JP2002010028A - Light source unit for original reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source unit for an original reader capable of preventing a shade at an end of an original or an end of a cut and adhered part and being reduced in size. SOLUTION: The light source unit 21 for the original reader comprises a light source 22 disposed directly under a reading line of the original A to radiate a light from a perpendicular direction to the line, and a half-mirror 23 disposed obliquely in an optical path between the source 22 and the line to pass a light from the source 22 to radiate the light to the line and reflect a reflected light from the original A in a predetermined direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light source unit for a document reading device.

[0002]

2. Description of the Related Art Document reading apparatuses are used in various apparatuses for handling document documents or image documents, such as copying machines and image input devices.

There are two types of document reading apparatuses: a flat bed type in which a document is fixed and a part of a reading unit moves, and a sheet feed type in which a reading unit is fixed and a document moves.

FIG. 7 shows an example of a conventional flatbed type document reading apparatus.

The original reading device (1) is arranged below a horizontal original table (2) made of platen glass, and comprises a first scanning unit (3) and a second scanning unit (4) constituting a light source unit. ), An imaging optical lens (5), and a CCD (Charge Coupled Device) (6) as a photoelectric conversion element.
The direction perpendicular to the plane of FIG. 7 is the main scanning direction, and the direction from left to right in FIG. 7 is the sub-scanning direction. Scanning unit (3) (4)
Is supported by a casing of the document reading device (1) (not shown) so as to be able to reciprocate within a predetermined range in the sub-scanning direction in a sub-scanning direction and a return direction opposite thereto. First scanning unit (3)
Scans the document (A) placed on the document table (2) while moving at a constant speed in the sub-scanning direction. Second scanning unit (4)
Moves in the sub-scanning direction with a constant speed relationship with the first scanning unit (3). The lens (5) and the CCD (6) are fixed to the housing of the document reading device (1).

The first scanning unit (3) includes a lamp (7) as a light source for irradiating the document (A) on the document table (2), and a document (A).
A first mirror (8) for reflecting the reflected light image toward the second scanning unit (4) to guide the reflected light image from the CCD to the CCD (6) is mounted. The second scanning unit (4) includes a second mirror (9) for reflecting the reflected light image toward the lens (5) and guiding the reflected light image from the first mirror (8) to the CCD (6). A third mirror (10) is mounted. Lens (5) is the third
This is for forming an image of the reflected light from the mirror (10) on the CCD (6). The CCD (6) constitutes a photosensitive light receiving means for converting a reflected light image from the document (A) into an electric image signal. The lamp (7), the mirrors (8), (9), (10), the lens (5), and the CCD (6) extend in the main scanning direction corresponding to the width of the document (A).

The lamp (7) is arranged below the reading line of the document (A) on the right side (downstream in the sub-scanning direction) and irradiates the reading line diagonally from the lower right. The first mirror (8) is disposed immediately below the reading line. In order to prevent a reflected light image of a portion other than the reading line from being incident on the first mirror (8), a slit plate (12) having a slit (11) having a predetermined width corresponding to the reading line width is provided. Platen (2) and 1st
It may be located in the optical path between the mirrors (8).

As described above, the first scanning unit (3) moves in the sub-scanning direction to scan the original (A), thereby
The image of (A) is formed on the CCD (6) one read line at a time and read, and image data is obtained.

In the above document reading apparatus (1), since the lamp (7) irradiates the reading line of the document from obliquely below, the thickness of the document and the cut and pasted portion are attached to the end of the document and the end of the cut and pasted portion. There is a problem that a shadow corresponding to the step is generated and is read as a black image.

Therefore, as shown by a chain line in FIG.
A reflector (13) is provided on the scanning unit (3) on the opposite side of the lamp (7), and a part of the light from the lamp (7) is reflected by the reflector (13) so that the light is reflected from the opposite side of the lamp (7). There is one that irradiates a reading line.

However, even in this case, the optical path length of the light emitted from the reflector (13) to the reading line is longer than the optical path of the light emitted from the lamp (7) directly to the reading line.
Since the reflectivity of the reflector (13) is not 100%, etc., a difference in the amount of light occurs between the reflected light from the reflector (13) and the direct light from the lamp (7). It is not possible to completely prevent the occurrence of.

Therefore, various proposals have been made as follows.

First, Japanese Patent Application Laid-Open No. 4-273657 proposes the following light source unit for a document reading apparatus. That is, the light source unit for the document reading device is
As in the case of FIG. 7, a long fluorescent lamp and a reflector are provided. The lamp has a portion where a phosphor is applied to a glass tube and an aperture where the phosphor is not applied. The aperture of the lamp is arranged so as to be deflected from the document surface side in the direction of the reflector, and the aperture portion with respect to the document surface so that the amount of direct light from the lamp and the amount of reflected light at the reading portion of the document surface are substantially equal. Set the direction of. The reflector is disposed downstream (reading end side) of the document in the sub-scanning direction with respect to the lamp, and the document surface between the lamp and the reflector serves as a reading portion.

Japanese Patent Application Laid-Open No. 4-323951 proposes the following light source unit for a document reading apparatus. That is, two tubular light sources long in the main scanning direction are provided before and after the reading line of the document in the sub scanning direction. Providing a long solid-state light-transmitting portion in the main scanning direction that transmits the illumination light beam condensed from the opening of the tubular light source toward the reading line of the document, and forming the light-shielding portion on the side surface of the solid light-transmitting portion This allows the light-shielding portion to block light other than the illuminating light flux condensed from the opening of the tubular light source toward the reading line without being affected by mechanical vibrations or the heat of the tubular light source, and correct the information of the document. The reading can be performed over a long period of time.

Further, Japanese Patent Application Laid-Open No. 5-72641 proposes the following document reading apparatus. In other words, the document reading device includes an illumination light source that is disposed immediately below a reading line of a document placed on a document table (contact glass) and has directivity directly above, and an illumination light source that irradiates the position of the reading line. A first mirror is disposed obliquely above the illumination light source for guiding the reflected light, and a second mirror and a third mirror for guiding the reflected light of the first mirror to the one-dimensional image sensor.

[0016]

The above-mentioned JP-A-4-27
In the case of the light source unit for a document reading device described in Japanese Patent No. 3657, a reflector is required to split the illumination light into two. Further, since the lamp as the light source and the reflector are arranged in the sub-scanning direction, the size of the light source unit in the same direction increases.

In the case of the light source unit for a document reading apparatus described in Japanese Patent Laid-Open No. 4-323951, the light source is
And a long solid light transmitting portion is required for each light source. Also, since the two light sources are arranged in the sub-scanning direction,
The size of the light source unit in the same direction increases.

In the case of the document reading apparatus described in Japanese Patent Application Laid-Open No. 5-72641, the first mirror is disposed diagonally below the reading line of the document (obliquely above the light source) in the light source unit. In order to correct the shrinkage of the image at the first mirror, the subsequent second mirror, third mirror,
The optical lens for imaging needs to be devised. Further, since the light source and the first mirror are arranged in the sub-scanning direction, the size of the light source unit in the same direction increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light source unit for a document reading apparatus which can solve the above problems and can prevent the occurrence of shadows at the end of a document or at the end of a cut-and-paste portion and can be reduced in size. To provide.

[0020]

According to the present invention, there is provided a light source unit for a document reading apparatus according to the present invention, which is disposed immediately below a reading line of a document and irradiates light to the reading line from a vertical direction, and a light source. A half mirror that is arranged in an inclined manner in the optical path between the scanning line and the reading line, passes light from a light source to irradiate the reading line, and reflects reflected light from a document in a predetermined direction. It is a feature.

A part of the light heading directly upward from the light source is reflected by the half mirror, while the remaining part passes through the half mirror and is irradiated in a direction perpendicular to the reading line of the original. Is reflected. A part of the reflected light passes through the half mirror, while the remaining part is reflected in a predetermined direction by the half mirror, and is reflected on the CCD via the second and third mirrors and the imaging optical lens. It is imaged.

By using a half mirror, a half mirror and a light source are arranged immediately below the reading line of the document, and a part of the light from the light source is radiated from the vertical direction to the reading line of the document. Can be partially reflected and guided in a predetermined direction. Since the light from the light source is emitted from the direction perpendicular to the reading line of the original, the shadow corresponding to the thickness of the original or the step of the cut and pasted portion may be present at the end of the original or at the end of the cut and pasted portion attached to the original. Does not occur, and the disadvantage that the shadow portion is read as a black image as in the related art is eliminated.

The transmittance of the half mirror is preferably 5
0%. By setting the transmittance of the half mirror to 50%, it is possible to transmit the irradiation light from the light source and reflect the reflection light from the reading line of the original in the half mirror most efficiently. The ratio of the amount of light reflected by the mirror can be maximized. In that case, the above ratio is 25%, but CCD
There is no problem because the performance of the photoelectric conversion element is improved.

Further, only a half mirror is used instead of the conventional first mirror, and there is no need to provide a reflector for dividing light into two or to provide two light sources. Moreover, since the light source and the half mirror are arranged vertically, the size in the sub-scanning direction does not increase, and the size of the light source unit can be reduced.

In the light source unit for a document reading apparatus according to the present invention, for example, a light shielding layer is provided on a half mirror except for a portion having a predetermined width corresponding to the reading line width of the document.

The light-shielding layer is formed, for example, by applying black paint at a predetermined position of the half mirror, leaving a portion having a predetermined width corresponding to the reading line width of the document.

In this case, a portion of the half mirror having a predetermined width where the light shielding layer is not provided serves as a slit in the conventional slit plate. For this reason, it is no longer necessary to provide a slit plate which is conventionally provided as a separate body.

In the above-described light source unit for an original reading apparatus, for example, a light shielding layer is provided on the original-side surface of the half mirror.

In this way, the effect of the slit can be maximized.

In the light source unit for a document reading apparatus according to the present invention, for example, the half mirror comprises a transparent mirror substrate and a half mirror portion provided on the surface of the mirror substrate on the document side.

The mirror substrate is made of, for example, a transparent glass plate.

In the above-described light source unit for a document reading device, for example, the half mirror portion is provided only on a portion of the mirror substrate having a predetermined width corresponding to the reading line width of the document.

In this case, the portion of the mirror substrate on which the half mirror portion is not provided remains transparent, so that only light passes therethrough and does not fulfill the function of the half mirror. For this reason, the half mirror portion provided on the mirror substrate plays the role of a slit in the conventional slit plate.
For this reason, it is no longer necessary to provide a slit plate which is conventionally provided as a separate body. Moreover, there is no need to provide a light-shielding layer made of black paint or the like in order to fulfill the function of the slit.

In the above-described light source unit for a document reading device, for example, the half mirror portion is formed by evaporating aluminum on the surface of the mirror substrate.
Its transmittance is 50%.

In this way, the half mirror portion can be easily formed by vapor deposition of aluminum.
Further, since the transmittance of the half mirror section is 50%, as described above, transmission of the irradiation light from the light source and reflection of the reflected light from the reading line of the document can be performed most efficiently as described above. it can.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a drawing corresponding to FIG. 7 showing a schematic configuration of a document reading apparatus. In FIG. 1, the same parts as those in FIG. 7 are denoted by the same reference numerals in the drawings. In the following description, the left and right sides of the drawing are simply referred to as left and right.

The original reading device (20) includes a light source unit (first
A scanning unit (21), a second scanning unit (4), an imaging optical lens (5), and a CCD (6). The light source unit (21) has a lamp (22) as a light source and a half mirror (2
3) is installed. Lamp (22) and half mirror (2
3) is long in the main scanning direction corresponding to the width of the document (A). The lamp (22) is disposed immediately below the reading line of the document (A), and the half mirror (23) is disposed between the lamp (22) and the reading line. The lamp (22) is provided with a semi-cylindrical reflector (24) that covers a substantially lower half thereof, whereby most of the light from the lamp (22) is irradiated directly upward, Light is applied to the reading line of the document (A) from directly below. The half mirror (23) is
2) is to pass the light from 2) to irradiate the reading line and reflect the reflected light from the original (A) in the direction of the second scanning unit (4).
(4) The right side is arranged with a high inclination so as to face the side. The inclination angle of the half mirror (23) with respect to the document table (2) surface is 45 degrees. The transmittance of the half mirror (23) is 50%. Others are the same as the case of the conventional example of FIG.

In the above document reading apparatus, the lamp (22)
A part of the light going directly upward from is reflected rightward by the half mirror (23), and the remaining part passes through the half mirror (23), and is perpendicular to the reading line of the original (A) from directly below. And is reflected right below. Part of the reflected light from the original (A) passes through the half mirror (23) and goes directly downward, and the remaining part is reflected to the left by the half mirror (23), and the second mirror (9) and the third mirror CC via mirror (10) and lens (5)
An image is formed on D (6).

Since the transmittance of the half mirror (23) is 50%, the transmission of the irradiation light from the lamp (22) and the reflection of the reflected light from the original (A) in the half mirror (23) are performed most efficiently. be able to. At this time, the light source light (lamp (2
The ratio of the final reflected light amount (light amount of light reflected from the half mirror (23) toward the second mirror (4)) by the half mirror (23) to the light amount of light first irradiated from (2)) is 25. %
It is.

FIG. 2 shows the details of the light source unit (21) of FIG. 1, especially the half mirror (23).

In this case, the half mirror (23) comprises a transparent mirror substrate (25) and a half mirror portion (26) provided on the original-side surface, ie, the upper surface of the mirror substrate (25). The mirror substrate (25) is made of, for example, a transparent glass plate. The half mirror part (26) is formed by evaporating aluminum on the surface of the mirror substrate (25). The transmittance of the half mirror portion (26) is 50%, and thereby the transmittance of the entire half mirror (23) is 50%. lamp
Part of the irradiation light from (22) is reflected rightward by the half mirror part (26), and part of the reflection light from the original (A) is reflected by the half mirror part (26) to the second mirror (4). Reflected in the direction.

FIGS. 3, 4 and 5 show a half mirror (2
It is a drawing of FIG. 2 corresponding to three modifications of (3).

In these modifications, the half mirror (2
3) comprises a mirror substrate (25) and a half mirror part (26), as in the case of FIG. And the half mirror (26)
A light-shielding layer (28) is provided on both sides in the width direction except for a slit portion (27) having a predetermined width corresponding to the reading line width of the document (A). The slit portion (27) functions as a slit in a conventional slit plate.

In the example of FIG. 3, the light shielding layer (28) is a mirror substrate.
It is provided on the lower surface of (25). The light shielding layer (28) is formed by, for example, applying an appropriate black coating to the lower surface of the mirror substrate (25) before or after forming the half mirror portion (26) on the mirror substrate (25). In this case, the ramp
The light from (22) passes through only the slit portion (27) of the half mirror (25) corresponding to the reading line of the document (A) and irradiates the reading line.

In the example of FIG. 4, the light shielding layer (28) is a mirror substrate.
(25) and a half mirror section (26). The light-shielding layer (28) is formed, for example, by applying an appropriate black coating on the upper surface of the mirror substrate (25) before forming the half mirror part (26), and thereafter, the light-shielding part (28) and the mirror in between A half mirror portion (26) is formed so as to cover the upper surface of the substrate (25). Also in this case, the light from the lamp (22) is
Then, the light passes through only the slit portion (27) of the half mirror (25) corresponding to the read line and is irradiated on the read line.

In the example shown in FIG. 5, the light shielding layer (28) is provided on the upper surface of the half mirror section (26). The light-shielding layer (28) is formed by forming a half mirror portion (26) on the mirror substrate (25) and then applying an appropriate black coating on the upper surface of the half mirror portion (26), for example. In this case, the light from the lamp (22) passes through the half mirror (25) corresponding to the reading line of the original (A).
Is irradiated on the reading line through only the slit portion (27), and the reflected light from the document (A) is reflected toward the second mirror (4) only at the slit portion (27). Therefore, the slit portion (27) can maximize the effect as a slit.

FIG. 6 is a drawing corresponding to FIG. 2 showing another modification of the half mirror (23).

In this case, the half mirror (23) is composed of a mirror substrate (25) and a half mirror part (26) as in the case of FIG. 2, but the half mirror part (26) is a mirror substrate (25). Are provided only in a portion having a predetermined width corresponding to the reading line width of the original (A). Since the part of the mirror substrate (25) where the half mirror part (26) is not provided remains transparent,
The light only passes through and does not fulfill the function of a half mirror. Then, only the half mirror portion plays the role of the half mirror and the role of the slit in the conventional slit plate.

The configuration of the document reading apparatus is not limited to that of the above embodiment, but can be changed as appropriate. Further, in the above-described embodiment, the flat-bed type document reading device is described, but the present invention can be applied to a sheet feed type document reading device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a document reading apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an enlarged light source unit of the document reading apparatus of FIG. 1;

FIG. 3 is a drawing corresponding to FIG. 2, showing a modified example of the half mirror of the light source unit.

FIG. 4 is a drawing corresponding to FIG. 2, showing another modified example of the half mirror of the light source unit.

FIG. 5 is a drawing corresponding to FIG. 2, showing still another modified example of the half mirror of the light source unit.

FIG. 6 is a drawing corresponding to FIG. 2, showing still another modified example of the half mirror of the light source unit.

FIG. 7 is a drawing corresponding to FIG. 2, showing still another modified example of the half mirror of the light source unit.

[Explanation of symbols]

 (A) Document (20) Document reader (21) Light source unit (22) Lamp (23) Half mirror (25) Mirror substrate (26) Half mirror part (27) Slit part (28) Light shielding layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiro Mizuguchi 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 2H108 AA01 CB01 DA01 DA06 GA02 GA09 JA11 2H109 AA02 AA15 AA23 AA52 AA90 5B047 AA01 BA02 BB02 BC09 BC12 5C072 AA01 BA15 CA09 DA05 DA15 DA21 XA01

Claims (6)

[Claims] A light source that is disposed immediately below a reading line of the document and irradiates light from the reading line in a direction perpendicular to the reading line; and a light from the light source that is disposed obliquely in an optical path between the light source and the reading line. A light source unit for a document reading device, comprising: a half mirror that irradiates light onto a reading line by passing light through the mirror and reflects reflected light from the document in a predetermined direction. 2. The light source unit for a document reading device according to claim 1, wherein a light shielding layer is provided on the half mirror except for a portion having a predetermined width corresponding to a reading line width of the document. 3. The light source unit for a document reading device according to claim 2, wherein the light shielding layer is provided on a surface of the half mirror on the document side. 4. The original reading apparatus according to claim 1, wherein the half mirror comprises a transparent mirror substrate and a half mirror portion provided on the original-side surface of the mirror substrate. Light source unit for equipment. 5. The light source unit for a document reading device according to claim 4, wherein the half mirror portion is provided only on a portion of the mirror substrate having a predetermined width corresponding to a reading line width of the document. 6. The document reading apparatus according to claim 4, wherein the half mirror portion is formed by evaporating aluminum on the surface of the mirror substrate, and has a transmittance of 50%. Light source unit.