting point of the divergence is located in front of the mirror surface of the reflective imaging element 6, it is represented by a negative distance. When the distance extending from the deflecting origin by the deflection means deflect light flux reflected image forming element and L _0, in general, light shift amount; .DELTA.l and, tilt quantity: [Delta] [theta] and L ₀ and the arrangement state position of the reflective image forming element 6 Is determined.

In the following specific examples, the “separation amount”
The distance between the beam deflection surface and the reflected light beam at the position of the deflection reflection surface is shown. “Scanning line bending” represents the maximum value of the deviation between the actual scanning line and the above-described optical scanning line L.

The first specific examples 44 to 49 are shown in FIG.
And the tilt amount: Δ
θ = 0.

Specific Example 44 t = 4 mm, α = 15 degrees, S ₀ = −315.1, L ₀ = 6
_{6.1, K = -1.87, R m} = -223.0, R s = -
110.5, Δl = 3.6, separation amount = 0.3 mm, scanning line bending = 26 μm.

Specific Example 45 t = 4 mm, α = 60 degrees, S ₀ = −315.1, L ₀ = 6
_{6.11, K = -1.89, R m} = -223.0, R s =
−110.5, Δl = 5.1, separation amount = 1.4 mm, scanning line bending = 20 μm.

Specific Example 46 t = 8 mm, α = 15 degrees, S ₀ = −293.3, L ₀ = 6
_{6.1, K = -1.85, R m} = -218.7, R s = -
108.7, Δl = 4.2, separation amount = 0.5 mm, scanning line bending = 36 μm.

Specific Example 47 t = 8 mm, α = 60 degrees, S ₀ = −293.3, L ₀ = 6
_{6.1, K = -1.91, R m} = -218.8, R s = -
112.0, Δl = 7.0, separation amount = 3.6 mm, scanning line bending = 46 μm.

Specific Example 48 t = 12 mm, α = 15 degrees, S ₀ = −311.2, L ₀ =
_{70.3, K = -1.73, R m} = -223.34, R s
= −112.0, Δl = 4.9, separation amount = 1.2 mm,
Scan line bending = 40 μm.

Specific Example 49 t = 12 mm, α = 60 degrees, S ₀ = −293.3, L ₀ =
_{66.1, K = -1.89, R m} = -217.2, R s =
−105.1, Δl = 9.3, separation amount = 6.2 mm, scanning line bending = 46 μm.

The following specific examples 50 to 55 are also specific examples in the embodiment shown in FIG. In these embodiments, the ray shift amount: Δl = 0, and the tilt amount: Δθ has a finite size.

Specific Example 50 t = 4 mm, α = 15 degrees, S ₀ = −315.1, L ₀ = 6
_{6.1, K = -1.87, R m} = -223.0, R s = -
110.5, Δθ = 2, separation amount = 0.0 mm, scanning line bending = 67 μm.

Specific Example 51 t = 4 mm, α = 60 degrees, S ₀ = −315.1, L ₀ = 6
_{6.1, K = -1.89, R m} = -223.0, R s = -
110.63, Δθ = 2.6, separation amount = 1.3 mm, scanning line bending = 9 μm.

Specific Example 52 t = 8 mm, α = 15 degrees, S ₀ = −293.3, L ₀ = 6
_{6.1, K = -1.85, R m} = -218.7, R s = -
108.7, Δθ = 2.3, separation amount = 0.7 mm, scanning line bending = 21 μm.

Specific Example 53 t = 8 mm, α = 60 degrees, S ₀ = −293.3, L ₀ = 6
_{6.1, K = -1.91, R m} = -218.8, R s = -
218.8, Δθ = 3.8, separation amount = 3.8 mm, scanning line bending = 35 μm.

Specific Example 54 t = 12 mm, α = 15 degrees, S ₀ = −311.2, L ₀ =
_{70.3, K = -1.73, R m} = -223.34, R s
= −112.0, Δθ = 2.5, separation amount = 1.2 mm,
Scan line bending = 40 μm.

Specific Example 55 t = 12 mm, α = 60 degrees, S ₀ = −293.3, L ₀ =
_{66.1, K = -1.89, R m} = -217.2, R s =
−105.1, Δθ = 5.0, separation amount = 6.1 mm, scanning line bending = 60 μm.

Embodiments 56 to 57 shown below are also specific examples of the embodiment shown in FIG. 51, in which the angle of incidence on the parallel plate is set to the "Brewster angle". It is an Example of an apparatus.

Specific Example 56 t = 8 mm, α = 56.506 degrees, S ₀ = −293.
3, L ₀ = 66.1, K = −1.89, R _m = −218.
6, R _s = -109.0, Δl = 7.1, separation amount = 3.
7 mm, scanning line bending = 36 μm
.

Specific Example 57 t = 8 mm, α = 56.506 degrees, S ₀ = −293.
3, L ₀ = 66.1, K = −1.89, R _m = −218.
6, R _s = -109.0, Δθ = 3.7, separation amount = 3.
6 mm, scanning line bending = 32 μm
.

The following embodiments 58 to 59 are specific examples of the embodiment shown in FIG. 52, and are therefore embodiments of the optical scanning device according to claim 31.

Specific Example 58 t = 12 m, α = 45 degrees, S ₀ = −289.2, L ₀ = 6
_{9.0, K = -1.8, R m} = -218.8, R s = -1
12.0, Δl = 8.3, separation amount = 1.7 mm, scanning line bending = 20 μm.

Specific Example 59 t = 12 mm, α = 45 degrees, S ₀ = −284.2, L ₀ =
_{69.0, K = -1.8, R m} = -218.8, R s = -
112.0, Δθ = 4.3, separation amount = 1.8 mm, scanning line bending = 27 μm.

The numerical values of these specific examples 58 and 59 can be used as they are in the embodiment of FIG. However, in this case, the separation amount is 1.8 mm in each case.

The specific examples 60 to 63 given last are specific examples of the embodiment of FIG. Specific examples 60 and 61 are cases where the tilt amount: Δθ = 0, and specific example 62 is a light shift amount: Δl
In the case of = 0, the specific example 63 is a case where both the amount of light shift: Δl and the amount of tilt: Δθ are finite.

Specific Example 60 t = 8 mm, α = 15 degrees, S ₀ = −294.3, L ₀ = 6
_{7.1, K = -1.85, R m} = -218.7, R s = -
108.7, Δl = 4.4, separation amount = 0.2 mm, scanning line bending = 39 μm.

Specific Example 61 t = 8 mm, α = 56.506 degrees, S ₀ = −293.
_{3, L 0 = 66.1, K} = -1.91, R m = -218.
8, R _s = -108.0, Δl = 7.7, separation amount = 1.
7 mm, scanning line bending = 56 μm
.

Specific Example 62 t = 8 mm, α = 60 degrees, S ₀ = −293.3, L ₀ = 6
_{6.1, K = -1.91, R m} = -218.8, R s = -
218.8, Δθ = 4.1, separation amount = 1.7 mm, scanning line bending = 51 μm.

Specific Example 63 t = 8 mm, α = 15 degrees, S ₀ = −294.3, L ₀ = 6
_{7.1, K = -1.85, R m} = -218.7, R s = -
108.7, Δl = 0.2, Δθ = 2.4, separation amount =
0.2 mm, scanning line bending = 29 μm.

FIGS. 55 to 74 show the curvature of field (left figure) and the scanning characteristics (right figure) of the above Examples 44 to 63. In all of the specific examples 44 to 63, the curvature of field and the scanning characteristics are satisfactorily corrected, and even those having a large scanning line curve are corrected very well at 0.1 mm or less.

In the specific examples 44 to 63, the angle of inclination of the light beam incident on the deflecting anti-slope surface of the deflecting means with respect to the beam deflecting surface is set to 2 degrees. is there.

[0216]

As described above, according to the present invention, a novel optical scanning device can be provided. Since the optical scanning device according to any one of claims 1 to 6 is configured as described above, in the optical scanning device of the type in which the light spot is imaged by the reflection imaging element having the concave reflection surface shape, the half mirror is separated by the optical path. Good optical scanning can be realized by effectively reducing the bending of the scanning line caused by using as a means.

In the optical scanning device according to the eighth to thirteenth aspects, since a transparent parallel flat plate is used as the optical path separating means, the light use efficiency is higher and the scanning efficiency is higher than when a half mirror is used as the optical path separating means. Since the bending of the line is extremely small, high-speed and good optical scanning is possible. In the optical scanning device according to the eleventh aspect, the incident angle of the incident deflected light beam on the parallel plate approximately satisfies the Brewster angle.
The amount of reflection of the P-deflection component becomes extremely small, and the light use efficiency can be increased without providing an anti-reflection film on the parallel plate. The optical scanning device according to the twelfth and thirteenth aspects has a large degree of freedom in the layout of the optical system.

In the optical scanning device according to the fifteenth to eighteenth aspects,
New optical scanning using the long prism as the optical path separating means is enabled, and in the optical scanning device according to any one of claims 16 to 18, the bending of the scanning line caused by using the long prism as the optical path separating means is effectively reduced. As a result, good optical scanning can be realized.

In the optical scanning device according to the twentieth to twenty-fifth aspects,
The effect of separating the optical path by the parallel flat plate and the effect of tilting the reflective imaging element can favorably correct the scanning line bending.

[0220] In the optical scanning device according to claims 27 to 34,
Smooth correction of scanning line bending by the effect of separating the optical path by a parallel plate and the effect of inclining the light beam incident on the deflecting means from the beam deflecting surface, or by inclining these and the reflective imaging element with respect to the beam deflecting surface it can.

Further, claims 7, 14, 19, 26, 35
In the optical scanning device described above, since the tilt of the deflecting surface can be corrected, various deflecting means such as a rotary polygon mirror can be used as the deflecting means.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the invention described in claims 1 to 7;

FIG. 2 is a diagram for explaining a scanning line bending correction effect according to specific examples of the first and second aspects of the present invention.

FIG. 3 is a diagram illustrating a scanning line bending correction effect according to another specific example of the first and second aspects of the present invention.

FIG. 4 is a diagram illustrating a scanning line bending correction effect according to a specific example of the third embodiment of the present invention.

FIG. 5 is a diagram illustrating a scanning line bending correction effect according to specific examples of the inventions of claims 4 and 5;

FIG. 6 is a view for explaining an embodiment of the optical scanning device of the invention according to claims 8 to 14;

FIG. 7 is a view for explaining a modified embodiment of the invention according to claims 8 to 14;

FIG. 8 is a view for explaining another modified embodiment of the invention described in claims 8 to 14;

FIG. 9 is a view for explaining another modified embodiment of the invention described in claims 8 to 14;

FIG. 10 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 8;

FIG. 11 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 9;

FIG. 12 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 10;

FIG. 13 is a diagram illustrating a curvature of field and a scanning characteristic according to a specific example 11;

FIG. 14 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 12;

FIG. 15 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 13;

FIG. 16 is a diagram illustrating a curvature of field and a scanning characteristic according to a specific example 14;

FIG. 17 is a diagram illustrating a field curvature and a scanning characteristic according to specific example 15;

FIG. 18 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 16;

FIG. 19 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 17;

FIG. 20 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 18;

FIG. 21 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 19;

FIG. 22 is a diagram illustrating a field curvature and a scanning characteristic of the specific example 20;

FIG. 23 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 21;

FIG. 24 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 22;

FIG. 25 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 23;

FIG. 26 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 24;

FIG. 27 is a diagram illustrating a curvature of field and a scanning characteristic according to a specific example 25;

FIG. 28 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 26;

FIG. 29 is a diagram of a field curvature and a scanning characteristic according to a specific example 27;

FIG. 30 is a diagram of a field curvature and a scanning characteristic according to a specific example 28;

FIG. 31 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 29;

FIG. 32 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 30;

FIG. 33 is a view for explaining the invention according to claims 15 to 19;

FIG. 34 is a diagram for explaining the effect of correcting a scan line bending according to the embodiments of the invention.

FIG. 35 is a diagram for explaining the effect of correcting a scan line bending according to a specific example of the invention according to claims 16 and 17;

FIG. 36 is a view for explaining a scanning line bending correction effect according to a specific example of the invention described in claim 18;

FIG. 37 is a view for explaining an embodiment of the optical scanning device according to the invention described in claims 20 to 26;

FIG. 38 is a view for explaining a modified embodiment of the invention according to claims 20 to 26;

FIG. 39 is a view for explaining another modified embodiment of the invention described in claims 20 to 26;

FIG. 40 is a view for explaining another modified embodiment of the invention according to claims 20 to 26.

FIG. 41 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 34;

FIG. 42 is a diagram of a field curvature and a scanning characteristic of the specific example 35;

FIG. 43 is a diagram of a field curvature and a scanning characteristic of the specific example 36;

FIG. 44 is a diagram of a field curvature and a scanning characteristic of the specific example 37;

FIG. 45 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 38;

FIG. 46 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 39;

FIG. 47 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 40;

FIG. 48 is a diagram illustrating a field curvature and a scanning characteristic according to a specific example 41;

FIG. 49 is a diagram of a field curvature and a scanning characteristic regarding the specific example 42;

FIG. 50 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 43;

FIG. 51 is a view for explaining an embodiment of the optical scanning device according to the invention described in claim 27;

FIG. 52 is a view for explaining a modified embodiment of the invention according to claim 30;

FIG. 53 is a view for explaining another modified embodiment of the invention described in claim 31;

FIG. 54 is a view for explaining another modified embodiment of the invention described in claim 34;

FIG. 55 is a diagram showing a field curvature and a scanning characteristic in the specific example 44;

FIG. 56 is a diagram of a field curvature and a scanning characteristic of the specific example 45.

FIG. 57 is a diagram of a field curvature and a scanning characteristic relating to a specific example 46;

FIG. 58 is a diagram of a field curvature and a scanning characteristic in the specific example 47;

FIG. 59 is a diagram of a field curvature and a scanning characteristic according to a specific example 48;

FIG. 60 is a diagram of a field curvature and a scanning characteristic of the specific example 49;

FIG. 61 is a diagram illustrating a field curvature and a scanning characteristic of the specific example 50;

FIG. 62 is a diagram illustrating a field curvature and a scanning characteristic of the specific example 51;

FIG. 63 is a diagram of a field curvature and a scanning characteristic regarding the specific example 52;

FIG. 64 is a diagram of a field curvature and a scanning characteristic regarding a specific example 53;

FIG. 65 is a diagram of a field curvature and a scanning characteristic regarding the specific example 54;

FIG. 66 is a diagram illustrating a field curvature and a scanning characteristic of the specific example 55;

FIG. 67 is a diagram of a field curvature and a scanning characteristic relating to a specific example 56;

FIG. 68 is a diagram illustrating a field curvature and a scanning characteristic of the specific example 57;

FIG. 69 is a diagram illustrating a field curvature and a scanning characteristic of the specific example 58;

FIG. 70 is a diagram of a field curvature and a scanning characteristic relating to a specific example 59;

FIG. 71 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 60;

FIG. 72 is a diagram illustrating a field curvature and a scanning characteristic in the specific example 61;

FIG. 73 is a diagram showing a field curvature and a scanning characteristic of the specific example 62;

FIG. 74 is a diagram of a field curvature and a scanning characteristic relating to a specific example 63;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Condensing lens 3 Cylinder lens 4 Deflection means 5 Half mirror 5A Parallel plate 50 Long prism 6 Reflection imaging element 7 Recording medium

──────────────────────────────────────────────────の Continuation of front page (31) Priority claim number Japanese Patent Application No. 5-14127 (32) Priority date January 29, 1993 (1993.1.129) (33) Priority claim country Japan (JP) (56) References JP-A-48-37011 (JP, A) JP-A-63-106719 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 26/10

Claims (35)

(57) [Claims] 1. A light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting reflection surface rotating at a constant speed, and the deflected light beam is transmitted through a half mirror inclined with respect to the beam deflecting surface. The reflected light from the reflective imaging element is reflected by the half mirror, and the light is condensed as a light spot on the surface to be scanned by the reflective imaging element to perform optical scanning. A reflection imaging device, wherein the reflection imaging element has a function of performing light scanning by the light spot substantially at a constant speed, and in order to correct a bending of a scanning line on a surface to be scanned,
An optical scanning device, wherein the reflection imaging element is arranged by being shifted by a predetermined shift amount in a direction orthogonal to the beam deflection surface. 2. A light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting / reflecting surface rotating at a constant speed, and the deflected light beam is transmitted through a half mirror inclined with respect to the beam deflecting surface. The light is made incident on the reflection imaging element, the light beam reflected by the reflection imaging element is reflected by the half mirror, and the light is condensed as a light spot on the surface to be scanned by the imaging operation of the reflection imaging element to perform optical scanning. An apparatus, wherein the reflective imaging element has a function of performing light scanning by the light spot at a substantially constant speed, and in order to correct a bending of a scanning line on a surface to be scanned,
An optical scanning device, wherein the reflection imaging element is arranged so that its optical axis is inclined by a predetermined tilt amount with respect to the beam deflection surface. 3. A light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting / reflecting surface rotating at a constant speed, and the deflected light beam is transmitted through a half mirror inclined with respect to the beam deflecting surface. The light is made incident on the reflection imaging element, the light beam reflected by the reflection imaging element is reflected by the half mirror, and the light is condensed as a light spot on the surface to be scanned by the imaging operation of the reflection imaging element to perform optical scanning. In the apparatus, the reflective imaging element has a function of performing light scanning by the light spot substantially at a constant speed, and the half mirror has a semi-transparent mirror surface on a deflecting unit side. An optical scanning device, comprising: 4. The optical scanning device according to claim 3, wherein the curvature of the scanning line on the surface to be scanned is corrected by:
An optical scanning device, wherein a reflection imaging element is arranged by being shifted by a predetermined shift amount in a direction orthogonal to a beam deflecting surface. 5. The optical scanning device according to claim 3, wherein the curvature of the scanning line on the surface to be scanned is corrected.
An optical scanning device, wherein a reflection imaging element is provided so that an optical axis thereof is inclined by a predetermined tilt amount with respect to a beam deflection surface. 6. The optical scanning device according to claim 2, wherein a curvature of a scanning line on the surface to be scanned is corrected.
An optical scanning device characterized in that an optical axis of a reflection imaging element is inclined with respect to a beam deflecting surface by a predetermined tilt amount, and the reflection imaging element is arranged so as to be shifted by a predetermined shift amount in a direction orthogonal to the beam deflecting surface. . 7. The optical scanning device according to claim 1, wherein the deflecting means has a deflecting / reflecting surface parallel to the rotation axis, and the deflecting / imaging element comprises a deflecting / reflecting means of the deflecting means. The surface position and the surface to be scanned are geometrically conjugated in the sub-scanning corresponding direction, and the light beam from the light source is formed near the deflecting reflection surface in the sub-scanning corresponding direction as a long line image in the main scanning corresponding direction. An optical scanning device characterized by being imaged. 8. A luminous flux from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting / reflecting surface rotating at a constant speed, the deflected luminous flux is reflected by an anamorphic reflective imaging element, and the reflected luminous flux is reflected. An apparatus for performing optical scanning by condensing light as a light spot on a surface to be scanned by an imaging action of an imaging element, wherein the reflective imaging element performs optical scanning by the light spot substantially at a constant speed. A transparent parallel plate is disposed between the deflecting means and the reflective imaging element so as to be inclined by a finite inclination angle with respect to the rotation axis of the deflecting means, and the light is reflected from the deflecting means. The optical path toward the imaging element and the optical path from the reflective imaging element to the surface to be scanned are separated, and the material, thickness, and tilt angle of the parallel plate are determined so that the scanning line bend is corrected. An optical scanning device. 9. The optical scanning device according to claim 8, wherein both the deflected light beam incident on the reflection imaging device and the reflection light beam reflected by the reflection imaging device are transmitted through a parallel flat plate. Optical scanning device. 10. The optical scanning device according to claim 8, wherein, out of the deflected light beam incident on the reflection imaging element and the reflection light beam reflected by the reflection imaging element, only the deflected light beam incident on the reflection imaging element is a parallel plate. An optical scanning device characterized by transmitting light. 11. The optical scanning device according to claim 8, wherein the angle of inclination of the parallel plate is determined so that the incident angle of the deflected light beam incident on the parallel plate substantially satisfies the Brewster angle. Optical scanning device. 12. The optical scanning device according to claim 9, wherein a reflection film is formed on a part of the surface of the parallel plate on the side of the deflecting means.
An optical scanning device, wherein only a reflected light beam reflected by a reflective imaging element and transmitted through a parallel plate is selectively reflected by the reflective film. 13. The optical scanning device according to claim 10, wherein a reflection film is formed on a part of the surface of the parallel plate on the side of the reflective imaging element, and selectively reflects only the reflected light flux reflected by the reflective imaging element. An optical scanning device, wherein the light is reflected by the reflection film. 14. The optical scanning device according to claim 8, wherein the deflecting means has a deflecting reflection surface parallel to the rotation axis, and a light beam from a light source is located near the deflecting reflection surface. An image is formed as a long line image in the main scanning corresponding direction, and the position of the deflecting / reflecting surface and the position of the surface to be scanned have a geometrically optically conjugate relationship with respect to the sub-scanning corresponding direction. An optical scanning device characterized by the above. 15. A light beam from a light source is deflected at a constant angular velocity in a plane by a deflecting means, the deflected light beam is reflected by a reflection image forming element, and the reflected light beam is scanned by the image forming operation of the reflection image forming element. An apparatus for performing light scanning by converging light as a light spot thereon, wherein the reflective imaging element has a function of performing light scanning by the light spot at a substantially constant speed, A long prism having a wedge-shaped cross section is provided in parallel with the main scanning direction between the image forming element and the optical path from the deflecting means to the reflective image forming element and from the reflective image forming element to the surface to be scanned. An optical scanning device for separating an optical path. 16. An optical scanning device according to claim 15, wherein: in order to correct the curvature of the scanning line on the surface to be scanned,
An optical scanning device, wherein the reflection imaging element is provided with a predetermined shift amount shifted in a direction orthogonal to the beam deflection surface. 17. An optical scanning device according to claim 15, wherein: in order to correct the bending of the scanning line on the surface to be scanned,
An optical scanning device, wherein the reflection imaging element is provided so that its optical axis is inclined by a predetermined tilt amount with respect to a beam deflection surface. 18. The optical scanning device according to claim 16, wherein the reflection surface of the reflection imaging element is a coaxial spherical or aspherical surface. 19. An optical scanning device according to claim 15, wherein the deflecting means has a deflecting / reflecting surface parallel to the rotation axis, the reflecting / imaging element is anamorphic, and a position of the deflecting / reflecting surface of the deflecting means. And the surface to be scanned are geometrically conjugated in the sub-scanning corresponding direction, and the light beam from the light source is formed as a long line image in the main scanning corresponding direction in the sub-scanning corresponding direction near the deflecting reflection surface. An optical scanning device characterized in that: 20. A luminous flux from a light source is deflected at a constant angular velocity in a plane by a deflecting means having a deflecting / reflecting surface which rotates at a constant speed, and the deflecting luminous flux is reflected by an anamorphic reflective imaging element. An apparatus for performing optical scanning by condensing light as a light spot on a surface to be scanned by an imaging action of an imaging element, wherein the reflective imaging element performs optical scanning by the light spot substantially at a constant speed. A transparent parallel plate is disposed between the deflecting means and the reflective imaging element so as to be inclined by a finite inclination angle with respect to the rotation axis of the deflecting means, and the light is reflected from the deflecting means. The optical path toward the imaging element and the optical path from the reflective imaging element to the surface to be scanned are separated, the reflective imaging element is tilted by a predetermined tilt amount with respect to the beam deflecting surface, and the material and thickness of the parallel plate , Tilt angle, reflection imager above An optical scanning device, wherein an inclination angle of a sub-element with respect to a beam deflection surface is determined so as to correct the bending of a scanning line. 21. The optical scanning device according to claim 20, wherein both the deflected light beam incident on the reflection imaging element and the light beam reflected by the reflection imaging element are transmitted through a parallel plate. Optical scanning device. 22. The optical scanning device according to claim 20, wherein, out of the deflecting light beam incident on the reflection imaging element and the reflection light beam reflected by the reflection imaging element, only the deflection light beam incident on the reflection imaging element is a parallel plate. An optical scanning device characterized by transmitting light. 23. The optical scanning device according to claim 20, wherein the inclination angle of the parallel plate is determined so that the incident angle of the deflected light beam incident on the parallel plate substantially satisfies the Brewster angle. Optical scanning device. 24. The optical scanning device according to claim 21, wherein a reflection film is formed on a part of the plane of the parallel plate on the side of the deflecting means.
An optical scanning device, wherein only a reflected light beam reflected by a reflective imaging element and transmitted through a parallel plate is selectively reflected by the reflective film. 25. The optical scanning device according to claim 22, wherein a reflection film is formed on a part of the surface of the parallel plate on the side of the reflective imaging element, and only the reflected light flux reflected by the reflective imaging element is selectively formed. An optical scanning device, wherein the light is reflected by the reflection film. 26. The optical scanning device according to claim 20, wherein the deflecting means has a deflecting / reflecting surface parallel to the rotation axis, and the luminous flux from the light source is in the vicinity of the deflecting / reflecting surface. In the main scanning direction, a line image is formed as a long line image, and the position of the deflecting / reflecting surface and the position of the surface to be scanned are geometrically and optically substantially conjugated with respect to the sub-scanning corresponding direction. An optical scanning device characterized in that: 27. A light beam from a light source is deflected by a deflecting means having a deflecting / reflecting surface rotating at a constant speed, the deflected light beam is reflected by an anamorphic reflection / imaging element, and the reflected light beam is imaged by the reflection / imaging element. An apparatus for performing optical scanning by condensing light as a light spot on a surface to be scanned by an operation, wherein the reflective imaging element has a function of performing optical scanning by the light spot substantially at a constant speed, A transparent parallel flat plate is provided between the deflecting means and the reflective imaging element so as to be inclined by a finite inclination angle with respect to the rotation axis of the deflecting means, and an incident light beam is incident on the deflecting / reflecting surface of the deflecting means. Is inclined with respect to the beam polarization plane, thereby separating the optical path from the deflecting means to the reflective imaging element and the optical path from the reflective imaging element to the surface to be scanned. The inclination The optical scanning device in which light shift, curvature of the scanning line, characterized in that the determined as correction for the reflective image forming element of the deflected beam. 28. A light beam from a light source is deflected by a deflecting means having a deflecting / reflecting surface rotating at a constant speed, the deflected light beam is reflected by an anamorphic reflection imaging element, and the reflected light beam is imaged by the reflection imaging element. An apparatus for performing optical scanning by condensing light as a light spot on a surface to be scanned by an operation, wherein the reflective imaging element has a function of performing optical scanning by the light spot substantially at a constant speed, A transparent parallel flat plate is provided between the deflecting means and the reflective imaging element so as to be inclined by a finite inclination angle with respect to the rotation axis of the deflecting means, and an incident light beam is incident on the deflecting / reflecting surface of the deflecting means. Is incident on the beam polarization plane at an angle to separate the optical path from the deflecting means to the reflective imaging element and the optical path from the reflective imaging element to the surface to be scanned, and the reflective imaging element Its optical axis The parallel plate is disposed so as to be tilted by a predetermined tilt amount with respect to the beam deflecting surface, and the material, thickness, tilt angle, and tilt amount of the reflective imaging element are set so that the bending of the scanning line is corrected. An optical scanning device, comprising: 29. The optical scanning device according to claim 27, wherein the reflective imaging element is disposed so that its optical axis is inclined by a predetermined tilt amount with respect to the beam deflection surface, and the material, thickness, An optical scanning device, wherein an inclination angle, a light shift amount, and a tilt amount are determined so as to correct the bending of a scanning line. 30. The optical scanning device according to claim 27, wherein the deflected light beam incident on the reflection imaging element and the reflection light beam reflected by the reflection imaging element both pass through a parallel flat plate. An optical scanning device characterized by the above-mentioned. 31. The optical scanning device according to claim 27, wherein only the deflected light beam incident on the reflection imaging element is selected from the deflected light beam incident on the reflection imaging element and the reflection light beam reflected by the reflection imaging element. An optical scanning device characterized by transmitting light through a parallel plate. 32. The optical scanning device according to claim 27, wherein the inclination angle of the parallel plate is adjusted so that the incident angle of the deflected light beam incident on the parallel plate substantially satisfies the Brewster angle. An optical scanning device characterized in that: 33. The optical scanning device according to claim 30, wherein a reflection film is formed on a part of the surface of the parallel plate on the side of the deflecting means.
An optical scanning device, wherein only a reflected light beam reflected by a reflective imaging element and transmitted through a parallel plate is selectively reflected by the reflective film. 34. The optical scanning device according to claim 30, wherein a reflection film is formed on a part of the surface of the parallel plate on the side of the reflection imaging element, and only the reflected light flux reflected by the reflection imaging element is selectively provided. An optical scanning device, wherein the light is reflected by the reflection film. 35. The optical scanning device according to claim 27, 28, 29, 30, 31, 32, 33, or 34, wherein the deflecting means has a deflecting / reflecting surface parallel to the rotation axis, and the luminous flux from the light source is An image is formed as a long line image in the main scanning corresponding direction in the vicinity of the deflecting reflecting surface, and the position of the deflecting reflecting surface and the position of the surface to be scanned are substantially geometrically optically related to the sub-scanning corresponding direction by the reflective imaging element. An optical scanning device having a conjugate relationship.