JPH04223665A - Picture reader - Google Patents

Abstract

PURPOSE:To obtain a picture having a high picture quality without any blurring by applying a pressing pressure according to the thickness of original, and to use a motor at a low cost of with a reduced torque load as a driving system by relatively reducing the pressing pressure in a state before the original is inserted, in which the torque load is the highest. CONSTITUTION:A picture reader which feeds an original 2 by pressing the original 2 to a photoelectric converting part 1 by a back roller 3, and rotating the back face roller 3, is equipped with a spring 4 which pressurizes the back roller 3, and a spring 5 which further pressurizes the back roller 3 in addition to the pressure by the spring 4 when the back roller 3 is lifted up by the original 2 while being beyond a fixed value against the photoelectric converting part 1.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to an image reading device.
In particular, the present invention relates to an image reading device that presses a document against a photoelectric conversion unit using a rear roller and feeds the document by rotating the rear roller.

0002

[Prior Art] In recent years, image reading devices using a one-dimensional line sensor have advantages such as a simplified optical system, so a one-dimensional optical system equipped with a long one-dimensional line sensor with the same length as the document width has been developed. systems are increasingly being adopted. As for 1-magnification optical systems, in addition to methods that use focusing fibers and contact lens arrays, there is also a complete contact method that does not use these at all and reads the document while moving it in close contact with the one-dimensional line sensor. . Examples of this complete adhesion method include JP-A-55-74262, JP-A-55-75271, and JP-A-56-45.
Systems disclosed in Japanese Patent Application Laid-open No. 084, Japanese Patent Application Laid-open No. 56-122172, and the like are known.

A general structure of an image reading apparatus using such a complete contact method is as shown in FIGS. 4 and 5. FIG. 4 is a schematic side view showing the configuration of a conventional image reading device. FIG. 5 is a schematic perspective view showing the configuration of a conventional image reading device.

In FIGS. 4 and 5, a document 2 is conveyed between a back roller 3 and a photoelectric conversion section 1 by rotation of the back roller 3. As shown in FIG. At this time, due to the pressing pressure of the back roller 3 applied by the spring 4, the original 2 is brought into close contact with the one-dimensional line sensor in the photoelectric conversion section 1, and image information is read.

[0005]

However, in recent image reading apparatuses, there has been an increasing demand for "multi-tone reading" instead of "two-tone reading" in black and white. This means that manuscripts such as photographic manuscripts have become more diverse, and the following problems have been highlighted.

[0006] That is, documents with thick paper (such as photo manuscripts)
When reading an image, the stiffness of the paper is stronger than the pressing pressure of the back roller, and the one-dimensional line sensor and the document do not come into close contact over the entire reading width, resulting in a blurred image. In order to prevent this image blurring, it is possible to increase the pressing pressure of the rear roller, but this method has the following problems.

[0007] During the time it takes for the original to be transferred between the back roller and the photoelectric conversion unit, there is friction between the back roller and the photoelectric conversion device, which has a coefficient of friction higher than that between the original and the photoelectric conversion unit. Since there is direct contact, a large amount of force is required to drive this system (for example, a large torque motor is required).

[0008]

[Means for Solving the Problems] An image reading device of the present invention is an image reading device in which a document is pressed against a photoelectric conversion unit by a back roller and the document is sent by rotating the back roller. a first pressing means for applying pressure, and a pressure applied to the back roller in addition to the pressure by the first pressing means when the back roller is lifted by a document beyond a certain value with respect to the photoelectric conversion unit; and a second pressing means for applying.

[0009]

[Operation] When reading a thin document, the present invention
The back roller is pressed by the pressure (P1) by the first pressing means, and when the paper thickness becomes thick and the back roller is lifted by a certain value or more with respect to the photoelectric conversion unit, the pressure (P1) is applied to the second pressing means. Pressure by pressing means (P2
) is applied to press the back roller with pressure (P1 + P2).

0010

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings. FIG. 1 is a schematic side view of a first embodiment of an image reading device of the present invention. In FIG. 1, 1 is a photoelectric conversion unit, 2 is an input document, 3 is a back roller, 4 is a spring that is the first pressing means that applies pressing pressure to the back roller 3, and 5 is attached to the back roller together with the spring 4. This is a second spring serving as a second pressing means that applies pressing pressure. The spring 4 and the spring 5 have a gap t, and the document 2 exceeding a certain thickness
When a document is input, the back roller 3 is lifted, and when the lifted length exceeds the gap t, the spring 5 becomes effective, forming a so-called non-linear spring mechanism.

[0011] In the image reading device of this embodiment, the document is placed in the gap t.
0 (usually around 200 μm) or before the document is loaded, only the spring 4 applies pressing pressure to the back roller 3, and in the case of a document with a thickness exceeding the gap t0, the combined force of the springs 5 and 4 applies pressure to the back roller 3. Fig. 3 shows the nonlinear characteristics of this mechanism.

FIG. 2 is a schematic side view of a second embodiment of the image reading apparatus of the present invention. In FIG. 2, as in FIG. 1, 1 is a photoelectric conversion unit, 2 is an input document, 3 is a back roller, and 4 is a spring serving as a first pressing means that applies pressing pressure to the back roller 3. . 6 is a second spring serving as a second pressing means that applies pressing pressure to the back roller 3 together with the spring 4, and 7 is a screw that adjusts the gap t in which the spring 5 is effective. The spring 4, spring 6, and screw 7 constitute a nonlinear spring mechanism. In this embodiment, the gap t can be freely changed by adjusting the screw 7.

[0013]

As described above in detail, according to the image reading apparatus of the present invention, a pressing force corresponding to the thickness of the document can be obtained, so that a high-quality image without image blur can be obtained. Furthermore, since the pressing pressure can be relatively low in the state before document loading, which has the highest torque load, an inexpensive motor with low torque can be used in the drive system.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of a first embodiment of an image reading device of the present invention.

FIG. 2 is a schematic side view of a second embodiment of the image reading device of the present invention.

FIG. 3 is a characteristic diagram showing the relationship between the pressing force and document thickness by the image reading device of the present invention.

FIG. 4 is a schematic side view showing the configuration of a conventional image reading device.

FIG. 5 is a schematic perspective view showing the configuration of a conventional image reading device.

[Explanation of symbols]

1 Photoelectric conversion section 2　Submitted manuscript 3 Back roller 4 Spring 5 Spring 6 Spring 7 Screw

Claims (1)

[Claims] 1. An image reading device that presses a document against a photoelectric conversion unit by a back roller and also sends the document by rotating the back roller, comprising: a first pressing means for applying pressure to the back roller; and a second pressing means that applies pressure to the back roller in addition to the pressure exerted by the first pressing means when the back roller is lifted above a certain value with respect to the photoelectric conversion unit. Device.