JPH09102851A - Original width detecting mechanism in original reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the width of an original which is set without using an exclusive photoelectric sensor for discriminating an original size with high resolution. SOLUTION: The surface of the original 4 is illuminated by an illumination optical system 3, a reflection light image on the original surface is formed in an image sensor 7 by image pickup optical systems 5a to 5c and 6 and the image on the original surface is read in an original reading device. In the device, a back surface reflecting plate 8 with a sufficiently high reflectivity is arranged by position relation so as to be projected from an original side end to the rear side of the original 4 and difference between a reflection level on the original surface and the reflection level on the back surface reflection plate 8 which is protruded from the original side end is discriminated so that the width of the original 4 which is set at the reading position is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading device for photoelectrically reading an image of a document such as a document or a drawing,
In particular, it relates to a document width detection mechanism for recognizing the size of a document set at the reading position.

[0002]

2. Description of the Related Art As is well known, many recent facsimile machines, digital copying machines, electronic file systems and the like include a document reading device having the following basic structure. A manuscript table made of a transparent glass plate is horizontally arranged, a hinged document cover is attached on the manuscript table, and an illumination optical system and an imaging optical system are installed inside the device under the manuscript table. -Various components such as image sensors are installed.

Normal document reading devices include B5, B4, A4,
Handles various size originals such as A3. A document position marker that indicates at which position and direction the document of each size is set is printed around the platen. The document is set on the document table with the side to be scanned down and the document cover is closed, and the document cover is activated. Then, the lower surface of the document is illuminated by the illumination optical system, and the reflected light image of the document is formed on the image sensor by the imaging optical system. Generally, the illumination optical system linearly illuminates the original, and the imaging optical system forms a linear image of the original on the one-dimensional image sensor. Image scanning by this image sensor is called main scanning. There is a mechanism for relatively moving the document and the reading mechanism in the direction orthogonal to the main scanning, which is called sub-scanning. The image of the original is surface-scanned and read by a combination of main scanning and sub-scanning.

Further, many document reading devices are provided with a detection mechanism for recognizing the size of a document set on a document table before reading an image. In the conventional document size detecting mechanism, a plurality of reflection type photoelectric sensors are arranged at required places under the document table. Each photoelectric sensor spot-wise detects whether or not there is a document directly above the arrangement position. As described above, the document position marker is provided around the document table, and the document of each size is set at a predetermined position according to the marker. On the premise of this, the arrangement relationship of the sensors is determined so that the size of the document set on the document table can be discriminated by the outputs of the plurality of photoelectric sensors.

[0005]

As described above, the conventional document size detecting mechanism has a problem that the cost is high because it has a structure using a plurality of photoelectric sensors dedicated to the mechanism. In particular, in a document reading apparatus in which there are many types of document sizes to be discriminated, it is necessary to increase the number of photoelectric sensors for detecting the document size, which increases the cost.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to detect the width of an original set with high resolution without using a dedicated photoelectric sensor for discriminating the original size. An object of the present invention is to provide a document width detecting mechanism.

[0007]

Therefore, according to the present invention, a document is read by illuminating the surface of the document with an illumination optical system and forming a reflected light image of the document surface by an image pickup optical system on an image sensor to read the image on the document surface. In the reading device, a rear reflector having a sufficiently high reflectance is arranged on the back side of the original document so as to extend beyond the edge of the original document, and the front surface of the original document is processed by an image signal processing system that processes the output of the image sensor. The width of the document set at the reading position is detected by discriminating the difference between the reflection level of the document and the reflection level of the back reflector protruding from the end of the document.

In this document width detecting mechanism, a mirror can be used as the back reflector. Further, the illumination optical system and the image pickup optical system are disposed under a transparent document table, and there is a document cover that covers the document table in an openable and closable manner. It is possible to adopt a configuration in which the plates are integrally arranged. Further, the back reflector may be an inclined surface or a curved surface that reflects the light from the illumination optical system and guides it to the imaging optical system with high efficiency, instead of a plane parallel to the original.

[0009]

1 and 2 show the structure of the main part of a document reading apparatus including a document width detecting mechanism according to an embodiment of the present invention.
Is shown in A manuscript table 1 made of a transparent glass plate is horizontally arranged, a hinge opening / closing manuscript cover 2 is mounted on the manuscript table 1, and an illumination optical system and an imaging optical system are provided inside the device under the manuscript table 1. Various components such as a system and an image sensor are arranged.

In the illustrated example, a linear lamp 3 is used as an illumination optical system.
Is shown. The slit-shaped illuminating light emitted from here passes through the document table 1 and is applied to the lower surface of the document 4 set thereon. The imaging optical system includes mirrors 5a, 5b, 5c, a lens 6, and the like. The reflected light from the original 4 illuminated by the light from the lamp 3 is captured, and the linear reflected light image is captured by the one-dimensional image sensor 7 Image on.

FIG. 2 shows a state in which the original 4 and the original cover 2 are viewed from the lower surface side of the original table 1. Main scanning by the one-dimensional image sensor 7 is performed in the direction of the short side of the document table 1,
Sub-scanning is performed by moving the illumination optical system, the imaging optical system, the image sensor, and the like in the long side direction of the document table 1.
Since the principle of reading the image of the original 4 by the main scanning and the sub-scanning is well known, it will not be described here.

In carrying out the document width detecting mechanism of the present invention, a back reflector 8 is integrally provided on the lower surface side of the document cover 2. The back reflector 8 of this embodiment is composed of a strip-shaped elongated mirror, and the back reflector 8 is closed when the cover 2 is closed.
Is parallel to the short side direction of the document table 1, and even when a normal document 4 is set on the document table 1, when viewed from the lower surface side of the document table 1, both side edges of the document 4 are reflected from the rear reflectors. 8 is protruding. Further, in this embodiment, the rear reflector 8 is not parallel to the document table 1 with the cover 2 closed,
It is arranged so as to be inclined at an appropriate angle. With these configurations, the illumination light from the linear lamp 3 is reflected by the back reflector 8.
When reflected by, the reflected light is received by the image sensor 7 via the imaging optical system with extremely high efficiency.

As a result, when viewed as an input image of the image sensor 8, the reflection level of the rear reflector 8 is clearer than the reflection level of the original 4 even when the original 4 having a flat gloss is set. Get higher Therefore, FIG.
As shown in FIG. 5, the output of the image sensor 8 is level-discriminated by an appropriate threshold value Vs (a level slightly lower than the reflection level of the back reflector 8), so that the time information Tw proportional to the width of the document 4 is easily extracted. be able to. The process of extracting the document width information Tw is extremely easy in terms of software or hardware as a simple additional work of a system for processing an image signal from the image sensor 8 (that is, an image processor for reading a document image). Can be implemented. Therefore, it will not be described in further detail herein.

It is possible to easily recognize what the size (B5, B4, A4, A3, etc.) of the document 4 set from the document width information Tw is. Further, unlike the prior art, since the document width can be detected with a considerably high resolution, not only can the types of standardized document sizes be distinguished, but also the width of an irregular-sized document can be recognized.

[0015]

According to the present invention, a back reflector is placed on the back side of a document and an image signal processing system for processing the output of an image sensor that reads the image of the document is used to reflect the reflection level of the document front and the back reflector. The original width can be detected with high resolution by discriminating the reflection level from the level. Therefore, the dedicated photoelectric sensor for detecting the document size is completely unnecessary as in the conventional case, and therefore the cost can be considerably reduced as compared with the conventional case. In particular, the effect of the present invention that the original width detection mechanism becomes cheaper becomes more remarkable as the original reading device has more types of original sizes that must be distinguished. Further, the original width can be detected with a high resolution, which is impossible with the conventional photoelectric sensor for detecting the original size.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a document reading device including a document width detection mechanism according to an embodiment of the present invention.

FIG. 2 is a diagram showing a state in which a document 4 and a document cover 2 are viewed from a lower surface side of a document table 1 in the above embodiment.

FIG. 3 is a principle diagram for detecting the document width from the output of the image sensor 8 in the same embodiment.

[Explanation of symbols]

 1 Original Plate 2 Original Cover 3 Linear Lamp 4 Originals 5a, 5b, 5c Mirror 6 Lens 7 Image Sensor 8 Rear Reflector

Claims (4)

[Claims] 1. A document reading apparatus for illuminating the surface of a document with an illumination optical system and for reading the image on the document surface by forming a reflected light image of the document surface on an image sensor by an imaging optical system to read the image on the document surface. A high back reflector is arranged on the back side of the original document in such a positional relationship as to protrude from the edge of the original document, and an image signal processing system that processes the output of the image sensor projects the reflection level on the original document surface and the edge of the original document. A document width detecting mechanism in a document reading device, wherein the width of a document set at a reading position is detected by discriminating a difference from the reflection level of the back reflector. 2. The document width detection mechanism in a document reading device according to claim 1, wherein the back reflector is a mirror. 3. The illumination optical system and the image pickup optical system according to claim 1 or 2, wherein the illumination optical system and the imaging optical system are arranged under a transparent document table, and a document cover that covers the document table in an openable and closable manner is provided. A document width detecting mechanism in a document reading device, wherein the back reflector is integrally provided on a lower surface portion of the document cover. 4. The method according to claim 1, 2 or 3.
In the above document, the back reflector is not a plane parallel to the original, but is an inclined surface or a curved surface that reflects the light from the illumination optical system and guides it to the imaging optical system with high efficiency. Document width detection mechanism in the reading device.