JPH05289190A - Image bar printer increased in resolution in process direction - Google Patents

Abstract

PURPOSE: To improve the level of address probability in a process direction by controlling the duration time and level of a current to an LED. CONSTITUTION: In the image bar printer corrected so as to form line images different tin resolution between the process direction and a process orthogonal direction, addresses in an LED array 24 are selectively specified to generate a line image output to be modulated. An output from the LED is focused by a 1× SELFOC lens array and a line image in which spot size in the process orthogonal direction is larger than that in the process direction is formed. A pair of cylindrical lenses 30, 32 are arranged adjacently to the inlet and outlet faces of a gradient index lens array 28 along an optical path. The lenses 30, 32 are designed so as to reduce an output spot projected from the LED at a certain reuction rate.

Description

Detailed Description of the Invention

The present invention relates to an electronic printer which utilizes an address image bar to form a line image on a photoreceptor moving in the process direction. In particular, the invention relates to increasing the resolution of scan lines on the surface of the photoreceptor in the process direction.

According to a first aspect of the invention, the image
Bar printers are addressable in the process direction by introducing a pair of cylindrical lenses on both the entrance and exit faces of the gradient index lens array. As an example, a 300 spi (118 spots / cm) LED image bar forms a line image at a 1: 1 magnification in the process orthogonal direction, but with a properly designed pair of cylindrical lenses, 2: 1
Reduction ratio reduces the spot size in the process direction by a factor of 2, resulting in a resolution in the process direction of 600 spi (236 spots / c) due to improved addressability for the print bar.
m) will be raised.

As will be described in more detail below, the above example utilizes an embodiment of a single row gradient index lens array. However, for single row arrays, the radiometric rate of the system is limited. According to a second aspect of the invention, a two-row array is shown, which doubles the radiometric rate by forming the two rows in a non-parallel orientation in the manner described below. ..

That is, the present invention relates to an image bar having a linear array of light emitting elements, a photoconductive member adapted to move in a process direction through an exposure mechanism, and connected to said image bar. Image signal source means,
Means for addressing the image bar to generate a light output representative of the input of the signal source; and in cooperation with the image bar, a line image in the process orthogonal direction to the photoconductive member. For an image bar printer, wherein the line image is formed from a focused combined output spot corresponding to the output of the light emitting element. Wherein the optical system includes a linear gradient index lens array disposed between the image bar and the photoconductive member, and a first gradient color lens array disposed between the image bar and the lens array. A cylindrical lens and a second cylindrical lens disposed between the lens array and the photoconductive member are included, the optical system being larger than the spot size in the process direction. Having a size, by spot combined the focus in a process direction orthogonal so as to form the line image.

FIG. 1 is a side view of an image bar print system incorporating the optical system of the present invention.

FIG. 2 is a diagram of the optical system shown in FIG. 1 showing the locus of a single ray passing through the optical system.

FIG. 3 is a diagram showing a second embodiment of the optical system shown in FIG.

FIG. 1 shows a printer utilizing a standard width LED type writing bar and incorporating the focusing optics of the present invention. The present invention is, for example, an LCD.
(Liquid crystal display) or other types of imaging using an electroluminescent display as an image bar
It can also be used in a system.

As shown in FIG. 1, an exemplary printer 10 includes a photoreceptor drum 12 on which an imaging member is rotatably supported in a suitable housing or enclosure (not shown). When the printer is activated, a suitable motor (not shown) rotates the drum 12 in the process direction indicated by the solid arrow. A corona discharge device, such as a corotron 14, is arranged to act on the drum 12, which serves to apply a uniform electrostatic charge to the photoconductor drum 12 in preparation for exposure.

The photoconductor drum 12 is exposed to the exposure mechanism 15 downstream of the corotron 14 by a method which will be described later in more detail.
Exposure is performed, and an electrostatic latent image is formed on the surface of the photoconductor drum 12 by such exposure. After the exposure, the developing mechanism 16 develops the electrostatic latent image.

After the development of the electrostatic latent image, the developed image is shown in the transfer mechanism 18, in this case as copy paper 20, which is sent in time with the arrival of the developed image. , Is transferred to a compatible copy substrate material. The copy sheet 20 bearing the developed image is conveyed to a suitable fusing or fusing device (not shown) to provide a permanent attachment of the toner image to the copy sheet. For example, a plurality of light emitting diodes (LE
D) Image writing bar 22 that can be configured from 24
It is provided. The LEDs 24 are arranged in one or more linear arrays or columns that are in the plane of the page, which is also referred to as the process-orthogonal direction in the past, ie in a direction perpendicular to the process direction. Extends to. The image signal source 26 is connected to the bar 22 via an input line 27. The signal source 26 can be a data communication channel, a raster input scanner, or the like. The bar 22 has a driver, a shift register,
And an LE including a latch circuit according to the image signal.
A circuit configuration suitable for performing selective activation of D24 (control of on / off time) is incorporated. US Patent No. 4,
Nos. 731,673 and 4,689,694 disclose typical LED energizing and driving circuits according to the prior art. The contents of these patents are incorporated herein by reference. The image rays from the bar 22, which consist of the output light spots from each LED emitter, have a gradient index lens array 28 and first and second
Is coupled to an optical system 25 including cylindrical lenses 30 and 32. The lens array 28 is composed of a plurality of gradient index optical fibers arranged in a linear array 29. Array 28 also extends in the plane of the page. The output of the LED 24 from the print bar 22 is
Coupled to array 28 by a first cylindrical lens 30. The output from array 28 is focused onto the photoconductor drum via a second cylindrical lens 32 to form a line image of the combined spots in the process-orthogonal direction. As mentioned above, the spot size of the LED output spot focused in the process orthogonal direction (in the plane of the page) is L along the entire length of the bar 22.
It is a function of the mounting density of the ED elements 24. The size of the LED output spot that is focused in the process direction is
The reduction is performed according to the reduction rate determined by the design characteristics of the cylindrical lenses 30 and 32.

According to a first aspect of the invention, an optical system consisting of two cylindrical lenses 32, 32 and a lens array 28 provides a focused LED output spot in the process direction. -The size is reduced at a reduction ratio of 2: 1 but 1: 1 in the process orthogonal direction.
It is designed to work as-is at a magnification of (same resolution as obtained by an LED element). In the preferred embodiment, the print bar 22 includes a 300 spi LED image constructed in accordance with the conventional technique described in US Pat. No. 4,905,021, the contents of which are incorporated herein by reference.・ It is a bar. The Selfoc lens array 28 is, for example,
Applied Optics (April 1980, 19th)
Vol. 7, No. 10, pp. 1035-1038), "Gradient Index Optics: Review (A Revie
w) ”consisting of a single row of gradient optical fiber constructed according to the conventional technique described in the paper. Each L
The ED42 is an 84.6 micron radiator. The cylindrical lenses 30, 32 have an image on the surface of the photoconductor composed of 84.6 micron spots in the process orthogonal direction and 4 in the process direction, as described below.
It consists of 2.3 micron spots and is designed to have a potential resolution of, for example, 300 spi in the process orthogonal direction versus 600 spi in the process direction. The resolution in the process direction is
It can be increased by appropriately increasing the pulse repetition rate of the LED.

Referring now to FIG. 2, the optical imaging system 25 is shown by the trajectory of a single ray through the system. In Table 1, first, the magnification is −. 5
Shown for a 032x cylindrical / spherical imaging system. Lens array 28 is a radial, symmetrical, single row, gradient index lens array. The lens array 30 is a cylindrical lens having a thickness of 3 mm, and the lens 32 is a cylindrical lens having a thickness of 8.154 mm. The collection F / number of the system is -9.026 and the total conjugate is 27.8846 mm. In the process direction, this optic is an 84.6 micron LED
Imaging from element 22 to 42.3 microns.
In Table 2, the magnification in the process orthogonal direction is-.
A 9996x system is shown. For this reference direction, the collection F / number of the system is 9.73 and the total conjugate is the same 27.8846 mm. Therefore, in the process direction, the optics are 84.6 micron LEDs.
Perform 84.6 micron imaging on the radiator.

[0014]

[Table 1]

Effective focal length. ． ． -3.7317 entrance pupil diameter. ． ． ． 0.5000 rear focal length. ． ． 0.9637 Entrance pupil distance. ． ． ． 0.0000 front focal length. ． ． 2.5519 Injection pupil diameter. ． ． ． 0.7314 F / number. ． ． ． ． ． -7.4633 Ejection pupil distance. ． ． ． 6.5225 Half angle of view. ． ． ． ． ． 0.0000 Paraxial image height. ． ． ． ． ． ． 0.0000 image distance. ． ． ． ． ． 2.8414 Paraxial image distance. ． ． ． ． ． 2.8414 full length. ． ． ． ． ． ． 20.1780 Lens reference wavelength (mm) 720.0 Reduction rate. ． ． ． ． ． -0.5032 All tracks. ． ． ． ． 27.8846 Finite F / number. ． ． ． -4.9026 object distance. ． ． ． ． ． ． 4.8652

[0016]

[Table 2]

Effective focal length. ． ． -4.3703 entrance pupil diameter. ． ． ． 0.5000 rear focal length. ． ． -1.5310 Entrance pupil distance. ． ． ． 0.0000 front focal length. ． ． -0.4930 exit pupil diameter. ． ． ． 4.4328 F / number. ． ． ． ． ． -8.7407 Ejection pupil distance. ． -40.2763 half angle of view. ． ． ． ． ． 0.0000 Paraxial image height. ． ． ． ． ． ． 0.0000 image distance. ． ． ． ． ． 2.8374 Paraxial image distance. ． ． ． ． ． 2.8374 full length. ． ． ． ． ． ． 20.1780 Lens reference wavelength (mm) 720.0 Reduction rate. ． ． ． ． ． -0.9996 all tracks. ． ． ． ． 27.8806 Finite F / number. ． ． ． -9.7390 object distance. ． ． ． ． ． ． 4.8652

In the above example, lens array 28 was constructed from a single row of gradient index optical fibers. The radiometric rate of the system was therefore limited. It is desirable to utilize a two-row lens array, which is common in most commercial copiers that utilize a gradient lens array as the imaging member. However, using a conventional two-row array in the optics described above, two of each projected radiator output is used.
The two images are reduced, but discontinuous. A second embodiment of the optical system of FIG. 2 is shown in FIG. 3, where the lens array 28 is an array of two rows of gradient index optical fibers 28A ', 28B'. 28 '
Has been replaced by. According to a second aspect of the invention,
The rows 28A ', 28B' are formed at suitable angles to each other and are inclined with respect to the vertical axis between the object plane (radiator row) and the image plane (photoreceptor surface). Row 28
A ', 28B' remain parallel to each other in the process-orthogonal direction, but form an appropriate angle in the process-direction. Therefore, the reduction in spot size only occurs in one direction (process direction). The tilting of one row relative to the other eliminates discontinuous imaging of the radiator in the process direction.

[Brief description of drawings]

FIG. 1 is a side view of an image bar print system incorporating the optical system of the present invention.

FIG. 2 shows the trajectory of a single ray through the optical system, FIG.
It is a figure of the optical system shown in FIG.

FIG. 3 is a diagram showing a second embodiment of the optical system of FIG.

[Explanation of symbols]

10 printer, 12 photoconductor drum, 14 corotron, 15 exposure mechanism, 16 developing mechanism, 18 transfer mechanism, 20 copy paper, 22 image writing bar,
24 light emitting diode, 25 optical imaging system, 26 image signal source, 27 input line, 2
8 gradient index lens array, 30 cylindrical lenses, 3
2 cylindrical lens

Continuation of front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location H04N 1/036 A 9070-5C (72) Inventor Thomas J. Hammond New York, USA 14526 Penfield Henderson Drive 108 ( 72) Inventor James Dee-Leeds New York, USA 14534 Pittsford Palmyra Road 5880

Claims (1)

[Claims] 1. An image bar comprising a linear array of light emitting elements, a photoconductive member adapted to move in a process direction through an exposure mechanism, and an image signal source connected to said image bar. Means for addressing the image bar to generate a light output representative of the input of the signal source; and in cooperation with the image bar for the photoconductive member in a process orthogonal direction. An image bar printer including an optical system for forming a line image, wherein the line image is formed from a combined focused output spot corresponding to the output of the light emitting element. An image bar printer wherein the optical system includes: a linear gradient index lens array disposed between the image bar and the photoconductive member; A first cylindrical lens disposed between the image bar and the lens array; and a second cylindrical lens disposed between the lens array and the photoconductive member;
The optical system is characterized by the focused spot in the process-orthogonal direction having a size larger than the spot size in the process-direction.
It is supposed to form an image.