JPH0728017B2 - Image reader - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, for example, a document having a one-dimensional line sensor, and a document for image reading in a state of being in close contact with the one-dimensional line sensor. The present invention relates to an image reading apparatus suitable for being applied to a facsimile apparatus, an image reader, or the like that reads image information while moving the image relatively.

[Prior Art] Conventionally, as an image reading apparatus using a one-dimensional line sensor, a one-dimensional line sensor having a length of several cm is used to form a document image using a reduction optical system to read original image information. It has been known. However, this type of image reading device requires a large optical path length for performing reduction or imaging.
Moreover, since the volume of the optical system is large, it is difficult to make the reader small.

On the other hand, in the case of using an equal-magnification optical system using a long one-dimensional line sensor having the same length as the document width, the volume of the optical system can be remarkably reduced and the reader can be downsized. Known methods for realizing such a unity-magnification optical system include a method using a converging fiber and a method using a contact lens array. Further, a contact type document reading method of reading a document while moving the document in a close contact state on the one-dimensional line sensor without using such a fiber or lens array at all (Japanese Patent Laid-Open No. 55-74262, Japanese Patent Laid-Open No. 55-74262). 75271, JP-A-56-45084, JP-A-56-122172
No.) has already been developed as related to the applicant's prior application.

FIG. 8 is a side cross-sectional view showing the contact type image reading apparatus in a partially cutaway view. The apparatus will be briefly described. Reference numeral 8 is a sensor portion that is arranged on a transparent substrate 11 such as glass in a direction orthogonal to the drawing to form a one-dimensional line sensor.

In this sensor 8, on a transparent substrate 11 such as glass,
A light-shielding layer 12 of metal or the like and an insulating layer 13 are formed, and a semiconductor layer 14 such as GdS.Se or hydrogenated amorphous silicon (hereinafter referred to as a-Si: H) as a photoconductive layer is formed thereon. . Further, a pair of main electrodes 16 and 17 are formed via a doping semiconductor layer 15 for ohmic contact, and a light receiving window 18 is formed between them.

In this structure, the light L incident through the incident window 19 of the transparent substrate 11 (the sensor unit 8 shields the incident light from the incident light).
The original P is illuminated by (the light is shielded by 12), the reflected light is received by the sensor unit 8, and the read signal is taken out through the electrode wiring (not shown). That is, for example, the main electrode 16
When a high-potential drive voltage is applied to the main electrode 17 with reference to the potential of, the reflected light L is transmitted through the light receiving window 18 to the semiconductor layer.
When incident on the surface of 14, the resistance decreases because the number of carriers increases, and this change can be read as image information.

On the other hand, the distance between the document P and the sensor unit 8 is usually 0.1 mm.
Read resolution of 4 to 8 lines / mm can be obtained.
In order to secure such resolution, the above interval must be strictly controlled. The control of the gap is performed by forming a transparent protective layer 20 on the upper surface of the sensor unit 8 to cover it.

A plurality of such optical sensor portions 8 are arranged in a line in a direction orthogonal to the paper surface in FIG. 8 (width direction which is directly in the moving direction of the document P indicated by an arrow) to form a one-dimensional line sensor. The image information carried on the document P is read line by line in the width direction as the image information is moved.

FIGS. 9 (A) and 9 (B) are plan views showing two examples of the configuration of the image reading apparatus having such a conventional line sensor, and show the arrangement state of the entrance window and the optical sensor section.
As shown in these figures, the conventional incident window 19 has a rectangular shape (reference numeral 19 'in FIG. 9 (A)) with respect to each optical sensor section 8 or a linear shape (first section) parallel to the arrangement direction of the optical sensor sections 8. Figure 9 (B)
19 ").

[Problems to be Solved by the Invention] Generally, in the image reading apparatus, it is difficult to keep the distance between the original P and the optical sensor unit 8 constant by the conveying mechanism of the original P, as shown in FIG. As described above, the distance 1 may change due to the flapping of the paper.

If there is such a variation Δl in the distance l, the optical path length changes, so that in the conventional image reading apparatus, as shown in FIG.
The amount of light incident on the optical sensor unit 8 fluctuates (ΔP), and as a result, the output of the optical sensor unit 8 fluctuates, so that there is a problem that image information cannot be read accurately.

The variation in the amount of light with respect to the variation in the distance to the document surface will be described in more detail with reference to FIGS. 12 (A) to (C) and FIG.

As shown in FIGS. 12 (A) to 12 (C), consider a case where windows 19A, 19B and 19C of the same size are opened at a distance A, a distance B and a distance C from the optical sensor unit 8, respectively. . First, when the window 19A is located at the position shown in FIG. 12 (A), if the distance l to the document surface is gradually increased from 0, as shown in FIG. 13, light immediately enters the optical sensor unit 8. First, at this time, the light amount P changes by drawing a curve PA having a large peak. Conversely, if the window 19C is located at the position shown in FIG. 12 (C),
Even if the distance 1 is gradually increased from 0, the light does not easily enter the optical sensor unit 8, and at this time, the light amount changes in a curve PC having a small peak. At the intermediate position of FIG. 12 (B), the light amount P draws a curve PB intermediate between PA and PC.
That is, Becomes

When windows 19A, 19B and 19C are opened on the same substrate, they are equal to those in FIG. 9 (A) or (B), but at this time, the light quantity draws a curve of PA + PB + PC shown by a broken line in FIG. It is nothing but the curve shown in FIG.

In the conventional image reading apparatus, in addition to the problem caused by the fluttering of the document P, the light amount P, that is, the optical sensor output may change in addition to the above problem. That is, in the image reading apparatus, the protective layer 20 is provided in order to define the distance between the optical sensor section 8 and the original P.
If the thickness is not formed uniformly, the variation will also change the distance l. In such a case, not only the output of the image reading device in each position varies depending on the optical sensor, but also it is impossible to commercialize the image reading device uniformly, and thus the yield is reduced.

The present invention eliminates these conventional problems and ensures that a stable light quantity is incident on the optical sensor irrespective of the fluctuation of the distance l caused by the fluttering of the document during conveyance and the state of formation of the protective layer. An object of the present invention is to provide an image reading device capable of reading an accurate image.

[Means for Solving the Problems] For that purpose, the present invention comprises an optical sensor provided on a substrate provided with a window portion for transmitting light and juxtaposed with the window portion. Irradiate light from one surface side to the original surface arranged on the other surface side of the substrate through the window portion,
In the image reading device configured to receive the light reflected from the document surface by the optical sensor, the window includes a portion in which the amount of light transmitted through the window differs depending on the distance from the optical sensor. It is characterized by going out.

[Operation] That is, according to the present invention, it is possible to control the amount of light that passes through the window, that is, the amount of light that is emitted to the document surface or that is incident on the optical sensor, according to the distance from the optical sensor. Become. Therefore, a stable amount of incident light can be secured on the optical sensor regardless of the distance from the optical sensor to the document surface above it.

[Examples] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is an embodiment of an image reading apparatus to which the present invention is applied, and the same reference numerals are given to corresponding portions with respect to each unit that can be configured similarly to FIG. In the figure, reference numeral 190 is an entrance window according to this embodiment. FIG. 2 is a top view schematically showing the image reading apparatus shown in FIG. 1 for explaining one embodiment of the entrance window 190. In this example, the entrance window 190 is formed as having three portions 190A, 190B, 190C which increase in size as the distance from the photosensor 8 increases.

Here, FIG. 12 (A) to FIG.
Similarly to (C), each unit 190A to 190C is connected to the optical sensor unit 8 respectively.
Consider this example as being formed separately at a distance from A to C. The amount of light passing through the windows 190A to 190C is measured by the optical sensor 8
The size increases in this order because the size increases with the distance from.
Therefore, as the distance 1 between the optical sensor unit 8 and the document surface, that is, the optical path length increases, the document surface is irradiated with a large amount of light, and as a result, the amount of light incident on the optical sensor unit 8 is compensated. .

FIG. 4 shows change curves PA to PC of the received light amount p of the optical sensor unit 8 irradiated by the reflected light of the light passing through the windows 190A to 190C shown in FIGS. Is shown,
The light intensity peak values are almost equal to each other. If these windows 190A to 190C are formed on the same substrate as shown in FIG. 2, the light quantity at this time draws a curve of PA + PB + PC shown by a broken line in FIG.

As is apparent from this curve, the size of the entrance window is changed according to the distance from the optical sensor unit 8 so that the region S in which the change in the light amount is small is obtained regardless of the distance 1 between the optical sensor unit 8 and the document surface. It can be seen that the shape of the entrance window 190 can be selected. That is, as a result, it is possible to compensate for the influence of the change regardless of the distance 1 above the optical sensor unit 8 and to secure a wide area in which the change in the light amount is small.

FIG. 5 shows another embodiment of the entrance window 190 according to the present invention.
In the above example, the entrance window is divided into three parts 190A to 190C, but in this example, by dividing this into infinity,
It has one apex at the portion closest to the optical sensor unit 8,
The entrance window 190 has a triangular shape with a base at the farthest portion. By doing so, it becomes possible to obtain a flatter received light amount curve.

The image reading device shown in FIG. 1, FIG. 2 or FIG. 5 corresponds to 1 bit of image reading,
It is also possible to form a one-dimensional line sensor by arranging a plurality of these on the line 11 in a line shape. For example, 1728 photosensors and entrance windows can be arranged in the width direction of the document P.

Further, an optical sensor section, a charge storage section (capacitor section) for storing the output of the optical sensor section, a switch section for transferring the stored charge for signal processing, and a necessary wiring pattern, etc. They may be formed on the substrate by the same manufacturing process.

FIGS. 6A, 6B and 6C are plan views showing an example of an image reading apparatus in which such an optical sensor unit, a charge storage unit and a switch unit are integrally formed. The figure, the BB line sectional view, and the CC line sectional view are shown.

In these figures, 210 is a matrix wiring section, 208 is an optical sensor section, 212 is a charge storage section, 213 is a switch section including a transfer switch 213a and a discharge switch 213b for resetting the charge of the charge storage section 212, and 214 is a transfer. A wiring that connects the signal output of the power switch to a signal processing unit described later, and 223 is a load capacitor for accumulating and reading the charges transferred by the transfer switch 213a.

In this embodiment, an a-Si: H film is used as the photoconductive semiconductor layer 14 that forms the optical sensor unit 208, the transfer switch 213a, and the discharge switch 213b, and the insulating layer 203 is a silicon nitride film (SiNH) formed by glow discharge. ) Is used.

In FIG. 6 (A), in order to avoid complication, only upper and lower electrode wirings are shown, and the photoconductive semiconductor layer 14 is shown.
And the insulating layer 203 is not shown. Further, the photoconductive semiconductor layer 204 and the insulating layer 203 are composed of the photosensor unit 208 and the charge storage unit 2.
12, formed on the transfer switch 213a and the discharge switch 213b, and also formed between the upper electrode wiring and the substrate. Further, an n ⁺ -doped a-Si: H layer 205 is formed at the interface between the upper electrode wiring and the photoconductive semiconductor layer,
Ohmic junction is taken.

Further, in the wiring pattern of the line sensor of the present embodiment, all signal paths output from each sensor unit are wired so as not to intersect with other wiring, and crosstalk between signal components and gate electrode wiring This prevents the generation of induction noise.

In the optical sensor unit 208, 216 and 217 are upper layer electrode wirings. The light input from the incident window 219 and reflected by the document surface changes the conductivity of the photoconductive semiconductor layer 14 which is a-Si: H,
The current flowing between the upper electrode wirings 216 and 217 facing each other in a comb shape is changed. Reference numeral 202 is a metal light-shielding layer connected to an appropriate driving unit.

The charge accumulating portion 212 includes the lower layer electrode wiring 214 and the lower layer electrode wiring
The insulating layer 203 and the photoconductive semiconductor 14 are formed on the dielectric 214, and the wiring formed on the photoconductive semiconductor layer 204 and continuous with the upper electrode wiring 217 of the photosensor portion. The structure of the charge storage section 212 is the same as that of a so-called MIS capacitor (Metal-Insulater-Semiconductor). Both positive and negative bias conditions can be used, but stable capacitance and frequency characteristics can be obtained by using the lower electrode wiring 214 in a state of always being negatively biased.

In the figure, (C) is a transfer switch 213a and a discharge switch.
A switch portion 213 having a TFT structure including 213b is shown, and the transfer switch 213a includes a lower electrode wiring 224 that is a gate electrode, an insulating layer 203 that forms a gate insulating layer, and a photoconductive semiconductor layer 14,
The upper electrode wiring 225 serving as a source electrode, the upper electrode wiring 217 serving as a drain electrode, and the like. Discharge switch 2
The gate insulating layer and the photoconductive semiconductor layer of 13b are insulating layers 203
Also, in the same layer as the photoconductive semiconductor layer 14, the source electrode is the upper layer electrode wiring 217, the gate electrode is the lower layer electrode wiring 227, and the drain electrode is the upper layer electrode wiring 226. Reference numeral 234 is a lower layer wiring connected to the gate electrode of the transfer switch 213a.

As described above, the n ⁺ layer 205 of a-Si: H is present at the interfaces between the upper electrode wirings 217, 225 and 226 and the photoconductive semiconductor layer 14 to form ohmic contact.

As described above, the line sensor according to this example includes the optical sensor unit,
Since each of the constituent parts of the charge storage part, the transfer switch, the discharge switch, and the matrix wiring part has a laminated structure of a photoconductive semiconductor layer, an insulating layer, etc., each part can be formed simultaneously by the same process.

In addition, in the example shown in FIG.
Although the shape is shown in the figure, it may be a shape as shown in the fifth figure. In addition, in an image reading apparatus including such a line sensor, it is known that the output changes according to the position of the optical sensor unit 208 due to various factors, that is, the output is low at the end and high at the center. Therefore, the incident window 219 has an appropriate shape and size according to the installation position.
If is provided corresponding to the optical sensor 208, the sensor output can be compensated by the amount of light passing through the entrance window 219.

Furthermore, in reality, the image reading device has a light incident angle, a protective layer
Due to various factors such as the thickness of 20, the refractive index, the amount of fluttering of the paper, the amount of light of the illumination source 30, etc., a curve as shown by the broken line in FIG. 4 can be obtained even with a simple shape as shown in FIG. 2 or 5. It is possible that there is nothing. In such a case, FIG. 7 (A)
~ (G), considering these factors, the incident window
The shape, size, etc. of 190 can be selected appropriately. Among the shapes of the entrance window 190 shown in FIGS. 7 (A) to 7 (G), preferable shapes to which the present invention is applied are shown in FIGS. 7 (A), (B) and (D) to (G). It is a thing.

In addition, in the above description, the light quantity is adjusted by selecting the shape, size, etc. of the entrance windows 190, 219. However, even with the configuration shown in FIG. 9 (A) or (B),
For example, the light amount can be adjusted by subjecting the substrate 11 to an appropriate surface treatment in this portion.

EFFECTS OF THE INVENTION As described above, according to the present invention, a stable light amount can be obtained irrespective of the fluctuation of the distance between the optical sensor and the document surface caused by the fluttering of the document during conveyance and the formation of the protective layer. Since the light is incident on the optical sensor unit, accurate image reading can be performed, and the manufacturing yield of the image reading apparatus is improved.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of an image reading apparatus according to the present invention, FIG. 2 is a schematic plan view showing an embodiment of an entrance window of the image reading apparatus according to the present invention, and FIG. 4A to 4C and FIG. 4 are explanatory views for explaining the function and effect of the embodiment shown in FIG. 2, and FIG. 5 is a schematic plan view showing another embodiment of the entrance window according to the present invention. 6 (A), (B) and (C) each show an image reading apparatus to which the present invention is applicable, in which an entrance window, an optical sensor section, a charge storage section, a switch section and the like are integrally formed. A plan view showing an embodiment of the image reading apparatus, a step view thereof along BB line, and a sectional view taken along line CC, FIGS. 7 (A) to 7 (G) show other embodiments of the entrance window according to the present invention. FIG. 8 is a schematic plan view, FIG. 8 is a side sectional view showing an example of a conventional image reading apparatus, and FIGS. 9 (A) and 9 (B) show a conventional apparatus. Schematic plan view showing two examples of kicking entrance window, Fig. 10 to 13 is an explanatory diagram for explaining the amount of light caused by changes in the distance between the optical sensor and the document surface. 8,208 ... Optical sensor part, 11,201 ... Transparent substrate, 12 ... Light shielding layer, 1
3,203 ... Insulating layer, 14,204 ... Semiconductor layer, 16,17,216,217 ... Electrode (wiring), 19,190,219 ... Incident window, 20 ... Protective layer, 212 ...
Charge storage unit, 213 ... Switch unit, 213a ... Transfer switch unit, 213b ... Discharge switch unit, 246 ... Gate drive unit, A,
B, C ... Distance between optical sensor section and document surface, l ... Distance between optical sensor section and document surface, P, PA, PB, PC ... Amount of light.

Claims (4)

[Claims] 1. An optical sensor provided on a substrate provided with a window portion for transmitting light in parallel with the window portion,
A structure in which light is emitted from one surface side of the substrate to the other surface side of the substrate through the window portion and light reflected from the document surface is received by the optical sensor. In the image reading device, the window portion includes a portion in which the amount of light transmitted through the window portion increases as the distance from the optical sensor increases. 2. A substrate having a plurality of windows for transmitting light, a plurality of optical sensors provided on the substrate in juxtaposition with the windows, and one surface side of the substrate. A light source provided, and irradiates light from the light source to a document surface provided on the other surface side of the substrate through the plurality of window portions to reflect light reflected from the document surface. In the image reading device configured to be received by the optical sensor, each window portion includes a portion in which the amount of light transmitted through the window portion increases as the distance from the corresponding optical sensor increases. Reader. 3. The image reading device according to claim 2, wherein the amount of light is increased by increasing the width of the window portion according to the distance from the optical sensor. apparatus. 4. The image reading device according to claim 3, wherein the window portion has a triangular shape.