JPH0221713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a document reading device that uses a plurality of imaging systems to share and read document image information that should be read as a line of information, and is generally used as a reading system for facsimile machines. This invention relates to a general-purpose reading device.

2. Description of the Related Art Conventionally, document reading devices such as facsimile machines have been of the type shown in FIGS. 1 and 2. In FIG. 1, 1 is a document, 2 is a fluorescent lamp for illuminating the document, 3 is a lens, and 4 is a solid-state sensor such as a CCD. A document 1 is illuminated with a fluorescent lamp 2, an image is created on a solid-state sensor 4 using a lens 3, one line is read, and the information on the entire surface of the document is sequentially read by conveying the document in the direction of the arrow. It is something. However, in such a device, since there is an upper limit to the angle of view of the lens 3, it is necessary to maintain a large distance between the document 1 and the sensor 4, and as a result, the optical path must be turned back using a mirror or the like. However, the disadvantage was that the device became larger. In addition, the amount of light from the periphery of the document decreases with respect to the center of the document, making it impossible to obtain uniform output and requiring various correction measures. An example of a configuration considered as a method for solving these problems is shown in FIG. 2. In other words, as shown in FIG. 2, the imaging optical system is composed of a compound eye optical system in which a plurality of lenses are arranged in parallel, and a plurality of solid-state image pickup devices corresponding to each lens are arranged. In this method, one direction is divided into a plurality of regions, and each lens and each solid-state image sensor are assigned to read each region. FIG. 2 will be explained in more detail. In Figure 2, 5 is the original, 6
₁ , 6 ₂ , and 6 ₃ are part of image information such as calligraphy and drawings drawn on the manuscript. 7 ₁ , 7 ₂ , 7 ₃ are lenses, 8 ₁ , 8
₂ and 8 ₃ are images of parts 6 ₁ , 6 ₂ , and 6 ₃ of calligraphy and paintings in the manuscript, respectively. 9 ₁ , 9 ₂ , 9 ₃ are solid sensors,
10 ₁ -1, _{10 1} -2, ..., 10 ₁ -n, 10 ₂
-1, 10 ₂ -2, ..., 10 ₂ -n, 10 ₃ -1,
10 ₃ -2,..., 10 ₃ -n are solid state sensors 9 ₁ ,
9 ₂ and 9 ₃ are shown for each 1-bit light amount conversion unit. The operation of this reading device is as follows. That is, the original 5 is being conveyed in a direction perpendicular to the paper surface,
The direction in which the large number of lenses 7 ₁ , 7 ₂ , 7 ₃ . . . and the solid-state sensors 9 ₁ , 9 ₂ , 9 ₃ , etc. are arranged is the main scanning direction. Lenses 7 ₁ , 7 ₂ , 7 ₃ create reduced images 8 ₁ , 8 ₂ , _{8 3} of calligraphy images 6 ₁ , 6 2 , 6 ₃ on the original on solid-state sensors 9 ₁ , 9 ₂ , 9 _{3 ,} respectively. Image 8 ₁ , 8
Since ₂ and 8 ₃ are inverted images, solid-state sensors 9 ₁ and 9
The output of each bit _{of 2,93 is 101-1,1} from the end.
0 ₁ -2, ..., 10 ₁ -n, 10 ₂ -1, 10 ₂ -
2,...,10 ₂ -n, 10 ₃ -1, _{10 3} -2,
Even _if they are arranged in the order . Therefore, for example, the output of each bit is 10 ₁ -n..., 10 ₁ -2,1
0 ₁ -1, 10 ₂ -n, ..., 10 ₂ -2, 10 ₁ -
It is necessary to extract them in the order of 1, 10 ₃ -n, . . . 10 _{3 -2} , 10 3 -1. Or you need to take the output one by one, store it in memory, and then retrieve it in the correct order. Alternatively, if the head of the recording system is multi-head, each bit of one solid-state sensor and each bit of the recording head corresponding to that solid-state sensor are inverted, so that the read signal of the solid-state sensor can be changed. are sent to the recording system sequentially or in parallel from the end to record, and correct recording is performed.
That is, each bit of the portion of the recording head corresponding to 6 ₁ of the document is related to each bit of the solid-state sensor in the same geometrical relationship as the portion 6 ₁ of the document and its image 8 ₁ . solid state sensor 9 ₂ ,
The same holds true for the relationship between the recording head section ₉₃ and the corresponding recording head section.

Each solid-state sensor must read image information only in a predetermined area of the document, but in order to avoid reading information in other areas at the same time, light shielding means 11 ₁ , 11 ₂ , 11 ₃ , 11 are provided. _Four …
...is provided. For example, the light beam 12 from the part of the image ₆₃ is blocked by the light shielding means ₁₁₂ , so that the photoelectric conversion output of the solid-state sensor ₉₁ is correct when only part of the calligraphy ₆₁ of the manuscript is read. It becomes a signal. Regarding the length of each solid-state sensor, in order to read with high resolution, the length of the photoelectric conversion section array must be equal to the length of each subframe (for example, 6 ₁ ), that is, the lenses 7 ₁ , 7 ₂ , 7 ₃ It is desirable that the lens be a same-magnification system, but in the structure of each solid-state sensor itself, there is a non-conversion area outside the photoelectric conversion part and a light shielding means is provided, so each lens is generally a same-magnification system. The result is a reduced image. By the way, consider the positional accuracy of an imaging system using a plurality of lens systems as shown in FIG. When the imaging lens (for example, 7 ₁ ) is parallel decentered by △ in the direction perpendicular to the optical axis, and the imaging magnification of the lens is β, then
The amount of movement δ of the field of view in the direction perpendicular to the optical axis on the document surface that has an imaging relationship with a specific solid-state sensor has the following relationship.

δ=Δ(1-1/β)...Here, when β>0, erect imaging is formed, and when β<0, inverted imaging is formed.

The fact that the field of view on the document surface that has an imaging relationship with a specific solid-state sensor moves in a direction perpendicular to the optical axis means that the images obtained by the solid-state sensors 9 ₁ , 9 ₂ , 9 ₃ . . . The correspondence relationship between the solid-state sensors 9 ₁ , 9 ₂ , 9 ₃ ...
Jumping and doubling occur at the seams. Therefore, the amount of movement δ of the field of view on the document surface is 1
It is desirable to make it smaller than a certain amount determined by the size of the bit.

For example, if the size on the document surface corresponding to the size of 1 bit of the solid-state sensor is 83.3 μ × 1/β, then the amount of movement δ of the field of view on the document surface is equivalent to 1/4 or less of 1 bit. In order to make the size smaller than 20.8μ×1/β, the imaging magnification β=−0.8 (×0.8 inverted reduction imaging) and δ=△(1+1/0.8)≦26.0, that is, the imaging The amount of parallel eccentricity Δ of the lens (for example, 7 ₁ ) in the direction perpendicular to the optical axis must be 11.55 μ or less. Similarly, if the size on the document surface corresponding to the size of 1 bit of the solid-state sensor is 125 μ × 1/β, then the amount of movement δ of the field of view on the document surface is 1/4 of 1 bit.
In order to make the size on the original surface equivalent to the following, that is, 31.25 μ × 1/β or less, as an inverted reduced image of 0.8 times, δ = △ (1 + 1 / 0.8) ≦ 39.06 μ, that is, the parallel eccentricity of the lens. △ must be 17.4μ or less.
As can be seen from the above, in order to obtain accurate image information with no jumps or overlaps in the original image, it is necessary to The amount of parallel eccentricity △ in the direction perpendicular to must be suppressed to 10μ to 20μ or less. However, the imaging lenses 7 ₁ , 7 ₂ , 7 ₃ ...
If the lens is made of a material that is relatively stable against temperature and humidity, such as glass, each lens must be manufactured separately and then assembled, and the solid-state sensors 9 ₁ , 9 ₂ , 9 ₃ must be assembled. ……
Performing high-precision alignment of 10 to 20 microns requires a lot of effort since there are a large number of lenses, and this becomes a factor that impedes mass production. Furthermore, if the imaging lenses 7 ₁ , 7 ₂ , 7 ₃ . . . are molded with plastic such as acrylic to integrate a plurality of lenses, the solid state sensors 9 ₁ , 9 ₂ , 9 ₃ . . .
Although the time required for alignment during assembly is greatly reduced, moldable optical plastics such as acrylic have large changes in size or refractive index depending on environmental conditions such as temperature and humidity. Therefore, the parallel eccentricity accuracy as shown earlier is
It is difficult to suppress the thickness to 10μ to 20μ or less. For example, looking at the expansion of acrylic due to heat, the linear thermal expansion coefficient is ~6×10 ^-5 cm/cm/℃, so
The amount of linear expansion of acrylic with a length of 200 mm is 480 μm, assuming that the amount of temperature change is 40 degrees (for example, 20 degrees Celsius ± 20 degrees). On the other hand, the coefficient of linear thermal expansion of silicon (Si) and glass (SiO ₂ ), which are the substrates of solid-state sensors, is about an order of magnitude smaller than that of acrylic, so the amount of linear expansion is smaller under the same conditions as in the case of acrylic. , several tens of micrometers, and when the compound eye lens is integrated with acrylic, the amount of parallel eccentricity of the lens with respect to the sensor is several hundred micrometers at most, making it difficult to put it into practical use.

The present invention provides a compact reading device that satisfies the above-mentioned strict alignment accuracy of the sensor and the imaging system and is suitable for mass production.

In the reading device according to the present invention, the imaging system consisting of a plurality of zone plates that projects an image of the original onto the sensor places the original on a transparent substrate, which is the original platen on which the original is placed. The above object is achieved by being provided on the opposite side. By adopting such a configuration, it is possible to simplify the parts necessary for accurately setting the mutual spacing between the document table, the zone plate board, and the sensor board, or to save labor during assembly.

Hereinafter, when the present invention is described in detail with reference to the drawings, a Fresnel type zone plate will be used, but it goes without saying that the present invention may also be applied to a Gabor type zone plate.

FIG. 3 is a diagram for explaining a zone plate used as an imaging system in the reading device according to the present invention. In Figure 3, 13 is the manuscript, 14 ₁ , 1
4 ₂ , 14 ₃ are some of the calligraphy and paintings drawn on the manuscript, 15 ₁ ,
15 ₂ and 15 ₃ are imaging optical systems called zone plates; 16 ₁ , 16 ₂ , and 16 ₃ are images of portions 14 ₁ , 14 ₂ , and 14 ₃ of the calligraphy and painting of the manuscript;
7 ₁ , 17 ₂ , 17 ₃ are thin film sensors represented by amorphous silicon, etc. 18 and 19
Both are optically transparent media such as glass.

The thin film sensor is provided on a transparent substrate 19, and the zone plate is provided on a transparent substrate 18. FIG. 4a is an enlarged view of the zone plate, showing a state in which a Cr metal film 21 is provided on the transparent substrate 18. Figure 4b shows the fourth
A view of figure a viewed from the optical axis 22 direction is shown. As is well known, a Fresnel (or Soret) zone plate has an imaging effect similar to a lens, and as shown in Figure 4 a and b, it alternates between a ring zone through which light passes and a ring zone that is opaque. and rm and rm+1
If the dimension of the ring zone whose radius is (m=1, 2, 3...) is given by rm=√×+, then the focal length f
Provides the same imaging effect as a lens with Here, λ is the wavelength of light. The first-order diffracted light diffracted by each ring zone in FIG. 4 provides an imaging effect with a focal length f. Zone plates usually use monochromatic or quasi-monochromatic light in order to reduce so-called chromatic aberration. FIGS. 4a and 4b show an example in which m=10, and the opaque film 21 for shielding light is obtained by depositing a metal film such as Cr. For example, consider the case where the focal length f=10 mm, the wavelength of light λ=546.07 nm (monochromatic light), and the number of annular zones m=200. At this time, the radius of the minimum circle is r ₁ = 0.07389mm
and the radius of the outermost ring is r ₂₀₀ = 1.04499mm
Or r ₁₉₉ = 1.020966mm. That is, the width of the outermost ring zone is 2.4μ from r ₂₀₀ −r ₁₉₉ . This method of forming an opaque film in a ring shape is possible by photo etching, which is well known as a step in the IC manufacturing process, and allows many zone plates to be formed on the substrate 18 at once with high precision. be able to. On the other hand, thin film sensors such as amorphous silicon 17 ₁ , 17 ₂ , 17 ₃
... are integrally provided on the transparent substrate 19 in a desired pattern using the same photo-etching method as the zone plate, and the thin film sensors 17 ₁ , 17 ₂ , 17 ₃ ... and the zone plate 15
₁ , 15 ₂ , 15 ₃ ..., for example, thin film sensors 17 ₁ , 1
7 ₂ , 17 ₃ . . . on the transparent substrate 19 and the zone plates 15 ₁ , 15 ₂ , 15
_3. A reference pattern for alignment obtained from the same mask may be provided on the transparent substrate 18 on which . . . is provided by a photoetching method. This allows individual sensors to
There is no need to adjust individual imaging elements, and it is relatively easy to align the integrated imaging system with respect to the integrated sensor with high precision (e.g., less than a few microns). be able to. In addition, the substrates of both the imaging system and the sensor are made of a material with excellent environmental resistance such as glass, and if the substrates of both the imaging system and the sensor are made of the same material, the amount of thermal expansion will be greater than that of the sensor. Since both imaging systems are the same, expansion and contraction due to temperature changes is zero, that is, the positional deviation between the imaging system and the sensor is zero. Even if they are not the same type of glass, if you choose one with a small coefficient of thermal expansion, you can achieve the required accuracy (for example, less than 20 μ) in the positional deviation between the imaging system and the sensor due to expansion and contraction due to temperature changes. It can be suppressed.

The example shown in FIGS. 4a and 4b is an example in which opaque and transparent areas are provided alternately in the annular zone from the center. This is called a so-called amplitude type zone plate and is well known. In this case, an example has been shown in which the smallest circle part is opaque, but generally the smallest circle part may be transparent, and opaque and transparent may be alternately repeated outward. In addition, as shown in Figure 5 a and b, although the zone plate transmits light over the entire area, the phase alternately increases by λ/2 (λ: wavelength of light) in the annular zones from the center. A transparent film 24 may be provided. This is called a so-called phase type zone plate and is well known. In FIG. 5a, the refractive index of the transparent film 24 providing a phase shift is np, and its thickness is dp (np-1)dp=λ/2 (λ: wavelength of light). The opaque film 23 provided on the transparent film 24 is a metal film such as Cr. This has the purpose of blocking stray light coming from the original, since the outer surface of the zone plate is an ineffective area that does not contribute to image formation.

As described above, if the zone plates shown in FIGS. 4a, b and 5a, b are used as the imaging systems 15 ₁ , 15 ₂ , 15 ₃ . . .
Sensors 17 ₁ , 17 ₂ , 17 ₃ ... and imaging system 15
It is possible to provide a compact document reading device that satisfies the strict positioning accuracy of ₁ , 15 ₂ , 15 ₃ . . . and is suitable for mass production. In FIG. 3, 20 ₁ , 20 ₂ , 20 ₃ , and 20 ₄ are formed by imaging systems other than the imaging system 15 ₂ , for example, adjacent imaging systems 15 ₁ ,
Since there is a possibility that the light flux may enter the sensor 16 ₂ from other areas of the document via the document 15 ₃ , this is a light shielding means for the purpose of eliminating this.

6a and 6b are diagrams showing an embodiment of the reading device according to the present invention, and FIG. 6a shows a plane parallel to the moving direction of the document as shown by arrow A; b shows a plane perpendicular to the moving direction of the document. In FIG. 6a, 26 is a transparent body which is the substrate of the document table and zone plate row 28, 33 is a sensor row, 34 is a sensor substrate, and 36A and 36B are light sources. As shown in the figure, the zone plate, which is an imaging system, is provided on the surface of a transparent substrate, which is a transparent body that also serves as a document table, on the opposite side to the surface on which the document is placed. In FIG. 6b, 27 is the original, 35 ₁ , 35 ₂ , 35 ₃ are the original calligraphy drawn on the original 27, and 26 is the original platen and zone plate row 2.
The transparent bodies 28 ₁ , 28 ₂ , 28 ₃ are the substrates 32 1 , 32 2 , 32 2 , 35 1 , 35 ₂ , 35 ₃ of the calligraphy and paintings of 35 ₁ , 35 ₂ , 35 ₃ , respectively.
32 ₃ The zone plates 31 ₁ , 31 ₂ , 31 ₃ , and 31 ₄ are in charge of the function of forming an image, and the zone plates 31 1 , 31 2 , 31 3 , and 31 4 focus on the light from the document outside the desired document area and the diffraction order of the zone plate's diffracted light that participates in image formation. Shielding plate for blocking light other than diffracted light, 33 ₁ , 33 ₂ , 3
3 ₃ is a sensor, and 34 is a substrate on which the sensor is provided. Further, 30 is an imaging system 28 and a sensor 3.
In order to position between 3 ₁ , 33 ₂ , and 33 ₃ ,
A spacer solid is provided to integrate the zone plate and the sensor via the adhesive layer 29. To align the zone plate and sensor, when bonding the substrate 26, spacer 30, and sensor substrate 34 to each other, pattern marks on each plate in advance for alignment during bonding, and perform alignment bonding using these marks as a reference. do it.

If a zone plate is provided on the document table as shown in FIG. 6, the distance between the zone plate and the document can be set in advance by the plate thickness of the document table.
This is required in the case of a configuration such as the example shown in FIG. There is no need to adjust the distance between the document surface and the zone plate surface during assembly, or to integrate the document table 13 and the zone plate substrate 18 by adhering them via an intermediate whose thickness is accurately set. .

FIGS. 7a and 7b are diagrams showing other embodiments of the reading device according to the present invention. The device shown in FIG.
Similar to the apparatus shown in the figure, a indicates a plane parallel to the moving direction of the document, and b indicates a plane perpendicular to the moving direction. In FIG. 7a, 36 is a transparent body serving as a substrate for the document table and zone plate row 40, 46 is a sensor row, 43 is a sensor substrate, and 37 _A and 37 _B are light sources. In FIG. 7b, 38 is a manuscript, 39 ₁ , 39 ₂ , 39 ₃ are manuscript drawings drawn on the manuscript surface, and 36 is a manuscript table/zone plate row 40
The transparent bodies 40 ₁ , 40 ₂ , 40 ₃ are the calligraphic images 47 ₁ , 47 of 39 ₁ , 39 ₂ , 39 ₃ respectively.
A zone plate for imaging ₂ , 47 ₃ , 44 ₁ ,
44 ₂ , 44 ₃ , 44 ₄ and 45 ₁ , 45 ₂ , 45 ₃ ,
45 ₄ is the light from the original outside the desired original area and
These are a shielding plate and a shielding groove for shielding light other than diffracted light of a diffraction order that contributes to image formation among the diffracted light of the zone plate. 45 ₁ , 45 ₂ , 45 ₃ , 4
5 ₄ is a light-shielding groove provided in the sensor substrate 43, and is designed to block light incident obliquely here. 46 ₁ , 46 ₂ , 46 ₃
is a sensor, 41 is an imaging system 40 and a sensor 46 ₁ ,
This is a spacer provided to integrate the zone plate and the sensor via the adhesive layer 42 in order to position the zone plate and the sensor 46 ₂ and 46 ₃ .
The positioning between the zone plate and the sensor can be achieved by providing alignment reference marks on each substrate and spacer before adhesion, as in the embodiment shown in FIG.

In the above embodiments, the sensor is generally a thin film sensor such as amorphous silicon.
It may also be a solid state sensor such as a CCD. Also,
In any of the above embodiments, the zone plate may be a so-called amplitude type zone plate as shown in FIG. 4, or a phase type zone plate shown in FIG. 5. In either case, an opaque film such as a metal film is provided on the surface of the zone plate other than the effective opening surface.

As explained above, the present invention provides a document reading device (for example, a facsimile machine, ), by making the substrate on which the imaging system consisting of the zone plate is installed and the document table the same, a compact device suitable for mass production can be obtained.

[Brief explanation of drawings]

1 and 2 are diagrams explaining a conventional reading device, and FIGS. 3, 4 a, b, and 5 a, b each show a zone plate applied as an optical system to the reading device of the present invention. The figures for explanation, FIGS. 6a and 6b and FIGS. 7a and 7b, each show an embodiment of the reading device according to the present invention. 26...Original table, 27...Original, 28 ₁ , 28
₂ , 28 ₃ ... Zone plate, 29 ... Adhesive layer, 30 ... Spacer, 31 ₁ , 31 ₂ , 31 ₃ ,
31 ₄ ... light shielding plate, 33 ₁ , 33 ₂ , 33 ₃ ... sensor, 34 ... board.

Claims (1)

[Claims] 1. An imaging system consisting of a plurality of zone plates that projects an image of the original onto a sensor is provided on a surface of a transparent substrate, which is a document table on which the original is placed, opposite to the surface on which the original is placed. A reading device characterized by: