JP2007188092A - Multi-beam scanner, multibeam scanning method, light source unit, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To individually detect a plurality of deflected light beams, using a synchronous photodetector in multibeam scanning. <P>SOLUTION: The multi-beam scanner is provided with the synchronous photodetectors 22, 24 for detecting deflected light beams traveling toward, the scanning region of a surface 20 to be scanned. The light source unit 10 for emitting a plurality of light beams is provided with N pieces of semiconductor lasers 1a-1c and N pieces of coupling lenses 2a-2c, corresponding thereto at 1:1 ratio. The coupling lenses are of the same structure and are set mutually nonparallel in the optical axes in the main scanning direction. In the light-receiving face position of the synchronous photodetectors, where two arbitrary deflected light beams adjacent to each other are B<SB>i</SB>, B<SB>i+1</SB>(i=1 to N-1), an angle ϕ<SB>i</SB>, formed in the main scanning direction by the optical axis of the coupling lens corresponding to the semiconductor laser that emits the beams B<SB>i</SB>, B<SB>i+1</SB>, is set so that the interval in the main scanning direction of the beams B<SB>i</SB>, B<SB>i+1</SB>becomes equal to or larger than the resolution Δ of the synchronous photodetectors. Thus, in the structure of the multi-beam scanner, each deflected light beam can be detected individually by the synchronous photodetectors. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multi-beam scanning device, a multi-beam scanning method, a light source device, and an image forming apparatus.

A plurality of deflected light beams that are radiated and deflected from the light source device are condensed toward the scanned surface by a common scanning imaging optical system, and are separated from each other in the sub-scanning direction on the scanned surface. Various types of multi-beam scanning devices that form a light spot and simultaneously scan a plurality of lines with the plurality of light spots have been proposed, and have recently been intended to be realized from the viewpoint of improving the efficiency of light scanning. ing.
In order to perform multi-beam scanning, a plurality of light beams are required, and the number of light emitting units corresponding to the number of light beams is required for the light source device.
As such a plurality of light emitting units, a semiconductor laser array can be used, or a plurality of independent semiconductor lasers can be used.
In the semiconductor laser array, since the arrayed light emitting sections are close to each other, there is a problem of so-called “crosstalk” in which the light emission intensities of adjacent light emitting sections affect each other. Is difficult.
When a plurality of independent semiconductor lasers are used as the light emitting section, there is no problem of crosstalk, and the light quantity control of each semiconductor laser can be performed with high accuracy.
In the case of multi-beam scanning, since a plurality of lines on the surface to be scanned are simultaneously scanned, it is necessary to align the “scanning start position for each deflected light beam”. To do this, the light spots formed by a plurality of deflected light beams are arranged in a line in the sub-scanning direction, and any one of the light spots is detected by the “synchronous light detecting means for starting scanning”. A method of performing the same synchronization control for all the light spots can be considered.

When a plurality of light spots are separated in the main scanning direction, the “separation amount in the main scanning direction between adjacent light spots” is set in advance as a design condition, and the light spot that starts scanning first is Based on the detection signal, the scanning start of the “light spot that starts scanning first” is synchronized, and the following light spot and “light spot that starts scanning first” are referred to below. There is a method of sequentially generating a synchronization signal for starting scanning of a subsequent light spot with a delay time corresponding to the separation amount in the main scanning direction.
When using “independent semiconductor lasers” as the light emitting part of the light source device, the mechanical accuracy of the optical system deteriorates with time due to mechanical vibration and environmental fluctuations, and the positional relationship between the light spots changes over time. In the above-described “method of synchronizing the start of scanning of another light spot with reference to one of the light spots”, an image is written with a “shift” in the scanning start position between the light spots with time. The problem of degrading can be considered.
Therefore, in order to avoid such a problem, as in the invention disclosed in Patent Document 1, a plurality of light spots are separated in the main scanning direction, and each light spot is individually detected, and a plurality of light spots are detected. It is preferable to synchronize the start of scanning individually with respect to the light spot.

JP-A-8-179229

  The present invention provides a novel multi-beam scanning device capable of individually detecting a plurality of deflected light beams by a synchronous light detecting means when a plurality of independent semiconductor lasers are used as light emitting units of a light source device in multi-beam scanning. Another object of the present invention is to realize a multi-beam scanning method, a novel light source device used in the multi-beam scanning device, and a novel image forming apparatus using the multi-beam scanning device.

The multi-beam scanning device according to the present invention basically “condenses a plurality of deflected light beams emitted and deflected from the light source device toward the surface to be scanned by the scanning imaging optical system, and on the surface to be scanned, A multi-beam scanning device that forms a plurality of light spots separated from each other in the sub-scanning direction, and simultaneously scans a plurality of lines with the plurality of light spots. A synchronizing light detecting means for detecting a deflected light beam directed toward the scanning region of the surface to be scanned.
The “scanning imaging optical system” for condensing a plurality of deflected light beams toward the surface to be scanned and forming a light spot is configured with one lens or with two or more lenses. It is also possible to adopt a configuration including one or more lenses and “one or more mirrors having an imaging function”.
As described above, the synchronization light detecting means detects the deflected light beam directed to the scanning region of the surface to be scanned. Therefore, the synchronization light detecting means has a “light receiving means”, and receives the deflected light beam by the light receiving means to generate a light receiving signal. The light receiving surface of the light receiving means is disposed at, for example, “a position equivalent to the surface to be scanned and capable of receiving a light beam directed to the scanning region”. The position equivalent to the surface to be scanned is “a position where the light beam received by the light receiving surface is substantially condensed on the light receiving surface at least in the main scanning direction”.

For example, if the light receiving surface is arranged at a position equivalent to the scanned surface and the “light beam that has passed through the scanning imaging optical system” is incident on the light receiving surface, the light receiving surface is the same as that on the scanned surface. Light spots are formed.
The scanning imaging optical system often has a long toroidal lens that has substantially no power in the main scanning direction in order to correct surface tilt and field curvature of the rotating polygon mirror. It has a “cylindrical lens”. In such a case, since the long toroidal lens or cylindrical lens does not have substantial power in the main scanning direction, the light spot in the main scanning direction is “the above-mentioned toroidal lens or cylindrical lens in the scanning imaging optical system”. It is formed by the “part excluding the lens”.
In such a case, the light receiving surface of the synchronizing light detection means is placed at a position equivalent to the surface to be scanned, and the "deflected light beam that has passed through the scanning imaging optical system excluding the toroidal lens and cylindrical lens" is received. When the light is received by the surface, what is formed on the light receiving surface is a “long oval spot having a width equivalent to the light spot in the main scanning direction and long in the sub scanning direction”. Even a spot is sufficient for use as synchronized light. In this case, a cylindrical lens can be disposed in the vicinity of the light receiving surface, and the light beam can be condensed on the light receiving surface also in the sub-scanning direction.
Of course, the light beam deflected toward the scanning region is “condensed at least in the main scanning direction on the light receiving surface of the light receiving unit of the synchronous light detecting unit by the dedicated optical system without using the scanning imaging optical system. It may be configured as follows.

Prior to explaining the invention of claim 1 and below, some reference examples of the multi-beam scanning device will be explained.
The multi-beam scanning apparatus of the first reference example (hereinafter referred to as reference example 1) has N (≧ 2) semiconductor lasers, and each of the semiconductor lasers 1 and 1 emits a plurality of light beams. And at least N coupling lenses corresponding to 1.
The N coupling lenses have the same configuration, and the optical axes are made parallel with respect to the main scanning direction. That is, the optical axes of the N coupling lenses are parallel to each other when viewed from the sub-scanning direction.
Arbitrary two deflected light beams adjacent to each other at the light receiving surface position of the synchronous light detecting means are denoted as B _i and B _{i + 1} (i = 1 to N−1). The light emitting portions of the semiconductor lasers that emit these beams B _i and B _{i + 1} are shifted by shift amounts: ζ _i and ζ _{i + 1} from the optical axis of the corresponding coupling lens in the main scanning direction. When the lateral magnification in the main scanning direction of the optical system arranged between each semiconductor laser and the light receiving surface position is M (main), the shift amount: ζ _i , with respect to the resolution: Δ of the synchronous light detection means, ζ _{i + 1} is
Δ ≦ M (Main) ・ | ζ _i −ζ _{i + 1} ｜
And each deflected light beam can be individually detected by the synchronous light detecting means.
Of the deviation amounts: ζ _i and ζ _{i + 1} (i = 1 to N−1), “zero” may be included.
“Resolution of the synchronization detection means: Δ” means that the synchronization light detection means can “separately detect two polarized light beams adjacent to each other in the main scanning direction as separate light beams”. The “limit of the amount of separation in the main scanning direction on the light receiving surface” is required. This resolution is about 0.5 mm in a photosensor which is a typical light receiving means.

In the multi-beam scanning device of the second reference example (hereinafter referred to as reference example 2), a light source device that emits a plurality of light beams has a first light source unit, a second light source unit, and beam combining means.
The “first light source unit” includes n (≧ 2) semiconductor lasers, n coupling lenses corresponding to each of these semiconductor lasers, and the n semiconductor lasers and n cups. The ring lens includes a holding body that integrally holds the n lens coupling lenses in a predetermined positional relationship with the optical axes of the n coupling lenses parallel to each other in the main scanning direction.
The “second light source section” includes m (≧ 2) semiconductor lasers, m coupling lenses corresponding to each of these semiconductor lasers, and the m semiconductor lasers and m cups. The ring lens includes a holding body that integrally holds the m lens coupling lenses in a predetermined positional relationship with the optical axes of the m coupling lenses parallel to each other in the main scanning direction.
The “beam combining unit” is a unit that combines the n light beams emitted from the first light source unit and the m light beams emitted from the second light source unit as light beams that are close to each other.
Deviation in the main scanning direction from the optical axis of the corresponding coupling lens of the light emitting part of an arbitrary semiconductor laser in the first light source part: ζ _i (i = 1 to n), and an arbitrary semiconductor in the second light source part The amount of deviation in the main scanning direction from the optical axis of the corresponding coupling lens of the laser light emitting unit: ζ _k (k = 1 to m), and the positional relationship between the first and second light source units and the beam combining means. , "At the light receiving surface position of the synchronization light detection means, the deflection light beams adjacent to each other are separated from each other in the main scanning direction by the above resolution: Δ or more". It can be detected individually.

In the multi-beam scanning device of Reference Example 2, n = m, and the first light source unit and the second light source unit can have the same structure. In this case, “each of the first and second light source units of the light source device” The semiconductor laser is press-fitted and fixed in the holding hole of the corresponding holding body, each coupling lens is fixed to the corresponding holding body with an adhesive resin, and the optical axis position with respect to the light emitting part of the corresponding semiconductor laser is adjusted by the adhesive resin. Can be configured. In this case, n = m = 2. As the “adhesive resin”, for example, “ultraviolet curable resin” can be used.
When the adhesive resin is used to fix the coupling lens to the holding body, and the optical axis position relative to the light emitting part of the semiconductor laser is adjusted by the adhesive resin (amount, etc.), the adhesive resin depends on “changes in temperature and humidity”. Since the volume changes, the relative relationship between the light emitting part and the optical axis of the coupling lens varies due to environmental changes. In such a case, if only one light spot is detected by the synchronization light detection means, and the synchronization of the scanning start positions of other light spots is fixedly controlled based on this light spot, the above-described “between light spots” However, if the light beam is detected individually by the synchronous light detection means, an appropriate timing for starting the scanning can be provided for each light beam. .

The multi-beam scanning device according to claim 1 has the following characteristics.
That is, a light source device that emits a plurality of light beams includes at least N (≧ 2) semiconductor lasers and N coupling lenses corresponding to each of these semiconductor lasers and 1: 1.
The N coupling lenses have the same configuration and “the optical axes are not parallel to each other in the main scanning direction”.
A semiconductor that emits beams B _i and B _{i + 1} when any two deflected light beams adjacent to each other at the light receiving surface position of the synchronous light detecting means are B _i and B _{i + 1} (i = 1 to N−1). The angle formed by the optical axis of the coupling lens corresponding to the laser in the main scanning direction: φ _i is such that the interval between the beams B _i and B _{i + 1 in} the main scanning direction is equal to or greater than the resolution of the above-mentioned synchronizing light detecting means: Δ. Set to Accordingly, each deflected light beam can be individually detected by the synchronous light detecting means.
The multi-beam scanning device according to claim 2 has the following characteristics.
That is, a light source device that emits a plurality of light beams has a first light source unit, a second light source unit, and beam combining means.
The “first light source unit” includes n (≧ 2) semiconductor lasers, n coupling lenses corresponding to each of these semiconductor lasers, and n semiconductor lasers and n couplings. A holding body that integrally holds the lens in a predetermined positional relationship so that the optical axes of the n coupling lenses form a predetermined angle with each other in the main scanning direction.

The “second light source unit” includes m (≧ 2) semiconductor lasers, m coupling lenses corresponding to each of these semiconductor lasers, 1: 1, m semiconductor lasers, and m couplings. And a holding body that integrally holds the lens in a predetermined positional relationship so that the optical axes of the m coupling lenses form a predetermined angle with each other in the main scanning direction.
The “beam combining unit” is a unit that combines n light beams emitted from the first light source unit and m light beams emitted from the second light source unit as light beams close to each other.
Then, the optical axis direction of each coupling lens in the first and second light source units, and the mutual positional relationship between the first and second light source units and the beam combining unit is “the mutually adjacent deflected light beams are mutually in the main scanning direction, The resolution is set to be separated by a distance greater than Δ. Accordingly, each deflected light beam can be individually detected by the synchronous light detecting means.
In the multi-beam scanning device according to claim 2, n = m, and the first light source unit and the second light source unit can have the same configuration (claim 3).
In the multi-beam scanning device according to claim 3, the light emitting portion of each semiconductor laser in the light source device can be arranged on the optical axis of the corresponding coupling lens (claim 4). Further, in the multi-beam scanning device according to claim 3, n = m = 2 can be set (claim 5).
In the multi-beam scanning device according to claim 1, of the N (≧ 2) semiconductor lasers, at least P (2 ≦ P ≦ N) light emitting units are arranged from the optical axis of the corresponding coupling lens. They can be shifted in the main scanning direction.
3. The multi-beam scanning device according to claim 2, wherein at least P (2 ≦ P ≦ n + m) light emitting units among n + m semiconductor lasers are shifted from the optical axis of the corresponding coupling lens in the main scanning direction. (Claim 7). In this case, n = m, and the first light source unit and the second light source unit can have the same configuration (claim 8). In the multi-beam scanning device according to claim 8, n = m = 2 can be set (claim 9).

The multi-beam scanning device according to claim 10 is the multi-beam scanning device according to any one of claims 1 to 9, wherein the plurality of light beams emitted from the light source device have the same deflection reflection of the optical deflector. The light source device is configured to be deflected at the same time, and is configured such that the plurality of light beams cross in the main scanning direction in the vicinity of the deflection reflection surface. The multi-beam scanning device according to claim 11 is the multi-beam scanning device according to any one of claims 1 to 10, wherein the plurality of light beams emitted from the light source device are the same deflection reflection of the optical deflector. The main scanning is configured such that a plurality of light beams from the light source device are separated in the sub-scanning direction in the vicinity of the deflection reflection surface between the light source device and the optical deflector. Line image forming optical system that forms an image as a line image that is long in the direction, and the scanning image forming optical system has a geometric optical conjugate relationship between the position of the deflecting reflection surface and the surface to be scanned in the sub-scanning direction. It is characterized by being anamorphic. By adopting such a configuration for the multi-beam scanning device, it is possible to correct surface tilt of the deflecting reflecting surface.
The “light source device” of the present invention is a light source device used in a multi-beam scanning device, and has the configuration described in any one of claims 1 to 11 (claim 12).
In the “multi-beam scanning method” of the present invention, a plurality of deflected light beams emitted and deflected from a light source device are condensed toward a surface to be scanned by a scanning imaging optical system, This is a multi-beam scanning method in which a plurality of light spots separated in the sub-scanning direction are formed and a plurality of lines are simultaneously scanned by the plurality of light spots.

A multi-beam scanning method according to claim 13 is performed using the multi-beam scanning apparatus according to any one of claims 1 to 10. A multi-beam scanning method according to claim 14 is performed using the multi-beam scanning apparatus according to claim 11.
The image forming apparatus of the present invention is an “image forming apparatus that forms a latent image on a latent image carrier by optical scanning and visualizes the latent image to obtain a desired recorded image”.
An image forming apparatus according to a fifteenth aspect uses the multi-beam scanning apparatus according to any one of the first to tenth aspects as an optical scanning apparatus that optically scans a latent image carrier. The image forming apparatus described above is characterized in that the multi-beam scanning device according to claim 11 is used as an optical scanning device that optically scans the latent image carrier.
17. The image forming apparatus according to claim 15 or 16, wherein the latent image carrier is a photoconductive photosensitive member, and an electrostatic latent image is formed by uniform charging and optical scanning, and the formed electrostatic latent image is It can be configured to be visualized as a toner image. The toner image is fixed on a sheet-like recording medium (transfer paper or a plastic sheet for an overhead projector).
In the image forming apparatus according to claim 15 or 16, for example, a silver salt photographic film may be used as the photosensitive medium. In this case, the latent image formed by the optical scanning by the multi-beam scanning device can be visualized by a developing method of a normal silver salt photographic process.
Such an image forming apparatus can be implemented as, for example, an “optical plate making apparatus”.
The image forming apparatus according to claim 17 can be implemented specifically as a laser printer, a laser plotter, a digital copying machine, a facsimile machine, or the like.
As described above, in the multi-beam scanning device, a plurality of light spots must be separated from each other in the sub-scanning direction on the surface to be scanned. Various methods can be used to separate a plurality of light spots on the surface to be scanned in the sub-scanning direction.
When the light source device has a plurality of semiconductor lasers and a plurality of coupling lenses corresponding to the semiconductor lasers, as in each of the multi-beam scanning devices described above, for example, the optical axis of the coupling lens On the other hand, the light emitting part of the corresponding semiconductor laser is shifted in the sub-scanning direction, and the “deviation amount of the light emitting part in the sub-scanning direction with respect to the optical axis of the coupling lens” is adjusted for each pair of the semiconductor laser and the coupling lens. Accordingly, the light spots may be separated from each other in the sub-scanning direction, or the optical axes of the individual coupling lenses may form a minute angle in the sub-scanning direction, and each optical axis may be in the sub-scanning direction. By adjusting the angle, the light spots can be separated from each other in the sub-scanning direction, or the direction of the optical axis and the “optical axis of the light emitting unit” By adjusting the sub-scanning direction shift amount "of al,
The light spots may be separated from each other in the sub-scanning direction.

  In addition, the coupling action of the coupling lens in the above description may be an action of making a divergent light beam from the light emitting part of the corresponding semiconductor laser a parallel beam, or an action of making a divergent or convergent light beam. But you can.

As described above, according to the present invention, a novel multi-beam scanning device, multi-beam scanning method, light source device, and image forming apparatus can be realized.
In the multi-beam scanning apparatus and the multi-beam scanning method of the present invention, since the plurality of deflected light beams directed to the scanning region to simultaneously scan the surface to be scanned can be individually detected by the synchronous light detecting means, the scanning start timing is set. Since each deflection light beam can be set independently and the writing start position of an image written by simultaneous scanning can be aligned with respect to all the deflection light beams, extremely good image writing can be realized.
In addition, the light source device of the present invention separates a plurality of simultaneously deflected light beams in the main scanning direction so that they can be individually detected on the way to the scanning region. It can be tightened. In addition, since the image forming apparatus of the present invention performs image writing using the multi-beam scanning device, high-speed and good image formation is possible.
Further, as in the multi-beam scanning device according to claims 3 and 5, the first and second light source parts used in the light source device have the same structure, so that the cost of the light source device can be reduced by sharing parts. Can be achieved.

The multi-beam scanning will be described based on the example of the multi-beam scanning apparatus of Reference Example 1 described above. The configuration of the multi-beam scanning device shown in FIG. 1A is an example of the basic configuration of the reference examples 1 and 2 and the multi-beam scanning device of the present invention.
In FIG. 1A, three light beams are emitted from the light source device indicated by reference numeral 10 (only one light beam emitted from the light source device 10 is drawn in order to avoid complication of the drawing). ) Each emitted light beam (which is a substantially parallel beam) enters a cylindrical lens 12 as a line image imaging optical system. The cylindrical lens 12 has a positive power only in the sub-scanning direction, converges the three incident light beams only in the sub-scanning direction, and is in the vicinity of the deflection reflection surface of the rotary polygon mirror 14 as an optical deflector. Then, it is formed as a long line image in the main scanning direction. A line image is formed for each light beam, and each line image is separated from each other in the sub-scanning direction.
When the rotary polygon mirror 14 is rotated at a constant speed in the direction of the arrow by a motor (not shown), the three light beams reflected by the deflecting / reflecting surface are respectively deflected light beams and deflected at an equal angular velocity.
Each deflected light beam is incident on an fθ lens 16 serving as a scanning imaging optical system while being deflected, and after passing through the fθ lens 16, is reflected by a folding mirror 18 that is a long plane mirror to bend an optical path, thereby scanning a surface to be scanned. Is condensed as a light spot by the action of the fθ lens 16 on the peripheral surface of the photoconductor 20 forming the above structure.
The three light spots formed on the surface to be scanned are separated from each other in the sub-scanning direction, and three lines on the surface to be scanned are simultaneously scanned at a time as shown in the figure.
A plane mirror 22 is disposed in the vicinity of the “scanning start side end” in the longitudinal direction of the folding mirror 18. The portion where the plane mirror 22 is disposed is outside the effective deflection area necessary for the deflection light beam to scan the effective scanning area of the surface to be scanned. The deflected light beam reflected by the plane mirror 22 enters a photosensor 24 that is a light receiving means for detecting synchronous light. That is, each deflected light beam is incident on the plane mirror 22 and reflected on the way to the scanning area of the surface to be scanned while being deflected, and is incident on the photosensor 24 and received. The light receiving surface of the photosensor 24 is arranged at “a position optically equivalent to the surface to be scanned”. Since each deflected light beam incident on the plane mirror 22 is subjected to the optical action of the fθ lens 16, each deflected light beam is condensed on the light receiving surface of the photosensor 24 as a light spot similar to that on the scanned surface.
In this apparatus example, the plane mirror 22 and the photosensor 24 constitute “synchronous light detection means”. The light receiving area of the light receiving surface of the photosensor 24 has such a size as to have a resolution: Δ (for example, 0.5 mm) in the main scanning direction.

FIG. 1B illustrates an essential part of one example of the light source device 10 in FIG. The main part of the light source device 10 includes three semiconductor lasers 1a, 1b, and 1c as light sources, and coupling lenses 2a, 2b, and 2c corresponding to these semiconductor lasers in a ratio of 1: 1. The semiconductor lasers 1a to 1c and the coupling lenses 2a to 2c have a mutual positional relationship and are held together by an appropriate holding means (not shown).
The semiconductor lasers 1a to 1c and the coupling lenses 2a to 2c have the same configuration, and are generally arranged in the main scanning direction. Further, the coupling lenses 2a to 2c convert the divergent light beams from the respective light emitting portions of the corresponding semiconductor lasers 1a to 1c into “substantially parallel beams”.
That is, the light emitting portion of each semiconductor laser is substantially located on the focal plane of the corresponding coupling lens.
FIG. 1C shows a state in which the coupling lenses 2a to 2c are arranged in the main scanning direction. The “+ sign” drawn at the center of each coupling lens indicates the optical axis position. The optical axes of the coupling lenses 2a to 2c are parallel to each other, and are directions orthogonal to the drawing in FIG. Reference numerals Ha, Hb, and Hc represent light emitting portions of the semiconductor lasers 1a, 1b, and 1c corresponding to the coupling lenses 2a, 2b, and 2c, respectively.
The light emitting part Hb is located on the optical axis of the coupling lens 2b. On the other hand, the light emitting portion Ha is shifted from the optical axis of the coupling lens 1a by “ζa” in the main scanning direction and “ξa” in the sub-scanning direction. Similarly, the light emitting portion Hc is shifted from the optical axis of the coupling lens 1c by “ζc” in the main scanning direction and “ξc” in the sub scanning direction. Such a positional relationship between the light emitting unit and the optical axis is set with high accuracy using a jig.
FIG. 1 (d) shows the behavior of the chief ray of the light beam emitted from each light emitting portion Ha, Hb, Hc.
Since the light emitting part Hb is located on the optical axis (the focal position) of the coupling lens 2b, the light beam emitted from the light emitting part Hb is converted into a parallel beam by the coupling lens 2b, and the principal ray is emitted from the coupling lens 2b. Proceeds along the optical axis.
On the other hand, since the light emitting portions Ha and Hc are shifted from the optical axes of the corresponding coupling lenses 2a and 2c, the light beams from these light emitting portions are converted into parallel beams by the corresponding coupling lenses. The direction of the light beam is refracted by the coupling lens, as indicated by the solid line in the figure. Therefore, the direction of the principal ray of the light beam converted into a parallel beam by the coupling lenses 2a and 2c is inclined with respect to the optical axis of the coupling lenses 2a and 2c.

The three light beams emitted from the light source device 10 form light spots on the scanned surface and the light receiving surface of the photosensor 24 as described above.
FIG. 1E shows the state of the light spot on the light receiving surface of the photosensor 24 as an explanatory diagram. The state of the light spot formed on the surface to be scanned is similar to this.
In FIG. 1E, “light spots” denoted by reference characters Sa, Sb, and Sc are formed by light beams emitted from the semiconductor lasers 1a, 1b, and 1c, respectively. These optical spots Sa, Sb, and Sc are optically images of the light emitting portions Ha, Hb, and Hc by the coupling lenses 2a, 2b, and 2c, the cylindrical lens 12, and the fθ lens 16. Each light spot is made into an “elliptical shape” that is slightly longer in the sub-scanning direction by adjusting the “aperture size” of the beam shaping aperture disposed at an appropriate position between the light source and the optical deflector. Has been.
As shown in FIG. 1E, with the light spot Sb as the center, the light spot Sa is shifted by “δab” in the main scanning direction, is shifted by “ηab” in the sub-scanning direction, and the light spot Sc is shifted in the main scanning direction. It is shifted by “δbc” and shifted by “ηbc” in the sub-scanning direction.
Considering a “combining optical system” of the coupling lenses 2a to 2c (which are optically equivalent as described above), the cylindrical lens 12 and the fθ lens 16, this combining optical system is in the main scanning direction. And the above-described δab, δbc, ηab, ηbc, where the horizontal magnification of image formation is M (main) in the main scanning direction and M (sub) in the subscanning direction. Respectively
δab = M (main) · ζa, δbc = M (main) · ζc
ηab = M (sub) · ξa, ηbc = M (sub) · ξc
Given in.
Since ηab and ηbc are scanning line intervals between adjacent two lines that are scanned simultaneously, the light emitting portions Ha and Hc are set so that “ηab = ηbc”, that is, | ξa | = | ξc |. “The amount of deviation in the sub-scanning direction with respect to the optical axis of the coupling lens” is set.

On the other hand, with respect to δab and δbc, since the light spot formed by each deflected light beam on the light receiving surface of the photosensor 24 needs to be detected separately by the photosensor 24, the above δab and δbc are the photosensor 24. In the main scanning direction, the resolution must be greater than Δ. That is,
Δ ≦ δab and Δ ≦ δbc
By satisfying ζa and ζc so as to satisfy the above, each light spot of the three deflected light beams can be separately detected by the same photosensor 24, so that scanning by each deflected light beam is performed based on the detection result. The start position can be controlled independently, and the start position can be “aligned to the same position” with high accuracy for each deflected light beam.
As long as “Δ ≦ δab and Δ ≦ δbc” is satisfied, ζa and ζc may be ξa = ξc, or ζa ≠ ζc.
Since the composite optical system is an afocal system in the main scanning direction, the lateral magnification in the main scanning direction is f for the focal length of the coupling lenses 2a to 2c and F for the focal length of the fθ lens 16 in the main scanning direction. Then, M (main) = F / f.
In the embodiment described above, the deviation amount ζb of the light emitting portion Hb of the semiconductor laser 1b from the optical axis of the coupling lens 2b is set to 0, but ζb is a finite value other than 0. It is good.
When ζb ≠ 0,
Δ ≦ F / f | ζa−ζb | and Δ ≦ F / f | ζc−ζb |
Ζa, ζb, and ζc may be set so that In this case, ζa, ζb, and ζc in FIG. 1C are positive when they are on the right side of the optical axis and negative when they are on the left.

The multi-beam scanning device (reference example) described above condenses a plurality of deflected light beams emitted and deflected from the light source device 10 toward the surface to be scanned 20 by the scanning imaging optical system 16, and In a multi-beam scanning apparatus that forms a plurality of light spots separated in the sub-scanning direction on the scanning surface 20 and simultaneously scans a plurality of lines with the plurality of light spots, the scanning start of each deflected light beam is synchronized. For this purpose, the light source device 10 that has the synchronized light detection means 22 and 24 for detecting the deflected light beam directed toward the scanning region of the surface to be scanned and emits a plurality of light beams has N (= 3) semiconductor lasers 1a. -1c and each of these semiconductor lasers and N coupling lenses 2a-2c corresponding to 1: 1, and the N coupling lenses 2a-2c have the same configuration. The optical axes are parallel to each other with respect to the main scanning direction, and the light beams from the corresponding semiconductor lasers are made into substantially parallel beams. The beams are B _i and B _{i + 1} (i = 1 to 2), and the amount of deviation in the main scanning direction from the optical axis of the corresponding coupling lens of the light emitting part of the semiconductor laser that emits these beams B _i and B _{i + 1} is ζ. _{When i} , ζ _{i + 1} (ζa to ζc), the horizontal magnification in the main scanning direction: M (main) and the resolution of the synchronous light detection means of the optical system arranged between each semiconductor laser and the light receiving surface position: With respect to Δ, the deviation amounts: ζ _i , ζ _{i + 1} are set so as to satisfy the relationship: Δ ≦ M (main) · | ζ _i −ζ _{i + 1} | Multi-beam running that can be individually detected by means Inspection device.
In the above apparatus example, the optical axes of the coupling lenses 2a to 2c are parallel to each other. However, they are parallel to each other only in the main scanning direction (that is, parallel to each other when viewed from the sub scanning direction). With respect to the sub-scanning direction, the optical axes may form a minute angle. In this case, even if the shift amount is set as ξa = ξb = ξc = 0, the optical axes form. By adjusting the small angle, the light spot can be separated in the sub-scanning direction.

2 and 3 are diagrams for explaining an example of a light source device that can be used as the light source device of the multi-beam scanning device shown in FIG. In addition, in order to avoid complication, the same code | symbol is used throughout FIG.
FIG. 2A is a diagram for explaining the structure of the main part of the light source device.
Reference numerals 1a, 1b, 1c, and 1d indicate semiconductor lasers, and reference numerals 2a, 2b, 2c, and 2d indicate "coupling lenses corresponding to each of the semiconductor lasers 1a, 1b, 1c, and 1d and 1: 1". Reference numerals 3A and 3B denote holders, and reference numeral 4 denotes a prism as beam combining means.
The semiconductor lasers 1a, 1b, 1c, and 1d have the same configuration, and the coupling lenses 2a, 2b, 2c, and 2d also have the same configuration. Each coupling lens is set so that the light beam from the corresponding semiconductor laser is converted into a parallel beam.
The holding bodies 3A and 3B have the same configuration.
The holding body 3A, the semiconductor lasers 1a and 1b, and the coupling lenses 2a and 2b constitute a “first light source unit”. The holding body 3B, the semiconductor lasers 1c and 1d, and the coupling lenses 2c and 2d constitute a “second light source unit”.
Since the first and second light source units have “similar configurations”, the first light source unit will be described as an example. FIG. 2B is a view of the holding body 3A of the first light source unit as viewed from the front side, and the CC ′ section of FIG. 2B is drawn together with the semiconductor laser and the coupling lens. ).
As shown in FIGS. 2B and 2C, the base portion 300 of the holding body 3A has a plate shape, and a convex portion 301 for holding a lens is formed at the center portion thereof, and light beam passing through both sides of the convex portion 301 are formed. Through-holes 302 and 303 are formed so as to sandwich the convex portion 301 therebetween. The through holes 302 and 303 penetrate the base 300 in the thickness direction and are “parallel to each other”. The diameters of the through holes 302 and 303 in the vicinity of the rear side outlet of the base 300 are enlarged, and the semiconductor lasers 1a and 1b are press-fitted and fixed to these portions (FIG. 2 (c)). Therefore, the positions of the light emitting portions of the semiconductor lasers 1a and 1b are uniquely determined with respect to the through holes 302 and 303.

In addition, coupling lenses 2a and 2b are fixedly provided on the convex portion 301 so as to sandwich the convex portion 301 with their optical axes parallel to each other. 2B and 2C, reference numerals 304 and 305 denote fixing screw holes.
The second light source unit is configured by fixedly holding the semiconductor lasers 1c and 1d and the coupling lenses 2c and 2d (see FIG. 2A) on the holding body 3B, like the first light source unit.
The first light source unit and the second light source unit are arranged to face the incident side surface of the prism 4 with the optical axes of the respective coupling lenses being parallel to each other.
Referring to FIG. 3 (a), this figure is a diagram for explaining the attachment state of the coupling lens to the holding body as an example of the attachment state of the coupling lens 2b to the holding body 3A. As shown in the drawing, the side surface of the convex portion 301 is formed as a concave cylindrical surface, and this cylindrical surface is a reference surface for mounting the coupling lens 2b.
The coupling lens 2b is coated with an ultraviolet curable resin 310 on the edge portion thereof, and the ultraviolet curable resin 310 is brought into contact with the cylindrical surface portion. The coupling lens 2b has a positional relationship (shift amount in the main scanning direction: ζb) between the optical axis (denoted by “+”) and the light emitting portion Hb of the semiconductor laser 1b (fixed position fixed to the holding body 3A). The amount of deviation in the sub-scanning direction: ξb) and the position in the optical axis direction are adjusted by a jig (not shown). When the ultraviolet curable resin 310 is irradiated with ultraviolet rays and the resin is cured with the position adjusted in this manner, the coupling lens 2b is fixedly bonded to the convex portion 301. The “holding on the corresponding holding body” of the other coupling lenses 2a, 2c, and 2d is performed in the same manner.
FIG. 3B is a diagram for explaining the state of beam synthesis by the prism 4 with respect to the light beams emitted from the light emitting portions Ha and Hc. The prism 4 has a side shape as shown in FIG. The prism 4 has a configuration in which a parallelogram prism and a right-angle prism are combined, and a polarizing reflection film 401 is formed at a joint portion between both prisms. Further, a half-wave plate 403 is provided at a site where the light beam from the light emitting unit Hc is incident (not shown, but also the light beam from the light emitting unit Hd is incident).

The position of the light source is determined so that the light emitted from the light emitting portions Ha and Hb is both P-polarized with respect to the polarization reflection film 401. Therefore, a light beam emitted from the light emitting unit Ha and converted into a parallel beam by the coupling lens 2a (not shown, but also a light beam emitted from the light emitting unit Hb and converted into a parallel beam by the coupling lens 2b) When entering the prism 4, the light passes through the polarization reflection film 401 and exits from the prism 4. On the other hand, a light beam emitted from the light emitting part Hc and converted into a parallel beam by the coupling lens 2c (not shown, but also a light beam emitted from the light emitting part Hd and converted into a parallel beam by the coupling lens 2d) By passing through the half-wave plate 403, the polarized light reflecting film 401 becomes S-polarized light. Then, the light is totally reflected by the prism surface 402 of the prism 4, further totally reflected by the polarization reflection film 401, and enters from the prism 4.
In this way, the four light beams emitted from the prism 4 (all of which are parallel beams) are combined as light beams that are close to each other.
Of the four light beams emitted from the prism 4, two are S-polarized light and the other two are P-polarized light, and their polarization planes are orthogonal to each other. As is well known, the reflectivity by the reflecting surface changes differently between S-polarized light and P-polarized light as the incident angle changes. Therefore, if it is “as above”, the four light beams emitted from the light source device are When reflected by the deflecting reflecting surface of the rotary polygon mirror 14 or the folding mirror 18 in FIG. 1A, the light intensity of the light spot on the scanned surface varies depending on the two light beams due to the change in reflectance. Therefore, in order to avoid such a problem, the four light beams synthesized by the prism 4 are passed through the quarter wavelength plate, and the four light beams are both “circularly polarized”. It is preferable that
FIG. 3C shows a state in which the light source device 10 is viewed obliquely from the rear. The prism 4 is accommodated in a box-like casing indicated by reference numeral 5 in a predetermined state. The rear plate of the casing 5 is provided with semiconductor lasers 1a and 1b and coupling lenses 2a and 2b (not shown). 3A) and a holding body 3B in which the semiconductor lasers 1c and 1d and the coupling lenses 2c and 2d (not shown) are integrated are formed in the rear plate. The convex part of the holding body (with the coupling lens fixed) is fitted into the hole, and the mounting state is adjusted and fixed. The four combined light beams (parallel beams) are emitted from a cylindrical injection port 5 </ b> A formed in the casing 5. The exit 5A is provided with the above-described “¼ wavelength plate” and an aperture for performing beam shaping. Therefore, all of the four parallel light beams emitted from the light source device 10 are shaped into circularly polarized light.

The four light beams emitted from the light source device 10 are separated from each other in the sub-scanning direction by the cylindrical lens 12 in the vicinity of the deflection reflection surface of the rotary polygon mirror 14 as shown in FIG. Is formed into a "long line image", is converted into a deflected light beam by a rotating polygon mirror, and a light spot separated in the sub-scanning direction is formed on the surface to be scanned, which is the peripheral surface of the photoreceptor 20, by the action of the fθ lens 16. To do. Then, four lines (four scanning lines) on the surface to be scanned are simultaneously scanned by these four light spots.
FIG. 4A illustrates the combined state of the prisms 4 in an explanatory manner. When the prism 4 is combined, the center between the optical axes of the coupling lenses 2a and 2b and the center between the optical axes of the coupling lenses 2c and 2d are in the position shown in FIG. As follows. In order to avoid complication of the drawing, the coupling lens 2a and the coupling lens 2c are drawn to overlap each other, and the coupling lens 2b and the coupling lens 2d are drawn to overlap each other. Since the optical axes of the coupling lenses are parallel to each other, and the coupling action is to convert the light beam from the semiconductor laser into a parallel beam, as long as the center between the optical axes coincides at the position q, the individual couplings The position of the lens may be anywhere, and therefore the generality of the following description is not lost even if two coupling lenses are drawn one by one as shown in FIG.
The shift amounts of the light emitting portions Ha and Hc of the semiconductor lasers 1a and 1c relative to the optical axes (indicated by “+” marks) of the coupling lenses 2a and 2c are related to ζa and ζc and the sub-scanning direction with respect to the main scanning direction. Let ξa and ξc. Similarly, the shift amounts of the light emitting portions Hb, Hd of the semiconductor lasers 1b, 1d relative to the optical axes (indicated by “+” marks) of the coupling lenses 2b, 2d are ζb, ζd, Let ξb and ξd be related to the scanning direction.
At this time, if 3 | ζa | = | ζc |, 3 | ζb | = | ζd |, and 3 | ξa | = | ξc |, 3 | ξb | = | ξd | In addition, the light spots Sa, Sb, Sc, and Sd formed on the light receiving surface of the photosensor 24 are as shown in FIG. “Q” is an image of the position: q by the cylindrical lens 12 and the fθ lens 16.

If the “intervals in the main scanning direction” between adjacent light spots are δab, δac, and δbd as shown in the figure, these are described below using the imaging magnification: M (main) (= F / f). It is expressed as
δab = M (main) | ζb−ζa |
δac = M (main) | ζc−ζa |
δbd = M (main) | ζd−ζb |
In order to detect individual light spots separately by the photosensor 24 using the resolution in the main scanning direction: Δ in the photosensor 24,
δab ≦ Δ, δac ≦ Δ, δbd ≦ Δ
It is sufficient that the three conditions are satisfied independently. In other words, the shift amounts: ζa, ζc, ζb, and ζd may be set in accordance with the imaging magnification: M (main) so that the above condition is satisfied.
Deviation amounts in the sub-scanning direction: ξa, ξb, ξc, and ξd are connected in the sub-scanning direction so that the adjacent intervals in the sub-scanning direction of the light spots Sa, Sb, Sc, and Sd match a predetermined scanning line pitch. Image magnification: Set according to M (sub).
FIG. 4C shows a case where the positions of the light emitting portions Hb and Hd in FIG. At this time, the arrangement of the light spots Sa, Sb, Sc, Sd on the surface to be scanned is as shown in FIG. That is, the arrangement state of the light spots Sa, Sb, Sc, and Sd can be appropriately adjusted by adjusting the positional relationship between the light emitting unit and the optical axis of the coupling lens.
In the case of the light spot arrangement in FIG. 4D, the conditions under which each light spot can be individually detected by the photosensor 24 are
δad ≦ Δ, δac ≦ Δ, δbd ≦ Δ
It will be easily understood in light of the above explanation.

As the light source device 10 in the multi-beam scanning device shown in FIG. 1A, a device using the “light source device whose embodiment is described in FIGS. 2 to 4” is emitted from the light source device 10 and simultaneously deflected. Are deflected toward the scanning surface 20 by the scanning imaging optical system 16, and a plurality of light spots separated in the sub-scanning direction are formed on the scanning surface. Thus, in the multi-beam scanning device that scans a plurality of lines simultaneously, synchronous light detection means 22 and 24 for detecting the deflected light beam toward the scanning region of the surface to be scanned in order to synchronize for the start of scanning by each deflected light beam. The light source device 10 that emits a plurality of light beams includes n (= 2) semiconductor lasers 1a and 1b and n coupling lasers corresponding to each of these semiconductor lasers in a ratio of 1: 1. 2a, 2b, n semiconductor lasers and n coupling lenses, with the optical axes of the n coupling lenses being parallel to each other in the main scanning direction and maintaining a predetermined positional relationship. A first light source unit having a holding body 3A for holding, m (= 2) semiconductor lasers 1c and 1d, and m coupling lenses 2c and 2d corresponding to each of these semiconductor lasers 1: 1. A holding body 3B that integrally holds the m semiconductor lasers and the m coupling lenses while keeping the optical axes of the m coupling lenses parallel to each other in the main scanning direction and maintaining a predetermined positional relationship. A second light source unit having n, n (= 2) light beams emitted from the first light source unit 3A, and m (= 2) light beams emitted from the second light source unit are close to each other. Beam to be combined as a light beam And a forming unit 4, the light emitting portion of any of the semiconductor laser in the first light source unit, a main scanning direction of the shift amount from the optical axis of the corresponding coupling lenses: ζ _i (ζa, ζb) and, second Deviation amount in the main scanning direction of the light emitting part of an arbitrary semiconductor laser in the light source part from the optical axis of the corresponding coupling lens: ζ _k (ζc, ζd), first and second light source parts, and beam combining means 4 Is set so that the deflection light beams adjacent to each other at the position of the light receiving surface of the synchronization light detection means are separated in the main scanning direction by a distance equal to or greater than the resolution of the synchronization light detection means: Δ. It is the multi-beam scanning apparatus of the reference example 2 comprised so that a deflection | deviation light beam could be detected separately by a synchronous light detection means.

The light source device described with reference to FIGS. 2 to 4 has n = m, the first light source unit and the second light source unit have the same structure, and the first and second light source units of the light source device have the same structure. Each semiconductor laser is press-fitted and fixed in the holding hole of the corresponding holding body, and each coupling lens is fixed to the corresponding holding body with an adhesive resin (see FIG. 3). The optical axis position is adjusted and n = m = 2.
In the example described above, the optical axes of the coupling lenses 2a to 2d are parallel to each other. However, these optical axes are parallel to the “main scanning direction”, and the sub-scanning direction forms a minute angle with each other. May be. As described above, when the optical axes of the coupling lenses form a minute angle with respect to the sub-scanning direction, the deviation amounts ξa to ξd of the light emitting units in the sub-scanning direction can be set to “0”. .
It is also easy to spread the example described in FIGS. 2 to 4 when the number of semiconductor lasers and coupling lenses: n and m are 3 or more.
In the example described with reference to FIGS. 1 to 4, for example, the direction of deviation of the light emitting portions Ha and Hb with respect to the optical axes of the coupling lenses 2 a and 2 b has been described as “direction away from each other”. Is not limited to such a “direction away from each other”.
With reference to FIG. 5, the case where the light emitting portions Ha and Hb are displaced with respect to the optical axes of the coupling lenses 2a and 2b will be described as an example. The light emitting portions Ha and Hb are as shown in FIG. Alternatively, they may be shifted so as to approach each other in the main scanning direction. In this case, the principal rays of the light beams converted into parallel beams by the coupling lenses 2a and 2b travel in directions away from each other in the main scanning direction. Further, as shown in FIG. 5B, the light emitting portions Ha and Hb may be shifted in the “same direction”. In this case, the traveling directions of the coupled light beams are separated from each other so as to advance in directions intersecting with each other in the main scanning direction according to the magnitude relationship between the shift amounts ζa and ζb in the main scanning direction. You can also go in the direction.

In each example described above, the relationship between the coupling optical axes is basically parallel to the main scanning direction, and the light emitting part of the semiconductor laser is in the main scanning direction with respect to the optical axis of the corresponding coupling lens. It is located at a position shifted.
In this case, when the number of deflected light beams used for the simultaneous scanning is increased, a part of the light emitting portion is disposed at a “position far away from the optical axis of the coupling lens”. Since the light flux from such a light emitting part passes through the peripheral part of the corresponding coupling lens, the wavefront aberration in the coupled light beam is increased. When such wavefront aberration increases to some extent, the spot diameter of the light spot formed on the surface to be scanned by this light beam is increased. If an image is written with such a light spot, the image quality of the written image may not achieve the desired quality.
As a measure for avoiding such a problem, it is conceivable to “make the directions of the optical axes of the coupling lenses non-parallel to each other in the main scanning direction”.
FIG. 6 conceptually shows an example of such a light source device.
The main part of the light source device 10A includes two semiconductor lasers 1a and 1b, and coupling lenses 2a and 2b corresponding to them 1: 1. The figure shows the light source device 10A as viewed from the sub-scanning direction. As shown in the figure, the optical axes of the coupling lenses 2a and 2b are "non-parallel with respect to the main scanning direction". The optical axes are in the same plane with respect to the sub-scanning direction.
The light emitting portions of the semiconductor lasers 1a and 1b are assumed to be Ha and Hb as before, and the deviation amounts of these light emitting portions from the optical axes of the coupling lenses 2a and 2b are ζa and ζb in the main scanning direction and ξa and ξb in the sub scanning direction. Then, ζa = ζb = 0, and ξa and ξb are determined so that the light spot on the scanned surface is separated by the scanning line pitch in the sub-scanning direction. In this way, it is not necessary to dispose the light emitting part far away from the optical axis of the coupling lens, and the above-mentioned problem of wavefront aberration degradation can be effectively avoided (even if the number of semiconductor lasers and coupling lenses increases) Is).

When such a light source device is used as a light source device of a multi-beam scanning device as shown in FIG. 1A, conditions under which light spots can be individually detected on the light receiving surface of the photosensor 24 equivalent to the surface to be scanned Is described as follows.
In FIG. 7, reference numeral 16 indicates a combined and unified “fθ lens 16 illustrated in FIG. 1A”. As shown in the drawing, when a light beam having a focusing angle: φ is incident on the fθ lens 16 in the main scanning direction (vertical direction in the drawing), the incident light beam has a focusing angle “ It is converted to “γφ” and imaged at a point P in the figure. Then, on the surface to be scanned 20 that is separated from the image forming point P by the distance: S, it is spread by “δ” in the main scanning direction. The “γ” is referred to as “angular magnification in the main scanning direction” of the fθ lens 16. Angular magnification: γ is uniquely determined according to the fθ lens 16.
Here, let us consider the focusing angle: φ in FIG. 7 as an “angle formed in the main scanning direction” by the principal rays of the two light beams emitted from the light source device 10A shown in FIG.
Then, the principal rays of the two light beams intersect at point P, but each light beam (deflected light beam) forms an image at the position of the scanning surface 20. Therefore, the two light spots formed by imaging on the surface to be scanned are separated by a distance δ in the main scanning direction. The distance: δ uses the angle: γφ and the distance: S in FIG.
δ = 2S · tan (γφ / 2)
It can be expressed as.
Therefore, the condition for individually detecting the two light spots is that the resolution of the photosensor 24: Δ
Δ ≦ δ = 2S · tan (γφ / 2)
Is true.
The usage mode of the fθ lens 16 is determined as a design condition, and the angular magnification: γ is also determined as a characteristic of the fθ lens 16. If the angle φ is determined, the position of the point P, and thus the distance S, is determined. Accordingly, the angle φ may be set so as to satisfy the above condition “Δ ≦ δ = 2S · tan (γφ / 2)”.
As described above, even when the number of light beams is three or more, it can be easily spread.

That is, a light source device that emits a plurality of light beams has at least N (≧ 3) semiconductor lasers and N coupling lenses corresponding to each of these semiconductor lasers and 1: 1, and N When the coupling lenses have the same configuration and the optical axes are made non-parallel to each other in the main scanning direction, any two deflected lights adjacent to each other at the position of the light receiving surface of the synchronous light detecting means. When the beams are B _i and B _{i + 1} (i = 1 to N−1), the angle formed by the optical axis of the coupling lens corresponding to the semiconductor laser emitting these beams B _i and B _{i + 1} in the main scanning direction: φ _i may be set so that “the interval between the beams B _i and B _{i + 1 in} the main scanning direction is equal to or greater than the resolution of the synchronous light detection means: Δ”.
For example, if the number of light beams emitted from the light source device is four, these beams are designated as beams B _{1 to} B ₄ , and they are sequentially adjacent at the position of the light receiving surface of the synchronous light detecting means. beam B _1, B ₂ corner in the main scanning direction: entering the phi ₁₂ f [theta] lens forms a likewise light beam B _2, B ₃ corners in the main scanning direction: entering the f [theta] lens forms a phi ₂₃ The light beams B ₃ and B ₄ are incident on the fθ lens at an angle of φ ₃₄ in the main scanning direction, and reach the light receiving surface from the position where the chief rays of the light beams B ₁ and B ₂ intersect. The distance is S ₁₂ , the distance from the position where the chief rays of the light beams B ₂ and B ₃ intersect to the light receiving surface is S ₂₃ , and the distance from the position where the chief rays of the light beams B ₃ and B ₄ intersect is the light receiving surface. if S _34, to make each light spot can be detected individually, the resolution of the synchronization light detecting means: For Δ
_{Δ ≦ 2S 12 · tan (γφ} 12/2)
_{Δ ≦ 2S 23 · tan (γφ} 23/2)
_{Δ ≦ 2S 34 · tan (γφ} 34/2)
What is necessary is just to comprise a light source device so that it may satisfy | fill. When the light emitting portion of each semiconductor laser is “not shifted (ζ = 0)” in the main scanning direction with respect to the optical axis of the corresponding coupling lens, the angle formed by the optical axis of each coupling lens in the main scanning direction is What is necessary is just to set so that it may become said angle | corner: (phi) ₁₂ , (phi) ₂₃ , and (phi) ₃₄ .

FIG. 8 shows a specific example of the light source device as shown in FIG.
Two holding holes 302 ′ and 303 ′ are formed in the holding body indicated by reference numeral 30 at an angle in the thickness direction, and the semiconductor lasers 1 a and 1 b are press-fitted and fixed to the end portions of the through holes. Coupling lenses 2a and 2b corresponding to the respective semiconductor lasers 1a and 1b are bonded and fixed to the convex portion projecting from the central portion of the holding body 30 in the same manner as described with reference to FIG. ing. However, in this example, the position of each coupling lens is adjusted so that each light emitting part of the semiconductor laser is positioned on the optical axis of the corresponding coupling lens. The optical axes of the coupling lenses 2a and 2b are non-parallel to each other in the main scanning direction as shown in the figure, and the light spots formed by the respective light beams are separated in the sub scanning direction on the surface to be scanned. In addition, the light emitting portions of the semiconductor laser corresponding to each coupling lens are formed so as to form a small angle with each other in the sub-scanning direction (instead of doing so, the two optical axes are on the same plane parallel to the main scanning direction). May be displaced from the optical axis position in the sub-scanning direction).
In this way, two light beams that are non-parallel to each other in the main scanning direction are obtained.
Each coupling lens is optically the same, and converts the divergent light beam from the light emitting section into a parallel beam.
The two light source devices as shown in FIG. 8 are used, and these are used as the first and second light source sections together with the prism 4 described above as a light source device similar to that described with reference to FIG. The two light beams from the first and second light source units can be combined by the prism 4 and emitted as four parallel light beams close to each other.
FIG. 9 is a diagram for explaining such a light source device.
In FIG. 9, reference numeral 3C denotes the light source shown in FIG. 8, which is the first light source unit. Reference numeral 3D denotes a second light source unit having a configuration similar to that of the first light source unit 3C. As shown in the figure, the first light source unit 3C and the second light source unit 3D are arranged apart by “L” in the main scanning direction, and the light beams B ₁ and B ₃ emitted from the first light source unit 3C and the second The light beams B ₂ and B ₄ emitted from the light source unit 3D are combined so as to be alternately arranged in the main scanning direction (not shown in FIG. 9, but in order to do so, the first light source unit 3C And the second light source unit 3D, in a plane parallel to the plane of FIG. 9, "straight lines that bisect the angle formed by the optical axes of the two coupling lenses" in each light source unit form an angle with each other. ) These four light beams are synthesized by a prism (not shown) (same as the prism 4 shown in FIG. 2).

These light beams B ₁ , B ₂ , B ₃ , B ₄ are light beams having the same arrangement as the beam arrangement on the scanned surface (and on the light receiving surface of the synchronous light detecting means) as shown in the right figure of FIG. If the spots S ₁ , S ₂ , S ₃ , S ₄ are to be formed, the conditions for individually detecting these light spots are the angles formed by the light beam shown in FIG. 9 in the main scanning direction: φ ₁₂ , φ _23, phi ₃₄ is the fθ lens angular magnification: gamma, resolution of synchronous optical detection means: relative delta, the above conditions:
_{Δ ≦ 2S 12 · tan (γφ} 12/2)
_{Δ ≦ 2S 23 · tan (γφ} 23/2)
_{Δ ≦ 2S 34 · tan (γφ} 34/2)
By configuring the light source device in this way, four light beams can be detected individually.
By using the light source device described with reference to FIG. 9 as the light source device 10 of the multi-beam scanning device shown in FIG. 1A, four surfaces to be scanned, which are peripheral surfaces of the photoconductor 20, are simultaneously provided. Can be scanned.
That is, in such a multi-beam scanning device, a plurality of deflected light beams emitted and deflected from the light source device 10 are condensed toward the scanned surface 20 by the scanning imaging optical system 16, and In addition, in a multi-beam scanning device that forms a plurality of light spots separated from each other in the sub-scanning direction and simultaneously scans a plurality of lines with the plurality of light spots, in order to synchronize for the start of scanning with each deflected light beam, A light source device that has synchronized light detection means 22 and 24 for detecting a deflected light beam directed toward a scanning region of a surface to be scanned and emits a plurality of light beams includes n (= 2) semiconductor lasers and these semiconductors. Each of the lasers has n coupling lenses corresponding to 1: 1, n semiconductor lasers and n coupling lenses, and the optical axes of the n coupling lenses are in the main scanning direction. A first light source unit 3C having a holding body that integrally holds a predetermined positional relationship so as to form a predetermined angle with each other, m (= 2) semiconductor lasers, and these semiconductor lasers Each of the m coupling lenses corresponding to 1: 1 and the m semiconductor lasers and the m coupling lenses have an optical axis of the m coupling lenses at a predetermined angle in the main scanning direction. The second light source unit 3D having a holding body that is integrally held in a predetermined positional relationship, the n light beams emitted from the first light source unit 3C, and the second light source unit Beam combining means for combining m light beams emitted from 3D as light beams close to each other, and the optical axis direction of each coupling lens in the first and second light source units, the first and second light sources And beam combining means The mutual positional relationship is set so that the deflected light beams adjacent to each other are separated from each other in the main scanning direction by a distance equal to or greater than the resolution of the synchronization light detection means: Δ, and each deflection light beam is individually detected by the synchronization light detection means. It is configured so that it can be detected (claim 2).

Further, when n = m, the first light source unit 3C and the second light source unit 3D have the same configuration (Claim 3), and the light emitting unit of each semiconductor laser in the light source device is arranged on the optical axis of the corresponding coupling lens. (Claim 4) and n = m = 2 (Claim 5).
In the light source device used in the invention described in claim 1 described above, generally, at least P (2 ≦ P ≦ N) of the light emitting units among the N (≧ 2) semiconductor lasers correspond to the corresponding coupling lens. The optical axis can be shifted from the optical axis in the main scanning direction.
Similarly, in the light source device described with reference to FIG. 9, at least P (2 ≦ P ≦ n + m) light emitting units among n + m semiconductor lasers are main-scanned from the optical axis of the corresponding coupling lens. In such a case, the first light source unit and the second light source unit are configured to have the same configuration with n = m (Claim 8). In addition, n = m = 2.
By displacing the light emitting part of the semiconductor laser in the main scanning direction from the optical axis of the corresponding coupling lens, the main beam direction of the collimated light beam is main scanned from the optical axis direction of the coupling lens. Since it can be deflected in the direction, the angle formed by the light beams in the main scanning direction (the aforementioned angle: φ ₂₃ or the like) can be easily adjusted.
By the way, in each of the light source devices described above, it is preferable that all the light beams emitted from the semiconductor laser are “crossed in the main scanning direction in the vicinity of the deflection reflection surface of the rotary polygon mirror 14”.
This will be described with reference to FIG. In FIG. 10, the vertical direction is the main scanning direction.
In FIG. 10A, for example, light beams from the light emitting portions Ha and Hb are incident on the deflecting / reflecting surface 14A of the rotary polygon mirror while spreading each other. Considering the point G in the main scanning direction on the surface to be scanned 20 assuming that the rotation direction of the rotary polygon mirror is the arrow direction, when the light spot of the light beam from the light emitting portion Ha is located at the point G, deflection reflection The surface 14A is at the position of the solid line, and the light beam passes through the “optical path indicated by the solid line” to reach the point G.
On the other hand, when the light beam from the light emitting portion Hb forms a light spot at the point G, the deflecting / reflecting surface 14A is rotated to the broken line position, and the light beam passes through the “optical path indicated by the broken line” to the point G. To reach.
As can be seen from this figure, when the “positions at which the light beams from the light emitting portions Ha and Hb are incident on the deflecting / reflecting surface 14A” are separated, the two light beams pass through “substantially different optical paths”, and the fθ lens 16 Therefore, the optical action of the fθ lens 16 on each light beam imaged at the point G is not the same. For this reason, optical characteristics such as aberration differ for two light beams that reach the same image height in the main scanning direction on the surface to be scanned 20, causing the scanning lines to bend, and between the image heights of the scanning line pitch. May cause fluctuations.

On the other hand, as shown in FIG. 10B, if the light beams from the light emitting portions Ha and Hb cross in the main scanning direction in the vicinity of the deflecting / reflecting surface 14A, the same image of the scanned surface 20 is obtained. The light beam (deflected light beam) heading high passes substantially the same optical path, and the above-mentioned problem of the bending of the scanning line and the accompanying “fluctuation between the image heights of the scanning line pitch” does not occur. In addition, by making all the light beams from the light source device cross in the main scanning direction in the vicinity of the deflecting reflecting surface, the inscribed circle radius of the rotating polygon mirror 14 can be reduced, and the rotating polygon mirror can be rotated at high speed. Therefore, it is advantageous for increasing the scanning speed.
The multi-beam scanning device according to claim 10, wherein a plurality of light beams emitted from the light source device are simultaneously deflected by the same deflecting reflection surface of the optical deflector in the multi-beam scanning device having various embodiments described above. The light source device is configured such that a plurality of light beams cross in the main scanning direction in the vicinity of the deflecting reflection surface.
If the light source device used in such a multi-beam scanning device is realized by, for example, the light source device shown in FIG. 9, the light beam B is adjusted by adjusting the angles: φ ₁₂ , φ ₂₃ , φ _{34 in} the figure. _What is necessary is just to make ₁ , B ₂ , B ₃ , and B ₄ cross in the main scanning direction in the vicinity of the deflecting reflecting surface.
Further, in order to realize the light source device as described with reference to FIG. 2, as shown in FIG. 11, the holding bodies 3A and 3B (shown in a simplified manner) are set in the main scanning direction (vertical direction in the figure). The light beams Ba and Bb emitted from the light emitting portions Ha and Hb and the light beams Bc and Bd emitted from the light emitting portions Hc and Hd are alternately arranged in the main scanning direction, and are separated by a distance L. Can cross in the vicinity of the deflecting and reflecting surface 14A.
FIG. 11B shows an example of the positional relationship between the coupling lenses 2a, 2b, 2c, and 2d and the relationship between the light emitting portions Ha, Hb, Hc, and Hd. Since the same holders 3A and 3B for holding the coupling lens and the semiconductor laser are used, the interval between the light emitting portions Ha and Hb; the interval between Aab and the light emitting portions Hc and Hd: Acd is the same. The relative positional relationship between each light emitting portion and the optical axis of the corresponding coupling lens is set as appropriate when the coupling lens is bonded and fixed.

In the example shown in FIG. 11B, the holding body 3B that holds the coupling lenses 2c and 2d is tilted in the longitudinal direction with respect to the holding body 3A that holds the coupling lenses 2a and 2b.
FIG. 11C shows a state in which the light emitting unit arrangement as shown in FIG. 11B is synthesized by the prism 4 (see FIG. 2) which is a beam synthesis unit. Reference numeral 2 denotes a combined virtual coupling lens. At this time, the four light spots Sa, Sb, Sc, Sd formed on the scanned surface (and on the light receiving surface of the synchronous light detecting means) by the light beams emitted from the light emitting portions Ha, Hb, Hc, Hd are shown. As shown in FIG.
In the multi-beam scanning device of FIG. 1A using each of the light source devices described above as the light source device 10, a plurality of light beams emitted from the light source device 10 are simultaneously transmitted on the same deflecting reflection surface of the optical deflector 14. A line which is configured to be deflected and which is long in the main scanning direction between the light source device 10 and the optical deflector 14 and which separates a plurality of light beams from the light source device in the sub-scanning direction in the vicinity of the deflection reflection surface. The scanning image forming optical system 16 includes a line image forming optical system 12 that forms an image, and the scanning image forming optical system 16 has an anamorphic conjugate relationship in which the deflection reflection surface position and the scanned surface position are geometrically optically conjugate in the sub-scanning direction. (Claim 11). The various light source devices described above are light source devices used in a multi-beam scanning device, and have the configuration described in any one of claims 1 to 11 (claim 12).
By using a multi-beam scanning device as described in the above embodiment, a plurality of deflected light beams emitted and deflected from the light source device are condensed toward the surface to be scanned by the scanning imaging optical system. Further, it is possible to realize a multi-beam scanning method in which a plurality of light spots separated from each other in the sub-scanning direction are formed on the surface to be scanned, and a plurality of lines are simultaneously scanned by the plurality of light spots.

As one specific example, a specific example of the apparatus of Reference Example 1 described with reference to FIG. 1 is given.
The focal length of each coupling lens in the light source device 10 is f = 27 mm, and the focal length of the fθ lens 16 in the main scanning direction is F = 225.3 mm. Therefore, the imaging magnification in the main scanning direction is M (main) (= F / f) = 8.34 times.
At this time, the condition that the light spots Sa, Sb, Sc shown in FIG. 1 (e) can be individually detected is that the resolution of the photosensor 24 is Δ = 0.5 mm, and δab, δbc in the figure is used. As described above, Δ ≦ δab = M (main) · ζa and Δ ≦ δbc = M (main) · ζc. In consideration of M (main) = 8.34 times, the shift amounts in the main scanning direction of the light emitting portions Ha and Hc with respect to the optical axis of the coupling lens: ζa and ζc are respectively ζa = ζc ≧ 0.06 mm (= 0.5). /8.34).

FIG. 12 shows an embodiment of an image forming apparatus according to the present invention.
A photoconductive photosensitive member 20 as a latent image carrier is formed in a cylindrical shape and rotates at a constant speed in the direction of an arrow, and charging means (showing a contact type by a charging roller, but a corona discharge type) And the electrostatic latent image is formed by writing by optical scanning of the multi-beam scanning device 114. The electrostatic latent image is developed by the developing unit 116, and the toner image obtained by the development is a sheet by a transfer unit (transfer / separation charger type, but may be a roller type) 120. Is transferred onto a recording medium S (transfer paper, a plastic sheet for an overhead projector, etc.) S. On the recording medium S, the transferred toner image is fixed by the fixing unit 122 and discharged out of the apparatus. Residual toner, paper dust, and the like are removed from the photoreceptor 20 after the toner image transfer by the cleaning device 124.
As the multi-beam scanning device 114, the one described in any one of claims 1 to 11 described above is used.
That is, in the image forming apparatus shown in FIG. 12, a latent image is formed on the latent image carrier 20 by optical scanning, and the latent image is visualized to obtain a desired recorded image. As the optical scanning device, the multi-beam scanning device according to claim 1 to 10 or claim 11 is used (claims 16 and 17), and the latent image carrier 20 is a photoconductive photoconductor, An electrostatic latent image is formed by the uniform charging and optical scanning, and the formed electrostatic latent image is visualized as a toner image.

It is a figure for demonstrating the reference example of a multi-beam scanning apparatus. It is a figure for demonstrating one example of a light source device. It is a figure for demonstrating the light source device of the form example of FIG. It is a figure for demonstrating an example of the formation state of the light spot when the light source device shown in FIG.2, 3 is used. It is a figure for demonstrating another example of the positional relationship of the light emission part and coupling lens in the light source device shown to FIG. It is a figure for demonstrating embodiment of the light source device in invention of Claim 1. It is a figure for demonstrating the conditions of the separate detection of each light beam in invention of Claim 1. It is a figure for demonstrating one specific example of the light source device in invention of Claim 1. It is a figure for demonstrating an example of the light source device which combines two light source devices of FIG. 8, and combines a beam with the prism which is a beam synthetic | combination means. It is a figure for demonstrating the advantage of the invention of Claim 10. It is a figure for demonstrating an example of the light source device in the multi-beam scanning apparatus of Claim 10. It is a figure for demonstrating one Embodiment of an image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b, 1c Semiconductor laser 2a, 2b, 2c Coupling lens 10 Light source device 12 Cylindrical lens (line image imaging optical system)
14 Rotating polygon mirror (optical deflector)
16 fθ lens (scanning imaging optical system)
20 photoconductor (acts as the surface to be scanned)
22 Plane mirror 24 Photo sensor

Claims (17)

A plurality of deflected light beams radiated and deflected from the light source device are condensed toward the surface to be scanned by the scanning imaging optical system, and a plurality of light spots separated from each other in the sub-scanning direction on the surface to be scanned In a multi-beam scanning apparatus that simultaneously scans a plurality of lines with these plurality of light spots,
In order to synchronize the scanning start by each deflected light beam, it has a synchronized light detecting means for detecting the deflected light beam directed to the scanning area of the scanned surface,
A light source device that emits a plurality of light beams,
At least N (≧ 2) semiconductor lasers and N coupling lenses corresponding to each of these semiconductor lasers and 1: 1,
The N coupling lenses have the same configuration, the optical axes are made non-parallel to each other in the main scanning direction,
When arbitrary two deflected light beams adjacent to each other at the light receiving surface position of the synchronous light detecting means are B _i and B _{i + 1} (i = 1 to N−1), these beams B _i and B _{i + 1.} The angle formed by the optical axis of the coupling lens corresponding to the semiconductor laser emitting the laser beam in the main scanning direction is φ _i , and the interval between the beams B _i and B _{i + 1 in} the main scanning direction is the resolution of the synchronous light detecting means. A multi-beam scanning device, wherein the multi-beam scanning device is configured to be set to be equal to or greater than Δ and to detect each of the deflected light beams individually by the synchronous light detecting means. A plurality of deflected light beams radiated and deflected from the light source device are condensed toward the surface to be scanned by the scanning imaging optical system, and a plurality of light spots separated from each other in the sub-scanning direction on the surface to be scanned In a multi-beam scanning apparatus that simultaneously scans a plurality of lines with these plurality of light spots,
In order to synchronize the scanning start by each deflected light beam, it has a synchronized light detecting means for detecting the deflected light beam directed to the scanning area of the scanned surface,
A light source device that emits a plurality of light beams,
n (≧ 2) semiconductor lasers, n coupling lenses corresponding to each of these semiconductor lasers, and the n semiconductor lasers and the n coupling lenses are connected to the n semiconductor lasers. A first light source unit having a holding body that is integrally held in a predetermined positional relationship such that the optical axes of the coupling lenses form a predetermined angle with each other in the main scanning direction;
m (≧ 2) semiconductor lasers, m coupling lenses corresponding to each of these semiconductor lasers 1: 1, the m semiconductor lasers and the m coupling lenses, A second light source unit having a holding body that is integrally held in a predetermined positional relationship such that the optical axes of the coupling lenses form a predetermined angle with each other in the main scanning direction;
Beam combining means for combining the n light beams emitted from the first light source unit and the m light beams emitted from the second light source unit as light beams close to each other;
The optical axis direction of each coupling lens in the first and second light source units, the mutual positional relationship between the first and second light source units and the beam combining unit, the deflection light beams adjacent to each other in the main scanning direction, The multi-beam scanning apparatus according to claim 1, wherein a resolution of the synchronizing light detecting means is set so as to be separated by a distance of Δ or more, and the respective deflected light beams can be individually detected by the synchronizing light detecting means. The multi-beam scanning device according to claim 2.
A multi-beam scanning device, wherein n = m and the first light source unit and the second light source unit have the same configuration. The multi-beam scanning device according to claim 3.
A multi-beam scanning device, wherein a light emitting portion of each semiconductor laser in a light source device is arranged on an optical axis of a corresponding coupling lens. The multi-beam scanning device according to claim 3.
n = m = 2, A multi-beam scanning device, wherein The multi-beam scanning device according to claim 1.
Of the N (≧ 2) semiconductor lasers, at least P (2 ≦ P ≦ N) light emitting portions are shifted in the main scanning direction from the optical axis of the corresponding coupling lens. Scanning device. The multi-beam scanning device according to claim 2.
A multi-beam scanning device characterized in that at least P (2 ≦ P ≦ n + m) light emitting portions among n + m semiconductor lasers are displaced in the main scanning direction from the optical axis of the corresponding coupling lens. The multi-beam scanning device according to claim 7.
A multi-beam scanning device, wherein n = m and the first light source unit and the second light source unit have the same configuration. The multi-beam scanning device according to claim 8.
n = m = 2, A multi-beam scanning device, wherein The multi-beam scanning device according to any one of claims 1 to 9,
A plurality of light beams emitted from the light source device are configured to be simultaneously deflected by the same deflecting reflection surface of the optical deflector,
The multi-beam scanning device, wherein the light source device is configured such that the plurality of light beams cross in the main scanning direction in the vicinity of the deflecting reflection surface. The multi-beam scanning device according to any one of claims 1 to 10,
A plurality of light beams emitted from the light source device are configured to be simultaneously deflected by the same deflecting reflection surface of the optical deflector,
A line image is formed between the light source device and the optical deflector so that a plurality of light beams from the light source device are formed in the vicinity of the deflection reflection surface as long line images in the main scanning direction separated from each other in the sub scanning direction. An image optical system,
The multi-beam scanning device according to claim 1, wherein the scanning imaging optical system is an anamorphic one in which the deflection reflection surface position and the scanning surface position are geometrically optically conjugate in the sub-scanning direction. A light source device used in a multi-beam scanning device,
It has the structure described in any 1 of Claims 1-11, The light source device characterized by the above-mentioned. A plurality of deflected light beams radiated and deflected from the light source device are condensed toward the surface to be scanned by the scanning imaging optical system, and a plurality of light spots separated from each other in the sub-scanning direction on the surface to be scanned A multi-beam scanning method of simultaneously scanning a plurality of lines with the plurality of light spots,
A multi-beam scanning method, which is performed using the multi-beam scanning device according to claim 1. A plurality of deflected light beams radiated and deflected from the light source device are condensed toward the surface to be scanned by the scanning imaging optical system, and a plurality of light spots separated from each other in the sub-scanning direction on the surface to be scanned A multi-beam scanning method of simultaneously scanning a plurality of lines with the plurality of light spots,
A multi-beam scanning method, which is performed using the multi-beam scanning device according to claim 11. In an image forming apparatus that forms a latent image on a latent image carrier by optical scanning and visualizes the latent image to obtain a desired recorded image.
An image forming apparatus using the multi-beam scanning device according to claim 1 as an optical scanning device for optically scanning a latent image carrier. In an image forming apparatus that forms a latent image on a latent image carrier by optical scanning and visualizes the latent image to obtain a desired recorded image.
An image forming apparatus using the multi-beam scanning device according to claim 11 as an optical scanning device for optically scanning a latent image carrier. The image forming apparatus according to claim 15 or 16,
The latent image carrier is a photoconductive photosensitive member, and an electrostatic latent image is formed by uniform charging and optical scanning, and the formed electrostatic latent image is visualized as a toner image. Forming equipment.

Images