JP2007185918A - Light source apparatus, optical scanner, and image-forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source apparatus which is substantially insensitive to environmental temperature and humidity and can obtain a stable optical spot on a surface to be scanned using a liquid microlens, an optical scanner capable of obtaining stable, high-definition images using the light source apparatus, and an image-forming apparatus using the scanner. <P>SOLUTION: In a light source apparatus comprising a coupling lens 10 which couples divergent optical beams radiated from a light-emitting section 9, a liquid microlens 21 is arranged between the light-emitting section 9 and the coupling lens 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light source device having a coupling lens for coupling a divergent light beam emitted from a light emitting unit, an optical scanning device including the same, and an image forming apparatus using the optical scanning device.

Optical scanning devices are widely known in connection with image forming apparatuses such as optical printers, digital copying machines, and optical plotters (see, for example, Patent Document 1).
In an image forming apparatus using such an optical scanning device, a demand for obtaining a high-definition image is increasing year by year. In order to obtain a high-definition image, the light spot on the surface to be scanned has the following conditions: (1) the beam waist position of the light beam matches the surface to be scanned; (2) the light spot It is important to satisfy that the position in the main scanning / sub-scanning direction is as intended.
In particular, the condition (2) is extremely important because it relates to the presence or absence of color misregistration when the image forming apparatus is developed into a color image. Of course, these conditions are given within a certain range, and various processing errors and mounting tolerances of the optical element are determined from the range. In that case, it is the relative arrangement position accuracy of the light emitting part and the coupling lens that imposes a particularly strict tolerance.
This is because the coupling lens functions as the optical element having the strongest power among the optical elements that constitute the optical scanning device, and therefore has high sensitivity, so that the coupled lens and the light emitting unit are scanned against the relative positional deviation. The influence on the light spot on the surface is extremely large.

For example, assuming that the combined focal length in the main scanning direction of the optical element disposed after the optical deflector is 150 mm and the focal length of the coupling lens is 15 mm, the lateral magnification in the main scanning direction is about 10 times and the vertical magnification is about 100 times.
Therefore, when the relative arrangement position of the light emitting portion and the coupling lens is shifted by 1 μm in the Y direction, the position of the light spot on the surface to be scanned in the main scanning direction is shifted by 10 μm with respect to the target position. Similarly, when the relative arrangement position is shifted by 1 μm in the optical axis direction, the beam waist position on the scanned surface is shifted by 100 μm from the scanned surface.
This phenomenon is also the same in the sub-scanning direction. In particular, when the so-called “enlargement system” in which the lateral magnification of the optical element disposed after the optical deflector is greater than 1, the optical performance is significantly deteriorated.
It is very difficult to place components with an accuracy of 1 μm in normal machine accuracy, and even if it can be achieved, the capital investment for that and the time required for placement become enormous, resulting in an expensive image forming apparatus. . Therefore, conventionally, a method as disclosed in Patent Document 1 is employed to achieve the relative arrangement accuracy of the light emitting unit and the coupling lens.
JP 2001-166244 A

In the method disclosed in Patent Document 1, the light emitting part is press-fitted and fixed to a holder, the relative arrangement position of the coupling lens is adjusted, and then the adhesive is fixed by UV curing resin.
However, since this method uses a UV curable resin, it changes constantly under the influence of ambient temperature and humidity even after being bonded and fixed, so that the light spot on the surface to be scanned is stably the above condition (1). It is difficult to construct a light source device that satisfies the conditions (2).
Accordingly, an object of the present invention is to provide a light source device that uses a liquid microlens, is less susceptible to the influence of ambient temperature and humidity, and obtains a stable light spot on the surface to be scanned, and is stable using this light source device. It is an object of the present invention to provide an optical scanning device capable of obtaining a desired high-definition image and an image forming apparatus using the same.

In order to solve the above-described problem, the invention according to claim 1 is a light source device including a coupling lens for coupling a divergent light beam emitted from a light emitting unit, the light emitting unit and the coupling lens. It features a light source device in which a liquid microlens is disposed between the two.
In the invention according to claim 2, the liquid microlens defines an axis perpendicular to the optical axis direction of the coupling lens as a Y axis and an axis perpendicular to the optical axis direction and the Y axis direction as a Z axis. Then, the light source device according to claim 1, wherein the direction of the light beam emitted from the coupling lens can be adjusted independently in the Y direction and the Z direction by electrical control.

In the invention according to claim 3, the liquid microlens can independently adjust the degree of divergence of the light beam emitted from the coupling lens in the Y direction and the Z direction by electrical control. A light source device according to claim 1 or 2 is characterized.
The invention according to claim 4 is characterized in that the liquid microlens also serves as a cover glass having a dustproof function with respect to the light emitting portion. And

According to a fifth aspect of the present invention, at least one light beam emitted from the light source device is imaged as a long line image in the main scanning direction in the vicinity of the deflection reflection surface of the optical deflector by the line image imaging optical system. In the optical scanning device that scans the scanned surface by deflecting the deflected beam at an equal angular velocity by the optical deflector, condensing the deflected beam as a light spot on the scanned surface, and as the light source device, Item 5. An optical scanning device using the light source device according to any one of Items 1 to 4.
According to a sixth aspect of the present invention, the photosensitive image carrier is optically scanned by the optical scanning unit to form a latent image, and the latent image is visualized by the developing unit to obtain an image. An image forming apparatus having at least one section is characterized by an image forming apparatus using the optical scanning device according to claim 5 as optical scanning means for optically scanning the image carrier.

  According to the present invention, it is possible to provide a light source device that is hardly affected by ambient temperature and humidity and that can stably maintain the state of the light beam.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an optical arrangement of an embodiment of an optical scanning device according to the present invention. In the optical scanning device D of FIG. 1, the light beam from the light source device 1 passes through an aperture 3, an anamorphic optical element 4, a polygon mirror 5 of a rotating polygon mirror as an optical deflector, and a scanning surface 8 via a scanning optical system 6. To reach.
FIG. 1 also shows a soundproof glass G1 that closes a window of a soundproof housing (not shown) that houses the polygon mirror 5, and a dustproof glass that is provided at the exit portion of the deflected light beam of the housing that houses the optical system of FIG. G2 is shown.
The light beam emitted from the light source device 1 is shaped by the aperture 3 and enters the anamorphic optical element 4. The light beam transmitted through the anamorphic optical element 4 passes through the soundproof glass G1 while being focused in the sub-scanning direction, and is formed as a “long line image in the main scanning direction” in the vicinity of the deflection reflection surface of the polygon mirror 5 to be deflected and reflected. When reflected by the surface, the light passes through the soundproof glass G 1 and enters the scanning optical system 6.

The scanning optical system 6 is composed of two lenses 6 a and 6 b, and the light beam transmitted through these lenses 6 a and 6 b is incident on the scanned surface 8 through the dust-proof glass G 2 and is scanned by the action of the scanning optical system 6. A light spot is formed on the surface 8.
When the polygon mirror 5 rotates at a constant speed, the light beam reflected by the deflecting reflecting surface is deflected at a constant angular velocity. The scanning optical system 6 causes the light spot by the incident light beam while being deflected at a constant angular velocity to move on the surface to be scanned 8 at a constant speed in the main scanning direction (vertical direction in the figure). It has characteristics. The light spot optically scans the scanned surface 8 at a constant speed.
The scanning optical system 6 is also an anamorphic optical element, and in the sub-scanning direction, the deflection reflection surface position of the polygon mirror 5 and the scanned surface position are in a geometric optical conjugate relationship, thereby correcting the surface tilt of the polygon mirror. is doing. The scanned surface 8 is essentially a “photosensitive surface of a photosensitive medium (image carrier)”.

As described above, the light source device 1 of the present invention includes a light emitting unit 9 (see FIG. 3) that emits a light beam and a coupling lens 10 (FIG. 2) that couples a divergent light beam emitted from the light emitting unit. Reference).
That is, this is a light source device in which a liquid microlens 21 (see FIG. 4) is disposed between the light emitting unit 9 and the coupling lens 10. In the light source device 1, the liquid microlens 21 can adjust the direction of the light beam emitted from the coupling lens 10 independently with respect to the Y axis and the Z axis by electrical control using a control unit (not shown). be able to.
In this case, an axis orthogonal to the optical axis direction of the coupling lens 10 is defined as a Y axis, and an axis orthogonal to the optical axis direction and the Y axis direction is defined as a Z axis. Accordingly, it is possible to provide the light source device 1 that can stably maintain the divergent / parallel / converged state of the light beam.

FIG. 2 is a schematic perspective view showing a semiconductor laser constituting the light source device. FIG. 3 is a schematic perspective view showing a coupling lens constituting the light source device. 2 and 3 are perspective views of the front side and the back side of the holder 11, respectively.
In the light source device 1, the semiconductor laser 9 as a light emitting unit has a configuration as shown in FIG. 3, and a divergent light beam emitted from the semiconductor laser 9 is desired for a subsequent optical system. It comprises a coupling lens 10 for converting into a light beam shape, and a liquid microlens (see FIG. 4) disposed between the semiconductor laser 9 and the coupling lens 10.
More specifically, the semiconductor laser 9 is press-fitted and fixed to a resin holder 11. The coupling lens 10 is pressed and fixed to support portions 11a and 11b provided on the holder 11 by springs 12a and 12b.

Conventionally, when the semiconductor laser 9 and the coupling lens 10 are fixed to the holder 11, the relative arrangement positions of the semiconductor laser 9 and the coupling lens 10 are adjusted. For example, the relative position of the semiconductor laser 9 that is press-fitted and fixed is adjusted. After that, the coupling lens 10 was fixed to the holder 11 using an adhesive.
However, the fixing method using the adhesive is affected by the ambient temperature and humidity even after the adhesive fixing, and the relative arrangement position constantly changes. Therefore, the light beam emitted from the coupling lens 10 is deviated from a desired direction, and the imaging position is also shifted in the optical axis direction.
However, when the semiconductor laser 9 and the coupling lens 10 are held by press-fitting or pressing against the holder 11 as in the present embodiment, it becomes difficult to be affected by the ambient temperature and humidity, and at least the relative arrangement position is stable. To do.
Even in this case, it is very difficult to adjust the direction of the light beam emitted from the coupling lens 10. Therefore, the adjustment is performed by a liquid microlens installed between the semiconductor laser 9 and the coupling lens 10. This liquid microlens is preferably configured to also serve as a cover glass in consideration of the dustproof function of the semiconductor laser 9.

FIG. 4 is a schematic diagram showing the configuration of the liquid microlens. FIG. 5 is a top view showing an electrode structure of the liquid microlens of FIG. FIG. 6 is a schematic diagram for explaining the movement of a droplet. Here, the liquid microlens will be described.
The liquid microlens is a lens (shown in FIG. 4) as disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-50303. The configuration and operation of the liquid microlens will be described with reference to FIGS.
The liquid microlens 21 includes a transparent insulating layer 14, a droplet 13 made of a transparent fluid disposed on the surface thereof, and a plurality of electrodes 17, 18, 19, insulated from the droplet 13 by the insulating layer 14. 20, and further, a transparent substrate 15 that supports the insulating layer 14 and the electrodes 17, 18, 19, 20.
Further, in FIG. 5, which is a top view showing a configuration of a plurality of electrodes, each electrode 17, 18, 19, 20 (voltage V 1 to V 4) and a droplet electrode 16 (voltage V 0) connected to the droplet 13 are The liquid microlens 21 is operated by the voltage difference between these V0 to V4.

Next, the operation will be described. The contact angle θ1 formed by the droplet 13 and the insulating layer 14 is determined from the mutual interfacial tension between the droplet 13, the insulating layer 14 and air. When there is no voltage difference between the droplet 13 and the electrodes 17, 18, 19, 20 (V 0 = V 1 = V 2 = V 3 = V 4), the droplet 13 has a volume (Vol) of the droplet 13. And the shape defined by the contact angle θ1 (indicated by the solid line) is maintained, and the curvature radius R1 of the droplet 13 is determined. Further, the droplet 13 exists in the center with respect to the electrodes 17, 18, 19, and 20 (the position indicated by the solid line in FIG. 5).
Next, when a voltage V equal to the four electrodes 17, 18, 19, 20 is applied to the droplet 13 (that is, V 0 ≠ V 1 = V 2 = V 3 = V 4), the droplet 13 is indicated by a dotted line. The droplet 13a changes to a shape defined by the contact angle θ2 shown, and the contact angle decreases from θ1 to θ2.
In this case, since the volume (Vol) of the droplets 13 and 13a is not changed, the curvature radius R2 of the droplet 13a is determined from the relationship with the shape defined by the contact angle θ2. At this time, the contact angle reversibly changes with respect to the voltage V, that is, the radius of curvature can also be determined reversibly. At this time, the droplet 13a remains in the center with respect to the electrode (the position of the dotted line in FIG. 5).
As described above, the liquid microlens 21 can adjust the radius of curvature R by applying the voltage V to the electrodes 17, 18, 19, and 20 with respect to the droplet 13, that is, the focal length can be adjusted.

Next, an operation for moving the position of the droplet 13 will be described. By selectively applying a voltage to the four electrodes 17, 18, 19, and 20, the position of the droplet 13 can be changed.
For example, by making the voltage V1 of the electrode 17 and the voltage V3 of the electrode 19 equal to V0 and making the voltage V2 of the electrode 18 greater than the voltage V4 of the electrode 20, the droplet 13 is drawn in the direction of higher voltage, It moves in the direction of the arrow shown in FIG.
As described above, the liquid microlens 21 can adjust the lens position, that is, the focal position by selectively applying a voltage to the electrodes 17, 18, 19, and 20. Needless to say, this is one configuration example of the liquid microlens 21 and is not limited thereto.

Returning to FIGS. 2 and 3, according to the operation principle of the liquid microlens 21, there is a relative dislocation shift when the semiconductor laser 9 and the coupling lens 10 are fixed to the holder 11. However, all of this can be absorbed by the liquid microlens 21 and corrected.
Although the liquid microlens 21 (see FIG. 4) can provide the same effect even if it is disposed after the coupling lens 10, in this case, it is greatly influenced by the aberration of the liquid microlens 21. For example, there is a possibility that the light spot on the surface to be scanned cannot be narrowed.
In order to reduce this, it is preferable for the light source device to dispose the liquid microlens 21 in front of the coupling lens 10 so that the liquid microlens 21 does not exhibit much influence even if it has aberration. It is a form.
The semiconductor laser 9 may be a so-called semiconductor laser array having a plurality of light emitting portions. In this way, the rotational speed of the optical deflector required to achieve the same writing density can be reduced, and high density / high speed writing can be performed with low power. Further, it is possible to provide an optical scanning device that is less affected by ambient temperature and humidity and that can obtain a stable light spot on the surface to be scanned.

FIG. 7 is a schematic view showing an embodiment of an image forming apparatus to which the present invention is applied. This image forming apparatus C is shown as a tandem full-color optical printer. On the lower side of the apparatus, a conveyance belt 32 that conveys transfer paper (not shown) fed from a paper feed cassette 22 arranged in the horizontal direction is provided.
Above the transport belt 32, a yellow Y photoconductor 36Y, a magenta M photoconductor 36M, a cyan C photoconductor 36C, and a black K photoconductor 36K are arranged in order from the upstream side at equal intervals. Has been. In the following, yellow, magenta, cyan, and black are distinguished by Y, M, C, and K in the code.
The photoreceptors 36Y, 36M, 36C, and 36K are all formed to have the same diameter, and process members are sequentially disposed around the photoreceptors according to the electrophotographic process. Taking the photoconductor 36Y as an example, a charging charger 33Y, an optical scanning device 34Y, a developing device 35Y, a transfer charger 31Y, a cleaning device 37Y, and the like are sequentially arranged. The same applies to the other photoconductors 36M, 36C, and 36K.
That is, this image forming apparatus uses the photoconductors 36Y, 36M, 36C, and 36K as scanning surfaces set for respective colors (corresponding to reference numeral 8 in FIG. 1), and optical scanning is performed for each. The devices 34Y, 34M, 34C, and 34K are provided in a one-to-one correspondence relationship.

Around the conveyor belt 32, a registration roller 23 and a belt charging charger 24 are provided on the upstream side of the photosensitive member 36Y, and a belt separation charger 25 and a charge removing charger are provided on the downstream side of the photosensitive member 36K. 26, a cleaning device 27, and the like are provided. A fixing device 28 is provided downstream of the belt separation charger 25 in the transport direction, and is connected to a paper discharge tray 29 by a paper discharge roller 28.
In such a configuration, for example, in the full color mode, each of the optical scanning devices 34Y, 34M, 34M, 36M, 36C, and 36K is based on the image signals of Y, M, C, and K colors. An electrostatic latent image is formed by optical scanning with 34C and 34K.
These electrostatic latent images are developed with corresponding color toners to form toner images, which are superposed by being sequentially transferred onto transfer paper that is electrostatically adsorbed onto the conveyance belt 32 and conveyed. After being fixed as a full-color image, it is discharged onto a discharge tray 29.

  By using the optical scanning device described in the embodiment for such an image forming apparatus, it is possible to obtain a stable light spot diameter on the surface to be scanned, which is hardly affected by the ambient temperature and humidity. An image forming apparatus suitable for fine printing can be realized in a compact and inexpensive manner.

It is the schematic which shows the optical arrangement | positioning of embodiment of the optical scanning device by this invention. It is a schematic perspective view which shows the semiconductor laser which comprises a light source device. It is a schematic perspective view which shows the coupling lens which comprises a light source device. It is the schematic which shows the structure of a liquid microlens. It is a top view which shows the electrode structure of the liquid microlens of FIG. It is the schematic explaining the movement of a droplet. 1 is a schematic diagram showing an embodiment of an image forming apparatus to which the present invention is applied.

Explanation of symbols

C Image forming device D Optical scanning device 1 Light source device 4 Line image imaging optical system (anamorphic optical element)
5 Line image imaging optical system (polygon mirror of rotating polygon mirror which is an optical deflector)
6 Scanning optical system (lenses 6a, 6b)
8 Scanned surface 9 Light emitting part (semiconductor laser)
10 Coupling lens 21 Liquid microlens 34Y Optical scanning means (optical scanning device)
35Y developing means (developing device)
36Y Image carrier (photoreceptor)

Claims (6)

  In a light source device including a light emitting unit and a coupling lens for coupling a divergent light beam emitted from the light emitting unit, a liquid microlens is disposed between the light emitting unit and the coupling lens. A light source device characterized by the above.   The liquid microlens defines a light beam emitted from the coupling lens when an axis orthogonal to the optical axis direction of the coupling lens is defined as a Y axis and an axis orthogonal to the optical axis direction and the Y axis direction is defined as a Z axis. The light source device according to claim 1, wherein the direction can be independently adjusted in the Y direction and the Z direction by electrical control.   3. The liquid microlens is capable of independently adjusting the degree of divergence of the light beam emitted from the coupling lens in the Y direction and the Z direction by electrical control. Light source device.   4. The light source device according to claim 1, wherein the liquid microlens also serves as a cover glass having a dustproof function with respect to the light emitting unit. 5.   At least one light beam emitted from the light source device is formed as a long line image in the main scanning direction in the vicinity of the deflecting reflection surface of the optical deflector by the line image imaging optical system, and deflected at a constant angular velocity by the optical deflector. 5. The light source device according to claim 1, wherein the deflected beam is condensed as a light spot on the surface to be scanned by a scanning optical system and the surface to be scanned is scanned. An optical scanning device using a light source device.   In the image forming apparatus having one or more image forming units for forming a latent image by performing optical scanning by the optical scanning unit on the photosensitive image carrier, and visualizing the latent image by the developing unit to obtain an image. An image forming apparatus using the optical scanning device according to claim 5 as optical scanning means for optically scanning an image carrier.

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