JPH0485516A - Image forming element - Google Patents

Abstract

PURPOSE:To eliminate the need for the troublesome axis alignment of a lens array, to reduce the chromatic aberration to one lens and projecting an image on a line, and to make the structure compact and simple and facilitate the manufacture by combining a lens array and an array of reflecting surface couples. CONSTITUTION:The image forming element has the reflecting surface group 1 formed by arraying many couples of reflecting surfaces, forming a valley with a vertical angle pi/2, at right angles to the base line and many lens elements 4 which are arrayed in parallel to the reflecting surface group and mutually equal in focal length. The width of the lens elements is set to a half integer larger than 1.5, preferably, >=3 times as large as array intervals of the reflecting surface couples and then when the pitch of the reflecting surface couples is 1, the width of effective reflecting surfaces with p+q=0.5, i.e. 2p+2q=1 becomes 1 and there is no irregularity in brightness due to a deviation between both positions. Further, a light shield means 13 is provided preferably between lenses so that light which is made incident on the lens element 4 does not become stray light by striking on an adjacent lens element after being reflected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an imaging element used in facsimiles, electronic copying machines, LED printers, and the like.

[Prior art]

Facsimile machines, electronic copying machines, LED printers, and the like use optical components that project objects on a line onto a sensor or photosensitive drum at the same magnification.

Conventionally, such optical components include: ■ A so-called rod lens array, which is an array of cylindrical transparent bodies whose refractive index changes continuously in the radial direction from the center, and ■ A multilayer plate that forms an array of spherical lenses. (often three layers), for example, Tokuko Sho 4
9-8893, JP-A-57-104923, JP-A-57-66414, etc. ■ An erect equal-magnification optical system arranged in an array by combining a roof prism and a lens, for example, JP-A-61 -210319, JP-A-56-117201, JP-A-56-1
No. 26801, Japanese Unexamined Patent Publication No. 140301/1983,
JP-A-56-149002, JP-A-60-254
018, JP 60-254019, JP 60-254020, JP 61-23
3714, JP-A-62-91902, and JP-A-62-201417.

[Problem to be solved by the invention]

In the above-mentioned conventional optical component (2), it is necessary to form a refractive index distribution in a cylindrical transparent body and to precisely control this, but this requires special know-how.
It's not easy. Furthermore, it is particularly difficult to make a rod lens with a particularly large diameter, so when it is desired to increase the distance between the lens and the subject, the F value decreases, resulting in a dark optical system.

Next, with the conventional optical component (■) mentioned above, it is difficult to align the optical axes of the single lenses in each layer of the lens array with sufficient precision.
It is difficult to make particularly long arrays.

In addition, the conventional optical components (1) and (2) described above have the disadvantage that chromatic aberration tends to increase because the sum of the refraction angles of light rays becomes large.

On the other hand, the conventional optical component (2) uses a roof prism (or roof mirror) to invert the image, so the integrated refraction angle is small and the chromatic aberration is small. However, it is difficult to precisely align the axes of the prism (roof mirror) and lens.

Furthermore, in common with the above-mentioned conventional optical components (1) to (4), there is a risk that periodic unevenness in the amount of light may occur due to the difference in brightness on the optical axis of the lens and in the periphery.

The problem to be solved by the present invention is to provide a projection optical component that does not require particularly difficult know-how, is easy to manufacture, has small chromatic aberration, and does not cause unevenness in light amount.

[Means to solve the problem]

The imaging element according to the present invention includes a reflective surface group in which a large number of pairs of reflective surfaces forming a valley with an apex angle of π/2 are arranged in a direction perpendicular to the valley line where the reflective surfaces intersect, and this reflective surface group. An optical element having a large number of lens elements arranged in parallel and having the same focal length, and the width of the lens elements is a half-integral multiple of 1.5 or more, preferably 3, of the distance between the reflective surface pairs. It is characterized by being more than twice as large.

Further, in a preferred embodiment of the present invention, the imaging element can be provided with a reflection means for separating the incident light from the subject and the output light that forms an image.

Furthermore, in a preferred embodiment of claim 4, contrast can be improved by arranging a light-shielding surface perpendicular to the arrangement direction of the pair of reflective surfaces in front of the group of reflective surfaces of the optical component.

[For production]

The imaging element of the present invention projects a line image by arranging a large number of equal-magnification imaging units established in one direction by a lens element and a row of minute reflective surface pairs placed behind the lens element. It is.

The operation of the above configuration will be explained in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a pair of reflective surfaces, showing reflection by two reflective surfaces that intersect at right angles. If you look at this situation in a plane perpendicular to both incidence planes from this figure, you will see that the reflected light travels parallel to and in the opposite direction to the incident light.

Next, as shown in FIG. 4, reflection by the above-mentioned reflective surface group 1 arranged at a short pitch and the lens element 4 placed in front of it will be explained.

FIG. 2 shows how light emitted from the focal point 2 of the lens is reflected by the group of reflective surfaces 1, as seen in a plane perpendicular to the ridgeline of the pair of reflective surfaces. These rays are made parallel by a lens,
Since the light is reflected in parallel and opposite directions by the group of reflective surfaces, the light is focused again at point 2 by the lens.

Next, Figure 3 shows this as seen in a plane perpendicular to the arrangement direction of the pair of reflective surfaces, and the pair of reflective surfaces performs the same function as a plane mirror.
The image of point 2 on the subject is focused at position 3.

As a result, in FIG. 4, an image 3 of point 2 on the focal plane is obtained, and this image is a real life-size image in the X direction and an inverted life-size image in the y direction.

FIG. 4 shows one embodiment of the present invention.

With such a very simple configuration, the imaging element of the present invention eliminates the need for troublesome axis alignment, which was required in the lens array, and has the property that zero chromatic aberration is just a lens branch. have

First, the above item (2) will be explained.

If the reflective surface group 1 of the present invention is replaced with an array of reflective surface pairs forming a valley with an apex angle of π/2 and having the same spacing as the lens elements, and each lens element is associated with one reflective surface pair, the above-mentioned It becomes an imaging element similar to the conventional optical component (2). In these imaging elements, it is necessary to correctly align the lens and the pair of reflective surfaces, and if these positions are misaligned, performance degradation such as uneven brightness will occur. In particular, if this shift becomes half a period, it is almost impossible to obtain an image.

In the present invention, this problem is solved by making the width of the lens element a half-integer multiple of 1.5 or more of the spacing between the reflective surface pairs.

This situation will be explained with reference to FIG. Although the case where the width of the lens is 1.5 times the pitch of the pair of reflective surfaces is shown here, the same reasoning holds true for cases where the width is another half-integer multiple.

In the figure, the positional relationship between the reflective surface pair and the lens is classified into three categories. In the same figure (a), when the pitch of the pair of reflective surfaces is 1, p−+−+; r=0.5,゛, 2 p + 2 q = 1, and the effective width of the reflective surface is 1. becomes.

Also, in the case of (t)) (C), the effective width of the reflecting surface is clearly 1, so it can be seen that it is 1 in all cases.

Therefore, when a rectangular lens element is used, as in the embodiments shown in FIG. 5 and subsequent figures to be described later, unevenness in brightness due to the positional shift between the reflective surface and the lens element will not occur. In addition, when using a circular lens as shown in Figure 4,
This will result in some unevenness.

Next, in a preferred embodiment described in claim 2, the need for this positioning is omitted by making the pitch of the pair of reflective surfaces sufficiently smaller than the width of the lens element. The unevenness in brightness caused by the positional shift between the reflective surface and the lens element is at most a variation in whether one pair of reflective surfaces is effective or ineffective. Therefore, if the number of reflective surfaces per lens element is large, the rate of this variation will be reduced.Practically speaking, it is desirable that the brightness unevenness is at least within 50%, but to achieve this, the width of the lens element must be It is desirable that the distance be at least three times the distance between the reflective surface pairs.

More preferably, it is 5 to 10 times or more. In this way, if the width of the reflective surface pair is sufficiently small compared to the lens element, even when using a circular lens as shown in Figure 4, there will be almost no unevenness in brightness due to the misalignment of the reflective surface and the lens element. Does not occur.

In either case, it is preferable to provide a light shielding means 13 between each lens so that the light incident on one lens element does not enter an adjacent lens element after reflection and become stray light. This situation is shown in the plan view of FIG. 9(a) and the perspective view of FIG. 18. Black paint is sufficient for this.

In this imaging element, as shown in FIG. 15(a), the component reflected only on one side of the pair of reflective surfaces becomes stray light, causing a reduction in contrast. In a preferred embodiment described in claim 4, such stray light is removed by providing a light shielding surface 6 as shown in FIG. 15(1)).

The light shielding surface 6 is a thin black plate that absorbs light, and is placed perpendicular to the direction in which the reflective surface pairs are arranged. When the reflective surface group and the light shielding surface are in the same medium as shown in the figure, it is sufficient that the width d and the interval of the light shielding surface satisfy the relationship d≧D. This is because the components of the incident light whose angle of incidence is π/4 or more are cut, and
Since the reflection angle of the reflected light as shown in (a) for incident light of 4 or less is π/4 or more, this component is also cut 100%.

As shown in Fig. 13 (a), when the reflective surface group is composed of minute right-angle prisms formed on a transparent plate with a refractive index of J2 or more, θ. ==-' (1/n) However, n: Since most of the light incident on the prism surface is transmitted at a critical angle θ6 or less expressed by the refractive index, as shown in Figure 14, -n is applied to the lens. There is little reflection of light incident at an angle that satisfies sin (π/4−θ.). Therefore, even without a light shielding surface, stray light is considerably less than in the case of FIG. 15. However, since this limits the viewing angle of each lens element in the lens array, if the image position is closer to the lens array than position 8 in Fig. 16, an extremely dark portion of the image will be created between each lens. In order to avoid this, the image position must be placed at a position farther than position 8, such as position 9 in the figure.

In other words 2LtanlC≧T (However, L is the distance between the lens array and the image plane) You can set it so that

In any case, in this case, brightness unevenness with period T is likely to occur in the image, so care must be taken in determining the value of T. Although such unevenness is less likely to occur when the reflective surface is made of a gold R mirror or the like, it is better for T to be small from the viewpoint of lens aberration.

When using a prism in this way, even when installing a light-shielding surface, a light-shielding surface 7 that absorbs light is provided in a transparent medium with a refractive index of J2 or higher, as shown in FIG. 13(b). If it is optically bonded to a reflecting prism, the incident light will be refracted and become a ray of light at the critical angle θ, (<π/4), and considering the effect of stray light components being reflected on the medium surface,
It is sufficient that the width d of the light shielding surface and the interval satisfy the relationship d≧D/2, and the width can be made thinner than in the case of FIG. 15.

The above example shows the case where the light-shielding surface is placed just in front of the reflective surface group, but
It is also possible to place it elsewhere in the optical path. However, it is preferable to install the light-shielding surface on both the subject side and the image side when viewed from the group of reflective surfaces, and in order to prevent the light-shielding surface from creating uneven brightness in the image, it should be placed as far away from the subject and image as possible. Therefore, it is most preferable to place it immediately in front of the reflective surface group.

〔Example〕

Hereinafter, the present invention will be explained more specifically using Examples.

The embodiments shown in FIGS. 5 to 7 and 10 are claimed in claim 3 of the present invention.
This is an embodiment described in Claim 1 or 2 depending on how the pitch of the reflective surface pair is selected. In all cases, the reflective surface group 1 is formed as a prism row, and the prism surfaces are treated to increase reflection by metal vapor deposition.

The embodiment shown in FIG. 5 is one in which a lens array 6 and a prism row are integrally molded. Here, a reflective surface 5 is used to make the subject plane and image plane parallel, so that the image of point 2 is Get into position.

The embodiment shown in Fig. 6 uses a beam splitter with a half mirror surface 7 as a reflecting means.The beam splitter is used to separate the object side and the image side, and the object side and the image side are different from each other. Become vertical.

In the embodiment shown in FIG. 7, the lens array 4 and the beam splitter are integrated, and the object plane and the image plane are perpendicular to each other.

The embodiment shown in Fig. 8 is a comparative example in which lens arrays are provided separately on the image side and the subject side, and although images can be formed in principle, it is difficult to accurately align the axes of both lens arrays, and
This is not preferable because it tends to cause uneven brightness in the direction.

In the embodiment shown in FIG. 10, the lens array 4 and the reflective surface 5 are integrated.

When using a beam splitter as shown in Figures 6 and 7, the only light that forms an image is [light from the subject x beam splitter transmittance x reflectance], which is less than 10% of the light from the subject. It is. The embodiment shown in FIG. 11 is obtained by adding one more lens array and prism row to FIG. 6, and thereby obtains twice the brightness as in FIG. 6. By shifting the positions of the lens elements of both lens arrays in the X direction, it is also possible to reduce the uneven brightness that occurs in FIG. 6.

Next, FIG. 12(b) shows an example of a reflective surface group in which the light-shielding surface described in claim 4 is introduced, and FIG. 12(a) shows a combination of this and a lens array. Further, as shown in FIG. 9 (+), the light shielding means 13 between the lenses may be deeply cut to serve as a light shielding surface.

FIG. 17 shows an example in which the present imaging element is actually used, taking the type shown in FIG. 10 as an example. Using an imaging element component of the required length, a life-size image of the original 11 is captured by the image sensor 1.
This is an example of an image reading device that obtains an electrical signal by projecting the image onto 2.

〔Effect of the invention〕

The present invention has a configuration in which a lens array and a row of reflective surface pairs are combined, so that the imaging element of the present invention: (1) eliminates the troublesome axis alignment that was required with the conventional lens arrays (2) and (2); and (2) eliminates chromatic aberration from the lens. It has the property of branching.

Therefore, it is possible to construct a projection optical system that projects an image on a long line in one direction, has a compact and simple structure, and is easy to manufacture.

[Brief explanation of the drawing]

Figures 1 to 4 are explanatory diagrams for explaining the basic principle of the present invention, and Figures 5 to 7 are examples of the present invention.
) is a perspective view, (b) is a cross-sectional view perpendicular to the X-axis, and FIG. 8 is a comparative example. (a) is a perspective view, (b) is a cross-sectional view perpendicular to the X-axis, and FIG. FIG. 10 is a partial view of an embodiment of the present invention, in which (a) is a perspective view, (b) is a sectional view perpendicular to the X axis, and FIG. 11 is an embodiment of the embodiment of FIG. 6. This is an embodiment of the present invention in which another lens array and prism row are added to the above, and (a) is a perspective view, and (b) is a perspective view.
) is a sectional view perpendicular to the X-axis, Fig. 12 is a partial view of an embodiment of the present invention, Fig. 13 is a principle diagram showing the effect of the light shielding surface according to the present invention, and Fig. 14 shows a prism array as a reflective surface group. Fig. 15 is a principle diagram showing the effect of the light shielding surface according to the present invention; Fig. 16 is an explanatory diagram showing the use of a prism array as a reflective surface group; Fig. 17 is a perspective view showing an example of application of the present invention. , FIG. 18 is a partial diagram of an embodiment of the present invention, and FIG. 19 is an explanatory diagram showing the relationship between the lens array and the reflective surface group according to the present invention. 9 ・Position of subject (image) Imaging element Document image sensor Light-shielding member Patent applicant Mitsubishi Rayon Co., Ltd. Reflective surface group Subject) Image lens element Reflective surface Light-shielding surface Half mirror surface Position where a connected image can be obtained 'H2 diagram (b) Fig. 6 Fig. 3 Fig. 4 <a) (b) Fig. 7 Fig. 9 Fig. 10 (a) <b> w113 Fig.) In2 Fig. (a) (b) Fig. 12 Figure <b> 5th figure w116 figure 17 figure 1i18 figure wi19 figure

Claims (1)

[Claims] 1. A reflective surface group in which a large number of pairs of reflective surfaces forming a valley with an apex angle of π/2 are arranged in a direction perpendicular to the valley line where the reflective surfaces intersect; An optical element having a large number of arranged lens elements having the same focal length, characterized in that the width of the lens elements is a half-integer multiple of 1.5 or more of the spacing between the reflective surface pairs. Imaging element. 2. A reflective surface group in which a large number of pairs of reflective surfaces forming a valley with an apex angle of π/2 are arranged in a direction perpendicular to the valley line where the reflective surfaces intersect, and a group of reflective surfaces arranged parallel to this and each other at focal lengths. 1. An optical element having an equal number of lens elements, wherein the width of the lens element is three times or more the distance between the pair of reflective surfaces. 3. An imaging element comprising a light-shielding surface perpendicular to the arrangement direction of the pair of reflective surfaces arranged in front of the group of reflective surfaces of the optical component according to claim 1 or 2. 4. An optical element having at least one reflecting means parallel to the arrangement direction of the lens element and the pair of reflecting surfaces in the imaging element according to any one of claims 1 to 3.