JPH03295354A - Picture reader - Google Patents

Abstract

PURPOSE:To set a range wide where an original picture is prevented from being blurred by using a plural unmagnified image-forming lens arrays different in a conjugate length and permitting respective unmagnified image-forming lens arrays to differ the range of a focus depth. CONSTITUTION:The refractive index distribution-type unmagnified image-forming lens array 1 having the conjugate length TC 1, the unmagnified image-forming lens array 2 having the conjugate length TC 2 and the photoelectric conversion element arrays 3 and 4 which respectively correspond to the unmagnified image- forming lens arrays 1 and 2 are provided. Thus, the range of the focus depth can be made different in respective unmagnified image-forming lens arrays 1 and 2 by using plural unmagnified image-forming lens arrays 1 and 2 different in the conjugate length. Then, they are constituted so that an original surface exists in the focus depth of the unmagnified image-forming lens arrays 1 and 2. Thus, the range where the original picture is prevented from being blurred can be set wide and an accurate picture signal can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image reading device used as an image reading device for a facsimile, an image scanner, an OCR (optical character reader), a computer, etc. The present invention relates to an image reading device that can obtain an image signal without blur while using an image lens system.

(Prior art) In recent years, in order to miniaturize image reading devices, photoelectric conversion element arrays have been formed to have a length equal to the width of the original to be read, and the distance between the original to be read and the photoelectric conversion element array has been shortened. has been proposed. The reading section of this image reading device is
As shown in FIG. 6, it has a photoelectric conversion element array 61 formed of a laminated structure of thin films and elongated in the front and back directions of the figure, and a refractive index gradient array 62 as a same-magnification imaging system, The platen glass 63 is installed so that the upper end portion of the platen glass 63 is located at the focal point of the gradient index array 62.

Then, when each photoelectric conversion element constituting the photoelectric conversion element array 61 is irradiated with reflected light containing brightness information of minute areas of the original image, charges corresponding to this reflected light are generated. The charges generated in each charging conversion element are extracted in time series to one output line by a switch in a drive IC (not shown) that sequentially selects each photoelectric conversion element.

(Problem to be Solved by the Invention) However, the depth of focus of the refractive index gradient array 62 is practically 0.5 mm or less, and there may be irregularities in the read document, or the document 64 may be lifted off the platen glass 63. (book-type original), the image signal will be blurred. In an apparatus configured to fix the read original 64 on the platen glass 63 while electrically scanning the photoelectric conversion element array 61, this may adversely affect the formed image, including distortion of the platen glass 63. It is from.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide an image reading device that can obtain an image signal without blur even when using an equal-magnification imaging lens system with a shallow depth of focus.

(Means for Solving the Problems) In order to solve the problems of the above-mentioned conventional example, the invention of claim 1 provides the following:
It is characterized by comprising a plurality of equal-magnification imaging lens arrays having different conjugate lengths and photoelectric conversion element arrays respectively corresponding to the equal-magnification imaging lens arrays.

According to a second aspect of the invention, in the image reading apparatus according to the first aspect, a light shielding means is provided between the equal-magnification imaging lens arrays along the longitudinal direction.

(Function) According to the invention of claim 1, since a plurality of equal-magnification imaging lens arrays having different conjugate lengths are used, the depth of focus range can be made different for each equal-magnification imaging lens array. Therefore, by making the document surface exist within the focal depth of any one of the equal-magnification imaging lens arrays, it is possible to set a wide range in which the document image does not become blurred.

According to the invention of claim 2, since the light shielding means is provided along the longitudinal direction between the equal-magnification imaging lens arrays, the same-magnification imaging lens array adjacent to the photoelectric conversion element array corresponding to each equal-magnification imaging lens array is There is no influence of light emitted from the image lens array.

(Example) An example of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of the structure of the image reading device of the present invention, which includes a refractive index distribution type equal-magnification imaging lens array 1 having a conjugate length TCI, and a equal-magnification imaging lens array 2 having a conjugate length TC2.
and a photoelectric conversion element array 3.degree. 4 corresponding to the equal-magnification imaging lens array 1.2, respectively.

The photoelectric conversion element arrays 3 and 4 are each formed on a substrate 5 so as to be elongated in the front and back directions of the figure, and the same-magnification imaging lens arrays 1 and 2 are arranged to face the photoelectric conversion element arrays 3 and 4. It is installed in

The photoelectric conversion element arrays 3 and 4 are, for example, metal electrodes.

It has a thin film structure formed by sequentially laminating a photoelectric conversion layer and a transparent electrode and photolithographically etching them.

The same-magnification imaging lens array 1.2 is a photoelectric conversion element array 3.
．． 4, they are elongated in the front and back directions of the figure and are arranged parallel to each other.

As shown in FIG. 2, the focal plane A of the equal-magnification imaging lens array 1 is located approximately 0.4 mm above the glass surface 6a of the platen glass 6 installed on the equal-magnification imaging lens array 12. That's what I do. Therefore, the depth of focus P1 of the 1-magnification imaging lens array 1 is set within a range of about 0.5 mm vertically centered on the focal center plane A of the 1-magnification imaging lens array 1, and the lower end thereof Surface 6a
Position it further down. In addition, by installing the focal center plane B of the equal-magnification imaging lens array 2 to be located approximately 1.2 mm above the glass surface 6a of the platen glass 6, the focal depth P2 of the equal-magnification imaging lens array 2
is set in a range of about 0.5 mm vertically with respect to the focal center plane B of the equal-magnification imaging lens array 1. As shown in the figure, the focal depth P1 of the equal-magnification imaging lens array 1 and the focal depth P2 of the equal-magnification imaging lens array 2 are arranged so that there is an overlapping portion C. This is to ensure that the document surface is always within the depth of focus of one of the equal-magnification imaging lens arrays.

When the document surface placed on the top surface of the platen glass 6 is used as the reference surface, the conjugate length TC of each equal-magnification imaging lens array 1°2
I, TC2 as ITcI-TC2+≦depth of focus (0.5m
m) x 2, and the reference plane is set to (TCI
-Te3)/2, the depth of focus P3 of the entire imaging device can be improved to approximately twice that of an image reading device having a single equal-magnification imaging lens array.

The image signals detected by each photoelectric conversion element array 3, 4 are processed according to a block diagram as shown in FIG. The image signals of the lines detected at the same time by the photoelectric conversion element arrays 3 and 4 read original images shifted by an interval in the original feeding direction Y shown in FIG. The image signals from the sensors 3a and 4a for each bit of the photoelectric conversion element array 3.4 are input to a delay circuit 7.8, and the image signals are subjected to delay processing to produce image signals obtained by reading the same portion of the document. to be able to compare. Next, the sensor selector 9 compares the contrasts of the image signals of the respective sensors 3a and 4a, and outputs the image signal with higher contrast, thereby making it possible to obtain an image signal with less blur.

FIG. 4 shows a specific example of an image reading device with an integrated light source.
Photoelectric conversion element arrays 3 and 4, light sources 11 and 12, light shielding plate 1
3 are fixed respectively. The same-magnification imaging lens arrays 1 and 2 are arranged so that their ends on the side of the photoelectric conversion element arrays 3 and 4 are aligned. The light source 11.12 is a fluorescent light source fixed along the 1-magnification imaging lens array 1.2. The light shielding plate 13 is made of a material through which light cannot pass, and is provided along between the equal-magnification imaging lens arrays 1 and 2. The photoelectric conversion element arrays 4.2 and 4.2 are installed so that stray light from each photoelectric conversion element array 4.3 does not affect the other photoelectric conversion element arrays 4.3.

FIG. 5 shows another specific example of the image reading device, in which equal-magnification imaging lenses 21.
22, and are arranged with the edges on the document surface side aligned. Since the equal-magnification imaging lenses 21 and 22 have different conjugate lengths TC, T
It is necessary to provide a step on the photoelectric conversion element arrays 3 and 4 by the difference in C.

In this embodiment, the photoelectric conversion element arrays 3 and 4 are formed on separate substrates 51 and 52, and are overlapped to create a step, so that the photoelectric conversion elements Arrays 3 and 4 can be installed. The other configurations are the same as the image reading device shown in FIG. According to this embodiment, since the edges of the Δ imaging lenses 21 and 22 on the document surface side are aligned, a space on the document surface side can be secured.

(Effects of the Invention) According to the invention of claim 1, since a plurality of equal-magnification imaging lens arrays having different conjugate lengths are used, it is possible to make the depth of focus range different for each equal-magnification imaging lens array. can. Therefore, by making the document surface exist within the focal depth of any of the equal-magnification imaging lens arrays, it is possible to set a wide range in which the document image is not blurred, and it is possible to obtain accurate image signals.

According to the invention of claim 2, since the light shielding means is provided along the longitudinal direction between the equal-magnification imaging lens arrays, the same-magnification imaging lens array adjacent to the photoelectric conversion element array corresponding to each equal-magnification imaging lens array is High-resolution image signals can be obtained without being affected by light irradiation from the image lens array.

[Brief explanation of drawings]

1 is a structural explanatory diagram showing the structure of the image reading device of the present invention, FIG. 2 is an explanatory diagram for explaining the depth of focus of the image reading device of the present invention, and FIG. 3 is the image reading device of FIG. 1. 4 is a cross-sectional explanatory diagram showing a specific example of an image reading device. FIG. 5 is a cross-sectional explanatory diagram showing another specific example of an image reading device. FIG. 6 is a structural explanatory diagram showing the structure of a conventional image reading device. 1.. . . 2. . 3.. .. 4 . . 6. . 7 . 8 . Element array platen glass delay circuit delay circuit sensor selector light shielding plate Fig. 2 Fig. 3 Fig. 0

Claims (2)

[Claims] (1) An image reading device comprising a plurality of equal-magnification imaging lens arrays having different conjugate lengths and photoelectric conversion element arrays respectively corresponding to the equal-magnification imaging lens arrays. (2) The image reading device according to claim 1, further comprising a light shielding means provided along the longitudinal direction between the equal-magnification imaging lens arrays.