JPH06118340A - Image forming element - Google Patents

Abstract

PURPOSE:To obtain an image forming element which can form an erect unmagnification image by providing convex lenses whose focal distances are equal on the light incident/emitting end faces, respectively of an assembly of a tab prism. CONSTITUTION:A tab prism 3 is formed with two pieces of tab prisms in which a triangle columnar rectangular prism is used as the light reflecting surface, and these two tab prisms 3 are joined to the light reflecting surface outside. Convex lenses 1 and 2 are convex lenses whose focal distances are equal and provided on the light incident/emitting surfaces of an assembly of the tab prism 3. By setting an angle theta made by an oblique side of the tab prism 3 and an edge line of the rectangular prism as large as possible, a formed image scarcely causing a chromatic aberration is obtained. In this regard, as for the angle theta, it is desirable that a relational expression theta<=90 deg.-sin<-1> (1/n) is satisfied, wherein (n) is a refractive index of a base material for constituting the tab prism 3. Also, as for a ratio a/b of length (b) in the width direction of the tab prism 3 and length (a) in the axial direction, a bright formed image is obtained by satisfying a necessary condition prescribed by the expression.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a facsimile, a copying machine,
The present invention relates to an image forming element that can be effectively used as an image forming element such as an LED printer, and particularly to an image forming element that can form an erecting equal-magnification image.

[0002]

2. Description of the Related Art Conventionally, a compact image forming element for image transmission has been used in a copying machine, a facsimile, an LED printer, and a liquid crystal printer, and examples thereof include the following.

Gradient index type rod-shaped lens element array; a rod-shaped lens element array in which a large number of gradient-index type rod-shaped lenses whose refractive index decreases from the central axis of the rod-shaped lens toward the outer periphery is arranged in parallel is used as an imaging element. thing.

Spherical lens array: There is a spherical lens array using a multilayer plate in which three or more sheets each having a spherical lens portion formed on a flat plate surface are used as an imaging element, and these inventions are disclosed in Japanese Patent Publication No. 49-8893. It is disclosed in JP-A-57-66414 and JP-A-57-104923.

Tab prism array; JP-A-56-117
201, JP-A-56-126801, JP-A-56-140301, and JP-A-56-14900.
No. 2, JP 60-254018 A, JP 6
0-254019, JP60-254020, JP61-210319, JP62-
Japanese Patent Laid-Open No. 91902 and Japanese Patent Application Laid-Open No. 62-201417 disclose an array using an image-forming element capable of forming an erecting equal-magnification image in which a tab prism and a lens are combined.

[0006]

An image forming element using a tab prism has a simple structure and uses an image forming mechanism by image inversion, and has an advantage that an image with a small chromatic aberration can be obtained. However, there is a drawback that the obtained image is an inverted unity-magnification image, and the emergence of an image-forming element using a tab prism capable of forming an erecting unit-size image is awaited.

[0007]

SUMMARY OF THE INVENTION The inventors of the present invention have studied the present invention as a result of the study for the purpose of developing an imaging element capable of forming an erecting equal-magnification image with an imaging element using a tab prism. completed.

The gist of the present invention is to provide a tab prism (I) in which the light reflecting surface of the tab prism is composed of a plurality of right-angled prisms having parallel ridges parallel to the longitudinal axis of the tab prism. The two are formed as a tab prism (I) assembly in which the array surfaces of the right-angle prisms are joined to the outside, and a convex lens having the same focal length is provided on the light input and output end faces of the tab prism assembly (I). The imaging elements are characterized in that they are respectively arranged.

In a line imaging element using a lens array, it is a necessary condition for the imaging element alone to form an erect image when it is used as a line imaging element by arranging the imaging elements alone in a line. In the line imaging element using the tab prism that has been developed, it has been devised so that an equal-magnification erect image can be formed only on the line axis. The object can be achieved by devising the structure of the light reflecting surface of the tab prism (I) to be configured.

The imaging element of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a structure of an example of an image forming element of the present invention. In the figure, reference numeral 3 denotes two tab prisms (A) each having a light reflection surface provided with an array of triangular prism right-angle prisms. These two tab prisms (I) have a black adhesive with the light reflection surface as an outer side. It is joined at 5. 1 in the figure
Reference numerals 2 and 2 are convex lenses having the same focal length provided on the light entrance and exit surfaces of the tab prism (I) assembly. 6 is an object plane, and 7 is an image.

By forming the angle θ formed by the hypotenuse of the tab prism (I) and the ridge of the rectangular prism used in the present invention as large as possible, an image with less chromatic aberration can be obtained, but this angle θ is too large. Then, the light emitted from the object surface will not be reflected by the right-angle prism surface of the tab prism (I). From this point of view, it is preferable that the angle θ satisfies θ ≦ 90 ° −sin ⁻¹ (1 / n) ... N satisfies the relational expression that the refractive index of the material forming the tab prism (I).

The length b of the tab prism (I) in the width direction is
The ratio a / b between the length a and the axial length a satisfies the requirement defined by [Equation 1], so that a bright image can be formed.

[Equation 1]

FIG. 2 is a plan view for explaining the image forming mechanism of the image forming element shown in FIG. 1, and FIG. 2A is an explanatory view of the image forming mechanism of the yz plane of the image forming element. The figure (b) shows x of the imaging element.
It is explanatory drawing of the imaging mechanism of z surface.

The light emitted from the center point 0 of the object plane in FIG. 2 (a) is divided by the convex lens 1 into light ray components parallel to the axis of the tab prism (I), and enters the tab prism (I), The light is reflected twice by the right-angle prism surface, is converted into parallel light by its hypotenuse, is condensed by the convex lens 2, and forms an image at a point 0 ′ during image formation.
On the other hand, the point y ₁ on the object plane is decomposed into parallel rays by a convex lens,
Then, the hypotenuse of the tab prism (A) on the light incident side becomes light directed toward the right-angle prism of the tab prism (I), and after being reflected twice on the inner surface of the prism, the hypotenuse of the tab prism (I) on the light emitting side. Is converted into light emitted in the direction of the convex lens 2 and is condensed by the convex lens 2 to form an erecting equal-magnification image at a point y ₁ ′ on the image formation. That is, an erecting equal-magnification image can be formed by utilizing twice reflection of the rectangular prism 4 provided on the light reflecting surface of the tab prism (I).

FIG. 2B is an explanatory diagram of the image forming mechanism on the xz plane of the image forming element shown in FIG. The light emitted from the center point 0 on the object is decomposed by the convex lens 1 provided on the light incident surface of the imaging element, and refracted at the hypotenuse of the tab prism (I) on the light incident surface side.
The light becomes parallel light, travels in the direction of the right-angle prism, is reflected twice on the inner surface of the right-angle prism, and is bent as a parallel light ray at the hypotenuse of the tab prism (I) on the light emission surface side, and is condensed by the convex lens 2 to form an image. Image at point 0 '.

FIG. 2B is an explanatory view of the image forming mechanism on the xz plane of the image forming element of FIG. The point 0 on the object plane is split by the convex lens 1 and is converted into parallel light in the direction of the right prism installation surface of the tab prism (I) at the hypotenuse side of the light entrance surface of the two tab prisms (I). After being reflected twice on the inner surface, the optical path is changed on the hypotenuse side of the tab prism (I) on the light emitting surface side, the light is condensed by the converging convex lens 2, and 0 on the image corresponding to the point 0 on the object plane is formed. 'Image to a point. On the other hand, the point x ₁ on the object plane is split by the convex lens 1 on the light incident surface side, and becomes parallel light to the installation surface side of the right angle prism of the tab prism (I) due to the hypotenuse of the two tab prisms (I). After being reflected twice on the inner surface, the optical path is changed by the hypotenuse of the tab prism (I), condensed by the condenser lens 2, and imaged at a point x ₁ 'on the image formation corresponding to x ₁ on the object plane. . That is, an erecting equal-magnification image can be formed.

FIG. 3 is a plan view showing an optical path on the xy plane of the image forming element for explaining the image forming action of an erecting equal-magnification image by the right-angle prism of the image forming element of the present invention. Light entering the convex lens ₁ from the point x _{1 on the} object plane 6 is first converted into parallel light which forms an angle −tan ⁻¹ (x ₁ / f) with the optical axis (z axis) by the action of the lens 1 (however, f represents the focal length of lenses 1 and 2).
Then, by the action of the tab prism (I), this light is converted into parallel light forming an angle tan ^-1 (x ₁ / f) with the optical axis, and by the action of the lens 2, it is converted to a point of coordinate x ₁ on the image plane. Focus. x ₁ y
The coordinates are saved as described below, so the points on the object plane are eventually
The light emitted from x ₁ is focused at the same position as viewed from the point 0 on the image plane, that is, the position of an erecting equal-magnification image.

Further, in FIG. 3, the same x as the point 0 on the object plane
The light emitted from the coordinate point y1 is converted by the convex lens 1 into parallel light whose x component of the traveling vector is zero, enters the transparent member 3, and is reflected by the right-angled prism 4.
By the action, the sign of the y component of the traveling vector is inverted and the sign is inverted, and the light exits the transparent member 3 and reaches the convex lens 2. Figure 4
Since the vector of the light emitted from the transparent member 3 does not have an x component by the action of, the discussion of the above-mentioned x-coordinate applies to the y-coordinate as it is, and this ray is acted by the lens 2 to erect equal-magnification on the image plane. It can be seen that the image is focused on the point with the position coordinate y ₁ .

Also, a point x1 having the same y coordinate as the point 0 on the object plane
The light emitted from is converted by the convex lens 1 into parallel light having a zero y component of the traveling vector, converted into the direction of the right-angled prism by the hypotenuse of the tab prism (I), reflected in the right-angled prism, and reflected by the tab prism (I ), After passing through the inside of the tab prism, light is directed toward the convex lens 2 on the hypotenuse side of the light exit side, is condensed by the convex lens 2, and is a point on the image forming point corresponding to the point x ₁ on the object plane.
Form an image at x ₁ '. During this time, the ray vector does not generate any other y component, so it can be seen that the points 0 and x ₁ on the object are imaged on the coordinates of the corresponding points 0 ′ and x ₁ ′ on the image formation.

As described above in detail, the above-described phenomenon can be applied to the point of arbitrary coordinates on the object plane in the image forming element of the present invention, and the image is an erecting equal-magnification image of the object. That is, an erecting equal-magnification image is formed by the actions of (1) position-angle conversion by the convex lens 1, (2) angle conversion by the rectangular prism surface of the tab prism (I), and (3) angle-position conversion by the convex lens 2. You can do it.

This means that the positional information between the convex lens 1 and the convex lens 2 does not substantially change, and this brings out the optical stability of the imaging element of the present invention. That is, even if the positions of the convex lens 1 and the convex lens 2 in FIG. 2 (b) are slightly deviated in the x-axis direction or the y-axis direction, they only appear as translation of the image, and the quality of the image itself is completely different. Absent. The most problematic point in assembling a plurality of image-forming elements of the present invention into a lens array is that fluctuations in the pitch between the lenses are integrated in the arrangement direction of them and cause a non-negligible optical axis shift. As described above, the image-forming element of the present invention has a feature that the optical axis shift is unlikely to occur, and has a great feature that when the line image-forming element is made, the optical axis shift in the array direction is unlikely to occur. There is.

FIG. 4 is a perspective view showing an example of a line image forming element in which a plurality of image forming elements of the present invention are linearly coupled.

FIG. 5 is a plan view of a linear image-forming element in which a plurality of image-forming elements according to the present invention and the rectangular prism portions of the tab prism (I) are arranged so as to mesh with each other. This line image forming element is a meshing portion of the image forming elements, and in order to prevent light from being mixed due to leakage of light from an adjacent image forming element, a light shielding portion may be formed on the meshing surface of the image forming elements. preferable.

FIG. 6 is a plan view showing an example of a line image-forming element formed by joining a plurality of image-forming elements according to the present invention to the ridges of the rectangular prism.

FIG. 7 is a plan view showing an example of a line image forming element in which a large number of image forming elements of the present invention are arranged so that their right-angle prism surfaces are in the vertical direction.

FIG. 8 is a perspective view showing another example of the imaging element of the present invention, in which the convex lenses 1 and 2 of the imaging element of FIG. 1 are replaced by a combination of cylindrical lenses 9 and 11 and 10 and 12. FIG. 3 is a perspective view showing an example, and an image forming mechanism of this image forming element forms an erecting equal-magnification image by the same mechanism as that shown in FIG. 2. Although this type of imaging element uses a slightly increased number of parts, when forming a line imaging element array, the cylindrical lenses 11 and 12 can be respectively used as one common cylindrical convex lens as shown in FIG. As a result, it is possible to prevent the image shift of the image forming element assembly in the y-axis direction from occurring easily, and the cylindrical convex lens.
By changing the focal lengths and positions of 11 and 12, there is an advantage that the viewing angle (aperture angle) in the y-axis direction can be changed, and the functions of enlarging and reducing can be provided.

[0028]

The imaging element of the present invention is a tab prism (I).
2 with a parallel array of right-angle prisms
On the other hand, by arranging the right-angled prism array surface so as to be on the outer side, it was possible to obtain an image-forming element capable of forming an erecting equal-magnification image, which was considered impossible with the tab prism in the past. Yes, its utility value is extremely high.

[0029]

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of an imaging element of the present invention.

2 is a plan view showing an image forming mechanism of the image forming element of FIG. 1. FIG.

3 is a plan view showing an xy plane image forming mechanism of the image forming element of FIG. 1. FIG.

FIG. 4 is a perspective view of a line image forming element in which a large number of image forming elements of FIG. 1 are linearly combined.

FIG. 5 is a plan view showing an example of a coupled state of the line coupling element of FIG.

FIG. 6 is a plan view showing another example of a combined state of the line imaging element of FIG.

FIG. 7 is a plan view showing another example of a line image forming element in which a plurality of image forming elements of FIG. 1 are combined by changing the connection state.

FIG. 8 is a perspective view showing another example of the imaging element of the present invention using a cylindrical convex lens as a convex lens.

9 is a perspective view showing an example of a line image forming element in which a large number of image forming elements of FIG. 8 are connected in a line.

[Explanation of symbols]

 1, 2 ……………… Convex lens 3 …………………… Tab prism (I) 4 …………………… Right angle prism 5 …………………… Tab prism (I) Bonding surface 6 …………………… Object surface 7 …………………… Imaging surface 9,10,11,12 ………… Cylindrical convex lens

Claims (1)

[Claims] 1. A right-angle prism array comprising two tab prisms (I) in which a light-reflecting surface of the tab prism is constituted by a plurality of parallel prisms each having a ridge line parallel to a longitudinal axis of the tab prism. An image forming element characterized in that convex lenses having the same focal length are respectively provided on the light input and output end faces of an assembly of tab prisms (I) joined such that their surfaces are on the outside.