JP2001071561A - Laser array imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small laser array imaging apparatus in which the quantity of light can be corrected with high accuracy. SOLUTION: A plurality of laser beams 3 emitted from each laser element 2a of a semiconductor laser array 2 are partially reflected on a half mirror 5 positioned between the second lens 41 and the stop 42 of a focus optical system 4 and the remainder transmits the half mirror 5. Each laser beam 3 reflected on the half mirror 5 is directed toward a quantity of light detector 7 located at a position on the optical axis equivalent to the stop 42 with respect to the half mirror 5 and the quantity of light is detected. A quantity of light correcting circuit 11 outputs a signal for correcting the quantity of light of the laser element 2a based on the detection results of the quantity of light detector 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser array image forming apparatus such as a printer and a copying machine, and more particularly, to a laser array image forming apparatus which is small in size and capable of correcting light quantity with high accuracy.

[0002]

2. Description of the Related Art An example of a conventional image forming apparatus using a laser beam is disclosed in Japanese Patent Application Laid-Open No. H11-58828.

FIG. 5 shows the conventional image forming apparatus.
The image forming apparatus 100 includes a laser array 101 having a plurality of laser elements 101a arranged in an array,
An imaging optical system 103 composed of an enlargement optical system for imaging a plurality of laser beams 102 emitted from each laser element 101a on a photosensitive drum 105, and a point 103a where a principal ray of the laser beam 102 intersects the photosensitive drum 105 The half mirror 1 is arranged on the optical path of the laser beam 102 between the first and second mirrors.
04 and the laser beam 1 reflected by the half mirror 104
And a light detecting element 107 disposed at a converging point of the condensing lens 106 and detecting the light amount of the laser beam 102.
And an amplifier 10 for amplifying a detection signal of the light detection element 107.
8 and the laser array 10 based on the output of the amplifier 108.
Correction circuit 1 for correcting the output of each laser element 101a
09.

According to such an image forming apparatus 100,
Even if the output of the laser element 101a varies, the light quantity of the laser beam 102 can be corrected for each laser element 101a based on the detection of the light quantity, so that the light quantity on the photosensitive drum 105 can be made uniform and high image quality can be obtained. An image can be formed.

[0005]

However, according to the conventional image forming apparatus, the laser beam 102 is applied to the photosensitive drum 1.
After the respective laser beams 102 are divided by the half mirror 104 during the enlarging and projecting onto the laser beam 05, the laser beams 102 are condensed by the condensing lens 106 so that the principal rays of the laser beams 102 coincide on the photodetector 107. Therefore, it is necessary to use a large condensing lens having a large condensing action, which causes a problem that the apparatus becomes large.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a laser array image forming apparatus which is small and capable of correcting light quantity with high accuracy.

[0007]

According to the present invention, in order to achieve the above object, a plurality of laser elements arranged on a laser array emit a plurality of laser beams modulated in accordance with an image signal. In the laser array image forming apparatus for forming an image by forming an image of the laser beam on a photoreceptor, the plurality of laser beams emitted from the plurality of laser elements are irradiated with a principal ray of the plurality of laser beams. An imaging lens system that condenses light so as to intersect at the center of an aperture disposed outside the body side and forms an image on the photoreceptor; and an imaging lens system that is disposed between the imaging lens system and the aperture. An optical system for dividing the plurality of laser beams transmitted through the lens system into an image for forming an image on the photoreceptor, and a light amount detecting unit; and a light dividing unit for the light amount detecting unit. A laser array image forming apparatus, comprising: a light detecting means for detecting the plurality of laser beams; and a control means for controlling driving conditions of the plurality of laser elements based on a detection result of the light detecting means. I will provide a.

According to the above arrangement, by disposing the splitting optical means between the imaging lens system and the stop, the plurality of laser beams split for detecting the amount of light by the splitting optical means have their chief rays converged. Act like so. Therefore, even if an optical element such as a condenser lens for matching the principal rays of the plurality of laser beams is not used, the plurality of laser beams split for light amount detection by the split optical unit can be It becomes possible to detect.

[0009]

DETAILED DESCRIPTION OF THE INVENTION FIGS. 1 (a), 1 (b) and 1 (c)
1 shows a laser array image forming apparatus according to a first embodiment of the present invention. FIG. 3A is a YZ plane view, and FIG.
FIG. 3C is an XZ plane view, and FIG. 3C is a view as viewed from the photosensitive drum side in FIG. 3A and 3B, X indicates the sub-scanning direction, Y indicates the main scanning direction, and Z indicates the optical axis direction. The apparatus 1 mainly forms a single-color image, has a plurality of laser elements 2a two-dimensionally arranged in a sub-scanning direction X and a main scanning direction Y, and outputs an image signal from each laser element 2a. Semiconductor laser array 2 capable of simultaneously and independently emitting a plurality of laser beams 3 modulated in accordance with the above, a photosensitive drum 6 rotated in a direction indicated by an arrow in FIG. An imaging optical system 4 including a first lens 40, a second lens 41, and an aperture 42 for projecting a plurality of laser beams 3 emitted in parallel from the respective laser elements 2a onto the photosensitive drum 6 to form an image; A half mirror 5 disposed on the optical path of the laser beam 3 between the second lens 41 and the diaphragm 42 and transmitting a part of the laser beam 3 transmitted through the second lens 41 and reflecting the rest; And it includes a light amount detector 7 for detecting the amount of laser beam 3 reflected by the Fumira 5.

The first lens 40 and the second lens 41 are
In order to reduce aberrations, the object side (laser array 2 side) is formed of a telecentric optical system, which is composed of anamorphic aspheric lenses formed in different aspheric shapes in the sub-scanning direction X and the main scanning direction Y. ing. The diaphragm 42 is arranged at a point 4a where the principal rays of each laser beam 3 intersect, sets the brightness (F number) to a predetermined value, and removes scattered rays and the like.

As shown in FIGS. 1B and 1C, the light quantity detector 7 includes a condenser lens 70 for condensing the laser beam 3 reflected by the half mirror 5, and an aperture 42 for the half mirror 5. The condenser lens 7 is disposed at a position on the optical axis equivalent to
A light receiving element 71 that receives the laser beam 3 condensed by 0 and outputs a detection signal corresponding to the light amount. The condenser lens 70 has a positive power composed of a spherical surface having a center of a radius of curvature at the center of the light receiving surface of the light receiving element 71. Therefore, the laser beam 3 reflected by the half mirror 5 is applied to the center of the light receiving element 71 while being condensed by the condenser lens 70.

As shown in FIG. 1B, the apparatus 1 includes a drum driving circuit 10 that drives the photosensitive drum 6 to rotate and outputs a timing signal synchronized with the rotation of the photosensitive drum 6. A light amount correction circuit 11 for obtaining a difference between a detection signal from the light receiving element 71 of the light amount detector 7 and a reference value and outputting a correction signal corresponding to the difference to the control circuit 15
An image memory 12 storing an image signal; a signal processing circuit 13 for reading out the image signal from the image memory 12 and processing the image signal to output a recording signal according to a recording pattern; A laser drive circuit 14 for inputting a recording signal and outputting a drive signal for driving the semiconductor laser array 2; a control signal output to the laser drive circuit 14 in synchronization with a timing signal from the drum drive circuit 10; A control circuit 15 for outputting a correction signal from the circuit 11 to the laser drive circuit 14.

The laser drive circuit 14 controls each laser element 2 based on a control signal and a correction signal from the control circuit 15.
A drive signal is output in which the value of the applied current to each laser element 2a or the pulse width of the applied current is corrected so that the light amount of the laser beam 3 from a becomes uniform on the photosensitive drum 6.

Although this device 1 is not shown,
Image forming means such as a charging device, a developing device, and a transfer device are provided around the photoreceptor drum 6, and a paper feed unit for supplying recording paper to the transfer device is provided in a stage preceding the transfer device, and a sheet feeding unit is provided in a stage subsequent to the transfer device. And a fixing unit for fixing the toner image transferred to the recording paper, and a paper discharge unit for discharging the recording paper on which the toner image is fixed.

FIG. 2 shows the semiconductor laser array 2. In the semiconductor laser array 2, a plurality of laser elements 2a are two-dimensionally arranged in a sub-scanning direction X and a main scanning direction Y according to a certain rule.

Next, the operation of the apparatus 1 will be described. (1) Correction mode

The laser drive circuit 14 outputs a drive signal to the semiconductor laser array 2 under the control of the control circuit 15, and sequentially drives each laser element 2a one by one. Each laser element 2a emits light sequentially and emits the laser beam 3 substantially parallel to the optical axis direction Z. The laser beam 3 emitted from each laser element 2a passes through the first lens 40 and the second lens 41 of the imaging optical system 4, is partially reflected by the half mirror 5, and the rest is transmitted. The laser beam 3 transmitted through the half mirror 5 is enlarged by the lateral magnification of the imaging optical system 4 and projected on the photosensitive drum 6 to form an image. At this time, the principal rays of each laser beam 3 intersect at the center point 4a of the stop 42.

On the other hand, the laser beam 3 reflected by the half mirror 5 is condensed by the condensing lens 70, and then enters the light receiving surface of the light receiving element 71 at substantially the same position. The light receiving element 71 outputs a detection signal corresponding to the received light amount to the light amount correction circuit 11. The light amount correction circuit 11 calculates a difference between the detected value and the reference value, and outputs a correction signal corresponding to the difference to the control circuit 15. The control circuit 15 includes the light amount correction circuit 11
Is stored in a memory (not shown) for each laser element 2a. Thus, the correction mode is executed. (2) Image forming mode

The signal processing circuit 13 reads an image signal from the image memory 12, processes the image signal, and outputs a recording signal corresponding to a recording pattern to the laser driving circuit 14. The drum drive circuit 10 drives the photosensitive drum 6 to rotate at a constant rotation speed, and outputs a timing signal synchronized with the rotation of the photosensitive drum 6 to the control circuit 15.
The control circuit 15 outputs a control signal to the laser drive circuit 14 in synchronization with the timing signal from the drum drive circuit 10, and outputs a correction signal stored in the memory to the laser drive circuit 14 in the correction mode. The laser drive circuit 14 inputs the recording signal from the signal processing circuit 13 based on the control signal and the correction signal from the control circuit 15, and outputs a drive signal corrected based on the correction signal to the semiconductor laser array 2. The semiconductor laser array 2 emits a laser beam 3 from each laser element 2 a, and the emitted laser beam 3 is enlarged and projected on a photosensitive drum 6 by an imaging optical system 4, so that the main scanning direction Y Are formed in one row, and a two-dimensional electrostatic latent image is sequentially formed by rotating the photosensitive drum 6. Thereafter, the electrostatic latent image on the photosensitive drum 6 is developed with toner by a developing device, and the toner image is transferred to recording paper fed from a paper feeding unit by a transfer device and further fixed by a fixing device. Thereafter, the paper is discharged to the paper discharge unit. Thus, a high-quality image is formed on the recording paper.

According to the above-described first embodiment, the following effects can be obtained. (A) Since the light receiving element 71 of the light amount detector 7 is disposed at a position on the optical axis equivalent to the stop 42 with respect to the half mirror 5, a large light condensing beam for matching the principal ray of the laser beam 3 is used. Since an optical element such as a lens becomes unnecessary, the size of the apparatus can be reduced. (B) Since the amount of light is detected by the common light receiving element 71 for each laser element 2a, there is no variation in the light amount detection value due to the characteristics between the light receiving elements as compared with the case where a plurality of light receiving elements are used. Thus, highly accurate light quantity correction can be performed. (C) A hemispherical condenser lens 7 on the light receiving surface of the light receiving element 71
0, the laser beam 3 reflected by the half mirror 5 and incident on the condenser lens 70 is condensed at the center of the light receiving surface on the light receiving element 71 under the same refraction regardless of the incident direction. Since the light is irradiated while being irradiated, the light receiving area of the light receiving element 71 can be reduced, and the size of the device can be further reduced. (D) Since the half mirror 5 can be a flat mirror, the half mirror 5 can be easily manufactured.

FIGS. 3A, 3B and 3C show a laser array image forming apparatus according to a second embodiment of the present invention. FIG. 3A is a YZ plane view, FIG. 3B is an XZ plane view, and FIG. 3C is a view from the photosensitive drum side in FIG. 3A and 3B, X indicates the sub-scanning direction, Y indicates the main scanning direction, and Z indicates the optical axis direction. The apparatus 1 forms a color image, and includes a plurality of laser beams 3 modulated according to image signals of Sian (C), yellow (Y), magenta (M), and black (K). (3c, 3y, 3m, 3k), and a plurality of photoconductor drums 6C, 6Y, 6C, 6Y, which are provided corresponding to the respective colors of C, Y, M, and K and rotate in the direction of the arrow in FIG. 6M, 6K and laser array 2
A plurality of laser beams 3c, 3y,
3m and 3k corresponding to the photosensitive drums 6C, 6Y, 6M,
An imaging optical system 4 similar to that of the first embodiment for forming an image on a surface of 6K and forming an electrostatic latent image on the surface,
And a half mirror 5 and a light amount detector 7 configured in the same manner as in the embodiment.

FIG. 4 shows a semiconductor laser array 2 according to the second embodiment. The semiconductor laser array 2 includes a laser beam 3 modulated according to an image signal of Sian (C).
c, a laser element group 2Y emitting a plurality of laser beams 3y modulated according to a yellow (Y) image signal, and a laser element group 2Y modulated according to a magenta (M) image signal. It has a laser element group 2M that emits a plurality of laser beams 3m and a laser element group 2K that emits a plurality of laser beams 3k modulated according to a black (K) image signal. 2M, 2Y, 2C
Are arranged in parallel in the main scanning direction Y, and each laser element group 2
Each of the laser elements 2a constituting K, 2M, 2Y, and 2C is
According to a certain rule in the main scanning direction Y and the sub-scanning direction X, 2
They are arranged in a dimension.

According to the second embodiment described above, the first
Similarly to the embodiment, the light receiving element 71 of the light quantity detector 7
Are arranged on a position on the optical axis equivalent to the stop 42 with respect to the half mirror 5, so that the laser beams 3c, 3y,
Since an optical element such as a large condenser lens for matching the principal rays of 3 m and 3 k is not required, the size of the apparatus can be reduced. Further, since the amount of light is detected by the common light receiving element 71 for each of the laser elements 2a constituting each of the laser element groups 2K, 2M, 2Y, 2C, the amount of light is compared with the case where a plurality of light receiving elements are used. Since there is no variation in the detected value due to characteristics between the light receiving elements, highly accurate light amount correction can be performed. Further, since the hemispherical condenser lens 70 is provided on the light receiving surface of the light receiving element 71, the laser beams 33c, 3y, which are reflected by the half mirror 5 and enter the condenser lens 70, are provided.
3m and 3k receive the same refraction effect regardless of the incident direction and are irradiated while being condensed at the center of the light receiving surface on the light receiving element 71. Therefore, the light receiving area of the light receiving element 71 can be reduced, and the device can be downsized Can be further improved.

[0024]

Next, an image forming optical system 4 according to an example corresponding to the first and second embodiments of the present invention will be described. Assuming that the horizontal coordinate with the optical axis as the origin is X and the vertical coordinate is Y, the sag amount z (x, y) of the plane parallel to the Z axis is expressed by the following equation. The amount of zag is (sagittal
Height) is an abbreviation for the height of the surface from the tangent plane.

(Equation 1) Table 1 shows lens data of the imaging optical system 4 according to the example of the present invention.

[Table 1] In the table, the # column indicates the surface number, # 0 indicates the emission surface of the semiconductor laser array 2, and # 1 to # 2 indicate the first surface.
The lens 40 is shown, # 3 to # 4 show the second lens 41, # 5 shows the stop 42, and # 6 shows the surface of the photosensitive drum 6, that is, the image plane. The column of the radius of curvature r indicates the radius of curvature of each surface. The column of the thickness or the surface distance d is
The distance from each surface to the next surface is shown. The column of “refractive index” indicates the refractive index of the material forming the first lens 40 and the second lens 41.

In Table 1, aspherical surfaces are indicated by *,
The values of the coefficients defined by the above equations and in the equations for each surface are shown in Table 2 below.

[Table 2] In the imaging optical system 4 having the lens data shown in Table 2, the wavelength λ, the focal length f, the total angle of view 2θ, the execution FNo,
Magnification M is: λ = 775 nm, f = 70.000 mm, 2θ = 52 de
g, FNo = 16, and M = 6.

The present invention is not limited to the above embodiments and examples, but can be variously modified. For example, in the above embodiment, the condenser lens is used for the light amount detector. However, the condenser element is not provided, and the light receiving element 71 is arranged at a position on the optical axis equivalent to the diaphragm 42 with respect to the half mirror 5. You may. As a result, the number of parts can be reduced,
The configuration can be simplified. Further, in the above embodiment, the photoconductor is arranged on the side that has passed through the half mirror,
The light amount detector was placed on the side reflected by the half mirror,
Conversely, the light amount detector may be arranged on the side that has passed through the half mirror, and the photoconductor may be arranged on the side that has been reflected by the half mirror. Further, the configuration using the photoconductor drum as the image carrier has been described. For example, a belt photoconductor, a drum-shaped or a belt-shaped dielectric may be used. Also,
The invention can also be applied to an image forming apparatus having an intermediate transfer member.

[0027]

As described above, according to the laser array image forming apparatus of the present invention, a plurality of lasers divided for detecting the amount of light by the dividing optical means disposed between the imaging lens system and the stop are provided. Since the light amount of the beam is detected, the light amount of the plurality of laser beams can be detected without using an optical element such as a condenser lens for matching the principal rays of the plurality of laser beams. Becomes possible. Further, since the amount of light is detected by a common light detecting means for each laser element, the light amount detected value does not vary due to the characteristics between the light detecting means as compared with the case where a plurality of light detecting means are used. Thus, highly accurate light quantity correction can be performed.

[Brief description of the drawings]

FIGS. 1A and 1B show a laser array image forming apparatus according to a first embodiment of the present invention, in which FIG.
(B) is a configuration diagram on the XZ plane, and (c) is a diagram of the light amount detector viewed from the photosensitive drum side in (b).

FIG. 2 is a perspective view of the semiconductor laser array according to the first embodiment;

3A and 3B relate to a laser array image forming apparatus according to a second embodiment of the present invention, wherein FIG.
(B) is a configuration diagram on the XZ plane, and (c) is a diagram of the light amount detector viewed from the photosensitive drum side in (b).

FIG. 4 is a perspective view of a semiconductor laser array according to a second embodiment.

FIG. 5 is a perspective view showing a conventional image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser array image forming apparatus 2 semiconductor laser array 2a laser element 2K, 2M, 2Y, 2C laser element group 3, 3c, 3y, 3m, 3k laser beam 4 imaging optical system 4a point 5 half mirror 6, 6C, 6Y, 6M, 6K Photoconductor drum 7 Light amount detector 10 Drum drive circuit 11 Light amount correction circuit 12 Image memory 13 Signal processing circuit 14 Laser drive circuit 15 Control circuit 40 First lens 41 Second lens 70 Condensing lens 71 Light receiving element X Sub-scan Direction Y Main scanning direction Z Optical axis direction

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C362 AA16 AA53 AA54 BA51 BA60 BA85 CA39 DA08 2H076 AB05 AB06 AB08 AB18 AB34 AB41 AB55 CA18 DA04 DA17 EA01

Claims (8)

[Claims] An image is formed by emitting a plurality of laser beams modulated in accordance with an image signal from a plurality of laser elements arranged on a laser array, and forming an image on the photosensitive member with the plurality of laser beams. In the laser array image forming apparatus, the plurality of laser beams emitted from the plurality of laser elements are collected so that the principal rays of the plurality of laser beams intersect at the center of an aperture arranged outside the photoconductor. An imaging lens system that emits light to form an image on the photoconductor; and an optical system that is disposed between the imaging lens system and the diaphragm and transmits the plurality of laser beams transmitted through the imaging lens system onto the photoconductor. An image forming unit that forms an image, and a division optical unit that divides the light into a light amount, and a light detection unit that detects the plurality of laser beams divided for the light amount detection by the division optical unit. Control means for controlling driving conditions of the plurality of laser elements based on a detection result of the light detection means. 2. The laser array image forming apparatus according to claim 1, wherein said light detecting means is arranged at a position optically equivalent to the center of said stop with respect to said division optical means. 3. The apparatus according to claim 1, wherein said splitting optical means is a half mirror for transmitting and reflecting said plurality of laser beams transmitted through said imaging lens system and splitting said laser beams for image formation and light amount detection. Item 2. A laser array image forming apparatus according to Item 1. 4. A light-receiving element for receiving the plurality of laser beams and outputting a detection signal, and a light-receiving element for receiving the plurality of laser beams from the splitting optical means on a light-receiving surface of the light-receiving element. 2. The laser array image forming apparatus according to claim 1, further comprising an optical element having a positive power for converging light on the light receiving surface. 5. The laser array image forming apparatus according to claim 4, wherein the surface of the optical element on the side of the divided optical means is formed as a spherical surface having a center of a radius of curvature on the light receiving surface of the light receiving element. 6. The laser array image forming apparatus according to claim 1, wherein said imaging lens system includes a lens having an aspherical shape for reducing aberration. 7. The laser array image forming apparatus according to claim 6, wherein said lens has a different aspherical shape in the main scanning direction and the sub-scanning direction. 8. A plurality of laser elements arranged on a laser array corresponding to a plurality of color materials emit a plurality of laser beams modulated according to image signals corresponding to the color materials,
A laser array image forming apparatus that forms a color image composed of the plurality of color materials by imaging the plurality of laser beams on a plurality of photoconductors provided corresponding to the plurality of color materials; The plurality of laser beams emitted from the plurality of laser elements corresponding to the color materials are collected such that the principal rays of the plurality of laser beams intersect at the center of a stop arranged outside the plurality of photoconductors. An imaging lens system that emits light and forms an image on the plurality of photoconductors; and the plurality of laser beams that are disposed between the imaging lens system and the diaphragm and pass through the imaging lens system. Division optical means for dividing into an image formation for forming an image on the photosensitive member and light quantity detection; and a light detection means for detecting the plurality of laser beams divided for the light quantity detection by the division optical means. When the detection result laser array image forming apparatus characterized by comprising a control means for controlling the driving condition of said plurality of laser elements on the basis of the light detecting means.