JPH0331839A - Picture reader - Google Patents

Abstract

PURPOSE:To prevent the blooming phenomenon of a photoelectric conversion element by using a diffusing member attachably and detachably arranged in a optical path according to the level of the reflectivity of an original. CONSTITUTION:The reflectivity of a part 6 to be read, placed on the surface of a original platen 8 is measured by a reflectivity detecting means 9. When the part 6 to be read of a high reflectivity is read based on an output signal from the means 9, the diffusing member 7 is inserted between the part 6 to be read and the original platen 8. Then, the part 6 to be read is irradiated with diffusing light and illumination effect is positively lowered. Thus, the quantity of light which is made incident on the surface of a picture reading means 4 by a projecting lens 3 is decreased, and the photoelectric conversion element is prevented from blooming. Moreover, an incident angle from a light source 1 to the part 6 to be read is set to be <=40 deg., and it is eliminated that normal reflection light from the part 6 to be read is made incident on the means 4, whereby reading precision is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an image reading device, and in particular, the present invention relates to an image reading device, and in particular, in addition to an ordinary document on a sheet, a reflective type with a metallic luster and high reflectance, for example, a document on a sheet can be read. The present invention relates to an image reading device suitable for projecting a document or a three-dimensional object book as a reading image onto an image reading means made of a CCD or the like using a projection lens and reading the projected image.

(Prior art) Conventionally, li! Various image reading apparatuses have been proposed in which a reflective image illuminated by an illumination means is projected onto the surface of an image reading means such as a CCD using a projection lens, and the projected image is read.

FIG. 5 is a schematic cross-sectional view of a main part of a conventional image reading device of this type.

In the figure, reference numeral 52 denotes a part to be read, which is, for example, an original with metallic luster or a three-dimensional object with high reflectivity, and is placed on the surface of the original platen 51. 54 is a concave mirror that condenses the light beam from the light source 53 to improve illumination efficiency and direct it onto the surface of the document table 51.
The part to be read 52 which is M is illuminated.

Reference numeral 55 denotes a projection lens which projects the portion to be read 52 onto the surface of an image reading means 56 comprising a CCD or the like. 57 is an output signal based on image information of the portion to be read 52 obtained from the image reading means 56.

(Problems to be Solved by the Invention) In conventional image reading devices, since the reflectance of the sheet-like original, which is most often used as the part to be read, is relatively low, the image reading device uses illumination means to place the original on the original platen. The area to be read is illuminated as efficiently as possible.

For this reason, when reading a precious metal such as an accessory book on the part to be read that has metallic luster, for example, the light beam from the illumination means is specularly reflected and a large amount of light is incident on the surface of the image reading means. It becomes like this. For this reason, there is a problem in that the photoelectric conversion element of the image reading means 5 exceeds the saturation level, causing a blooming phenomenon and turning the image signal into white noise.

On the other hand, it is possible to reduce the illumination efficiency of the illumination means and, for example, illuminate the original at an angle of incidence of 40 degrees or more to prevent specular reflection. However, there was a problem in that the F number of the projection lens had to be made brighter, making the lens configuration more complicated.

It is also conceivable to set the usage level of, for example, a CCD as this local electric conversion element to 30% or less of the 8 sum output, and to take 70% as a margin for specularly reflected light when a reading area with high reflectance is used. However, with this method, when reading the most common originals, the output signal becomes too small and S
There is a problem that the /N ratio decreases.

The present invention enables any kind of image information to be captured by removably arranging a diffusion member in a predetermined optical path, regardless of whether the original has a low reflectance or a high reflectance with metallic luster. An object of the present invention is to provide an image reading device that can always read image information with high accuracy even if there is a problem.

(Means for Solving the Problems) The image reading device of the present invention illuminates a portion to be read placed a on a document table surface from diagonally below with an illumination means, and illuminates the portion to be read with a projection lens onto the surface of the image reading means. When reading by projecting onto
Note: A diffusion member is inserted and removed between the part to be read and the illumination means according to the reflectance of the part to be read, and the part to be read is illuminated and read through the diffusion member. It is characterized by

Particularly, in the present invention, the illumination means illuminates the part to be read at an incident angle of 40 degrees or less with respect to the document table, and the diffusion member is made of a member having a transmittance of 80% or more. It is characterized by the presence of

(Embodiment) FIG. 1 is a schematic diagram of main parts of an embodiment of an image reading apparatus of the present invention.

In the same figure, reference numeral 6 denotes a part to be read (original), and the original has a high reflectance, and the figure shows a case of a four-piece precious metal having metallic luster and exclusively used as an accessory.

Reference numeral 8 denotes a document table, which supports the portion to be read 6 and is movable in the direction of arrow 8a. Reference numeral 7 denotes a diffusion member, which is arranged so as to be insertable and removable between the portion to be read 6 and the document table 8 . Reference numeral 2 denotes a concave mirror which condenses the light beam from the light source 1 and illuminates the part 6 to be read placed on the surface of the document table 8 from below at an incident angle of 40 degrees or less with respect to the surface of the document table 8. . Reference numeral 3 denotes a projection lens which projects the portion to be read 6 on the surface of the document table 8 onto the surface of the image reader 1I94 at a predetermined magnification.

The image reading means 4 is a CC in which a plurality of elements are arranged one-dimensionally.
It consists of a D-type photoelectric conversion element, and the image information on the surface of the reading section 6 is sequentially scanned and read by moving the document table 8. Incidentally, the image reading means 4 may be composed of a two-dimensional CCD, and in this case, the document table 8! It's fine to leave it fixed.

Reference numeral 9 is a reflectance detection T: stage, which is provided near the document table 8 as necessary, and serves as a light emitting part and a light receiving part.
The diagonal Q41 of the portion to be read 6 placed on the surface 1-1 of the document table 8 is measured.

In this embodiment, when reading the part to be read 6 having a high anti-fJ4 ratio, the reading part 6 is automatically read based on the output signal from the reflectance detection means 9 or based on the input signal 9 from an external input means (not shown). 7 is inserted between the part to be read 6 and the document table 8.

Incidentally, FIG. 2 shows the diffusion member 7 inserted between the document table 8 and the read section 6 (not shown) at this time.

And read! IS6 is illuminated with expanded light to dramatically reduce lighting efficiency. This allows the projection lens 3 to reduce the amount of charge incident on the surface of the image reading means 4.
Blooming of the j1 element is prevented.

In addition, in this embodiment, the angle of incidence of the light beam from the light source 1 on the reading section 6 is set to be 40 degrees or more, so that the specularly reflected light from the reading section 6 does not enter the image reading means 4. Improves reading accuracy.

In this embodiment, when the read part 6 has a low reflectance of a normal sheet-like document register, the read area 6 automatically detects the output signal based on the output signal from the reflectance detection means 9 or from the external input means. Based on this, the diffusion member 7 is removed from between the portion to be read 6 and the document table 8. Thereby, the part to be read 6 is efficiently illuminated with the light beam from the light source 1.

In this embodiment, by inserting and removing the diffusion member from the optical path according to the reflectance of the part to be read, it is possible to read a single document regardless of the reflectance of the part to be read. This allows for accurate reading.

At this time, in this embodiment, the first image reading stage 4 is composed of a CCD, and a white original (an ordinary sheet-shaped original) is placed on the original table 8, and when the reading signal is saturated. level 3
111I! The valley elements are set as described above, and the blooming phenomenon of the photoelectric conversion element is prevented from occurring, so that only highly accurate image fR reading can be performed.

In this embodiment, a material having a transmittance of 80% or more is used as the diffusing member, so that the amount of blurring is small even when the original is lifted, and reading can be performed with high accuracy.

The diffusion member is not limited to between the part to be read 6 and the original HA table 8, but may be placed at any position in the optical path, such as below the document table 8.

As shown in No. 314, the diffusion member 7 is placed on the document table 8.
The FX
The manuscript table 8 may be made to have a movable IJT function, and may be driven and selectively used in accordance with the reflectance of the portion to be read.

In addition, as shown in FIG. 4, two concave surfaces #12a and 2b are used to illuminate the document table 8 so that the angle of incidence of the light beam from the light source 1 on the document table 8 is 40 degrees or less. It is also possible to illuminate from both sides.

(Effects of the Invention) According to the present invention, the diffuser +4 is arranged so that it can be inserted into and removed from the optical path according to the magnitude of the reflectance, regardless of the reflectance of the part to be read. Accordingly, it is possible to prevent the blooming phenomenon of the charging conversion element-r and to achieve an image reading device capable of highly accurate image reading.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the main parts of one embodiment of the present invention, and FIG.
3 is a schematic diagram of another embodiment near the document table in FIG. 1, FIG. 4 is a schematic diagram of a main part of another embodiment of the present invention, and FIG. 1 is a schematic diagram of a conventional image reading device. In the figure, 1 is a light source, 2 is a concave mirror, 3 is a projection lens, 4 is an image reading means, 6 is a part to be read, 7 is a diffusion member, 8 is a document table,
9 is a reflection is detection-L stage.

Claims (5)

[Claims] (1) When the part to be read placed on the document table is illuminated diagonally from below by the illumination means and the part to be read is projected onto the surface of the image reading means by the projection lens and read, the reflectance of the part to be read is An image reading device characterized in that a diffusion member is inserted and removed between the part to be read and the illumination means in accordance with the above, and the part to be read is illuminated and read via the diffusion member. (2) The diffusion member is configured to be insertable and removable based on a signal from a reflectance detection means for detecting the reflectance of a portion to be read provided near the document table or based on a signal from an external input means. The image reading device according to claim 1, characterized in that: (3) The image reading device according to claim 1, wherein the illumination means illuminates the portion to be read at an incident angle of 40 degrees or less with respect to the document table. (4) The image reading device according to claim 1, wherein the diffusion member is made of a member having a transmittance of 80% or more. (5) The image reading means is constituted by a CCD, and each element is set so that the reading signal is 30% or more of the saturation level when the portion to be read is a white original. Image reading means.