JPS63276962A - Contact type image sensor - Google Patents

Abstract

PURPOSE:To attain the miniaturization of an original reader by arranging a positioning member of an image forming means in the direction of optical axis at a right angle in an optical axis direction tying the read position of an original and a photodetection position of a photodetector. CONSTITUTION:A pressing guide 7 gives a carrying force to an original 2 by clipping the original 1 between a roller 2. A structure 8 is supported turnably from both sides by a drive shaft of the main body and a hole 9 for turning center. A mount plate 30 fixes the photodetector 14 and the detector 14 is driven by using a drive circuit board 31. The picture information at the side A of the original 1 collects the light of an LED array 10 and is radiated at a read position and a reflected light is made incident on the photodetection section of the detector 14 via a nonmagnification lens 13 and read as picture information. The lens 13 is fixed to the structure 18 at a right angle in the optical axis direction tying the read position 11 and the photodetection position of the detector 14. Thus, the total length of the detector in the lengthwise direction is decreased to make the size of the original reader small.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a contact type image sensor.

[Conventional technology]

A conventional image sensor of this type has been comprised of a light source for illuminating the document, a 1-magnification lens that forms an image of light reflected from the document on the sensor's light receiving surface, and a sensor that performs photoelectric conversion.

FIG. 8 shows the conceptual configuration of a conventional contact type image sensor (hereinafter referred to as C5). Here, 41 is a document, which is conveyed in the direction of the arrow in this figure. 42 is an LED (
It is a light emitting diode) array, and has an illumination length equivalent to the paper width of the original in a direction perpendicular to the paper surface of this figure. 43 is a lens array of equal magnification.

44 is an image sensor that reads image information and converts it photoelectrically.

FIG. 9 shows a cross section of a conventional contact type image sensor. Here, 51 is an original to be read, and 52a is an LED chip bonded onto an AJ2 substrate or a glass epoxy substrate 52b. 52c is a rod-shaped lens for condensing the amount of light. 52d is a lens house that holds the rod-shaped lens 52c, 53 is a lens array, and 54 is an image sensor. 55 is the entire structure of C5 (hereinafter,
(referred to as a frame), and usually has a high heat dissipation effect.
It is made of extruded material. 56 is a platen roller 58
57 is a leaf spring that biases the lens array 53 in the direction of arrow C%D in this figure, and the platen roller 58 is Rotate in the direction of arrow B in the figure.

FIG. 10 shows the appearance of the conventional example shown in FIG. Here, 5
9a and 59b are side plates on the side of C5, which are fixed to the frame 55 from both sides. Reference numeral 60a denotes an adjustment screw that presses the lens array 53 in the direction of the arrow E in the figure with the pressing force of the leaf spring 57 to finely adjust the position of the lens array 53 in the E direction. Although the adjustment screw 60a is shown only on the front side in this figure, a similar screw 60b is also provided on the side plate 59b side.

The operation of the conventional CS in the above configuration will be explained.

The light emitted from the LED chip 52a is focused by a rod-shaped lens, and the image information surface of the original 51 is illuminated at the reading position.

The light reflected from the illuminated original 51 is formed into a 1-magnification image by the lens array 53 on the light receiving section of the sensor 54, and is photoelectrically converted by the sensor 54 to read image information.

Next, C5 regarding the installation of parts that is generally done.
This will be explained in relation to the output performance.

In order to make the C5 output uniform and have a high MTF (spatial frequency characteristic), which indicates resolution, it is necessary to uniformly illuminate the reading position (reading line) and form a high MTF image of the B original image information. , and are necessary.

Usually, in order to satisfy the above-mentioned conditions, high precision components are used for each component, resulting in a C5 with high manufacturing costs.

Next, components with high accuracy will be explained below.

In FIG. 5, the LED 52 is screwed to the lower surface side, and in this case, the first board 52b is usually fitted with screws to ensure precision in mounting the parts.

Next, the light amount distribution of the illumination by the LED array 52 will be explained.

FIG. 11(A) shows the appearance of the LED array 52, and the first
FIG. 1(B) three-dimensionally shows the light amount distribution state on a plane that is away from the LED array 52 by a distance corresponding to the document surface and parallel to the LED ^L substrate 52b. Here, X is an axis in the longitudinal direction (reading line position) of the LED 52, Y is an axis perpendicular to the X axis and parallel to the All board 52b,
indicates the amount of light at each point on the XY plane.

As can be seen from FIG. 11(B), the amount of light is maximum at the position Y-0. Further, the LED chips 52a are usually arranged at several pitches in the X direction, and the amount of light usually has a wavy ripple.

Figures 12 (A) and (B) show the cross section of the above-mentioned (D LED7 ray 52 (7)) on a plane perpendicular to the X axis. We will discuss the mounting accuracy. First, Fig. 12(A) shows the state when the center of the rod-shaped lens 52c is shifted by Δ1 from the ideal position (designed position).At this time, the light converging position is shifted by Δ2. However, Δ2>Δ1. FIG. 12(B) shows that when the position of the LED chip 52a shifts by Δ3 from the ideal position, the light condensing position shifts by Δ4.

FIG. 13 shows how much the illuminance at the reading position changes when the condensing position is shifted by Δ2. 13th
In the figure, 91 is an illuminance distribution curve in a plane perpendicular to the X-axis as shown in FIG. 92 is Figure 12 (A)
This is an illuminance distribution curve when the condensing position is shifted by Δ2 as shown in FIG. By the way, the illuminance of a normal LED array is about 100ix. If the focusing position shifts as shown in Figure 12 (A), the illuminance at the reading position will be I2 / II
It deteriorates to 1001. The reason for this deterioration is that the amount of light from the LED is focused by a lens and the peak illuminance is increased, so the illuminance is usually near the optical axis of the illumination system, as shown in Figure 9.
This is because the price is rapidly increasing. Therefore, 1 in the Y direction
The normal limit is to obtain an output of 90 zeros of h with a width of n+m.

Therefore, in order to ensure uniformity of illuminance on the document surface, it is necessary to improve the accuracy of the following items.

■Position of rod-shaped lens 52c (see Figure 8 (A)) ■LE
Position of the D chip 52a (see FIG. 8(B)) ■-Distance l between the rod-shaped lens 52c and the LED chip 52a ■Distance between the LED chip 52a and the original 51 lit H2,
■ Mounting position of LED A1 board 52b (different from reading position)
Relative Position) Items (1) and (2) above have already been explained, but here we will discuss the case where the positional relationship is shifted at both ends of the LED and the middle tray is linearly stable.

Regarding item (2), since the LED chip 52a is usually bonded with a robot machine tool, the accuracy is about 50 μI, and A4 in FIG. 8(B) is also 0.1 to 0.2
It is about +am. Regarding the 0 term above, the first
Δl in Figure 2 (^) is generally about ±0.3 mm, but A2 ends up being ±1 to ±2-m. Regarding the above-mentioned 0 terms and 0 terms, the accuracy is at the limit of about ±0.2 nun, respectively, and becomes a factor of about ±1 nun as a variation in the amount of light. The above-mentioned item 0 is the first substrate 52 to the bottom surface of FIG.
The mounting accuracy of b is about ±0.2 mm, which is the limit.

For reasons of accuracy as described above, the illuminance on the reading position line on the document surface shows unilateral deviation, as shown by the two-dot chain line and the three-dot chain line in FIG. If the illuminance at the reading position is not uniform in this way, the output from the image sensor 54 will also be skewed, which has the disadvantage of causing stains on the read image and deteriorating the resolution of halftone originals. was. Until now, the following methods have generally been used to eliminate these drawbacks.

b Rotate the rod-shaped lens and adjust the fixed position of the lens.

Mouth Finely adjust and position the LED ^1 board.

c) Improve the precision of each part and perform sorting to achieve uniformity in each combination.

[Problem that the invention seeks to solve]

However, in both cases, the equipment becomes complicated and the number of man-hours increases.
The drawback was that the manufacturing cost was high.

In particular, the method of adjusting the position of the entire LED has to be carried out while observing the illuminance distribution on a two-dimensional plane, which requires an excessive number of man-hours.

Figures 14 to 17 show the SELFOC lens array (
Hereinafter, it will be referred to as SLA. ) is shown. FIG. 14 shows the structure of an SLA in which SELFOC lenses are arranged in two rows in a staggered manner.

FIG. 15 shows the imaging state of the SLA of FIG. 14. From this figure, it can be seen that an equal-strength standing image can be obtained by overlapping the images of the individual rod lenses.

FIG. 16 shows the illuminance distribution on the imaging plane when uniform diffused light is incident on the above-mentioned SLA. In this figure, each rod-shaped lens shows a mountain-shaped illuminance distribution with a peak at the central axis of the lens. Therefore, on the imaging plane, a plurality of mountain-like overlapping illuminance distributions are formed.

FIG. 17 is a three-dimensional representation of the development of the illuminance distribution of the SLA described above.

FIG. 18 shows the illuminance distribution on the line in the X direction when shifted by Δy from the optical axis on the imaging side of the SLA described above. As can be seen from this figure, ripples are generated by each rod lens. Also, if the line of uniform illuminance on the document surface and the SLA line or the line of the image sensor light receiving part and the SLA line are misaligned, the result will be the two-dot chain line and the three-dot chain line in Figure 20. As shown,
The illuminance on the sensor surface may become uneven.

Deterioration of resolution depending on the position of the SLA will be described below. FIGS. 19(^) to (C) show the deterioration of resolution depending on the position of the SLA. As can be seen from Figure 19 (B),
It can be seen that with respect to the total optical path length TC (distance 1lI from the document surface to the sensor), when the SLA position deviates from the center (%TC position), the MTF deteriorates significantly. As a way to solve the above problem, in Fig. 9, SLA is
It was common to increase the accuracy of the parts so that they are parallel to the reading line by having a structure that abuts against a surface and fixing them with precision to the image sensor 54 and frame 55. . However, this makes the parts more expensive, which in turn increases the manufacturing cost of the C5 as a whole.
It was not possible to provide an inexpensive C5.

Next, the MTF indicating the resolution according to the position of the SLA mentioned above.
This section describes the adjustment. As mentioned above, FIG. 19(A)
As shown in FIG. 19(C), it is the SLA position shown in FIG. 19(B) that affects the MTF the most.

To explain this using the cross section of FIG. 9, let TC be the distance between the reading position a of the original 51 and the imaging position of the image sensor 54, and the center point C of the height of the lens array 5LA53 is the center point of TC. Assuming that the amount of deviation from the angle is 6° C., Δ1 greatly affects the resolution, as can be seen from FIG. 19(B). Generally, the position is adjusted in the direction of arrow d in FIG.

A general method for adjusting the position will be explained using FIG. 9 and FIG. 1O. As mentioned above, 5LA53 is used as leaf spring 5
7 in the directions of arrows C1 and D, and screws 60a and 60b (not shown) in the direction opposite to arrow C (
In other words, the position of the SLA 53 is finely adjusted by pushing up the 5LA 53 in the E direction). However, as shown in FIG. 10, in order to adjust the screws 60a and 60b from the E direction, the screws must be positioned outside the longitudinal width of the sensor 54, and therefore This has disadvantages in that it requires extra space, becomes larger as a CS unit, and as a result, the entire reading device becomes larger, which becomes an obstacle to miniaturization.

Further, the drive circuit for the image sensor 54 is usually placed near the sensor 54. As described above, since the position of the adjustment screw is limited, the drive circuit also has to escape from the driver section for the adjustment screw, which has the drawback that the area of the circuit board cannot be increased.

It is an object of the present invention to eliminate the above-mentioned drawbacks and provide a compact and inexpensive contact type image sensor.

[Means for solving problems]

In order to achieve such an object, the present invention provides an illumination means for illuminating the image information surface of a document, an imaging means for forming an image at the same magnification of the light reflected from the image information surface by the illumination, and an imaging means for forming an image on the image formation surface of the reflected light. In a contact type image sensor for a document reading device, which has a light-receiving element that reads image information of reflected light by photoelectric conversion, and a structure that integrally holds illumination means, imaging means, and light-receiving element, It is characterized in that the positioning member in the optical axis direction is arranged at right angles to the optical axis direction connecting the document reading position and the light receiving position of the light receiving element.

[For production]

In the present invention, since the focus adjustment and fixation of the drive circuit board are performed from the side direction of the drive circuit board, which is perpendicular to the optical axis, extra space is created outside the longitudinal width of the image sensor. Since there is no need to secure the contact type image sensor and the length of the entire contact type image sensor in the longitudinal direction can be shortened, the entire unit can be made compact, and by extension, the entire device can be made compact.

In addition, in the present invention, since there is no adjustment using screws or the like from the drive circuit board side, the circuit board can be arranged efficiently, and the area (
Therefore, there is no need for an unnecessary increase in manufacturing costs due to the miniaturization of the circuit, and an inexpensive contact type image sensor unit can be provided as a whole.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention. In particular, in this example, an original m-reading apparatus will be described in which the original is conveyed in a U-turn from the bottom to the top and uses a same-size image sensor as a light receiving element.

In FIG. 1, l is a document (sheet) to be read, and image information to be read is located on the arrow A side of the figure. 2 is
This is a document conveying roller (drive roller) that conveys the document l in the direction of arrow B, and reads the image information of the document I while rotating in the direction of arrow C by a drive source (not shown). 3 is a structural frame of the apparatus; 3a and 3b are a pair of guides that guide the original 1 to the roller 2; 3a is an upper guide; 3b is a lower guide; 4 is an ejection guide that guides the document l out of the device;
5 is the upper cover of the device. Reference numeral 5a denotes a cover that also serves as a guide for the discharge section, and is rotatable in the direction of arrow C in the figure, so that it can be repaired in the event of a jam.

This is the bottom cover of the device. Reference numeral 7 denotes a pressing guide for the original 1, which applies a conveying force to the original 1 by holding the original 8% 1 between the roller 2 and the pressing means described later. 8
1 is a structure of a reading unit which is fixed to the main body, and includes illumination means, equal-magnification lens means, sensors, etc., which will be described later, are fixedly installed. This structure 8 is made of a material such as drawn aluminum, die-cast aluminum, or resin.

Reference numeral 9 denotes a rotation center hole fixed to the structure (hereinafter referred to as holder) 8, and the holder 8 is rotatably supported from both sides by the drive shaft of the main body and the rotation center hole 9. ing. 32
is a suppressing means such as a spring that presses the reading unit toward the roller 2 side. 11 is a document reading position, and 12 is a light receiving line on the light receiving element.

! Reference numeral 3 denotes a 1-magnification lens that guides reflected light from the document reading position 11 to the light receiving position 12. Reference numeral 14 denotes an image sensor (hereinafter referred to as a light receiving element) having a photoelectric light receiving section in the light receiving line 12.

20 is an actuator that rotates in conjunction with the insertion of the original 1; 2 is a detector that detects rotation of the actuator 20; and 30 is a mounting plate that fixes the light receiving element 14. 31 is a drive circuit board that drives the light receiving element 14;
It is connected to a system controller (not shown), drives the light receiving element 14 with an input signal from the system controller, processes the optical output signal of the light receiving element 14, and transmits the signal to the system controller. 34 is a connector that electrically connects the circuit of the light receiving element 14 and the drive board 31.

In the above configuration, the original 'g41 is moved from the direction of the arrow B to B by the rotation of the roller 2 in the direction of the arrow C.

conveyed in the direction. The image information for side A of manuscript L is L
A rod-shaped equal-magnification lens 17 into which the light emitted from the ED chip 15 is incident.
The reflected light is incident on the light receiving portion of the light receiving element 14 via the equal magnification lens 13, photoelectrically converted by the light receiving element 14, and read as image information.

FIG. 2 shows in more concrete detail the unit structure of the document reading section of the embodiment shown in FIG. It makes a U-turn and is ejected. Further, FIG. 3 shows in detail the mounting plate 30 and drive circuit board 31 shown in FIG. 2. Hereinafter, components of the embodiment shown in FIGS. 2 and 3 that are not explained in FIG. 1 will be explained.

2a is a pulley on one side of the roller 2, and 2b is a timing belt that transmits driving force from a drive system (not shown).

7a and 7b are set screws for fixing the pressing guide 7 to the holder 8, and 88 to 8C are screws for fixing the lens 13 to the holder 8 from a direction perpendicular to the optical axis of the same-magnification lens 13 for imaging (for example, Selfoc lens). This is a set screw for fixing to the

8d and 8e are holes made in the holder 8, through which the side surface of the lens 13 described above can be touched from above in FIG. Further, by using the holes 8d and 8e, it is possible to adjust the position of the lens 13 in the optical axis direction using a needle-like protrusion of a jig (not shown) or the like. 8f and 81 are shaft supporting holes provided on the side surface of the holder 8, and 8Il is a circular hole 8f which is elongated. 8g and 8h are taps provided at both ends of the holder 8, and are used to fix the light receiving element mounting plate 30 described in FIG. 1.

Reference numerals 9a and 9b are stepped screws that are passed through taps provided on the frame 3 from both sides of the device, and whose pin portions at the tips fit into the circular hole 81 and the elongated hole 8f of the holder 8 described above;
The holder 8 is rotatably supported in the direction of arrow M about the pins of the screws 9a and 9b as rotation centers.

10aNIOe is illumination means for illuminating the original.

Reference numeral 10e denotes a rod-shaped lens that illuminates the original at the reading position 11 by condensing the luminous flux of the small square light-emitting LED chip 10a bonded onto the substrate 10b. 10d
is a lens house, which is located at both ends of the LED array 10a, and fixes the rod-shaped lens lOe to the LED board 10b. 10c is an external resistor that limits and adjusts the current value of LED loa, and is soldered onto the LED board 10b.

Reference numerals 30a and 30b are holes through which the fasteners 33 for fixing the light-receiving element mounting plate 30 to the Honda 8 are passed, and they are formed larger than the screw diameter so that they can be fixed by freely adjusting the position relative to the mounting plate 30 and the holder 8. It is. 30c and 30d are cut-and-raised portions for positioning by abutting the glass end surface of the light receiving element 14; 30e, 30f, 30g, and 30h are embossments for abutting the end surface; 30i and 30
J is a fixing surface for fixing the drive circuit board (hereinafter referred to as I'CB) 31, and the fixing surfaces 30i and 30J are provided with taps. 30, 30j2.30m, 30
n is a hook part for preventing the PCB 31 from floating, 30
31a and 31b are screws for fixing the PCB 31 to the mounting plate 30.

FIGS. 4 and 5 show other configurations of the embodiment of the present invention. In Fig. 4, 81 is a trapezoidal piece for adjustment, and 5L
It is located on the slope F of the holder 55 at both ends of A31, and contacts SL^31 at the surface G. Also 82 (82a.

82b) has an adjustment screw, and by pushing the trapezoidal piece 81 in the direction of arrow H, the SL^31 can be pushed up in the direction of J.

In the above configuration, in order to focus the CS (contact type image sensor), screws 82a and 82b shown in FIG.
When screwed in, the trapezoidal pieces 81a and 81b (81b is not shown) rise along the slope in the direction of arrow 1. Then, the joint surface G with 5LA31 moves in the direction of arrow J, and 5LA31, which is pressed in the direction of arrow C or the direction indicated by the arrow by the plate screw 57, is held down by the reference surface E and the upper surface G of the piece, and the screw 82 is screwed in. It is fixed and held according to the amount.

FIGS. 6 and 7 show the configuration of still another embodiment of the present invention. Here, 201a and 201b are adjustment jig needles provided on the adjustment jig of the CS unit. These needles 201a and 201b are 5LA31 at point S in this figure.
It sticks into the side of the 5LA31, making it movable. 202a, 2G2b, and 202c are pressers and screws from the side of SL^31, and those with pointed or double point tips are used. Reference numerals 55a and 55b are holes made in the holder 55, and are escape holes for the needles 201a and 201b.

In the above configuration, in this embodiment, the jig needles 201a and 201b are pressed against SL^31 in the direction of arrow R, and the point S
Push it into SL^31 and press SL^31 against the reference surface E. Next, the rotation, vertical and horizontal arrows 0°P in Figure 7
, move the two needles 201a and 20a in the Q direction,
Set SL^31 to the most in-focus position, then SL^31
are fixed with screws 202a to 202C from a direction perpendicular to the optical axis.

Even if the needles 201a and 201b are removed after this fixation,
SL^31 is held with a screw.

(Effects of the Invention) As explained above, according to the present invention, the focus adjustment and fixation of the drive circuit board are performed from the side direction of the drive circuit board, which is the direction perpendicular to the optical axis. There is no need to secure extra space outside the longitudinal width of the image sensor, and the length of the entire contact type image sensor can be shortened.
The entire unit can be made compact, and as a result, the entire device can be made compact.

In addition, in the present invention, since there is no adjustment using screws or the like from the drive circuit board side, the circuit board can be arranged efficiently, and the area (
Therefore, it is possible to provide an inexpensive contact type image sensor unit as a whole, since there is no unnecessary increase in manufacturing costs due to circuit miniaturization.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a reading device incorporating an image sensor according to an embodiment of the present invention, Fig. 2 is an exploded perspective view showing the configuration of the reading unit of Fig. 1, and Fig. 3 is a main part of Fig. 2. FIG. 4 is a cross-sectional view showing the main structure of another embodiment of the present invention. FIG. 5 is an exploded perspective view showing the structure of the reading unit in FIG. 4. FIG. 7 is an exploded perspective view showing the structure of the reading unit of FIG. 6; FIG. 8 is a conceptual diagram showing the structure of the conventional reading unit; Fig. 9 is a cross-sectional view showing the configuration of a conventional reading unit, Fig. 1θ is an exploded perspective view showing the structure of the conventional reading unit, Fig. 11 is (^), and (B) is a perspective view of the LED array. and characteristic diagram, Figure 12 (^), (B) is a cross-sectional view of the LED array,
Figure 13 is a light intensity distribution diagram of the LED array, Figure 14 is a configuration diagram showing the configuration of the SELFOC lens array, Figure 15 is an explanatory diagram of the imaging state of the SELFOC lens array, and Figure 16 is the SELFOC lens array. 17(A) and 17(B) are perspective views and surface light amount phase diagrams of the SELFOC lens array. FIG. 18 is a characteristic diagram showing the light amount distribution of the SELFOC lens array. Figures 19 (^) to (J) are characteristic diagrams showing the resolution characteristics depending on the position of the SELFOC lens array, and Figure 20 is L.
FIG. 21 is a waveform diagram showing the sensor output due to uneven light intensity of the ED array. FIG. 21 is a waveform diagram showing the sensor output due to the ripple of the SELFOC lens array. l...Original, 2...Document transport roller, 3...Structure (claim), 7...Press guide, 8...Reading unit structure (holder), 10a N1
0e = illumination means, 11-... document reading position, 12... light receiving line, 13... equal magnification lens (imaging means), 14... image sensor (light receiving element), 15...
LED chip, 17... Rod-shaped lens, 20... Actuator, 21... Detector, 30-... Mounting plate, 31... Drive circuit board (5LA)% 32... Spring (pressing means) , 81... Trapezoid for adjustment, 82a... Adjustment screw, 201-... Adjustment jig needle, 202a to 202e... Presser screw. Fig. 1: Disassembly of main parts of the embodiment ♀゛11 Perspective view: A sectional view showing the structure of the main parts of the embodiment Fig. 4: Conceptual diagram of a conventional reading unit Figure 8: Cross-sectional view of conventional reading unit Figure 9: Perspective view and characteristics diagram of LED array Figure 11: Cross-sectional view of LED array Figure 12: Light intensity distribution diagram of LED array Figure 13: Structure of Selfoc lens array Figure 14 Explanatory diagram of the image formation state of the SELFOC lens array Fig. 15 Explanatory diagram of the surface light amount distribution of the SELFOC lens array 916
Figure 17 Perspective view and area light intensity distribution of SELFOC lens array Figure 17 Characteristic diagram of light intensity distribution of SELFOC lens array Figure 18 Characteristic diagram of resolution depending on the position of SELFOC lens array Figure 19: Between waveforms showing the sensor output due to uneven light intensity of the LED array; 20th e-shaped diagram showing the sensor output due to ripples of the SELFOC lens array; 215i3

Claims (1)

[Scope of Claims] Illumination means for illuminating the image information surface of a document; imaging means for forming an image of the reflected light on the image information surface by the illumination at the same magnification; a light receiving element that reads image information of the reflected light by photoelectric conversion; the illumination means; the imaging means;
and a structure for integrally holding the light-receiving element, in which a positioning member in the optical axis direction of the imaging means is arranged to align the reading position of the original and the light-receiving position of the light-receiving element. A close-contact image sensor characterized by being arranged perpendicular to the connected optical axis direction.