JP3398163B2 - Image reading device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image reading device for reading a color image for inputting a color image to an image processing device connected to a computer or the like, and particularly to prevent color misregistration in the color image reading device. Regarding improvement of optical system.

[0002]

2. Description of the Related Art Generally, in order to input a color image to an image processing apparatus connected to a computer or the like, a color image reading apparatus for reading a color image is used. In such a color image reading apparatus, an original is placed on a transparent original placing table made of glass or plastic, and image information of the original surface is imaged on a reading device such as a CCD sensor by an imaging lens system. It The image information formed on the CCD sensor is converted into an electric signal by the CCD sensor, stored in a predetermined memory as an image information signal, or output to an image forming apparatus or the like connected to the outside.

In the above-mentioned color image reading apparatus, a 1-line CCD method and a 3-line CCD method have already been proposed as a method for reading a color image. In a color image reading device adopting the 1-line CCD method, an original is read by one CCD line sensor. That is, the same area on the original is scanned three times, and the color separation filter mounted on the imaging lens system is changed for each scan to decompose the image information of the area into three color components, and each scan is performed. Image signals corresponding to the three color components are generated as image information from the CCD line sensor. Image signals obtained by these three scans are combined to reproduce a one-line color image. On the other hand, in a color image reading apparatus adopting the 3-line CCD method, the image on the original is read by the three CCD line sensors. That is, areas on different originals corresponding to the arrangement pitch of the CCD line sensors are simultaneously scanned, and image signals from the individual line sensors are generated as different color component image information of different areas. Image signals obtained one by one by this scanning are combined to reproduce a color image on the original.

The 1-line CCD method has a low reading speed because it requires three scans for one document, and is mainly used in a reading device for reading an image at a low speed. Also,
A memory is required for each color component, and image information obtained by scanning three times needs to be combined. At the time of alignment when synthesizing the image information, high precision is required for the driving device of the image reading device and the structure of the device, and its control is also very complicated.

The 3-line CCD method has a high reading speed because the image information can be read by one scanning with respect to one original, and is used in a reading device for reading an image at a relatively high speed. However, in the 3-line CCD sensor used in this method, three 1-line CCD sensors are
Since they are formed in one unit, the document reading position is different. Therefore, image signals of each color component in the same area are output at different timings according to the arrangement pitch of the three line CCD sensors. As a result, displacement of each color in the read image information component is generated. Various methods have been proposed as methods for removing the deviation for each color component in the above-described 3-line CCD sensor method.

Japanese Unexamined Patent Publication No. 1-97056 discloses 3-line C
An example is disclosed in which an image of an area corresponding to the array pitch of the CD sensor is read, image information is stored in a memory for each color component, and a positional deviation between the color components of this image information is electrically corrected. ing. According to this method, the deviation between the color components of the image information due to the arrangement pitch of the CCD sensors is removed. However, similar to the 1-line CCD method described above, there is a problem that complicated image information synthesis is required.

Further, in Japanese Patent Laid-Open No. 2-115816, image information is read by shifting the reading position according to the arrangement pitch of each line CCD sensor, and the image information due to the arrangement pitch of each line CCD sensor is read. A method for optically removing the deviation of each color component is disclosed.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the color image reading device disclosed in No. 7056,
With respect to the arrangement pitch of the individual line CCD sensors of the three-line CCD sensor, that is, the deviation of the image information of each color component due to the interval between the line CCD sensors caused by the CCD charge transfer paths arranged on both sides of each line CCD sensor. The image reading information is read by slightly shifting the reading position itself with respect to the interval of each line CCD sensor. The image information read after being slightly shifted is combined using a memory, and the deviation of the image information of each color component is removed.

However, the above-mentioned JP-A-1-97056.
In the color image reading device disclosed in Japanese Laid-Open Patent Publication No. 2000-242242, when the image to be read is a color image, since the image information also includes gradation data, an interline correction memory having a huge storage capacity is required. There's a problem. When a zoom function is added to the image reading device, a very complicated process such as changing the number of lines in the line memory or performing calculation between lines is required depending on the magnification, which increases the circuit scale. There is a problem that the cost is unavoidable. In addition, since the reading position itself is slightly shifted, there is a problem that the reading position of each color component shifts due to mechanical vibration in the sub-scanning direction, resulting in color shift and color fringing in the output image. Naturally, if the speed of the read object is not stable,
Alternatively, if the speed is unknown from the beginning, the amount of correction in the line-to-line correction memory cannot be determined, so that image reading without color misregistration becomes impossible. Further, in the alignment when synthesizing the image information, there is a problem that the driving device of the image reading device and the structure of the device require high accuracy and the control thereof becomes very complicated.

Further, in the color separation device disclosed in the above-mentioned Japanese Patent Laid-Open No. 2-115816, the arrangement pitch of a plurality of line CCD sensors in which light beams corresponding to image information are arranged in parallel on the same plane. The color separation means is used to perform color separation at intervals corresponding to, and to set the color-separated light beam to be transmitted in the same direction, thereby optically removing the deviation of the image information of each color component.

However, the above-mentioned JP-A-2-11581
The color separation means disclosed in No. 6 has a light-transmissive member as a substrate, a light beam reflecting surface for reflecting a light beam is provided on one surface, and the other surface parallel to the light beam reflecting surface is provided. Is composed of a dichroic prism provided with a color selection surface for selectively transmitting and reflecting the color components contained in the light beam. Therefore, when the array pitch of each line CCD sensor is small, such as when using a three-line CCD sensor, it is necessary to reduce the plate thickness of the dichroic prism. Therefore, when the light beam reflecting surface or the color selecting surface is formed on the translucent member by a method such as vapor deposition, there is a problem that the translucent member warps and the image forming surface is not stable. Further, when the arrangement pitch of each line CCD sensor is small, such as when using a three-line CCD sensor, it is necessary to form a plurality of color selection surfaces adjacent to each other corresponding to the arrangement pitch of each line CCD sensor. There is a problem in that it is difficult to form the surface, which increases the cost. Furthermore, when a light ray enters the prism or emerges from the dichroic prism, refraction of the light occurs and the optical path is changed, which causes a problem that the image plane shifts.

Further, in the optical system using the color separation means disclosed in Japanese Patent Laid-Open No. 2-115816, the shape of the optical system is changed and redesigned each time the pitch between the CCD sensors used is changed. However, there is a problem that the manufacturing cost becomes high.

Further, the light beam color-separated by the color separation means disclosed in Japanese Patent Laid-Open No. 2-115816 is
Photoelectric conversion is performed by each line CCD sensor. However, since the sensitivity of each line CCD sensor differs depending on the wavelength of the light beam, when the color-separated light beam is photoelectrically converted by each line CCD sensor, the level of each output signal becomes different for each color. Therefore, for example, when performing 256-gradation A / D conversion processing on these output signals, A
When the reference voltage for the A / D conversion is set, the A / D conversion using the 256-gradation full scale cannot be performed for the signal having a relatively low output level, and the gradation is deteriorated. It becomes a processing problem.

Furthermore, a part of the light beam emitted from the optical path length correction means used in the color separation means disclosed in Japanese Patent Laid-Open No. 2-115816 is reflected by the cover glass of each line CCD sensor. , A part of this reflected light is reflected again at the exit surface of the optical path length correction means and each line C
When the light enters the CD sensor, stray light appears in the output image, which causes a problem. Similarly, in the case of the optical system using the color separation means disclosed in Japanese Patent Application Laid-Open No. 2-115816, the dimensional accuracy of the color separation means is adjusted to completely match the pitch between the photoelectric conversion elements of the photoelectric conversion means. There is also a problem that the manufacturing cost must be high because it has to be extremely high.

An object of the present invention is to optically prevent color misregistration of an image due to detection of each color component of image information at different reading positions in a color image reading apparatus using the 3-line CCD method. Moreover, it is an object of the present invention to provide a color image reading device capable of just-focusing color image information on a plurality of detecting portions without using a special correction means and forming an image on the same pixel of each line CCD.

[0016]

In order to solve the above-mentioned problems, the invention according to claim 1 provides a light source means for irradiating an object to be read with a light beam, and an optical means for transmitting the light beam from the object to be read. And an optical element for dividing the light beam from the optical means into a plurality of light beams separated by a predetermined distance, and a plurality of optical elements provided at positions for receiving each of the light beams divided by the optical element through different color filters. A detection means of which the detection part is formed on a single substrate; and an imaging optical element that is provided on the light incident side of the optical element and forms an image of a light beam split by the optical element on the detection part. In the image reading apparatus including the optical element, the optical element emits a light beam to the surface on the long side.
Half-mirror surface is formed to transparently and reflecting mirror surface for reflecting a rectangular prism reflection preventing film is formed on the other two short sides, a light beam to the surface opposite the surface of the long side of the rectangular prism is adhesive and a total reflection optical element formed, the consist half mirror surface and a flat refracting member made form between the mirror surface, and the right angle prism, wherein a flat refracting member, the two and adhesive have a substantially identical refractive index to, the flat refraction member, the thickness of the adhesive
Is the arrangement pitch of the detection unit of the detection means
Is formed to a thickness corresponding to.

According to a second aspect of the present invention, the light source means for irradiating the object to be read with the light beam, the optical means for transmitting the light beam from the object to be read, and the light beam from the optical means are separated by a predetermined distance. An optical element for splitting into a plurality of luminous fluxes, and a position for receiving each of the luminous fluxes split by this optical element,
A plurality of detection units provided via different color filters are arranged on a single substrate, and a light beam provided on the light incident side of the optical element and split by the optical element is detected on the detection unit. the image reading apparatus comprising an imaging optical element for imaging, the said optical element is a half mirror surface is formed to transparently and reflections of the light on the surface of the long side,
A right angle prism with an antireflection film formed on the other two short sides,
An array of the detection unit of the detection means between a total reflection optical element having a mirror for reflecting a light beam formed on a surface facing the long side of the rectangular prism and the half mirror surface and the mirror surface. And a flat plate-shaped refraction member having a thickness corresponding to the pitch, wherein the flat plate-shaped refraction member is made of an adhesive agent for adhering the right-angle prism and the total reflection optical element, and The agent has substantially the same refractive index as the right-angle prism.

[0018]

According to the present invention, when reading a color image, the image information of a single line obtained by the optical means is
An optical element using a prism disperses and forms an image on a plurality of detectors arranged at a predetermined pitch, that is, an image sensor. Therefore, the deviation of each color component caused by the arrangement pitch peculiar to the plurality of arranged detection units does not occur.

Further, when the spectral image information is imaged on a plurality of arranged color line image sensors, it can be imaged on the same pixel of each color line image sensor.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an image reading apparatus according to an embodiment of the present invention. As shown in FIG. 1, the image reading device 2 includes a first reflection unit 20 and a first reflection unit 20 which guide a reflected light beam from a document surface into the second reflection unit 30 by reflecting the light beam once inside the image reading device 2. second reflection unit 30 for guiding to the image reading unit 40 that reads the image information by reflected twice in them rays from, and a drive mechanism described later, these units 20, 30, 40 housed The housing 10 is provided.

The housing 10 is provided with a reading window 14 having a flat surface on which an original is placed, and an original pressing member 12 for bringing the original placed on the reading window 14 into close contact with the reading window. Further, the housing 10 is provided with a document holder 12
And a drive mechanism (not shown) for moving the reading window 14 on the first reflection unit 20 in the sub-scanning direction Sa, in which an image for reading image information by forming image information from the document surface G of the document is formed. The reading unit 40 and a signal processing unit (not shown) that processes signals from the image reading unit 40 and outputs the processed signals as image signals are provided. Next, each device or unit shown in FIG. 1 will be described in detail.

The reading window 14 arranged on the upper part of the housing 10 is a transparent plate made of glass, for example, and is arranged substantially horizontally. In this reading window 14,
In order to clearly take out the image information to be read, the document is turned upside down, that is, the document surface G is placed inside the housing 10 and the document surface G of the document is placed so as to be in close contact with the flat surface of the reading window 14. It Further, the document retainer 12 and the reading window 14 are moved along the sub-scanning travel Sa on the housing 10 by a drive mechanism (not shown).

The first reflecting unit 20 installed substantially parallel to the reading window 14 illuminates the original surface G of the original that is in close contact with the reading window 14 as shown in FIG. 2, and a light beam from the lamp 24. A concave reflecting plate 26 for efficiently illuminating the original surface of the original, a first mirror 22 for guiding a part of a reflected light beam reflected from the original surface G of the original to a second reflecting unit 30, an original surface G of the original. A slit 27 for narrowing the reflected light from the lamp to a predetermined width, and a light blocking plate 28 for blocking the light source light from the lamp 24 so as not to directly enter the first mirror 22 are provided. The lamp 24, the reflecting plate 26, the slit 27, the light shielding plate 28, and the first reflecting mirror 22 that guides a part of the reflected light from the document surface G to the second reflecting unit 30, the document pressing member 12 and the reading window 14 move, respectively. Is extended in the scanning direction orthogonal to the sub-main scanning direction Sa, and the first surface is moved at a predetermined position in the sub-main scanning direction Sa so that the document surface can be completely scanned.
It is fixed to the reflection unit 20.

As shown in FIG. 1, the second reflection unit 30 reflects the reflected light beam from the document surface G of the document twice and guides it to the reading section for reading the image information.
2, 34 are provided. The second and third mirrors 32,
34 is fixed in the second reflection unit 30 so as to extend in the main scanning direction. Here, the second mirror 32
Are arranged parallel to the first reflecting mirror 22, and the third mirror 34 is arranged so as to be orthogonal to the first and second reflecting mirrors 22 and 32.

The image reading unit 40 has an image forming lens unit 42 in which a plurality of lenses are combined with a light beam containing image information guided from the second reflecting unit 30, and a photolytic function shown in FIG. It is guided to the image reading element shown in FIGS. 4 and 5, that is, the three-line CCD sensor 46 through the photolytic element 44, converted into an electric signal by the three-line CCD sensor 46, and subjected to predetermined processing in the signal processing unit. Then, the image is sent to an external image forming apparatus, a storage device or the like (not shown).

As shown in FIG. 4, the 3-line CCD sensor 4
6 has three line CCD sensors 46r, 46g, 46b extending in the main scanning direction. As shown in FIG. 5 which is an enlarged view of the area A shown in FIG.
In r, 46g, and 46b, the same number of pixels that receive light are arranged in the same direction, that is, in the main scanning direction. Further, 47r, 47g, 4 arranged in a direction perpendicular to the main scanning direction in FIG. 5, that is, in the sub scanning direction.
Each pixel 7b is a pixel that receives light from the same point on the document surface. Similarly, the pixels on the line CCD sensors 46r, 46g, and 46b arranged in the sub-scanning direction receive light from a certain point on the document surface. This line CCD
As shown in FIG. 5, 46b, 46g, and 46r each have a pixel size of 14 μm square. So, for example,
When reading a document with a resolution of 4 lines / mm, the size of the read pixels on the document surface G is 250 μm square,
The magnification of the imaging lens 42 shown in FIG. 1 is 1 / 17.86.
Is set to.

In the 3-line CCD sensor 46, C is provided on the side of each line CCD sensor 46r, 46g, 46b.
A CD charge transfer path is provided, which allows a line CCD
The sensors 46r, 46g, and 46b are arranged with a predetermined space. This arrangement interval, that is, the pitch p thereof is peculiar to the 3-line CCD sensor, and is set to about 168 μm in this embodiment.

On the light incident surface of the line CCD sensor 46r, a red filter L1 having a spectral characteristic FR shown in FIG.
The light incident surface of the CD sensor 46g is provided with the green filter L2 having the spectral characteristic FG shown in FIG. 6, that is, the characteristic of transmitting green light, and the light incident surface of the line CCD sensor 46b is shown in FIG. A blue filter L3 having a spectral characteristic FB, that is, a characteristic of transmitting blue light is provided. This 3-line CCD 46 is further provided with each line CC
A cover glass 48 for protecting the detection surface of D is provided on the front surface of the detection surface.

Further, in the above-mentioned embodiment, in order to prevent ghosts from being produced in the reproduced image, the intervals between the line CCD sensors 46r, 46g and 46b, that is, the pitch p.
The width w of the slit 27 provided in the first reflection unit 20 corresponding to the above, more precisely, the line reading width of the original image is set by the magnification a of the imaging lens 42 and the arrangement pitch p of the line CCD sensors. The width s of the light detection surface of each CCD sensor, the width w of the slit 27, and the pitch p are determined so as to satisfy the following relationships. w <(2p−s) · a From this relational expression, in the embodiment of the present invention, the slit width w
Is set to 3 mm.

[0031] To explain why such a slit 27 is provided. The light ray L reflected from the document surface G by using the above-mentioned photolytic element 44 is line CCD sensor 46.
When disassembling corresponding to the array pitch p of b, 46g, and 46r, if the slit 27 is not arranged in the above-described first reflecting unit 20, the following problems occur due to the structure of the photolytic element 44. That is, as shown in FIG. 7, the area P1
When scanning the document surface G1 of a document having
If the reflection unit 20 is not provided with the slit 27, as shown in FIG.
The primary reflected light L1, secondary reflected light L2, and tertiary reflected light L3 having the image information segments of the areas P1 to P7 are respectively directed to b, 46g, and 46r at the same time, and the line C
The area P is provided in each of the CD sensors 46b, 46g, and 46r.
Adjacent three image information segments 1 to P7 are simultaneously imaged, and a kind of ghost phenomenon occurs. However, when the first reflecting unit 20 is provided with the slit 27 having a predetermined width w, as shown in FIG.
Even if the reflected lights L1, L2 and L3 are read at the same time, the area P1
From P7 to P7 other than the image segment P4 are slits 27.
Only the image segment P4 within the area P1 to P7 is blocked by the line CCD sensors 46b, 46g, 4
It is incident on each of 6r. The optical signal that causes the ghost phenomenon described above is not imaged on the line CCD sensor,
Therefore, the ghost phenomenon does not occur.

The illumination light beam Lw from the lamp 24 arranged in the first reflecting unit 20 is guided to the original surface G of the original directly or after being reflected by the reflecting plate 26, and efficiently illuminates the original surface G. . The document surface G has the condensed illumination light beam Lw.
It is illuminated by and emits reflected rays in unspecified directions. A part of the light ray L reflected from the document surface G passes through the slit 27 as shown in FIG.
First, the first fixed unit is fixed to the first reflection unit 20.
The light is reflected by the mirror 22 in the sub-scanning direction Sa and is incident on the second mirror 32 fixed to the second reflection unit 30. Here, the light shielding plate 28 causes light rays other than the reflected light ray L from the document surface G of the document to directly and indirectly.
It is prevented to be led to 2.

The light ray L incident on the second mirror 32 is reflected at a right angle toward a third mirror 34 arranged so as to be orthogonal to the second mirror 32, and is incident on the third mirror 34. The light ray L incident on the third mirror 34 is reflected at a right angle again, is directed in the substantially sub-scanning direction Sa, and is guided to the image reading unit 40. That is, the reflected light ray L including the image information from the document surface G is guided to the image reading unit 40 by being bent twice by 180 degrees by the second reflection unit 30.

The light ray L guided to the image reading unit 40
Are focused by the lens unit 42. As shown in FIG. 3, this converging light beam is decomposed by the photolytic element 44 into color components of image information, that is, blue, green, and red components Lb, Lg, and Lr, and at the same time, in the photolytic element 44. It is reflected at different positions and its direction is approximately 9
It is folded back at 0 ° and guided to the image reading element, that is, the 3-line CCD sensor 46. Decomposed reflected rays Lb, Lg,
Lr is an image reading element, that is, the 3-line CCD sensor 4
The image is formed on each of the line CCD sensors 46r, 46g, and 46b equipped with color separation filters of 6 and converted into an electric signal.

The photolytic element 44 shown in FIG. 3 comprises first and second right-angled prisms 44h and 44m each having a right-angled isosceles triangular cross section, and a plate-shaped refracting member 45 provided therebetween. Has been done. Flat refraction member 4
5 has a thickness t corresponding to the arrangement pitch of the line CCD sensors, and the long side surface of the first rectangular prism 44h has
A half mirror surface is formed as a photolytic surface for transmitting and reflecting light rays by a method such as vapor deposition, and an antireflection film, that is, an AR coat film is provided on the other two short sides. The long-side surface of the second right-angle prism 44m facing the long-side surface of the first right-angle prism 44h has a total reflection surface that reflects light rays,
That is, the mirror surface is formed by a method such as vapor deposition.
The first right-angled prism 44h, the second right-angled prism 44m, and the plate-shaped refraction member 45 are joined to each other by optical contact or an adhesive.

The light ray L guided to the photolytic element 44 is
First, a part of the light rays, that is, the primary reflected light Lb is reflected by the half mirror surface, and the remaining light rays that have passed through the half mirror surface are reflected by the total reflection surface, and a part of the light rays, that is, the second light rays. The next reflected light Lg is transmitted. The rest of the light reflected by the half mirror surface is reflected by the total reflection surface, and a part of the light rays, that is, the tertiary reflected light Lr is transmitted by the half mirror surface. In this way, the reflected light Lb, L
g and Lr are decomposed at equal intervals.

The light beam thus decomposed is emitted from the photolytic element 44 and guided to the 3-line CCD sensor 46. And the cover glass 48 of the 3-line CCD sensor
A part of the light is reflected by the laser beam, and the reflected light beam is again incident on the photolytic element 44. Since the incident surface at this time is the AR coating surface, the light beam is reflected here and the three lines C again.
It is prevented from being guided to the CD sensor 46. That is, deterioration of an image is prevented by reflection of light rays from the cover glass 48 of the 3-line CCD sensor 46.

Each reflected light beam Lb, Lg, Lr is decomposed.
The spacing is a flat plate-shaped refraction member forming the photolytic element 44.
It is defined by the thickness t of 45. In this example, 3
Each reflected light beam Lb, Lg, Lr of the line CCD sensor 46
Line CCD sensors 46b, 46g, 46r corresponding to
The array pitch p of is unique to the CCD sensor (immediately
The pitch p is constant and cannot be changed. ) Is
Therefore, the thickness t of the plate-shaped refraction member 45 is equal to the arrangement pitch.
It is formed to have a thickness corresponding to p. Half turn back ray L
The mirror surface and the total reflection surface reflect the reflected light ray L at a right angle.
Therefore, they are arranged at an angle of 45 ° with respect to the optical axis. Servant
Thus, the thickness t of the flat plate-shaped refraction member 45 is t = p / 2^1/2 Stipulated in.

First right-angle prism 44 of photolytic element 44
The h and the plate-shaped refraction member 45 are preferably made of the same material. If the materials of the first right-angled prism 44h and the plate-shaped refraction member 45 are different, the following unfavorable problems occur. That is, in FIG. 10 showing how light rays are decomposed by the photolytic element 44, if the refractive indices of the first rectangular prism 44h and the flat refracting member 45 are different, the photolytic element 44 is indicated by the solid line. The reflected light beam L from the original document G traveling inside is refracted, and the desired light path shown by the broken line in FIG. 10 does not travel. However, if the first right-angle prism 44h and the plate-shaped refraction member 45 are made of the same material, such refraction of light rays can be prevented. Therefore, as shown by the broken line in FIG.
The light rays are decomposed according to the arrangement pitch of the CD sensors, and the reflected light rays L are reflected on the line CCD sensors 46r, 46g, 46b.
b, Lb, and Lr are surely directed.

The half mirror surface of the photolytic element 44 is preferably formed of a dielectric multilayer film. This is based on the following reasons. Generally, when a half mirror surface is formed of a metal film, when light enters the half mirror surface, light absorption occurs on this surface. This absorption varies depending on the film thickness and the type of film, but if this half mirror is made of a chrome film or an aluminum film, the total incident light is 3%.
0 to 40% is not transmitted or reflected and is absorbed by the film. As a result, the amount of light guided to the 3-line CCD sensor 46 is reduced significantly. To prevent this decrease in light intensity, it is necessary to take measures such as increasing the light intensity of the lamp that illuminates the original, but this increases the power consumption of the device and increases the amplification of the sensor output signal. There is also a method of raising the image signal level to the above, but a decrease in the S / N ratio is unavoidable, and as a result, there arises a problem that image quality is deteriorated. On the other hand, when the half mirror surface is formed by the dielectric multilayer film, the dielectric material that is the material of the film hardly absorbs light, and thus the above-mentioned measures are unnecessary. From this, the half mirror surface is preferably formed of a dielectric multilayer film.

As shown in FIGS. 11 and 12, the plate-shaped refraction member 45 is attached to the prisms 44h and 44m with an adhesive 45.
In the case of joining with a and 45b, the accuracy of the thickness of the flat refracting member 45 can be satisfied by adjusting the thickness of the adhesive. The reason for this will be described with reference to FIGS. 11 and 12. In FIG. 11, broken lines indicate reflected light rays Lb, Lg, and Lr from the mirror surface when the plate-shaped refracting member 45 has a uniform thickness and is formed on an ideal mirror surface as indicated by a dashed line. Shows reflected light rays Lb, Lg, and Lr from the mirror surface when the flat refracting member 45 is formed on the mirror surface having an uneven thickness. As shown in FIG. 11, when the half mirror surface and the mirror surface are not parallel, the reflected lights Lb, Lg, Lr are not imaged on the CCD sensors 46g and 46r. Usually, as the distance between the photolytic surface, that is, the half mirror surface and the sensor 46 increases, the thickness of the flat plate-shaped refracting member 45 is required to have high accuracy. Therefore, the first prism 4
4h and the plate-shaped refraction member 45, and the second prism 44m and the plate-shaped refraction member 45 are adhered to each other using adhesives 45a and 45b having the same refractive index as that of the plate-shaped refraction member 45. By adjusting, the plate-shaped refraction member 45
It is possible to satisfy the accuracy regarding the thickness of the. By adjusting the thickness of the adhesive, it is possible to secure the parallelism between the half mirror surface and the mirror surface as shown in FIG. 12, and it is possible to read an image without deviation. However, in order to enable such adjustment, the thickness of the flat plate-shaped refraction member 45 needs to be thinner than the thickness t determined by the arrangement pitch of the sensors by a value corresponding to the thickness of the adhesive. is there.

The plate-shaped refracting member 45 is made of an adhesive, for example, an ultraviolet curable adhesive, and by adjusting the compounding ratio of a plurality of resins, the same refractive index as that of the prism (nD = 1.475 in the case of quartz glass). ) May be given. This is because even if the arrangement pitch p of the 3-line CCD sensor is changed for each device, it is not necessary to change the specifications of other optical parts only by changing the thickness t of the adhesive agent, which is in terms of manufacturing and cost. This is because it is very advantageous. Further, when the array pitch p of the sensors is narrow, the plate-shaped refracting member 45 becomes very thin, but when glass is used for the plate-shaped refracting member 45,
Because of the thinness, the plate-shaped refracting member 45 is warped or the thickness becomes nonuniform, so that the reflected lights Lb, Lg, and Lr may not be correctly imaged on the sensor surface. However, when the plate-shaped refraction member 45 is made of an adhesive, the parallelism of the adhering surface of the prism is maintained, and the deviation that may occur in the image information is prevented.

The prisms 44h and 44m and the plate-shaped refraction member 45 may be joined by an optical contact method without using an adhesive material. The problems and accuracy of using the adhesive will be further discussed with reference to FIG. FIG. 13 is an enlarged view of the light beam splitting surface of the optical element 44 shown in FIG. In FIG. 13, the first prism 44h, the plate-shaped refraction member 45, and the second prism 44m.
And the plate-shaped refraction member 45 are respectively
It shows a state of being adhered with adhesives 45a and 45b having the same refractive index. Here, when the thickness of the adhesive 45a becomes non-uniform as shown in FIG. 13 and its mirror surface is tilted, the half mirror surface and the mirror surface are not parallel to each other, and the reflected light ray Lg from the document surface G is lost. , Lr are not imaged on the CCD sensors 46g and 46r.
Further, as the distance between the photolytic surface and the sensor 46 increases, the thickness of the adhesives 45a and 45b is required to have higher accuracy. Therefore, the first prism 44h and the plate-shaped refraction member 45, and the second prism 44m and the plate-shaped refraction member 4
The first prism 44h and the plate-shaped refraction member 45, and the second prism 44m and the plate-shaped refraction member 45 are formed by using an optical contact method for bringing the respective adhesion surfaces into a vacuum state without using an adhesive agent for the adhesion of No. Can be completely adhered. Due to this optical contact, the parallelism between the half mirror surface and the mirror surface depends only on the accuracy of the thickness of the flat plate-shaped refracting member 45, and a more accurate photolytic surface can be obtained.

The half mirror surface and the mirror surface are formed only in the central portion of the long side surface of the prism 44h and the central portion of the long side surface of the prism 44m.
The peripheral part of the prism in which the half mirror surface of h is not formed is brought into contact with one surface of the flat plate-shaped refracting member 45 in a vacuum state, and the two are joined by the optical contact method. The mirror surface of the second rectangular prism 44m may be attached to the other surface by optical contact or an adhesive using the peripheral portion of the prism. This is based on the following reasons. If the half mirror surface or the mirror surface is formed on the entire surface of the prism, there are the following problems. That is, when the photolytic element 44 is bonded by optical contact, the bonding surface is not in a vacuum state depending on the type of the half mirror surface or the multilayer film forming the mirror surface, and optical contact cannot be performed. Further, when the photolytic element 44 is bonded with an adhesive, an error occurs in the photolytic pitch due to the thickness of the adhesive, and the nonuniformity of this thickness deteriorates the accuracy of parallelism between the half mirror surface and the mirror surface. Therefore, the decomposed rays Lb, Lg, and Lr are generated by the CCD sensor 46 of each line.
The positions where the images are formed on b, 46g, and 46r are displaced.
However, if the half mirror surface and the mirror surface are formed in the central portion of the prism, optical contact using the peripheral portion of the prism becomes possible. When the photolytic element 44 is bonded with an adhesive, the prism can be bonded by applying the adhesive to the peripheral portion of the prism. Therefore, by forming the thickness of the adhesive to be the same as the thickness of the multilayer film as the mirror surface, the thickness of the adhesive does not affect the photolytic pitch. The photolytic element 44 is capable of decomposing light rays from the document at a predetermined pitch.

Generally, line CCD sensors 46r, 46
The detection sensitivities of g and 46b are wavelength-dependent, and the detection signal levels generated from each of them differ even when light rays having the same light intensity level are incident. When the line CCD sensor 46b that detects a blue ray has the lowest sensitivity and the line CCD sensor 46r that detects a red ray has the highest sensitivity, the reflected ray from the half mirror having the highest light amount among the decomposed rays. The line CCD sensor 46b is arranged so as to be able to receive Lb, and the line CCD sensor 46r is arranged so as to be able to receive the reflected light beam Lr from the half mirror having the smallest light amount among the decomposed light beams. Further, in such a case, if necessary, the output signal level of the line CCD sensor 46b can be raised, and as a result, the S / N ratio of the image data can be improved. On the contrary, if the line CCD sensor 46r has the lowest sensitivity, the CCD sensor 46r
By arranging in the order of r, 46g, 46b, C
The output signal level of the CD sensor 46r can be increased. That is, in the above optical system, the photolytic element 44
When the transmission and reflection ratios of the half mirror surface are equal (transmittance 50%, reflectivity 50%, loss 0%), the light intensity as the light beam is reflected and transmitted in the optical element 44 is Lb, Lg. , Lr in that order. Therefore, when the line CCD sensors 46r, 46g, and 46b have a characteristic that the detection sensitivity with respect to blue, green, and red light rays increases in that order, the line CCD sensors in that order.
Sensors 46r, 46g, 46b are arranged, and the corresponding light rays Lb, Lg, Lr are line CCDs as shown in FIG.
By making the light incident on the sensors 46r, 46g, and 46b, the difference in detection sensitivity is corrected to some extent.

Further, the line CCD sensors 46r, 46
It is preferable that the filters provided on the light incident surfaces of g and 46b have a light transmission characteristic that corrects this sensitivity characteristic. By adjusting the transmittance of the blue, green and red filters, the line CCD sensors 46r, 46g,
The output signal level from 46b can be approximated to the color components of the original image, and the reproducibility of the original image can be improved.

Further, the light quantities of the decomposed light rays Lb, Lg, Lr are set to different values depending on the transmittance of the half mirror surface, as is clear from the decomposition process. When a xenon lamp that passes an infrared cut filter is used as the lamp 24 that illuminates the document surface G, the sensitivities of the line CCD sensors 46b, 46g, and 46r are approximately 7.2, 8.5, and 8.8 [V], respectively. / lx ・ sec] is obtained experimentally. In consideration of these sensitivities and the light amounts of the decomposed rays Lb, Lg, and Lr, the CCD sensors 46b and 46 of the respective line sensors are considered.
The transmittance of the half mirror surface is set so that the difference between the output signal levels of g and 46r is minimized. In this example, assuming that the amount of light incident on the photolytic element 44 is 10 [lx] and the integration time of the 3-line CCD sensor 46 is 10 [msec], the output signal levels of the respective line CCD sensors 46b, 46g, 46r are It is almost as shown in Table 1. Therefore, in this example, this transmittance is set to about 59% according to Table 1. Further, even when the sensitivity of the lamp or the line CCD sensor that irradiates the document surface G is different from the above example, the optimum transmittance can be obtained as in the above example.

[0048]

[Table 1] By the way, the optical system of the reading apparatus shown in FIG. 1 employs a telecentric system.

The telecentric system is a generally well-known optical system, and is an optical system adjusted so that all the light rays emitted from the lens are parallel to the optical axis. For example,
"How to use optical components for optronics technology utilization and notes" issued by Optronics Co., Ltd. (Tetsuo Sueda,
Its optical properties and usage are described in May, 1990, supplemented and revised version).

FIG. 14 shows how the light rays emitted from the emission portion of the imaging lens 42 included in the image reading unit 40 of the reading apparatus shown in FIG. 1 are imaged on the 3-line CCD sensor 46. Has been done.

The light rays reflected from the original reflected by the third mirror 34 included in the second reflecting unit 30 are guided to the image forming lens 42. The imaging lens 42 is an optical system, that is, a telecentric optical system, in which a light beam incident on the photolytic element 44 is substantially parallel to the main axis of the optical system. The light reflected from the document is generated by the imaging lens 42.
Is converted into a focused ray. Further, the light is guided to the photolytic element 44 in substantially parallel to the main axis of the optical system. Therefore, a light beam from a certain point on the document surface is decomposed by the photolytic element 44, and then is arranged on the 3-line CCD sensor 46 in the pixel rows aligned in the sub-scanning direction, for example, 47b, 4b.
The light is simultaneously received by 7g and 47r.

FIG. 15 shows how a light beam emitted from the exit portion of the imaging lens using an optical system other than the telecentric optical system is imaged on the 3-line CCD sensor.

The light rays from the document surface are required to be decomposed by the photolytic element 44 in accordance with the arrangement pitch of each line CCD sensor. There's a problem. That is, since the imaging lens is not a telecentric optical system, each resolved ray is
It is not parallel to the main axis of the optical system but has an angle. Therefore, a light beam from a certain point on the document surface is not received by the pixel rows that are lined up in the sub-scanning direction on the 3-line CCD sensor at the same position in the main scanning direction, and as a result, a color shift occurs in the output image. Misalignment occurs. In order to remove the color misregistration of the output image, it is necessary to provide a means for correcting the optical path length of each decomposed light beam generated at the time of photodecomposition,
The cost will be high. However, by constructing the imaging lens using a telecentric optical system, it becomes unnecessary to provide such an optical path length correction means.

Considering the optical path lengths of the reflected light rays Lb, Lg, and Lr, as is clear from FIG. 3, when the optical path length (DLb) of the reflected light ray of the blue component is used as a reference, the reflected light rays of the green component are The optical path length is DLg (= DLb + p) and the optical path length of the reflected ray of the red component is DLr (= DLb + 2p), and the optical path length differs for each color by the sensor pitch (p).

As shown in FIG. 16, when the sensor is installed at a position where the blue component image is just in focus, the red component image and the green component image are blurred. Therefore, as shown in FIG. 17, the imaging lens 42 is designed so that the imaging distances for the blue, green, and red components are different for each sensor pitch (P). FIG. 18 shows the default of the optical system lens which is one embodiment of the present invention.
An example of the dregs characteristic is shown. The horizontal axis is the defocus position, and the position where the resolution (MODULATION, vertical axis) is maximum when the e-ray (single wavelength light of wavelength 546.1 mm) is incident is set as the origin. In the figure, three colors of single wavelength light corresponding to R, G and B colors (g line: 4
Defocus characteristics of 35.8 mm, e line: 546.1 mm, c line: 656.3 mm) are shown.

As is apparent from the figure, the positions of the maximum resolutions of the three colors are displaced by the sensor pitch of 168 μm in this embodiment. Therefore, each color image signal is imaged on the 3-line CCD sensor in a just focus.

In the above embodiment, the case where the light beam reflected from the original is detected has been described.
It is obvious that the present invention can be applied to an apparatus which can provide a light source on a document and read a light beam transmitted through the document.

Further, in the above-mentioned embodiment, the example of the line CCD sensor is described as the detector for detecting the light beam, but the detector of the image reading apparatus of the present invention is not limited to the line CCD sensor. Obviously, other detectors may be used instead.

[0059] Further, in the embodiment described above, has been described for the three detector is a detector which is provided for that detect light rays separated into three, not limited to the three detection section, 2 It is obvious that two or more light beams are separated and two or more detection units for detecting these light beams may be provided in the detector.

[0060]

As described above, according to the present invention,
Unique to multiple line image sensors, because the image information of a single line in the main scanning direction is decomposed by optical elements at intervals corresponding to the array pitch of the line image sensor equipped with color separation filters. The deviation of each color component due to the arrangement pitch of can be removed. Therefore, a storage means for storing information from a plurality of line image sensors arranged, a mechanism for correcting the deviation of each color component, or a control device therefor becomes unnecessary.

Further, the focal length of the light beam split by the optical element is varied on the light incident side of the optical element, and an optical beam having a wavelength corresponding to the spectral sensitivity characteristic of the detecting section is formed on the detecting section. Since the focusing optical element for forming an image is provided, each color image signal is just focused on each detector,
It is possible to obtain a high-resolution image without using special correction means.

Further, since the parallel optical element for making the light beam emitted from the optical means and incident on the optical element parallel to the main axis of the optical system is provided, the color is spread over the entire area of the image information on the document surface. An output image without deviation can be obtained. Further, since the right-angle prism, the plate-shaped refraction member, and the adhesive for adhering the both have substantially the same refractive index, the reflected light beam from the document can be advanced along a desired optical path, and the image reading accuracy can be improved. Can be improved. In addition, the flat plate-like buckling
The thickness of the folding member corresponding to the arrangement pitch of the detection part of the detection means
To contact wear and minute only thin to rectangular prism corresponding to the thickness of the adhesive than by adjusting the thickness of the adhesive, to maintain the parallelism of the adhesive surface of the half-mirror surface and the mirror surface, The image reading accuracy can be improved. Furthermore, since the flat refracting member is made of an adhesive that bonds the right-angle prism and the total reflection optical element, even if the flat refracting member is thin, the parallelism between the bonding surfaces of the half mirror surface and the mirror surface can be maintained. It can be maintained and the image information can be read accurately.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a color image reading device according to an embodiment of the present invention.

2 is a cross-sectional view showing a first reflection unit used in the color image reading apparatus of FIG.

FIG. 3 is a sectional view showing a photolytic element used in the color image reading apparatus of FIG.

4 is a schematic plan view of a 3-line CCD used in the color image reading apparatus of FIG.

5 is a partially enlarged plan view showing the 3-line CCD of FIG. 4. FIG.

6 is a graph showing spectral characteristics of a color separation filter used in the 3-line CCD shown in FIG.

FIG. 7 is a plan view showing an area on a document read by the color image reading apparatus of FIG.

8 is an image information and line CCD of an area on the original of FIG.
The side view of the reading unit which shows the relationship with a sensor.

FIG. 9 is a line CCD with image information of an area on the original of FIG.
The side view of the reading unit which shows the relationship with a sensor.

10 is an explanatory diagram showing a ray trace when the first right-angle prism and the translucent member have different refractive indexes in the photolytic element of FIG.

FIG. 11 is an explanatory view showing a locus of a reflected light ray when the light transmissive member in the photolytic element of FIG. 3 is formed with uniform and nonuniform thickness.

12 is an explanatory view for ensuring the parallelism between the half mirror surface and the mirror surface by adjusting the thickness of the adhesive in the photolytic element of FIG.

13 is a first prism in the photolytic element of FIG.
Sectional drawing which shows the structure which the translucent member and the 2nd prism were each adhere | attached by the adhesive agent which has the same refractive index.

14 is an explanatory diagram showing a state in which a light beam emitted from an emission unit of an imaging lens is imaged on a 3-line CCD sensor when a telecentric optical system is adopted in the color image reading apparatus of FIG. .

15 is a color image reading apparatus of FIG. 1, when an optical system other than a telecentric optical system is adopted, the light rays emitted from the emission portion of the imaging lens are 3-line CCDs.
Explanatory drawing which shows a mode that an image is formed on a sensor.

16 is an explanatory diagram illustrating the reason why a difference occurs in the optical path of the ray trace of the reflected ray within the photolytic element in the color image reading apparatus of FIG.

FIG. 17 is an explanatory diagram for explaining an optical system using a lens system that corrects a difference between ray trajectories of reflected rays generated in the photolytic element in the color image reading apparatus of FIG. 1.

18 is a graph showing the defocus characteristic of the lens system of FIG.

[Explanation of symbols]

2 ... Image reading device, 10 ... Housing, 14 ... Reading window,
20 ... 1st reflection unit, 22 ... 1st mirror, 24 ... Lamp, 26 ... Reflector, 27 ... Shading plate, 28 ... Slit,
30 ... 2nd reflection unit, 32 ... 2nd mirror, 34 ... 3rd mirror, 40 ... Image reading unit, 42 ... Imaging unit, 44 ... Photolytic element, 46 ... 3-line CCD sensor.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenichiro Yamada               1-3-6 Yoyogi, Shibuya-ku, Tokyo Nikko Toko               Ware corporation                (56) References JP-A-4-65965 (JP, A)                 JP-A-3-201861 (JP, A)                 JP-A-2-214370 (JP, A)                 JP-A-57-45516 (JP, A)

Claims (2)

(57) [Claims] 1. A light source means for irradiating an object to be read with a light beam, an optical means for transmitting a light beam from the object to be read, and a light beam from the optical means is divided into a plurality of light rays separated by a predetermined distance. An optical element, and a detection means in which a plurality of detection sections provided via different color filters are formed on a single substrate at a position for receiving each of the light beams divided by the optical element, An image reading apparatus comprising: an image forming optical element which is provided on the light incident side of the element and forms an image of a light beam split by the optical element on the detection unit, wherein the optical element has a long side surface. half-mirror surface is formed to transparently and reflections of the light, and reflects the light beam and rectangular prism antireflection film is formed on the other two short sides, the surface opposite the surface of the long side of the rectangular prism Totally reflected light with mirror surface And Manabu element, wherein consists half mirror surface and a flat refracting member made form between the mirror surface, and the right angle prism, wherein a flat refracting member, and an adhesive for bonding the both have a substantially same refractive index, the flat refraction member thickness plus the thickness portion of the adhesive
Corresponds to the arrangement pitch of the detectors of the detector.
An image reading device characterized by being formed to a thickness . 2. A light source means for irradiating an object to be read with a light beam, an optical means for transmitting a light beam from the object to be read, and a light beam from the optical means is divided into a plurality of light rays separated by a predetermined distance. An optical element, and a detection unit in which a plurality of detection sections provided via different color filters are formed on a single substrate at a position for receiving each of the light beams divided by the optical element, An image reading apparatus comprising: an image forming optical element which is provided on the light incident side of the element and forms an image of a light beam split by the optical element on the detection unit, wherein the optical element has a long side surface. half-mirror surface is formed to transparently and reflections of the light, and reflects the light beam and rectangular prism antireflection film is formed on the other two short sides, the surface opposite the surface of the long side of the rectangular prism Totally reflected light with a mirror formed An element and a flat plate-shaped refraction member formed between the half mirror surface and the mirror surface to a thickness corresponding to the arrangement pitch of the detection units of the detection means, wherein the flat plate-shaped refraction member is An image reading apparatus, which is made of an adhesive agent for adhering a right-angle prism and the total reflection optical element, and the adhesive agent has substantially the same refractive index as the right-angle prism.