JPH0462166A - Optical image printer - Google Patents

Abstract

PURPOSE:To form an accurate latent image on an image carrier by forming a second light emitting element which conducts the same light emitting operation as that of a first light emitting element formed at the other end of a chip adjacent to one end of each chip, and arranging a plurality of single lenses at an interval for focusing in duplicate by the adjacent lens in the second element. CONSTITUTION:An LED head 4 is composed of an LED panel 15 and a single lens array 16. The panel 15 is composed of a printed board 15a and an LED arranging board 15b, the array 16 is arranged directly under an LED element 18 formed on the board 15b, and a plurality of single lenses 16a-16c,... are arranged in one row at a predetermined interval. For example, each chip is formed by 104 pieces of the elements 18a-l, 18a-2,.... In the LED element of each chip, focusing is executed by one of the lenses 16a, 16b,..., light emissions of two LED elements are duplicated to optically write in a focused boundary of the lenses 16a, 16b,..., and focused on the periphery of a photosensitive drum 2.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an image forming apparatus using electrophotographic technology,
In particular, the present invention relates to an optical printing device that forms an accurate latent image on an image carrier.

[Conventional technology]

As an image forming apparatus using electrophotographic technology, for example, LE
D printers are known. This LED printer optically writes image data output from a host device onto an image carrier through an optical writing head composed of an LED, etc., and develops an electrostatic latent image formed by this optical writing into a toner image. The toner image is then transferred to paper to create an image on the paper.

In the above-described apparatus, the optical printing device that performs optical writing on an image carrier such as a photoreceptor drum includes the above-mentioned LED as a light emitting element, and an image forming device that forms an image of the emitted light of the LED on, for example, the photoreceptor drum. Consists of lenses. This optical printing device controls blinking of a large number of LED elements arranged in an array according to image data, and uses an imaging lens to optically write the light emitted from the LED elements onto an image carrier. be.

Conventionally, in an optical printing apparatus having the above-mentioned configuration, a plurality of single lenses are used to form an image of light on an image carrier, with one single lens responsible for emitting light from a predetermined number of LED elements. The image forming process is performed using

For example, in an optical writing head with 2000 LED elements arranged in an array, if one single lens is responsible for imaging 100 LED elements, then 20 single lenses are arranged parallel to the micro shutter. This is the configuration to set.

[Problems with the Prior Art] However, in the conventional optical printing device, among the LED elements assigned to each single lens, the light emitted from the LED element located at the end is focused near the position of the image carrier where the image is formed. The transmitted light of the LED element, which is imaged by a single lens arranged next to it, is also imaged.

For this reason, if the placement positions of the LED elements and single lenses and the spacing between the LED elements and the image carrier are not set with high precision, the optical images at the boundaries formed by adjacent single lenses will interfere with each other. However, it may not be possible to perform optical writing with a sufficient amount of light on the image carrier, or conversely, unnecessary optical writing may be performed at the above-mentioned boundary.

For this reason, for example, line-shaped low potential areas and high potential areas unrelated to the image data are formed on the electrostatic latent image formed on the image carrier, and white lines and black lines are generated on the paper on which the image is formed. This results in a marked deterioration in print quality.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide an optical printing device that can prevent the formation of unnecessary lines and create images with excellent print quality.

[Summary of the Invention] In order to achieve the above object, the present invention includes an optical writing head in which a large number of n light emitting elements are arranged in an array and is provided facing an image carrier, and an optical image generated by the light emitting elements is formed. In an optical printing apparatus, the optical printing apparatus includes an imaging optical system including a plurality of single lenses arranged along the light emitting element array to form an image on the image carrier, wherein the one single lens is formed on a chip in a predetermined number of the light emitting elements. An image of the element array is formed, and a second light emitting element is formed at one end of each chip to perform the same light emitting operation as the first light emitting element formed at the other end of the adjacent chip. The light emitting element is characterized in that a plurality of the single lenses are arranged at intervals such that adjacent single lenses form overlapping images.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing the overall configuration of an LED printer to which the optical printing device of this embodiment is applied. In the figure, an LED printer 1 includes a photoreceptor drum 2 as an image carrier, a charger 3 sequentially arranged near the circumferential surface of the photoreceptor drum 2, and an LED.
It is composed of a head 4, a developing device 5, a transfer device 6, and a cleaner 7. Further, between the photosensitive drum 2 and the transfer device 6, a paper P carried out from a paper feed cassette 8 by a paper feed roller 9 is transported along a guide plate 10 by a transport roll 11 and a standby roll 12. In addition, a paper detection sensor 1 is installed on the paper transport path.
3 is provided, and the passage of paper P is detected. Further, the fixing roll 14 on the conveyance path is a device for thermally fixing the toner image on the paper P as described later.

On the other hand, the LED head 4 includes an LED panel 15 and a single lens array 16. An image data output circuit 17, which will be described in detail later, is connected to the LED panel 15. This image data output circuit 17 is configured to be supplied with image data from a host computer or the like.

FIG. 3 is a diagram showing a detailed arrangement configuration of the LED panel 15 and single lens array 16 that constitute the above-mentioned LED head 4. The LED panel 15 is composed of a printed board 15a and an LED mounting board 15b arranged on the printed board 15a, and a large number of ED elements 18 are mounted on the LED mounting board 15b.
is formed. In addition, this LED arrangement board 15b is specifically constructed by linearly arranging chips on which a predetermined number of LED elements 18 are formed.

On the other hand, the single lens array 16 is arranged directly below the LED element 18 formed on the LED arrangement board 15b, and includes a plurality of single lenses 16a, 16b, 16c at a predetermined interval.
, ... are arranged in the - column. Each single lens 16
a, 16b, 16c, . . . form an image of light emitted from a predetermined number (104 in this embodiment, which will be described later) of LED elements 18 located directly above each of them on the circumferential surface of the photoreceptor drum 2 described above.

In FIG. 1, the above-mentioned single lens array 16 is the main body,
2 is a partially enlarged view of a portion including a D element 18 and a photoreceptor drum 2. FIG. Note that this figure is a partially enlarged view particularly including the single lenses 16a and 16b and the LED elements whose images are formed by the single lenses 16a and 16b. LED element 18a shown in the same figure
-1, 18a-2, ... 18a-103, 18a-1
04 is an LED element whose emitted light is imaged on the photosensitive drum 2 by a single lens 16a, and an LED element 18b-
1, 18b-2, ... 18b-103, 18b-10
4, the light emitted from the single lens 16b is directed to the photosensitive drum 2.
This is an LED element that is imaged.

Here, the LED elements 18a-3 to 18a-1 indicated by ■ marks
02, and LED elements 18b-3 to 18b- indicated by a seal
102 is an element to which regular image data is supplied from the image data output circuit 17, and is an LED element 18a indicated by .
-1, 18a-2, 18a-103, 18a-104,
and LED elements 18b-1, 18b-2, 1 indicated by ○ marks
8b=103.18b-104 is image data output circuit 1
This is an element to which auxiliary image data is supplied from 7.

It should be noted that the above-mentioned marks 1, . be. Then, the specific LED elements 18a-1, 1
The shapes of the light emitting surfaces such as 8a-2, . . . are the shapes shown in FIGS. 4(a) and 5(a). Here, FIG. 4(a) shows the shape of the light emitting surface of the LED element other than the end of each chip on which 104 LED elements are formed, and the width is S in the main scanning direction shown by the arrow. Specifically, LED elements 18a-5 to 18a- that are not superimposed on the imaging light described later.
100, and LED element 18 b-5, 18b-100
This is the shape of the light emitting surface. In addition, Fig. 5(b) shows the shape of the light emitting surface at the end of each chip, which is composed of a narrow S' in the same main scanning direction. LED elements 18a-1, 18a-2, 18a-1
03, 18a104, and LED element 18b-1, 18
This is the shape of the light emitting surface of b-218b-103 and 18b-104.

In addition, the 104 LED elements 18a shown in the above-mentioned
-1, 18a-2, =18a-104 are formed on one chip, and the light emitted from these LED elements is imaged on the photosensitive drum 2 by the imaging lens 16a. Similarly, 104 LED elements 18b-1, 1 indicated by a circle
8b-2, . . . 18b-104 are also formed on one chip, and the light emitted from these LiED elements is imaged by the imaging lens 16b.

And each LED element 18a-1, 18a-2,...
etc. and the image data output circuit 17 are connected as follows. First, LED elements 18a-5 to 18a-1
00 and the LED elements 18b5 to 18b-100 are connected one-to-one to an output terminal (not shown) of the image data output circuit 17, and a control signal for lighting/non-lighting is output from the image data output circuit 17. Further, the LED element 18a-3 and the auxiliary LED element 18b-103 on the adjacent chip are connected to the same output terminal (not shown) of the image data output circuit 17, and both are supplied with the same image data. therefore,
Although the image data supplied to the LED element 18b-103 is auxiliary image data, it is actually supplied to the LED element 18a-3.
This is the same data as , and will be explained as auxiliary image data for convenience of explanation. Also, the above configuration is LE
The position ↑■ where the light emitted from the D element 18a-3 is imaged on the photoreceptor drum 2 by the imaging lens 16a is the same as the position where the light emission from the LED element 18b-103 is imaged through the imaging lens 16b. Position of? ■Based on what is set. Similarly, the LED element 18a-4 and the auxiliary LED element 18b''-104 on the adjacent chip are connected to the same output terminal of the image data output circuit 17, and the same image data is supplied to both. 18a-
Are the light emitted from LED element 4 and the light emitted from LED element 18b-104 at the same position on photosensitive drum 2? ■Based on being imaged.

Furthermore, as described above, auxiliary LED elements 18a-1, 1
8a-2 also corresponds to the LED element 18 of the adjacent chip.
It is connected to the same output terminal of the image data output circuit 17 together with b-101 and 18b-102, and the same control signal for lighting/non-lighting is supplied to each of them. In addition, the LED element 18a
The light emission from -1, 18b-101 is focused on ↑■ shown in the same figure, and the light emission from LED elements 18a-2, 18b-102 is shown in the same figure. The image is formed in ■.

In the optical printing apparatus having the above configuration, the imaging lens 1 is as follows.
The optical writing process on the photoreceptor drum 2 will be explained with a focus on the optical writing operation at the boundary between 6a and 16b.

First, when the printing process of the LED printer 1 using the optical printing device of this embodiment is started, the photosensitive drum 2 rotates in the direction of the arrow, and a charger 3 such as - is applied onto the photosensitive drum 2. Charging processing is performed. Through this process, the photoreceptor drum 2
A negative charge is applied to the circumferential surface of the LED head 4.
The optical writing process is executed.

This optical writing process is performed from the image data output circuit 17 to each LE.
This is done by outputting a control signal to the D elements 18a-1, 18a-2, . . . , and each LE
The D elements 18a-1, 18a-2, . . . are driven to turn on/off.

6 to 8 are diagrams particularly for explaining the optical writing state near the boundary between the imaging positions of the single lenses 16a and 16b, and
When the distance between the ED elements 18a-1, 18a-2, etc. and the photosensitive drum 2 is short (Fig. 6), coincides (Fig. 7), or wide with respect to the predetermined distance. (Figure 8)
FIG.

First, in the case of FIG. 6, the LED elements 18a-1, 18a
-2, etc. and the photoconductor drum 2 is shorter than a predetermined distance (indicated by the symbol -), for example, when the LED head 4 or the arrangement of the photoconductor drum 2 This is a case where this occurs due to an error or a design error.In this case, the LED elements 18a-1, 18a-2, and 18a
18a-1' which is the imaging light of -103, 18a-104
18a-2', and 18a-103', 18a-
The irradiation position of each lens 104' is on the optical axis 1 of the imaging lens 16a.
6a' direction (arrow A direction), and LED element 1
8b-101, 18b-102, and 18a-3, 18
18b-101' 18b- which is the imaging light of a-4
The irradiation positions of 102', 18b-3, and 18b-4' move in the direction of the optical axis 16b' of the imaging lens 16b (in the direction of arrow B).

The cause of this is the LED elements 18a-1, 18a-2,...
As the distance between the photoreceptor drum 2 and the like becomes narrower, the LED element 18a-1, which is imaged by the imaging lens l6a,
, 18a-2, 18a-103, 18a-104 become closer to the optical axis 16a' of the imaging lens 16a,
Furthermore, the LED element 18b- which is imaged by the imaging lens 16b
101, 18b-102, and 18 b-3, 18b-
This is because the imaging position of the light No. 4 approaches the optical axis 16b' of the imaging lens 16b. Therefore, the brightness of the light received by the photoreceptor drum 2 at this time has the characteristics shown in FIG. 2(b).

Note that the solid line shown in FIG.
The brightness of light from 8a-2, 18a-103, 18a-104 is shown, and the dotted line indicates the LED elements 18b-101, 18b.
The brightness of light from -102, 18b-3, and 18b-4 is shown. Further, there is a difference of Δd in the peak values of brightness from each of the single lenses 16a and ieb. Therefore, the composite brightness of the photoreceptor drum 2 at this time has the characteristics shown in FIG. And the central type ■′ of each brightness? ■′、↑■? ■′
,? ■′? ■'The pitch of the dots (dot pitch DOP) is constant, and is the dot pitch at each imaging position? ■~↑■ and the center of each brightness ↑■'~↑■' match.

Therefore, when configured as in this embodiment, the LED element 1
Even if the distance between 8a-1, 18a-2, .

Furthermore, the shape of the light emitting surface is different from that shown in FIGS. 4(a) and 5(a).
) As shown in the figure, the image forming position is different between the end and other parts of each chip. ■~? Although it is thought that the amount of light received at point (3) is lower than that of the center portion and other parts other than the end portions, the amount of light received does not decrease for the following reason. That is, 1. LED elements 18a-5 to 18a arranged other than the end of each chip
The -100 light emitting surface has a width S in the main scanning direction as shown in FIG. 4(a), and has a brightness l even in a low brightness portion as shown in FIG. 4(b). On the other hand, LED elements 18a-1 and 18a-2 arranged at the end of each chip
18a-103, 18a-104, 18b-1, 18b
-2, 18b-103, 18b-104 light emitting surface is the fifth
As shown in Figure (a), the formation width is S' in the main scanning direction.
As shown in FIG. 5(c), the low luminance part has a low luminance l', but as mentioned above, the image forming position? ■～↑■ 2
Figure 5 (C)
As shown in the figure, the brightness is l'' even in the low brightness area.Therefore, since the amount of received light is determined based on the low brightness area,
There is no difference between the ends of the single lenses 16a and 16b and other parts.

Next, in the case of FIG. 7, the LED elements 18a-1, 18a-
2, . . . and the photosensitive drum 2 is a predetermined value. In this case, the LED elements 18a-1, 18a-
2, 18a-103, 18a-104 imaging light, and L
ED elements 18b-101, 18b-102, 18b-3
, 18b-4 are at the same position? ■~? The images are respectively formed in ■. Therefore, the brightness of the light received by the photoreceptor drum 2 at this time is the same at the same imaging position as shown in FIG. The characteristics are shown in . Note that the straight lines I and 2 connecting the peaks of each luminance shown in FIG. Also, in this case, of course, the center of each brightness? ■
′ and ↑■′,? ■? ■′、? ■′? ■The pinch between '' (dot pitch DOP) is constant, and each imaging position? ■~? ■ and the center of each brightness? ■′~? ■' is defeated once.

Next, in the case of FIG. 8, the LED elements 18a-1, 18a
-2, . This is a case where this occurs due to a placement error or a design error. In this case, 18
a-1'18a-2', and 18a-103',
Each irradiation position of 18a-104'? ■~? (2) is the optical axis 1 of the imaging lens 16b, contrary to the case of FIG. 6(a) above.
6b' direction, and LED elements 18b-101,
18b-102, and the irradiation position of each of 18b-101'18b-102' and 18b-3'18b-4' which are the imaging lights of 18b-3 and 18b-4?
■~↑■ also move in the direction of the optical axis 16a' of the imaging lens 16a. The reason for this is that the LED elements 18a-1, 18a-2, . . .
By increasing the distance between the LED element 18a-1 and
, 18a-2, and 18a-103, 18a-104 are closer to the optical axis center 16b', and the LED element 18b-101 is imaged by the imaging lens 16b.
, 18b-102, and 18b-3, 18b-4 because the imaging position of the light approaches the optical axis center 16a'.

Therefore, the brightness of the light received by the photoreceptor drum 2 at this time has the characteristics shown in FIG. 2B, and the combined brightness received by the photoreceptor drum 2 has the characteristics shown in FIG. In addition, in this case, is the center of each brightness? ■′? ■′、? ■′ and ↑■′,? ■
The pitch between ' and ↑■' (dot pitch DOP) is - constant, and the center of each image forming position t■ to ↑■ and each brightness? ■
'~↑■' match, LED elements 18a-1, 18a-
Even if the distance between the photoreceptor drum 2 and the photoreceptor drum 2 is widened by a predetermined distance, there is no adverse effect on the imaging light on the circumferential surface of the photoreceptor drum 2.

Further, although the shape of the light emitting surface is different from that described above, for the same reason as described above, the amount of received light does not differ between the end of the imaging position and the other portions.

As described above, in this embodiment, a large number of LED elements 18a-1
, 18a-2, . . . are formed on each chip in 104 pieces,
The LED elements of each chip are replaced by one single lens 16a, 16b.
,... are in charge of image formation, and each single lens 16a, 16b
, . . . by overlapping the light emission of the two LED elements, it is possible to provide leeway in the assembly, design, etc. of the LED panel 15 and the photoreceptor drum 2.

Incidentally, in this embodiment, the imaging processing for the single lenses 16a and 16b was particularly explained, but the other single lenses 16c and 16d
8. The same applies to...

Furthermore, the number of LED elements that supply auxiliary image data is not limited to two at one end.

Furthermore, although the optical printing apparatus of the present invention is applied to an LED printer, it can of course be used not only for an LED printer but also for an apparatus that performs optical writing on an image carrier.

(Effects of the Invention) As described above in detail, according to the present invention, there is no interference of optical writing light near the image forming position boundary of adjacent single lenses as in the conventional case, and unnecessary line-shaped It can prevent optical writing and create images with excellent print quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical printing device according to an embodiment, FIG. 2 is an overall block diagram of an LED printer to which the optical printing device according to an embodiment is applied, and FIG. 3 is a block diagram of an optical printing device according to an embodiment. 4(a) and 5(a) are diagrams explaining the shape of the light emitting surface of the LED element; FIG. 4(b), FIG. 5, etc.), (C) FIG. 6(a) is a diagram showing the brightness of light from the LED element that is received by the photoreceptor drum.
, Fig. 7(a) and Fig. 8(a) are diagrams explaining the deviation of the imaging position of a single lens, Fig. 6(c), Fig. 7(b), and Fig. 8(b) 6 (C), 7 (C), and 8 (c) show the combined brightness of light from the LED elements to the photosensitive drum. 4. 15. . 16. . 16a. 17.. 18, 1 LED head, LED panel, single lens array, 6b, . . . single lens, image data output circuit, a-1, 18a-2...LED element.

Claims (1)

[Claims] n light emitting elements arranged in an array, an optical writing head provided with the light emitting elements facing an image carrier, and a single lens for forming an optical image by the light emitting elements on the image carrier. In an optical printing device including a plurality of imaging optical systems arranged along the light emitting elements, each of the plurality of single lenses is responsible for imaging a predetermined number of the light emitting elements formed on a chip, A second light emitting element that performs the same light emitting operation as the first light emitting element formed at the other end of the adjacent chip is formed at one end of each chip, and the second light emitting elements are each formed by an adjacent single lens. An optical printing device characterized in that a plurality of the single lenses are arranged at intervals such that images are formed overlappingly.