JPH0396063A - Image reader - Google Patents

Abstract

PURPOSE:To use a color separation element comparatively easily manufactured by arranging the color separation element in which a dichroic mirror and a total reflection mirror are laminated via a transparent layer between an image pickup sensor having plural line sensors corresponding to each separation color and an image forming lens system. CONSTITUTION:The color separation element 8 is arranged between an image forming lens 6 and a CCD line sensor 7. At the color separation element 8, after the total reflection mirror M is formed on one end face of a plate prism 9, the transparent layer 10 is formed, and furthermore, the dichroic mirror D is formed on the layer. Two line sensors having color filters corresponding to two colors separated with the color separation element 8 are provided at the CCD line sensor 7, which read the dichroic images of a color original 2, respectively. In such a way, manufacturing can be comparatively simply performed compared with a case where plural thin transparent layers 10 are laminated and plural dichroic mirrors D are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image reading device, and more particularly, to an improvement of a color separation element of a device that separates and reads a color image. Conventional technology> Generally speaking, a device for color-separating and reading a color image is provided with a dichroic beam splitter behind an imaging lens system, and the dichroic beam splitter separates the color image into three primary colors. A widely known method is to emit light in different directions and read each of the three primary colors using separate sensors. However, in this type of device that separates the three primary colors into three directions, each dichroic surface and the corresponding image sensor are precisely aligned with each other to determine the focal point. It is necessary to correct the magnification, warpage of the sensor surface, etc., and complicated adjustment work must be performed for each of the three primary colors, resulting in high costs.

Therefore, as a device that can simplify the positioning of the sensor as described above, a plurality of gicroic films (dichroic films) are laminated with a transparent layer interposed therebetween, as disclosed in, for example, Japanese Patent Application Laid-Open No. 62-234106. A beam splitter has been proposed in which the colors are separated into parallel light beams, and the light is received by an image sensor equipped with multiple line sensors. According to this configuration, since a sensor including a plurality of line sensors is used, only one sensor needs to be aligned, and the adjustment work is simplified by reducing the number of sensors.

However, stacking a plurality of dichroic films via a transparent layer as described above means that a plurality of transparent films can be stacked at 100%
It is necessary to manage cranes of ~100 microns, which requires very difficult manufacturing technology, which raises the problem of high manufacturing costs. In this regard, in the method disclosed in JP-A No. 60-134556, since a total reflection mirror and a dichroic film are laminated via a relatively thick transparent layer, the manufacturing technique requires multiple thin dichroic films. Although it is simpler than the method disclosed in JP-A-62-234106, in which layers are laminated,
This device has a configuration in which the colors are separated into parallel light beams in front of the imaging lens system, so it is necessary to provide an imaging lens system for each separated color and form each image on the light receiving surface of the image sensor. ．． Providing a combination lens system and an image sensor for each separated color in this way leads to an increase in the size of the apparatus, and it also becomes necessary to perform alignment for each image forming lens system and image sensor, which increases the adjustment process such as positioning. The problem is that it becomes complicated.

<Problems to be Solved by the Invention> As mentioned above, in conventional image reading devices, the color separation elements require difficult manufacturing techniques, and the combination of dichroic ξ-color and total reflection ξ-color can be used easily. Even if an image reading device is equipped with a color separation element configured as follows,
There are problems in that an imaging lens system and an imaging sensor are required for each color separation.

The present invention has been made in view of the above problems, and uses a color separation element that can be manufactured relatively easily, does not increase the size of the image reading device, and does not require adjustment work such as positioning. The purpose is to provide an image reading device with as few parts as possible. <Means for Solving the Problem> Therefore, in the present invention, in an image reading device that separates and reads a color image, a color separation element in which a dichroic mirror and a total reflection mirror are laminated with a transparent layer interposed therebetween is used. It is arranged between an imaging sensor having a plurality of line sensors corresponding to each color and an imaging lens system.

Here, the color separation element is configured to include two types, and the two types of color separation elements are provided.
A color image is separated into three primary colors using different color separation elements, and the image sensor is configured to integrally include three line sensors corresponding to each of the three primary colors, so that images can be read for each of the three primary colors. You can also do it. Further, it is preferable that the thicknesses of the respective transparent layers constituting the two types of color separation elements be the same.

<Function> In an image reading device having such a structure, the color separation element is constructed by laminating a dichroic mirror and a total reflection mirror with a transparent layer interposed therebetween, and the dichroic mirror reflects only light in a predetermined wavelength range. While separating the colors, the total reflection mirror totally reflects the light that has passed through the dichroic ξ color.
One color separation element separates a color image into two colors.

The color separation element is an image sensor having a plurality of line sensors corresponding to each of the colors separated by the color separation element (including a structure in which a plurality of line sensors are included in a two-dimensional sensor). and an imaging lens system, and forms an image on the image sensor for each separated color.

Therefore, if two types of color separation elements are provided, for example, one color separation element can be arranged to separate blue and yellow, and the other color separation element can be arranged to separate yellow into red and green. So, red R. It is possible to separate colors into the three primary colors of green G and blue B, and if the image sensor is integrally equipped with three line sensors corresponding to each of the three primary colors in accordance with such color separation, it is possible to separate the colors into the three primary colors of green G and blue B. Image reading is possible.

Furthermore, when two types of color separation elements are provided to separate three colors as described above, if the thickness of the transparent layer constituting each of the two types of color separation elements is the same, the transparency of the color separation elements By standardizing the layer thickness, fabrication becomes easier, and the light after color separation can be made into parallel light with equal intervals. <Examples> Examples of the present invention will be described below. In FIG. 1 showing the first embodiment, an illumination lamp 1, which is a tube light whose longitudinal direction is orthogonal to the drawing, illuminates a color original 2 in a slit shape, and a color image from the color original 2 in the slit shape is illuminated. is reflected by a plurality of total reflection mirrors 3 to 5 and guided to an imaging lens 6 while changing direction, and a slit-shaped image of the color original 2 is formed on a CCD line sensor 7 by this imaging lens 6. It's like this. Here, a color separation element 8 is disposed between the imaging lens 6 and the CCD line sensor 7, and this color separation element 8 separates the incident image into parallel light beams of two colors. The separated light is imaged on each of two line sensors provided in parallel on the CCD line sensor 7.

The color separation element 8 has 5InIIIN. A total reflection mirror surface M is formed by aluminum vapor deposition on one end surface of the plate prism 9.
After that, a transparent polyimide or the like is coated on the total reflection mirror surface M to form a 157 μm transparent layer 10 (refractive index 1.
5), and then add 550 at a standard angle of incidence of 45°.
It has a dichroic ξ-D parallel to a total reflection ξ-D that reflects wavelengths shorter than nm and passes longer wavelengths. Therefore, a color image incident on the color separation element 8 is separated into the color reflected by the gyroic mirror D and the color reflected by the total reflection ξ color M after passing through the dichroic mirror D. In the CCD line sensor 7, two line sensors having color filters corresponding to the respective colors are provided in parallel at a predetermined interval in order to detect each of the light images separated into two colors by the color separation element 8. By arranging the line sensors so that they are positioned at the imaging positions of the respective light beams, it is possible to read the two-color images of the color original 2, respectively.

By the way, although the colors are separated by the color separation element 8 to obtain parallel light beams of two colors, as shown in FIG. 2, the light reflected by the dichroic mirror D and the light reflected by the total reflection mirror M are as follows. Because a difference in optical path length occurs, if the CCD line sensor 7 is arranged so as to be perpendicular to the parallel light beam and attempts to receive two colors of light on the same plane, both cannot be received at the focal position. To match both focal positions, it is necessary to arrange the CCD line sensor 7 at an angle with respect to the reference direction orthogonal to the parallel light beam. Here, the optical path length difference is defined as the distance between the two line sensors of the CCD line sensor 7 of S (168 μlm in this example).
), and if the incident angle to the color separation element 8 is θ1, the optical path length difference is given by Scos θ1, and the CCD line sensor 7
The angle α at which is tilted with respect to the parallel rays after color separation is α=9
It is given by 01-θ1.

In this way, the optical path length difference and the sensor inclination angle α are determined by the transparent layer 10.
The refractive index n1 of the air layer and the refractive index n. The thickness d of the transparent layer 10 to obtain parallel rays at a desired interval based on the line interval S is determined as 2 tan θ2. Note that θ2 is the refraction angle when the light enters the transparent layer 10 from the air layer, and if the incident angle θ1 is 45'', the CCD line sensor 7 is 45'' with respect to parallel light.
It would be better to place it at an angle.

Incidentally, in the above embodiment, the CCD line sensor 7 is actually
is equipped with a cover glass, whose thickness is 100
It is available as gwb. This is because in order to suppress chromatic aberration due to oblique incidence when the sensor is arranged at an angle as described above, it is desirable to make the thickness of the cover glass as thin as possible, and the thickness is preferably 1 mm or less, preferably 100 μm or less. It is.

According to the above embodiment, the color separation element 8 is constructed by forming the dichroic mirror D on the total reflection layer M with one transparent layer 10 interposed therebetween.
It is relatively easier to manufacture than when multiple layers of dichroic ink ξ rollers D are laminated. Furthermore, since the configuration is such that the two-color separated light is detected by each of the two line sensors provided integrally on one CCD line sensor 7, sensor position adjustment only needs to be performed for one CCD line sensor 7. , the process of adjusting the sensor position can be simplified. Furthermore, two-color images can be formed using one imaging lens 6, and there is no need to provide an imaging lens 6 for each separated color, so the number of components can be reduced and the device can be made larger. Furthermore, since there is only one imaging lens 6 and one CCD line sensor 7, position adjustment work is also simplified. Note that scanning of the color original 2 may be performed by moving the color original 2 or by moving the optical system of the image reading device. Next, in FIG. 3 showing the second embodiment, the structure shown in FIG. 1 differs only in the shape of the color separation element 8, and the other basic structures are the same. Therefore, the same elements as in FIG. 1 are given the same reference numerals and their explanations will be omitted.

The color separation element 8 in the second embodiment shown in FIG. 3 has a plate thickness of 97 mm.
A total reflection mirror M is formed on one end surface of the glass plate 11 with a diameter of μm by aluminum evaporation, while a guichroic mirror M is formed on the end surface corresponding to the long side of the cross section of the columnar prism 12 having a cross section of a right-angled isosceles triangle. The surface opposite the total reflection mirror M of the glass plate l1 is adhered to the dichroic mirror D with U■ (ultraviolet) curing resin to form a 99μ
A transparent layer (refractive index 1.5) of m (adhesive layer of 2μ steel) is formed.

In the color separation element 8, the light image incident on the prism l2 is separated into two colors, one reflected by the dichroic ink mirror D and the other transmitted, and then received by the sensor 7 via the prism l2 again. It will be done.

Here, if the interval S between the two line sensors provided in the CCD line sensor 7 is 168 μm, and considering the optical path length difference as described above, the sensor 7 will be .7@ By arranging the sensor at an angle, it is possible to arrange the line sensor at the focal position of each of the two colors. The reason for setting such an inclination angle will be described below with reference to Figure 4. That is, if the refractive index of the air layer is n1, the refractive index of the prism is n', the angle of incidence with respect to the dichroic mirror D is θ, and the oblique mounting angle around f of the sensor 7 is α, then
The optical path length difference is: Optical path length difference - S sincr - 2 d cos θx n 1
/ n 2, and if the incident angle θ to the dichroic mirror D is 45'', then tan α = n 1 / fl
z, optical path length difference = S3inff = 2 "" d
Xn+/n! Therefore, n,=l,ng=
1.5, α becomes approximately 33.7@, and based on the line spacing S (-168μ), the thickness d of the transparent layer is approximately 99μ since the optimum value is obtained in countries such as The thickness of the transparent layer is set to 99μ. The cross section of the prism 12 is a right-angled isosceles triangle to prevent the incident light from being refracted by entering the prism 12 at a right angle when the angle of incidence on the guichroic mirror 10 is set to 45 degrees. This is to make it. Next, in FIG. 5 showing the third embodiment, a color image is separated into three primary colors by a color separation element 8, and correspondingly, the CCD line sensor 7 has three color filters each having a color filter. Line sensors are provided at equal intervals.

The color separation element 8 is a right-angled isosceles triangular columnar prism l3.
A dichroic mirror D is formed on each of the end faces sandwiching the right-angled ridgeline of the dichroic mirror D, and two right-angled isosceles triangular columnar prisms 14 having a base substantially equal to the end face of the dichroic mirror D are provided. A total reflection mirror M is formed on each bottom surface of the prism 14, and the total reflection mirror M faces the surface of each dichroic mirror D in parallel with a predetermined interval (predetermined transparent layer thickness). The prisms 13. 14 Glue each other. As a result, the dichroic ξ mirror D and the total reflection mirror M are laminated with a transparent layer of a predetermined thickness interposed therebetween.
The angle of incidence on the prism is set to 90". Also, by setting the angle of incidence on the dichroic mirror D to 45", the angle of incidence on the prism becomes 90".
°, thereby avoiding refraction upon incidence on the prism.

Here, a transparent bead with a diameter of 119μ is used as a spacer, and the gap is regulated by intervening this bead between a plurality of dichroic mirrors D and a total reflection mirror M, avoiding the optical path. By filling it with resin, it adheres and forms a transparent layer. In this embodiment, two dichroic ξ mirrors D are provided, but if the dichroic mirror D that enters first has characteristics of red reflection and cyan transmission, and the other has characteristics of blue reflection and yellow transmission, then The image separated into red and cyan by the passing dichroic mirror D is divided into red, green, and blue because blue is reflected from cyan by the next dichroic mirror D, and the remaining green is reflected by the total reflection mirror M. The color is separated into three primary colors. In this embodiment, a CCD line sensor 7 having three line sensors each having a color filter corresponding to the three primary colors at equal intervals is attached to the prism 13 and integrated. The cover glass of the sensor 7 can be omitted.

In the color separation element 8 having such a configuration, the light path is the longest for the middle light vA (green) among the light rays separated into three colors.
Since the light rays on both sides have the same optical path length, it is not possible to arrange the CCD line sensor 7 to match the focal position of each of the three colors. Therefore, it is necessary to position the CCD line sensor 7 so that the sensor element is placed near the middle of two successive focal positions, and the distance to each focal position is within the depth of focus. It is necessary to set the optical path length difference so that the sensor 7 can be placed within the depth of focus. In the structure of this embodiment, the transparent layer has an area of 119 μm and the incident angle is 45°, so that the focal position shifts by about 112 μm back and forth. However, by placing the sensor 7 at the midpoint, the focal point Since the sensor element can be placed within ±56 μ from the position, the sensor can be placed within the depth of focus.

Next, in FIG. 6 showing the fourth embodiment, whereas in the third embodiment, two dichroic mirrors 10 are arranged at right angles to separate a color image into three primary colors, two dichroic mirrors The mirrors D are disposed parallel to each other, and the two parallel dichroic mirrors D separate a color image into three primary colors.The color separation element 8 of this embodiment has a narrow angle of 45 mm. A dichroic mirror D is formed on each of the opposite end surfaces of a parallelogram prism l5 set at
Two prisms with a total reflection mirror M formed on one end surface are prepared, and both prisms 15. 16, the short dichroic mirrors D face each other in parallel at a predetermined interval, and a total reflection mirror M is provided on the outside of each dichroic mirror D with a transparent layer interposed therebetween. As the substrate, beads as described above may be used, but a tungsten wire or the like having a predetermined diameter may also be used. In order to make the width 99μm, the diameter is 99μm.
A tungsten wire is used as a spacer to avoid the optical path, and the gap is filled with UV curing resin to form a transparent layer between the dichroic mirror D and the total reflection mirror M.

The dichroic mirror D reflects cyan and passes red on the side where the color image from the imaging lens 6 is incident, and the second dichroic mirror D on the side where the color image separated into cyan and red is incident. In Guicroic Mira 10,
It is designed to reflect blue and pass yellow, and the red and cyan are separated into blue and green by the next dichroic mirror D, resulting in a color image consisting of red, green, . It is separated into the three primary colors of blue and read by three line sensors each having a color filter on the CCD line sensor 7. In this embodiment, as in the second embodiment, by installing the CCD line sensor 7 at an angle of 33.7 degrees with respect to the direction perpendicular to the resolved light, light reception corresponding to the optical path length difference is achieved. If the line sensor spacing is 168 .mu.m, each of the three primary colors can be received by the line sensor at the 99 .mu.m distance between the light separated by the transparent layer. In the above embodiment, in which two sets of dichroic mirrors D are used to separate a color image into three primary colors, the thickness of each transparent layer is the same in both cases. This corresponds to the line sensors that emit light at regular intervals and is provided at equal intervals, and is set to be the same for the sake of manufacturing simplicity by keeping the dimensions constant. However, if the difficulty in manufacturing is not taken into consideration, as shown in FIGS. 7 to 9, the interval between the decomposed lights can be made constant even if the thickness d of the transparent layer is not the same.

Figure 7 shows the same thickness d of the transparent layer.
A color image is separated into three primary colors by arranging color separation elements in parallel. First, in the first guichroic
(see figure 1), and only the other wavelengths of colors A and B are allowed to pass through.
The next dichroic ink also has a configuration that reflects color A of the short wavelength side from the light reflected by the first dichroic ξ color D, thereby separating color B of the intermediate wavelength. The three primary colors A, B, and C are each emitted as equally spaced parallel rays. On the other hand, in the color separation elements shown in FIGS. 8 and 9, the three primary colors A, B, and C are separated by a dichroic ξ mirror D having the same configuration, but in FIG. 8, the second dichroic mirror The thickness d of the transparent layer laminated between D and the total reflection mirror M is twice the thickness d of the transparent layer constituting the first dichroic mirror D, but even in such a configuration, the three primary colors A , B, and C are emitted at equal intervals.

However, in the color separation element shown in FIG. 8, the first dichroic mirror D is configured to reflect only C color.
The second dichroic mirror D separates the light that has passed through the first dichroic ξ mirror D and been totally reflected into A color and B color.

In Figure 9, the relationship between the thicknesses d of the transparent layer in Figure 8 is reversed, and the thickness of the first incident side is doubled, but in this case as well, the three primary colors separated are Emitted at equal intervals. Here, similar to the color separation element shown in FIG.
Only C color is reflected by the first guichroic ξ ra D,
The configuration is such that the second Gikroic Clark D separates A and B colors. In this way, even if the thickness d of the transparent layer is not necessarily the same, it is possible to make the emitted separated light beams at equal intervals. It can also be applied to the horizontal case where the direction of is reversed (see FIG. 5).

In addition, when separating into three primary colors using two sets of color separation elements each consisting of a dichroic filter D and a total reflection mirror M laminated via a transparent layer as in the above embodiment, FIGS.
As shown in Figure 17, multiple color separation stages can be set. In the case shown in Fig. 12, the first guichroic ξ ray D reflects cyan b and passes red R (in the figure, the part before the "/" symbol indicates reflected light, and the part after it indicates transmitted light.) , In the next Gikkuritsukan color D, it is sufficient to separate blue B or green G from the reflected cyan C, and by using one that reflects blue B and passes yellow Y, or one that passes green G and passes magenta M. , blue B and green G can be separated from cyan C, and together with red R separated by the first dichroic mirror D, separated lights of three primary colors are obtained.

In the case shown in FIG. 13, magenta M is first reflected by dichroic mirror D and green G is separated, so next, it is sufficient to separate red R or blue B from magenta M. R reflection cyan C pass or blue B reflection yellow Y
By using the passing dichroic ξ color D, magenta M can be separated into blue B and red R.

In the case shown in FIG. 14, yellow Y is first reflected by dichroic mirror D to separate blue 8, and the next dichroic mirror D is set to pass red R reflecting cyan C or green G reflecting magenta. This separates red R and green G from yellow Y.

In the case shown in Fig. 15, red R is first reflected by the dichroic mirror D, cyan C is separated, and then the next dichroic mirror D is passed through the yellow Y reflection blue B or the magenta M reflection green G. By doing so, blue B and green G are separated from cyan C.

In the case shown in FIG. 16, green R is first reflected by dichroic mirror D, magenta M is separated, and then cyan C is reflected by red R passing through dichroic mirror D, or
By reflecting yellow Y and passing blue B, blue B and red R are separated from magenta M. In the case shown in FIG. 17, blue B is first reflected by the dichroic ξ color D and yellow Y is separated, and then the dichroic ξ color D is passed through the cyan C reflected red R or the magenta M reflected green G. By passing through, green G and red R are separated from yellow Y.

In this way, various combinations of characteristics of the dichroic mirror D can be set, but in the dichroic ink mirror D in which the wavelength of the green G is set as a reflection/non-reflection wavelength, the green G
is an intermediate wavelength sandwiched between red R and blue B, and has two large and small threshold wavelengths, so the resolution performance is inferior to that of one threshold, so green G reflected magenta M It is preferable to avoid using a dichroic mirror D that has characteristics such as passing, magenta, M, reflecting green, and G. In addition, in FIGS. 12 to 17, which show multiple types of color separation characteristics, two sets of color separation elements are arranged in parallel. I mentioned what was set up,
It goes without saying that a plurality of types of settings can be made in the same way in other arrangement relationships, such as when they are arranged at right angles.

In the above embodiment, two-color separation and three-color separation were described, but four-color separation is also possible by using three sets of color separation elements each consisting of a dichroic mirror D and a total reflection mirror M laminated with a transparent layer interposed therebetween. It is possible.

In the color separation element shown in FIG. 18, three sets of laminated dichroic mirrors D and total reflection mirrors M are arranged in a U-shape. Then, only the b wavelength range shown in the five color separation characteristic diagrams shown in FIGS. 19 and 20 is reflected by the first dichroic mirror D, and the b
The C color is separated by reflecting only those belonging to the C wavelength range from wavelengths outside the wavelength range. Next, in the third dichroic mirror D, from the light in the b wavelength range reflected by the first dichroic mirror D and totally reflected by the second dichroic mirror D to the light in the a wavelength range (
By reflecting only color A), it is separated into color A and color B. In addition, the light with wavelengths other than the C wavelength range separated by the second guichroic mirror 10 is directly reflected by the total reflection mirror M and output in the form of DfE color.
．． It is separated into four colors: B, C, and D+E. Note that when the above three types of color separation elements are arranged in a U-shape and are separated into four colors, a shift in the focal position occurs due to the difference in optical path length, as shown in FIG. Since the deviation is not linear but moves back and forth, a line sensor is arranged so as to be located approximately in the middle of these focal positions so that each of the four colors can be detected within the depth of focus.

In addition, four types of color separation elements are prepared by laminating dichroic ξ mirrors D and total reflection mirrors M through transparent layers, and as shown in FIG. 21, two types of color separation elements are arranged on the same plane. A dichroic mirror is placed on each other.
It is also possible to separate five colors by arranging them parallel to each other with the D sides facing each other. The process of color separation in the device shown in FIG. 21 will be explained with reference to FIGS. 19 and 20. First, in the color separation element on which the color image first enters (angle of incidence 45°),
The dichroic mirror D reflects the colors in the wavelength range d, excluding the long wavelength E color, and allows only the E color to pass.

The next dichroic mirror D reflects the wavelength range C excluding the wavelength range of color D from the wavelength range d, and passes the rest, so the first dichroic also reflects the wavelength range d (A In the second guichroic ξ color D, the wavelength range c (color A, color B) is
Only the color C) is reflected, and only the color D passes through and is totally reflected.

The third dichroic ξ ray D reflects the wavelength range b consisting of A color and B color and passes the others, so the wavelength range c (A color. Only C color among the B color and C color) is allowed to pass through.

The fourth dichroic mirror D reflects only the A color wavelength and passes the other wavelengths, so 3
Only the A color is reflected from the wavelength range b reflected by the th dichroic mirror D, and the remaining B color is passed.

In this way, E color. D color, C color. The B color and the A color are separated in this order, and as a result, five colors can be separated. In addition, when the color separation elements are arranged in parallel and are made to enter alternately at parallel intervals, as shown in Fig. 21, the shift in the focal position due to the difference in optical path length causes a linear tilt as shown in the figure. By tilting the sensor accordingly, each color can be detected at its focal position. Also, the 21st
In the parallel arrangement of color separation elements as shown in the figure, since the color separation elements can be arranged in succession to reflect light, separation of five or more colors is also possible. Furthermore, in the configuration shown in FIG. 21, a color separation element may be provided which is disposed at right angles to the color separation element that emits the last five color separated lights, and the dichroic mirror D and the total reflection ξ mirror may be provided. The format of arranging a plurality of color separation elements formed by stacking M and M with a transparent layer interposed therebetween is not limited to that shown in this embodiment.

Next, the method for manufacturing a color separation element in which the dichroic mirror D and the total reflection ξ mirror M according to the present invention are laminated via a transparent layer is described in the first to fourth embodiments above. , are summarized and described below.

First, in order to create a reflective surface in which the dichroic mirror D and the total reflection mirror M are laminated via a transparent layer, the dichroic mirror D, the transparent layer, and the total reflection mirror M are placed on a transparent substrate or prism. They may be laminated in this order or in the reverse order. The transparent layer may be an air layer, resin, glass, inorganic material formed by CVD or vapor deposition, SiCh. SiN. The transparent layer is produced by coating. CVD, vapor deposition. This is done using methods such as sputtering, sandwiching transparent plates, and sandwiching spacers.

Alternatively, a dichroic ξ mirror D and a total reflection mirror M may be formed on the front and back surfaces of a transparent plate such as glass, respectively, or the transparent plate may be attached to a prism or the like to improve flatness. It's okay.

In addition, dichroic mirror D is placed on a transparent substrate or prism.
It is also possible to form a total reflection layer M on one end surface of a transparent plate such as a glass plate and attach it thereon.

Furthermore, a dichroic mirror D is formed on one of two transparent substrates or prisms, and a total reflection mirror M is formed on the other, and the two transparent substrates are arranged so that the dichroic mirror D and the total reflection mirror M face each other. Alternatively, the prism may be bonded with a spacer interposed therebetween.

Examples of the spacer include beads, fibers, thin wires, and transparent plates such as glass plates. Here, the transparent layer portion may be formed into an air gap, or may be filled with resin such as UV resin.

Incidentally, the angle of incidence on the dichroic mirror 10 may be any number, but from the viewpoint of ease of setting, it is preferably 30°, 45°, or 60°, and most preferably 45°. Further, the CCD line sensor 7 that integrally includes a plurality of line sensors is preferably a single chip or a single package. When three or more line sensors are integrally provided, the intervals between the line sensors should be equal. Preferably, but
They do not necessarily have to be equally spaced.

Effects of the Invention> As explained above, according to the present invention, a color separation element is formed by laminating a dichroic mirror and a total reflection mirror through a transparent layer. It is easier to manufacture than the case of stacking dichroic mirrors, and the color separation element is arranged between an imaging sensor and an imaging lens system that are integrally equipped with a plurality of line sensors corresponding to each separated color. As a result, there is no need to provide an imaging lens system or an image sensor for each separated color, and the apparatus structure can be simplified and adjustment work etc. can be simplified.

Furthermore, if two types of color separation elements are provided, it becomes possible to separate a color image into three primary colors and read the image for each of the three primary colors using three line sensors. It is easy to cope with an increase in the number of required decompositions.

Furthermore, if the thicknesses of the transparent layers constituting the color separation element are the same, manufacturing becomes easy and the separated colors can be easily emitted as equally spaced parallel light beams.

[Brief explanation of drawings]

FIG. 1 is a front view showing the first embodiment of the present invention, FIG. 2 is a diagram for explaining the calculation of the optical path length difference in the color separation element shown in FIG. 3, and FIG. 3 is a front view showing the first embodiment of the present invention. Front view showing an example,
4 is a diagram for explaining the calculation of the optical path length difference in the color separation element shown in FIG. 3, FIG. 5 is a front view showing the third embodiment of the present invention, and FIG. 6 is a diagram showing the fourth embodiment of the present invention. Front view showing an example,
7 to 9 are diagrams for explaining the relationship between the transparent layer thickness and the emitted light interval, respectively, and FIGS. 10 and 11 are diagrams for explaining the separation wavelength characteristics in three-color separation, respectively. 12 to 17 are diagrams each showing a three-color separation pattern, and FIG. 18 is a diagram showing a four-color separation color separation element.
FIGS. 19 and 20 are diagrams for explaining the separation wavelength characteristics in five-color separation, respectively, and FIG. 21 is a diagram showing the configuration of a color separation element for five-color separation.

Claims (3)

[Claims] (1) In an image reading device that separates and reads a color image, a color separation element in which a dichroic mirror and a total reflection mirror are laminated with a transparent layer interposed therebetween is used as an image sensor having a plurality of line sensors corresponding to each separated color. An image reading device characterized by being disposed between a sensor and an imaging lens system. (2) It is configured with two types of color separation elements, and the two types of color separation elements separate a color image into three primary colors, while the image sensor integrates three line sensors corresponding to each of the three primary colors. 2. The image reading device according to claim 1, further comprising: (3) The image reading device according to claim 2, wherein the transparent layers constituting the two types of color separation elements have the same thickness.