JPH02252355A - Image input device - Google Patents

Abstract

PURPOSE:To make change of the constitution of a device and addition of parts entirely unnecessary and to miniaturize the whole device sufficiently by incorporating a bias light guiding means to guide light to an image sensor as one body in the internal part of an imaging lens array element. CONSTITUTION:In a lens array 4, plural pieces of rod lenses 4A with such refractive index distribution that a refraction index in a sectional area is maximum at a central axis and decreases gradually parabolically in a radial direction toward the outer circumference are arranged in parallel with each other at their central axes, and they are united into jointed integral construction by holding the circumference by a holding plate 4B and spacer member 4C and filling an adhesive 4D in a void part. Further, optical fiber 4E not having imaging action is arranged additionally in the void part between the lenses 4A, and is jointed into one body together with the lenses 4A. By using such the array 4, light not contributing to the image formation of the lenses 4A among illumination light reflected by the surface of an original 1 is conducted by an optical fiber 4E group, and is diffused and emitted from an end part so that the image sensor 5 is irradiated uniformly, and it acts as bias light 8 for improving the sensitivity of the sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image input device, and more particularly to an improvement in an optical system for uniformly applying bias light when an image sensor reads a document.

[Conventional technology]

In an image input device using a contact image sensor such as a facsimile, the sensitivity of the sensor becomes extremely poor when the amount of light is small.

To compensate for this, we increase the overall light intensity by covering the original image light intensity with uniform light, and use it at a brightness that provides good sensor sensitivity.

Unlike the photosensitive drum of a copying machine, a sensor treats it as an electrical signal, so by applying a bias, it is possible to remove light signals other than the image light amount.

In order to input a good image, the key is to uniformly apply light that is not involved in image formation (hereinafter referred to as bias light) to the sensor.
No. 60 proposes a configuration in which a light reflecting plate is provided near the original document almost parallel to the original surface, a window is provided on the outer periphery of the imaging optical system, and the light reflected by the reflecting plate is used as the aforementioned bias light. ing.

Furthermore, Japanese Patent Application Laid-Open No. 178658/1983 proposes a configuration in which a light guiding means for guiding light from a light source directly to an image sensor is attached in addition to the imaging optical system.

[Problem that the invention seeks to solve]

In the configuration disclosed in JP-A-63-182960, it is difficult to maintain a constant gap between the imaging optical system and the surrounding frame, and there is a problem that the bias light does not uniformly illuminate the document surface.

Additionally, since there is a gap, there is also the problem that paper dust from feeding the document can adhere to the sensor.

On the other hand, in the configuration of JP-A-63-178658, since the side leakage light of the light source lamp is used as the bias light, it is difficult to keep the illuminance of the document constant and also keep the bias light constant. There is a problem.

Furthermore, in any of the above configurations, it is necessary to provide a reflecting mirror or some kind of light guide, which increases the production cost and has the disadvantage that it becomes difficult to miniaturize the image input device.

[Means for solving the problem] Image input in which an image of a document surface illuminated by a light source is formed on an image sensor via a rod lens array formed by arranging and joining a large number of rod lenses. In the apparatus, by arranging optical fibers that do not have an image forming function between the rod lenses, or (and) by using a transparent adhesive to bond the rod lenses, the illumination reflected light from the document surface is reduced. is guided to the image sensor as bias light.

[For production]

According to the above configuration, the reflected light from the document surface hits the image sensor with uniform illuminance through the optical fiber or adhesive layer between the lenses, and acts as bias light to increase the sensitivity of the image sensor.

In addition, the bias guiding light section is arranged around the imaging lens and is integrated as a lens array element, so it can be simply installed in place of the conventional lens array without changing the specifications of the device. , it is possible to improve the sensitivity of the image sensor.

〔Example〕

The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, in which 1 is a document surface, 2 is a platen, and 3 is an LE as a light source.
D, 4 is a rod lens array, and 5 is an image sensor. The gap between the rod lens array 4 and the housing 6 is filled with a filler 7 such as adhesive or sponge to block light and seal it, thereby preventing dust from adhering to the surface of the image sensor 5.

As shown in FIG. 2, the lens array 4 includes a large number of rod lenses 4A having a refractive index distribution in which the refractive index in the cross section is maximum on the central axis and gradually decreases unevenly in the radial direction toward the outer circumference. They are arranged with their central axes parallel to each other, the periphery is held by a retaining plate 4B and a spacer member 4C, and the gap is filled with an adhesive 4D to form a structure in which they are joined together.

Rod lens arrays having the above structure have conventionally been used as optical systems for copying machines, optical printers, facsimile machines, etc., but in the present invention, optical fibers that do not have an image forming effect are used in the gaps between the lenses 4A. 4E is additionally arranged, lens 4A
They are joined together and fixed together.

By using the lens array with the above structure as the lens array 4 in FIG. The light is diffused and emitted to uniformly illuminate the image sensor 5, and acts as the bias light 8 for improving the sensor sensitivity described above.

Instead of providing the optical fiber 4E for guiding bias light as in the embodiments described above, a transparent adhesive may be used as the adhesive 4D for bonding the lenses 4A together. Of course,
The optical fiber 4E and a transparent adhesive may be used together.

〔Effect of the invention〕

According to the present invention, since the bias guiding light means for the image sensor is integrated inside the imaging lens array element, there is no need to change the structure of the device or add any parts, and it can be manufactured at low cost. At the same time, the entire device can be sufficiently miniaturized. Furthermore, since the illumination light is diffused and emitted at a position sufficiently close to the lens, uniform bias light can be obtained.

Furthermore, since the area around the image sensor can be completely sealed, there is no dust adhering to the sensor, and stable performance can be maintained over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a front view showing an example of a rod lens array element used in the present invention. l... Original surface 2... Platen 3... Light source 4... Rod lens array element 4A...
Rod lens 4B... Holding plate 4C... Spacer 4D... Adhesive 4E... Optical fiber 5.
...Image sensor-6...Housing 7...
Light-shielding filler 8...bias light '21Fi6A,',E:!

Claims (1)

[Scope of Claim] An image input device configured to form an image of a document surface illuminated by a light source on an image sensor through a rod lens array formed by arranging and bonding a large number of rod lenses, comprising the steps of: By arranging optical fibers that do not have an imaging function between the lenses, or (and) by using a transparent adhesive to bond the rod lenses together, the illumination reflected light from the document surface can be imaged as bias light. An image input device characterized by being guided to a sensor.