JPH09187991A - Exposure device and image forming device using the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce loss of light energy which is generated from an LED array. SOLUTION: A plurality of LED eliments 11a are provided on a surface of a substrate 10. While the light emissions of the LED elements are selectively controlled, a photosensitive body on a rotary drum 20 is exposed so as to form an electrostatic latent image. A micro lens 12a which collects the lights of the LED elements 11a of the substrate 10 to the photosensitive body is directly attached to the substrate 10, so that loss of energy until the lights arrive at the photosensitive body is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for forming an image by an electrophotographic method and an image forming apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, laser light obtained from a laser light source is deflected and scanned by a scanning means such as a rotating polygon mirror to form an image on a photosensitive member on a rotating drum. A scanning type exposure apparatus that exposes this is widely used, but in recent years, an LED in which a plurality of light emitting diode (hereinafter, referred to as “LED”) elements that can selectively control light emission are linearly arranged. Exposure for forming an electrostatic latent image on the photoconductor on the rotary drum by arranging the array so as to face the photoconductor on the rotary drum and selectively controlling the light emission of the LED elements while rotating the rotary drum. A method was developed. This is because the light source can be arranged in the vicinity of the photoconductor and does not require a mechanical driving unit such as a motor for driving the rotating polygon mirror, and therefore greatly simplifies and downsizes the mechanism of the entire image forming apparatus. Expected to be useful.

FIG. 6 shows a conventional example of an exposure apparatus using such an LED array.
The LED array 110 in which 1 is arranged in the axial direction of the rotary drum 120 is opposed to the cylindrical surface 120a of the rotary drum 120, and the LED array 1 is rotated while rotating the rotary drum 120.
An erecting equal-magnification imaging optical system 130 arranged between the LED array 110 and the rotating drum 120
The light is focused on the photoconductor on the cylindrical surface 120a of the rotating drum 120. A known SELFOC lens or the like is generally used as the image forming optical system 130.

[0004]

However, according to the above conventional technique, as described above, the light generated from the LED array is imaged by the SELFOC lens or the like arranged between the LED array and the rotating drum. Since the light is condensed on the photoconductor by the optical system, most of the energy of the light generated from the LED array is lost in the atmosphere before reaching the SELFOC lens and the like, and a part of the light is SELFOC. There is an unsolved problem that the light generated from each LED element is not fully utilized because it is totally reflected on the surface of the lens or attenuated while passing through the SELFOC lens.

For example, when the lens diameter of the SELFOC lens is 1 mm and the pixel size is 300 dpi, each L
The ratio of the energy emitted from the ED element to the photoreceptor is 75% by the time it reaches the photoreceptor, and the energy loss when the light is reflected at the boundary between the SELFOC lens and the air is 4.3. %, And the energy of light reaching the photoconductor has been found to be attenuated to the order of 20% of the emission energy of each LED element.

As described above, nearly 80% of the energy of the light generated from the LED element is wasted, so that it is necessary to increase the amount of light emitted from the LED element and to extend the exposure time.
As a result, the power consumption of the LED array increases, and the time required for printing or the like also increases, which causes inconvenience.

The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and reduces the energy loss until the light generated from the LED array reaches the photoconductor, thereby reducing the power consumption. An object of the present invention is to provide an exposure apparatus that can reduce the consumption amount and can significantly reduce the exposure time, and an image forming apparatus using the exposure apparatus.

[0008]

In order to achieve the above-mentioned object, the exposure apparatus of the present invention condenses light generated from a light emitting diode array arranged on the surface of a substrate onto a photoconductor by an imaging optical system. And an exposure apparatus for exposing this,
The image forming optical system includes a microlens array including a plurality of microlenses directly attached to the surface of the substrate.

[0009]

The photosensitive member is exposed to form an electrostatic latent image while selectively controlling the light emission of a plurality of light emitting diode elements (LED elements) provided on the surface of the substrate. By directly attaching the microlens array that collects the light of each light emitting diode element to the photoconductor to the surface of the substrate, the distance between the light emitting diode array and the photoconductor is shortened, and the energy loss when the light passes through the atmosphere. To reduce.

Further, a part of the light is not totally reflected on the exit surface of the lens as in the case of using the SELFOC lens and the like, so that the energy loss when the light passes through the lens can be reduced.

By thus reducing the energy loss until the light generated from the light emitting diode array reaches the photoconductor, it can greatly contribute to the reduction of the power consumption and the exposure time.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an exposure apparatus according to an embodiment, in which an LED array 11 which is a light emitting diode array consisting of a plurality of light emitting diode elements (LED elements) 11a is formed on a surface of a substrate 10, and There is a laminated unit 1 in which a microlens array 12 composed of a plurality of microlenses 12a is laminated on top.

Each microlens 12a of the microlens array 12 has a lens diameter set based on the light emitting surface of the LED element 11a of the LED array 11, that is, the light emitting pixel, and the material thereof is SiO ₂ having a refractive index of 1.52. Then, it is a so-called direct mounting lens that is directly laminated on each LED element 11a on the surface of the substrate 10.

Each LED element 11a is selectively controlled to emit light by a current supplied from an electric circuit (not shown), and L
The light generated from the ED array 11 exposes the photoconductor on the rotary drum 20 to form an electrostatic latent image.

In the exposure apparatus according to the present embodiment, the image forming optical system for condensing the light generated from each LDE element on the photoconductor is composed of the microlenses directly attached to the substrate as described above. The light emitted from each LED element directly enters the microlens without being emitted to the atmosphere. Therefore, as compared with the case where a SELFOC lens or the like is provided between the substrate and the photoconductor as in the conventional example, the distance between the LED array and the photoconductor is significantly shortened, and the light generated from the LED element is emitted. It is possible to avoid significant attenuation before reaching the photoconductor.

Further, since the surface of each microlens is a curved surface, it is possible to greatly reduce the loss of light due to total reflection at the boundary surface between the microlens and the atmosphere. When the exit surface of the imaging optical system is a flat surface as in the conventional example, a large amount of light is totally reflected at the boundary surface with the atmosphere, which causes a large energy loss.

By using the microlens array directly attached to the substrate as described above, the energy loss of the light generated from the LED element is greatly reduced, and the exposure apparatus which consumes less power and requires shorter exposure time is realized. it can.

For example, in the conventional example, the light reaching the photoconductor is in the order of 20% of the light emission amount of each LED element,
It has been found that the use of the directly mounted microlens array according to this embodiment can improve the performance to 90%.

In the manufacturing process of each LED array, the amount of emitted light often varies among pixels. Such a variation in the amount of emitted light is about ± 20% at maximum, which is one of the causes of the occurrence of remarkable exposure unevenness on the photoconductor.

Therefore, it is preferable to use photochromic glass as the material of the microlens array so that the transmittance of each microlens changes with the amount of incident light. Photochromic glass is a dispersion of microcrystals in glass. Since the size of the microcrystals is less than a dozen nm, light scattering by the microcrystals is usually small and therefore transparent, but the incident light Coloring occurs as the light quantity changes, and the transmittance decreases as shown in FIG. By using the photochromic glass having such characteristics for the microlens, the variation in the amount of light emission of each LED element, which is a maximum of ± 20%, is reduced to ± 5% or less on the surface of the rotating drum, and the density unevenness is large. It is possible to realize high image quality even in a halftone image or the like.

FIG. 3 illustrates an image forming apparatus A using the exposure apparatus according to this embodiment. Light from the LED array 11 is rotated by a rotary lens via a microlens 12a directly attached to each LED element 11a. An image is formed on the photoreceptor on 20. The photoconductor is previously charged by the charging means 21 and is exposed by the light passing through the microlens 12a to form an electrostatic latent image. This electrostatic latent image is developed by the developing means 2.
The image is visualized by 2, and then transferred onto the recording paper by the transfer unit 23 and fixed by the fixing unit 24. Subsequently, the photoconductor is cleaned by the cleaning unit 25.

By using the exposure apparatus having the microlenses directly attached to each LED element in this way, L
The amount of light reaching the photoconductor from the ED element increases. As a result, in addition to being able to increase the printing speed than before,
By making the current flowing through the LED array small, it is possible to greatly contribute to the reduction of the heat generation of the LED element, the extension of the life of the LED element and the reduction of the power consumption.

FIG. 4 shows a printer for performing two-color printing using the image forming apparatus according to this embodiment. This is because a pair of image forming apparatuses B ₁ and B ₂ similar to the image forming apparatus A shown in FIG. 3 are arranged in series on a conveyor that conveys the recording paper P, and one of the image forming apparatuses B ₁ is black. Image of,
An image of another color is formed by the other image forming apparatus B ₂ .

Further, FIG. 5 shows a printer for performing full-color printing using the image forming apparatus according to this embodiment. This is a recording paper in which _four image forming apparatuses C _{1 to} C ₄ similar to the image forming apparatus A shown in FIG. 3 are arranged in series to form images of cyan, magenta, yellow, and black colors. Print over P.

In two-color printing or full-color printing, it is important to avoid the occurrence of so-called color shift due to the shift of the images formed by the exposure devices. The exposure apparatus including the laminated unit to which the microlenses are directly attached according to the present embodiment significantly shortens the length of the optical path until the light generated from each LED element reaches the photoconductor, and causes the trouble such as the color shift. There is a remarkable advantage that can easily be solved. Further, since all the exposure apparatuses are significantly downsized and labor is saved, it is possible to greatly promote downsizing, labor saving and speedup, especially for a full color printer or the like.

[0027]

Since the present invention is configured as described above, it has the following effects.

The energy loss until the light generated from the LED array reaches the photoconductor is reduced, which can greatly contribute to the reduction of the power consumption of the exposure apparatus and the reduction of the exposure time.
By using such an exposure apparatus, labor saving and speeding up of the image forming apparatus can be greatly promoted.

[Brief description of the drawings]

FIG. 1 shows an exposure apparatus according to an embodiment, (a)
Is a sectional view thereof, and (b) is a plan view.

FIG. 2 is a graph showing the transmittance of photochromic glass.

FIG. 3 is a diagram illustrating an entire image forming apparatus.

FIG. 4 is a diagram illustrating a two-color molding printer.

FIG. 5 is a diagram illustrating a full-color printer.

FIG. 6 is a perspective view showing an exposure apparatus according to a conventional example.

[Explanation of symbols]

 1 Laminated Unit 10 Substrate 11 LED Array 11a LED Element 12 Microlens Array 12a Microlens 20 Rotating Drum

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 1/036

Claims (3)

[Claims] 1. An exposure apparatus which exposes the light generated by a light-emitting diode array disposed on a surface of a substrate to a photosensitive body by an imaging optical system and exposing the photosensitive body. An exposure apparatus comprising a microlens array including a plurality of microlenses directly attached to the surface of the substrate. 2. The exposure apparatus according to claim 1, wherein the material of the microlens array is photochromic glass. 3. An image forming apparatus having the exposure apparatus according to claim 1 or 2, and a developing unit for developing an electrostatic latent image on a photoconductor.