JPH1079833A - Color image scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure of an optical system and to reduce the cost by adopting a configuration that a light reflected at both end faces of a dichroic mirror is delivered to a color sensor. SOLUTION: A dichroic mirror 26 is formed by adhering three dichroic mirrors 26a-26c reflecting respectively R, G, B light into one mirror. Reflected light from an original reaches the one side face of the dichroic mirror 26 via an image-forming lens 24 and reflected thereon and is spectrally seperated into R, G, B light, they reach the other side face of the dichroic mirror 26 via two total reflecting mirrors 25 and reflected thereon again and reach a CCD line sensor 28. Thus, the separating width of the R, G, B light is larger than that the case with reflection only at one side face, and then the R, G, B separation is ensured. Furthermore, the optical path length of the R, G, B light differs from each other when the light is reflected in one side face only and then dispersed, but the optical path length difference is almost eliminated when they are reflected again on the other side face and spectrally separated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color image scanner, and more particularly to a color image scanner using a CCD line sensor in an image input device such as a copying machine or a personal computer.

[0002]

2. Description of the Related Art Generally, in a color image scanner using a CCD line sensor in an image input device such as a copying machine, a facsimile, a personal computer, etc., incident light from an imaging lens is red (hereinafter referred to as red). It is necessary to decompose the color into three colors, that is, R (green) (hereinafter, G) and blue (B).

As a method of decomposing incident light from an imaging lens into R, G, and B, a "color sensor system" and a "dichroic prism or dichroic mirror system" are known.

The color sensor system is shown in FIGS. 5 and 6. As shown in FIG. 6, three image sensors are provided on the same chip, and R, G, and B filters are arranged in each image sensor. R sensor 31a and G sensor 31b
And a color sensor (C
A CD line sensor 33 is formed, and color separation and photoelectric conversion of incident light from the imaging lens 34 are simultaneously performed.

That is, as shown in FIG. 5, reflected light from an original placed on an original platen glass 32 illuminated by a white light source as a lamp 35 is reflected by a mirror 37 and an imaging lens 34.
When the image is formed on the color sensor 33 via the color sensor 33, a signal of a color component corresponding to each of the sensors 31a, 31b, and 31c is output from the color sensor 33.

The color sensor system has a simple configuration, can use an optical system common to monochrome, and can easily increase the speed. Since the R, G, and B pixel position accuracy is determined by the accuracy of the color sensor, the color misregistration is fixed and correction can be performed, so that high accuracy can be achieved. However, as shown in FIG. 6, since the reading positions of R, G, and B are divided into different lines, a line memory for correction is required, and the optical system becomes complicated and the whole becomes expensive. Had.

On the other hand, in the dichroic prism system, as shown in FIG. 7, the same optical axis is divided into R, G, and B light by a dichroic prism, and each light is photoelectrically converted by an image sensor (line sensor). It has become. That is, the reflected light from the original placed on the original platen glass 32 illuminated by the white light source, which is the lamp 35, enters the dichroic prism 38 via the mirror 37 and the imaging lens, and is reflected by the first prism 38a. Blue light is reflected to blue light, red light is reflected to the second prism 38b to red light, and finally blue light and red light are removed from incident light by the third prism 38c to become green light. Image sensors 39a and 39b corresponding to
At 39c, photoelectric conversion is performed to perform color separation.

In this system, three sets of image sensors 39
Since the photoelectric conversion is performed at a, 39b, and 39c, the number of readings is only one for each line, and high-speed reading is possible.
The reflected light of the same object is reflected by three sets of image sensors 39.
a, 39b, and 39c are read, so that a line memory for correction for alignment is not required. However, since the dichroic prism 38 is used, the spectral characteristics are related to each other, and an arbitrary spectral characteristic can be obtained. Can not. Further, the respective image sensors 39a, 39b, 39c
As for the position adjustment, precise position adjustment is required, and the optical system is complicated.

In the dichroic mirror system, as shown in FIG. 8, reflected light from an original placed on an original platen glass 32 illuminated by a white light source as a lamp 35 is reflected by a mirror 37, The light is reflected by the two dichroic mirrors 41 and 42 via the imaging lens 34, and is separated into R, G, and B light at the time of reflection, and enters the CCD line sensor 33 as a color sensor to form an image. The line sensor 33 outputs an output corresponding to the color component corresponding to the incident light.

In the dichroic mirror system, similarly to the color sensor system, the configuration is simple, an optical system common to monochrome can be used, and high-speed operation is easy. However, the use of two or more dichroic mirrors has a problem that the whole becomes expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image scanner of a dichroic mirror type which can have a simple optical system and can be made inexpensive as a whole.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a method of reflecting reflected light of an original by a dichroic mirror via an image forming lens and splitting the reflected light into R, G, and B light.
A color image scanner of a dichroic mirror system configured to output a signal corresponding to each color by a color sensor, wherein the dichroic mirror is R,
A dichroic mirror that reflects each of G and B is laminated and formed. Total reflection mirrors are arranged on both sides of the dichroic mirror. Light reflected on one side of the dichroic mirror is guided to the other side by the total reflection mirror. And the light is reflected again and transmitted to the color sensor.

[0013]

Since the present invention is constructed as described above, the reflected light of the original reaches one side surface of the dichroic mirror via the imaging lens and is reflected there.
The light reaches the other side of the dichroic mirror via two total reflection mirrors, is reflected again, and is transmitted to the color sensor. Therefore, the separation width of R, G, and B is larger than that when the light is reflected only on one side, and the separation of R, G, and B is ensured. Further, the optical path lengths of R, G, and B are different when reflected and spectrally reflected on only one side, but the optical path length difference is almost eliminated by being reflected again and spectrally separated on the other side.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image scanner according to the present invention shown in the drawings will be described below. 1 to 4 show an embodiment of a color image scanner according to the present invention. FIG. 1 is an overall schematic view of a general color image scanner, and FIG. 2 is a state where a part of FIG. 1 is removed. FIG. 3 is a schematic diagram showing the relationship among an imaging lens, a total reflection mirror, a dichroic mirror, and a CCD line sensor provided inside a lens barrel. FIG. 4 is a diagram showing light incident on the imaging lens. FIG. 3 is a diagram for explaining a dichroic mirror and a reflection process up to a CCD line sensor via the mirror.

FIGS. 1 and 2 show the structure of a general color image scanner using a CCD line sensor in an image input device such as a copying machine, a facsimile, a personal computer or the like.

In this general color image scanner, a pair of rails 2, 2 for supporting a mirror in an operation direction are provided on opposing inner surfaces of a frame body 1, which is open up and down,
A machine base 6 having the first mirror unit 5 located on the upper surface and a machine 8 having the second mirror unit 7 located on the upper surface are provided so as to extend between the rails 2 and 2, respectively.

The first mirror unit 5 and the machine base 6 form a first mirror moving body 3, and the second mirror unit 7 and the machine body 8 form a second mirror moving body 4, respectively. Also, 2
Reference numeral 3 denotes a lens barrel provided with a CCD line sensor.

Further, shafts 10 and 11 which are orthogonal to the rails 2 and 2 are provided on the frame 1 at both ends of the rails 2 and 2, respectively. And a flywheel 12 is attached. A drive transmission pulley 13 is provided at a portion of the shaft 10 inside the frame 1, and is provided between the shaft 10 and a drive shaft of a stepping motor 14 which is a drive source mounted outside the frame 1. Is provided with a timing belt 15.

The shafts 10 and 11 are provided with pulleys 16a, 16b, 17a and 17b for the first mirror moving body 3 and the second mirror moving body 4, respectively. Fixed wire 18,
Reference numeral 18 denotes pulleys 16a, 1a for the first mirror movable body 3 and the second mirror movable body 4 provided on both shafts 10, 11.
The other end is fixed to the frame 1 after the bases 6b, 17a, 17b, the base 6 of the first mirror moving body 3 and the base 8 of the second mirror moving body 4 are hung.

As described above, the first mirror moving body 3 and the second mirror moving body 4 move along the rails 2 and 2 in a predetermined relationship when the stepping motor 14 is driven by winding the wires 18 and 18 around. It has become.

Light emitted by a lamp (not shown) is reflected by an original placed on the upper surface of an original platen glass provided horizontally on the upper surface of the frame 1, and this reflected light is reflected by the first light.
A mirror 20 located inside the mirror moving body 3 through the opening 5a of the first mirror section 5; and a second mirror moving body 4
The light is reflected by mirrors 21 and 22 provided inside the lens and transmitted to the lens barrel 23.

FIG. 3 shows an imaging lens 24 and two total reflection mirrors 25, 2 provided inside a lens barrel 23.
5, the positional relationship between the dichroic mirror 26 and the CCD line sensor 28 is shown.

That is, the reflected light from the original is reflected by the mirror of the second mirror moving body 4 and enters the lens barrel 23. This light first enters the imaging lens 24, is reflected by one side of the dichroic mirror 26, is reflected by the two total reflection mirrors 25, 25, and reaches the other side of the dichroic mirror 26, where the dichroic mirror 26 Is reflected by the other side surface and enters a CCD line sensor 28 provided on the bottom surface of the lens barrel 23, where R, G, B
A signal corresponding to each color is output.

FIG. 4 shows the details of the RGB spectral optical system at the time of this reflection. The dichroic mirror 26 used in the present invention is formed as a single mirror by bonding three dichroic mirrors 26a, 26b and 26c reflecting R, G and B, respectively.

The dichroic mirror 26 includes the imaging lens 2
The light from the imaging lens 24 is reflected at 45 ° by inclining at 67.5 ° with respect to the optical axis 4.

On the other hand, two total reflection mirrors 2 used to reflect light reflected on one side surface of the dichroic mirror 26 on the other side surface of the dichroic mirror 26
Reference numerals 5 and 25 are located on both sides of the dichroic mirror 26 at an angle of 22.5 ° from each other. Therefore, the light reflected on the other side of the dichroic mirror 26 is 45 °
Is transmitted to the CCD line sensor 28 in the inclined state.

In the above configuration, when only one side surface of the dichroic mirror 26 is used, R, G,
Since the reflection position of B is different in the thickness direction, R, G, B
However, the use of both side surfaces of the dichroic mirror makes it possible to reduce the optical path length difference between R, G, and B, that is, to almost zero.

When the thickness of the dichroic mirror 26 is 0.3 mm in the configuration as shown in FIG.
When the optical path length difference on the surface of the D line sensor 28 with reference to G, R is -0.0000417 mm and B is 0.00
00417 mm, which was almost 0. Also, CCD
The separation width of R, G, and B on the surface of the line sensor 28 was 0.3 mm between R and G and between G and B, respectively.

[0029]

According to the present invention, as described above, the optical system can have a very simple configuration because it is sufficient to guide the light reflected on one side of the dichroic mirror to the other side. In addition, by reflecting the light on both sides of the dichroic mirror, the difference in the optical path lengths of R, G, and B can be almost eliminated, and the separation width can be increased, so that the light can be separated into R, G, and B reliably. it can. In addition, since the dichroic mirror system is used, a line memory for positioning is not required, and there is an effect that the whole can be made inexpensive.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of a general color image scanner.

FIG. 2 is a schematic diagram showing a state where a part of FIG. 1 is removed.

FIG. 3 is a schematic diagram showing the relationship among an imaging lens, a total reflection mirror, a dichroic mirror, and a CCD line sensor provided inside a lens barrel.

FIG. 4 is a diagram for explaining a process of reflection of light incident on an imaging lens until reaching a CCD line sensor via a dichroic mirror and a mirror.

FIG. 5 is a schematic diagram showing a color sensor system for separating into R, G, and B.

FIG. 6 is a schematic diagram showing a CCD line sensor used in FIG.

FIG. 7 is a schematic diagram showing a dichroic prism system for decomposing into R, G, and B.

FIG. 8 is a schematic diagram showing a dichroic mirror system for decomposing into R, G, and B.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Frame 2 ... Rail 3 ... 1st mirror moving body 4 ... 2nd mirror moving body 5 ... 1st mirror part 5a ... Opening 6, 8 ... Machine stand 7 ... 2nd mirror Part 10, 11 Shaft 12 Flywheel 13, 16a, 16b, 17a, 17b Pulley 14 Stepping motor 15 Timing belt 18 Wire 20, 21, 22, 25, 37 Mirror 23 lens barrel parts 24, 34 imaging lenses 26, 26a, 26b, 26c, 41, 42 dichroic mirrors 28, 33, 39a, 39b, 39c color sensor (CCD line sensor) 31a … R sensor 31b… G sensor 31c… B sensor 32… Original platen glass 35… Lamp 38… Dichroic prisms 38a, 38b, 38c… prism

Claims (1)

[Claims] 1. A color of a dichroic mirror system in which reflected light of a document is reflected by a dichroic mirror via an image forming lens to be separated into R, G, and B, and a signal corresponding to each color is output by a color sensor. An image scanner, wherein the dichroic mirror is R, G, B
A dichroic mirror that reflects each is laminated and formed, and total reflection mirrors are arranged on both sides of this dichroic mirror, and light reflected on one side of the dichroic mirror is guided to the other side by the total reflection mirror and reflected again And transmitting the color image to the color sensor.