JP2739690B2 - Light beam scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] A correction function of a light beam scanning device, particularly a correction function of a light beam scanning device for scanning a scanning object such as a photosensitive drum of a laser printer with a light beam, is based on an eccentricity of the light beam scanning device. The purpose is to eliminate misalignment of scanning dots caused by abnormal scanning of the light beam, perform beam correction corresponding to each beam scanning element, improve the linearity of the vertical line of the printing pattern, and improve the printing quality. The first light beam scanning device is arranged so as to divide the circle into a plurality of fan-shaped regions having different center angles (θ1, θ2,..., Θn) from each other. A hologram disk that is composed of a plurality of hologram facets and diffracts the light beam output from the light beam generating means, and scans the light beam by rotating the hologram disk. Drive means, a light beam detecting means arranged in the scanning range of the light beam to detect the light beam, a beam scanning element recognizing means for recognizing each hologram facet from the output of the light beam detecting means, and a hologram facet Correction information storage means for storing correction data corresponding to the hologram facet, and light beam emission for controlling a light beam output from the light beam generation means based on the correction data for each hologram facet recognized by the beam scanning element recognition means. The second light beam scanning device is characterized by having a light beam generating means for generating a light beam and an angle of a circle formed in a prismatic shape and divided by a normal to each side surface. (Θ1, θ2,..., Θn) are different from each other, and a polygon mirror that reflects the light beam output from the light beam generating means on the side surface; A driving means for scanning the light beam by rotating the polygon mirror, a light beam detecting means arranged within the scanning range of the light beam to detect the light beam, and a driving means for detecting the light beam from the polygon mirror based on an output of the light beam detecting means. Beam scanning element recognition means for recognizing each side face, correction information storage means storing correction data corresponding to each side face of the polygon mirror, and corresponding to each side face of the polygon mirror recognized by the beam scanning element recognition means. A light beam emission / drive control unit that controls a light beam output from the light beam generation unit based on the correction data.

[Industrial applications]

The present invention relates to a light beam scanning device, and more particularly, to a correction function of a light beam scanning unit that scans a scanned object such as a photosensitive drum of a laser printer with a light beam.

In recent years, with the spread of word processors and personal computers, demands for desktop publishing and the like have increased the demand for page printers, especially semiconductor laser printers having a printing speed of medium to low speed of about 1000 lines / minute. 2. Description of the Related Art In a laser printer, a polygon mirror or a scanning optical system for scanning a light beam by rotating a hologram disk is widely used.

By the way, hologram disks and polygon mirrors
Eccentricity or the like may occur depending on a manufacturing state or a state where the apparatus is attached to a driving device or the like. When the light beam is scanned by the scanning optical system having the eccentricity, a displacement of the scanning dots may be caused in the print pattern. As a result, there is a problem that the linearity of the vertical line of the print pattern is deteriorated and the print quality is deteriorated.

Therefore, there is a demand for a light beam scanning device capable of performing beam correction corresponding to each of the beam scanning elements constituting the light beam scanning means.

[Conventional technology]

 8 and 9 are explanatory views according to a conventional example.

FIGS. 8A and 8B are explanatory views of a conventional light beam scanning device, and FIG. 8A shows a hologram scanner of a laser printer using a hologram disk.

In FIG. 1A, the hologram scanner is a simple optical system including a semiconductor laser 2, which is a light source, a hologram lens 4a, and two holographic optical elements of a hologram disk 1a. The light L emitted from the semiconductor laser 2 is diffracted by the hologram lens 4a,
Scanning is performed by the hologram disk 1a driven by the motor 3. This method does not require a collimating lens, an fθ lens, and a tilt correction optical system as compared with a method using a polygon mirror shown in FIG. Therefore, there is a feature that the number of optical components can be significantly reduced.

The hologram disk 1a is usually composed of a plurality of hologram facets, and can scan the photosensitive drum 6 with the light beam L a plurality of times in one rotation like a polygon mirror.

Reference numeral 5 denotes a light emission / drive control circuit for controlling input / output of the semiconductor laser 2 and the motor 3, and reference numeral 6 denotes a print information processing circuit.

FIG. 1B similarly shows a laser printer using a polygon mirror type light beam scanning device.

A light beam position detector 8 detects the light beam L and obtains a synchronization signal. The synchronization signal synchronizes the output of the print information with the rotating polygon mirror 1b. This is used to output a print at a specific scanning position on the photosensitive drum 6, that is, on the printing paper, and align the writing start position.

FIGS. 9 (a) to 9 (c) are diagrams for explaining problems with the conventional light beam scanning device, and FIG. 9 (a) is a top view of the hologram disk.

In FIG. 7A, ΔX is an error of the hologram disk 1a, that is, a difference between the eccentric hologram disk 10a and the normal hologram disk 1a. The eccentric hologram disk 10a is generated due to inherent distortion at the time of production or because a normal hologram disk 1a cannot be mounted properly when mounted on a rotating body such as the motor 3.

When the eccentric hologram disk 10a is rotated, the incident position of light from the hologram lens 4a changes.
Since the holograms on the hologram disk 10a have spatially different spatial frequency distributions, the scanning beams are displaced.

FIG. 1B shows a top view of the polygon mirror.

In FIG. 6B, Δθ is the error of the polygon mirror, and is the difference between the eccentric polygon mirror 10b and the normal polygon mirror 1b. Eccentric polygon mirror 10b
As in the case of the eccentric hologram disc 10a in FIG. 3A, the distortion is inherent in the manufacturing process and the normal polygon mirror 1b cannot be mounted properly when the polygon mirror 1b is mounted on a rotating body such as the motor 3. What happens.

When the eccentric polygon mirror 10b is rotated, the error Δθ changes with time with respect to the incident angle of the light beam L incident on the photosensitive drum 6, and the incident angle offset Δθ changes with time.
As (t), the light beam scanning is adversely affected.

FIG. 1C shows a dot pattern printed on a laser printer.

In the figure, ΔX is the displacement of the scanning dot, which is caused by the light beam scanning means such as the eccentric hologram disk 10a or polygon mirror 10b. For example,
The scanning dot pattern by the No. 1 beam scanning element and N
o. Differences from the scanning dot patterns by the beam scanning elements of 3 to 6. Reference numeral 9 denotes a pincushion-shaped distorted portion, in which the writing start portion of the entire print screen is linearly aligned, while the writing end portion is distorted in a curved shape.

[Problems to be solved by the invention]

By the way, according to the conventional example, the hologram disk 1a and the polygon mirror 1b are manufactured with high accuracy, and the
9 (a) and 9 (b), an eccentric hologram disk 10a or a light beam scanning means such as a polygon mirror 10b may be generated.

For this reason, when the light beam is scanned by the hologram facet or the mirror surface of the decentered light beam scanning means, the ninth light beam is scanned.
As shown in FIG. 3C, a positional shift ΔX of the scanning dot may occur at the end of the printed print pattern.

As a result, a pincushion-shaped distortion portion 9 in which the end portion of the entire print pattern is curved is generated, which causes a problem that the print quality is reduced.

The present invention has been made in view of the problems of the conventional example, and eliminates the displacement of the scanning dots caused by the abnormal scanning of the light beam due to the eccentricity of the light beam scanning means,
Perform beam correction corresponding to each beam scanning element one by one,
It is an object of the present invention to provide a light beam scanning device capable of improving the linearity of a vertical line of a print pattern and improving print quality.

[Means for solving the problem]

FIGS. 1A to 1C show principle diagrams according to the light beam scanning device of the present invention.

The apparatus includes a light beam scanning means 11 for scanning a light beam L on an object 16 to be scanned, a light beam generating means 12 for supplying the light beam L to the light beam scanning means 11, and a rotation of the light beam scanning means 11. Driving means 13, a beam correcting means 14 for correcting the light beam L, and a light emitting / driving control means 15 for controlling the input / output of the light beam generating means 12 and the driving means 13.
Wherein the light beam scanning means 11 comprises an aggregate of a plurality of beam scanning elements No. 1 to No. n, and the beam correction means 14 comprises a light beam detecting means 14a for detecting at least the light beam L. Beam scanning element recognition means 14b for identifying the beam scanning elements No. 1 to No. n, and correction information storage means 14c storing correction data D1 to Dn of the light beam L. The light beam scanning means 11 comprises a hologram disk 21 and is corrected by correction data D1 to Dn corresponding to the respective beam scanning elements No. 1 to No. n.
No. 1 to No. n are arranged so as to divide the circle into a plurality of fan-shaped regions having different center angles (θ1 to θn) (θ1 ≠ θ2 ≠... ≠ θn). The scanning means 11 comprises a polygon mirror 31,
The angles (θ1 to θn) of circles divided by the normals of the side surfaces (mirror surfaces) No1 to Non of the polygon mirror 31 are different from each other (θ1 ≠ θ2 ≠ · ≠ θn). Achieve the goal.

[Action]

According to the first apparatus of the present invention, the light beam scanning means 11
Is composed of a hologram disk 21, and the central angles θ1 to θn of the fan-shaped regions divided by the hologram facets No1 to Non of the hologram disk 21 are different from each other (θ1 ≠ θ2 ≠... ≠ θn). That is, each of the hologram facets No 1 to No n divides the circle angle 360 ° into unequal angles.

The light beam L emitted from the light beam generating means 12 is first-order diffracted by the hologram disk and reaches the light beam detecting means 14a once for each scan. The hologram facets No. 1 to No.n can be identified by measuring the time required for one scan for each of the hologram facets No. 1 to No. n. Therefore, hologram facet No.1 ~
The correction data D1 to Dn associated with No. n makes it possible to perform the correction of the light beam scanning with good reproducibility.

As a result, it is possible to eliminate the displacement of the scanning dots caused by the abnormal scanning of the light beam due to the eccentricity of the light beam scanning means as in the related art.

Further, according to the second apparatus of the present invention, the light beam scanning means 11 comprises the polygon mirror 31;
The angles θ1 to θn of circles divided by the normals l1 to ln of the side surfaces No1 to Non are different from each other (θ1 ≠ θ2 ≠ · ≠).
θn). That is, the normal line l1 of each side surface (mirror surface) No1 to Non
~ Ln divides the circle angle 360 ° into unequal angles.

The light beam L emitted from the light beam generating means 12 is reflected by the polygon mirror 31 and reaches the light beam detecting means 14a once for each scan. Each mirror surface N of polygon mirror
o By measuring the time required for one scan for each 1 to No.n, it is possible to identify each mirror surface No.1 to No.n. Therefore, the correction of the light beam scanning can be performed with good reproducibility by using the correction data D1 to Dn associated with each mirror surface.

As a result, similarly to the first apparatus, it is possible to eliminate the positional deviation of the scanning dots as in the related art.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

2 to 7 are views for explaining a light beam scanning device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a configuration of the light beam scanning device according to the first embodiment of the present invention. I have.

In the figure, reference numeral 21 denotes a hologram disk as one embodiment of the light beam scanning means 11. The hologram disk 21 is manufactured by using the technique of Japanese Patent Application No. 59-48076 already filed. The hologram disk 21 will be described in detail with reference to FIG. 4, but the embodiment of the present invention shows a case of six facets (however, FIG. 2 shows nine facets).

Reference numerals 22a and 22b denote a semiconductor laser as a light source, which is an embodiment of the light beam generating means 12, and a hologram lens for aberration correction. Reference numeral 23 denotes a motor as an embodiment of the driving means 13, which rotates the hologram disk 21. The hologram disk 21, semiconductor laser 22a, hologram lens 22b and motor 23 constitute a light beam scanner for linear scanning of Japanese Patent Application No. 60-168830 filed by the present applicant.

24a is a light beam position detector which is an embodiment of the light beam detection means 14a. 24b is a beam scanning element recognition means 1
4B is a facet recognition circuit according to the first embodiment of FIG. The function of the facet recognition circuit 24b will be described later with reference to FIG. Reference numeral 24c denotes a correction data memory as one embodiment of the correction information storage means 14c. Reference numeral 24d denotes a correction data selection output circuit, which has a function of selectively outputting correction data D1 to D6 corresponding to each facet.

The light beam position detector 24a and the facet recognition circuit 24
b, correction data memory 24c and correction data selection output circuit 24
The beam correction means 24 is constituted by d.

Reference numeral 25 denotes a light emission / drive control circuit which inputs a print basic clock φ0 and a print signal S1 from a print information processing circuit 27, and controls input / output of the semiconductor laser 22a, the correction data selection output circuit 24d, and the motor 23. Has a function.

Reference numeral 26 denotes a photosensitive drum which is one embodiment of the scanned object 16, and scans and exposes a light beam L incident from one side of the hologram disk 21 as the hologram disk 21 rotates.

Reference numeral 27 denotes a print information processing circuit which receives input data DIN and outputs a print signal S1.

FIGS. 4 (a) and (b) are explanatory diagrams relating to the hologram facet according to the first embodiment of the present invention.
Indicates the divided state.

In FIG. 5A, when the hologram disk 21 has six facets, the conventional hologram facet is
While dividing 360 ° into equal angles = 60 °, in the embodiment of the present invention, each angle is different from each other, that is,
It is divided so that θ1 ≠ θ2 ≠ · ≠ θ6.
For example, the set angle difference Δψ1, Δψ2.
{2} ... 5}, each hologram facet
The angles θ1, θ2,..., Θ6 of No. 1 to No. 6 are 61
゜, 62 ゜, 63 ゜, 64 ゜, 65 ゜ and 45 ゜.

FIG. 1B is a state diagram of hologram facets No. 1 to No. 6, showing a state in which the boundary surface between the hologram facets is different from the hologram facet of the conventional hologram disk.

Accordingly, when the light beam is incident on the hologram disk 21, the beam scanning start time intervals of the hologram facets No. 1 to No. 6 can be respectively changed.

FIG. 6 is an explanatory diagram relating to a beam scanning element recognizing means of each embodiment of the present invention.

In the figure, the facet recognition circuit 24b of the first embodiment
First, the laser beam L diffracted from each of the hologram facets No. 1 to No. 6 of the hologram disk 21 is input as a light beam detection signal S2 via a light beam position detector 24a. Next, the detection time differences T1 to T6 are measured from the time interval of the peak value of the incident intensity.

From this detection time difference T1 to T6, each hologram facet N
o.1 to No.6 can be recognized.

Thus, a laser printer apparatus to which the light beam scanning device according to the first embodiment of the present invention is applied is configured.

FIG. 7 is an operation time chart according to each embodiment of the present invention.

In the figure, it is assumed that, for example, a print basic clock φ0 and a print signal S1 of a print information processing circuit 27 are input to a light emission / drive control circuit 25, and a print to be printed on the photosensitive drum 26 is a dot pattern.

It is also assumed that the correction data memory 24c stores correction data D1 to D6 associated with hologram facets No. 1 to No. 6 of the hologram disk 21.

At this time, after each of the hologram facets No. 1 to No. 6 is identified by the facet recognition circuit 24b, the correction data selection output circuit 24d uses the correction data D1 associated with the hologram facet No. 1 to perform basic printing. Clock φ
0 is modulated. For example, the print clock φ1 after the correction of the hologram facet No. 1 is obtained by raising the print clock signal of the light beam scanning end portion earlier by Δt11 and Δt12.

Similarly, the printing basic clock φ0 is set to Δt21, Δt22 to Δt
61, Δt62, hologram facet No. 2 ~
No. 6 corrected print clocks φ2 to φ6 are obtained.

Thereby, the beams corresponding to the hologram facets No. 1 to No. 6 can be corrected.

Thus, according to the first embodiment, the light beam scanning means 11 comprises the hologram disk 21, and each of the hologram facets No. 1 to No. n of the hologram disk 21 has an unequal angle 360 ° of the circle. Angles θ1 に θ2 ≠... ≠ θn.

Therefore, the semiconductor laser 22a and the hologram lens 22b
The light beam L emitted from the light beam is first-order diffracted by the hologram disk 21 and reaches the light beam position detector 24a.
By measuring this arrival time for each of the hologram facets No. 1 to No. 6, the hologram facets No. 1 to N
On can be identified. Therefore, the correction of the light beam scanning can be improved with good reproducibility by the correction data D1 to D6 associated with the hologram facets No. 1 to No. 6.

This makes it possible to eliminate the displacement of the scanning dots caused by the abnormal scanning of the light beam due to the eccentricity of the light beam scanning means as in the related art.

FIG. 3 shows a configuration diagram of a light beam scanning device according to a second embodiment.

In the figure, the difference from the first embodiment is that the light beam scanning means 11 is constituted by a polygon mirror 31 in the second embodiment.

The polygon mirror 31 has six mirror surfaces No. 1 to No. 6 as shown in FIG. 5 in the embodiment of the present invention. Reference numeral 32b denotes a correction lens for correcting the laser beam L reflected on the polygon mirror 31 as in the related art.

32a is a semiconductor laser, 33 is a motor, 34a is a light beam position detector, 34c is a correction data memory, 34d is a correction data selection output circuit, 35 is a light emission / drive control circuit, 36 is a photosensitive drum, and 37 is print information. This is a processing circuit, and its function is the same as that of the first embodiment, so that the description is omitted.

Reference numeral 34b denotes a mirror surface recognizing means which is a second embodiment of the beam scanning recognizing means 14b. The function of the mirror surface recognition means 34b will be described later with reference to FIG.

FIG. 5 is an explanatory diagram relating to a polygon mirror according to a second embodiment of the present invention.

In the figure, when the polygon mirror 31 is a six-sided mirror, the normal line of each mirror surface of the conventional polygon mirror divides the angle 360 ° of the circle into equal angles = 60 °, whereas in the second embodiment,
Each angle is different from each other, that is, θ1 {θ2}
・ It is divided into ≠ θ6. For example, as in the first embodiment, if the set angle differences Δψ1, Δψ2... Δψ5 are 1 ゜, 2 ゜... 5 ゜, and the mirror surface of No. 1 is used as a reference, each mirror surface No. .1 ~ No.6 normal line l1 ~ l6 is 360 ° of circle,
θ1 = 61 °, θ2 = 62 °, θ3 = 63 °, θ4 = 64 °, θ
Divide into unequal angles of 5 = 65 ° and θ6 = 45 °.

Thus, when a light beam is incident on the polygon mirror 31, the beam scanning start time intervals of the six mirror surfaces No. 1 to No. 6 of each polygon mirror 31 can be respectively changed.

Next, a mirror surface recognition circuit 34b according to a second embodiment of the present invention will be described with reference to FIG.

In the figure, a mirror surface recognition circuit 34b firstly applies a laser beam L reflected from each of the mirror surfaces No. 1 to No. 6 of the polygon mirror 31 to a light beam position detector as in the first embodiment.
It is input as a light beam detection signal S2 via 34a. Next, the detection time differences T1 to T6 are measured from the time interval of the peak value of the incident intensity.

The mirror surfaces No. 1 to No. 6 of the polygon mirror 31 can be recognized from the detection time differences T1 to T6.

Thus, a laser printer apparatus to which the light beam scanning device according to the second embodiment of the present invention is applied is constructed.

Next, the operation of the light beam scanning device according to the second embodiment of the present invention will be described with reference to FIG.

In FIG. 7, for example, in the same manner as in the first embodiment, the print basic clock φ0 and the print signal S1 of the print information processing circuit 27 are input to the light emission / drive control circuit 35. The printing to be performed is assumed to be a dot pattern.

The correction data memory 34c has a polygon mirror 31
Correction data D1 associated with each mirror surface No. 1 to No. 6
~ D6 are stored.

At this time, each mirror surface N
After o.1 to No. 6 are identified, the correction data selection circuit 34d modulates the print basic clock φ0 by the correction data D1 associated with the mirror surface No. 1. For example, the first
Similarly to the embodiment, the print clock signal at the end of scanning of the light beam is raised by Δt11 and Δt12 earlier to obtain the corrected print clock φ1 of the mirror surface No. 1.

Similarly, the printing basic clock φ0 is set to Δt21, Δt22 to Δt6.
1, the print clocks φ2 to φ6 after correction of the mirror surfaces No. 2 to No. 6 are obtained.

Thereby, it is possible to perform beam correction corresponding to each of the mirror surfaces No. 1 to No. 6.

Thus, according to the second embodiment, the light beam scanning means 11 comprises the polygon mirror 31, and the normals l1 to l6 of the mirror surfaces No. 1 to No. 6 of the polygon mirror 31 are the angles of the circle. 360 ° is divided into unequal angles θ1 ≠ θ2 ≠.

Therefore, the light beam L emitted from the semiconductor laser 32a is reflected by the polygon mirror 31 and reaches the light beam position detector 34a. This arrival time is specified for each mirror surface No. 1 to No.
By measuring every mirror surface 6, each mirror surface No. 1 to No. 6 can be identified. Accordingly, the correction of the light beam scanning can be performed with good reproducibility by using the correction data D1 to Dn associated with each of the mirror surfaces No. 1 to No. 6.

Thus, similarly to the first embodiment, it is possible to eliminate the positional deviation of the scanning dots as in the related art.

〔The invention's effect〕

As described above, according to the present invention, it is possible to recognize each beam scanning element such as a hologram facet or a mirror surface, and to correct a light beam with good reproducibility by using correction data associated with the beam scanning element.

Therefore, the light beam can be scanned with high accuracy on the object to be scanned. Therefore, the unevenness of the scanning width and the displacement of the scanning dots due to the defective production of the light beam scanning means as in the conventional example are eliminated, and high quality printing processing can be performed.

This greatly contributes to the production of highly reliable laser printers and the like.

[Brief description of the drawings]

1 (a) to 1 (c) are diagrams illustrating the principle of a light beam scanning device according to the present invention, FIG. 2 is a diagram illustrating the configuration of a light beam scanning device according to a first embodiment of the present invention, FIG. FIG. 4 is a configuration diagram of a light beam scanning device according to a second embodiment of the present invention; FIGS. 4A and 4B are explanatory diagrams of a hologram disk of the first embodiment of the present invention; FIG. 6 is an explanatory diagram relating to a polygon mirror according to a second embodiment of the present invention. FIG. 6 is an explanatory diagram relating to a beam scanning element recognizing means according to each embodiment of the present invention. FIGS. 8 (a) and 8 (b) are explanatory diagrams relating to a conventional light beam scanning apparatus, and FIGS. 9 (a) to 9 (c) are light beam scanning apparatuses according to a conventional example. It is a figure explaining a problem concerning a device. (Explanation of Signs) 11: Light Beam Scanning Unit, 12: Light Beam Generating Unit, 13: Drive Unit, 14: Beam Correction Unit, 15: Light Emission / Drive Control Unit, 21: Hologram Disc, 31 ... Polygon mirror 14a Light beam detecting means 14b Beam scanning element recognizing means 14c Correction information storage means No.1 to No.n Beam scanning elements (hologram facet, mirror surface) …… Light beam (laser beam), D1 to Dn …… Correction data.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroyuki Ikeda 1015 Kamikodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-63-225215 (JP, A) JP-A-54-89758 (JP, A) JP-A-58-97960 (JP, A)

Claims (2)

(57) [Claims] A light beam generating means for generating a light beam, and a plurality of hologram facets arranged so as to divide a circle into a plurality of fan-shaped regions having different central angles (θ1, θ2,..., Θn). A hologram disk that diffracts the light beam output from the light beam generating unit; a driving unit that scans the light beam by rotating the hologram disk; A light beam detecting means for detecting, a beam scanning element recognizing means for recognizing each hologram facet from an output of the light beam detecting means, a correction information storage means storing correction data corresponding to each hologram facet, and the beam scanning element Output from the light beam generation means based on the correction data for each hologram facet recognized by the recognition means Light beam emission to control light beam /
A light beam scanning device comprising: a driving control unit. 2. A light beam generating means for generating a light beam, and angles (.theta.1, .theta.2,..., .Theta.n) of circles formed in a prismatic shape and divided by normals of respective side surfaces are different from each other. A polygon mirror that reflects the light beam output from the beam generating means on the side surface; a driving means that scans the light beam by rotating the polygon mirror; and a light beam that is arranged within a scanning range and detects the light beam. A light beam detecting means, a beam scanning element recognizing means for recognizing each side of the polygon mirror from an output of the light beam detecting means, and a correction information storage means storing correction data corresponding to each side of the polygon mirror. A light beam output from the light beam generating means based on the correction data corresponding to each side surface of the polygon mirror recognized by the beam scanning element recognition means; A light beam emission / drive control means for controlling the light beam emission / drive control means.