JPS6343470A - Image reader - Google Patents

Abstract

PURPOSE:To prevent the lowering of picture quality and to realize a faithful reading of an image by forming a projecting image and a reflected image on a long type solid-state image pickup element by a convergent light transmitter array by making the number of Fresnel lens one. CONSTITUTION:An original picture 1 illuminated by a projector 3 is projected by a projection lens 2 and projected on an original platen through a halfway light path bending mirror 4. A Fresnel lens 5 is provided a little apart from an original platen glass 6 on the way of projection, and principal ray of luminous flux of the projecting image is made perpendicular to the original platen glass 6 at any place. The image on the original platen 6 is led to a long type solid-stage image pickup element 8 through a convergent light transmitter array 7. Principal ray of the projected image passed through the Fresnel lens 5 becomes parallel to the optical axis of the convergent light transmitter array 7, and thereby, the image on the original platen is formed effectively on the long type solid-state image pickup element 8.

Description

Detailed Description of the Invention B. Purpose of the Invention [Field of Industrial Application] The present invention is an image reading device applied to facsimiles, electrophotographic copying devices, etc. The present invention relates to an image reading device that can also read a projected image of an original image, such as a film, projected from a projection device.

[Conventional technology]

FIG. 4 is a front view showing the overall configuration of a conventional image reading device. In the figure, 1 is an original image such as a film, 2 is a projection lens, 3 is a projection device equipped with an original image L and a projection lens 2, and 4 15 is a fixed mirror that directs the projected image onto the document table; and 15 is an imaging lens that forms the image on the document table guided through the plane mirrors 12 to 14 onto the solid-state image sensor 16.

The spherical imaging lens 15 reduces the image on the document table and forms the image on the solid-state imaging device 16. Main scanning is performed by the solid-state imaging device 16, and sub-scanning is performed using several plane mirrors 12 to 1.
4 in the direction of the arrow to read the image.

[The intermediary point that Hatsu E month tries to resolve]

When reading a projected image, a sufficient amount of light will not reach the solid-state image sensor unless the principal ray of the projection optical system is directed toward the entrance pupil of the image reading lens.

In this reading system, the chief ray from the projection lens 2 enters the entrance pupil of the imaging lens 15, so in the main scanning direction, as shown in FIG.
As shown in a), it must be directed from the position of the document table toward the entrance pupil of the imaging lens 15.

On the other hand, in the sub-scanning direction, as shown in Figure 5(b), the direction of the principal ray must be oriented perpendicular to the document table at any position on the document table. It differs depending on the scanning direction.

To actually do this, it is not possible to use a normal rotationally symmetrical Fresnel lens as a field lens. Therefore, in order to change the direction of the principal ray in the main scanning direction, a cylindrical Fresnel lens that has refractive power only in the main scanning direction is used. Two Fresnel lenses are required: the lens 10 and the Fresnel lens 11 having refractive power only in the sub-scanning direction, which changes the direction of the chief ray in the sub-scanning direction.

It is better to place the Fresnel lenses 10 and 11 on the document table 6 with an imaging trowel, but in this state, the Fresnel lenses 10 and 11
The grooves are also imaged by the imaging lens 15 onto the solid-state imaging device 16, and the images read and reproduced at the same time are of poor quality.

To avoid this, as shown in FIG. 6, the Fresnel lens to-it is placed slightly above the document table 6 so that the groove of the Fresnel lens 10-11 does not form an image on the solid-state image sensor 16k.

In this case, since the cross section of the light beam of the captured image when passing through the Fresnel lenses 10 and 11 has a certain area, the Fresnel lens 1
0-11 causes aberrations and the quality of the projected image deteriorates to some extent. Therefore, since the above-mentioned image reading device uses two Fresnel lenses, there is a drawback that the image quality is further deteriorated.

The present invention has been made to solve the above-mentioned drawbacks.
An object of the present invention is to obtain an image reading device that can read projected images and reflected images without degrading image quality as much as possible.

SUMMARY OF THE INVENTION [Means for solving the problems] The present invention provides an image reading device that reads a projected image from an original image and a reflected image from a document using a solid-state image sensor.
a convergent light transmitter array for reading the projected image and the reflected image; a long solid-state image sensor for converting the same-magnification image formed by the convergent light transmitter array into an electrical signal; and an exit pupil of a photographing lens. and a field lens that brings the projected image closer to the focal point and guides the projected image to the convergent light transmitting body array.

[For production]

The image reading device of the present invention forms a projected image and a reflected image on a long solid-state image sensor using a convergent light transmitting array, thereby preventing deterioration in image quality by using only one Fresnel lens. The key is to read the image faithfully.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1, in which the same parts as in FIG. 4 are denoted by the same reference numerals. In Figure 1,
5 is a Fresnel lens; 7 is a convergent light transmitting element array; 8 is an elongated solid-state image sensor; 9 is an image reading device that supports the convergent light transmitter array 7 and the elongated solid-state image sensor 8 in a predetermined positional relationship. It is a unit.

The original image l illuminated by the projection device 3 is projected by the projection lens 2 and imaged onto the document table via the optical path bending mirror 4 midway. In the middle of this projection, the groove is placed slightly away from the document platen glass 6 so that the read image is not affected by the image, and is designed so that its focus is on the exit pupil of the projection lens 2. Due to the disposed Fresnel lens 5, the chief ray of the light beam of the projected image is perpendicular to the document table glass 6 at any location.

The individual optical axes of the convergent light transmitting body array 7 that focuses the image on the document table 6 onto the elongated solid-state image sensor 8 are as follows.

It is always perpendicular to the document table glass 6. Therefore, the chief ray of the projected image that has passed through the Fresnel lens 5 is parallel to the optical axis of the convergent light transmitter array 7 for image reading, and the image formed anywhere on the document table is transmitted by convergent light. The image is effectively formed on the elongated solid-state image sensor 8 by the body array 7 .

FIG. 2 shows that the principal ray of the projection light beam in the main scanning direction and the sub-scanning direction coincides with the optical axis of the convergent light transmission array 7 for image reading. Figure 2 (a) shows the state of the chief ray in the main scanning direction.Since the focal point of the Fresnel lens 5 is on the exit pupil of the projection lens 2, the principal ray after passing through the Fresnel lens 5 is perpendicular to the platen glass surface. This coincides with the direction of the optical axis of each element of the convergent light transmitter array 7, and effectively reaches the elongated solid-state tail image element 8.

FIG. 2(b) shows the state of the principal ray in the sub-scanning direction. After passing through the Fresnel lens, the principal ray is perpendicular to the document table 6, so the image reading unit 9 that scans the image is Even when the projection light beam is moved to another position, the principal ray of the projection light beam can be made to coincide with the optical axis of the convergent light transmission body array 7, and effectively reaches the elongated solid-state image sensor 8.

In this case, if a Fresnel lens is placed on the document table glass 6'' as shown in FIG. The grooves appear in the reproduced image, significantly degrading the image quality.

Therefore, as shown in FIG. 3(b), it is placed slightly away from the document table glass 6.

In Fig. 3(a), the projected image is focused on the Fresnel lens surface, and the image quality of the projected image is not degraded by the Fresnel lens, but as shown in Fig. 3(b), the projected image is formed on the Fresnel lens surface. If they are separated, the projection light beam entering the Fresnel lens has a certain spread, so aberrations change depending on the refractive power, thickness, etc. of the Fresnel lens, and the image quality deteriorates to some extent.

However, in the present invention, it is possible to match the principal ray of the projection light flux with the principal ray of the reading system in both the main scanning direction and the sub-scanning direction with a single Fresnel lens, and compared to the conventional method using two Fresnel lenses. Compared to this, it is possible to avoid a significant deterioration in image quality.

C. Effects of the Invention As described above, according to the present invention, the projected image and the reflected image are formed on the elongated solid-state image sensor H by the converging light transmitting body array, so that the Fresnel lens used is Since only one sheet is required, it is possible to avoid a significant deterioration in image quality compared to conventional devices that require the use of two sheets, and there is an effect that the projected image and the reflected image can be read faithfully.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an image reading device according to an embodiment of the present invention, and FIGS. 2(a) and 2(b) are principal rays of projection light beams and images in main scanning and sub-scanning in the image reading device. Figures 3(a) and 3(b) are diagrams showing the relationship between the principal ray in the reading system and the relationship between the position of the Fresnel lens and the projected light flux.
The figure is a front view of a conventional image reading device.
b) is a diagram showing the relationship between the chief ray of the projection light flux in main scanning and sub-scanning in the device and the chief ray in the image reading system, and Figure 6 shows that the projection light flux passes through two Fresnel lenses. It is a diagram. 2 is a projection lens, 5 is a Fresnel lens, 6 is a manuscript table, 7
8 is a convergent optical transmitter array, and 8 is a long solid-state image sensor. (Q) Figure 5 (b) ・'/Me7i Thoughts

Claims (1)

[Claims] (1) In an image reading device that reads a projected image from an original image and a reflected image from a document using a solid-state image sensor, a convergent light transmission body array that reads the projected image and reflected image;
a long solid-state image sensor that converts the same-magnification image formed by the convergent light transmitting body array into an electrical signal; and a long solid-state image pickup device that converts the image formed at the same magnification by the convergent light transmitting body array, and a projection image that is focused on the exit pupil of the photographing lens and transmitting the projected image to the convergent light transmitting body array. An image reading device characterized by comprising a field lens for guiding the image.