JP2939813B2 - Multi-beam laser scanner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Objects of the Invention 1) Field of the Invention The present invention relates to a laser scanning device for writing an electrostatic latent image on the surface of a photoreceptor such as a digital copying machine using a laser beam that scans linearly. In particular, the present invention relates to a multi-beam laser scanning device that performs writing simultaneously with a plurality of laser beams.

2) Prior art FIGS. 4A and 4B are explanatory views of an example of a conventional laser scanning device used in a writing device of a digital copying machine. FIG. 4A shows two laser beams on a photosensitive member at the same time. FIG. 4B is a plan view of a scanning optical system for a multi-beam semiconductor laser scanning device for writing lines, and FIG. 4B is a side view of the same. This multi-beam semiconductor laser scanning device includes a multi-beam diode laser array 01 (see FIGS. 4A, 4B, 5) as a semiconductor laser light source that emits two laser beams simultaneously.

As shown in FIG. 5, the multi-beam laser diode array 01 was placed on an electrode substrate 02 on the lower surface and mounted thereon.
LD chip (laser diode chip) 03
LD chip 03 is a laser diode with two oscillation regions 06 and 07 separated by an insulating layer 05 on a chip substrate 04
It has LD1 and LD2. When a drive current is supplied from connection terminals a and b connected to an LD drive circuit (not shown) via electrodes 06a and 07b, each of the laser diodes LD1
And LD2 have the first and second polarization directions indicated by arrows.
Laser beams L1 and L2 forward, and back beams L1 ',
L2 'is emitted backward. Generally,
Since the diameter of the laser beams L1 and L1 at the time of emission is small, it can be regarded as a point, and the size of the laser beams L1 and L2 as a light source depends on the spread angle θ1. Further, the laser array 01 includes a photodiode 08, which receives the back beams L1 'and L2' and outputs a light amount signal to a connection terminal c connected to a light amount control circuit (not shown). It is arranged to be.

4A and 4B, the collimator lens 0 is provided on the optical path of the laser beams L1 and L2 emitted from the oscillation regions 06 and 07.
10. Aperture 011 having inner diameter D in the sub-scanning direction, cylindrical lens 012 having optical power only in the sub-scanning direction, mirror 013, polygon mirror (rotating polygon mirror) 01
4, a scanning optical system 017 comprising an f-θ lens 015 and a cylindrical lens 016 is provided, and a photosensitive drum 018 as a scanning surface rotatably provided around a central axis.
(That is, the surface of the photoreceptor) 018a. An optical sensor 019 is provided at an end of the photosensitive drum 018, and a beam position detection signal SOS (Start of scan, see FIG. 4A) output from the optical sensor 019 is applied to each of the laser diodes LD1 and LD2. The output timing of the image signal is set.

6 to 8 are explanatory diagrams in the case of performing a writing scan using a multi-beam. Here, the number obtained by dividing the interval r between the scanning lines scanned by the two adjacent laser beams L1 and L2 by the scanning line width p is defined as the “number of skipping lines”.

FIG. 6 is an explanatory diagram of scanning on the photosensitive member surface 018a when the number of laser beams is 2 and the number of jump lines is 1. FIGS. 6a and 6b show spots of the first and second laser beams L1 and L2 on the photoreceptor surface 018a, respectively, and their diameters are generally equal. In FIG. 8, p indicates the width of the scanning line, and r indicates the distance between the spots a and b of the laser beams L1 and L2.
A1 and b2 are the positions of the spots a and b at the time of the first scan (in the figure, displayed as scan number (1)), a2 and b2 are the positions of the second scan,. ai, bi is the ith (i =
1, 2, 3,...) Indicate the positions at the time of scanning.

In FIG. 6, at the time of the first scan, that is, the scan number (1)
After the scanning of the first and second scanning lines by the first and second laser beams L1 and L2 is performed at the same time, the scanning of the third and fourth scanning lines by the first and second laser beams L1 and L2 at the scanning number (2) Are performed simultaneously. Scanning number (3) in the same manner
Scanning of two lines is repeated in the order of (4), (5),.

Also, as shown in FIG. 7, when the number of skipped lines is 5, that is, the interval r between the two laser beams L1 and L2 is 5p.
When (p is the scanning pitch, that is, the width of one scanning line), the second laser beam L2 scans the scanning lines 2 and 4 in the scanning numbers (1) to (2) in FIG. After the scanning number (3), the second laser beam L2 scans the sixth, eighth, tenth,... Lines, and at the same time, the first laser beam L1 becomes five lines earlier than the first, third, fifth,. Scanning will be performed simultaneously.

Further, as shown in FIG. 8, when the number of interlaced lines is 3, that is, the interval r between the two laser beams L1 and L2 is 3p.
In FIG. 8, after the second laser beam L2 scans the second scan line at the scan number (1) in FIG. 8, the second laser beam L2 is changed to the fourth, sixth,... After the scan number (2).
While scanning the scanning line, the first laser beam L1
Scans the first, third, fifth,... Scan lines three lines earlier.

The outline of the conventional multi-beam laser scanning apparatus has been described with reference to FIGS.
A multi-beam laser scanning device using more than two beams has been conventionally known. In a multi-beam laser diode array used as a light source of such a multi-beam laser scanning device, the intervals between adjacent laser diodes are all set to be equal.

By the way, in the multi-beam semiconductor laser scanning device, it may be necessary to change the interval between the spots of the respective laser beams converging on the photoconductor surface. Conventionally, as disclosed in JP-A-56-42248 and JP-A-57-135914, the distance between the spots on the photoreceptor surface of a plurality of laser beams emitted from a multi-beam laser diode array is increased. Adjustments are known.

3) Problems to be Solved by the Invention However, in the conventional technique in which the distance between the spots is adjusted, the position of each spot on the surface of the photoconductor is shifted in the main scanning direction, or the distance from the laser diode is reduced. There has been a problem that the structure of the scanning optical system for converging the emitted laser beam on the surface of the photoconductor becomes complicated.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to make it possible to easily change an interval between spots of laser beams converging on a photoconductor surface of a multi-beam semiconductor laser scanning sorter.

B. Configuration of the Invention 1) Means for Solving the Problems In order to solve the problems, the surface of the photoconductor is scanned linearly and a plurality of laser beams are emitted at predetermined intervals in a direction perpendicular to the scanning direction. A multi-beam laser scanning device having three or more laser diodes (LD1, LD2, LD3,...) Each of which is driven by an independently modulated LD drive signal and emits a laser beam. In the laser diode (LD1, LD2, LD3,...), The distance between adjacent ones in a predetermined direction is set such that at least one distance is different from other distances, and The photosensitive member is provided with a greater number of laser diodes than the number of laser beams for writing and scanning, and selecting a predetermined laser diode from among the laser diodes. Characterized in that the beam spot distance on the surface was adjustable.

Incidentally, the "interval in the predetermined direction" is, when a perpendicular line is drawn from the emission center of each laser diode in a straight line along the predetermined direction, an intersection occurs between the straight line and each perpendicular line. Means interval. Further, the meaning of “the distance between adjacent ones of the laser diodes in the predetermined direction is set to a value in which at least one distance is different from the other distance” means that the distance between the plurality of laser diodes in the predetermined direction is different. If the intervals are d1, d2, d3,..., Dn, d1 = d2 = d3 = ...
= Dn is not satisfied.

2) Operation According to the multi-beam laser scanning device of the present invention having the above-described configuration, the intervals between the spots formed by converging the laser beam emitted from each laser diode on the surface of the photoconductor are not the same. Therefore, it is possible to select spots at intervals according to the scanning pitch on the surface of the photoreceptor and perform writing on the surface of the photoreceptor. Therefore, by preparing various values for the intervals between the spots, it is possible to cope with various scanning pitches on the surface of the photoconductor.

3) Example Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1A shows a first embodiment of a multi-beam laser scanning device according to the present invention.
FIG. 1B is a perspective view of the multi-beam laser diode array 1 according to the embodiment, and FIG. 1B is a diagram illustrating four beams emitted from the multi-beam laser diode array 1 according to the first embodiment and converged on the photosensitive member surface 3 by the scanning optical system 2. Laser beams L1, L2, L3, L
FIG. 4 is a diagram showing four spots a, b, c, and d.

In FIG. 1, a multi-beam laser diode array 1 includes four laser diodes LD1, LD2, LD3 and LD4.
It has. These four laser diodes LD1, LD2,
Each interval of LD3 and LD4 is d1, d2, as shown in FIG.
d2. These four laser diodes LD1, LD2, LD3
And laser beams L1, L2, L3 and L4 emitted from LD4
Respectively form spots a, b, c and d on the photoreceptor surface 3 through the scanning optical system 2 as shown in FIG. 1B.

Next, two of L1, L2 in the laser beams L1, L2, L3, L4.
A case in which writing is performed on the photoconductor surface 3 using a book will be described. In this case, as shown in FIG. 1C, writing is performed on the photosensitive member surface 3 with the number of interlaced scanning lines = 3 by the spots a and b. Now, assuming that the moving speed of the photosensitive member surface 3 in the sub-scanning direction Y is v (mm / sec) and the scanning cycle is t (sec), the position a1 of the spot a in the first scan and the position a1 in the second scan (Distance) h from position a2
Becomes h = vt.

Here, the distance r1 between the spots a and b (this distance r1
Is r1 = d1 where the lateral magnification of the scanning optical system 2 is m.
× m) is determined as in the following equation.

However, it is possible to set m as an integer of 1 or more,
In the case of FIG. 1C, m = 2. In this case, r1 = 3h / 2.

In this case, as can be seen from FIG. 1C, the scanning pitch p
Becomes p = h / 2.

Here, for example, if h = 63.5 μm, the scanning pitch p becomes: p = (0.0635 / 2) mm = 25.4 / (0.0635 / 2) spi = 800 spi (spot per inch).

Next, L2, L3, L4 in the laser beams L1, L2, L3, L4
A case in which writing is performed on the photoreceptor surface 3 using these three lines will be described. In this case, as shown in FIG. 1D, the number of interlaced scanning lines is 4 due to the spots b, c, and d.
It is assumed that writing is performed on the photoconductor surface 3. Now, the moving speed of the photosensitive member surface 3 in the sub-scanning direction Y is set to v (mm / sec) as in the case of FIG. 1C, and the scanning cycle is set to t (sec).
Then, the interval (distance) h between the position b1 of the spot b in the first scan and the position b2 in the second scan of the spot b becomes h = vt, as in the case of FIG. 1C.

Here, the distance r2 between the spots b and c and between c and d is determined as in the following equation.

However, it is possible to set m as an integer of 1 or more,
In the case of FIG. 1D, m = 1. In this case, r2 = 4h / 3.

In this case, as can be seen from FIG. 1D, the scanning pitch p
Becomes p = h / 3.

Here, as in the case of FIG. 1C, if h = 63.5 μm, the scanning pitch p becomes p = (0.0635 / 3) mm = 25.4 / (0.0635 / 3) spi = 1200 spi.

The above description with reference to FIG. 1D is for the case where writing is performed continuously during the entire scan by the three spots b, c, and d. However, either the odd-numbered scan or the even-numbered scan is performed. If writing is performed only during scanning and writing is not performed during other scanning, the scanning pitch p becomes p = 600 spi.

In addition, in the case of FIG. 1D, when writing the same one scan line of data continuously during the odd-numbered and even-numbered scans, by writing 1200 spi,
It can write 600spi apparently.

Further, in the case of FIG. 1D, writing of image data is performed in the n-th scan, writing is not performed in the (n + 1) th, n + 2, n + 3rd scans, and writing of the next image data is performed in the (n + 4) th scan. Then, if the next image data is written every fourth scanning, the scanning pitch p becomes p = 300 spi.

In addition, by writing image data of the same line during the fourth consecutive scan, writing of 300 spi can be performed by writing of 1200 spi.

2A and 2B are explanatory views of a second embodiment of the multi-beam laser diode array according to the present invention. FIG. 2A is a diagram showing five laser diodes of the multi-beam laser diode array 1.
FIG. 4 is a diagram showing a relationship between LD1 to LD5 and spots a, b, c, d, and e formed by converging laser beams L1 to L5 emitted therefrom through a scanning optical system 2 and converging on a photoreceptor surface 3; It is. As shown in FIG. 2A, the intervals d1 to d4 between adjacent ones of the laser diodes LD1 to LD5 are set as follows.

d2 = 0.8d1, d3 = 0.7d1, d4 = 0.5d1, each of the spots a by the laser beams L1 to L2 emitted from the laser diodes LD1 to LD5 arranged as described above.
The distances r1 to r4 between to e are determined by the lateral magnification m of the scanning optical system as described above.

FIG. 2B shows two of the spots a to e in FIG. 2A.
An example of a combination of the two selected spots when writing to the photoreceptor surface 3 by selecting the two spots;
The relationship between the distance between the two laser diodes corresponding to the two spots and the moving speed of the photosensitive member surface 3 when writing is performed at the same scanning pitch p by the selected two spots is shown. I have.

As can be seen from FIG. 2B, writing is performed at the same scanning pitch p for various laser scanning devices having different moving speeds of the photoreceptor surface 3 by selecting a driving laser diode in the multi-beam laser diode array. It can be performed. That is, the same multi-beam laser diode array can be used for various types of semiconductor laser scanning devices having different printing speeds.

FIG. 3 is an explanatory view of a third embodiment of the multi-beam laser diode array according to the present invention, in which four laser diodes LD1 to LD4 of the multi-beam laser diode array 1 and laser beams L1 to L4 emitted therefrom are scanned. The spots a, b, and converged on the photoreceptor surface 3 after passing through the optical system 2.
It is a figure showing the relation with c and d. As shown in FIG. 3, the distance between adjacent laser diodes LD1 to LD4
d1 to d3 are set as follows.

d1 = d−Δd, d2 = d, d3 = d + Δd, In this multi-beam laser diode array 1, the distance between adjacent laser diodes is set so as to correspond to the variation of the scanning optical system of the semiconductor laser scanning device to be used. The design center value d is increased or decreased by a small amount. The multi-beam laser diode array 1 uses the laser diodes LD2 and LD3 when the scanning optical system has the designed lateral magnification, and uses the laser diodes LD1 and LD2 when the lateral magnification is larger than the designed value. When the lateral magnification is small, the use of the laser diodes LD3 and LD4 can cope with variations in the scanning optical system.

As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above embodiments, and various small design changes can be made without departing from the present invention described in the claims. It is possible to do.

For example, the number of laser diodes in the laser array 1 of the semiconductor laser scanning device can be various numbers other than those illustrated. Also, the interval between the laser diodes can be set arbitrarily.

C. Effects of the Invention According to the multi-beam laser scanning device of the present invention having the above-described configuration, the intervals between the spots formed by converging the laser beam emitted from each laser diode on the photoreceptor surface are not the same. Absent. Therefore, it is possible to select spots at intervals according to the scanning pitch on the surface of the photoreceptor and perform writing on the surface of the photoreceptor. Accordingly, by preparing various values for the intervals between the spots, that is, the intervals between the laser diodes, it is possible to cope with various scanning pitches on the surface of the photosensitive member.

[Brief description of the drawings]

FIG. 1A is a perspective view of a multi-beam laser diode array according to a first embodiment of the present invention, and FIG. 1B is a light beam emitted from the multi-beam laser diode array of the first embodiment, which is converged on a photosensitive member surface by a scanning optical system. Four laser beams L
FIG. 1C shows spots a, b, c, and d of 1, L2, L3, and L4, and FIG. 1C is an explanatory diagram when writing is performed on the surface of the photosensitive member by the spots a and b shown in FIG. 1B, and FIG. 1D. FIG. 1B is an explanatory view when writing is performed on the surface of the photoconductor by the spots b, c, and d shown in FIG. 1B. FIG. FIG. 5 is a diagram showing spots of five laser beams converged on the surface,
FIG. 2B shows two selected spots from the five spots shown in FIG. 2A.
FIG. 3 is a view showing an example of a combination of three spots. FIG. 3 is a view showing spots of four laser beams emitted from the multi-beam laser diode array of the third embodiment and converged on the surface of the photoconductor by a scanning optical system. 4A to 8 are explanatory diagrams of the prior art, FIGS. 4A and 4B are explanatory diagrams of a scanning optical system used in a multi-beam laser scanning device, and FIG. 5 is used in the multi-beam laser scanning device. FIG. 6 is an explanatory diagram of a multi-beam laser diode array, FIG. 6 is an explanatory diagram in the case of scanning with two laser beams and the number of interlaced scans is 1, and FIG. FIG. 8 is an explanatory diagram of interlaced scanning when the number of laser beams is two and the number of interlaced scans is three. L1, L2, L3, ... Laser beam, LD1, LD2, LD3, ... Laser diode, 1 ... Multi-beam laser diode array

Claims (2)

(57) [Claims] 1. A multi-beam laser scanning device which scans a photosensitive member surface linearly and emits a plurality of laser beams separated by a predetermined distance in a direction perpendicular to the scanning direction, wherein each of the LD driving devices is independently modulated. Three or more laser diodes (LD1, LD1,
In the multi-beam laser scanning device having LD2, LD3,..., At least one interval between adjacent ones of the laser diodes (LD1, LD2, LD3,. The number of laser beams that is set to a value and is larger than the number of laser beams that actually perform writing scanning on the surface of the photoconductor is provided. By selecting a predetermined laser diode from among the laser diodes, the A multi-beam laser scanning device wherein a beam spot interval on a body surface is adjustable. 2. The method according to claim 1, wherein each of said three or more laser diodes (LD1, LD1,
LD2, LD3,...) Are formed on the same substrate of one laser array.