JPH0318354B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reading device such as a facsimile machine,
In particular, the present invention relates to a reading device that reads a document with a directional sensor array via an imaging system.

In recent years, thin film sensors such as amorphous silicon and CdSe have been widely used in compact and long document reading systems. A typical example of its application is a digital imaging device such as a facsimile. FIG. 1 shows an example of the structure of a conventionally known thin film sensor. In FIG. 1A, 1 is a photoreceptor made of amorphous silicon or the like, 2a and 2b are metal electrodes such as aluminum, and 3 is a substrate made of glass or the like. Figure 1B is an enlarged plan view of one bit when the thin film sensor is configured as a digital line sensor.
The structure shown in FIG. 1A is shown for cross section 4 in FIG. B. A voltage is applied to the electrodes 2a and 2b, and when light enters the shaded area of the amorphous silicon layer 1, a change in the output current occurs, making it possible to sense light. The reason why the light receiving surface is meandering in FIG. 1B is to obtain a large output current. As shown in FIG. 1A, in the conventional sensor structure, the sensitivity does not change much no matter which direction light enters. This is true even if the electrode is a transparent electrode. From now on, for convenience, Figure 1A
A type having this structure is hereinafter referred to as a gap type.

An example of a reading system such as a facsimile using the photo sensor shown in FIGS. 1A and B is shown in FIGS.
Shown in B. In Figure 2, 5 is the manuscript, 6a, 6
b, 6c, 6d, 6e are 2 on the original surface to be read.
The imaging systems 7a, 7b,
Line sensors 8a, 7c, 7d, 7e
They correspond to 8b, 8c, 8d, and 8e and are read separately. By making the imaging system a double-lens configuration as shown in FIG. 2A, the distance from the document surface to the sensor is shortened and a compact reading system is realized. Note that the arrow indicates the direction in which the original 5 moves.

In FIG. 2A, FIG. 2B shows a cross section of a row of the thousand-island arrangement of each component. The imaging systems 7a, 7c, and 7d in FIG. 2B are shown as an example of inverted equal-magnification imaging, but in general, the imaging may be reduced imaging. As shown in FIG. 2B, if the imaging system is a compound-eye inverted imaging system, stray light enters through the pupil of the adjacent imaging system from other than the original surface to be read, resulting in so-called noise. For this reason, 9a, 9
c, 9e, 9g and 10a, 10c, 10e,
It becomes necessary to provide a light shielding plate as shown in 10g. For example, the light ray 11a shown by the dotted line in FIG.
Without the above-mentioned light shielding plate, light such as the light rays 11b and 11b would enter the sensor 8a, which is undesirable. Therefore, when applying a sensor with normal sensitivity and no directionality to such a reading system, the light shielding plates 9a, 9c, 9
e, 9g and 10a, 10c, 10e, 10g
Is required. In addition, the light shielding plates 10a to 10g also serve to prevent internal scattering, etc., occurring between the sensor substrate 12, the imaging system support, and the imaging systems 7a, 7c, and 7e.

As described above, when using a conventionally used sensor such as a solid sensor such as a CCD or a thin film sensor such as amorphous silicon, the problem of light shielding occurs when the reading system is configured with a reciprocating system. Although FIG. 1 shows a two-row chilled-like reading array, it goes without saying that a light-shielding plate is also required for a single-row reading system.

An object of the present invention is to provide a reading device having a sensor whose sensitivity is directional, particularly a sensor array represented by amorphous silicon, etc., and by using such a sensor, the above-mentioned compound eye It eliminates the need for a light-shielding plate required for an inverted imaging system, and also suppresses stray light generated by internal scattering even in the case of an upright 1-magnification imaging system such as a self-reflection system. This is to measure the improvement of the N ratio. Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 3 is a diagram showing an embodiment of the sensor according to the present invention, in which the sensor has directivity such that the maximum amount of light received is the light incident perpendicularly to the sensor. 16 in the figure is Cr
17 is a film such as glass, 18a and 18b are metal electrodes such as aluminum, 19 is an amorphous silicon layer, and the shaded area 19
I feel the light at a. That is, the region 19a forms a photosensitive region. 20 is a substrate made of glass or the like. A thin film sensor having the structure shown in FIG. 3A can be realized by, for example, providing a SiO _{2 film on FIG. 1A by glass evaporation or ion plating, and then applying a pattern such as a Cr film on top of the SiO 2} film. . Figure 3A
If the incident angles of the incident light 15a and the incident light 15b are Q ₁ and Q ₂ respectively, the incident light 15a enters the light receiving section, but the incident light 1
5b is not detected by the sensor because it is removed from the light receiving part. Here, when the incident angle is θ, some examples of the relationship between the incident angle θ and the amount of received light are shown in Figure 3B.
Shown below. In FIG. 3A, the gap (width of the opening) of the light shielding film 16 (light shielding means) is l ₂ and the gap (width of the photosensitive area) between the metal electrodes 18A and 18B.
l ₁ and the thickness of the film 17 is d.

In the example shown in FIG. 3B, Example 1 has l ₁ =3 μm, d
= 6 μm, the incident medium is air, and the refractive index of the film 17 is 1.5. Example 2 is l ₁ = 3μm, l ₂ = 6μ
When m and d are 6 μm, the incident medium is air, and the refractive index of the film 17 is 1.5. Example 3 is l ₁ = 3μm,
When l ₂ = 3 μm, d = 6 μm, and the incident side medium has the same refractive index as the film 17. Example 4 has l ₁ = 3 μm, l ₂ = 6 μm, d
= 6 μm and the incident side medium has the same refractive index as the film 17. As can be easily seen from these four examples, the correlation between the incident angle and the amount of light received can be varied in various ways by appropriately adjusting l ₁ , l ₂ and d and by combining them with the medium on the incident side. , it is possible to create a sensor that only receives light with a small angle of incidence and is not sensitive to light with a large angle of incidence.

Figure 4 shows, as shown in Figure 3A, the light incident at an angle θmin with respect to the light incident perpendicularly to the sensor in a sensor that receives the light incident perpendicularly to the sensor with maximum efficiency. The amount of light received begins to drop, and the sensor exhibits characteristics such that it no longer senses anything with respect to the incident light at θmax. The values of θmin and θmax in this case can be determined by the parameters configuring the sensor, l ₁ , l ₂ , d, and the refractive index n of the film 17, such as glass. If the refractive index of the medium on the light incident side shown in FIG. 3A is N, then It is. Similarly, θmax is It is. Here, an example of a specific design using these equations (1) and (2) is shown below.

For example, when the F _NO of the imaging system is 4.0, the numerical aperture is
It is 0.125. Therefore, the light receiving angle of the sensor at this time is θ=7.2°, and in this case, θmin=7.2°. The external medium is air and N=1. Also,
Let's consider a case where the sensor is designed so that, for example, θmax = 23.6°, the sensor does not sense the light that enters the sensor through an adjacent lens. By the way, the distance between the electrodes
l The value of ₁ is actually limited in size by the following constraints: ○B If the distance between the electrodes is small, the pattern of the light receiving part can be made finer to increase the S/N ratio of the sensor. It is possible. Conversely, the larger the distance between the electrodes, the smaller the S/N ratio of the sensor.

○B As the distance between electrodes becomes smaller, highly accurate patterning technology is required during production, and the limits of miniaturization are determined by patterning technology.

Considering these circumstances,
The value of the inter-electrode distance l ₁ is preferably in the range of 2 μl ₁ 20 μ. Further, the thickness d of the dielectric film is usually considered to be several μd+several μ, considering that it is usually manufactured by glass vapor deposition or the like. Considering these things, (1),
In the equation (2), N=1, n=1.5, l ₁ =2μm, θmin=7.2°,
θmax=23.578° From this, l ₂ =3.755 μm and d=10.49 μm.
That is, l ₁ = 2 μm, l ₂ = 3.755 μm, d = 10.49 μm,
When n=1.5, a sensor with directivity of θmin=7.2° and θmax=23.6° is obtained.

Unlike the case where the amount of light received is maximized by focusing on the light incident perpendicularly to the sensor as shown in Figure 3A and B, the sensor shown in Figure 5A and B is designed to maximize the amount of light that is incident on the sensor obliquely. This is to show an example in which the amount of light received is maximized at the center. The numbers given in FIG. 5A that are the same as the numbers given in FIG. 3A indicate the same members, so a description thereof will be omitted here. In addition, l ₃ is the center of the opening of the light shielding film 16 and the electrode 18
a and 18b, that is, the amount of displacement from the center of the photosensitive area. FIG. 5B shows that the values of each parameter of the sensor in FIG. 5A are l ₁ = 6 μm, l ₂ = 6 μm,
FIG. 7 is a diagram showing the relationship between the amount of received light and the incident angle θ of light when l ₃ =2 μm, d=10 μm, n=1.5, and N=1.

Next, as shown in FIG. 5, a general structure of a sensor will be described in which the light receiving rate is maximized for light obliquely incident on the sensor.
Figure 6 shows a general light-receiving sensitivity characteristic curve when receiving light centered on obliquely incident light at a certain angle θc. Shown in Figures A and B. The sensors shown in FIGS. 7A and 7B have the same shape as the sensor shown in FIG. 5A, and in FIG.
It shows the ray of θmin2. In the structure shown in FIG. 7, if the refractive index of the medium on the incident side of the light beam is N, and the refractive index of the glass film 17 is n, θmax1, θmax2,
θmin1 and θmin2 are determined as follows.

Here, θmax2 is expressed in correspondence with a minus sign. where d = 10.5μm, l ₁ = 20μm, l ₂
= 3.8 μm, l ₃ = 1.0 μm, n = 1.5, and N = 1.0, a sensor having the following directivity is obtained: θmax1 = 31.5° θmax2 = -15.5° θmin1 = 15.5° θmin2 = 0.8°.

Such asymmetric light receiving characteristics are caused by the metal electrode 18
By changing the pattern of the light shielding film 16 for a and 18b, it can be freely controlled.

As described above, it is necessary to provide light-receiving sensitivity characteristics for vertically incident light or incident light at a certain angle. For example, as shown in FIG. 2, the inclinations of the seed rays of the light incident on the central bit and the light incident on the peripheral bits are different for the light incident on the sensor array via the imaging system. Therefore, it is possible to achieve the maximum light receiving sensitivity for the bit vertically incident light in the center, and
It is desirable that the peripheral bits have maximum light-receiving sensitivity to obliquely incident light. This kind of setting is
Since the electrodes and light-shielding film can be formed using photolithography, it is only necessary to take the relative positions into account when creating the original mask.
Thin film sensors suitable for mass production can be manufactured relatively easily.

In this way, by forming the opening of the light-shielding film according to the incident angle of the principal ray of the light incident on each bit and individually controlling the directivity of the incident light on each bit, the sensor array can be It is possible to uniformly improve the S/N ratio of reading for each bit, and to provide a reading device that can accurately read a document.

In the sensor, when the film layer 17 is formed by glass vapor deposition, if the film thickness d is too large, the surface of the film 17 becomes minutely uneven, which is undesirable and causes light scattering. If the thickness is about 10 μm or less, a film with a good surface can be obtained.

FIG. 8 is a diagram showing an embodiment of the gap type sensor according to the present invention described above in which light is incident from the substrate side. In the numbering indicating the structure of FIG. 8, the same number as the numbering of FIG. 3A represents the same member, but the structure of FIG. 8 is somewhat different from the structure shown in FIG. 3A. That is, as shown in FIG. 8, the structure of the sensor is that the sensor is
A pattern of a metal film 16 such as Cr is deposited as a light shielding film, a glass deposited film 17 is provided on top of the pattern, and a photoreceptor 19 made of amorphous silicon and an electrode 18 are further provided on top of this. .
The light beam 15a then reaches the light sensing portion 19a of the photoreceptor 19, but the light beam 15b does not reach 19a and is not detected.

The gap type sensor mentioned above has directivity within the plane included in the paper, and when used as a line sensor as shown in Figure 2, it is sufficient to have directivity in only one direction. In this case, it is sufficient to make the surface with directivity parallel to the line direction of the line sensor. However, such a gap type thin film sensor can be provided with directivity not only in one dimension but also in two dimensions, examples of which are shown in FIGS. 9, 10 and 11.

In FIG. 9, 16 is a light-shielding film, and the shaded area is the part that blocks light. 17 is a transparent film provided by glass vapor deposition or ion plating, 18 is a metal electrode, and 20 is a substrate made of glass or the like. In Figure 9, the incident light is extracted as a current signal by applying a potential difference between the metal electrodes 18, and the smaller the distance between the metal electrodes, the greater the current value for a given amount of incident light. Therefore, as seen in the pattern of the metal electrode 18 in FIG. 9, the portion 19b where the electrodes are close to each other is
The photoreceptor layer 1 is made of substantially amorphous silicon or the like and exhibits relatively stronger sensitivity than the distant portion 19e.
The shape of the photosensitive portion 9 is rectangular, and by combining it with the rectangular opening of the photosensitive film 16, it is possible to provide overall directivity in two directions, the x and y directions. FIG. 10 shows a structure in which the silicon photoreceptor 19 is formed into a fine rectangular pattern and the pattern of the metal electrode 18 is simplified. As shown in FIG. 10, each bit constituting the photoreceptor 19 is formed independently in a rectangular shape, and the light shielding film 1
Combined with pattern 6, it gives the sensor directivity. Note that in the sensors shown in FIGS. 9 and 10, the metal electrode may be a transparent electrode.

Figures 11A and 11B are diagrams showing an example embodiment of a two-dimensionally directional sensor;
is a perspective view, and FIG. 11B is a sectional view thereof. 1st
No. 9 with the number attached to the sensor shown in Figure 1 A and B.
The same numbers in the figures and FIG. 10 indicate the same members. In FIG. 11B, the light shielding film 1
The inner diameter and outer diameter of electrode 6 are d ₁ , d ₁ ′ and electrode 1
If the inner diameter and outer diameter of 8 are d ₂ and d ₂ ′,
For example, if d ₂ ′ > d ₁ ′ and d ₂ > d ₁ , the light from a point at a finite distance from the sensor and on the normal line to the center of the concentric electrode and mask is best sensed. It will have characteristics. Note that the electrode 18 may be either a metal electrode or a transparent electrode. Further, the shapes of the electrodes and the light-shielding film are not limited to concentric circles, but may also be, for example, elliptical shapes. Furthermore, the centers of the electrode and light-shielding film patterns are all on the same straight line (normal line) perpendicular to the silicon photoreceptor film 19, but generally the centers of the electrode and light-shielding film patterns are aligned on the same straight line (normal line). does not have to be perpendicular to the silicon photoreceptor 19; in such a case, a directivity that acts like off-axis imaging in lens imaging occurs.

Although the above embodiment has considered a gap type sensor, FIG. 12 shows another type of sensor to which the present invention is applied (hereinafter this sensor will be referred to as a sandwich type sensor).

In FIG. 12, 25 is a metal electrode, 26 is a photoreceptor such as amorphous silicon, 27 is a transparent electrode, 28 is a glass vapor deposited film, 29 is a light shielding film such as Cr, etc.
30 is a glass substrate. In the configuration shown in FIG. 12, the portion of the photoreceptor 26 that senses light is the portion where voltage is applied between the metal electrode 25 and the transparent electrode 27;
That is, the shaded portion 26a of the photoreceptor 26
Only. Therefore, the incident light 24a is detected by the photoreceptor, but the incident light 24b is not detected. In this way, in the sandwich type sensor, by selecting the mutual pattern of the metal electrode 25 and the light-shielding film 29, it is possible to create a sensor whose sensitivity differs greatly depending on the direction of light incidence, similar to the gap type shown above. It can be realized. Note that the photoreceptor 26 is not limited to silicon, but may be made of CaSe or the like, and the glass vapor deposited film may be other transparent film such as Zns.

FIGS. 13A and 13B show an embodiment of a Sanderch type sensor having directivity in one dimension.

In FIG. 13A, 31 is a metal electrode, 32 is an amorphous silicon photoreceptor film, 33 is a transparent electrode film, 34 is a relatively thick transparent film such as a glass vapor deposited film, and 35 is a light shielding film such as Cr. , 36 are glass substrates. The metal electrode 31 is shown in a pattern of multiple long and narrow rows. FIG. 13B shows a plan view of the light shielding plate 35, in which the directionality in the x-y direction corresponds to the metal electrode 31, and in this case, the sensor has directionality in the y direction, There is no directivity in the x direction.
Note that in FIG. 13B, the shaded area is the area that blocks light.

FIGS. 14A, B, and C show an embodiment of a sandwich type sensor having directivity in two-dimensional directions. The members constituting FIG. 14A are the same as those shown in FIG. 13A, including 31 a metal electrode, 32 an amorphous silicon photoreceptor film, and 33
34 is a transparent electrode film, 34 is a glass vapor deposited film, 35 is Cr
36 is a glass substrate. The plan view of the entire 1 bit of the Cr light shielding film 35 is shown in the first diagram.
This is shown in FIG. 4B and FIG. 14C. FIG. 14B shows an example in which the pattern through which light passes is rectangular, and FIG. 14C shows an example in which the pattern through which light passes is circular. When each center of the two-dimensional array of photosensitive parts of the sensor matches the center of each pattern of the light transmission area of the light shielding plate, x
Directional characteristics are symmetrical in both the x and y directions, and directivity can be provided in both the x and y directions. Furthermore, if the centers of the two-dimensional array of photosensitive parts of the sensor are shifted from the centers of the patterns of the light transmission area of the light shielding plate, the directivity becomes asymmetrical in the x and y directions. Therefore,
It is possible to provide directional characteristics depending on the angle of incidence of the incident light.

In the above-described embodiment of the sandwich type sensor, the electrode provided on one side of the photoreceptor is a metal electrode, but it may also be a transparent electrode.

In the gap type and sandwich type sensors shown above, only one layer of glass vapor deposited film was shown, but generally a dielectric layer is provided on the glass vapor deposited film. A glass vapor-deposited film and a light-shielding film layer may be further stacked on top of each other, such as a light-shielding film and a glass vapor-deposited film.

Next, an embodiment of a reading device to which the sensor of the present invention is applied is shown in FIGS. 15 to 18. The reading device shown in FIGS. 15 and 16 is an embodiment for reading a document in a thousand-island pattern, and FIG. 15 is an inverted image.
FIG. 16 shows the case of reading with an erect image.
In Figures 15 and 16, 41 is the original, 4
2a to 42e are calligraphy and drawings to be read on the manuscript surface, 4
3a to 43e are sensor arrays according to the present invention, and 44a to 44e are images of the original document images. In the apparatus shown in FIG. 15, the imaging system is 45a-4.
In the apparatus shown in FIG. 16, the imaging system consists of one group as shown by 5e, 46a to 46e, 47a to 47e, and 48.
It has a three-group configuration as shown by a to 48e, and 47a to 48e.
47e has a function as a field lens. By using the sensor according to the present invention, the light receiving angle handled by one lens system can cover 2θ, and the light beam incident from an oblique angle is 49.
I don't feel any light against it. Using such a sensor eliminates the need for a conventional light shield.

The reading device shown in FIG. 17 and FIG. 18 is different from reading a thousand islands arrangement, and shows a device for reading a normal example. The device shown in FIG. 17 is similar to the device shown in FIG.
A case is shown in which the document surface is read as an erect image as shown in the apparatus shown in the figure. Since the same numbers given to the devices in FIGS. 17 and 18 as in FIGS. 15 and 16 indicate the same members, their explanations will be omitted here. In the apparatus shown in FIGS. 17 and 18, sensor 50 is a long sensor. Even in these cases, if the light receiving angle of the sensor covers 2θ and the sensor is made insensitive to obliquely incident light 49 as described above, a reading system can be constructed without a light shield.

Figures 15, 16, 17, and 18 above
The example shown in the figure shows a case where the imaging system is a normal lens (a means for producing an imaging effect by giving a curvature to a medium with a constant refractive index), but in reality, it is limited to a normal lens. It can be applied to any type of lens that has an imaging effect, such as a phase lens such as a zone plate, a non-uniform lens such as a self-occurrence lens, and even a distributed index flat plate microlens eye (1986 Institute of Electronics and Communication Engineers). Comprehensive National Convention, 992, Kenichi Iga and 5 others). Among these, zone plates and distributed index flat microlens eyes are suitable for monolithic configurations because compound eye system patterns are manufactured using photolithography techniques, and the thin film sensor of the present invention is suitable for monolithic configurations. Combined with the fact that it has the advantage of being able to do so, it is convenient for realizing a compact reading device that can be mass-produced. Further, in general, it goes without saying that the present invention can be applied not only to one-dimensional reading devices such as facsimile machines currently in use, but also to two-dimensional reading devices.

As shown above, in the thin film sensor typified by amorphous silicon according to the present invention, by giving directionality to the direction of exposure, the desired sensitivity characteristics can be achieved in the bits around the center bit of the line sensor. It also eliminates the need for a light-shielding plate required for compound-eye imaging systems in digital imaging devices such as facsimile machines, and also allows the inner surface to be This provides a reading device that suppresses stray light caused by scattering and has a good S/N ratio.

[Brief explanation of the drawing]

Figures 1A and B are diagrams for explaining a conventional gap type sensor, Figures 2A and B are diagrams showing an example of a conventional compound eye reading device, and Figures 3A and B and Figure 4 are diagrams for explaining a conventional gap type sensor. 5A and B, FIG. 6, and FIG. 7 A and B each illustrate an embodiment of a gap type sensor to which the present invention is applied. FIG. 8 is a diagram for explaining another type of gap sensor to which the present invention is applied, and FIGS. FIG. 12 is a diagram illustrating a sandwich type sensor to which the present invention is applied;
FIGS. 13A and 13B are diagrams each showing an embodiment of a Sand German arch type sensor having directivity in a one-dimensional direction to which the present invention is applied. FIGS. 14A, B, and C are diagrams showing an embodiment of a Sand Germany type sensor having directivity in two-dimensional directions to which the present invention is applied, FIG. 15, FIG. 16, FIG. 17, and FIG. 18
Each figure shows a compound eye optical system using a sensor according to the present invention. 15a, 15b...Incoming light flux, 16...Light shielding film, 17...Glass vapor deposited film, 18a, 18b...
Electrode, 19...photoreceptor, 20...substrate.

Claims (1)

[Claims] 1. An imaging system, a sensor array for reading a document through the imaging system, and a light shielding means having a predetermined opening provided to restrict light incident on the photosensitive area of each unit bit constituting the sensor array. By forming the aperture of the light shielding means according to the incident angle of the principal ray of light incident on each unit bit via the imaging system, the directivity of each unit bit with respect to the incident light can be adjusted. A reading device characterized in that the following are individually controlled.