JPH03135509A - Lif-size image forming element - Google Patents

Abstract

PURPOSE:To correct a shift in the position of a picture plane of each wavelength generated due to a chromatic aberration and to form all picture planes on the same surface by forming color separating layers which have mutually different color separation characteristics on the reflecting surface of an optical path separation mirror. CONSTITUTION:The life-size image forming element consists of a lens array 4 wherein lenses are formed successively, a roof mirror array 6 wherein roof type reflecting surfaces are formed successively at the array pitch of the lens array 4, an aperture plate 9 arranged between the roof mirror array 6 and lens array 4, and the optical path separating mirror. In this case, plural color separating layers P, Q, and R which have mutually different color separation characteristics are formed on the reflecting surface 3b of the optical path separating mirror across transparent members. Consequently, position shifts of picture planes by wavelengths due to the chromatic aberration are corrected to form all the picture planes on the same surface. Consequently, the influence of the chromatic aberration is removed to improve image forming performance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a 1-magnification imaging element used in an imaging optical system of a document reading section of a copying machine, facsimile machine, image scanner, or the like.

BACKGROUND OF THE INVENTION Conventional equal-magnification imaging elements will be explained using some specific examples. First, as a first conventional example, there is a roof mirror lens array 1 as shown in FIG. This is because the light from the object plane 2 is reflected by the upper reflective surface 3a of the optical path separation mirror 3, and then passes through each lens 5 in the lens array 4, and then passes through the left and right roofs of the roof mirror array 6, which face each other. After being reflected once each time (total of 2 times) by the mold reflecting surface 7, it passes through the same lens 5 of the lens array 4 again, and this time is reflected by the lower reflecting surface 3b of the optical path separation mirror 3. It is imaged on an image plane 8 conjugate to the object plane 2,
In this way, the image is read. Note that a diaphragm plate 9 as shown in FIG. 7 is disposed between the lens array 4 and the roof mirror array 6.

In this case, an erect real image is formed in both the array direction (Y direction) and orthogonal direction (X direction) of the lens array 4 and the roof mirror array 6, and in particular, an erect equal-magnification image is formed in the Y direction. The necessary width is covered by overlapping images obtained by one lens array 4 and one roof mirror array 6 in the Y direction.

Further, since the arrangement pitches of the lens array 4, the aperture plate 9, and the roof mirror array 6 are almost the same, the light amount distribution of each lens 5 is almost the same.

Next, as a second conventional example, there is a multicolor copying apparatus disclosed in Japanese Utility Model Application Publication No. 58-40757.

As shown in FIG. 10, an optical path separation mirror 12 having two dogleg-shaped reflective surfaces 12a and 12b is disposed below a contact glass 11 on which a document 1o is placed. A lens array 13 and a roof mirror array 14 are arranged on the optical path in front of the light reflected by the upper reflecting surface 12a. Furthermore, mirrors 15 and 16 are arranged on the optical path between the lens array 13 and the lower reflective surface 12b. In this case, manuscript 10
After being reflected by the reflective surface 12a, the light passes through the lens array 13, is reflected by the roof mirror array 14, passes through the lens array 13 again, and passes through the two dichroic mirrors used as color separation dichroic mirrors. mirror 1
Color separation is performed by 5°16, and the light can be detected as three light beams. Incidentally, FIG. 11 shows the relationship between the wavelength range and reflectance of the mirrors 15 and 16 and the reflecting surface 12b.

Problems to be Solved by the Invention First, let's take a look at the first conventional example. FIG. 9 shows the dispersion (wavelength dependence of refractive index) of the materials of the individual lenses 5 constituting the lens array 4. This indicates that the shorter the wavelength, the higher the refractive index and the shorter the focal length. Therefore, in a device having such lens characteristics, for example, as shown in FIG.
Light ray A with a short wavelength (λa = 486.13 nm) (in the figure,
Since the wavelengths of the point # and the long wavelength (λb = 856.27 nm) ray B (solid line in the figure) are different, there is a difference in focal length, and the position of the imaging plane is different, i.e. , the image plane position to the light ray becomes shorter than the image plane position of the light ray B. Since the optimum imaging plane is different in this way, when the same imaging plane is used, the imaging performance will differ depending on the wavelength.

In order to eliminate this phenomenon, as shown in Figure 8,
This is corrected by using a plurality of lens arrays 4 (in this case, two lenses) stacked one on top of the other, but in this case, there is a problem that the configuration becomes complicated and the cost increases.

In addition, in the case of the second conventional example, since the dichroic mirrors (15, 16) for color separation are arranged spatially discretely, the difficulty of position adjustment increases, or the dichroic mirrors (15, 16) for color separation become difficult to adjust. There is a problem in that there is a large difference in the imaging position of each color.

Means for Solving the Problems Therefore, in order to solve such problems, the present invention provides a lens array in which a plurality of lenses are successively formed;
A roof mirror array in which a plurality of roof-shaped reflective surfaces are successively formed at the arrangement pitch of the lens array, a diaphragm plate disposed between the roof mirror array and the lens array, and an optical path separation mirror. In the same-magnification imaging element, a plurality of color separation layers having mutually different color separation characteristics were formed on the reflective surface of the optical path separation mirror with a transparent member interposed therebetween.

In addition, in the equal-magnification imaging element, a plurality of color separation layers having different color separation characteristics were formed on each of the object surface side reflection surface and the image surface side reflection surface of the optical path separation mirror via a transparent member.

Therefore, by forming color separation layers with different color separation characteristics on the reflective surface of the optical path separation mirror, the positional shift of the image plane for each wavelength caused by chromatic aberration can be corrected and all images can be placed on the same plane. It becomes possible to form an image.

Embodiment A first embodiment of the present invention will be explained based on FIGS. 1 and 2. Note that the same reference numerals are used for the same parts as in the conventional example (see FIG. 6).

In the roof mirror lens array, the optical path separating mirror 3
on the reflective surface 3b located on the image plane 8 side.

Dichroic mirror surfaces P and Q as color separation layers.

It has a multilayer structure in which three layers of R are laminated. FIG. 2 shows an enlarged view of the dichroic mirror, in which the dichroic mirror surfaces P, Q, and R are mutually connected to the thin glass 1 as a transparent member.
7a and 17b.

For example, if the light is to be separated into three color lights: R (red), G (green), and B (blue), dichroic mirrors should be stacked in order, starting with the dichroic mirror that reflects the short wavelength region where the focal length is shortened due to chromatic aberration. The dichroic mirror surface R of the top layer is for B reflection, the dichroic mirror surface Q of the middle layer is for G reflection, and the dichroic mirror surface P of the bottom layer is
are set to be R reflection (or total reflection mirror such as AQ, Ag, etc.).

By forming each layer in this way, the focal length becomes longer in the order of sunlight, G light, and R light, from the relationship of the wavelength dependence of the refractive index shown in FIG. As a result, it is possible to correct the positional deviation of the optimum image plane for each wavelength caused by chromatic aberration, and to form all images in the same plane, thereby further improving the imaging performance.

In addition, as a method for forming each dichroic mirror surface P, Q, R, first, on the reflective surface 3b of the optical path separation mirror 3,
After forming a dichroic mirror surface P for R light by a vacuum evaporation method or the like, a thin glass 17a is bonded, a dichroic mirror surface Q for G light is formed by a vacuum evaporation method, etc., and then a thin glass 17b is bonded. It can be created by forming a dichroic mirror surface R for sunlight using a vacuum evaporation method or the like.

Next, a second embodiment of the present invention will be described based on FIG. In the first embodiment described above, the dichroic mirror surface P as a color separation layer is provided on the reflection surface 3b on the image plane side of the dogleg-shaped optical path separation mirror 3.

In this case, dichroic mirror surfaces P, Q, and R of a similar configuration are also formed on the reflecting surface 3a of the flat optical path splitting mirror 3. Therefore, in this case, You can also get the same effect.

Next, a third embodiment of the present invention will be described based on FIG. 4. Here, dichroic mirror surfaces P, Q, and R are provided as color separation layers on both reflective surfaces 3a and 3b on both the object plane 2 side and the image plane 8 side of the dogleg-shaped optical path separation mirror 3.
was formed.

Figure 5 shows the imaging performance (MTF) of the roof mirror lens array when the horizontal axis (X) is the amount of defocus on the object plane and the vertical axis (Y) is the amount of defocus on the image plane. be. In this case, the relationship on the Y=X line in the figure maintains the same magnification relationship, and the deterioration in performance is small. Therefore, it is possible to improve the imaging performance by making the distances between the object plane 2 and the image plane 8 of the optical path separation mirror 3 equal, and furthermore, dichroic mirrors are formed on the object plane 2 side and the image plane 8 side, respectively. P, Q
.

By forming R symmetrically, imaging performance can be further improved.

Effects of the Invention The present invention provides a lens array in which a plurality of lenses are continuously formed, a roof mirror array in which a plurality of roof-shaped reflective surfaces are continuously formed at the arrangement pitch of the lens array, and this roof mirror array. In the equal-magnification imaging element, which includes an aperture plate and an optical path separation mirror, which are arranged between the lens array and the optical path separation mirror, color separation layers having different color separation characteristics from each other are provided with transparent members on the reflection surface of the optical path separation mirror. Since multiple layers are formed through the chromatic aberration, it is possible to correct the positional shift of the image plane for each wavelength caused by chromatic aberration and form all images on the same plane.This eliminates the effects of chromatic aberration and improves imaging performance. It is possible to improve this.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention, FIG. 2 is a side view showing an enlarged view of the color separation layer formed on the optical path separating mirror, and FIG. 4 is a block diagram showing the third embodiment of the present invention, FIG. 5 is a characteristic diagram showing the imaging performance of the roof mirror lens array, and FIG. 6 is the first embodiment. Fig. 7 is a side view of the device, Fig. 8 is a side view showing the case where two lens arrays are used, and Fig. 9 is a characteristic diagram showing the wavelength dependence of the refractive index. , FIG. 10 is a side view showing the second conventional example, and FIG.
Figure 1 is a characteristic diagram showing the spectral performance of the dichroic mirror. 2... Object surface, 3a, 3b... Reflective surface, 4... Lens array, 5... Lens, 6... Roof mirror array, 7... Roof type reflective surface, 8... Image surface , 9... Aperture plate, 17a, 17b... Transparent member, P, Q, R...
color separation layer

Claims (1)

[Claims] 1. A lens array in which a plurality of lenses are continuously formed, a roof mirror array in which a plurality of roof-shaped reflective surfaces are continuously formed at the arrangement pitch of this lens array, and this roof mirror. In a 1-magnification imaging element consisting of an aperture plate and an optical path separation mirror disposed between the array and the lens array, transparent color separation layers having different color separation characteristics are provided on the reflective surface of the optical path separation mirror. A 1-magnification imaging element characterized in that a plurality of layers are formed using members. 2. A lens array in which a plurality of lenses are continuously formed, a roof mirror array in which a plurality of roof-shaped reflective surfaces are continuously formed at the arrangement pitch of this lens array, and this roof mirror array and the lens array. In a 1-magnification imaging element consisting of an aperture plate and an optical path separation mirror disposed between the diaphragm plate and an optical path separation mirror, the reflection surface on the object plane side and the reflection surface on the image plane side of the optical path separation mirror have color separation characteristics that differ from each other. A 1-magnification imaging element comprising a plurality of different color separation layers formed with transparent members interposed therebetween.