JPH06169375A - Image reader - Google Patents

Abstract

PURPOSE:To surely obtain illuminance increase effects at an image division position even with a general halogen lamp as to an image divisional read system. CONSTITUTION:The image divisional read system using a reflection body which is arranged on the optical axis of the image pickup lens and has two reflecting surfaces for splitting and reflecting a light image transmitted through an image pickup lens lights a document 9 by a rod type light source 22 having plural light emission points 23a-23e; and one of the light emission points 23a-23e of the light source 22 is arranged most closely to the part corresponding to an image division position 26 on the surface of the document 9 divided by the reflecting surfaces of the reflection body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus of an image division reading type which is equipped with an image pickup lens, a reflector and a solid-state image pickup element used in a scanner, a copying machine and the like.

[0002]

2. Description of the Related Art Conventionally, there is a document image reading apparatus using a solid-state image pickup device such as a CCD as a reading device, but it is not possible to read an image with a resolution higher than the number of pixels of the image pickup device.

In this respect, an attempt to read an image with a resolution higher than the resolution of one image pickup device provided as a product is disclosed in JP-A-60-213178 and JP-A-63-63.
It has already been proposed, for example, in Japanese Patent Laid-Open No.-131465. FIG. 4 shows the principle thereof, in which a plurality of reflectors 4, here two reflecting surfaces 4a and 4b, are arranged on the optical image 2 obtained through the imaging lens 1 at the pupil position of the imaging optical system 3. Each image 5a, 5 which is divided and reflected and divided by the reflecting surfaces 4a, 4b
Two solid-state image pickup elements 6 arranged so as to form images b on the respective light-receiving surfaces at positions optically shifted from each other by a predetermined pitch.
The original image is read by forming images on a and 6b and synthesizing the images read by the solid-state image pickup devices 6a and 6b. That is, the image 7 to be read is displayed on the reflector 4
A plurality of solid-state image pickup devices 6a, 6b by the optical path splitting part
It is an attempt to obtain an original image by dividing the above into an image and combining them.

In the case shown in FIG. 4, since the two solid-state image pickup devices 6a and 6b are used, it is apparently equivalent to reading using an image pickup device having twice the number of pixels.

However, in the case of such a reading method, a plurality of light beams near the optical axis, in the illustrated case, are distributed to each of the two solid-state image pickup devices 6a and 6b to form an image. Then, the amount of light near the optical axis decreases, and S /
There is a drawback that N is deteriorated. FIG. 5 shows this state. This shows the shading distribution in one solid-state image pickup device, and since the light amount on the optical axis is divided into two, it is theoretically reduced to 50%. Such a deterioration in S / N causes a change in signals between solid-state image pickup devices (especially, a change in hue and brightness) at the boundary portion of the image, so that the combined portion (boundary line) becomes conspicuous. The above publication does not take any measures against such a decrease in the illuminance of the portion corresponding to the image dividing position on the light receiving surface.

As a method of making the combined portion (boundary line) inconspicuous, an averaging method has been considered in which output image data in the vicinity of the boundary read by dividing is multiplied by an averaging process and output. However, this does not eliminate the cause. That is, in order to obtain a high effect while reducing the load on the image processing, it can be said that it is necessary to take measures to make the boundary inconspicuous at the stage of the original image signal.

[0007] The followings have been proposed as a solution from this point of view. In the first method, as shown in FIG. 6, for example, a document 9 placed on the contact glass 8 is provided with a lamp 10 and a direct light-shielding plate 11, a quadratic curved reflector 12 and a counter reflector 13. It is applied to a reflective original reading method in which the light source unit 14 illuminates and the reflected light from the original 9 is read through the imaging optical system after the first mirror 15. In this case, as shown in FIG.
A rectangular or V-shaped slit 11a or 11b is formed directly on a part of the light shading plate 11 (a portion corresponding to the image division position),
The vicinity of the boundary line is illuminated by the direct light from the lamp 10 and the indirect light from the reflector 12 through the slit 11a or 11b, while the other portions are illuminated only by the indirect light by the reflector 12.

The second method is, for example, as shown in FIG. 8, provided with a lamp 16 and a reflection plate 17, and further includes a diffusion plate 1.
The light source unit 19 including the document holder 20
The present invention is applied to a transparent original reading method in which the transparent original 21 held by is illuminated. In this case, the diffusing plate 18 is devised, and the diffusing surface 18b is formed on one side or both sides of the transparent substrate 18a as shown in FIG. 9, but the diffusing surface 18b near the center line of the diffusing surface 18b is used.
The transparent area 18c is eliminated so that the vicinity of the central boundary line is illuminated by the direct light through the transparent area 18c, while the other portions are illuminated by the diffused light through the diffusion surface 18b. .

[0009]

As the lamps 10 and 16, linear light sources, generally halogen lamps and the like are used. However, in general, the halogen lamp (also referred to as a double-terminal halogen lamp) 22 has a plurality of short filaments 23, which are light emitting points, connected linearly via an anchor 24 as illustrated in FIG. The structure has the caps 25 at both ends. Also,
Even if the halogen lamp 22 is generally called, the position and the length of the filament 23 are variously changed depending on the design specification of the lamp.
Even when used as No. 16, not all are effective for increasing the illuminance near the boundary line. For example, in the case where the slit 11a or 11b is formed as shown in FIG. 7, if there is no filament 23 at a position over the slit 11a or 11b from the area near the boundary line, the illuminance by the direct light from the lamp 10 It cannot be expected that the correction effect will be improved. Further, even when the distance between the filament position and the image division position is long, the effect of increasing the illuminance cannot be sufficiently obtained.

The same applies to the case of the transmissive original illumination system through the diffusion plate 18 as shown in FIGS. 8 and 9, and when the halogen lamp 22 is used as the lamp 16, Position of filament 23 and transparent area 18c
It can be said that it is necessary to specify the positional relationship with

[0011]

According to a first aspect of the present invention, a linear light source having a plurality of light emitting points for illuminating a document placed on a document placing means, and one line of the document are imaged. An image pickup lens, and a reflector having two reflecting surfaces arranged on the optical axis of the image pickup lens and dividing and reflecting the light image transmitted through the image pickup lens; An imaging optical system including a solid-state imaging device that reads an optically different imaging area for each light image divided and reflected by the surface is provided, and a part of the imaging optical system is scanned along the document surface. In the image reading apparatus configured to read the entire image of the document, any one of the light emitting points of the light source is divided by the reflecting surface of the reflector to correspond to the image dividing position on the document surface. I placed it in close proximity to.

In this case, according to the second aspect of the present invention, the number of light emitting points is an odd number, and the light emitting point at the center thereof is arranged closest to the portion corresponding to the image division position.

According to the third aspect of the present invention, the image division positions are formed by the indirect illumination by the light source so that the illuminance distribution becomes higher at the image reading position of the document than at other portions except the both ends of the image. The brightness of the light emitting point closest to the corresponding portion is set to be high, or the light emitting length of this light emitting point is set to be long.

[0014]

According to the first aspect of the invention, since the light emitting point is disposed closest to the corresponding portion on the document surface corresponding to the image dividing position, the illuminance can be surely increased and the vicinity of the image dividing position can be achieved. It is possible to avoid a decrease in S / N due to a decrease in illuminance.

In particular, according to the second aspect of the invention, the number of light emitting points is an odd number and the central one is arranged closest to the image dividing position, so that the image is illuminated symmetrically about the image dividing position. In this case, the design of the light source becomes easy,
As a result, high-quality reading can be easily realized.

According to the third aspect of the invention, the light emitting point closest to the image division position of the light source is:
The emission brightness is set to be high or the emission length is set to be long so that the illuminance distribution is higher than the other portions except the both ends of the image, so that even when the emission point and the document reading position are separated, It becomes possible to efficiently correct the decrease in illuminance in the image division portion, and S /
N drop is avoided.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. The same parts as those shown in FIGS. 4 to 10 are denoted by the same reference numerals (the same applies to the following embodiments). First, the basics of the image reading method of the present embodiment are based on the image division reading method as described with reference to FIG.
For example, it is assumed that the reflection original reading method as described with reference to FIG. Under such a premise, in this embodiment, the halogen lamp 22 is used as the light source lamp 10, and the positional relationship with the image division position is clarified.

First, the halogen lamp 22 of this embodiment is 5
It is assumed to have individual filaments 23a-23e,
The filament 23c located at the center of the left-right symmetry is arranged in the halogen lamp 22 so as to be closest to the image division position 26 by the reflector 4 (see FIG. 4) on the surface of the original 9 and such a filament is formed. 23c and the image dividing position 26 directly between the slit 11a of the light shielding plate 11
It is arranged so that is located.

With such a configuration, in the illumination system as shown in FIG. 6, the vicinity of the image division position 26 is always illuminated by the direct light 27 from the filament 23c,
The illuminance up correction effect by the illuminance distribution 28 as shown is secured. As a result, a reduction in illuminance at the image division position 26 in the image division reading method is fundamentally corrected, an S / N reduction near the image division position 26 is avoided, and high-quality image reading becomes possible. In particular, in this embodiment,
Since the number of filaments is odd (here, five) and the central filament 23c is arranged corresponding to the image division position 26, it is easy to balance the left and right illuminance distributions.

Although the present embodiment has been described as an application example to the reflection original reading system as shown in FIG. 6, the halogen lamp 22 is used as the lamp 16 and the filament 23c is used.
Is arranged so as to correspond to the image division position (not shown) and the transparent area 18c, it can be similarly applied to the transparent original reading method as shown in FIG.

Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, a light source unit 30 having a rod shape as a whole by disposing a plurality of, for example, five single-terminal halogen lamps 29a to 29e serving as light emitting points discretely in a straight line in a light source such as the lamps 10 and 16 is provided. The one-terminal halogen lamps 29a to 29 are used.
One of e, for example, a central one-terminal halogen lamp 29
It is arranged so that c is closest to the image division position.

Further, a third embodiment of the present invention will be described with reference to FIG. The present embodiment considers a case where the image division position is illuminated by direct light and indirect light, as described with reference to FIGS. 6 and 7, for example. First, referring to FIG. 6 and the like, the indirect light becomes a convergent light beam by the reflection plate 12, whereas the direct light becomes a divergent light beam. Therefore, if the distance between the lamp 10 (= halogen lamp 22) and the image dividing position is too large, the effect of increasing the illuminance at the image dividing position by the direct light is reduced. That is, the filament length and the filament interval of a normal halogen lamp are designed to correct a decrease in the amount of light in the periphery according to the flat or cos ⁴ θ rule at positions separated by a predetermined distance. FIG. 3B shows an illuminance distribution characteristic according to the cos ⁴ θ rule, which is an illuminance distribution 31 formed at the image reading position by the lamp 10 by indirect illumination.

Considering such a situation, however, in this embodiment, instead of the general illuminance distribution 31, FIG.
As shown in FIG. 5, the illuminance distribution 32 is formed at the image reading position of the original 9 by indirect illumination, in which the illuminance is higher in the vicinity of the image division position than in other portions except for the vicinity of both ends of the image. , For example, the filament 23c closest to the portion corresponding to the image division position 26 in FIG.
The brightness of is set high (light emission interval is set short), or
The emission length (filament length) of the filament 23c is set to be long.

The distribution of light having such an illuminance distribution 32 is the filament 23c corresponding to the image division position 26.
This can be achieved by increasing the filament length of No. 2 and setting the distance between the adjacent filaments 23b and 23d to be longer than in the case where the illuminance distribution 31 is provided.

By providing an illumination characteristic as shown by an illuminance distribution 32 in FIG. 3A on the surface of the original 9, the halogen lamp 22 (same in the case of the light source unit 30) and the image reading position are separated to some extent. However, image division position 2
The illuminance increasing effect of 6 can be maintained.

[0026]

According to the first aspect of the invention, in the image division reading system, any one of the light emitting points of the light source is divided by the reflection surface of the reflector to correspond to the image division position on the original surface. Since it is arranged closest to the part, it is possible to surely increase the illuminance near the image division position, and avoid the S / N reduction due to the illuminance decrease near the image division position to perform high-quality image reading. be able to.

In particular, according to the second aspect of the present invention, the number of light emitting points is an odd number and the central one is arranged closest to the image dividing position, so that the image is illuminated symmetrically about the image dividing position. In this case, the light source can be easily designed, and as a result, high-quality reading can be easily realized.

According to the third aspect of the invention, with respect to the light emitting point which is closest to the image dividing position of the light source, the light emitting brightness is set to be high or the light emitting length is set to be long, and the other parts except the both ends of the image are set. Since the illuminance distribution is higher than that, even when the light emitting point and the document reading position are separated,
It is possible to efficiently correct the decrease in illuminance at the image division portion, and avoid the S / N decrease due to the decrease in illuminance near the image division position.

[Brief description of drawings]

FIG. 1 is a front view showing a first embodiment of the present invention.

FIG. 2 is a front view of a light source unit showing a second embodiment of the present invention.

FIG. 3 is an illuminance distribution characteristic diagram including a general example showing a third embodiment of the present invention.

FIG. 4 is a principle diagram showing a conventional image division reading method.

FIG. 5 is an illuminance distribution characteristic diagram.

FIG. 6 is a side view showing a reflection original reading method.

FIG. 7 is a perspective view showing the configuration of the light source unit.

FIG. 8 is a side view showing a transparent original reading method.

FIG. 9 is a perspective view showing the structure of the diffusion plate.

FIG. 10 is a front view showing a general halogen lamp configuration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Imaging lens 2 Optical image 3 Imaging optical system 4a, 4b Reflective surface 4 Reflector 6a, 6b Solid-state image sensor 8, 20 Original mounting means 9,21 Original 22,30 Light source 23a-23e Light emitting point 26 Image division position 29a- 29e luminous point 32 illuminance distribution

Claims (3)

[Claims] 1. A linear light source having a plurality of light emitting points for illuminating a document placed on a document placing means, an imaging lens for imaging one line of the document, and an optical axis of the imaging lens. A reflector having two reflecting surfaces for dividing and reflecting the light image transmitted through the imaging lens, and for each light image arranged at relatively different positions and being divided and reflected by the reflecting surfaces. An image forming optical system including a solid-state image sensor that reads optically different image pickup areas is provided. By scanning a part of the image forming optical system along the document surface, the entire image of the document is read. In the image reading apparatus described above, any one of the light emitting points of the light source is disposed closest to the image division position corresponding portion on the document surface divided by the reflection surface of the reflector. Image reading device. 2. The image reading apparatus according to claim 1, wherein the number of light emitting points is an odd number, and the light emitting point at the center thereof is disposed closest to the image division position corresponding portion. 3. A portion corresponding to the image division position is arranged closest to the image reading position of the original by an indirect illumination by a light source so that an illuminance distribution having a higher illuminance than the other portions except for both ends of the image is formed. 3. The image reading apparatus according to claim 1, wherein the brightness of the light emitting point is set high, or the light emitting length of the light emitting point is set long.