JP2001091877A - Exposure head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure head capable of suppressing the deterioration of image quality such as the uneven density of an image formed by using plural light beams. SOLUTION: On the exit side of an LED chip 36 with plural LED elements 361 to 3631, a micro lens array 100 which is constituted by arranging micro lenses 1001 to 10031 as many as the LED elements at prescribed intervals in an array state is arranged. The micro lens array 100 functions as a lens for an illuminating system for limiting the diffusion of the light beam emitted from the LED chip 36, and a theoretical object plane 102 when the light beam is image-formed on an exposure drum 14 is illuminated with the light beam having homogeneous shape and profile through the micro lens array 100. By such the constitution, the light beams emitted from the LED elements 361 to 3631 are projected with the homogeneous shape and light distribution to the irradiation areas 1021 to 10231 through the independently functioning micro lenses 1001 to 10031.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure head, and more particularly to an exposure head which projects a light beam from a light source suitable for use in an image exposure apparatus or an image recording apparatus by a projection lens.

[0002]

2. Description of the Related Art A digital exposure type exposure apparatus that exposes a light beam modulated by image data to record an image is known. In order to shorten a recording time, a plurality of light beams are substantially emitted. Many optical systems using a plurality of light beams for simultaneous exposure have been proposed. In this case, when an optical system is configured by obtaining a plurality of light beams using a plurality of light sources, variations between pixels due to positional errors of the light sources and non-uniform light spot shapes due to variations in the light sources and assembly errors. Invited,
Density unevenness and the like were generated in the obtained image, and the quality of the image was reduced.

[0003] In order to solve this problem, there is known a technique in which an aperture is provided on an emission side of a light source to make the shape of a light spot uniform, or a diffuser plate is provided to make the light amount uniform (Japanese Patent No. 2771932, Japanese Patent Publication No. See JP-A-5-503169). In this technique, a plurality of apertures having a constant pitch and a constant hole diameter are arranged on each emission side of a plurality of light sources. These apertures are provided at conjugate positions with respect to the position of the photosensitive material. By irradiating these apertures with a collimated light beam from a light source and by providing a diffuser near the apertures, the shape and profile are made uniform. The irradiated light beam can be applied to the photosensitive material.

[0004]

However, by simply providing an aperture or a diffusion plate as in the prior art, the shape of each spot can be homogenized to some extent, but the diffusion locality of the diffusion plate is reduced. Therefore, fine homogenization is inappropriate.

In addition, since it is difficult to make the light source, the aperture, and the diffusion plate adhere to each other, a position error occurs depending on the distance.

Further, when a diffusion plate is used, when the degree of diffusion is low, in the elements other than the optical axis of the imaging lens, an LED image and a secondary light source image are imaged on the diffusion plate with a distance. In addition, shape variations are induced.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure head capable of suppressing a decrease in image quality such as density unevenness in an image formed by using a plurality of light beams in consideration of the above fact.

[0008]

In order to achieve the above object, the present invention provides an exposure head for projecting a light beam from a light source in an exposure apparatus for exposing an image by a projection lens, wherein a plurality of light emitting elements are arranged. A light source and a lens array having lenses corresponding to the number of the plurality of light emitting elements are provided.

When an exposure head projects a light beam from a light source using a plurality of light-emitting elements, the plurality of light-emitting elements correspond to the number of the plurality of light-emitting elements on the emission side of the light source arranged, for example, toward one side. A lens array having a lens to be mounted is provided. As this lens array, a microlens array in which a plurality of microlenses are arranged in an array can be used. Thereby, even if the light source has a variation, the light beam from the light source can be made uniform by each lens of the lens array. In addition, the light diffusivity on the emission side of the lens array can be improved by the light condensing property of the lens.

In the lens array, the shape of the entrance surface and the exit surface of each lens can be made convex. Each lens of this lens array can be constituted by one lens that functions as a lens obtained by combining two groups of lenses by increasing the distance between the entrance surface and the exit surface. There is a convex lens as a lens in which the shapes of the entrance surface and the exit surface are convex. By making the interface shape of the lens a convex shape, for example, a convex lens, each lens can be directed along the optical axis in the direction of condensing the light beam, and the light beam can be condensed.

In addition, a plurality of lens arrays arranged in the optical axis direction can be used as the lens array. That is, the light beam emitted from the light source can be dispersed and condensed by the plurality of lenses. For example, 2
When one lens array is arranged in the optical axis direction, a structure corresponding to an optical system of a so-called illumination system can be obtained when one lens is viewed. The light source side corresponds to a collector lens, and the exposure side corresponds to a condenser lens. By arranging in this way, it is possible to facilitate the optical design of the light beam from the light source.

As each lens of the lens array, a lens having a positive power, that is, a convex lens can be used.

[0013] The exposure head according to the present invention may further comprise opening means in which openings corresponding to the number of the plurality of light emitting elements are formed at regular intervals. The light beam transmitted through the lens can be restricted by the opening of the opening means, and transmission of a light beam other than the optical axis of the lens can be suppressed.

The size of the opening of the opening means may be smaller than the effective diameter of the lens. By doing so, it is possible to effectively limit only the light beam transmitted through the lens.

The opening means may be provided between the entrance surface and the exit surface of each lens. As a result, only the light beam transmitted between the entrance surface and the exit surface of each lens can be restricted, and only the aperture and the transmitted light beam can be emitted.

The exposure head according to the present invention may further comprise a diffusing means for diffusing the light beam emitted from the lens array. The light beam emitted from the lens array can be efficiently diffused by the diffusing means.

[0017] The lens array may include lenses corresponding to an even number increased from the number of the plurality of light emitting elements. For example, the same number of lenses can be provided on both sides of a plurality of light emitting elements. By doing so, the incidence of the light beams from the light sources adjacent to each other as viewed from one lens optical axis becomes the same state for all the lenses, and the obtained light beam state becomes uniform for each light source. .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. This embodiment is an LE
The present invention is applied to an image forming apparatus that forms an image by exposure with a light beam from D.

An image forming apparatus 54 having the exposure unit 10 according to the embodiment of the present invention will be described. FIG. 1 shows a schematic configuration of an image forming apparatus 54 including an exposure unit 10 according to an embodiment of the present invention, and FIG. 2 shows a schematic configuration of the exposure unit 10 according to the embodiment of the present invention. It is shown.

As shown in FIG. 1, the photosensitive material 40 wound around a supply reel 60 is set in a photosensitive material magazine 58 disposed below a housing 56 of the image forming apparatus 54. The supply reel 60 is rotated by driving means (not shown) to unwind the photosensitive material 40. The front end of the photosensitive material 40 is a photosensitive material magazine 5
8 is nipped by a pull-out roller 62 provided at the mounting opening 8. The pull-out roller 62 is used to drive the photosensitive material 4 under predetermined conditions.
0 is pulled out and sent to the guide plate 64, or
A buffer (indicated by a two-dot chain line) is formed under predetermined conditions.

The photosensitive material 40 that has passed through the guide plate 64 is
The image is wound around the exposure drum 14 and an image is exposed by a scanning head 28 of the exposure unit 10 described in detail later. The photosensitive material 40 on which the image has been exposed is supported on the support 65 and the pressure plate 6.
6, and water is applied by a water-absorbing application member 70 (such as a sponge) provided in the application tank 68. The photosensitive material 40 to which water has been applied is wound around the heat drum 72 having a built-in halogen lamp at a constant pressure by tension rollers 74 and 76. The wound photosensitive material 40 is superposed from above on an image receiving paper 78 while being heated, and the image is transferred. The photosensitive material 40 to which the image has been transferred is taken up on a waste reel 80. In this way, the supply reel 6 is cut without cutting the photosensitive material 40.
0 to the waste reel 80, the photosensitive material 40
The sheet itself functions as a timing belt for applying a constant pressure to the image receiving paper 78.

On the other hand, an image receiving paper 78 wound around a supply reel 84 is set in a receiving material magazine 82 disposed above the housing 56. The image receiving paper 78 is pulled out by a nip roller 86 and cut to a predetermined length.
Is guided by the conveying roller 90 and the guide plate 92, and is wound around the heat drum 72 while being superposed on the photosensitive material 40. Then, the image receiving paper 78 on which the image has been transferred from the photosensitive material 40 is peeled off from the heat drum 72 by a peeling claw (not shown), guided by the transport roller 94 and the guide plate 96, and reaches the tray 98.

Next, the exposure unit 10 according to the embodiment of the present invention and its peripheral portion will be described. As shown in FIG.
The exposing unit 10 supports both ends of an exposing drum 14 around which a photosensitive material is wound around a rotatable rotating shaft 12. The exposure drum 14 has a cylindrical shape, and the exposure surface has a constant curvature about the rotation axis 12. Further, two shafts 16 and 18 are disposed on the upper left side of the exposure drum 14 in parallel with the rotating shaft 12. Support holes 24 and 26 penetrating the support blocks 20 and 22 are inserted into the shafts 16 and 18, and the shafts 16 and 18 are
You can slide along. Note that two support blocks 20 and one support block 22 are provided on the exposure drum 14 side, and three support blocks 20 constitute a plane.

As shown in FIG. 2, the support blocks 20, 2
2, a casing 30 of the scanning head 28 is fixed. Inside the bottom plate 32 of the casing 30, three LED chips 36 of RGB which are turned on by a signal from a controller 34 in which an image signal is stored are arranged. Have been. Three LED chips 36 are arranged in the main scanning direction of the exposure head 28, and each chip has 31 elements in the sub-scanning direction.

Although the details will be described later, a slit plate for limiting the spread of the light beam emitted from the LED chip 36 or for diffusing the light beam can be included on the light emitting surface side of the LED chip 36. A light source unit 38 is provided.
An imaging lens 42 is arranged inside the light source unit 38. The imaging lens 42 includes a plurality of lenses and an aperture, and functions to collect light from the LED chip 36 and form an image on the photosensitive material 40 wound around the exposure drum 14. Plays. The focus is automatically adjusted by an auto-focus mechanism (not shown).

On the other hand, a connecting plate 44 is mounted on the outer surface of the bottom plate 32. An endless timing belt 46 is fixed to the connecting plate 44. Timing belt 46
Are wound around sprockets 48 and 50 provided near both ends of the shafts 16 and 18, respectively. The shaft of the sprocket 48 is a drive shaft 48A of the speed reducer.
The rotational force of the stepping motor 52 accompanying forward and reverse rotation of the drive shaft 48A is applied to the sprocket 48.
And the scanning head 28 reciprocates along the shafts 16, 18.

The driving of the stepping motor 52 is controlled by the controller 34, and is synchronized with the step driving of the photosensitive material 40. That is, in a state where the photosensitive material 40 is stepped and stopped, the stepping motor 52 rotates forward, and the scanning head 28 moves along the shafts 16 and 18 in the width direction (main scanning direction) of the photosensitive material 40. Then, after confirming the predetermined pulse, the stepping motor 52 is rotated in the reverse direction in a state where the photosensitive material 40 is stepped and stopped, so that the reciprocating main scanning is performed.

Next, the light source section 38 will be described. In the present embodiment, the light source unit 38 that can include a slit plate for limiting the spread of the light beam emitted from the LED chip 36 or for diffusing the light beam is provided. The light source unit 38 and the LED chip 36 are a light beam emission portion of the scanning head 28 of the exposure unit 10.

As shown in FIG. 3, the LED chip 36 includes a plurality (31 in this embodiment) of LED elements 36 ₁ to 36 ₁ .
36 ₃₁ are provided. A microlens array 100 is provided on the emission side of the LED chip 36. The microlens array 100 includes the microlenses 1 of the number (31) of the LED elements provided in the LED chip 36.
00 _{1-100 31} are arranged in an array at regular intervals. Each of the micro lenses 100 _{1 to} 100 ₃₁ is configured to function as a convex lens having a convex shape of the incident surface and the exit surface.

This microlens array 100 is an LE
A lens of an illumination system that limits or spreads a light beam emitted from the D chip 36, and has a uniform shape on a theoretical object plane 102 when the light beam is imaged on the exposure drum 14. This is for illuminating a light beam having a uniform profile. In the example of FIG.
Light beams emitted from the LED elements 36 ₁ to 36 ₃₁ is a microlens 100 ₁ of the microlens array 100 to
The 100 _31, irradiation area 102 ₁ to an object plane 102
102 light beams uniform shape and uniform profile ₃₁ (light intensity distribution) is applied. That is, it is possible to arranged at regular intervals with each of the shape of the microlens 100 ₁ to 100 ₃₁ is capable of uniform, luminous flux obtained becomes substantially the same.

As a result, it is possible to form an image on the exposure drum 14 with light having a uniform shape and a light amount distribution by the microlenses arrayed at regular intervals of the microlens array 100. Therefore, even when using an LED chip in which the shape of each LED element is slightly uneven,
The position error can be eliminated and a light beam having a uniform light amount distribution can be obtained.

Here, one micro lens array 10
When the distance between the entrance surface and the exit surface of 0 (micro lens) is increased, it functions as a group lens combining two groups of lenses. The operation of the light source unit 38 in this case will be described.
For simplicity of description, one optical system, that is,
The LED element 36 ₁ microlens 100 _first light beam emitted from the irradiation area of the object plane 102 102 ₁
The point of irradiation will be described.

As shown in FIG.
₁ (microlens array 100) is the first lens 11
0 and the second lens 112 are configured to function.
Specifically, the front focal position of the second lens 112 is located at a position where a light source image is formed by the first lens 110 (a plane including the arrow 116 in FIG. 4 and orthogonal to the optical axis CL, hereinafter referred to as an opening surface A). Set to. In this case, the second of the object plane 102
The conjugate position of the lens 112 (a plane including the arrow 114 in FIG. 4 and orthogonal to the optical axis CL, hereinafter referred to as a field plane F) is a position on the emission side of the first lens and is not affected by the shape and position of the LED element.

[0034] This means that, LED element 36 ₁ and the opening surface A
Means that the field plane F and the object plane 102 are conjugate via the second lens 112. Further, it means that the aperture surface A is located at the front focal position of the second lens 112. It is preferable that the field of view F is located at the rear focal position of the first lens 110.

With this configuration, the LED element 3
The light beam emitted from 6 ₁ spreads over the field of view F after passing through the first lens 110, forms an image on the aperture surface A, passes through the second lens 112, and is a parallel light beam having a predetermined numerical aperture on the object plane 102. Becomes Thus, even if there is luminance unevenness LED element 36 ₁ can be homogeneously illuminate the entire object plane 102.

The luminous flux uniformly illuminating each irradiation area of the object plane 102 is converted by the imaging lens 42 into a photosensitive material 40.
In this way, the position error of the LED element can be eliminated, and an image spot formed by a light beam having a uniform light quantity distribution can be obtained. Quality deterioration can be suppressed.

Next, a second embodiment will be described. In this embodiment, since the configuration is the same as that of the above-described embodiment, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and the periphery of a different light source unit 38 will be described.

In the above embodiment, one microlens
As a group lens combining two groups of lenses
We have described a working configuration, but for a simple configuration,
It is preferable to combine multiple independent lenses
No. Therefore, in the present embodiment, as shown in FIG.
The microlens array 100 is connected to the first microlens
From the array 120 and the second microlens array 122
Constitute. In the example of FIG.₁~ 36₃₁Or
The light beam emitted from the microlens array 120
And a pair of micro lenses 120 of₁, 122₁~ 1
20₃₁, 122 ₃₁Irradiates the object plane 102 with the irradiation area 1
02₁~ 102₃₁Homogeneous shape and uniform profile
(Light quantity distribution) is irradiated.

With this configuration, the first micro lens array 120 and the second micro lens array 12
2 can be independently designed and manufactured, thereby increasing design flexibility.

Next, a third embodiment will be described. In this embodiment, since the configuration is the same as that of the above-described embodiment, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and the periphery of a different light source unit 38 will be described.

In the above-described embodiment, the configuration in which the spread of the light beam emitted from the LED chip 36 is limited or diffused by the microlens array has been described, but the light beam other than the optical axis is shielded. Is preferred. Therefore, in the present embodiment, as shown in FIG. 6, the aperture array 130 is provided between the microlens arrays 120 and 122 formed separately and independently.

[0042] The aperture array 130, LED elements 36 ₁ to 36 ₃₁ and the pair of microlenses in the microlens array 120 and 122 120 _1, 122 _1-12
0 _31, 122 has a number apertures of matching the ₃₁ number of, it is perforated at the same predetermined interval as the microlenses. The size of each opening of the aperture array 130 is smaller than the effective diameter of the microlens array.

The position of the aperture array 130 in the direction of the optical axis is preferably set near the opening plane A or the viewing plane F described with reference to FIG. The aperture in the field plane F corresponds to a so-called field stop, and when installed near the field plane F, the size of the aperture can limit the area of the light beam irradiated on the object plane 102. The aperture on the aperture surface A corresponds to a so-called aperture stop. When installed near the aperture surface A, the size of the aperture limits the light beam passing around the optical axis, that is, the object plane 1.
This is because it is possible to limit the total amount of the light beam irradiated to the light source 02. Note that a plurality of aperture arrays 130 may be provided.

As described above, in the present embodiment, since the aperture array as a so-called stop is provided, it is easy to make the light spot obtained on the object plane uniform in light amount distribution and uniform in shape. Become. For this reason, the light beam uniformly illuminated on each irradiation area of the object plane 102 is imaged on the photosensitive material 40 by the imaging lens 42, so that the light beam having a uniform light amount distribution is uniform on the photosensitive material 40. Imaging spots can be obtained at equal intervals, so that the resulting image does not have density unevenness or the like,
Image quality degradation can be suppressed.

In the present embodiment, the case where the aperture array 130 is provided between the two microlens arrays has been described. However, the present invention is not limited to this. 100 may be provided. Also, the aperture array 130 may be sandwiched between the microlens arrays 120 and 122 and joined together to form a single microlens array. Further, it may be provided on the emission side of the microlens array in order to limit the amount of light beam emitted from the microlens array.

As another means for blocking light beams other than the optical axis, a light-blocking member, for example, a light-blocking plate may be provided between adjacent microlenses in the microlens array.

Next, a fourth embodiment will be described. In this embodiment, since the configuration is the same as that of the above-described embodiment, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and the periphery of a different light source unit 38 will be described.

In the above embodiment, the configuration in which the spread of the light beam emitted from the LED chip 36 is limited or diffused by the micro lens array, and the case where the aperture is provided by the micro lens array has been described. In some cases, the diffusivity on the object plane 102 side is low. Therefore, in the present embodiment, as shown in FIG. 7, the diffusion plate 140 is provided at a position near the object plane 102.

With this configuration, the photosensitive material 40
A light spot with improved diffusivity can be obtained on the object plane 102, which is a position conjugate with the photosensitive surface. For this reason, a light beam that is more uniform in each irradiation area of the object plane 102 is imaged on the photosensitive material 40 by the imaging lens 42, so that the light beam is formed on the photosensitive material 40 by a light beam having a uniform light amount distribution. Since image spots can be obtained at equal intervals, it is possible to suppress deterioration in image quality without causing density unevenness or the like in the obtained image.

Next, a fifth embodiment will be described. In this embodiment, since the configuration is the same as that of the above-described embodiment, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and the periphery of a different light source unit 38 will be described.

In the above-described embodiment, the configuration in which the spread of the light beam emitted from the LED chip 36 is limited or diffused by the microlens array having the same number of microlenses as the number of LED elements of the LED chip 36. However, each microlens may be affected by a light beam from an adjacent LED element. That is,
LED element (LE) near the end of the light spot in the sub-scanning direction
That state of the light spot on the object plane 102 is irradiated with the light beam by the D elements 36 ₁ and 36 _{3 1)} is in a state different from the state of the light spot on the object plane 102 irradiated by another light beam is there. This is one whereas the microlens is a possibility that the light beams from the same number of LED elements on the left and right is incident, a microlens for example in the end, only from one lateral In microlens 120 ₁ LED element This is because there is a possibility that the light beam is incident only from the outside.

Therefore, in the present embodiment, as shown in FIG. 8, a microlens array 150 and an aperture array 152 are provided on the emission side of the LED chip 36. The microlens array 150 is provided with an even number of microlenses increased from the number of LED elements included in the LED chip 36. That is, the microlens array 150 includes the LED chip 3
The microlens 150 _{1-150 31} number of 6 matches the number of the LED elements (31) provided with microlenses 150A, 150 of the even number (two in this embodiment)
B are increased at each end, and are arranged in an array at regular intervals. Therefore, the number of microlenses 150A and 150B to which a light beam is not directly incident as an optical axis from the LED element of the LED chip 36 is increased at the end of the microlens array.

On the light beam output side of the micro lens array 150, similarly to the micro lens array, an aperture array having an even number of apertures increased from the number of LED elements provided in the LED chip 36. 152 are provided.

Here, the LED element 3 of the LED chip 36
Consider the 6 _1, 36 ₂ of the light beam. First, the LED element 36
While ₂ of the light beam is irradiated to the micro-lens 150 _{and second} charge, the light beam diverges, is also irradiated to the micro-lens 150 _1, 150 ₃ adjacent (not shown). Thus, the microlenses 150 ₁ by LED element 36 ₂ by the LED element 36 ₂ in the irradiated region 102 _2, 15
It is assumed that light beams are emitted from O ₂ and 150 ₃ (not shown). That is, it may be affected by light from the surroundings.

In this embodiment, the micro lens 150
The opening of the microlens 150A and the aperture array 152 is provided outside the unit ₁ . That is, a microlens in charge of the LED element and a structure corresponding to the opening are additionally provided. Therefore, the irradiation area 102 ₁ by the LED element 36 ₁ by LED element 36 ₁ that light beams from the microlens 0.99 _1, 0.99 _2, 150A is irradiated is assumed.

As described above, since the microlenses and the aperture are added on the assumption that the light from the periphery is affected even near the end of the LED element, a uniform shape and a uniform shape are obtained on the object plane. Each of the light beams of the profile (light amount distribution) is irradiated. That is, the LED elements 36 ₁ to 36 ₁
Each of the light beam from 6 ₃₁ is irradiated is homogenized onto the object plane.

[0057] By thus opening the microlens and the aperture array of the microlens array is an even number increases, since the respective light beams from the LED elements 36 ₁ to 36 ₃₁ is irradiated is homogenized onto the object plane A light beam that is more uniform in each irradiation area of the object plane 102 is imaged on the photosensitive material 40 by the imaging lens 42 to form an image spot on the photosensitive material 40 by a light beam having a uniform light amount distribution. Can be obtained at regular intervals, so that the resulting image does not have density unevenness or the like,
Image quality degradation can be suppressed.

In the above embodiment, the case where the exposure head writes an image has been described. However, the present invention can be applied to a scanner that reads an image.

Next, a sixth embodiment will be described. In this embodiment, since the configuration is the same as that of the above-described embodiment, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and the periphery of a different light source unit 38 will be described.

For example, in the first embodiment, the case where one microlens array 100 is arranged on the emission side of the LED chip 36 has been described, but in the present embodiment, FIG.
As shown in (2), two microlens arrays 100A and 100B are arranged side by side on the emission side of the LED chip 36.

The micro lens arrays 100A, 10A
0B has the same configuration, and the LE provided in the LED chip 36 is provided.
The number (31) of microlenses 100A ₁ to D elements
100A ₃₁ and micro lenses 100B _{1 to} 100B ₃₁ are arranged in an array at regular intervals.

In the example shown in FIG. 9, the LED elements 36 _{1 to} 36 ₃₁
The light beam emitted from the microlens array 100
A, and 100B microlens 100A ₁ to 100 of
A ₃₁ , 100B _{1 to} 100B ₃₁ , the object plane 102
The irradiation regions 102 ₁ to 102 ₃₁ are irradiated with a light beam having a uniform shape and a uniform profile (light amount distribution).

Further, with this configuration, each of the microlens arrays 100A and 100B can be independently designed and manufactured, and the degree of freedom in design can be increased.

Next, a seventh embodiment will be described. In this embodiment, since the configuration is the same as that of the above-described embodiment, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and the periphery of a different light source unit 38 will be described.

For example, in the above-described first embodiment, the case where one microlens array 100 is arranged on the emission side of the LED chip 36 has been described.
As shown in FIG. 0, two microlens arrays 100A and 100B are arranged side by side on the emission side of the LED chip 36, and an aperture array 130 is provided between the microlens arrays 100A and 100B.

[0066] The aperture array 130, LED elements 36 ₁ to 36 ₃₁ and the microlens array 100A and 100B microlens 100A ₁ ~100A _31,
Has a number openings that match the number of 100B ₁ ~100B _31, is perforated at the same predetermined interval as the microlenses. The size of each opening of the aperture array 130 is smaller than the effective diameter of the microlens array.

The position of the aperture array 130 in the direction of the optical axis is preferably set in the vicinity of the opening surface A or the viewing surface F described with reference to FIG. The aperture in the field plane F corresponds to a so-called field stop, and when installed near the field plane F, the size of the aperture can limit the area of the light beam irradiated on the object plane 102. The aperture on the aperture surface A corresponds to a so-called aperture stop. When installed near the aperture surface A, the size of the aperture limits the light beam passing around the optical axis, that is, the object plane 1.
This is because it is possible to limit the total amount of the light beam irradiated to the light source 02. Note that a plurality of aperture arrays 130 may be provided.

As described above, in the present embodiment, since the aperture array as a so-called stop is provided, it is easy to make the light spot obtained on the object plane uniform in light quantity distribution and uniform in shape. Become. For this reason, the light beam uniformly illuminated on each irradiation area of the object plane 102 is imaged on the photosensitive material 40 by the imaging lens 42, so that the light beam having a uniform light amount distribution is uniform on the photosensitive material 40. Imaging spots can be obtained at equal intervals, so that the resulting image does not have density unevenness or the like,
Image quality degradation can be suppressed.

In this embodiment, the case where the aperture array 130 is provided between the two microlens arrays has been described. However, the present invention is not limited to this. It may be provided inside each of 100A and 100B. Further, it may be provided on the emission side of the microlens array in order to limit the amount of light beam emitted from the microlens array.

As another means for blocking light beams other than the optical axis, a light-blocking member, for example, a light-blocking plate may be provided between adjacent microlenses in the microlens array.

Next, an eighth embodiment will be described. In this embodiment, since the configuration is the same as that of the above-described embodiment, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and the periphery of a different light source unit 38 will be described.

In the above embodiment, the LED chip 36
Has described the case where 31 elements are arranged in one row in the sub-scanning direction. However, in the present embodiment, as shown in FIG. A), 31 LED elements 36A _{1 to} 36A ₃₁ , 3
6B ₁ ~36B ₃₁ are arranged in two rows.

As shown in FIGS. 11B and 11C, on the emission side of the LED chip 36, microlens arrays 100A and 100B are arranged side by side in the main scanning direction (direction B in the figure). I have.

As shown in FIGS. 12A and 12C, the LED chip 36 is connected to two LED chips 36A and 36A.
6B, and arranged along the main scanning direction (direction B in the figure). As shown in FIG. 12B, the microlens array 100 is divided into 31 sub-scanning directions (direction A in the figure). microlens 100A ₁ ~100A _31, 100B ₁ ~10
0B ₃₁ may be used as the configuration of arranging two rows.

As shown in FIGS. 13A and 13C, the LED chip 36 is provided with 31 LED elements 36A _{1 to} 36A ₃₁ and 36B _{1 to} 3 in the sub-scanning direction (direction A in the drawing).
6B ₃₁ 36C ₁ ~36C ₃₁ a may be arranged three rows. In this case, as shown in FIG. 13 (B), similarly to the LED element, a microlens array 100, each 31 pieces of microlenses 100A ₁ in the sub-scanning direction ～100A _31, 10
0B ₁ ~100B _31, microlens 100C ₁ to 100
It may be configured to place the A ₃₁ 3 columns. Note that FIG.
In the examples of (A) and (B), the three rows of LED elements or microlenses are arranged so as to be shifted by a predetermined distance in the sub-scanning direction, but the arrangement is not limited thereto.

[0076] Further, as shown in FIG. 14 (B), the microlens array 100 may be a micro lens array 100X ₁ ~100X ₃₁ independent 31 of separation.

[0077]

As described above, according to the present invention, when a light beam from a light source is projected by using a plurality of light emitting elements, a plurality of light emitting elements are arranged on the emission side of the light source in which the plurality of light emitting elements are arranged. Since a lens array having lenses corresponding to the number of light sources is provided, even if the light source has a variation,
The light beam from the light source can be made uniform by each lens of the lens array, and the light diffusivity on the emission side of the lens array can be improved due to the light condensing property of the lens.
This has the effect.

Further, by using a plurality of lens arrays arranged in the direction of the optical axis as the lens array, the light beam emitted from the light source can be dispersed and condensed by a plurality of lenses. This has the effect that the optical design for the light beam can be made easier.

Further, by further providing opening means in which openings corresponding to the number of the plurality of light emitting elements are formed at regular intervals, it is possible to limit the light beam transmitted through the lens, and to control the light beam other than the optical axis of the lens. Transmission can be suppressed,
This has the effect.

Further, by further providing a diffusing means for diffusing the light beam emitted from the lens array, there is an effect that the light beam emitted from the lens array can be efficiently diffused.

By using a lens array having lenses corresponding to an even number increased from the number of the plurality of light emitting elements, all the lenses have the same light state, and the obtained light beam state is There is an effect that the light source becomes uniform.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus provided with an exposure unit according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an exposure unit having a scanning head according to the embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a light source unit in an exposure unit according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram illustrating a conceptual configuration of a light source unit in which the thickness of a microlens is increased.

FIG. 5 is a schematic configuration diagram illustrating a light source unit in an exposure unit according to a second embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a light source unit in an exposure unit according to a third embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing a light source unit in an exposure unit according to a fourth embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing a light source unit in an exposure unit according to a fifth embodiment of the present invention.

FIG. 9 is a schematic configuration diagram showing a light source unit in an exposure unit according to a sixth embodiment of the present invention.

FIG. 10 is a schematic configuration diagram showing a light source unit in an exposure unit according to a seventh embodiment of the present invention.

11A is a plan view of an LED chip of a light source unit in an exposure unit according to an eighth embodiment of the present invention, FIG. 11B is a plan view of a microlens array, and FIG. 11C is a plan view of FIG. It is the figure which looked at B) from the upper side.

12A is a plan view of an LED chip of a light source unit in an exposure unit according to an eighth embodiment of the present invention, FIG. 12B is a plan view of a microlens array, and FIG. 12C is a plan view of FIG. It is the figure which looked at B) from the upper side.

FIG. 13A is a plan view of an LED chip of a light source unit in an exposure unit according to an eighth embodiment of the present invention, FIG. 13B is a plan view of a microlens array, and FIG. 13C is a plan view of FIG. It is the figure which looked at B) from the upper side.

14A is a plan view of an LED chip of a light source unit in an exposure unit according to an eighth embodiment of the present invention, FIG. 14B is a plan view of a microlens array, and FIG. 14C is a plan view of FIG. It is the figure which looked at B) from the upper side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Exposure part 36 LED chip 38 Light source part 100 Micro lens array 130 Aperture array

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B41J 2/455 H04N 1/036 A G02B 3/00 B41J 3/21 L G03B 27/32 H04N 1/04 B H04N 1/036 1/04

Claims (9)

[Claims] 1. An exposure head for projecting a light beam from a light source in an exposure apparatus for exposing an image by a projection lens, comprising: a light source in which a plurality of light emitting elements are arranged; and a lens corresponding to the number of the plurality of light emitting elements. An exposure head, comprising: a lens array having: 2. The exposure head according to claim 1, wherein each lens of the lens array has a positive power. 3. The exposure head according to claim 1, wherein the lens array is a plurality of lens arrays arranged in the optical axis direction. 4. The exposure head according to claim 1, wherein the lens array has a convex shape of an entrance surface and an exit surface of each lens. 5. The exposure apparatus according to claim 1, further comprising an opening unit in which openings corresponding to the number of the plurality of light emitting elements are formed at regular intervals. head. 6. The exposure head according to claim 5, wherein an opening of the opening means has a size smaller than an effective diameter of the lens. 7. The opening means is provided between an entrance surface and an exit surface of each lens.
Exposure head according to 4. 8. The exposure head according to claim 1, further comprising a diffusing unit for diffusing a light beam emitted from the lens array. 9. The exposure according to claim 1, wherein the lens array has lenses corresponding to an even number increased from the number of the plurality of light emitting elements. head.