JP2003315729A - Imaging element array, optical writing unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain an optical system whose brightness is more improved than in a conventional manner by constituting a roof prism lens of an anamorphic lens and bringing the incident lens surface close to an object surface, as for the optical system (imaging element array) using a roof prism lens array. <P>SOLUTION: The roof prism lens array 10 is constituted by integrally arranging several roof prism lenses 10<SB>1</SB>to 10<SB>n</SB>constituted of the incident lens surface 1, a roof prism part 2 and an exit lens surface 3. In this case, the roof prism lens is constituted of the anamorphic lens, and the incident lens surface 1 is brought closer to the object surface 4 than in the conventional manner, and the symmetrical structure with reference to the ridge of the roof prism part 2 is not introduced, then, the luminous flux emitted from the light emitting element positioned on the object surface 4 is coupled by the imaging element array 10, then, the angle of the guided luminous flux becomes larger than the conventional one. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging element array,
More specifically, the present invention relates to an optical writing unit and an image forming apparatus, and more specifically, a solid-state optical writing type digital copying machine, a printer,
The present invention relates to an imaging element array used in a digital output device such as a digital FAX, an optical writing unit including the imaging element array, and an image forming apparatus using the optical writing unit as an exposure unit.

[0002]

2. Description of the Related Art In recent years, as digital image output devices such as digital copying machines, printers, and digital facsimiles have become smaller, there has been a demand for smaller optical writing units for performing digital optical writing. At present, the digital optical writing method in the optical writing unit can be roughly classified into two types. One is an optical scanning method in which a light beam emitted from a light source such as a semiconductor laser is optically scanned by an optical deflector and a light spot is formed by a scanning imaging lens. The other is an LED array or an organic EL. This is a solid-state optical writing system in which a light beam emitted from a light emitting element array such as an array forms a light spot by an imaging element array.

In the above-mentioned optical scanning system, since the light is scanned by the optical deflector, the optical path length becomes large, whereas
The solid-state optical writing method has an advantage that the optical writing unit can be configured compactly because the optical path length can be extremely shortened. Moreover, since the solid-state optical writing method does not use a movable part such as an optical deflector,
There is also an advantage that noise can be suppressed (low noise). The solid-state optical writing optical writing unit includes a light emitting element array including a plurality of light emitting elements and an image forming element array including a plurality of image forming elements.

FIG. 20 is a view for explaining an example of an optical writing unit using a rod lens array as an imaging element array, which is a general solid-state optical writing type optical writing unit. Light emitted from the plurality of LEDs 121 therein is projected onto the photosensitive surface 160 by the condensing action of the rod lens array 150. As a result, a minute point image is formed on the photosensitive surface 160.

FIG. 21 is a diagram for explaining an example of an optical writing unit using a roof prism lens array as an example using another imaging element array, in which the roof prism lens array 110 is held. It is held by a member 131 and fixed to the frame 130 by a holder 132. The LED array 120 is also positioned with respect to the roof prism lens array 110, and
The light emitted from each light-emitting element (LED element) of the LED array 120, which is fixed to 30, forms a light spot on the image surface (image-bearing body surface) 105, so that the image surface 105
Form a point image on.

The light emitting element array is shown in FIGS.
As shown in FIG. 2, an LED array in which light emitting diodes (LEDs) are arranged at a predetermined arrangement pitch is generally used as a light emitting element. LED arrays are on the substrate
About 100 light emitting diode array chips are mounted, and several tens to several hundreds of light emitting diodes (LEDs) are arranged at predetermined intervals on each light emitting diode array chip. At this time, the light emitting diode array chips adjacent to each other are mounted on the substrate such that the distance between the light emitting diodes at the ends thereof is equal to the predetermined distance.

Other light emitting element arrays include organic E
There are an EL array in which L elements are arranged, an LD array in which semiconductor LDs (surface emitting type, edge emitting type) are arranged, and the like. Further, a high output light source such as a fluorescent tube using a shutter array such as a liquid crystal shutter can also be used as a kind of light emitting element array.

FIG. 22 is a diagram for explaining an example of the rod lens array 150 shown in FIG. A rod lens array in which a plurality of gradient index rod lenses are bundled is generally used as an imaging element array used in a solid-state optical writing optical writing unit. Is, for example, the rod lens 15
1 is bundled in a bale stack in two rows, and the periphery thereof is held by a side plate 152. Rod lens 151
An opaque member 153 is filled and solidified between the spaces.
In addition, there are some that are configured in one row.

FIG. 23 is a view for explaining an example of the roof prism lens array 110 shown in FIG. 21.
1, exit lens surface 103, and roof prism portion 10
2 has a structure in which a plurality of roof prism lenses integrally formed are arranged integrally.

As described above, the optical writing unit using the rod lens array is generally used as the image forming element array, but the image using the optical writing unit using the image forming element array is used. When an image is output by the forming apparatus, density unevenness called vertical stripes (white stripes or black stripes in a monochrome image) is recognized on the output image. The applicant has found through experiments that, as factors causing the density unevenness, there are non-uniformity of beam characteristics due to the imaging element array and non-uniformity of light-emitting element intervals due to the light-emitting element array. .

It has been found that the structure of the rod lens array has a great influence on the nonuniformity of the beam characteristics caused by the imaging element array, which is one of the factors. That is, since the rod lens array is formed by bundling a plurality of rod lenses having a refractive index distribution, as shown in FIG. 22, variations in the optical axis directions between adjacent rod lenses are likely to occur. . Since the light flux emitted from one light emitting element is imaged through a plurality of rod lenses, the shape and position of each image obtained through each rod lens due to the variation of the optical axis of each rod lens. Varies, the combined image depends on the optical axis variation of the rod lens. Therefore, the image formed corresponding to the plurality of light emitting elements changes according to the variation of the optical axis of the rod lens, resulting in non-uniformity of the beam characteristics. In addition to variations in the optical axis, variations in refractive index distribution, variations in rod diameter, etc. are also affected.

Therefore, the present applicant has formed an optical writing unit using a roof prism lens as an image forming element capable of reducing a variation due to a processing error such as an optical axis variation by integrally forming a plurality of image forming elements. Is proposed. However, compared to an optical writing unit using a roof prism lens array in which vertical stripes are not recognized,
The optical writing unit using the rod lens array is more advantageous in terms of brightness of the optical system.

[0013]

SUMMARY OF THE INVENTION The present invention is an optical system (imaging element array) using a roof prism lens array as described above, wherein the roof prism lens is an anamorphic lens, and the incident lens surface is an object surface. This is done for the purpose of realizing an optical system capable of improving brightness more than ever before by bringing them closer.

Further, in the optical writing unit using the roof prism lens array, the roof prism lens is an anamorphic lens, and the incident lens surface is closer to the object surface, whereby the brightness can be improved as compared with the conventional optical writing unit. It was made for the purpose of realizing.

Further, in the image forming apparatus using the optical writing unit using the roof prism lens array, the roof prism lens is an anamorphic lens, and the incident lens surface is closer to the object surface, so that the brightness is higher than that of the conventional one. The purpose of the invention is to realize an improved image forming apparatus capable of high-speed printing.

Also, from the environmental aspect, by adopting the solid-state optical writing method, the optical writing unit can be constructed more compactly than the optical scanning method (reduction of unit parts / materials). The purpose of this is to obtain the advantage that there is no moving part such as a deflector (low noise). Further, since the brightness can be improved as compared with the conventional one, when the same printing speed as the conventional one is used, the light emitting power of the light emitting element array is reduced to achieve low power consumption (energy saving). Is.

[0017]

According to a first aspect of the present invention, there is provided an imaging element array in which a plurality of roof prism lenses each of which includes an entrance lens surface, a roof prism portion, and an exit lens surface are integrally arranged. The roof prism lens is an anamorphic lens, and when the distance from the object surface to the entrance lens surface is d0 'and the distance from the exit lens surface to the image surface is d3', d0 '<d3'. It is characterized by that.

According to a second aspect of the present invention, in the first aspect of the invention, the incident lens surface has no power in the arrangement direction of the roof prism lenses.

According to a third aspect of the invention, in the second aspect of the invention, the exit lens surface has a non-arcuate shape in the arrangement direction of the roof prism lenses.

According to a fourth aspect of the present invention, in the first aspect of the invention, the absolute lateral magnification Mm in the arrangement direction of the roof prism lenses, which is determined by the distance relationship between the object plane, the roof prism lens, and the image plane, is absolute. The value is characterized by being approximately upright.

According to a fifth aspect of the present invention, in the first aspect of the invention, the lateral magnification Ms in the orthogonal direction to the arrangement of the roof prism lenses is determined by the distance relationship between the object plane, the roof prism lens, and the image plane. It is characterized in that the absolute value is 1.5 ≦ | Ms | ≦ 3.0.

The invention of claim 6 is characterized in that, in the invention of claim 1, light-attenuating means for attenuating the intensity of light passing between the adjacent roof prism lenses is provided between the roof prism lenses. It was done.

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the light attenuating means comprises a light attenuating member having a width W in the arrangement direction formed between the roof prism lenses. When the refractive index is N, the refractive index of the light attenuating member is N ′, and the internal absorption coefficient is k ′, ΔN
= (N'-N) / N, it is characterized by satisfying 0≤ΔN≤0.05 k '> 0.43 / W.

According to an eighth aspect of the present invention, an image forming element array in which a plurality of roof prism lenses each including an entrance lens surface, a roof prism portion, and an exit lens surface are integrally arranged, and a plurality of light emitting elements are predetermined. In an optical writing unit for forming a light spot consisting of a light emitting element array in which a plurality of light emitting element array chips arranged at intervals are arranged, the roof prism lens is an anamorphic lens, and from the object plane, The distance to the entrance lens surface is d0 ', and the distance from the exit lens surface to the image surface is d0'.
When 3'is set, d0 '<d3'.

According to a ninth aspect of the present invention, an imaging element array in which a plurality of roof prism lenses each including an incident lens surface, a roof prism portion, and an exit lens surface are integrally arranged, and a plurality of light emitting elements are predetermined. In an image forming apparatus in which an optical writing unit including a light emitting element array formed by arranging a plurality of light emitting element array chips arranged at intervals is used as an exposure unit, the roof prism lens is an anamorphic lens and an object plane. To d0 ', and d3' from the exit lens surface to the image plane, d0 '<d3'.

[0026]

1 is a schematic diagram for explaining an embodiment of an image forming element array (roof prism lens array) according to the present invention. A roof prism lens array 10 is
A plurality of roof prism lenses 10 ₁ to 10 _{n including an} entrance lens surface 1, a roof prism portion 2, and an exit lens surface 3 are integrally formed and formed. The roof prism lenses 10 ₁ to 10 _n are anamorphic lenses. It should be noted that α ′ is the angle of the light flux that can be captured by the imaging element array 10 by coupling the light flux emitted from the light emitting element (not shown) located on the object plane 4.

FIG. 2 is a perspective view of the imaging element array shown in FIG. 1. The incident lens surface 1 is a cylindrical surface having no power in the array direction but having power in the array orthogonal direction. The light flux emitted from the light emitting element located on the object plane 4 is converged by the incident lens surface 1 and then totally reflected by the two roof prism surfaces which are substantially orthogonal to each other and form the roof prism portion 2, and the exit lens surface. An image is formed on the image plane 5 via 3.

FIG. 3 is a schematic view for explaining an example of an image forming element array consisting of a conventional roof prism lens,
In the conventional roof prism lens, the entrance lens surface 101 and the exit lens surface 103 are configured by coaxial spherical surfaces or aspherical surfaces, and the entrance lens surface 101 and the exit lens surface 103 have the same surface shape. In addition, the entrance lens surface 1
The distance from 01 to the roof prism portion 102 is equal to the distance from the roof prism portion 102 to the exit lens surface 103. Further, from the object surface 104 to the entrance lens surface 101
Distance d0 to the exit lens surface 103 to the image surface 105
Are equal to each other (d0 = d3). That is, it has a structure in which the object plane side and the image plane side are symmetrical with respect to the ridgeline of the roof prism portion 102. Note that α is the object plane 10
This is the angle of the light flux that can be captured by the imaging element array 110 by coupling the light flux emitted from the light emitting element located at No. 4.

Even in the conventional roof rhythm lens array, the incident lens surface can be brought close to the object surface with d0 = d3, but the optical path length passing through the roof prism lens becomes long, and the light flux in the arrangement direction is increased. The angle of capturing light becomes smaller, and the brightness is reduced. Therefore, in the present invention, the roof prism lens is an anamorphic lens, the incident lens surface is brought close to the object surface (d0 '<d3'), and a structure not symmetrical with respect to the ridgeline of the roof prism portion is used. Achieve> α.

As will be described later, in the arrangement direction, although refracting at the incident lens surface 1, since it has no power, there is no great difference in the angle of taking in the light beam. Therefore, the brightness of the imaging element array 10 can be approximated as being substantially proportional to α. Therefore, the roof prism lens is used as an anamorphic lens, and the incident lens surface 1
Is brought closer to the object plane 4, the brightness of the imaging element unit is improved by approximately (α ′ / α) times.

FIG. 4 is a development view of the image forming element array shown in FIG. 1 when viewed from the image plane side, and the incident lens surface 1 is a plane because it has no power in the arrangement direction. In FIG.
Let d ′ be each surface spacing, r be the radius of curvature, and N be the refractive index,
Paraxial ray tracing is performed to find the angle (β ') of the light beam that can be captured by the roof prism lens. When performing paraxial ray tracing, the reduced surface spacing e ′ and the surface power φ are used. Here, when the surface numbers was m, in terms of spacing e _{m ',} the power phi _m surface can be written by the following equation. _{e m '= d m' /} N m 'φ m = (N m' -N m) / r m

FIG. 5 is a development view showing the imaging element array shown in FIG. 4 by the conversion surface spacing e'and the surface power φ, and FIG. 6 is
FIG. 6 is a development view of the conventional imaging element array (roof prism lens) shown in FIG. 3 as seen from the image plane side, as a comparative example with respect to FIGS. 4 and 5. Since the conventional roof prism lens has a symmetrical structure with respect to the ridgeline of the roof prism portion, d0 = d3 d1 = d2 r1 = -r3.

Table 1 shows parameters e ′ (e ₀ ′ to e ₃ ′) and φ (φ ₁ ˜) for the roof prism lens for performing paraxial ray tracing in the imaging element array shown in FIG.
φ ₃ ), and for performing paraxial ray tracing in the imaging element array shown in FIG.
9 is a table showing a comparative example showing parameters e ′ and φ for a roof prism lens. Note that d2 = d2 ', d3 =
It was compared as d3 '.

[0034]

[Table 1]

Comparative Examples e0 '= 9 mm, Examples 1 to 1
In the third embodiment, e0 ′ = 2 mm, 3 mm, 4 mm,
The entrance lens surface 1 is brought close to the object surface 4. Where e
1'is set so that the lateral magnification in the arrangement direction is | Mm | = 1.0 (equal magnification).

FIG. 7 is a diagram showing the relationship between the ray height h and the reduced surface spacing e'when ray tracing is carried out for Example 2 shown in Table 1, and FIG. 8 is for the comparative example shown in Table 1. It is a figure which shows the relationship between the ray height h at the time of ray tracing, and conversion surface space | interval e '. The ray in a figure traces the peripheral ray. The outermost rays are the roof prism lens 1
It is limited by the aperture diameter in the arrangement direction of the exit lens surfaces 3 and 103 of 0 _n and 110 _n , and here h = 0.35 mm.
Table 2 is a table showing β ′ for Examples 1 to 3 and β for Comparative Examples obtained by ray tracing.

[0037]

[Table 2]

From Table 2, in the arrangement direction, although the light is refracted at the incident lens surface 1, the incident lens surface 1 does not have power, so that there is a difference between the angles β and β'for taking in the light flux from a certain object point. Absent. Also, it can be seen that there is no great difference in the angle of view that can be captured. Therefore, the brightness of the imaging element array can be approximated to be approximately proportional to the angle α of capturing the light flux in the array orthogonal direction. Therefore, by making the roof prism lens 10 _{n an} anamorphic lens and bringing the incident lens surface 1 having no power in the array direction closer to the object surface 4 than in the conventional case, the brightness of the imaging element array 10 is approximately (α ′ / It can be improved by α) times.

The exit lens surface of the roof prism lens has a non-arcuate shape in the arrangement direction. Since the entrance lens surface has no power in the arrangement direction, it is necessary to form an image only on the exit lens surface in the arrangement direction. Therefore, by making the exit lens surface have a non-arcuate shape, it is possible to satisfactorily correct aberrations in the arrangement direction.

Further, the lateral magnification in the array direction, which is determined by the distance relationship between the object plane, the roof prism lens and the image plane, is assumed to be erect equal magnification. As in Examples 1 to 3 shown in Table 1, the erecting equal-magnification in the arrangement direction (| Mm |
= 1.0, but it is an inverted image, and the image is actually inverted by the roof prism part, and an erect image is obtained.) When a plurality of lenses are arranged, a certain point on the object plane forms an image at a certain point on the image plane through each roof prism lens, and these images can be exactly overlapped.

That is, in the imaging element array, the images are overlapped and the brightness can be ensured by making them upright in the arrangement direction. Also, slightly expanded (|
Mm | to about 1.02), and the light spot characteristics when the image plane is defocused can be improved.

FIG. 9 is a developed view of the image-forming element array shown in FIG. 1 when viewed from the arrangement direction. Table 3 shows the image-forming element array shown in FIG. In the table indicated by φ, parameters corresponding to the first embodiment of the imaging element array shown in FIG. 9 (conversion surface spacing e ′ (e ₀ ′ to e ₃ ′), surface power φ (φ _{1 to} φ ₃ )) ) To Examples 4 to 6 and parameters (e ′ (e ₀ ′ to e ₃ ′), φ (φ _{1 to} φ ₃ )) corresponding to Example 2 of the imaging element array shown in FIG. Example 7
In Example 9, Example 3 of the imaging element array shown in FIG.
Corresponding to (e ′ (e ₀ ′ to e ₃ ′), φ (φ
_{1 to} φ ₃ )) are shown in Examples 10 to 12.

[0043]

[Table 3]

FIG. 10 is a diagram showing the relationship between the ray height h and the reduced surface spacing e'when ray tracing is carried out for Example 8 shown in Table 3. The light rays in FIG. 10 trace the light rays at the outermost periphery. The light rays at the outermost periphery are limited by the aperture diameter of the exit lens surface 3 of the roof prism lens 10 _{n in} the direction orthogonal to the array, and here h = 0.46 mm. Table 4
[Fig. 4] is a table showing α'for Examples 4 to 12 and α for Comparative Examples obtained by ray tracing.

[0045]

[Table 4]

From Table 4, α'is larger than that of the comparative example (conventional roof prism lens), and the brightness of the imaging element array is improved.

Further, Table 5 shows Examples 4 to 12 shown in Table 4.
3 is a table showing the results of obtaining the absolute value of the lateral magnification Ms in the direction orthogonal to the array, which is determined by the distance relationship among the object plane 4, the roof prism lens 10 _n, and the image plane 5.

[0048]

[Table 5]

From Table 5, it can be seen that the absolute value of the lateral magnification in the direction orthogonal to the array increases as the brightness improves. Further, the brightness improvement rate (α '/ α) and the absolute value of the lateral magnification | Ms | are in a substantially proportional relationship.

When the lateral magnification is increased, the light spot on the image plane is enlarged, and when the lateral magnification is increased too much, the resolution is deteriorated. For example, 20
Considering a rectangular planar light source of μm (corresponding to 600 dpi), if | Ms | = 1.0, the beam spot diameter is 20 * 1. From 0 + 20 = 40, the beam spot diameter becomes about 40 μm, and a beam spot diameter almost equal to the pixel size of 600 dpi (42.3 μm) can be obtained.

When Ms = 3.0, 20 * 3.0 + 20 = 80, and the beam spot diameter is about 80 μm, and the beam spot diameter is about twice, which is twice the 600 dpi pixel size. If it is about twice the pixel size, it can be practically used. Therefore, in view of the brightness improvement of 50% or more and the deterioration of the resolution due to the beam spot expansion, it is desirable that 1.5 ≦ | Ms | ≦ 3.0 is satisfied.

FIG. 11 is a diagram for explaining an optical path of an image forming light beam (a light beam forming an image) by the image forming element array of the present invention. The actual optical path is three-dimensional and becomes complicated when illustrated. Therefore, for the sake of convenience, it is drawn in a developed view as a two-dimensional view. As shown in FIG. 11, light emitted from an object point on the object surface enters the entrance lens surface, is totally reflected by the two prism surfaces of the roof prism portion of the roof prism lens (A), and then exits. The light exits from the lens surface and reaches an image point on the image surface at the same position as the object point in the arrangement direction. At this time, the light always travels within the roof prism portion of the roof prism lens (A) and the exit lens surface.

The light totally reflected by the roof prism portion of the roof prism lens (B) always exits from the exit lens surface of the roof prism lens (B) and reaches the image point. The light totally reflected by the roof prism portion of the roof prism lens (C) also always exits from the exit lens surface of the roof prism lens (C) and reaches the image point.

In the state shown in FIG. 11, the light emitted from a certain object point "forms by combining one image point" through a plurality of roof prism lenses. The image formed on the object point in this way is called "main light". That is, FIG. 11 shows how the main light is imaged.

FIG. 12 shows the optical path in the case where a part of the light emitted from the object point reaches the image plane as "unnecessary light" without forming an image at the image point, following FIG. It is a figure. In FIG. 12, light emitted from an object point on the object plane is incident on the incident lens surface, and after being totally reflected by the two prism surfaces of the roof prism portion of the roof prism lens (D), the roof prism lens ( Emitted from the exit lens surface of C),
Point Q on the image plane at a position different from the object point in the array direction
To reach. That is, this light is "unnecessary light" that does not form an image at the image point.

When the "unnecessary light" is condensed at a certain position (not focused like the main light but concentrated in a certain area), such unnecessary light is ghost light. Call. The position where the ghost light is focused depends on the array pitch of the roof prism lenses and the shape of the roof prism lenses. Since these ghost lights may affect the output image during image formation and may deteriorate the image quality, it is desirable to reduce the ghost light within a range that does not affect the image.

FIG. 13 is a diagram for explaining an embodiment of the image-forming element array of the present invention provided with a light attenuating means for attenuating the intensity of light passing between the adjacent roof prism lenses. 13A is a view of the arrangement direction of the imaging element array viewed from the exit lens surface side, and FIG.
FIG. 14A is a cross-sectional view taken along the line BB of FIG. 14A, and FIG. In order to reduce the ghost light, each roof prism lens 10 _{1 is provided} with a light attenuating means as shown in FIG.
Must be between 10 and 10 _n . The light attenuating means 6 is
A light attenuating member (1) having a large internal absorptance and (2) having a refractive index close to that of the material of the roof prism lens can be formed by filling between the roof prism lenses 10 ₁ to 10 _n .

Considering the case where light travels through the material having the internal absorption coefficient k [mm ^-1 ] by the optical path length T [mm], the incident energy to the material is Ein and the emission energy is Eo.
ut satisfies the following relationship. Eout / Ein = 10 ^{−kT A} large internal absorptance means that it is a member that is well absorbed and that it is opaque to the wavelength of light.

When the refractive index of the light attenuating member is N'and the refractive index of the material of the roof prism lens is N, it is desirable that N'≥N. This is a condition for refracting from a medium having a refractive index N to a medium having a refractive index N'according to the law of refraction (Snell).

Therefore, as shown in FIG. 14, the above two meanings are from a medium having a refractive index N and an internal absorption coefficient k (roof prism lens) to a medium having a refractive index N'and an internal absorption coefficient k '(light This means that the light traveling to the attenuating means 6) is refracted at the boundary surface and the energy is attenuated in the light attenuating means 6. Since the lens material generally has a thickness of 3 mm and a transmittance of 90% or more, k ≦ 0.015, which can be regarded as almost zero.

On the other hand, in the light attenuating means 6, since it is desired to reduce the light energy by 25% or more, k'includes the optical path length T through which 10'-k'T≤0.25 and k'T≥0. It is desirable to satisfy 6. Further, when the width of the light attenuating means 6 in the arrangement direction is W, a ray that passes through between the adjacent roof prism lenses 10 ₁ to 10 _n and becomes a ghost light has a considerably large incident angle on the boundary surface. Since the refraction angle is 45 ° or more, T ≧ √2 · W, and therefore it is sufficient to satisfy k ′ ≧ 0.6 / (√2 · W)> 0.43 / W.

Further, even if N ′ ≧ N, the reflected energy obtained by the Fresnel equation exists at the boundary surface, so this reflected energy must be suppressed as much as possible. Therefore, the smaller the difference in refractive index, the smaller the reflected energy. Therefore, ΔN = (N ′
When −N) / N, it is desirable that 0 ≦ ΔN ≦ 0.05.

FIG. 15 is a view for explaining another embodiment of the tie element array of the present invention having the light attenuating means 6, FIG.
FIG. 6 is a diagram for explaining still another embodiment of the tie element array of the present invention including the light attenuating means 6. As shown in FIG. 13, the exit lens surface 3 of each roof prism lens
The light attenuating member 6 may be filled only in the space between the light attenuating means 6 and the light attenuating means 6 by filling the light attenuating member deeper toward the entrance lens surface 1 as shown in FIG. Is also good. However, if it is filled too deeply, the main light guided from the object point to the roof prism portion 2 through the incident lens surface 1 will also be attenuated and the brightness will be reduced, so a balance with the reduction of ghost light should be achieved. is necessary.
As a manufacturing method, the roof prism lens may be mechanically cut, and a light attenuating member may be inserted or filled therein, or the roof prism lenses 10 ₁ to 10 _n in the cut state may be formed in advance. The light attenuating member may be inserted or filled therein. Other known manufacturing methods can be used.

As shown in FIG. 16, a light attenuating member is filled between the exit lens surfaces 3 of each roof prism lens, and the light is guided into the member that guides light from the entrance lens surface 1 to the roof prism portion 2. Attenuating the attenuating member, the optical attenuating means 6
May be formed. As a manufacturing method, the light attenuating members to be embedded may be arranged in advance at an equal pitch, and a resin or the like forming the roof prism lenses 10 ₁ to 10 _n may be poured around the light attenuating members. Other known manufacturing methods can be used. A light scattering member may be used instead of the light attenuating member, or a mixture of the light scattering member and the light attenuating member may be used. In the present invention, any member may be used as long as it can attenuate the intensity of light passing through between the adjacent roof prism lenses 10 ₁ to 10 _n .

FIG. 17 is a diagram for explaining an embodiment of an optical writing unit formed together with a light emitting element array by using the imaging element array 10 as shown in FIG.
The image-forming element array 10 is held by a holding member (not shown), fixed to the frame 30 by a holding tool, and
The array 20 is also positioned with respect to the imaging element array 10 and is fixed to the frame 30 to form an optical writing unit 40, and each light emitting element (LED) of the LED array 20 is formed.
The light emitted from the element forms a light spot on the image surface (image carrier surface) 5.

The light emitting element array has a structure in which a plurality of light emitting elements are arranged at a constant interval, and a light emitting diode (LED) array as shown in FIG. 17 is used as a typical light emitting element array. ing. FIG. 18 is a view for explaining the LED array 20 shown in FIG.
18A is a schematic view of the LED array 20 when viewed from a direction orthogonal to the array direction and the array orthogonal direction, and FIG. 18B is a view taken along the line BB of FIG. 18A. Cross section,
FIG. 18C is a schematic diagram of a light emitting diode (LED) array chip. The LED array 20 is formed by arranging a plurality of LED array chips 22 on a substrate 21, and on both sides (or one side) thereof, as shown in the figure.
A driver IC 23 for driving the LED 22b is mounted on. Further, there is a connector section 24 for connecting a signal cable for giving information such as an image signal to the driver IC 23.

In addition, as shown in FIG.
The array chip 22 has an LED 22b on the chip 22a.
Are arranged in a plurality. Generally, tens to hundreds of LEDs 22b are arranged on one chip 22a, and tens of LED array chips 22 are arranged on the substrate 21. For example, in order to print A4 size at 600 dpi, 128 chips are placed on one chip 22a.
One LED 22b is arranged, and 40 LED array chips 22 are arranged on the substrate 21.
28 × 40 = 5120 LEDs 22b are arranged.

Further, the image forming device array 10 as shown in FIG. 1 is used to form an optical writing unit 40 in combination with the light emitting device array 20, and the image forming apparatus is formed by using it as the exposure unit 40. You can An electrophotographic process is one of the image forming processes for forming an image in an image forming apparatus. Based on FIG. 19 below,
An outline of an image forming apparatus using an electrophotographic process will be described.

FIG. 19 is a diagram for explaining an embodiment of the image forming apparatus of the present invention. In the electrophotographic process, a potential is applied (charged) to the image carrier (photoconductor) 41 by the charging unit 42, and a light spot from the optical writing unit 40 is irradiated onto the image carrier 41 to form a latent image. (Exposure), toner is attached to the latent image by the developing unit 43 to form a toner image (development), the toner image is transferred to the recording paper 44 by the transfer unit 45 (transfer), pressure or heat is applied,
This is a process of fusing (fixing) the recording paper 44 with the fixing unit 46. The residual toner adhering to the image bearing member 41 after the transfer is removed by the cleaner unit 47, and the potential is removed by the charge eliminating unit 48. Further, the optical writing unit 40 of the present invention can be applied to an image forming apparatus called a tandem type, which is advantageous for high-speed color image output.

[0070]

According to the present invention, there is provided an imaging element array in which a plurality of roof prism lenses each having an entrance lens surface, a roof prism portion, and an exit lens surface are integrally arranged. Since the roof prism lens is an anamorphic lens and the entrance lens surface can be brought closer to the object surface, the brightness of the imaging element array can be improved.

According to the present invention, according to the present invention, in the imaging element array in which a plurality of roof prism lenses each including an incident lens surface, a roof prism portion, and an exit lens surface are integrally arranged, a roof is provided. Since the incident lens surface of the prism lens is a cylindrical surface having no power in the arrangement direction, the processing becomes easy, and at the same time, there is no need to align the optical axes of the incident lens surface and the exit lens surface in the arrangement direction.

According to the present invention, according to the present invention, an image forming element in which a plurality of roof prism lenses each of which has an incident lens surface, a roof prism portion composed of an anamorphic lens, and an exit lens surface are integrally arranged. In the array, in the imaging element array in which the distance between the entrance lens surface and the object surface is shorter than the distance between the exit lens surface and the image surface, the exit lens surface of the roof prism lens has a non-arcuate shape in the array direction. Aberrations in the arrangement direction can be corrected well.

According to the present invention, according to the present invention, an imaging element in which a plurality of roof prism lenses each having an entrance lens surface, a roof prism portion composed of an anamorphic lens, and an exit lens surface are integrally arranged. In an imaging element array that is an array in which the distance between the incident lens surface and the object surface is shorter than the distance between the exit lens surface and the image surface, the absolute value of the lateral magnification Mm in the array direction is set to be substantially upright. Brightness can be secured by overlapping the images.

According to the present invention, according to the present invention, an image forming element in which a plurality of roof prism lenses each having an entrance lens surface, a roof prism portion made of an anamorphic lens, and an exit lens surface are integrally arranged. In an imaging element array that is an array in which the distance between the entrance lens surface and the object surface is shorter than the distance between the exit lens surface and the image surface, the absolute value of the lateral magnification Ms in the array orthogonal direction is 1.5.
Since the range of ≦ | Ms | ≦ 3.0 is suppressed, it is possible to achieve a brightness improvement of 50% or more compared to the conventional case without deteriorating the resolution due to beam spot expansion in practical use.

According to the present invention, according to the present invention, an image forming element in which a plurality of roof prism lenses each of which has an entrance lens surface, a roof prism portion made of an anamorphic lens, and an exit lens surface are integrally arranged. In an array, an imaging element array in which the distance between the entrance lens surface and the object surface is shorter than the distance between the exit lens surface and the image surface, light attenuation for attenuating the light intensity passing between adjacent roof prism lenses Since the means is provided between the roof prism lenses, the ghost light can be reduced and the image quality is not deteriorated.

According to the present invention, in the image forming element array having the light attenuating means, the light attenuating means is formed between the roof prism lenses and has a width W in the arrangement direction. ΔN when the refractive index of the roof prism lens is N, the refractive index of the light attenuating member is N ′, and the internal absorption coefficient is k ′.
When = (N'-N) / N, 0≤ΔN≤0.05 k '> 0.43 / W can be satisfied, and the ghost light can be more effectively reduced.

According to the present invention, according to the present invention, a plurality of roof prism lenses each having an incident lens surface, a roof prism portion composed of an anamorphic lens, and an exit lens surface are integrally arranged to form an image-forming element. A bright optical writing unit can be realized by using an imaging element array which is an array in which the distance between the entrance lens surface and the object surface is shorter than the distance between the exit lens surface and the image surface.

According to the present invention, according to the present invention, an imaging element in which a plurality of roof prism lenses each of which has an entrance lens surface, a roof prism portion made of an anamorphic lens, and an exit lens surface are integrally arranged. Since the array is an imaging element array in which the distance between the entrance lens surface and the object surface is shorter than the distance between the exit lens surface and the image surface, and an optical writing unit including a light emitting element is used as the exposure means, the printing speed is improved. It is possible to realize an image forming apparatus that speeds up.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an example of an imaging element array (roof prism lens array) of the present invention.

FIG. 2 is a perspective view of the imaging element array shown in FIG.

FIG. 3 is a schematic diagram for explaining an example of an image forming element array including a conventional roof prism lens.

FIG. 4 is a development view of the imaging element array shown in FIG. 1 when viewed from the image plane side.

5 is a development view showing the imaging element array shown in FIG. 4 in terms of reduced surface spacing e ′ and surface power φ.

6 is a development view of a conventional imaging element array (roof prism lens) viewed from the image plane side as a comparative example with respect to FIGS. 4 and 5. FIG.

FIG. 7 is a diagram showing a relationship between a ray height h and a reduced surface spacing e ′ when ray tracing is performed for Example 2 shown in Table 1.

8 is a diagram showing the relationship between the ray height h and the reduced surface spacing e ′ when ray tracing is performed for the comparative example shown in Table 1. FIG.

9 is a development view of the imaging element array shown in FIG. 1 when viewed from the arrangement direction.

FIG. 10 is a diagram showing the relationship between the ray height h and the reduced surface spacing e ′ when ray tracing is performed for Example 8 shown in Table 3.

FIG. 11 is a diagram for explaining an optical path of an image forming light beam (a light beam forming an image) by the image forming element array of the present invention.

FIG. 12 is a diagram showing an optical path in the case where a part of light emitted from an object point does not form an image on an image point and becomes “unnecessary light” and reaches an image plane, following FIG. 11. .

FIG. 13 is a diagram for explaining an embodiment of the imaging element array of the present invention, which is equipped with a light attenuating means for attenuating the intensity of light passing between adjacent roof prism lenses.

FIG. 14 is a schematic view of a light attenuation means.

FIG. 15 is a diagram for explaining another embodiment of the tie element array of the present invention including a light attenuator.

FIG. 16 is a view for explaining still another embodiment of the tie element array of the present invention including the light attenuating means.

FIG. 17 is a diagram for explaining an example of an optical writing unit formed together with a light emitting element array using the imaging element array as shown in FIG. 1.

FIG. 18 is a diagram for explaining the LED array shown in FIG.

FIG. 19 is a diagram for explaining an embodiment of the image forming apparatus of the present invention.

FIG. 20 is a diagram for explaining an example of an optical writing unit using a rod lens array as an imaging element array.

FIG. 21 is a diagram for explaining an example of an optical writing unit using a roof prism lens array as an imaging element array.

22 is a diagram for explaining an example of the rod lens array shown in FIG. 20. FIG.

23 is a diagram for explaining an example of the roof prism lens array shown in FIG. 21. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Incident lens surface, 2 ... Roof prism part, 3 ... Emitting lens surface, 4 ... Object surface, 5 ... Image surface, 6 ... Light attenuation means, 10
... Imaging element array (roof prism lens array), 1
0 ₁ to 10 _n ... Roof prism lens, 20 ... LED array (light emitting element array), 21 ... Substrate, 22 ... Light emitting diode array chip, 22a ... Chip, 22b ... LED,
23 ... Driver IC, 24 ... Connector part, 30 ... Frame, 40 ... Optical writing unit (exposure unit), 41 ... Image carrier (photoreceptor), 42 ... Charging unit, 43 ... Developing unit, 44 ... Recording paper , 45 ... Transfer unit, 46 ...
Fixing unit, 47 ... Cleaner unit, 48 ... Static elimination unit.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) G02B 17/08 H04N 1/036

Claims (9)

[Claims] 1. An incident lens surface, a roof prism portion,
In an imaging element array in which a plurality of roof prism lenses each including an exit lens surface are integrally arranged, the roof prism lens is an anamorphic lens, and the distance from the object surface to the entrance lens surface is d0 ′,
An imaging element array, wherein d0 '<d3' when the distance from the exit lens surface to the image surface is d3 '. 2. The imaging element array according to claim 1, wherein the incident lens surface has no power in the arrangement direction of the roof prism lenses. 3. The imaging element array according to claim 2, wherein the exit lens surface has a non-arcuate shape in the arrangement direction of the roof prism lenses. 4. The imaging element array according to claim 1, wherein an absolute lateral magnification Mm in an arrangement direction of the roof prism lenses is determined by a distance relationship between the object plane, the roof prism lens, and the image plane. An imaging element array, wherein the value is approximately an upright unity. 5. The imaging element array according to claim 1, wherein a lateral magnification Ms in a direction orthogonal to the array of the roof prism lenses, which is determined by a distance relationship between the object plane, the roof prism lens, and the image plane. An imaging element array having an absolute value of 1.5 ≦ | Ms | ≦ 3.0. 6. The imaging element array according to claim 1, further comprising light attenuating means between the roof prism lenses for attenuating the intensity of light passing between the adjacent roof prism lenses. Imaging element array. 7. The imaging element array according to claim 6, wherein the light attenuating means is formed of a light attenuating member having a width W in the arrangement direction formed between the roof prism lenses, When the refractive index is N, the refractive index of the light attenuating member is N ′, and the internal absorption coefficient is k ′, ΔN
= (N'-N) / N, an imaging element array characterized by satisfying 0≤ΔN≤0.05 k '> 0.43 / W. 8. An incident lens surface, a roof prism portion,
An imaging element array in which a plurality of roof prism lenses each having an exit lens surface are integrally arranged, and a light emitting element array in which a plurality of light emitting element array chips in which a plurality of light emitting elements are arranged at predetermined intervals are arranged In the optical writing unit for forming the light spot, the roof prism lens is an anamorphic lens, the distance from the object surface to the entrance lens surface is d0 ′, and the distance from the exit lens surface to the image surface is Is d3 ', then d0'<d3'. 9. An incident lens surface, a roof prism portion,
An imaging element array in which a plurality of roof prism lenses each having an exit lens surface are integrally arranged, and a light emitting element array in which a plurality of light emitting element array chips in which a plurality of light emitting elements are arranged at predetermined intervals are arranged In an image forming apparatus in which the optical writing unit is used as an exposure unit,
The roof prism lens is an anamorphic lens, and the distance from the object surface to the incident lens surface is d.
0 ', where d0'<d3', where d3' is the distance from the exit lens surface to the image surface.