JP2001130054A - Writing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide a writing apparatus capable of writing a wide image. SOLUTION: A plurality of light emitting element rows 2a, 2b, 2c wherein a large number of light emitting elements are arrange on one straight line in the main scanning direction shown by an arrow B are provided on one substrate (provided under a package case 4). The light emitting element rows are formed so that the length in the longitudinal direction of them becomes shorter than the maximum writing width writable by this writing apparatus and light emitting element rows 2a, 2b and 2b, 2c are parallelly arranged zigzag in two rows at the changeover positions Do1, Do2 of the writing dots of the light emitting elements so that these positions coincide with each other in order to obtain the maximum writing width in the arranging direction of the light emitting elements. Self-converging rod lens arrays 3A-3C are provided corresponding to the light emitting element rows 2a, 2b, 2c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a writing apparatus using a light emitting element array, and more particularly to a writing apparatus suitable for use in an image forming apparatus such as a printer and a digital copying machine.

[0002]

2. Description of the Related Art Heretofore, light emitted from a light emitting element array unit in which a plurality of light emitting elements such as LEDs are arranged in a straight line has been irradiated onto a charged surface of a photosensitive member to be written, and a latent image is formed there. There is a writing device for writing.
When writing a wide image such as an A0 size with such a writing apparatus, a light emitting element array unit having a length of about 1 m or more, which is equal to or larger than the writing width of the image, is required.

However, when a light emitting element array unit as long as 1 m is to be manufactured at, for example, 400 dpi (dot pitch: 63.5 μm), a wide LE is required.
Expensive equipment such as a D-chip mounter and a wire bonding machine are required for exclusive use. Also, the self-focusing rod lens array (Selfoc lens array: SLA) provided corresponding to the light emitting element row generally has a higher price per unit length as the width becomes wider. there were.

[0004] In order to solve such a problem, a conventional writing apparatus includes a light emitting element array unit formed in a relatively short length such as a width of A3 size, and the light emitting element arrays are arranged side by side. In some cases, a plurality of light emitting element array units are configured as a whole by arranging a plurality of light emitting element array units in the longitudinal direction (for example, see Japanese Utility Model Application Laid-open No.
No. 16342).

[0005]

However, in the case where a plurality of light emitting element array units are arranged in the longitudinal direction to form a long light emitting element array unit, the unit of the plurality of light emitting element array units is used. The problem is the dot alignment between them. That is, 400 dp
The dot pitch at i is 63.5 μm, but usually, unless the dot pitch error is smaller than about 5 μm,
Vertical black and white streaks are likely to occur in the image.

[0006] However, if the seam portion is formed by simply connecting a plurality of light emitting element array units as in a conventional writing device, for example, the environmental temperature may change or
When the temperature inside the image forming apparatus rises due to the heat generated by the LEDs, which are the light emitting elements provided in the light emitting element array unit, the temperature of the joints between the plurality of light emitting element array units also increases. There was a problem that the inter-pitch changed due to the elongation of the material.

That is, assuming that the distance between joints of connecting members connecting a plurality of light emitting element array units is 20 mm, the material is iron having a linear expansion coefficient of 0.000012 / deg, and the temperature rise is 30 deg, the temperature calculated by simple calculation is A pitch shift of 7.2 μm will occur only by the change.

Accordingly, if the initial positioning accuracy and the like of the plurality of light emitting element array units are added to this, the dot pitch error further increases, so that the seam portion of the light emitting element array units is naturally formed thereby. This causes a dot pitch error that causes a defect in the image. In addition, there is also a problem that a dot shift occurs at the joint in the direction (sub-scanning direction) orthogonal to the array direction due to the temperature change.

[0009] The present invention has been made in view of the above problems, and without using expensive equipment such as a wide LED chip mounter and a wire bonding machine.
Also, a self-focusing rod lens array, which is generally used at a low price and is inexpensive, can be used even when an image having a width wider than the width of one light emitting element row is written. It is an object of the present invention to provide a writing device that does not cause streaks or the like.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a plurality of light emitting element rows in which light emitting elements are arranged in a straight line on a single substrate. The length is shorter than the writable maximum write width, and the plurality of light emitting element rows are arranged in parallel with each other so as to obtain the maximum write width in the direction in which the light emitting elements are arranged. The writing device is configured by providing a self-focusing rod lens array corresponding to each row.

In the writing device, the light emitted from each of the light emitting elements of the plurality of light emitting element rows is aligned in the sub-scanning direction on the writing surface of the writing object and is aligned along the main scanning direction. It is effective to arrange the light emitting elements and the self-focusing rod lens arrays so as to form an image in a straight line.

Further, the optical axis of light emitted from each of the light emitting elements and passing through the self-focusing rod lens array is:
It is preferable that each light emitting element and each self-focusing rod lens array are arranged so as to be perpendicular to the writing surface of the writing object.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing an embodiment of a writing device according to the present invention, and FIG. 2 is a photoreceptor to which a writing object is similarly formed with a cross section taken along line AA of FIG. It is sectional drawing shown with a drum.

In this writing device, as shown in FIG. 1, a plurality of light emitting element rows 2a, 2b, 2c in which a plurality of light emitting elements are arranged in a straight line in the main scanning direction indicated by an arrow B are shown in FIG. It is provided on a single substrate 5 as shown. Each of the light emitting element rows 2a, 2b, 2c has a length in the longitudinal direction shorter than the maximum writing width that can be written by this device. Then, the three light emitting element rows 2a, 2b, 2c
Are arranged in parallel in two rows in a zigzag manner with their parts partially wrapped so that the maximum writing width is obtained in the arrangement direction of the light emitting elements.

The adjacent light emitting element rows 2
The light emitting element rows 2a, 2b, and 2c are made to correspond to each other at the write dot switching positions Do1 and Do2 of the light emitting elements, and the light emitting element rows 2a, 2b, and 2c are set in FIG. Are fixed to the substrate 5 shown in FIG. The light emitting elements constituting each of the light emitting element rows 2a to 2c are, for example, a plurality of LED array chips in which a plurality of dots are integrated into one, mounted on the substrate 5.

Further, as shown in FIG. 1, the writing apparatus is provided with self-focusing rod lens arrays 3A to 3C corresponding to the respective light emitting element arrays 2a to 2c, respectively.
Two light emitting element arrays 2a to 2c and three self-focusing rod lens arrays 3A to 3C are integrally packaged in a package case 4 and a housing 6, as shown in FIG.

That is, the projecting portion 4 is
a is continuously formed at a predetermined length along the longitudinal direction of the package case 4 (front and rear directions in FIG. 2), and the protrusions 4a correspond to the light emitting element arrays 2a to 2c, respectively. The self-focusing rod lens arrays 3 </ b> A to 3 </ b> C are inserted into the formed long holes so that the distal ends thereof slightly protrude as shown in the figure, and they are fixed to the package case 4 in that state.

Further, the light emitting element arrays 2a to 2c are respectively fixed to the substrate 5 in the positional relationship shown in FIG. 1 to form a long light emitting element array substrate as a whole, as shown in FIG. The housing 6 is sandwiched between the edge of the package case 4 and the housing 6, and in this state, the housing 6 is fixed to the package case 4 by screws. Thus, the light emitting element arrays 2a to 2c and the self-focusing rod lens arrays 3A to 3C are integrally packaged by the package case 4 and the housing 6.

In this packaged writing device, the tip ends of the self-focusing rod lens arrays 3A to 3C face the surface of the photosensitive drum 1 to be written with a predetermined distance therebetween. Then, it is fixed to the apparatus main body of the image forming apparatus.

In the set state, light emitted from each of the light emitting elements of the light emitting element rows 2a and 2c and passed through the self-focusing rod lens arrays 3A and 3C is written on the surface of the photosensitive drum 1. Image at position a,
Light emitted from each light emitting element of the light emitting element array 2b and passing through the self-focusing rod lens array 3B is
The image is formed at the writing position b on the surface of.

As described above, in the writing apparatus according to the present embodiment, the image forming position of the light irradiated through the self-focusing rod lens arrays 3A and 3C on the photosensitive drum 1 (a portion in FIG. 2) Self-focusing rod lens array 3B
The position of the light irradiated through the photosensitive drum 1 on the photosensitive drum 1 (part b in FIG. 2) is shifted in the double scanning direction indicated by arrow C.

Therefore, in this writing apparatus, when writing one scanning line in the main scanning direction (the direction indicated by the arrow B in FIG. 1) on the surface of the photosensitive drum 1, the writing line is located upstream in the rotation direction of the photosensitive drum 1. The light from the light emitting element array 2b located on the side is irradiated to the writing position b, and at the timing when the writing position b reaches the position a by the rotation of the photosensitive drum 1 in the direction of arrow E, the light emitting element By irradiating the light from the columns 2a and 2c to the writing position a, even if the self-focusing rod lens arrays 3A to 3C are arranged in a zigzag manner, one scanning line can be written in the same straight line. I have to.

As described above, the writing device is arranged in a zigzag manner so that the light emitting element rows 2a and 2b and 2
Since b and 2c are directly fixed to one substrate 5, the light emitting element arrays 2a and 2b and 2b and 2c are respectively fixed to separate substrates, and the respective light emitting element arrays are fixed. Compared with the case where the substrate is fixed to the substrate by a plate-like connecting member, it is possible to suppress the fluctuation of the dot interval at the switching position of each writing dot.

The self-focusing rod lens arrays 3A to 3C for forming the light emitted from the light emitting element arrays 2a to 2c on the photosensitive drum 1 are relatively short in the direction in which the light emitting elements are arranged. Although it is inexpensive by using one configuration, they are all fixed at predetermined positions of the same package case 4, so that their positional relationship is maintained with high precision. Accordingly, the same accuracy (deviation accuracy of the imaging position) as when one long self-focusing rod lens array, which is inexpensive and very expensive, is provided, can be obtained.

FIG. 3 is a plan view similar to FIG. 1 showing an embodiment of a writing device in which a plurality of light emitting element rows are arranged stepwise, and portions corresponding to FIG. 1 are denoted by the same reference numerals. It is.
As described above, even if the light emitting element arrays 2a to 2c are arranged stepwise, the light emitting element arrays 2a and 2b are located at the write dot switching position Do1, and the light emitting element arrays 2b and 2c are located at the write dot switching position Do2. Then, the switching positions of the writing dots are made to coincide with each other and fixed to the substrate, and they are fixed to the package case 4 'and the housing 6' (corresponding to the housing 6 in FIG. 2, and the package case 4 'in FIG. 3). 1 and 2), the same effect as that of the writing device described with reference to FIGS. 1 and 2 can be obtained.

FIG. 4 is a sectional view similar to FIG. 2 showing another embodiment of the writing device according to the present invention. In FIG. 4, the same reference numerals are used to simplify the description if the functions are the same as those of the writing device shown in FIG. This writing device includes a plurality of light emitting element rows 2
Light emitted from each of the light-emitting elements a to 2c is a surface (writing surface) of the photosensitive drum 1 to be written.
The light-emitting elements and the self-focusing rod lens arrays 3A to 3C are arranged so that the positions in the sub-scanning direction coincide with each other to form an image in a straight line along the main scanning direction.

According to this writing device, the light emitting element array 2a,
Since the image forming positions of the light emitted from the light emitting elements 2b and 2c coincide in the sub-scanning direction (rotation direction of the drum) of the photosensitive drum 1, the light emission timing of each light emitting element on the light emitting element rows 2a and 2c Need not be delayed by a predetermined time with respect to the light emission timing of the light emitting elements on the light emitting element array 2b. Therefore, even when the speed of the photosensitive drum 1 fluctuates,
The writing lines of the light emitting element arrays 2a and 2c do not deviate from the writing lines of the light emitting element array 2b. Further, a delay memory for delaying the light emission timing is not required.

FIG. 5 is a sectional view similar to FIG. 2 showing another embodiment of the writing apparatus according to the present invention.
In FIG. 5 as well, the same reference numerals are used for simplifying the description as long as the functions are the same even if the writing device shown in FIG.

In this writing device, the optical axes 10a to 10c of the light emitted from the respective light emitting elements and passing through the self-focusing rod lens arrays 3A to 3C are respectively applied to the surface of the photosensitive drum 1 as the writing surface. So that each light emitting element array 2a-2c and each self-focusing rod lens array 3
A to 3C are arranged respectively. In this way, the shift of the scanning line can be reduced as compared with the writing apparatus according to the embodiment shown in FIG.

That is, in the case of the writing device described with reference to FIG. 4, light emitted from each light emitting element is applied to the surface of the photosensitive drum 1 and to a line La perpendicular to the surface as shown in FIG. Incident at an angle θ. In this case, as shown in the figure, the distance between the surface of the photosensitive drum 1 and the writing device (the distance in the left-right direction in FIG. 6) is, for example, due to the eccentricity of the peripheral surface of the photosensitive drum 1. If the position of the peripheral surface fluctuates by ± δ as shown by the broken line and the imaginary line in the figure (generated by the rotational fluctuation of the photosensitive drum), the writing position of the light in the sub-scanning direction becomes regular. The position fluctuates by δtanθ.

At this time, the image forming position of the light passing through the self-focusing rod lens arrays 3A and 3C on the photosensitive drum 1 and the light passing through the self-focusing rod lens array 3B on the photosensitive drum 1 Is the angle of incidence of the light with respect to the photoconductor drum 1 in the direction different from each other with respect to the vertical line La, the deviation of the scanning line on the photoconductor drum 1 is 2δtanθ. .

On the other hand, in the writing apparatus of FIG. 5, the optical axes 10a to 10c of the light passing through the self-focusing rod lens arrays 3A to 3C are respectively perpendicular to the surface of the photosensitive drum 1. 7, the distance between the peripheral surface of the photosensitive drum 1 and the writing device is different from that when the peripheral surface of the photosensitive drum 1 is eccentric as shown by a virtual line in FIG. Even if it changes, the image forming position d of each light passing through the self-focusing rod lens arrays 3A and 3C on the photosensitive drum 1 does not shift in the sub-scanning direction (the direction of arrow C).
Similarly, the image forming position e of the light passing through the self-focusing rod lens array 3B on the photosensitive drum 1 is set even if the peripheral surface of the photosensitive drum 1 is eccentric as shown by a virtual line in FIG. There is no shift in the sub-scanning direction (arrow C direction).

[0033]

As described above, according to the present invention, the following effects can be obtained. According to the writing device of the first aspect, extremely expensive equipment such as an LED chip mounter and a wire bonding machine required for forming a long light emitting element array unit is not required, and generally used inexpensive equipment. It can be manufactured at low cost because it can be manufactured using equipment for a light emitting element array having a small width. Since a plurality of inexpensive self-focusing rod lens arrays, which are generally used in a narrow width, are used, the writing device can be manufactured at low cost.

Further, since all of the plurality of light emitting element rows are provided on one substrate, it is possible to arrange the light emitting element rows in a very short distance between adjacent light emitting element rows and to change the environmental temperature. Even if the temperature inside the apparatus rises due to heat generation of the light emitting element or the like, the dot misalignment in both the main scanning direction and the sub scanning direction is remarkably small. Therefore, it is possible to prevent the occurrence of vertical black or white streaks due to the dot displacement.

According to the second aspect of the present invention, the light emitted from each of the light emitting elements of the plurality of light emitting element arrays is aligned in the sub-scanning direction on the writing surface of the object to be written. Therefore, the deviation of the writing line in the sub-scanning direction between the light emitting element rows due to the fluctuation of the moving speed of the writing object can be eliminated. Then, there is no need to provide a delay memory for delaying the light emission timing.

According to the writing device of the third aspect, the optical axis of the light emitted from each light emitting element and passing through the self-focusing rod lens array is perpendicular to the writing surface of the writing object. When the writing surface fluctuates in the direction of approaching / separating from the self-focusing rod lens array when the writing target moves, causing a change in the distance between the writing surface and the self-focusing rod lens array. However, it is possible to prevent the writing line shift between the light emitting element rows in the sub-scanning direction.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a writing device according to the present invention.

FIG. 2 is a cross-sectional view showing a state in which the writing device is formed in a cross section along line AA in FIG. 1 together with a photosensitive drum as a writing target.

FIG. 3 is a plan view similar to FIG. 1, illustrating an embodiment of a writing device in which a plurality of light emitting element rows are arranged stepwise.

FIG. 4 is a sectional view similar to FIG. 2, showing another embodiment of the writing device according to the present invention;

FIG. 5 is a sectional view similar to FIG. 2, showing another embodiment of a writing device according to the present invention;

FIG. 6 shows a case in which the image forming position of light passing through the self-focusing rod lens array is shifted in the sub-scanning direction on the photosensitive drum if the photosensitive drum is eccentric in the case of the writing device of FIG. It is the schematic for demonstrating the appearance.

FIG. 7 does not deviate the image forming position of light passing through the self-focusing rod lens array in the sub-scanning direction on the photosensitive drum even if the photosensitive drum is eccentric in the case of the writing device of FIG. It is a schematic diagram for explaining a situation.

[Explanation of symbols]

 1: photosensitive drum (object to be written) 2a, 2b, 2c: light emitting element array 3A, 3B, 3C: self-focusing rod lens array 5: substrate 10a, 10b, 10c: optical axis

Claims (3)

[Claims] 1. A plurality of light emitting element rows in which light emitting elements are arranged in a straight line are provided on a single substrate, and the length of each light emitting element row is made shorter than the maximum writable write width. The plurality of light emitting element rows were arranged in parallel with each other so as to obtain the maximum writing width in the arrangement direction of the light emitting elements, and a self-focusing rod lens array was provided corresponding to each of the light emitting element rows. A writing device characterized by the above-mentioned. 2. The light emitted from each of the light emitting elements of the plurality of light emitting element rows is aligned in the sub-scanning direction on the writing surface of the writing object and forms an image in a straight line along the main scanning direction. 2. The writing apparatus according to claim 1, wherein the light emitting elements and the self-focusing rod lens arrays are arranged. 3. The light-emitting elements and the light-emitting elements such that an optical axis of light emitted from each of the light-emitting elements and passing through the self-focusing rod lens array is perpendicular to a writing surface of a writing object. 2. The writing device according to claim 1, wherein a self-focusing rod lens array is arranged.