JP3144724B2 - Image reading optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading optical apparatus which irradiates a document on which image information is recorded with reading light and reads transmitted light or reflected light by a line sensor.

[0002]

2. Description of the Related Art Conventionally, there has been known an image reading apparatus which photoelectrically reads image information recorded on a document such as a film by a line sensor, performs desired image processing on the image information, and creates a film master for printing and plate making. Widely used.

In the image reading apparatus, when light transmitted or reflected from a document is introduced into each pixel of the line sensor to obtain an electric signal corresponding to image information, the reading light is incident on a portion other than the pixel. In order to prevent the occurrence of flare, for example, a slit member is provided between the light source and the document, and the light irradiation area of the light source is formed in a slit shape in the width direction of the line sensor.

[0004]

However, the reading light that has passed through the gap between the slit members has its numerical aperture in the sub-scanning direction reduced because its emitting direction is narrowed within a predetermined range. The influence of unevenness existing in the upper sub-scanning direction is more likely to appear. As a result, flaws and the like are reproduced in the main scanning direction.

Accordingly, the present applicant has proposed an image reading optical apparatus which can prevent the scratches, dust, irregularities and the like existing on the original document or the glass plate holding the original document from being reproduced. (See Japanese Patent Application No. 4-55357). In Japanese Patent Application No. 4-55357, a long cylindrical lens is disposed between a slit member and a document in the main scanning direction, and the reading light is diverging light to reduce the visibility of scratches and the like. Further, a filter for controlling the light amount distribution of the reading light is further provided between the light source and the document, and the filter has a predetermined dimming characteristic with a predetermined range around the optical axis of the reading light incident on the document. By setting
A technical idea for further reducing the visibility of a flaw or the like in the main scanning direction is disclosed.

The present invention has been made in connection with the above-mentioned proposal, and is intended to make it possible to obtain a good image by making scratches, dust, etc. due to the original document or a glass plate holding the original document inconspicuous. It is an object to provide an optical device.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention illuminates an original with reading light and receives transmitted or reflected light of the original with a line sensor to obtain desired image information. In the image reading optical device, a filter for controlling the light amount distribution of the reading light is provided between a light source for irradiating the reading light and the document on which the image information is recorded, and the filter has a constant width and a constant width. Having a predetermined dimming characteristic disposed in the longitudinal direction of the line sensor at intervals of
And a predetermined width corresponding to a predetermined distance from the first dimming portion and corresponding to a distance between the first dimming portion,
And a second dimming portion having a predetermined dimming characteristic and arranged in a longitudinal direction of the line sensor at regular intervals.

Further, the present invention provides a light source for irradiating a document on which image information is recorded with reading light, a first light condensing means for condensing the reading light in a sub-scanning direction, A second focusing means for focusing the reading light on the document in the sub-scanning direction with the focusing position of the reading light by the focusing means as a front focus, a light source for irradiating the reading light, and recording of image information A filter that controls a light amount distribution of the reading light, a line sensor that receives reading light from the document and converts the light into an electric signal, and is long in a main scanning direction; A third light condensing means disposed between the document and the line sensor for condensing the reading light from the document on the line sensor, wherein the filter is fixed in the sub-scanning direction. With a constant width and constant spacing in the main scanning direction. A first dimming portion having a predetermined dimming characteristic, and a certain width and a certain interval corresponding to a distance between the first dimming portion and the first dimming portion and corresponding to the first dimming portion. And a second dimming portion having predetermined dimming characteristics arranged in the main scanning direction.

[0009]

In the image reading optical device according to the present invention, the reading light emitted from the light source and vertically incident on the filter is:
The light amount is attenuated by passing through the first light-reducing portion or the second light-reducing portion having a predetermined light-reducing characteristic, and is incident on the document. On the other hand, the reading light that enters the filter at an inclination of a predetermined angle enters the document from the gap between the first light-reducing portion and the second light-reducing portion, so that the amount of the reading light may be attenuated. Absent. Therefore, when there is a flaw in the sub-scanning direction of a document or the like, the total amount of light transmitted through the document can be kept constant regardless of whether or not the reading light is refracted by the document or the like. Can be obtained.

Further, in the image reading optical apparatus according to the present invention, the reading light from the light source is condensed by the first condensing means at the front focus of the second condensing means, and then the light quantity at a predetermined angle by the filter. The distribution is controlled, and the light is condensed on the document by the second condensing means. The reading light from the original is further focused on the line sensor by the third focusing means,
Converted to electrical signals.

In this case, the filter has a predetermined width in the sub-scanning direction and a first light-reducing characteristic having predetermined light-reducing characteristics, which is disposed in the main scanning direction at a constant width and at a constant interval. Since it is composed of a light portion, a second light-reducing portion, and a transmission portion other than the first and second light-reducing portions, light amount control is performed in both the main scanning direction and the sub-scanning direction. Therefore, even when there is a flaw or the like in the main scanning direction and the sub-scanning direction of the document, it is possible to prevent a reduction in the total amount of light, and as a result, it is possible to obtain an image with no noticeable flaw or the like.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of an image reading optical apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a view for explaining the principle of an image reading optical apparatus 10 according to this embodiment. The image reading optical device 10 is provided with a light source 12 for irradiating diffused reading light, a document 14 on which image information is recorded, and disposed between the light source 12 and the document 14 in a main scanning direction (arrow A filter 16 formed to be long with respect to the X direction), a reading lens 18 for collecting reading light transmitted through the filter 16, and the reading lens 1.
And a line sensor 20 that receives the light condensed by 8 and converts it into an electric signal.

The filter 16 is formed of a light-transmitting member 22 having a predetermined thickness (A) in a planar shape, for example, transparent glass. On the upper surface of the light transmitting member 22, a first print pattern 24 composed of a plurality of light dimming members, for example, chromium (Cr) is deposited at a predetermined interval (B) in the main scanning direction. . The first print pattern 24 is formed with a width (C) substantially equal to the interval (B) between the first print patterns, and the transmittance thereof is set to about 50%. On the other hand, a second print pattern 25 including a plurality of light attenuating members is deposited on a lower surface of the light transmitting member 22 at a position corresponding to a gap between the first print patterns 24 on the upper surface.

The image reading optical device 10 according to the present embodiment
Basically, the configuration is as described above. Next, the operation and the effect will be described.

The reading light emitted from the light source 12 is guided to a filter 16, and the reading light transmitted through the filter 16 is applied to a document 14, and the reading light transmitted through the document 14 and carrying image information is read by a reading lens. The light condensed by 18 is received by the line sensor 20 and converted into an electric signal to obtain desired image information.

Here, the relationship between the amount of light at an arbitrary point P on the document 14 and the incident angle θ of the reading light is such that when the incident angle θ = 0 °, the transmittance of the filter 16 is 50% (reading light L1, L
2) 25% of the incident angle θ at which the first print pattern 24 and the second print pattern 25 overlap (read light L
3), 100% (read light L
Taking into consideration 4) and shading by the incident angle θ, the result is as shown in FIG.

That is, as shown in FIGS. 3A and 3D, for example, when the incident angle θ of the reading light L5, L6 with respect to the filter 16 is 0 °, any of the reading light L5, L6
Is also 50% at an arbitrary scanning position. Further, as shown in FIGS. 3C and 3F, the angle of incidence is
For example, with the reading light where θ ₁ = arctan (B / A), the transmittance of the reading lights L7 and L8 passing through both the first print pattern 24 and the second print pattern 25 is 25%, and the transmittance of both is 25%. Reading light L9, L that does not transmit any
10 has a transmittance of 100%. In this case, the average transmittance of the reading lights L7 to L10 when the incident angle is θ ₁ is 6
2.5%. Further, when the incident angle θ of the reading light is 0 <θ <
For theta _1, as shown in FIG. 3B and FIG. 3E, the transmittance 25% of the read light L11 passing through the first printed pattern 24 to both of the second print pattern 25, transmitting only the second print pattern 25 The transmittance of the reading light L12 to be transmitted is 50%, and the transmittance of the reading light L13 that does not transmit any of the print patterns is 100%.

As described above, different incident angles (0 to 0)
Based on the transmittance distribution obtained for θ ₁ ) and, as shown in FIG. 4, the luminance characteristics of a normal diffuse light source in which the amount of light decreases as the incident angle θ increases, as shown in FIG. A characteristic curve of the irradiation angle and the light amount can be derived. The characteristic curve shown in FIG. 2 is determined by the thickness (A) of the light transmissive member 22, the width (C) of the first and second print patterns 24 and 25, and the interval (B).

If the numerical aperture of the reading lens 18 is NA (NA∝sin α), and the original 14 is not damaged, as shown in FIGS. 2 and 5A, the reading light in the range A1 is applied to the line sensor 20. It is led to. On the other hand, scratch 2
In the case where there is 6, the light path changes due to the refraction at the flaw 26, and as shown in FIG.
And the reading light of A3 is guided to the line sensor 20. In this case, from the characteristic of FIG. 2, the same amount of light can be guided to the document 14 in the case of FIG. 5A and the case of FIG. 5B. As a result, the reading light less affected by the flaw 26 arrives without reducing the total amount of light received by the line sensor 20, and
Thereby, a good image can be obtained. When the filter 16 according to the present embodiment is not used, as shown in FIG. 4, the luminance characteristic decreases as the irradiation angle θ increases, so that the optical path is refracted at the flaw 26. The amount of light received by the sensor 20 at the time of the change decreases, and a black flaw image is generated.

FIG. 6 shows an image reading optical device 30 in which the filter 16 is incorporated in a Koehler illumination optical system.

The image reading optical device 30 comprises a light source 32 comprising a fluorescent tube and having an aperture 31;
A field lens 38 disposed below the cylindrical lens 34 and having a slit 36, and a field stop 38 disposed below the field lens 38; A filter 16 having first and second print patterns 24 and 25 disposed at a predetermined width (C) and a predetermined interval (B) and having a predetermined length (D) in the sub-scanning direction; A pair of cylindrical lenses (second condensing means) 40a, 40b disposed below the filter 16, and disposed below the cylindrical lenses 40a, 40b and held by supporting glass plates 41a, 41b. An original 42, a reading lens (third condensing means) 44 disposed below the original 42 and collecting transmitted light applied to the original 42, By the lens 44 preparative said read disposed part and a line sensor 46 for converting into an electric signal by receiving light focused. The filter 16 is
The pair of cylindrical lenses 40a and 40b are disposed at front focal positions.

The image reading optical device 30 according to the present embodiment
Basically, the configuration is as described above. Next, the operation and the effect will be described.

The reading light emitted from the light source 32 is condensed in the sub-scanning direction by a cylindrical lens 34, and then passes through a slit 36 of a field stop 38 to filter 16.
It is led to. The reading light introduced into the filter 16 is:
It is introduced into a pair of cylindrical lenses 40a, 40b. The cylindrical lenses 40a and 40b form the image of the slit 36 on the original 42 and converge the reading light on the original 42. The reading light transmitted through the original document 42 is condensed via a reading lens 44 and is sent to a line sensor 46.
The light is collected as linearized light. Therefore, the line sensor 46 performs a main scan of the document 42 conveyed in the sub-scanning direction, converts read light carrying image information into an electric signal,
The image data is transferred as image data to an image processing circuit (not shown) of the image reading apparatus.

In this case, as described with reference to FIGS. 1 to 5, the filter 16 can reduce the visibility of a flaw on the document 42 in the sub-scanning direction. As shown in the characteristics of FIG. 7, the filter 16 is provided with first and second print patterns 24 and 25 having a predetermined length (D) in the sub-scanning direction. , Second print patterns 24 and 25 and the first and second print patterns 2
Since the control of the light amount in the sub-scanning direction is performed between the transmission portions other than 4 and 25, the visibility of the flaw in the main scanning direction can be reduced.

Next, a filter 50 according to another embodiment is shown in FIG. In this filter 50, spacers 54a and 54b are interposed at the ends of two transparent glass plates 52a and 52b, and chrome (Cr) having a predetermined width (C) is provided on opposing inner surfaces of the glass plates 52a and 52b. ) Are deposited at a predetermined interval (B) to form a first print pattern 56 and a second print pattern 57, respectively.
By making the inside hollow, a light transmitting member is obtained. In this case, there is no risk of dust entering between the glass plates 52a and 52b.
The effect that cleaning of the outer surface of 2b becomes easy can be obtained.

FIGS. 9 and 10 show a filter 60 according to another embodiment. The filter 60 includes a cylindrical aluminum pipe (light non-transmissive member) 64 having a slit 62 defined in a longitudinal direction, and a circle that is inserted into the aluminum pipe 64 and that introduces light from a light source 66. A columnar quartz glass body (introducing member) 68 and a substantially same light-attenuating member having a predetermined width (C) in the longitudinal direction of the outer peripheral surface of the glass body 68 are provided at the same interval (B) as the predetermined width (C). ), A plurality of first print turns 70 spaced apart from each other,
Glass body 68 facing first print pattern 70
Are formed substantially identically on the outer peripheral surface of the first printed pattern 7.
The second print pattern 71 corresponds to the position of 0 and the position of the interval (B). When the glass body 68 is inserted into the aluminum pipe 64, the second print pattern 71 is arranged at the slit 62. A diffusion paint layer (not shown) for diffusing light is attached to the inner wall surface of the aluminum pipe 64. Instead of the glass body 68, the inside of the aluminum pipe 64 is hollow, the first print pattern 70 is formed on the inner wall surface, and the second is formed in the slit 62 through an acrylic plate or the like.
The print pattern 71 may be formed.

The operation and effect of the filter 60 constructed as described above will be described below.

The reading light emitted from the light source 66 disposed near one end of the glass body 68 is introduced into the aluminum pipe 64 through the glass body 68. The reading light introduced into the aluminum pipe 64 is reflected by the diffusion paint layer provided on the inner wall surface of the aluminum pipe 64, and the reading light is scattered. In this case, the reading light L14 reflected at a portion other than the first print pattern 70 and scattered without transmitting through the second print pattern 71 is emitted to the outside of the filter 60 without being reduced. On the other hand, the reading light L15 that is reflected by the first print pattern 70 and does not pass through the second print pattern 71 and the reading light L16 that passes through the second print pattern 71 have their light amounts attenuated and are outside the filter 60. Injected into. Thus, the same characteristics as in FIG. 2 can be obtained with the read light that is dimmed and the read light that is not dimmed.

In this embodiment, the transmission type originals 14 and 42 have been described, but it is a matter of course that a reflection type original may be used.

[0031]

According to the image reading optical apparatus of the present invention, the following effects can be obtained.

That is, the amount of the reading light incident on the document is controlled by the angle, and the reading light is guided to the line sensor via the light condensing means having a numerical aperture corresponding to the angle, so that the sub-scanning direction of the document and the And / or scratches in the main scanning direction can be made inconspicuous.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of an image reading optical device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a relationship between a light amount of light incident on a document and an irradiation angle.

FIG. 3 is an explanatory diagram showing a relationship between an incident angle of reading light incident on a filter and transmittance.

FIG. 4 is an explanatory diagram showing luminance characteristics of a normal diffuse light source.

FIG. 5A is an explanatory diagram showing an operation of a filter when there is no flaw on an original, and FIG.

FIG. 6 is a configuration diagram illustrating an image reading optical device according to an embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating a relationship between a light amount and an irradiation angle with respect to a sub-scanning direction.

FIG. 8 is a sectional view of a filter according to another embodiment.

FIG. 9 is an exploded perspective view of a filter according to another embodiment.

FIG. 10 is a longitudinal sectional view of the filter shown in FIG.

[Explanation of symbols]

 10, 30 image reading optical device 12, 32, 66 light source 14, 42 document 16, 50, 60 filter 18, 44 reading lens 20, 46 line sensor 22 light transmitting member 24, 56, 70 ... first print patterns 25, 57, 71 ... second print patterns 26 ... scratches 34, 40a, 40b ... cylindrical lenses 38 ... field stop 64 ... aluminum pipe 68 ... glass body

Claims (5)

(57) [Claims] An image reading optical apparatus for irradiating a document with reading light and receiving transmitted light or reflected light of the document with a line sensor to obtain desired image information. A filter for controlling the light amount distribution of the read light is provided between the original and the document on which the light is recorded, and the filter is provided at a predetermined width and at a predetermined interval in a longitudinal direction of the line sensor. A first dimming portion having optical properties, a predetermined width corresponding to a predetermined distance from the first dimming portion and corresponding to a distance between the first dimming portions;
An image reading optical device, comprising: a second light-reducing portion having a predetermined light-reducing characteristic and arranged in a longitudinal direction of the line sensor at regular intervals. 2. The device according to claim 1, wherein the first light-reducing portion and the second light-reducing portion are constituted by predetermined transmittance portions provided on one surface and the other surface of the glass plate, respectively. An image reading optical device, comprising: 3. The device according to claim 1, wherein the first light-reducing portion and the second light-reducing portion are respectively provided on opposing surfaces of a pair of glass plates arranged at a predetermined distance from each other. An image reading optical device comprising a transmittance portion. 4. The device according to claim 1, wherein the first light-reducing portion and the second light-reducing portion are constituted by predetermined reflectance portions provided on the inner wall surface of the cylindrical body so as to face each other. An image reading optical device, comprising: 5. A light source for irradiating a document on which image information is recorded with reading light, a first light condensing means for condensing the reading light in a sub-scanning direction, and a first light condensing means. A second focusing unit that focuses the reading light on the document in the sub-scanning direction with the focusing position of the reading light as a front focus, and a light source that irradiates the reading light and a document on which image information is recorded. A filter for controlling the light amount distribution of the reading light, a line sensor that receives reading light from the document and converts it into an electric signal, and is long in the main scanning direction; and the document and the line sensor. A third condensing unit disposed between the line sensor and the line sensor for condensing the reading light from the document to the line sensor, wherein the filter has a constant width in the sub-scanning direction. In addition, a predetermined dimming that is arranged in the main scanning direction at a certain width and at a certain interval A first light-reducing portion having a property, and a predetermined distance from the first light-reducing portion, and a certain width corresponding to a space between the first light-reducing portions in the main scanning direction. An image reading optical device comprising: a second light-reducing portion having a predetermined light-reducing characteristic arranged.