JPH09159949A - Multi-beam optical recorder - Google Patents

Abstract

There is provided a multi-beam recording apparatus that appropriately adjusts an array interval of a light spot row for scanning a photosensitive drum in a sub-scanning direction according to the resolution of a recorded image. SOLUTION: Scanning line interval detecting means is provided at the optical scanning start end or the optical scanning end end of the photosensitive drum to detect the array interval of the optical spot rows scanning on the photosensitive drum in the sub-scanning direction. Further, by feeding back the light spot arrangement interval in the sub-scanning direction detected by the scanning line interval detecting means,
The scanning line spacing is adjusted by the scanning line spacing adjusting means arranged in the optical system of the optical scanning device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording device such as a laser beam printer which performs optical recording by scanning and modulating a plurality of laser beams.

[0002]

2. Description of the Related Art Regarding this type of multi-beam optical recording apparatus, there is, for example, Japanese Patent Laid-Open No. 62-239229 as a prior art. The configuration is shown in FIG.

[0003]

In this scanning device, the beam 31 emitted from the light source 30 first passes through a suitable optical device 32 at the modulator 34 to give the desired light beam shape, which is then elliptical by the optical device 32. Shaped to have a profiled section. Further, a beam splitter 33 is arranged after the optical device 32, and the beam splitter 33 is thereby arranged.
Is divided into a plurality of parallel beams. The modulated beam emitted from the modulator 34 is then imaged on the photoconductor 38 by the image forming optical device 35, the rotary scanning polygon mirror 36, and the anamorphic image forming lens 37, and a plurality of proximity beams are formed on the photoconductor 38. The scanning lines are scanned simultaneously.

However, in the scanning device having the above-mentioned configuration, each component constituting the optical system is designed according to the resolution of the recorded image and the lens arrangement position and the like are adjusted, so that when the resolution of the recorded image changes, It cannot be handled as it is.
Therefore, it has been difficult to handle image data having different resolutions with one scanning device.

An object of the present invention is to provide an optical scanning device which performs optical recording by forming an image on a photosensitive drum by a rotary polygon mirror and an Fθ lens of a laser beam composed of a plurality of beams and scanning the photosensitive drum simultaneously. It is an object of the present invention to provide a multi-beam recording apparatus capable of appropriately adjusting the arrangement interval of the optical spot rows scanning on the drum in the sub-scanning direction according to different resolutions of recorded images.

[0006]

SUMMARY OF THE INVENTION The above-mentioned object is to provide an optical scanning device for forming an image on a photosensitive drum by a rotary polygon mirror and an F.theta. In the above, it is achieved by providing scanning line interval detecting means for detecting the array interval in the sub-scanning direction of the light spot rows scanning on the photosensitive drum at the optical scanning start end or the optical scanning end end of the photosensitive drum.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1-1 shows the arrangement of each component constituting the optical system of the optical recording apparatus of the present invention and the chief ray of each beam. First, the laser beam 18 emitted from the laser light source 1 irradiates the multi-beam generation element 2 so that the incident beam becomes 2
It branches into a beam of books. A principal ray of each beam of the branched light is made parallel by a lens 3 and is incident on an AO modulator 4 (abbreviation of acousto-optic modulator). The AO modulator 4 independently modulates each beam according to the image data 15 sent from the controller 14. Then A
The chief rays of each beam emitted from the O modulator 4 are converged by the lens 5 and coincide with each other on the rotary polygon mirror 9. Rotating polygon mirror 9
The light reflected by is imaged on the photosensitive drum 11 by the rotary polygon mirror 9 and the Fθ lens 10, and a plurality of beams simultaneously scan the photosensitive drum 11 in 16 directions. Further, in this optical recording device, the cylinder lens 8 is provided in front of the rotary polygon mirror 9.
A dove prism 7 is arranged between the lens 5 and the cylinder lens 8, and the interval between the scanning lines on the photosensitive drum 11 is adjusted by rotating the dove prism 7.

Next, details of this optical system will be described with reference to FIG. FIG. 2A shows an optical system of the optical recording apparatus according to the present invention as viewed from the inside of the rotation surface of the rotary polygon mirror 9, that is, an optical system in the scanning direction on the photosensitive drum 11. FIG.
(b) is an optical system viewed from the direction perpendicular thereto, that is, an optical system in the sub-scanning direction.

In FIG. 2, the focal length of the lens 3 is f _L1
[mm] and the focal length of the lens 5 is f _L2 [mm],
Distance between multi-beam generating element 2 and lens 3, and lens 3
The distance between the AO modulator 4 and the AO modulator 4 is f _L1 , the distance between the AO modulator 4 and the lens 5 and the distance between the lens 5 and the rotary polygon mirror 9 are f _L2 . With such an arrangement, in the optical system in the scanning direction of FIG. 2, the chief ray of the laser beam branched by the multi-beam generating element 2 becomes parallel after the lens 3 is emitted, and after passing through the AO modulator 4, the lens 5 Irradiate. After that, the chief rays of the respective beams emitted from the lens 5 coincide on the rotary polygon mirror 9.

Next, each branched laser beam will be described. The light emitted from the laser light source 1 is transmitted through the multi-beam generating element 2 and then focused on the AO modulator 4 by the lens 3. The light emitted from the AO modulator 4 becomes parallel light by the lens 5, passes through the Dove prism 7 and the cylinder lens 8, and then illuminates the rotary polygon mirror 9. At this time, the AO modulator 4
Assuming that the spot diameter of the beam narrowed upward is δ [μm] and the beam interval is d [mm], the beam diameter D after exiting the lens 5 is D
Is given by D = 4λf _L2 / (πδ) [mm] …………………… (1). Here, λ is the wavelength of light. Next,
Laser light in the optical system in the sub-scanning direction in FIG. 2 will be described. In the optical system in the sub-scanning direction, the chief ray of each beam coincides with the optical axis from the emission of the laser light source 1 to the rotary polygon mirror 9. Also, regarding the beam diameter of each beam, the lens 5
Is the same as the optical system of FIG. 2 (a) up to the point where it becomes a parallel light with a beam diameter D = 4λf _L2 / (πδ) [mm], but the light emitted from the lens 5 is reflected by the cylinder lens 8. It is focused on the rotary polygon mirror 9. If the spot diameter at this time is δ ′ [μm], then δ ′ = (f _CYL / f _L2 ) δ [μm] ……………… (2) Therefore, as shown in FIG.
As described above, a light spot having a horizontal width D [mm] and a vertical width δ ′ [μm] is formed. Next, the light reflected by the rotary polygon mirror 9 is Fθ.
An image is formed on the photosensitive drum by the lens. At this time, Fθ
When the focal length of the lens is f _F θ, the diameter of the image forming spot on the photosensitive drum is expressed by the following equation.

Ω _x = (f _F θ / f _L2 ) δ [μm] (3) ω _y = mδ ′ = m (f _CYL / f _L2 ) δ [μm] (4) where ω _x is the imaging spot diameter in the scanning direction, ω _y is the imaging spot diameter in the sub-scanning direction, and m is the magnification of the Fθ lens in the sub-scanning direction. Further, if the distance between the image forming spots on the photosensitive drum is d ', then d' = d (f _F θ / f _L2 ) [mm] ............ (5) Further, the scanning line interval p'is given by p '= mp [μm] (6). Here, p is the interval in the sub-scanning direction of the light spot focused on the rotary polygon mirror 9, as shown in FIG. 3, and the rotation angle of the Dove prism 7 arranged between the lens 5 and the cylinder lens 8 is When fixed, the following equation holds. p∝ (f _CYL / f _L2 ) (7) Further, the following expression holds for the rotation angle φ of the Dove prism 7 and the inclination angle Ψ of the image spot on the photosensitive drum. Ψ = 2φ ………… (8) When f _L2 and f _CYL are fixed, p∝sin (φ) ……………… (9). Therefore, the spot diameter on the photosensitive drum is δf
_L2・ f _CYL・ f _F θ ・ m, and scanning line interval p '
Depends on f _L2 · f _CYL · φ.

Therefore, in the optical recording apparatus as described above, in order to record images having different resolutions without changing the basic structure of the optical system, the above parameters are changed and predetermined values corresponding to the respective resolutions are changed. By doing so, a resolution conversion optical system can be realized.

(Embodiment 1) Therefore, in the first embodiment of the present invention, as shown in FIG. 1-1, in the sub-scanning direction of the optical spot row for scanning the photosensitive drum 11 at the optical scanning start end of the photosensitive drum. A linear CCD 13 is provided as a scanning line interval detecting means for detecting the array interval of. FIG. 1-2 is an enlarged view of the scanning line interval detection unit. The linear CCD 13 is composed of a plurality of photodetection elements 19
It has a structure with. The number of the photodetection elements 19 is not limited, but in the present embodiment, it is assumed that the photodetection elements 19 are composed of n elements. Further, the distance between the photodetection elements is ξ.

Generally, since the light spot for scanning the surface of the photosensitive drum is a Gaussian beam, the light received by each photodetecting element 19 of the linear CCD 13 has a different light intensity for each element as shown in FIGS. Is obtained. At this time, the distance between the elements having the maximum light intensity (the distance between the 13th element and the 22nd element in FIG. 1-3) is the arrangement interval in the sub-scanning direction of the light spot rows for scanning the photosensitive drum. . Since this interval must always be a predetermined value corresponding to the resolution of the optical recording apparatus, the rotation angle adjustment of the Dove prism 7 is performed via the control circuit 20 based on the signal obtained by the scanning line interval detection unit. The mechanism 21 is provided, and when the resolution of the recorded image sent from the controller 14 is changed from α [dpi] to β [dpi], the Dove prism 7 arranged in the optical system of the optical recording device accordingly. The rotation angle of is automatically adjusted to the rotation angle that satisfies the condition of formula (10). sin (φ ') = (α / β) sin (φ) …………………… (10) (However, φ is the rotation angle of the Dove prism 7 when the resolution is α [dpi], and φ ′ is This is the rotation angle of the Dove prism 7 when the resolution is β [dpi].) By doing so, (9)
From the formula, the scanning line interval p _β after the resolution change is p _β = (α / β) p _α …………………… (11) (where p _α is the resolution when α [dpi] The scanning line interval, p _β is the scanning line interval when the resolution is β [dpi].), And an image with a resolution of β [dpi] is recorded with the same optical system as when α [dpi]. You can

Since the spot diameter on the photosensitive drum does not change in this embodiment, it is necessary to adjust the exposure amount as needed when the change in resolution is large. Further, when the resolution is changed while the process speed of the optical recording device remains constant in this embodiment, the rotation speed of the rotary polygon mirror 9 is also controlled correspondingly. That is, the resolution of the recorded image is α
When changing from [dpi] to β [dpi], the number of rotations of the rotary polygon mirror 9 is (β / α) times. On the contrary, when the resolution is changed from α [dpi] to β [dpi] while keeping the rotation speed of the rotary polygon mirror 9 constant, the process speed is multiplied by (α / β). Further, in the present embodiment, the arrangement position of the linear CCD 13 is the optical scanning start end of the photosensitive drum, but of course there is no problem even if it is the optical scanning end end of the photosensitive drum.

(Embodiment 2) In the second embodiment of the present invention, as shown in FIGS. 1-4, the scanning direction 16 of the light spot array and the arrangement direction of the photo-detecting elements forming the linear CCD 13 are arranged obliquely. To do. This is for the following reason. In the scanning line interval detecting method described in the first embodiment, the resolution of the inter-scanning line distance that can be detected does not exceed the photodetecting element array interval ξ of the linear CCD 13, so that the resolution of the recorded image becomes high and the imaging spot When the diameter is small and the scanning line interval is narrow, sufficient detection accuracy cannot be obtained.
On the other hand, there is a physical limit to narrowing the spacing ξ between the photodetector elements of the linear CCD. Therefore, in order to eliminate this inconvenience, as shown in FIG.
If D and D are arranged diagonally and the angle they make is γ,
The arrangement interval ξ ′ of the photodetecting elements 19 in the sub-scanning direction is ξ ′ = ξcos (γ) ……………… (12), and in fact, the resolution of the scanning line interval detector can be reduced. It is possible.

As described above, although the number of beams branched by the multi-beam generating element 2 is two in the first to second embodiments, the number of beams is not limited to this and may be three or more.

[0018]

As described above, according to the present invention, 1
It is possible to realize a multi-beam recording device capable of recording images having different resolutions with a single optical recording device.

[Brief description of the drawings]

FIG. 1-1 is a configuration diagram showing an optical system of a multi-beam optical recording device of the present invention.

FIG. 1-2 is an enlarged view of a scanning line interval detection unit.

FIG. 1-3 is an explanatory diagram showing a light intensity distribution received by each photodetection element that constitutes the scanning line interval detection unit.

FIG. 1-4 is an explanatory diagram showing an arrangement angle of a scanning line interval detection unit.

FIG. 2 is a configuration diagram showing a component arrangement position of an optical system of a multi-beam optical recording apparatus of the present invention.

FIG. 3 is a configuration diagram showing a conventional scanning device.

FIG. 4 is an explanatory diagram showing a light spot array formed on a rotating polygon mirror.

[Explanation of symbols]

1 ... Laser light source, 2 ... Multi-beam generating element, 3 ... Lens,
4 ... AO modulator, 5 ... Lens, 7 ... Dove prism, 8 ...
Cylinder lens, 9 ... Rotating polygon mirror, 10 ... Fθ lens,
11 ... Photosensitive drum, 12 ... Beam detector, 15 ... Image data, 21 ... Dove prism rotating mechanism, 30 ... Light source,
31 ... Outgoing beam, 32 ... Optical device, 33 ... Beam splitter, 34 ... Modulator, 35 ... Image forming optical device, 36 ...
Rotating / scanning polygon mirror, 37 ... Anamorphic image forming lens,
38 ... Photoreceptor

Claims (6)

[Claims] 1. A multi-beam optical recording apparatus, wherein a multi-beam laser beam is imaged on a photosensitive drum by a rotating polygon mirror and an Fθ lens, and the multi-beam is simultaneously scanned to perform optical recording. A multi-beam optical recording device, characterized in that a scanning line interval detecting means is provided at a start end or an end end of optical scanning to detect an array interval of light spot rows for scanning on a photosensitive drum in a sub-scanning direction. 2. The multi-beam optical recording apparatus according to claim 1, wherein the optical spot arrangement interval in the sub-scanning direction detected by the scanning line interval detecting means is fed back, and the scanning provided in the optical system of the optical scanning apparatus. A multi-beam optical recording apparatus characterized in that the line spacing adjusting means appropriately adjusts the arrangement position of the optical spot rows for scanning on the photosensitive drum in the sub-scanning direction according to the resolution of the recorded image. 3. The multi-beam optical recording apparatus according to claim 2, wherein the scanning line interval adjusting means adjusts the array position of the optical spot row for scanning on the photosensitive drum in the sub-scanning direction.
A multi-beam optical recording device characterized by using a Dove prism arranged in an optical system of the optical scanning device. 4. The multi-beam optical recording device according to claim 3, wherein when the resolution of a recorded image is changed from α [dpi] to β [dpi], the optical system of the optical recording device is arranged accordingly. A multi-beam optical recording device characterized in that the rotation angle of the Dove prism is adjusted to a rotation angle satisfying the following condition. sin (φ ') = (α / β) sin (φ) where φ is the rotation angle of the Dove prism when the resolution is α [dpi], φ ′ is the rotation of the Dove prism when the resolution is β [dpi] It is an angle. 5. A multi-beam optical recording apparatus according to claim 1, wherein a linear CCD is used as a detecting means for detecting a light spot arrangement interval in the sub-scanning direction. 6. A multi-beam optical recording apparatus according to claim 5, wherein a photo-detecting element array direction forming a linear CCD used as a light spot array interval detecting means in the sub-scanning direction scans on a photosensitive drum of the optical scanning apparatus. A multi-beam optical recording device, which is arranged vertically or obliquely with respect to the scanning line.