JPH0220361A - Led printing head - Google Patents

Abstract

PURPOSE:To perform the input of data by a method not different from a conventional method at all and to provide the interchangeability with a conventional general LED printing head of this kind by arranging serial input data at every N-bit in reverse order in a driving IC for driving respective LED array chips at every block. CONSTITUTION:Serial input data is inputted from the rightmost memory cell of the shift register SR of the leftmost block and, on and after, the leftmost memory cell of the shift register of the (n-1)-th block is connected to the rightmost memory cell of the shift register of the n-th block on the right side of said (n-1)-th one in succession. Whereupon, serial data are stored at every N-bit in reverse order and the light emitting dots on LED array chips 4a, 4b... emit light on the basis of the data made reverse in order at every N-bit. As a result of forming an image on a photosensitive drum 2 in a state inverted and magnified by respective convex lens elements 5a, 5b..., a series of light emitting dot images according to the serial input data are formed on the photosensitive drum 2 at an equal interval.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an LED print head used in an optical information writing device such as an optical printer.

[Conventional technology]

For example, an optical printer transmits light from a row of light emitting dots formed by a plurality of light emitting diodes (hereinafter referred to as LEDs) and an array chip on a print head through an optical lens system supported by the print head. It is configured to expose the photoreceptor by focusing the light onto the photoreceptor, and the optical lens system is an array of light-emitting dots arranged in a column direction, such as Selfoc Lens Array (trademark of Nippon Sheet Glass Co., Ltd.). Generally, a device is used in which the image is formed on a photoreceptor by directly corresponding to the photoreceptor. Therefore, in order to make the print quality uniform over the entire length of the recording paper in the width direction, it is ideally necessary to make the intervals between each dot in the light emitting dot array exactly constant.

[Problem to be solved by the invention]

However, the light emitting dot row is made up of a certain number of unit LEDs.
Since a plurality of LED array chips of a predetermined length, in which elements are assembled in a row, must be arranged in a row, the following problems arise. That is, as shown in FIG. 5, each LED is
Extremely high precision is required in dicing to separate array chips from a single wafer, which has led to increased manufacturing costs and decreased yields of LED array chips. In addition, when bonding the LED array chips to the print head substrate, each chip comes into close contact with each other in the longitudinal direction, so there are many opportunities for the chips to come into contact with each other, which may disrupt the chip arrangement or damage the chip surface. It was often contaminated with adhesive. In this way, in the conventional method, which required the dot spacing of the light-emitting dot array to be constant on the print head, not only did it increase the manufacturing cost of the LED array chip, but there were many factors that could cause print quality to deteriorate. . Therefore, the problem to be solved by the present invention is that the external precision of the LED array chip is not required so much, and moreover, it is possible to obtain good printing quality with simple adjustment.
To provide an ED print head, and further,
This LED print head eliminates the need to change the input method of print data, in other words,
The objective is to ensure compatibility with the ED print head.

[Means to solve the problem]

In order to solve the above problems, the present invention takes the following technical measures. A plurality of LF and D array chips each having N light emitting dots at equal intervals and driven by a drive circuit for each block are arranged in series on the substrate, and the light from each light emitting dot is directed onto the photoreceptor. L with a focusing optical lens system
In the ED print head, each of the LED array chips is arranged in a line at regular intervals in the longitudinal direction, and the optical lens system is configured by assembling convex lens elements facing each other in correspondence with each LED array chip. , The drive circuit for each block is characterized in that shift registers for storing N bits of serial input data are arranged in reverse order with respect to the direction of data progression between each block.

[Effect]

As can be easily understood from FIG. 3, as long as the object point of a convex lens is beyond the focal length (f), imaging will occur on the opposite side of the lens. Then, the distance from the lens to the object point is longer than the focal length (f), and twice the focal length (2f
), the distance from the lens to the image point is longer than the distance from the lens to the object point. In other words, in this case, what is at the object point is necessarily magnified and formed into an inverted image on the opposite side of the lens. In the LED print head of the present invention, each LED
The array chips are arranged at regular intervals in the longitudinal direction, and the light emitted from the dots of each LED array chip is imaged on the photoreceptor by a convex lens element corresponding to each chip. Here, by setting the distance from the light emitting part of the LED array chip to the convex lens element to be longer than the focal length (f) of the lens and shorter than twice the focal length (2f), the light emitting dot image of each LED array chip can be , it is possible to enlarge the image at a predetermined magnification and form an image on the photoreceptor. Therefore, even if the distances between the LED array chips are large on the print head as described above, the light emitting dot images of each LED array chip can be formed on the photoreceptor so that they are successively spaced at equal intervals. . Further, the light emitting dot images formed on the photoreceptor corresponding to each LED array chip are inverted images because a convex lens element is used in the optical lens system.
By arranging the shift registers that store N bits of serial input data in the block drive IC for each ED array chip in the reverse order of the data progression direction between each block, it is possible to Since the dot light emitting parts are arranged in the reverse order, when each of the dot light emitting parts in the reverse order is turned upside down on the photoreceptor, all the light emitting dot images are corrected to be continuous in correspondence with the serial input data.

【Effect of the invention】

According to the present invention, the LED array chips bonded on the substrate of the print head can be arranged at regular intervals, so that the external precision of each LED array chip, that is, the dicing precision is not required so much. This has the effect of dramatically improving the yield of LED array chips compared to the conventional method and simplifying the dicing process. In addition, since each LED array chip is not brought into close contact with each other during bonding, there are fewer chances of contact between the already bonded chip and the chip being bonded, and it is possible to avoid scratches and dirt on the chip surface. This has the effect of making the bonding work easier and improving the bonding quality. In the present invention, a method is adopted in which the drive IC that drives each LED array chip block by block reverses the arrangement of every N bits of serial input data to cause the light emitting dots of each LF and D array chip to emit light. Therefore, data input can be performed in a manner that is no different from the conventional method, and therefore, the LED print head of the present invention is compatible with conventional LED print heads of this type.

[Explanation of Examples]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic diagram of an optical printer constructed using the LED print head 1 of the present invention. The LED print head 1 is arranged parallel to the surface of a photosensitive drum 2 as a photosensitive member. The substrate 3 of the LED print head 1 includes a plurality of (for example, 16) LEDs.
D array chips 4a, 4b, . . . are bonded in a row in the longitudinal direction with their ends separated by a certain distance. Each LED array chip 4a, 4b... has unit light emitting dots made up of N (64 or 128) LED elements formed in rows at equal intervals on a GaAsP substrate having a rectangular cross section. It is obtained by forming a large number of array chips on one wafer at once and then dividing them into unit array chips by dicing. Between the LED array chips 4a, 4b, etc. and the photosensitive drum 2, light emitted from the light emitting dots is transmitted to the photosensitive drum 2.
An optical lens system 5 is arranged to focus the light emitting dots upward and form an image of the row of light emitting dots. This optical lens system 5 includes each of the above-mentioned LED array chips 4a.
, 4b..., and the same number of convex lens elements 5a, 5b... as the chips are assembled, and in this example, each of these convex lens elements 5a, 5b... It is configured to be held in a lens holder 6. That is, the lens holder 6 includes the LED array chip 4a,
The lens holding hole 5a has the same pitch as the arrangement pitch of 4b...
, 6b..., and can be made by resin molding. and each convex lens element 5a
, 5b, . . . are fixedly held in the lens holding holes 5a, 5b, . In this example, as shown in FIGS. 1 and 2, the holes are placed on the back surface of the lens holder 6 from the middle part of each lens holding hole 6a, 6b, etc. toward the gap between the ED array chips. An extending light shielding plate 7 and reinforcing ribs 8 extending downward from the back surface are integrally formed at both ends of the lens holder in the width direction. As a result, the space from each LED array chip 4a, 4b, . . . to the convex lens elements 5a, 5b, . This prevents the print quality from deteriorating due to leakage into the adjacent space or the outside of the lens holder 6. In addition, the lens holder 6
is attached to both ends of the substrate of the LED print head 1 so that its position can be adjusted in the vertical direction. Further, each of the above convex lens elements 5a, 5b... is, for example,
It is possible to use an aspherical lens made of hard resin with little aberration. Furthermore, the lens and holder may be integrally processed from plastic, and of course a spherical lens may also be used. When constructing an optical printer, the relationship among the LED array chips 4a, 4b, . . . , the optical lens system 5, and the photosensitive drum 2 in the ED print head 1 described above is determined as follows. First, convex lens elements 5a, 5b of the optical lens system 5...
and the corresponding LED array chips 4a, 4b.
. . is set to a value longer than the focal length (f) of the convex lens elements 5a, 5b, . . . and shorter than twice the focal length (2f). At this time, convex lens elements 5a, 5
A light emitting dot image is formed on the opposite side of the convex lens element 5a of this image. 5b... is longer than the distance between the convex lens element and the LED array chip. That is, an enlarged inverted image of the light emitting dot row on the LED array chip is formed at the image point of the convex lens element. Then, the surface of the photosensitive drum is placed at this image point position. The magnification rate by the convex lens elements 5a, 5b... is L
Arrangement pitch interval D of ED array chips 4a, 4b...
It is determined by the ratio of I to the distance D2 between the light emitting dots at both ends of each LED array chip. By doing this, even if the LED array chips 4a, 4b, . . . Images can be formed at equal intervals. That is, on the photosensitive drum 2, images can be formed so that the image interval a between the light emitting dots at the ends of adjacent LED array chips is equal to the image interval a between the light emitting dots within the same chip. Since the optical lens system 5 is supported such that both ends of the lens holder 6 can be adjusted vertically, the distance a and the distance must match within a range where defocusing of the image on the photoreceptor is allowed. This can be done relatively easily by finely adjusting the lens holder 6 up and down in FIG. By the way, in this LED print head, since the optical lens system 5 is composed of convex lens elements 5a, 5b, . . . corresponding to the respective LED array chips 4a, 4b, . Array chips 4a, 4b
The light-emitting dot images of . FIG. 4 schematically shows a driving circuit for the LED array chips 4a, 4b, . . . . Each LED array chip 4a. 4b... is a special drive IC 9a for each block. 9b... These drive ICs 9a, 9b, . . . each drive each unit LED on the LED array chip that constitutes N unit light emitting dots
A shift register SR has N memory cells corresponding to the number of elements, a launch circuit LA launches data in this shift register in parallel using a launch signal, and a strobe signal inputs data in a latch circuit LA to each LED. It includes a drive circuit DR that outputs output to the element. The anode of each unit LED element is individually connected to each output terminal of the drive circuit DR in correspondence with the arrangement of the elements, and
The cathode of each unit LED element is connected to ground. Now, in the present invention, the shift registers SR are arranged in reverse order with respect to the direction of data progression between each block. That is, serial input data is sequentially transmitted to each shift register SR from the left block to the right block in FIG. 4, but the shift registers are configured in the reverse order of the overall data transmission direction. It is. Along with this, serial input data is configured to be input from the rightmost memory cell of the shift register of the leftmost block, and thereafter sequentially input from the leftmost memory cell of the shift register of the n-1th block. , and the rightmost memory cell of the shift register of the n-th block on the right are connected in series. Then, the shift register SR of each block has N serial data in the arrangement on the print head.
Each bit will be stored in reverse order, and the light-emitting dots on the LED array chips 4a, 4b, . . . will emit light based on the data reversed every N bits. The dots that emit light in the reverse order are inverted and enlarged by the convex lens elements 5a, 5b, and formed into an image on the photosensitive drum 2. As a result, a series of emitted light according to the serial input data is formed on the photosensitive drum 2. Dot images are formed at equal intervals. As described above, according to the LED printer head of the present invention, the LED array chips constituting the light emitting dot row can be separated from each other and bonded to the substrate.
There is no problem with lowering the required precision of the outer shape of the D-array chip, which contributes to a significant reduction in the manufacturing cost of LED array chips for LED printheads, and also improves the yield of the chips. In addition, since the configuration is such that the light from the dots of each LED array chip is magnified and imaged on the photoreceptor using convex lens elements, the light can be focused on the photoreceptor by adjusting the position of the optical lens system including the convex lens elements. It becomes easy to make the intervals between all the luminescent dot images constant, and the printing quality improves. Furthermore, each L
The issue of inverted images on the photoreceptor for each ED array knob has been addressed by improving the shift register arrangement of each drive IC within the print head, so data input to the print head is now easier than before. Therefore, the LED print head of the present invention can be used as the conventional LED print head.
Compatible with D printheads.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the LED print head of the present invention and an optical printer using the same, and FIG. 2 is the nm of FIG. 1.
3 is a diagram illustrating the operation, FIG. 4 is a schematic diagram of a print head drive circuit, and FIG. 5 is a diagram illustrating a conventional example. 1...LED print head, 4a, 4b...LE
D array chip, 5... optical lens system, 5a, 5b.
...Convex lens element, SR...Shift register.

Claims (1)

[Claims] (1) Multiple LEs with N light-emitting dots at equal intervals, each driven by a drive IC for each block
In an LED print head, the D-array chips are arranged in series on a substrate and are equipped with an optical lens system that focuses light from each light-emitting dot onto a photoreceptor. The optical lens system is configured by assembling convex lens elements facing each other in correspondence with each LED array chip, and the drive IC of each block stores data for N bits of serial input data. An LED print head characterized in that shift registers are arranged in reverse order with respect to the direction of data progression between each block.