JP2004017382A - Optical write head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical write head which can improve the rigidity without bringing about a light axis variation when a lens supporting member for supporting a rod lens array, and a substrate base for loading a substrate with an LED light emitting element array mounted are fixed, and can print with a high quality. <P>SOLUTION: The substrate base 15 for loading the substrate 13 with the LED light emitting element array 16 mounted has pins 18 projecting at a side face by considered spacing in a head longitudinal direction. The lens supporting member 12 for supporting the rod lens array 11 has holes 19 for pins 18 to penetrate. The substrate base 15 and the lens supporting member 12 are positioned so that an emission point of the light emitting element is located at the center of a light axis of the lens, and then fixed by inserting pins 18 into holes 19 and injecting an adhesive to the periphery of the pins 18. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical writing head mounted on an electrophotographic image recording apparatus, which collects light emitted from a light emitting element array by a lens array and projects the light on a photosensitive member.
[0002]
[Prior art]
In an electrophotographic image recording apparatus, a latent image is formed by exposing a photosensitive drum, the latent image is developed with toner, the toner is transferred to paper, and printing is performed by fixing the toner to paper by heat or the like. It is carried out.
[0003]
FIG. 1 is a diagram for explaining a process of image recording in an electrophotographic system. Around the photosensitive drum 31, a charger 34, an optical writing head 30, a developing unit 35, a transfer belt 36, an eraser 32, and a cleaning roll 33 are arranged. Electrophotographic image recording includes a charging process in which a charging potential is previously applied to the surface of the photosensitive drum 31 by a charger 34 using a means such as corona discharge, and an LED disposed linearly on the substrate of the optical writing head 30. An exposure process of irradiating the light emitted from the light emitting element to the photosensitive drum 31 through an erecting equal-magnification rod lens to attenuate the potential of the irradiated portion to form a latent image, and a developing unit 35 includes: A developing process of attaching the charged toner to the latent image portion of the photosensitive drum 31 by electrostatic attraction, and a transfer process of transferring the toner attached to the photosensitive drum 31 to paper or the like carried by the transfer belt 36. A fixing process for fixing the toner transferred to the paper or the like by heat or the like, an erasing process for erasing the charge on the surface of the photosensitive drum 31 by the eraser 32, A cleaning process for removing toner adhered to the surface of the drum 31 by the cleaning roll 33.
[0004]
There are two types of exposure processes, one using LED light and the other using laser light. However, an image recording apparatus using an optical writing head of an LED optical system using an LED as a light source can be made smaller than one using laser light. It has the advantage of being widely used.
[0005]
FIG. 2 is a perspective view of a longitudinal end portion of an LED optical system optical writing head mounted on a conventional electrophotographic image recording apparatus. The optical writing head shown in FIG. 2 includes a lens support member 42 on which an erecting equal-magnification rod lens array 41 is mounted, and a substrate table 45 on which a substrate 43 is mounted. A plurality of LED light emitting element arrays 46 are mounted on the substrate 43 linearly in the longitudinal direction of the head, and the LED light emitting element arrays 46 are arranged such that the light emitting points of the LEDs are positioned at the optical axis center of the rod lens. Have been. The lens support member 42 and the board base 45 are fixed by bolts via brackets 47.
[0006]
FIG. 3 is a front view of a conventional optical writing head. Although the optical writing head shown in FIG. 2 shows only one end point, as shown in FIG. 3, the lens supporting member 42 and the board base 45 are similarly bolted via a bracket 47 at the other end. The support is fixed.
[0007]
[Problems to be solved by the invention]
In the writing head of the LED optical system, the light emitting energy from the LED light emitting element array is exposed to the photosensitive drum through the erecting equal-magnification rod lens array. However, since the rod lens array is apt to cause unevenness in the periodic light quantity of the resolution and the rod lens pitch, after finely adjusting the optical axis center of the rod lens and the light emitting point position of the LED, the lens support member holding the rod lens array is A method of fixing a substrate mounting a substrate on which an LED light emitting element array is mounted is adopted.
[0008]
As a method for fixing the lens support member and the substrate base, as shown in FIG. 3, a method in which both ends are fixed with bolts or the like via a bracket can be considered. In this method, the tightening torque of the bolt affects and the adjustment is performed. In this case, the optical axis is displaced, and the image quality deteriorates remarkably due to the occurrence of unevenness in the amount of light.
[0009]
As shown in FIG. 1, a number of members such as a charger, a developing unit, a transfer belt, an eraser, and a cleaning roll are arranged around the photosensitive drum on which the optical writing head is mounted. In order to avoid interference, it is necessary to reduce the width of the optical writing head, and a thin design is adopted for the lens support member and the substrate base. Therefore, at both ends in the longitudinal direction of the head, a method of fixing the lens support member and the board base with bolts via brackets and a method of fixing the bracket portions at both ends with solder are adopted. However, when the lens support member and the substrate table are fixed only at both ends, the natural frequency is reduced, which causes vibration and the like. Furthermore, if the intensity near the center of the head cannot be maintained and an external force is applied near the center of the head, the position of the LED light source and the optical axis of the rod lens change, and the image quality deteriorates significantly due to uneven light quantity. Would.
[0010]
The present invention has been made in view of such conventional problems, and an object thereof is to fix a lens support member for supporting a rod lens and a board base on which a board on which an LED light emitting element array is mounted is mounted. In this case, the optical axis of the rod lens and the LED element does not change, the rigidity of the head is improved, the optical axis does not easily change due to aging and external force, and an optical writing head capable of printing with high image quality is provided. Is to do.
[0011]
[Means for Solving the Problems]
In the optical writing head of the present invention, the substrate table has a pin protruding from the side surface on the lens supporting member side at a predetermined interval in the longitudinal direction of the head, and the lens supporting member has a hole for penetrating the pin. The board base and the lens support member are positioned so that the light emitting point of the light emitting element is located at the center of the optical axis of the lens, and are fixed by the adhesive injected around the pins inserted into the holes. Features.
[0012]
Further, in the optical writing head of the present invention, the lens support member includes a pin protruding from the side surface on the substrate table side at a predetermined interval in the longitudinal direction of the head, and the substrate table includes a hole for penetrating the pin. The substrate mount and the lens supporting member are positioned so that the light emitting point of the light emitting element is located at the center of the optical axis of the lens, and are fixed by the adhesive injected around the pin inserted into the hole. It is characterized by.
[0013]
Further, in the optical writing head of the present invention, the substrate base is provided with a plurality of protruding pins on a side surface on the lens support member side at a predetermined interval in the longitudinal direction of the head and in a direction orthogonal to the longitudinal direction of the head. The support member has a hole for penetrating a plurality of pins, and the substrate mount and the lens support member are positioned so that the light emitting point of the light emitting element is located at the optical axis center of the lens, and is inserted into the hole. The pin is fixed by an adhesive injected around the pin.
[0014]
Further, in the optical writing head of the present invention, the lens support member includes a plurality of protruding pins in a direction orthogonal to the head longitudinal direction, on a side surface on the substrate stage side at a predetermined interval in the head longitudinal direction, The base is provided with a hole for penetrating a plurality of the pins, and the substrate base and the lens support member are positioned so that the light emitting point of the light emitting element is located at the optical axis center of the lens, and inserted into the hole. The pin is fixed by an adhesive injected around the pin.
[0015]
The adhesive is preferably a UV-curable adhesive, the lens array is preferably a rod lens array or a resin erecting equal-magnification lens array, and the light emitting element array is a self-scanning light emitting element array Is preferred.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 4 is an exploded perspective view of a lens support member and a substrate stand that constitute the optical writing head of the present invention.
[0018]
A substrate 13 is mounted on the substrate stand 15, and a plurality of LED light emitting element arrays 16 are mounted on the substrate 13 linearly in the longitudinal direction of the head. In addition, pins 18 projecting at predetermined intervals in the longitudinal direction are provided on the side surface of the substrate table 15 on the lens support member 12 side. The cross-sectional shape of the pin 18 may be round or polygonal. The board base 15 has an action of releasing heat generated by the LED light emitting element array 16 mounted on the board 13.
[0019]
The lens support member 12 supports a rod lens array 11 in which rod lenses of erect equal magnification are arranged in a row. The lens support member 12 is provided with a hole 19 through which a pin 18 protruding from the substrate base 15 penetrates. The hole 19 is larger in size than the pin 18, and is provided at a position facing the pin 18 provided on the board base 15 at the time of assembly.
[0020]
The pin 18 is inserted into the hole 19, and the optical axis of the rod lens and the light emitting point is adjusted so that the LED light emitting element is positioned at the optical axis center of the rod lens. Since the rod lens has such a characteristic that the light amount unevenness in the lens arrangement cycle increases as the rod lens deviates from the optical axis center, it is necessary to finely adjust the light emitting point of the LED light emitting element to be located at the optical axis center of the rod lens. .
[0021]
After adjusting the optical axis of the rod lens and the light emitting point, an adhesive 17 is injected from the lens support member 12 side into the gap between the inserted pin 18 and the hole 19 of the lens support member 12, and the lens support member 12 and the substrate The position between the tables 15 is fixed.
[0022]
Next, a method of adjusting the optical axis of the rod lens and the light emitting point will be described.
[0023]
When the light emitting point of the LED light emitting element is moved from the optical axis center of the rod lens, the light amount cycle unevenness of the lens pitch in the longitudinal direction of the lens increases as the amount of movement increases. However, when halftone printing is performed, printing unevenness occurs due to light amount cycle unevenness, thereby deteriorating image quality.
[0024]
Therefore, while observing the spatial imaging profile and the light amount of the light emitting point of the LED light emitting element by means such as a CCD camera so that the light emitting point of the LED light emitting element is located at the optical axis position of the rod lens, the light amount unevenness is minimized. Next, the lens position or the light emitting point position is adjusted.
[0025]
FIG. 5 is a perspective view showing a state in which a substrate stand and a lens support member are attached to the optical axis adjusting and assembling machine.
[0026]
The optical axis adjusting and assembling machine includes a support 21, a substrate mount fixing bar 22 mounted on the support 21, a stage 23 movable on the support 21, and a CCD camera mounted on the stage 23. 24, and a support member fixing stay 25 held on a stage (not shown).
[0027]
The stage 23 can be finely moved in the Y direction in FIG. 5 on the support base 21 by operating an actuator. The support member fixing stay 25 can be finely moved in the X direction and the Z direction (the direction perpendicular to the surface of the support base 21) in FIG.
[0028]
The lens support member 12 supporting the rod lens array 11 is attached to a support member fixing stay 25. The board base 15 on which the board 13 on which the LED light emitting element array 16 is mounted is mounted on the board base fixing bar 22.
[0029]
The optical axis adjustment is performed using the opposed CCD camera 24. The positioning adjustment between the light emitting element and the lens is performed in the following procedure.
1. The parallelism between the stage 23 on which the CCD camera 24 is mounted and the LED light emitting element array 16 is adjusted.
2. The CCD camera 24 is focused on the light emitting element surface.
3. After retracting the CCD camera 24 by L0 + Z (L0: working distance (distance between the rod lens and the light emitting element), Z: lens thickness), the actuator of the support member fixing stay 25 is operated in the X direction, Adjustment is made so that the exit surface of the lens is focused on the CCD camera 24.
4. After the light emitting elements emit light, the stage 23 of the CCD camera 24 is operated in the Y direction to acquire spatial imaging data of the light emitting point sequence.
5. By shifting the support member fixing stay 25 up and down by 50 μm in the Z direction (perpendicular to the surface of the support table 21), the height of the lens support member 12 from the support table 21 is shifted by 50 μm each. Acquire spatial imaging data.
6. The lens support member 12 is moved to a position where the fluctuation of the light amount cycle unevenness is small in the data acquired in units of 50 μm from the support base 21 of the lens support member 12.
[0030]
After that, the lens support member and the substrate stand are fixed. That is, an adhesive 17 is injected into the gap between the inserted pin 18 and the hole 19 of the lens support member 12 from the lens support member 12 side to fix the position between the lens support member 12 and the substrate base 15. It is preferable to use a UV-curable adhesive since the process speed can be improved.
[0031]
FIG. 6 is a front view showing the optical writing head of the present invention after assembly, and a cross-sectional view in a direction perpendicular to the longitudinal direction at a central portion in the longitudinal direction of the head. In FIG. 6, the lens support member 12 side and the substrate stand 15 are fixed by injecting an adhesive 17 around the pins 18 from the lens support member 12 side at both ends and the center in the head longitudinal direction.
[0032]
Conventionally, the method of fixing the lens support member and the substrate base is by bolting through a bracket, so that when the bolt is rotated and tightened, stress is generated, and the optical axis adjusting and assembling machine is used. Even when the optical axis is adjusted by the method, when the lens support member and the substrate stand are fixed and taken out from the optical axis adjusting and assembling machine, the optical axis sometimes changes.
[0033]
As a countermeasure, there is a method of fixing the brackets on both ends with solder, or fixing the space between the substrate base and the lens support member with a hardening filler. However, there is a problem that the fixing strength between the two cannot be maintained.
[0034]
According to the fixing method of the present invention, the lens supporting member and the fixing means for the substrate stand do not have a structure for inducing a positional deviation such as a bolt, so that a positional deviation does not occur in a fixing step between the two. In addition, since a plurality of pins for fixing the two can be arranged in the longitudinal direction of the head, the natural frequency can be improved, and the strength can be increased without increasing the thickness of the head.
[0035]
FIG. 7 is a front view showing a modified example of the optical writing head of the present invention, and a cross-sectional view in a direction perpendicular to the longitudinal direction at a central portion in the longitudinal direction of the head. The optical writing head shown in FIG. 7 has the same configuration as the optical writing head shown in FIG. 6, except that a plurality of pins are arranged in the height direction of the substrate stand. Although a plurality of pins are arranged in the length direction of the substrate table, a plurality of pins may be arranged in the height direction of the substrate table.
[0036]
In the above-described embodiment, the pins for fixing the space between the lens support member and the substrate table are provided on the substrate table side. However, pins protruding toward the lens support member are provided, and the pins penetrate to the corresponding positions on the substrate table side. Holes may be provided, and they may be adhered and fixed from the substrate stage side.
[0037]
Further, if the fixing strength of the lens support member and the substrate base is fixed by only the adhesive, if the fixing strength is insufficient, the lens support member and the substrate stand may be further fastened by bolts after the adhesive is completely cured.
[0038]
Further, a self-scanning light emitting element array can be used as the LED light emitting element array. Note that the self-scanning light-emitting element array chip is a light-emitting element array chip having a built-in self-scanning circuit and having a function of sequentially transmitting light-emitting points.
[0039]
The self-scanning light emitting element array chip is mounted as a light source for a printer head according to Japanese Patent Application Laid-Open Nos. 1-238962, 2-14584, 2-92650, 2-92651, and the like. It is described that the above-described configuration is simple, the interval between the light emitting elements can be reduced, and that a compact printer head can be manufactured. Also, Japanese Patent Application Laid-Open No. Hei 2-263668 proposes a self-scanning light emitting element array chip having a structure in which a transfer element array is used as a shift section and is separated from a light emitting element array as a light emitting section.
[0040]
FIG. 8 shows an equivalent circuit diagram of a self-scanning light emitting element array chip having a structure in which a shift section and a light emitting section are separated. The shift section has transfer elements T ₁ , T ₂ , T ₃ ,..., And the light emitting section has write light emitting elements L ₁ , L ₂ , L ₃ ,. These transfer element and light emitting element are constituted by a three-terminal light emitting thyristor. The configuration of the shift unit uses diodes D ₁ , D ₂ , D ₃ ,... To electrically connect the gates of the transfer elements to each other. V _GK is a power supply (normally 5 V), and is connected to the gate electrodes G ₁ , G ₂ , G ₃ ,... Of each transfer element via a load resistance _RL . Further, the gate electrodes G ₁ , G ₂ , G ₃ ,... Of the transfer elements are also connected to the gate electrodes of the light emitting elements for writing. A start pulse φ _S is applied to the gate electrode of the transfer element T ₁ , transfer clock pulses φ 1 and φ 2 are alternately applied to the anode electrode of the transfer element, and a write signal is applied to the anode electrode of the write light emitting element. φ _I have been added.
[0041]
In the _{figure, R1, R2, R S,} R I denotes respectively current limiting resistor.
[0042]
The operation will be briefly described. First voltage of the transfer clock pulses φ1 is at H level, the transfer element T ₂ is turned on. At this time, the potential of the gate electrode _{G 2} is lowered to almost zero V from 5V to _{V GK.} The effect of this potential drop is transmitted by the diode D ₂ to the gate electrode G _3, it is set to the potential of about 1V (forward threshold voltage of the diode D ₂ (equal to the diffusion potential)). However, the connection of the potential of the gate electrode G ₁ for the diode D ₁ is reverse biased state is not performed, the potential of the gate electrode G ₁ remains at 5V. ON voltage of the light-emitting thyristor, since is approximated by a diffusion potential of the gate electrode potential + pn junction (approximately 1V), H-level voltage of the next transfer clock pulse φ2 it is necessary to turn on about 2V (transfer element T ₃ voltage) or more and and about 4V (only the transfer element T ₃ by setting the voltage) or less necessary to turn on the transfer element T ₅ is turned on such, other transfer devices are to remain off be able to. Therefore, the ON state is transferred by two transfer clock pulses.
[0043]
Start pulse phi _S is a pulse for starting such a transfer operation, and the start pulse phi _S H level (about 0V) to simultaneously transfer clock pulse .phi.2 H level (about 2 to about 4V) , to turn on the transfer element _{T 1.} Shortly thereafter, a start pulse φ _S is returned to the H level.
[0044]
Now, the transfer element T ₂ is When in the ON state, the potential of the gate electrode G ₂ is, becomes substantially 0V. Accordingly, the voltage of the write signal phi _I is, if the diffusion potential (about 1V) or more pn junctions, can be a light-emitting element L ₂ and the light-emitting state.
[0045]
In contrast, the gate electrode _{wherein G 1} is about 5V, the gate electrode _{G 3} are approximately 1V. Accordingly, the write voltage of the light-emitting element _{L 1} is about 6V, the write voltage of the light-emitting element _{L 3} is about 2V. Now, the voltage of the write signal phi _I to put writing only to the light-emitting element _{L 2} is in the range of 1 to 2 V. When the light-emitting element L ₂ is turned on, i.e., enters the emission state, the light emission intensity is decided to the amount of current flowing to the write signal phi _I, it is possible to image writing at any intensity. Further, in order to transfer the light-emitting state to the next light emitting element is dropped to 0V the voltage of the write signal phi _I line once, it is necessary to once turn off the light-emitting element that emits light.
[0046]
Further, in the above-described embodiment, an erecting equal-magnification rod lens array is used as imaging means for condensing light emitted from the LED light emitting element array to form an image on the photosensitive drum. The invention is not limited to the lens array, and for example, a resin erecting equal-magnification lens array may be used. FIG. 9 is a perspective view showing an example of a configuration of a resin erecting equal-magnification lens array. The resin erecting equal-magnification lens array is formed by stacking two or more lens array plates 27 each having a single-eye lens 28 arranged in one or two rows, and can form an erecting equal-magnification image. The monocular lens 28 has the same focal length and aperture, and is convex on one side or convex on both sides.
[0047]
【The invention's effect】
As described above, the optical writing head of the present invention does not have a structure in which the fixing means of the lens support member and the substrate stand are displaced by a bolt or the like. Does not occur.
[0048]
Further, in the optical writing head of the present invention, since a plurality of pins for fixing between the lens supporting member and the substrate stand are arranged in the longitudinal direction of the head, the natural frequency and rigidity are improved.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a process of image recording in an electrophotographic system.
FIG. 2 is a perspective view at a longitudinal end of an LED optical system optical writing head mounted on a conventional electrophotographic image recording apparatus.
FIG. 3 is a front view of a conventional optical writing head.
FIG. 4 is an exploded perspective view of a lens support member and a substrate stand that constitute the optical writing head of the present invention.
FIG. 5 is a perspective view showing a state where a substrate table and a lens support member are attached to the optical axis adjusting and assembling machine.
FIG. 6 is a front view showing the optical writing head of the present invention after assembling, and a cross-sectional view in a direction perpendicular to the longitudinal direction at a central portion in the longitudinal direction of the head.
FIG. 7 is a front view showing a modified example of the optical writing head of the present invention, and a cross-sectional view in a direction perpendicular to the longitudinal direction at a central portion in the longitudinal direction of the head.
FIG. 8 is an equivalent circuit diagram of a self-scanning light-emitting element array.
FIG. 9 is a perspective view showing an example of the configuration of a resin erecting equal-magnification lens array.
[Explanation of symbols]
11, 41 Rod lens array 12, 42 Lens support member 13, 43 Substrate 15, 45 Substrate base 16, 46 LED light emitting element array 17 Adhesive 18 Pin 19 Hole 21 Support base 22 Substrate mount bar 23 Stage 24 CCD camera 25 Support Member fixing stay 27 Lens array plate 28 Monocular lens 30 Optical writing head 31 Photosensitive drum 32 Eraser 33 Cleaning roll 34 Charger 35 Developing unit 36 Transfer belt 47 Bracket

Claims (7)

A substrate base on which a substrate on which the light emitting element array is mounted is mounted, and a lens support member for supporting a lens array in which lenses are arranged in a row is provided, and light emitted from the light emitting element array is collected by the lens array. In an optical writing head that projects onto a photoconductor,
The substrate mount has a pin protruding from a side surface on the lens support member side at a predetermined interval over the longitudinal direction of the head,
The lens support member includes a hole for penetrating the pin,
The substrate mount and the lens support member are positioned such that a light emitting point of a light emitting element is positioned at the center of the optical axis of the lens, and fixed by an adhesive injected around the pin inserted into the hole. An optical writing head, comprising: A substrate base on which a substrate on which the light emitting element array is mounted is mounted, and a lens support member for supporting a lens array in which lenses are arranged in a row is provided, and light emitted from the light emitting element array is collected by the lens array. In an optical writing head that projects onto a photoconductor,
The lens support member has a pin protruding from the side surface on the substrate stage side at a predetermined interval over the longitudinal direction of the head,
The board base includes a hole for penetrating the pin,
The substrate mount and the lens support member are positioned such that a light emitting point of a light emitting element is positioned at the center of the optical axis of the lens, and fixed by an adhesive injected around the pin inserted into the hole. An optical writing head, comprising: A substrate base on which a substrate on which the light emitting element array is mounted is mounted, and a lens support member for supporting a lens array in which lenses are arranged in a row is provided, and light emitted from the light emitting element array is collected by the lens array. In an optical writing head that projects onto a photoconductor,
The substrate mount is provided with a plurality of protruding pins in a direction orthogonal to the head longitudinal direction, on a side surface on the lens support member side at a predetermined interval over the head longitudinal direction,
The lens support member includes a hole for penetrating a plurality of the pins,
The substrate mount and the lens support member are positioned such that a light emitting point of a light emitting element is positioned at the center of the optical axis of the lens, and fixed by an adhesive injected around the pin inserted into the hole. An optical writing head, comprising: A substrate base on which a substrate on which the light emitting element array is mounted is mounted, and a lens support member for supporting a lens array in which lenses are arranged in a row is provided, and light emitted from the light emitting element array is collected by the lens array. In an optical writing head that projects onto a photoconductor,
The lens support member has a plurality of protruding pins in a direction perpendicular to the head longitudinal direction, on a side surface on the substrate stage side at a predetermined interval in the head longitudinal direction,
The board base includes holes for penetrating a plurality of the pins,
The substrate mount and the lens support member are positioned such that a light emitting point of a light emitting element is positioned at the center of the optical axis of the lens, and fixed by an adhesive injected around the pin inserted into the hole. An optical writing head, comprising: The optical writing head according to claim 1, wherein the adhesive is a UV-curable adhesive. The optical writing head according to claim 1, wherein the lens array is a rod lens array or a resin erecting equal-magnification lens array. 7. The optical writing head according to claim 1, wherein the light emitting element array is a self-scanning light emitting element array.

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