JP3258097B2 - Planar split projection element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plane-divided projection device having an enlargement / reduction function used in a slit exposure type analog copying machine.

[0002]

2. Description of the Related Art A slit exposure type analog copying machine uses a projection element for projecting a copy on a reading line onto a photoreceptor. A surface-divided projection element represented by a rod lens array, which is an array, is conveniently used. Such a surface-divided projection element is a compact optical system, and has the advantage of being easy to assemble and adjust the focal length. There is a drawback that it does not become a plane division projection element.

[0003]

As described above, it is extremely difficult to provide an enlargement / reduction function with a plane division projection element such as a rod lens array, and development of a plane division projection element having an enlargement / reduction function is required. I have been waiting.

[0004]

SUMMARY OF THE INVENTION The present inventor has studied the purpose of developing a plane-splitting element having a function of enlarging and reducing an image, and as a result, has completed the present invention. to place, the two Dove prism, so the light reflection surface is outside, the assembly was double flop <br/> rhythm assembly plurality in symmetrical, straight as the light reflective surface facing And two types of convex lenses having different focal lengths are arranged on the light entrance / exit end faces of the Dove prism assembly linearly arranged. The ratio between the arrangement distance d of the convex lenses to be arranged and the focal length of the convex lens arranged on the light incident end side is equal to the ratio of the focal length of the convex lens arranged on the light exit end side. The surface-division projection element is characterized in that:

FIG. 5 shows a cross section of the Dove prism 3 used in the present invention. In hypotenuse of this double light dove prism which is incident with a corner α of the axis of the prism is refracted to the light reflecting surface, the light reflected by the light reflecting surface than hypotenuse of the light emitting surface side of the dove prism, the The light is emitted in the reverse direction at an angle α formed with the axis.

The angle between the oblique side and the bottom surface of the Dove prism is θ, and when this angle θ is large, the light emitted from the object surface is not reflected by the light reflection surface of the Dove prism, but becomes stray light directly emitted from the emission surface. And the contrast of the obtained image decreases. From such a viewpoint, it is preferable that the angle θ satisfy the condition of θ ≦ 90 ° −sin ⁻¹ (1 / n), where n is the refractive index of the material constituting the Dove prism.

The ratio a / b of the length b in the width direction of the Dove prism to the length a in the base direction in the axial direction satisfies the expression (1). Although it is preferable in terms of increasing the brightness, the overall image brightness is a
If / b is slightly smaller than [Equation 1], the image becomes brighter. Also,
The uniformity of the image depends sensitively on a / b, and the optimal value varies depending on the focal length of the lens to be used, the arrangement interval of the Dove prism assembly, and the like. It is preferable to determine an optimum value slightly smaller than the value of [1].

(Equation 1)

FIG. 4 is a perspective view of a Dove prism assembly used in the present invention. In FIG. 4, reference numeral 8 denotes a joining surface made of a black adhesive for joining two Dove prisms.

In a line imaging element constituted by a lens array, it is an essential condition that each unit forms an erect image in order to form a connected line image. However, since the condition of the erect image is sufficient if the condition is satisfied only in the line direction of the line imaging element, the present invention reduces the load on the lens by using the image inverting action of the Dove prism in the line direction, and reduces chromatic aberration. In addition, it succeeded in making the line imaging element easy to assemble. In the present invention, the image is inverted in the direction perpendicular to the line direction. However, if an erect image is required, the image may be inverted using a mirror and changed to an erect image.

FIG. 1 is a plan view showing an xz plane and an image forming mechanism of the surface-divided projection element of the present invention, FIG. 2 is a plan view showing the yz plane and an image forming mechanism, and FIG. It is the perspective view. Of the reference numerals in these figures, 1 is a convex lens provided at the light incident end of the dove prism assembly, 2 is a convex lens provided at the light output end, 3 is a dove prism, 4 is a light shielding member, and 5 is a light shielding member. The object plane 6 indicates an image plane. Object plane 5, image plane 6
Are located at positions separated by a focal distance from the respective convex lenses, an inverted image is formed in the y direction as shown in FIG.
In the direction, the erect image is formed by the action of the Dove prism 3 as shown in FIG.

To make the description easier to understand, a specific embodiment will be described. Two polymethyl methacrylate dove prisms having a base length of 20 mm, a base width of 5 mm, a height of 10 mm, and a hypotenuse angle of θ = 45 ° were joined with a black adhesive so that the top and bottom surfaces matched.
Four Dove prism assemblies, four convex lenses (A) having a focal length of F = 60 mm, and four convex lenses (B) having a focal length of f = 45 mm are prepared. The four Dove prism assemblies are shown in FIG. The light-shielding member 4 having a thickness of 6.6 mm was assembled between the Dove prism assemblies. Next, the convex lens (A) is cut into two 10mm x 20mm rectangles with the optical axis at the center, and the other two are cut into half of this, 10mm x 10mm. D = 20 mm, and the convex lens (B) is cut into a rectangle of 10 mm × 15 mm, and is arranged at the output side with an axial distance d = 15 mm.
This is a surface-division projection element of the present invention.

FIG. 1 shows the xz of the surface-divided projection element of the present invention.
The in-plane imaging mechanism will be described. First, the convex lens (A)
The intersection point between the optical axis of the single lens (A) included in the array element and the object plane 5 is set to 0, and the optical axis of the single lens (B) included in the array element and the image plane 6 are set to zero. Is 0 '.
Light emitted from the distance apart points x ₁ of x ₁ from the point 0 on the object surface 5 enters the convex lens (A), the optical axis by the action of the convex lens (A) (z
Axis) and is converted into parallel light having an angle of −tan ⁻¹ (x ₁ / F) (where F indicates the focal length of the convex lens (A)). Then, due to the action of the Dove prism, this light is converted into a parallel light that forms an angle tan ^-1 (x ₁ / F) with the optical axis, and the convex lens (B)
The image is formed at a distance x ₁ ′ = x ₁ × f / F from the point 0 ′ on the image plane 6 (where f indicates the focal length of the convex lens (B)).

That is, the image on the image plane has an origin 0 on the image plane.
Is formed as a reduced image of f / F times moved to the origin 0 'of the image plane. The distance between adjacent convex lenses is D (= 20m
m), d (= 15 mm) on the image plane side, and d / D = f / F (3/4 times), so that the reduced images projected by the adjacent convex lenses are shifted. Instead, the image is formed as a continuous image as shown in FIG.

FIG. 2 is a view for explaining an image forming mechanism on the yz plane of the plane division projection element of the present invention. Since the convex lens (A) and the convex lens (B) are used in tandem, the magnification becomes an inverted image of f / F (3/4 times) (see FIG. 3).

That is, for each projection element, (a) position-angle conversion by the lens (A), (b) angle inversion in the xz plane by the Dove prism, and (c) angle-position conversion by the convex lens (B) Inverted f / F images are obtained only in the y direction, and the distance between these images is reduced to f / F (d / D) times.
As a whole, a continuous inverted image of f / F times inverted can be obtained. Also, the main-plane split projection element can be used as an F / f-fold enlarged projection element by reversing the object plane and the image plane.

In the plane-divided projection device shown in FIG. 1, the optical axis of the convex lens on the image side is moved inward by d / 2 by the lenses at both ends with respect to the optical axis of the convex lens on the object side to project a reduced image. ing. As described above, the pitch of the projection side lens array is limited to the reduction length of the projected image of the surface division projection element of the present invention in which one set of the convex lens array and the array of the Dove prism assembly are combined. Therefore, as the number of arrays of the convex lens and the Dove prism assembly optical unit increases, the limit of the reduction magnification of the projection element also increases. On the other hand, as the number of arrays of the optical units is reduced, the effect of miniaturizing the device (shortening of the projection distance) by projecting by dividing the plane becomes thinner, so that the number of arrays cannot be reduced much.

FIG. 6 is a plan view of an xz plane of another example of the surface division projection element of the present invention. In this example, in order to improve the brightness of the image formed by the projection elements, the same array of Dove prism assemblies as those used in FIG. Instead of using a simple array of convex lenses, a convex lens in which a part of a single lens was cut out while changing its position little by little was used. More specifically, the focal length F of the convex lens 9 is 60 mm, the focal length f of the convex lens 10 is 40 mm, the distance D between the optical axes of the convex lens (A) of the convex lens array 9 is 12 mm, and the convex lens (B) of the convex lens array 10 is Assuming that the distance d between the optical axes is 8 mm, the reduction magnification of the projected image by this projection element is 2/3 and the enlargement magnification is 3/2.

FIG. 7 is a plan view showing another embodiment of the surface-divided projection element according to the present invention using eight Dove prism assemblies. The reduction magnification of this projection element is 87.5% (the magnification is 11%).
4%).

In the projection elements shown in FIGS. 1 and 6, the single lenses of the lens arrays 1, 2, 9, and 10 are arranged with a constant optical axis interval, which is an aspect of the present invention. Not the necessary condition of the divided projection element, but if the optical axis interval of the convex lens corresponding to the object plane side and the imaging plane side is equal to the ratio of the focal length of each convex lens, that is, the reduction, the enlargement magnification,
The interval may be different depending on the location.

The surface-divided projection device of the present invention is not a projection device capable of forming a reduced or enlarged image, which was impossible with a projection device using a rod lens array or a three-layer lens array conventionally used. This is a major feature in that the obtained point and that an image with less chromatic aberration can be formed.

[0021]

[Brief description of the drawings]

FIG. 1 is a plan view showing an image forming mechanism on an xz plane of a surface-division projection element of the present invention.

FIG. 2 is a plan view showing an imaging mechanism on the yz plane of the projection element of FIG. 1;

FIG. 3 is a perspective view showing an example in which the projection device of FIG. 1 is used as a sensor.

FIG. 4 is a plan view showing an optical transmission mechanism of a Dove prism.

FIG. 5 is a perspective view of a Dove prism assembly.

FIG. 6 is a plan view of an xz plane of another example of the plane division projection element of the present invention.

FIG. 7 is a plan view of an xz plane of another example of the surface division projection element of the present invention.

[Explanation of symbols]

1, 2, 9, 10… Convex lens array 3… Dove prism 4… ………… Shielding body 5 …………… Object surface 6 …………… image plane 7 ..................... shielding plate 8 ..................... optical axis Tc ..................... conjugate length of Dove prism joining surfaces 11 and 12 ............... lens

Claims (1)

(57) [Claims] 1. A with two Dove prism, so the light reflection surface is outside, the assembly was Dove prism assembly plurality symmetrically type, arranged in a straight line as the light reflecting surface face each other The arrangement interval D (distance between lens axes) of a convex lens in which two types of convex lenses having different focal lengths are arranged on the light incident end side on the light entrance / exit end faces of the linear Dove prism assembly. The ratio of the arrangement distance d (inter-lens axis distance) of the optical axes of the convex lenses disposed on the light exit end side is determined by the focal length of the convex lens disposed on the light incident end side and the convex lens disposed on the light exit end side. A plane-segmented projection element, which is disposed so as to be equal to a focal length ratio.