JPH0262159A - Color reader - Google Patents

Abstract

PURPOSE:To reproduce a color faithful to an original by providing a light guide path in the light path between the original and a line image sensor. CONSTITUTION:A light guide path 14 consisting of black boards 16 and 16' is provided in the light path between an original 100 and the line image sensor, and from this, the incident area of rays emitted from fluorescent lamps 6 and 6' can be limited. In addition rays 10 and 10' made incident from the fluorescent lamps 6 and 6' directly to a mirror 11 can be simultaneously eliminated. Thus, by providing the light guide path 14, only reflected rays near a read line out of the reflected rays on the original 100 can be projected on the surface of the reflection mirror 11, and they can be read.

Description

[Detailed Description of the Invention] [Summary] Regarding a color reading device used as an image input device, the purpose of improving the S/N ratio of an image signal is to use light emitted from a light source to illuminate a color image on a document. A color reading device that reads a color image in a time-division manner by guiding the reflected light from a reduction optical system through three color filters to a line image sensor, and synchronizing the driving of the line image sensor and switching of the filters, A light guide path is provided in an optical path between the original and the line image sensor to transmit only the reflected light near the reading section on the original.

[Industrial application field]

The present invention relates to a color reading device used as an image input device.

Color reading devices are widely used as image input devices for facsimiles and computers.

These color reading devices include R (red) and G (green).
, B (blue) using a COD image sensor or the like is known. These color reading devices are desired not only to be further downsized and lower in price, but also to reproduce colors that are faithful to the original being read.

[Conventional technology]

FIG. 3 is a perspective view showing the main structure of a conventional color reading device, and the structure and operation of the device are as follows.

The reading line 1 on the original 100 is illuminated by an irradiation device such as a fluorescent lamp 6.
The image on this line is read. Reflected light from the reading line 1 is imaged by a lens 2 onto a line image sensor 3 such as a CCD line image sensor.

In order to perform color reading, three color filters 4a and 4 of R, G, and B are provided between the lens 2 and the line image sensor 3.
b, 4c are provided. Filters 4a, 4b, 4c
are held by linear motors 5a, 5b, and 5c, respectively, and can be moved to a position where the optical path from the reading line 1 to the line image sensor 3 is blocked. The color reading operation is shown in FIGS. 4(a)-(C). When reading the R component of the color image on the reading line l, as shown in FIG.
The filter 4a is placed into the optical path by driving the linear motor 5a. The other two filters 4b and 4c are held at positions where they do not block the optical path. As a result, of the reflected light from the reading line 1, only the red color can reach the line image sensor 3, and the R component of the image is read. When reading the G and B components of an image, use Figure 4 (b) and (C
), there are G filters 4b and B in the optical path, respectively.
Insert filter 4C and read. l line R,G,
When the reading of B is completed, the original 100 is moved in the direction of the arrow by a predetermined amount and the next line is read.

In this way, by combining a small and lightweight filter with a high-speed linear motor, the filter can be switched in approximately the same time as the reading time of one sensor line (1 to 10m5), achieving high-speed color reading. be able to.

[Problem to be solved by the invention]

However, in the reading optical system that realizes such color reading, as shown in Fig. 5, the fluorescent lamp 6.6', which has the largest amount of light, is used (the fluorescent lamp 6' is omitted in Fig. 3). The light emitted directly above the fluorescent lamp tube or a portion of the light emitted from the entire circumference of the fluorescent lamp tube is repeatedly reflected inside the document 100 and the document placement glass plate 7 (not shown in FIG. 3) and is reflected on the mirror 8. (
(omitted in FIG. 3) or inside the device, and is reflected and scattered by dust and flakes on the surface of the mirror 8 and the wall surface inside the device. Then, these were propagated to the original image reading area and read together with the regular image signals.

Therefore, the diffusely reflected light (hereinafter referred to as stray light) 9.9' reflected from the document 100 or inside the glass plate 7, or the light 10.10' directly incident on the mirror 8 from the fluorescent lamps 6, 6' becomes noise. As a result, the S/N ratio of the image signal was significantly lowered, and colors faithful to the original could not be reproduced.

An object of the present invention is to provide a color reading device that can improve the S/N ratio of image signals.

[Means to solve the problem]

In order to achieve the above-mentioned object, in the present invention, the reflected light of the light emitted from the light source and irradiating the color image on the document is guided to the line image sensor through three color filters by the reduction optical system, and the line image sensor is guided to the line image sensor. In a color reading device that reads color images in a time-division manner by synchronizing the driving of a sensor and the switching of the filter, reflected light near the reading section on the original is included in the optical path between the original and the line image sensor. The configuration includes a light guide path that only transmits light.

In addition, in the color reading device having the above configuration, the filter is omitted and a light source of three colors is used instead, and the switching of the light source and the driving of the line image sensor are synchronized to read a color image in a time-sharing manner. do.

[Effect]

In the present invention, a light guide path is provided in the optical path between the document and the line image sensor, so that only the reflected light near the hanging portion on the document is transmitted to the image sensor, and stray light, which has been a problem in the past, is transmitted to the image sensor. can be removed. Therefore, an image signal with a high S/N ratio can be obtained. Therefore, it is possible to reproduce colors faithful to the original.

〔Example〕

The present invention will now be described in detail with reference to FIGS. 1 and 2.

FIG. 1 is a perspective view showing the main structure of a color reading device according to the present invention.
is the light guide path. Note that the same reference numerals are given to members having the same configuration as those of the conventional one. The reflecting mirrors 11, 12, and 13 together with the lens 2 constitute a reduction optical system 15. Light guide path 1
Reference numeral 4 is for transmitting only the reflected light near the reading line (reading section) 1, and is provided in the optical path between the original lOO and the line image sensor 3. In this example, as shown in detail in FIG. 2, the light guide path 14 is arranged between the fluorescent lamps 6.6' in a symmetrical position with respect to the optical axis, extending in the longitudinal direction of the fluorescent lamps 6.6'. It is shown formed by black plates 16 and 16'.

The image on the original 100 placed on the original glass plate 7 is read using fluorescent lamps 6 and 6' (the fluorescent lamp 6' is omitted in FIG. 1) and reflective mirrors 11 and 12. .13 along with the light guide path 14 along the guide shafts 17 and 17' in the document length direction. 18 is a reflecting mirror 12.
13 is a pulse motor for driving, 19 is a fluorescent lamp 6.6',
This is a pulse motor for driving the reflecting mirror 11 and the light guide path 14. Reflected light 20 (second
(see figure) is obtained. This reflected light 2° is on the optical axis 21 (
(see FIG. 1), passes through reflecting mirrors 11, 12, 13, lens 2, and color separation filters 4a, 4b, 4c, and forms an image on line image sensor 3. in this case,
The reflected light 20 is photoelectrically converted for each color of the filter that is sequentially switched, so that an image signal of the original 100 can be obtained.

During color reading, stray light components that enter from outside the reading area have a large effect on color reproducibility.

Therefore, in the present invention, a light guide path 14 made of black plates 16 and 16' arranged as described above is provided, and thereby,
It is possible to limit the incident area of light emitted from the fluorescent lamps 6, 6'. Also, due to this light guide path 14, light 10.10 directly enters the mirror 11 from the fluorescent lamp 6.6'.
' can also be removed at the same time. In this way, the light guide path 14 is provided. As a result, only the reflected light 20 near the reading line (reading section) 1 of the reflected light from the original 100 is reflected by the reflecting mirror 1.
Since the image is projected onto the surface of the reflecting mirror 11, the actual reading involves reading the image projected onto the surface of the reflecting mirror 11. Furthermore, the stray light components 9 and 9', which have been a problem in the past, can be removed. Therefore, an image signal with a high S/N ratio can be obtained.

In the above description, an example was described in which the light guide path 14 is formed by a pair of black plates 16 and 16', but it is also possible to use a rod lens array formed of light-converging optical fibers as the light guide path.
A similar effect can be obtained by inserting this into the optical path.

In the above description, an example has been described in which two fluorescent lamps are used, but it goes without saying that the same effect can be obtained with just one fluorescent lamp.

In addition, instead of the method of switching filters to perform color reading, the same applies even if a light source switching method is used, for example, in which a light source such as a fluorescent lamp of three colors (R, G, B) is turned on alternately to read a color image. You can get the following effect.

Furthermore, by using a similar light guide path for black and white reading as well as color reading, highly accurate gradation reading becomes possible.

〔Effect of the invention〕

As described above, according to the present invention, by providing a light guide path, only reflected light near the reading line on the document can be transmitted to the line image sensor, and stray light, which has been a problem in the past, can be transmitted to the line image sensor. Since it can be removed, an image signal with a high S/N ratio can be obtained, and color reproduction faithful to the original can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the main structure of a color reading device according to an embodiment of the present invention, Fig. 2 is a diagram illustrating the structure and operation of a light guide path, and Fig. 3 is a main structure of a conventional color reading device. 4 (al, (b), (C1 is a diagram explaining the color reading operation of the device in FIG. 3, and FIG. 5 is a diagram explaining the problems of the conventional color reading device. In the figure, 1 1 is a reading line (reading part), 3 is a line image sensor, 4a, 4b, 4c are filters, 14 is a light guide path, 15 is a reduction optical system, 100 is a document. 1 Reading line (M reading part) FIG. FIG. 2 is an explanatory diagram of the II production process of the light guide path in an actual flow example of the present invention.

Claims (2)

[Claims] (1) The reflected light emitted from the light source and irradiating the color image on the document is passed through three color filters [4a], [4b], [4c] by the reduction optical system [15] to the line image sensor [ 3] and the line image sensor [3]
In a color reading device that reads color images in a time-division manner by synchronizing the driving of the filter and switching of the filters [4a], [4b], and [4c], an optical path between the original and the line image sensor [3] is provided. A color reading device characterized in that a light guide path [14] for transmitting only the reflected light near the reading section of the document is provided therein. (2) In the color reading device according to claim [1], the filters [4a], [4b], and [4c] are omitted and the light source is replaced with three colors, and the light source is switched and the line image sensor [3] A color reading device characterized in that the driving described in [3] is synchronized to read color images in a time-division manner.