JPH03247157A - Picture reader - Google Patents

Abstract

PURPOSE:To eliminate the effect of color aberration and to improve the image forming performance by forming plural color separation layers with different color separation characteristic via a transparent part to a reflecting face of an optical path separation mirror and arranging plural line image sensors on the image face to which a light reflected in a reflecting face of the optical path separation mirror is led. CONSTITUTION:Three layers of dichroic mirror faces P, Q, R as color separation layers are laminated onto a reflection face 3b placed to an image face 8 of an optical path separation mirror 3 as multi-layer structure. A focal distance is prolonged in the order of B, G and R light by forming each layer in this way and the image forming optical path length is adjusted, the position deviation of the optimum image face for each wavelength caused by the color aberration is corrected and the lights are all formed on a same face and the image forming performance is much improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image reading device 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 Several specific examples of conventional image reading apparatuses will be described. 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, in which an original 10 is placed as shown in FIG. An optical path splitting mirror 12 having two dogleg-shaped reflecting surfaces 12a and 12b is disposed below the contact glass 11, and on the optical path in front of the light reflected by the upper reflecting surface 12a. , a lens array 13 and a roof mirror array 14 are provided. 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, the light from the original 10 is reflected by the reflective surface 12a, 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 dichroic mirror for color separation. Two mirrors 15 used as
16, it is possible to perform color separation and generate three light beams for light detection. 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,
point M) and long wavelength (λb=656.27 nm) light fd
! fB (actual MA in the figure), there is a difference in focal length because the wavelength is different, and the position of the image plane is different, that is, the image plane position of ray A is higher than the image plane position of ray B. Becomes shorter. 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 separating mirror. In the image reading device, a light source for document illumination is provided, a plurality of color separation layers having different color separation characteristics are formed on the reflection surface of the optical path separation mirror via a transparent member, and the reflection surface of the optical path separation mirror A plurality of rows of line image sensors were arranged on the image plane to which the reflected light was guided.

In addition, in the image reading device, a light source for document illumination is provided, and a plurality of color separation layers having different color separation characteristics are provided on the object side reflective surface and the image side reflective surface of the optical path separation mirror via a transparent member. A plurality of line image sensors were arranged in layers on an image plane to which light reflected by the reflective surface of the optical path separation mirror was guided.

Therefore, by forming color separation layers with mutually different color separation characteristics on the reflective surfaces of the optical path separation mirrors, the positional deviation of the image planes for each wavelength caused by chromatic aberration is corrected, and the image planes all become the same plane. An image is formed on the image plane, and the corrected information after color separation can be read by a plurality of line image sensors formed at the position of the image plane.

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 image reading device, on the reflective surface 3b of the optical path separation mirror 3 located on the image plane 8 side, there is a multilayer structure in which dichroic mirror surfaces P, Q, and R are laminated in three layers as color separation layers. . FIG. 2 shows an enlarged view of the dichroic mirror, in which the dichroic mirror surfaces P, Q, and R are formed through thin glass plates 17a and 17b as transparent members.

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 of B light, G light, and R light becomes longer in the order of wavelength dependence of the refractive index shown in FIG. 9, which was explained in the prior art, and the imaging optical path length can be adjusted. As a result, it is possible to correct the positional deviation of the optimal image plane for each wavelength caused by chromatic aberration, and to form all images in the same plane, 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 the dichroic mirror surface P for R light by a vacuum evaporation method, etc., 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. can be created by forming a dichroic mirror surface R for B light using a vacuum evaporation method or the like.

Moreover, on the image plane 8 to which the light reflected by the reflection surface 3b of the optical path separation mirror 3 is guided, line image sensors 18 consisting of a plurality of rows are arranged. Therefore, the line image sensor 18 can detect the light that is imaged by the reflective surface 3b of the optical path separation mirror 3 while correcting the positional shift on the image plane 8 for each wavelength caused by chromatic aberration. This makes it possible to read the corrected information after color separation.

As the line image sensor 18, there is no need for a color image sensor, and it is sufficient to arrange multiple rows of identical monochrome line image sensors.
Accordingly, the sensor can be manufactured easily. Also, in this case,
Since the sensor surfaces are formed on the same plane, high-quality images can be read without deterioration in resolution even in such cases.

Note that as the document reading light source 19, a fluorescent tube, a halogen lamp, an LED light source, or the like can be used. Also,
The light emitted from the document reading light source 19 is irradiated onto the surface of the document 21 placed on the object surface 2 of the document contact glass 2o.

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.

Also in this case, by arranging the line image sensor 18 consisting of a plurality of rows, it becomes possible to read the corrected information after color separation.

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.

Also, in the case of this embodiment, as in the first embodiment and the second embodiment described above, by arranging a plurality of rows of line image sensors 18, it is possible to read the information after color separation. It becomes possible.

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 an image reading device comprising an aperture plate disposed between the lens array and the optical path separating mirror, a plurality of color separation layers having different color separation characteristics from each other are provided on the reflective surface of the optical path separating mirror via a transparent member. layered,
Since multiple rows of line image sensors are arranged on the image plane to which the light reflected by the reflective surface of the optical path splitting mirror is guided, the positional shift of the image plane for each wavelength caused by chromatic aberration can be corrected. All images can be formed on the same image plane, which makes it possible to eliminate the effects of chromatic aberration and improve imaging performance. The corrected information after color separation can be read using a line image sensor.

[Brief explanation of drawings]

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, 18... Line image sensor, 19... Light source for document illumination, P, Q
, R...color separation layer (-) d! Figure decay length (in)

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, which are arranged between the array and the lens array, a light source for illuminating the original is provided, and the reflection surface of the optical path separation mirror is provided with color separation characteristics that are different from each other. A plurality of different color separation layers are formed via a transparent member, and a plurality of line image sensors are arranged on an image plane to which light reflected by the reflection surface of the optical path separation mirror is guided. image reading device. 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 arranged between the diaphragm plate and an optical path separation mirror, a light source for document illumination is provided, and A line image sensor is provided in which a plurality of color separation layers each having different color separation characteristics are formed via a transparent member, and a plurality of rows are formed on an image plane to which light reflected by the reflection surface of the optical path separation mirror is guided. An image reading device characterized in that: