JPH01194750A - Image reader - Google Patents

Abstract

PURPOSE:To realize the stabilization of image reading accuracy by providing a positioning plane abutted with one side end of a color separation prism and performs the positioning of an image in a main scan direction at one end of the positioning member of an image pickup lens. CONSTITUTION:An assembled and adjusted image pickup unit is positioned and fixed on a lens supporting table 245. And a part of the lens barrel of the image pickup lens 210 is sunk in the aperture part 245a of the lens supporting table 245. Lens fixing arms 246A and 246B are fixed with screws at both sides of the upper plane of the lens supporting table 245. The image pickup lens 210 is positioned by the reference planes 246A1, 246A2, 246B1, and 246B2 of the lens fixing arms 246A and 246B, and the rotation of the image pickup lens 210 is regulated by abutting one side plane of a three color separation prism 220 with the reference plane 246A3.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an image reading device used in, for example, a facsimile machine or a digital copying machine, which forms an optical image of a document obtained by an exposure optical system that scans the surface of the document while irradiating the document surface in an imaging unit.

[Background of the invention]

In an image reading device, an optical image of a document surface obtained by exposure scanning is generally formed on a solid-state imaging device such as an image sensor installed around an optical axis via an imaging lens system. For example, in an image reading device of a multicolor image forming apparatus, a light image of the document surface obtained by exposure scanning is passed through an imaging lens system, and a lens system is provided on the optical axis of the document light image and behind it. After the light is separated by a light splitting means such as a prism, an image is formed on an image sensor that receives the light in each channel. FIG. 11 shows the imaging lens 210, the light splitting means (three-color separation prism) 220, and three solid-state imaging devices 231B. 231G and 231R are configured as an integrated unit. FIG. FIG. 12 is a perspective view of the imaging unit. The light image of the document is led out parallel to the optical axis from the exposure light source and enters the imaging lens 210. The light is then split when passing through the three-color separation prism 220. The three-color separated optical images are sent to corresponding solid-state image sensors 231B,
The signals are input to 231G and 231H and converted into electrical signals. The solid-state image sensing devices 231B, 231G, and 231R are line image sensors configured with minute pixel elements with a pixel width of about 7 μm. Therefore, these solid-state imaging devices 231B, 231G, and 231R are precisely positioned with respect to the imaging lens 21O1 and the three-color separation prism 220 in order to accurately form the optical image of the original onto the solid-state imaging device. later formed into a single unit. When the image pickup unit is shifted from the optical axis of the original optical image, the original optical image is also input shifted. In FIG. 11, with respect to the regular optical axis L0 shown by the solid line, the shifted optical axis L1 shown by the broken line is on the imaging plane of the solid-state image sensors 231B, 231G, and 231R.
The amount of deviation ΔB, ΔG, and ΔR is generated. When the front and rear portions of the imaging unit are shifted vertically from the horizontal plane of the optical axis, the position where the light image is formed on the image sensor is shifted vertically. As a result, the leading edge starting position of the output image corresponding to the leading edge starting position of the original image is shifted back and forth in the image forming direction. If the left side and right side of the imaging unit with respect to the optical axis are shifted vertically from the optical axis horizontal plane, the portion of the original optical image on the optical axis horizontal plane will be imaged tilted left and right on the solid-state image sensor. The document is output in a diamond shape in which the left side and right side in the scanning direction are shifted back and forth. The imaging unit 200 is fixed to a lens support stand, which will be described later, and is further positioned and fixed to the main body of the image reading apparatus via a base plate, a base mounting plate, etc. On the lens support stand, an imaging lens 21 is mounted on the lens support base in order to align the imaging lens 210 with the optical axis of the optical system of the image reading device.
A positioning member is provided for positioning the cylindrical portion of the lens barrel. The reason why it is necessary to regulate the main scanning direction (horizontal direction) of the prism is that the solid-state image sensor is fixed to the prism with adhesive, so if the positional relationship between the prism and the lens deviates from the predetermined position, the main scanning direction of the element will be regulated. One example of this is that the image is no longer formed at the position.

[Problems to be solved by the invention]

Conventionally, the positioning member of the imaging lens and the position regulating member of the color separation prism were separate parts3. Therefore, in addition to the accuracy of each part, assembly was required to ensure that both members matched. By adding precision, the positioning accuracy of the entire imaging unit was maintained. For this reason, it takes a large amount of man-hours to maintain accuracy when assembling both parts, and image formation defects due to inaccurate image output signals due to assembly errors occur, as well as optical axis alignment correction operations to eliminate this problem. It took a lot of time. Furthermore, readjustment operations were required due to poor reproducibility when the imaging unit was attached and detached.

[Means to solve the problem]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems caused by the optical axis deviation of the imaging unit in the conventional image reading apparatus as described above, and to realize stabilization of image reading accuracy. In other words, an image capturing unit installed in an image reading device and having its optical axis adjusted can always maintain an accurate optical axis regardless of the installation conditions of the reading device and generate highly accurate image reading output. The purpose is to provide a reading device. An image reading device of the present invention that achieves the above object scans and exposes a document image using an exposure light source of a scanning optical system, forms an image with an imaging unit consisting of an imaging lens, a color separation prism, and a solid-state imaging device, and performs image reading that performs photoelectric conversion. In the device,
The present invention is characterized in that a positioning surface is provided at one end of the positioning member of the imaging lens, the positioning surface coming into contact with one side end of the color separation prism and positioning the image in the main scanning direction.

【Example】

Prior to a detailed description of the present invention, the general functions of the image reading device will first be described. Furthermore, Figures 11 and 12
The same members having the same functions as those in the figures will be described with the same reference numerals. FIG. 1 is a configuration diagram of an image reading device. In the same figure,
lOl is the original platen glass, and the original is placed on this original platen glass 1.
placed on 01. The document tray is illuminated by a halogen lamp 111 provided in an exposure light source unit 110 that moves on the slide rail 102. The movable mirror unit 120 is provided with a second mirror 121 and a third mirror 122, which move on the slide rail 102, and in combination with the first mirror 112 provided in the exposure light source unit 110, move the original on the original platen glass 101. The resulting optical image is guided to the imaging unit 200. Exposure light source unit 110 and movable mirror unit 120
are powered by V and 1/2 V, respectively, by a driving device (not shown) consisting of a stepping motor, pulley, wire, etc.
are driven in the same direction at a speed of A standard white plate 10 is provided on the back side of the front end of the original table glass 101.
3 is provided, and is configured so that a standard white signal can be obtained before the start of document reading scanning. The imaging unit 200 includes a lens 210 as an imaging lens system, and a three-color separation prism 220 as three-color separation means.
．． Solid-state image sensors 2318, 231G and 231R provided on three sets of substrates 232B, 232G and 232R, respectively.
configured. The original optical image transmitted by the first mirror 112, the second mirror 1211, and the third mirror 122 is focused by the imaging lens 210 of the imaging unit and enters the three-color separation prism 220. FIG. 9 shows a central sectional view of the imaging unit of the present invention. The color separation prism 220 shown in FIG. 9, FIG. 11, and FIG.
In front of the prism 22, another group of pre-color separation prisms 221 is provided and configured integrally. Inside the front group prism 221 is a dichroic mirror 2.
23 and a dichroic mirror 224 are provided in the rear group prism 222, respectively. The light passing through the imaging lens 210 passes through the front group prism 221
The light is incident almost perpendicularly onto the prism surface 221A. after that,
The incident light is separated by the dichroic mirror 223, and the blue component light (wavelength 400 to 500 nm) is reflected and directed toward the surface 221A. This blue component light is totally reflected at the boundary between the glass and the air layer on the surface 221A, is emitted from the surface 221B almost perpendicularly to this surface, and is imaged on the solid-state image sensor 231B. On the other hand, the light (wavelength: 400 to 700 nm) transmitted through the dichroic mirror 223 further travels straight through the rear group prism 222 from the front group prism 221 and reaches the dichroic mirror 224 . Here, the red component light is reflected and
Head to A. The red component light is the ha vapor deposition surface 222D of the surface 222A.
The light is totally reflected by the surface 222B, is emitted from the surface 222B almost perpendicularly to this surface, and is imaged on the solid-state image sensor 231R. The green component light having the wavelength that has passed through the dichroic mirror 224 reaches total reflection 222C, is totally reflected at the boundary between the air layer and the glass, is emitted from the surface 222B almost perpendicular to the same surface, and is imaged on the solid-state image sensor 231G. . The three-color separation prism 220 having the above configuration is formed by polishing and bonding four prisms having inter-plane angles as shown. Here, the cross section of the front group prism 221 is a large equilateral triangle with the surface 221A as one side, and the cross section of the rear group prism 222 is configured as a small triangle with the surface 222A as one side. Configure it like this. The optical path lengths within the glass are all equal, and the lengths are equal to the height 62 of the large equilateral triangle of the front group prism 221. By using the large and small prisms as described above, the three-color separated light images are formed into substantially the same plane. Surface 2 of the three-color separation prism 220 made in this way
21A is mounted at a predetermined position by a mounting member 225 so as to be perpendicular to the optical axis L0 of the imaging lens 210. Furthermore, the regular optical axis. The light flux incident on the imaging lens 21
0. A solid-state image sensor 231B, which is a line image sensor configured with minute pixel elements with a pixel width of approximately 7 μm, passes through a three-color separation prism 220. 231G, 231R, e.g. CCD (charge coupled device)
After highly accurate position adjustment, each solid-state imaging device is fixed to the three-color separation prism 220 with adhesive or the like so that the image is formed on the imaging plane of the three-color separation prism 220. The imaging lens 21O1 whose position has been adjusted in this way, the trichromatic separation prism 220, and the solid-state imaging devices 231B, 231G, 2
31R is configured as an integrally fixed imaging unit 200, and is installed at a predetermined position of the image reading device. FIG. 2 is an exploded perspective view of the imaging unit 200 of the present invention, FIG. 3 is a plan view showing the imaging unit placed on a lens support and positioned, and FIG. 4 is a sectional view taken along line A-A. , FIG. 5 is an exploded perspective view. The rear end surface 210R of the lens barrel of the imaging lens 210 and the front surface 221A of the three-color separation prism 220 are connected to the spacer 226.
After being positioned through the , they are bonded to each other and formed integrally. A light-shielding mask 227 is adhered to the reflection surface 222C of the three-color separation prism 220 above the rear group prism 222 using double-sided tape or the like. The light-shielding mask 227 is a hollow plate-like member with a thickness of about 2 m+m made of an elastic material such as black neoprene foam, and the upper and lower surfaces thereof are covered with double-sided adhesive tape of the same shape, such as Sony Pond Film T 4000. An equivalent product (manufactured by Sony Pond) is attached. A black light shielding plate 228 is provided on the upper surface of the light shielding mask 227.
is pasted to cover the hollow hole (square hole 227A) and shield it from light. The light-shielding mask 227 has a rectangular outer shape that almost covers the reflective surface 222C, and has a square hole 227 inside.
It has A. The square hole is formed to have a shape and size that is slightly larger than the effective area of the imaging light flux that is incident on the reflecting surface 222C and reflected there. That is, the imaging light beam enters the reflecting surface 222C and is totally reflected by the critical angle formed by the internal glass layer and the air layer of the external square hole 227A. Also, the adhesive surface 227B of the light-shielding mask 227. That is, the surface other than the square hole 227A is the reflective surface 222C.
Since it covers the surface other than the imaging light flux incident surface, it prevents external miscellaneous light from entering the prism surface, which is effective in preventing noise in the image signal. This is not only effective when using a normal image reading device, but especially when adjusting the position of the imaging unit by removing the outer cover or internal light-shielding cover of the reading device, external light will directly enter the image sensor and leave the body unprotected. Therefore, it has the advantage that adjustment work can be carried out effectively without using special light shielding means. The light shielding plate 2 is glued to the light shielding mask 227 and forms an integral part.
A portion of 28 is engaged with a mounting member 225, which will be described later, and its position is regulated. Note that the light shielding plate 228 and the light shielding mask 227 may be integrally molded. In addition, light shielding covers 229 and 229 are attached to both sides of the triangular triangular shape of the three-color separation prism 220 to block the incidence of miscellaneous light. The imaging unit 220 assembled in this manner is formed into an integrated unit by adjusting the positions of the solid-state imaging devices 231B, 231G, and 231R attached to the substrates 232B, 232G, and 232H, respectively, and bonding them to the three-color separation prism 220. . The imaging unit 200 assembled and adjusted as described above is then positioned and fixed on the lens support stand 245. An opening 245a is formed on the lens support 245, and a part of the lens barrel of the imaging lens 210 is sunk into the opening 245a. Lens fixing arms 246A and 246B are fixed to both sides of the upper surface of the lens support base 245 with screws. Further, the mounting member 225 is screwed to the back surface of the lens fixing arms 246A, 246B. The front part of the lens fixing arms 246A and 246B is L.
A letter-shaped protrusion is formed, and its inner surface 246A1゜2
46Bl constitutes the same extension surface, and constitutes a reference surface for positioning the front end surface 210F of the lens barrel of the imaging lens 210. Further, the L-shaped inner surfaces 246A2 and 246B2 of the lens fixing arms 246A and 246H are arranged in parallel and abut against the cylindrical outer peripheral surface of the lens barrel of the imaging lens 210, and are a reference for determining the vertical and horizontal positions of the imaging lens 210. It is a surface. Furthermore, the rear end of one lens fixing arm 246A is extended, and its inner surface is slightly stepped from the L-shaped inner surface 246A2, and a right surface 246A3 is partially formed. This surface 246A3 is a reference surface against which one side surface of the three-color separation prism 220 formed integrally with the imaging lens 210 comes into contact. That is, the imaging lens 210 is
6A1, 246A2, 246B1, 246B2, but still has a degree of freedom to rotate around the optical axis. However, when one side of the prism 220 comes into contact with the reference surface 246A3 of the lens fixing arm 246A, rotation is restricted, and the imaging unit 200 is set at a predetermined position. Since the reference surfaces 246A2 and 246A3 are flat surfaces integrally formed on the lens fixing arm 246, high precision can be maintained by machining the same parts. Thereby, the positioning of the imaging unit 200 can be performed easily and with high precision. FIG. 6 is a perspective view showing an assembly example of the imaging unit, FIG. 7 is a plan view thereof, FIG. 8 is a rear view of the imaging unit as seen from an example of a fixed imaging element, and FIG. 9 is a diagram of the imaging unit. The cross-sectional view, FIG. 1O, is a side view including a cross-sectional view of the adjustment support portion of the imaging unit. In these figures, 240 is a base mounting plate, 241 is a unit base plate, 242A, 242B, 242C are adjustment rings, 243A, 243B, 243G are fixing nuts, 244A, 244B. 244C is an adjustment screw; 245 is a lens support; 102.
102 is a slide rail, and 104 is a machine frame bottom plate. The base mounting plate 240 is a metal plate with a thickness of 2 mm, and the base mounting plate 240 is fixed to the slide rail 102 so that its position can be adjusted. That is, the distance between the imaging lens 210 and the document tray caused by the difference in focal length of the imaging lens 210 is adjusted within the range of the four elongated holes 240a near both wing ends of the base mounting plate 240, and Fixed with screws. Note that an oblong hole 240b located in the middle of the elongated hole 240a,
Eccentric cams 250 and 250 are inserted into the inner surface of 240b to enable fine adjustment. Three adjustment screws 244A, 244B, and 244G are arranged and planted on the upper surface of the mounting plate 240 that is parallel to the mounting surface of the slide rail 102. The implantation screws 244A, 244B, 244C
The installation position is two adjustment screws 244 arranged parallel to the optical axis of the photographic lens 210 and located far from the optical axis.
A, 244B, and one adjustment screw 24 arranged perpendicularly to the optical axis with respect to any one of the adjustment screws.
4C, and these three adjustment screws 244A, 244B
, 244C form an L-shape when viewed from above in a plan view (FIG. 3). The adjustment screws 244A, 244B, and 244C are commonly used commercially available bolts. These adjustment screws are screwed and fixed to female screws provided on the base mounting plate 240. These adjustment screws 244A, 244B, 244
After C is screwed onto the base mounting plate 240, a rotation prevention treatment is applied. Adjustment rings 242A, 242B, and 242C are screwed onto the adjustment screws 244A, 244B, and 244C, respectively. The adjustment rings 242A, 242B, and 242C are metal rings with a diameter of 24+ll+l+1 and a thickness of 2.5+m+m. The adjustment ring 242A. 2428.242C is threaded. The outer peripheries of these adjustment rings 242A, 242B, and 242C are knurled to improve operability. The three adjusting screws 244 on the unit base plate 241
Upper adjustment screws 244A, 244B, and 244C are loosely inserted into corresponding portions of A, 244B, and 244C, respectively, with adjustment holes having a diameter slightly larger than the adjustment screw diameter. The lower surface of the unit base plate 241 is in contact with the upper surface of each of the adjustment rings 242A, 242B, and 2424G, and the unit base 241 can be moved up and down by rotating any or all of the adjustment rings 242A, 242B, and 242C. Adjustable and tilt adjustable. Commercially available nuts are used for the fixing nuts 243A, 243B, and 243C. This fixing nut 243A, 2
43B and 243C are the adjustment screws 244, respectively.
A, 244B, and 244C are screwed together. Fixing nut 24
3A, 243B, and 243C are imaging units 2, which will be described later.
After completing the height adjustment process of 00, adjust screw 244A, 2
44B and 244C, and serve to fix the imaging unit 200. In addition, the above fixing nut 243A
, 243B. A washer is used between the lower surface of 243C and the unit base plate 241. The unit base plate 241 is a metal plate with a thickness of 21+11. An imaging unit 200 attached to a lens support stand 245 is fixedly mounted on the upper surface of the unit base plate 241 . The lens support stand 245 is movable and adjustable on the unit base plate 241 in the optical axis direction of the photographing lens 210, and is fixed with a screw after adjustment. 248A and 248B are lens positioning plates screwed to the unit base plate 241, 249A and 249B are lens positioning pins implanted in the base mounting plate 240, and 249A and 249B are lens positioning pins implanted in the base mounting plate 240 fixed to the slide rails 102 and 102. On the other hand, the base unit plate 241 is made movable in the optical axis direction and fixed with screws. The lens barrel of the imaging lens 210 is loosely fitted into the recess on the top surface of the lens support base 245, and after being positioned by lens fixing arm plates 246A and 246B arranged on the left and right sides of the lens barrel, a fixing band is attached to the lens barrel. 247! :: , J:
Re-fixed. The lens fixing arm plates 246A and 246B are fixedly attached to the attachment member 225 located behind them. The configuration of the present invention is as described above, and the adjustment procedure thereof will be explained below. 0 Slide rail 1
Adjust the position to 02°102 and fix with the screws. ■Three adjustment rings 242A on these three adjustment screws. 242B and 242C are screwed together. (2) Next, the adjustment screws 244A, 24B, and 244G are loosely fitted into the three adjustment holes of the unit base plate 241 to which the imaging unit 200 is already attached. The unit base plate 241 is first screwed into the adjustment ring 242A. It is placed on the upper surfaces of 242B and 242C. (2) At this stage, the height of the imaging unit 200 is roughly adjusted. Exposure light source unit 110 and movable mirror unit 12
0 moves on the slide rail 102. Therefore, the light beam of the original optical image derived by the scanning and exposure of the exposure light source unit 110 has an optical axis parallel to the slide rail 102. Rough adjustment of the height of the imaging unit 200 is performed using this slide rail 102 as a reference. A dial gauge is provided on a reference base horizontally suspended on the slide rail 102, and the unit base plate 2 is mounted from this reference base.
Adjust the distance to the top surface of 41 uniformly. Select a measurement point near the adjustment hole of the unit base plate 241, touch the measuring point of the dial gauge, and while looking at the scale, rotate the adjustment rings 242A, 242B, and 242C to move the unit base plate 241 up and down. Adjust. After completing this rough adjustment, the fixed neck l-243A, 243B
, 243C are screwed onto the adjustment screws 244A, 244B, and 244C, respectively, to temporarily fix the unit base plate 241. The final fine adjustment of the imaging unit 200 is performed by deriving an actual reference light image from the exposure light source. solid-state image sensor 231B,
The image output based on the reference light image outputted from 231G and 231R is input into a measuring instrument such as an oscilloscope, and the adjustment is performed so that the output image from the solid-state image sensor matches a predetermined reference position. 242A, 2
Finely adjust 42B and 242C respectively. This fine adjustment is performed by the imaging unit 20 from the optical axis horizontal plane.
The purpose is to eliminate the vertical deviation between the 0# section and the rear part, and the vertical deviation between the left side and right side parts of the imaging unit 200 from the optical axis horizontal plane. The vertical deviation between the front part and the rear part of the imaging unit 200 from the optical axis horizontal plane is adjusted by an adjustment ring 242A corresponding to the front part of the imaging unit 200 and adjustment rings 242B and 242C corresponding to the rear part of the imaging unit 200. The vertical deviation between the left side and the right side of the imaging unit 200 from the optical axis horizontal plane is mainly adjusted by the adjustment ring 242C. Note that the embodiment of the image reading device described above relates to a color image reading device that separates color image information of a color document or the like into three colors using a prism and outputs the resultant image, but the present invention is limited to this embodiment. Instead, it is of course applicable to an image reading device that separates two colors (cyan and red, etc.) or an image reading device that obtains a monochromatic image signal without using a prism.

【Effect of the invention】

According to the present invention, when adjusting the position of the imaging unit in an image reading device, the imaging lens and color separation prism can be accurately, easily, and quickly positioned, and the optical axis can always be accurately set even when assembling or attaching/detaching the imaging unit. It has the excellent effect of maintaining high accuracy, generating high-precision image reading output, and achieving sharp image formation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an image reading device according to the invention, FIG. 2 is an exploded perspective view of an imaging unit of the invention, and FIG. 3 is a plan view showing the imaging unit placed on a lens support. ,
Fig. 4 is a sectional view taken along line A-A, Fig. 5 is an exploded perspective view, and Fig. 6 is an exploded perspective view.
The figure is a perspective view showing the adjustment support part of the imaging unit, FIG. 7 is a plan view thereof, FIG. 8 is a rear view, FIG. 9 is a central sectional view, FIG. 1O is a side view, and FIG. A cross-sectional view showing the optical path, and FIG. 12 is a perspective view thereof. 102...Slide rail 200...Imaging unit 210...Imaging lens 220...Three color separation prism 225...Mounting members 231B, 231G, 231R...Solid-state image sensor 24
0...Base mounting plate 241...Unit base plate 2
45...Lens support stand

Claims (1)

[Claims] In an image reading device in which a document image is scanned and exposed by an exposure light source of an optical system, and the image is formed and photoelectrically converted by an imaging unit consisting of an imaging lens, a color separation prism, and a solid-state imaging device, one end of a positioning member of the imaging lens is provided. . An image reading device, further comprising a positioning surface that abuts one side end of the color separation prism and positions the image in the main scanning direction.