JPH01179176A - Image forming device - Google Patents

Abstract

PURPOSE:To form the image of high luminance and high resolution with a simple constitution by making an image-formation magnification in an arraying direction in a line-shaped exposure means different from that in a direction perpendicular to the array. CONSTITUTION:A lens array 6 and a bar lens 7 are arranged between an LED array 3 mounted on the substrate 2 of an LED array head 1 and a photosensitive drum 5. The lens array 6 is constituted in array by using many refraction index distribution type lenses and the image-formation magnification is made same in (x) and (y) directions. The bar lens 7 forms the image on a photosensitive drum 5 by unmagnifying the optical image of the LED array 3 in the arraying direction (x direction) of light emitting elements 30-32, etc., and by reducing the optical image of the array 3 in the direction (y direction) perpendicular to the arraying direction. Even if the dimensions of the respective light emitting elements are made larger in the (y) direction in order to improve bit density, the resolution in the (y) direction at the time of forming the image is not spoiled. Therefore, the image of high density can be formed by using the light emitting element whose luminance is high.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image forming apparatus that arranges a plurality of micro optical elements and projects an optical image thereof onto a photoreceptor to form a desired image.

(Prior art) Conventionally, a plurality of minute optical elements such as LEDs and liquid crystals are arranged, and a photoreceptor such as a photoreceptor drum is exposed by controlling the blinking of each optical element to form a photoreceptor on the photoreceptor. 2. Description of the Related Art Image forming apparatuses that form a desired image by developing a latent image are known. An optical image obtained by blinking an optical element called a solid-state scanner is usually focused on a photoreceptor at the same magnification using an array lens or the like.

(Problems to be Solved by the Invention) Incidentally, in recent years, higher density recording has been required for such image forming apparatuses, and for this purpose, each element of the solid-state scanner ( ,11,/'
)・σ Must be so fine 0 For example, in an LED printer that uses LED light emitting elements as a light source, each element of each LED head is arranged at intervals of approximately 85 μm in order to form an image at a recording density of 300 dpi. . In order to form images at a higher recording density of 400 dpi with the same printer, each element must be approximately 64 mm thick.
It is necessary to arrange them at intervals of . As the recording density increases, each element must be brought closer to each other, so the light-emitting element of each element becomes smaller, and as a result, the amount of light emitted by each element becomes smaller. This has the problem that the load on the element increases.

Therefore, in order to improve the recording density without reducing the arrangement density of each element, a means has been devised for arranging light emitting elements in a plurality of arrays, as shown in FIG. That is, this means includes each light-emitting element 20 in the first row (101°, 102, 103, 104, etc.) and each light-emitting element 20 in the second row arranged with a predetermined distance.
1°202, 203, 204, . . . are arranged so that they do not overlap with each other in the photoreceptor moving direction a.

However, in such a conventional example, the light emitting element groups lot, 102... in the first row are separated by a distance from the light emitting element groups 201, 202... in the second row. When performing exposure by controlling each light emitting element group, it is necessary to turn on the lights at slightly different times so as to synchronize with the movement of the photoreceptor. Therefore, a special circuit including a memory for temporarily storing the image information is required, which increases the complexity and cost of the device.

On the other hand, in order to compensate for the reduction in brightness of each element due to the increased density of the element arrangement, the length of each element 301, 302, 303, 304, etc. in the direction perpendicular to the arrangement direction is increased as shown in Figure 6. Measures have also been devised.

However, when a photoreceptor is exposed using this method, although it is possible to improve the recording density in the element arrangement direction, the resolution in the direction perpendicular to that direction is reduced.゜302・
..., when the photoreceptor moves in the direction of arrow a, its length in the vertical direction is larger than in the direction in which the light emitting elements are arranged, so there is a problem in that the resolution in the direction of arrow a decreases. Ta.

Therefore, the present invention has been made to solve the problem of 1':=na2J'L of the above-mentioned prior art, and its purpose is to provide a high brightness in any direction while having a simple configuration. Another object of the present invention is to provide an inexpensive image forming apparatus capable of forming images with high resolution.

(Means for Solving the Problem) In order to achieve the above object, in the present invention, the exposure means arranged in a row are driven according to the image to be formed, and the light image is focused on the image carrier. An image forming apparatus that forms an image by imaging is provided with an imaging means that forms an image so that the imaging magnification in the array direction of the exposure means is different from the imaging magnification in a direction perpendicular to the array direction.

(Function) In the present invention having the above configuration, the optical images of the exposure means arranged in a row are formed on the image carrier at different magnifications in the arrangement direction and the direction perpendicular to the arrangement direction. . Therefore, in order to improve recording density and brightness, when light images of exposure means with different dimensions in the array direction and in a direction perpendicular to the array direction are formed on the image carrier, the light images have predetermined dimensions in each of the two directions. You can get the image. Furthermore, if the optical image of the exposure means that is long in the direction perpendicular to the arrangement direction is formed in a smaller size than the arrangement direction of the exposure means in that direction, loss of resolution in the direction perpendicular to the arrangement direction can be prevented. .

(Example) The present invention will be explained below based on illustrated embodiments.

1 to 3 show a first embodiment of an image forming apparatus according to the present invention, and FIGS. 1(a) and 1(b) show the main parts thereof, and l is an LED array head. , a substrate 2, an LED array 3 mounted on the substrate 2, and the LED
The drive circuit 4 includes a drive circuit 4 that drives the array 3.

The LED array head 1 includes a photosensitive drum 5 as an image carrier.
The LED array 3 on the substrate 2 is provided with light emitting elements 30, 31, 32, etc. as exposure means, as shown in FIG. 1(b). That is, each of the light emitting elements 30, 31, 32, etc. is a minute element whose length in the X direction, that is, in the arrangement direction, is dl = 604 m, and the length in the y direction, that is, in the rotation direction of the photosensitive drum 5, is d2 = 100 pm. , and the spacing between adjacent elements is P = 83.5p
They are arranged in a line so that the number is m. The light emitting elements 30, 31, 32, . . . are independently driven by the drive circuit 4 based on desired image information, and emit image light by blinking.

Between the LED array head l and the photosensitive drum 5, an LED
A lens array 6 for forming the optical image formed by the D array 3 onto the photosensitive drum 5 and a rod lens 5 as an image forming means are arranged in this order from the LED array head l toward the photosensitive drum 5. It is. The lens array 6 uses a large number of gradient index lenses such as self-occurring lenses (trade name of Nippon Sheet Glass Co., Ltd.) and is configured in an array, and its imaging magnification is! + It is the same in all 7 directions.

The length of the lens array 6 is approximately equal to the length of the LED array 3. The rod lens 7 is an optical lens having approximately the same length as the lens array 6, and has a convex surface in the X direction on the surface facing the lens array 6. It forms. Therefore, this rod lens 7 is moved in the X direction, that is, the light emitting element 30. The image light is guided onto the photosensitive drum 5 at the same magnification in the array X direction of the array. The image will be formed on top.

A developing device, a secondary and transfer charger, a fixing device, a cleaner, etc. (not shown) are provided around the photosensitive drum 5, and the latent image formed on the surface of the photosensitive drum 5 is processed by a known electrophotographic process. The image is visualized and transferred to a transfer material.

In this embodiment having the above configuration, in order to form an image, the light image of the LED array 3 is formed on the photosensitive drum 5 in a primary manner.

FIGS. 2(a) and 2(b) show the imaging state of the light image of the LED array 3, in which FIG. 2(a) is in the X direction and FIG. 2(b) is in the X direction.
In FIG. 2(a), the LED
Each light emitting element 30, 31, 32...of the array 3 has light f&
first passes through the lens array 6, and then is guided onto the photosensitive drum 5 by the rod lens 7, and the image 5 is formed on the drum 5.
0a, 51a.

The image is formed as 52a... Here, the rod lens 7 is
Each light emitting element 30.3 has no refractive power in the direction.
The optical images of 1.32, . . . are formed at the same magnification on the photosensitive drum 5 only by the lens array 6.

On the other hand, in the second UgJ (h), the image in the X direction, that is, the direction perpendicular to the arrangement direction of the light emitting elements 30, 31, 32, etc., passes through the lens array 6 at the same magnification, and then changes its refractive power in the X direction. An image 50b is formed on the photosensitive drum 5 by a rod lens 7 having a
51b, 51c... are reduced and imaged. In the present embodiment, the imaging magnification in the X direction is approximately 200 nm.

As described above, in this embodiment, the light emitting elements 30,
By adopting a configuration in which the rod lens 7 is used to form a reduced image in the X direction perpendicular to the arrangement direction X of 31, 32..., the dimensions of each light emitting element 30... can be changed in the Even if it is formed large, the resolution in the X direction during image formation will not be impaired.

Therefore, a light emitting element with high brightness can be used in a device using a solid-state scanner with high recording density.
This has the effect that high-density image formation can be performed in both the x and y directions without providing a plurality of LED arrays, a synchronization memory circuit, and the like.

Furthermore, since the image formed in the X direction perpendicular to the direction in which one light emitting element is arranged becomes smaller, when each light emitting element 30, 31, etc. is driven by pulse width modulation, the linearity and dynamic range of the modulation must be increased. It also has the effect of being able to.

FIG. 3 shows a second embodiment of the image forming apparatus according to the present invention. In the figure, the same parts as in the first embodiment are given the same reference numerals. In this embodiment, the light emitted from the light source 11 such as a fluorescent lamp is
The light is focused onto a liquid crystal shutter array 13 by a condenser lens 12 provided in front of the . Minute liquid crystal shutters are arranged on the liquid crystal shutter array 13 in the X direction in the figure, and each liquid crystal element is driven according to an image signal from a control circuit (not shown) to allow light from the light source 11 to pass through. Here, regarding each liquid crystal element.

Similar to the shape of each light emitting element 30, 31... in the first embodiment, the dimension in the direction (y direction) perpendicular to the arrangement direction (X direction) is set larger than in the arrangement direction (X direction). Even when arranged in high density, a large amount of light can be obtained as image light.

The light passing through the liquid crystal shutter array 13 is
An image is formed on the photosensitive drum 5 by an imaging lens 14 made of a toric lens disposed between the photosensitive drum 3 and the photosensitive drum 5. The imaging magnification of the imaging lens 14 is set to form an image at the same magnification in the X direction and at reduced magnification in the Y direction, similarly to the lens array 6. Therefore, even in this embodiment, which uses the array 13 in which liquid crystal elements are arranged in the y direction, which is more open than the x direction, the y
Since the irradiation width does not expand in the y-direction, it is possible to project an optical image with high brightness without impairing resolution in the y-direction. Since the other configurations and functions are the same as those of the first embodiment, their explanations will be omitted.

FIG. 4 shows a third embodiment of the image forming apparatus according to the present invention. In the figure, the same parts as in the second embodiment are given the same reference numerals. In this embodiment, the image light that has passed through the liquid crystal shutter array 13 is transferred to the photosensitive drum by the imaging lens 20. Although it is imaged on 21,
Since the imaging lens 20 has refractive power not only in the y direction but also in the X direction, the optical image formed by the liquid crystal shutter 7 ray 13 is reduced in both the
image on top. Therefore, on the photosensitive drum 21,
An image is formed by dots having a smaller pitch than the pitch between each element of the liquid crystal shutter array 13. in this case,
Regarding the y direction perpendicular to the element arrangement direction X of the liquid crystal shutter array 13, a reduced image is formed by the imaging lens 20, and the imaging lens 20 is used such that the imaging magnification is smaller than that in the X direction. Therefore, in this example,
It is possible to form an image using dots smaller than the dimensions of each element of the liquid crystal shutter array 13, and there is an effect that a higher density image can be formed. The other configurations and operations are the same as those of the second embodiment, so their explanation will be omitted.

(Effects of the Invention) In the present invention having the above configuration and operation, the optical images of the exposure means arranged in a row are transferred to the image carrier at different magnifications in the arrangement direction and the direction perpendicular to the arrangement direction. By focusing the image upwardly, it is possible to form a high-luminance, high-density image using exposure means having different dimensions in the arrangement direction and the direction perpendicular to the arrangement direction. Therefore, it is not necessary to provide exposure means for a plurality of lines in order to improve the recording density or to control and drive each line, thereby simplifying the apparatus and reducing costs.

In addition, the optical image of the exposure means that is long in the direction perpendicular to the arrangement direction,
If the image is formed in a smaller size than the array direction of the exposure means in this direction, the resolution in the direction perpendicular to the array direction is not impaired.
The effect is that high-density image formation can be performed in any direction.

[Brief explanation of the drawing]

1(a) and 1(b) show a first embodiment of an image forming apparatus according to the present invention, and FIG. 1(a) is a perspective view showing a schematic configuration of the main part of the embodiment; (b) is an enlarged front view showing the arrangement of the light emitting elements, and FIGS. 2(a) and (b) show the state of optical image formation of the LED array.
(b) is an explanatory diagram showing the imaging state in the y direction, FIG. 3 is a perspective view showing a schematic configuration of main parts of the second embodiment of the image forming apparatus according to the present invention, and FIG. FIG. 5 is an enlarged front view showing an example of the arrangement of light emitting elements in the conventional device; FIG. FIG. 7 is an enlarged front view showing another example of the element. Explanation of symbols l...LED array head 3...LED array 30.31.32...Light emitting element (exposure means) 5...
Photosensitive drum (image carrier) 7... Rod lens (imaging means)

Claims (2)

[Claims] (1) In an image forming apparatus that forms an image by driving exposure means arranged in a row according to an image to be formed and forming the light image on an image carrier, the arrangement direction of the exposure means 1. An image forming apparatus comprising: an image forming means for forming an image such that an image forming magnification in a direction different from an image forming magnification in a direction perpendicular to the arrangement direction is provided. (2) The imaging means has an imaging magnification in a direction perpendicular to the arrangement direction of the exposure means that is smaller than an imaging magnification in the arrangement direction of the exposure means. Image forming device.