JPH0195661A - Picture reader - Google Patents

Abstract

PURPOSE:To obtain the title picture reading device with a simple constitution which can process color picture information on a real time basis by providing an anamorphic optical element to have a refracting power in the parallel- arrangement direction of at least plural line sensors at a projecting system. CONSTITUTION:The projecting system has an anamorphic optical element 3 to possess the refracting power in the parallel-arrangement direction of at least plural line sensors 6-8. By arranging the anamorphic optical element 3 with a prescribed shape in the light path of the projecting system, an identical part on an original surface 1 can be highly accurately read by means of the plural line sensors 6-8 having intersections to a certain extent. Thus, the color processing of the color picture can be performed on the real time basis, made faster, and further, the small picture reading device with the simple constitution without plural color filters or plural light sources can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image reading device, and in particular to a color scanner that can read color image information on a document surface with high precision by using a plurality of line sensors. The present invention relates to an image reading device suitable for color facsimile and the like.

(Prior art) Conventionally, color image information on the document surface is transmitted through an optical system.
Various devices have been proposed that form an image on the surface of a line sensor such as a CD and read color image information using the output signal from the line sensor at this time.

In this case, the color image information can be read by, for example, scanning the document surface 3 to 4 times each time through a filter with predetermined spectral characteristics and reading image information corresponding to each color light, or Using a light source, the light source is sequentially turned on with three or four colored lights to illuminate the document surface, and image information in each colored light is read in chronological order.

However, in the former method, the filter switching mechanism for each scan is complicated, and in the latter method, three to four light sources are selected and used, so adjustment of each of these light sources,
None of these methods were very preferable because the control mechanism was complicated.

On the other hand, as shown in FIG. 3, an apparatus has been proposed that reads color image information on the surface of a document using three line sensors set to have three types of spectral sensitivity characteristics.

In the figure, 31 is a light receiving surface, and on the light receiving surface 31, there are three line sensors 32, 33.3, such as COD, which have spectral sensitivities for the three primary colors of red R, edge color G, and blue B.
4 is placed. The light receiving surface 31 is in a conjugate relationship with the document surface 36 by the imaging lens 35. The longitudinal direction of each line sensor 32, 33, 34 is the document surface 3
6 correspond to the directions of line segments 37, 38, and 39, respectively.

Therefore, image information in the directions of line segments 37, 38, and 39 on the original surface 36 is read by line sensors 32, 33, and 34, respectively. In this way, three line sensors can be used to
The upper pixel row in one direction is read with each color of light.

Generally, the distance between each line sensor is about 0.3 mm to several mm, and the imaging lens 35 is usually reduced on the line sensor side.
It is enlarged on the manuscript side. Therefore, the reading interval on the document surface is several man for each line sensor 32°33.34.
It will expand.

For this reason, it is difficult to perform color processing on the read color image information in real time, and in order to perform color processing in real time,
There were problems such as the need to prepare a certain amount of memory for processing.

In response, a line sensor has been proposed in which multiple elements with R, G, and H sensitivities are arranged on one line as shown in Figure 4, but the area of each light-receiving surface is small, and the necessary It is difficult to secure a sufficient amount of light for the purpose of use, and it is difficult to deposit color filters on each element, making it difficult to miniaturize the elements.

There is also a method of arranging three line sensors with R, G, and H sensitivities as shown in Figure 5, but this method requires less electrical circuit routing because the light-receiving surfaces are arranged two-dimensionally. There were drawbacks such as the complicated process.

(Problems to be Solved by the Invention) The present invention does not require a switching mechanism for color filters having predetermined spectral characteristics or a switching mechanism for multiple light sources to obtain colored light of the three primary colors, and does not require a memory. An object of the present invention is to provide an image reading device with a simple configuration that is capable of processing color image information in real time without using the image reading device.

(Means for solving the problem) A light beam from the document surface is made incident on a plurality of line sensor surfaces parallel to each other through a projection system, and the document is colored in at least two or more colors. In the image reading device, the projection system includes an anamorphic optical element having refractive power at least in the direction in which the plurality of line sensors are arranged side by side.

(Example) Fig. 1 is a schematic diagram of an optical system according to an embodiment of the present invention, and Fig. 2 (
A) and (B) are explanatory diagrams showing the optical conjugate relationship in FIG. 1.

In the figure, 1 is the document surface on which color image information is recorded. 3 is an anamorphic optical element as a rotationally asymmetric optical member, and in this embodiment, a cylindrical lens is used. Reference numeral 4 denotes a projection lens consisting of a rotationally symmetrical spherical optical system. The anamorphic optical element 3 and the spherical optical system 4 constitute one element of the projection system. 5 is a light-receiving surface, and on the light-receiving surface 5 there are, for example, 3 layers each having a different spectral sensitivity.
Three line sensors 6°7.8 are arranged to have spectral sensitivities for the primary colors red R1 green G and blue B.

The three line sensors 6.7.8 are set so that their longitudinal directions (element arrangement direction) are substantially parallel to each other, and these three line sensors 6.7.8 constitute one light receiving means. , image information of pixel rows 2 in one direction on one side of the original is read.

The longitudinal direction of the central line sensor 7 and the axis 31 of the cylindrical lens in a direction in which it does not have refractive power are set to be substantially parallel.

2(A) and 2(B) are explanatory views showing the optical conjugate relationship of the optical system of FIG. 1. FIG. 3A is a cross-sectional view taken in a direction perpendicular to the longitudinal direction of the line sensor, and FIG. 1B is a cross-sectional view taken in a direction parallel to each line sensor.

The cylindrical lens 3 has refractive power within the plane shown in FIG. 2(A). The cylindrical lens 3 establishes an optically conjugate relationship between the pupil of the projection lens 4 and the document surface 1 within the plane of FIG. 2A. Therefore, the light receiving surface 5 where the line sensor 6.7°8 is arranged and the document surface 1
is somewhat deviated from the conjugate relationship.

The center of the luminous flux from each line sensor 6, 7, 8 passes through the center of the projection lens 4 and is condensed at a predetermined position Ia on the document surface 1 by the cylindrical lens 3.

That is, the light beams emitted from one point of each line sensor 6, 7, 8 are collected in the same area 1a on the document surface 1. Considering this in reverse, it means that the light beam from a certain point 1a on the document surface 1 is guided onto each line sensor 6, 7, and 8 surface on the light receiving surface 5 by the cylindrical lens 3 and the projection lens 4. It shows.

Due to the imaging effect of the cylindrical lens 3 and the projection lens 4, the best position of the document surface detected by each line sensor is a position 21 shown by a broken line.

However, since the depth of field on the enlarged side of the document surface 1 is generally deep, the document surface 1 can be sufficiently set within the depth of focus.

FIG. 2(B) is an explanatory diagram of the optical system on a plane where the cylindrical lens 3 has no refractive power.

In the figure, the light receiving surface 5 and the original surface 1 are in a conjugate relationship due to the projection lens 4.

In this embodiment, the optical system having the above-mentioned configuration allows the original surface 1 to be
The color image information on the three line sensors 6.7.8
Light is guided onto the surface and color image information on the document surface 1 is read.

FIG. 6 is a schematic diagram of an optical system according to another embodiment of the present invention. In this embodiment, a cylindrical mirror 61 is used as an anamorphic optical element.

That is, the light beam from the document surface 1 is transferred to the cylindrical mirror 61.
After being reflected by the projection lens 4, the light is guided onto each line sensor surface 6, 7.8, and the image is read.

In this embodiment, it is more preferable to share the scanning mirror.

If a toric lens 71 as shown in FIGS. 7(A) and 7(B) is used instead of the cylindrical lens in the embodiment shown in FIG. 1, various optical aberrations (field curvature, etc.) can be corrected well, which is preferable.

Note that FIG. 7(A) is a cross-sectional view in a direction parallel to the longitudinal direction of the line sensor of the toric lens, and FIG. 7(B) is a cross-sectional view in the longitudinal direction and perpendicular direction of the line sensor. It is preferable to use an aspherical surface for the cylindrical lens or toric lens because various optical aberrations can be further reduced.

(Effects of the Invention) According to the present invention, by arranging an anamorphic optical element with a predetermined shape in the optical path of the projection system, the same part on the document surface can be detected with high accuracy using a plurality of line sensors or the like spaced apart to a certain extent. This enables real-time and high-speed color processing of color images.
Furthermore, it is possible to achieve a compact image reading device with a simple configuration that does not require multiple color filters or multiple light sources.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an optical system according to an embodiment of the present invention, and Figure 2 (
A) and (B) are explanatory diagrams showing the optical conjugate relationship in FIG. 1, FIG. 3 is a schematic diagram of a conventional image reading device, and FIG. Fifth
The figure is an explanatory diagram of a conventional line sensor, FIG. 6 is a schematic diagram of an optical system according to another embodiment of the present invention, and FIG. 7 (A), (
B) is an explanatory diagram of an anamorphic optical element applicable to the present invention. In the figure, 1 is a document surface, 3, 61.71 is an anamorphic optical element, 4 is a projection lens, 5 is a light receiving surface, and 6, 7, 8 is a line sensor. Patent Applicant: Canon Co., Ltd. [-1-no-taku 4 Kasumidai 5 [2]

Claims (1)

[Claims] In an image reading device that reads the document in at least two colors by making the light beam from the surface of the document incident on a plurality of line sensor surfaces arranged parallel to each other via a projection system, the projection system An image reading device comprising an anamorphic optical element having refractive power at least in the direction in which the plurality of line sensors are arranged side by side.