JPH0269065A - Picture reader - Google Patents

Abstract

PURPOSE:To improve the colored original reading speed and stabilize the reading by providing liquid crystal shutters which transmit or block irradiating light from white light sources and a red, green, and blue filters which respectively separate the irradiating light from each white light source into light rays having wavelengths of red, green, and blue. CONSTITUTION:The surface of an original 20 to be read is irradiated with light having each spectral distribution characteristics of red, green, and blue by transmitting and blocking light from light sources 21, 26, and 27 by means of liquid crystal shutters 22, 28, and 29 so that the rays of light can flash. Therefore, limitation to the reading timing of a picture reader 11 as a whole by the characteristics (light remaining time, etc.) of a light source (fluorescent tube) seen in the conventional example can be eliminated and the reading speed of the picture reader 11 provided with such color separating system can be improved. Moreover, since the light irradiating (flashing) timing of each light source 12-14 can be synchronized to each other, the reading can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image reading device, and more particularly to an image reading device that separates a color document into color and converts the read image signals into image signals.

(Prior Art) Recently, the demand for color images has been increasing mainly in the field of image processing. To meet these demands, an image reading device that can read color documents manually was developed.
It is becoming widely used.

An example of such an image reading device is shown in FIG. 4, for example. This image reading device has spectral distribution characteristics (
A color original is read by separating the colors by using a plurality of light sources with different emission wavelengths and blinking the plurality of light sources sequentially at a predetermined timing. In FIG. 4, 1 is an image reading device, and the image reading device 1 includes a light source 2.3.4, a mirror 5, an infrared cut filter 6, an optical system 7, an image sensor 8, and the like. Light sources 2.3.4 are fluorescent tubes with red, green, and blue spectral radiation characteristics, respectively.
Irradiate 9 sides of the original. The light reflected by the surface of the original 9 is introduced into the image sensor 8 via the mirror 5, the infrared cupto filter 6, and the optical system 7, and is read. When reading the original 9, the light source 2 is first turned on and illuminates the original 9. Therefore, an image containing red color information is read by the image sensor 8. Note that the light source 2 is turned off after reading is completed. Then, the light source 3.4 blinks in sequence, and the image sensor 8 reads an image with green color information and blue color information. After reading by each light source 2.3.4,
The document 9 is transported to the next reading position by a transport means (not shown). The above operations are repeated at predetermined timing, and the entire document 9 is read.

(Problems to be Solved by the Invention) However, such conventional image reading devices have a problem in that it is difficult to increase the reading speed. That is, this image reading device l has light sources 2.3.
4, color separation is performed by sequentially lighting up fluorescent tubes with spectral distribution characteristics for red, green, and blue.
Characteristics such as afterglow time are different. For example, the light source 4 having blue spectral distribution characteristics has a fast rise time and a short afterglow time. Further, the light source 3 having red spectral distribution characteristics exhibits characteristics similar to those of the light source 4, although the afterglow time is somewhat longer. However, light source 3 with green spectral distribution characteristics is light source 2.
Compared to 4, the afterglow time is long. Therefore, the timing of continuing the document 9 is limited by the characteristics of the light source 3, which is a factor that hinders speeding up of reading.

In addition, the timing of blinking of the light source 2.4 is set according to the characteristics of the light source 3, but as mentioned above, each light source 2.3
．． Since the start-up of light emission, afterglow, etc. are different for each four, there is a possibility that the reading characteristics will vary.

(Object of the invention) Therefore, the present invention focuses on such conventional problems, and
It is an object of the present invention to provide an image reading device that can read color documents at high speed and stably.

(Structure of the Invention) In order to achieve the above Old Testament, the present invention uses three primary colors of light,
In an image reading device that irradiates a document surface with light having emission wavelengths of red, green, and blue, and obtains image signals corresponding to each color component of red, green, and blue, three light beams irradiate the document surface. a white light source, a liquid crystal shutter provided between the document surface and each of the white light sources to transmit or block the irradiated light from the white light source, and a liquid crystal shutter provided between the document surface and each of the white light sources, each of the white light sources; The device is characterized by comprising red, red, green, and blue filters that separate the irradiated light from the light into red, green, and blue emission wavelengths, respectively.

(Examples) Hereinafter, the present invention will be specifically described based on Examples. 1 to 3 are diagrams showing one embodiment of the present invention.

In FIG. 1, 11 is an image reading device, which includes a light source unit I2, 13, 14 and a mirror 1.
5. An original 20 (color original) is equipped with an infrared cut filter 16, an optical system 17, an image sensor 18, an original transport means 19, etc., and is placed on an original table (not shown).
is read and output as an image signal.

The light source unit 12 includes a light source 21, a liquid crystal shutter 22, and a red filter 23. The light source 21 is, for example, a fluorescent tube that emits white light, and the light source 21 emits light over the entire reading width of the device.

The liquid crystal shutter 22 includes, for example, a glass substrate 31, a segment electrode 32, a liquid crystal 33, a common electrode 34, and a glass substrate 35, as shown in FIG.

In addition, polarizing plates 36.3 are provided on both sides of the liquid crystal shutter 22.
7 is provided. Transparent conductive films are used for the segment electrodes 32 and the common electrodes 34, and the segment electrodes 32 are formed on the glass substrate 31, and the common electrodes 34 are formed on the glass substrate 35 by vapor deposition or the like. In the liquid crystal 33, when a driving voltage is applied to the segment electrode 32 and the common electrode 34, the long sleeve direction of the liquid crystal 33 changes depending on the direction of the applied voltage, and light is refracted and propagates along the long sleeve direction of the liquid crystal 33. . The polarizing plates 36.37 are arranged so that their polarization directions are 90" opposite to each other, and the polarizing plates 36.3
The light directly polarized by the liquid crystal 33 is refracted along the long direction of the liquid crystal 33. Therefore, this refraction direction is
．． When the polarization direction of the liquid crystal 33 matches the polarization direction of the polarizing plates 36 and 37, the light is transmitted, and when the light refracted by the liquid crystal 33 does not match the polarization direction of the polarizing plates 36 and 37, the light is blocked. Note that the liquid crystal shutter 22 of this embodiment blocks light when no voltage is applied, and transmits light when a driving voltage is applied. Such a liquid crystal shutter 22 faces the light source 21 and is formed across the width direction of the light source 21 (main scanning direction of reading), and the light from the light source 21 is controlled to blink by passing through and blocking the liquid crystal shutter 22. be done.

Returning to FIG. 1, the red filter 23 is the liquid crystal shutter 2.
It is provided opposite to 2. Therefore, the light (white light) from the light source 21 that has passed through the liquid crystal shutter 22 passes through the red filter 23 to become light with red spectral distribution characteristics (emission wavelength) and illuminates the surface of the original 20. Although not shown, the light source 21. The liquid crystal shutter 22 and the red filter 23 are housed in a predetermined case or the like.

On the other hand, the light source unit 13 is provided with a green filter 24, and the light source unit 14 is provided with a blue filter 25. Note that the light sources and liquid crystal shutters of the light source units 13 and 14 have the same configuration as the light source unit 12, so different numbers will be added and explanations will be omitted. Therefore, the light from the light source 26 passes through the green filter 24 to become light with green spectral distribution characteristics and illuminates the surface of the original 20, and the light from the light source 27 passes through the blue filter 25. By doing so, the light having blue spectral distribution characteristics is irradiated onto the original 20 surface.

The light emitted from the light source units 12, 13, and 14 is reflected by the original 20 and introduced into the mirror I5. mirror 15
The light reflected by the infrared cut filter 16 and the optical system 17
is introduced into the image sensor 18 through. The infrared cut filter 16 limits infrared light that affects the sensitivity of the image sensor I8. The optical system 17 is a so-called lens, and reduces the reflected light from the surface of the document 20 (in other words, the image of the surface of the document 20) at a predetermined ratio and forms an image on the element of the image sensor 18 . The image sensor 18 uses, for example, a line-type COD, which main-scans the image formed on the element and generates an electric signal (hereinafter referred to as an image signal) corresponding to the amount of light for each I line. Convert and output. That is, the image sensor 18 is the light source unit 12.13.
．． Image information including a red color component, a green color component, and a blue color component is read by the irradiation light from 14, and is converted into an image signal and output.

The document transport means 19 is composed of, for example, rollers 41, 42 and a drive mechanism (not shown), and moves the document 20 placed on a document table (not shown) line by line at a predetermined timing as shown in FIG. Convey (sub-scan) in the direction of the arrow.

Next, the action will be explained.

The image reading device 11 of the present invention has a major feature in that the liquid crystal shutter 22 controls blinking of light having red, green, and blue spectral distribution characteristics.

Reading of the original 20 is performed in the following procedure. First, a drive voltage is applied to the liquid crystal shutter 22 of the light source unit 12 from a control section (not shown). As a result, the original 20 is irradiated with light having red spectral distribution characteristics, and image information containing a red color component is read by the image sensor 18. When the reading is completed, the application to the liquid crystal shutter 22 is stopped and the light is blocked. Next, a drive voltage is applied to the liquid crystal shutter 28 of the light source unit 13 from the control section.

As a result, the surface of the original 20 is irradiated with light having green spectral distribution characteristics, and image information containing a red color component is read by the image sensor 18. When the reading is completed, the application to the liquid crystal shutter 28 is stopped and the light is blocked.

Next, a drive voltage is applied to the liquid crystal shutter 29 of the light source unit 14 from the control section. As a result, the surface of the original 20 is irradiated with light having blue spectral distribution characteristics, and image information containing a blue color component is read by the image sensor 18. When the reading is completed, the application to the liquid crystal shutter 29 is stopped and the light is blocked. Light source unit 12.13.1
After the reading by irradiation 4 is completed, the original 20 is transported by the original transport means 19 to the next reading position (the next line position). Then, each light source unit 1
2.13.14 Light, green, and blue light with spectral distribution characteristics are sequentially irradiated, and the image sensor]
The image information is read by 8, and the entire document 21 is read by repeating this process.

In this way, the light from the light sources 21, 26, and 27 is transmitted and blocked by the liquid crystal shutters 22, 28, and 29, respectively, so that the 20 sides of the original to be read have red, green, and blue spectral distribution characteristics. Since light is irradiated, the timing of reading the entire image reading device 11 is not limited by the characteristics (afterglow time, etc.) of the light source (fluorescent tube) as in the conventional case. Therefore, it is possible to increase the speed of reading by an image reading device equipped with such a color separation method.

Further, since the timing of irradiation (blinking timing) by each light source unit 12 and I3.14 can be made the same, it is possible to stabilize reading.

Note that although a fluorescent tube is used as a light source in this embodiment, the present invention is not limited to this. Any white light source can be used.

Examples of such light sources include halogen lamps and xenon lamps.

Further, in this embodiment, red, green, and blue filters are provided between the document surface and the liquid crystal shutter, but the present invention is not limited to this. For example, as shown in FIG. 3, red, green, and blue filters may be provided between the liquid crystal shutter and the light source.

Further, in this embodiment, an image reading device that conveys a document and reads an image has been described, but the present invention is not limited to this. For example, the present invention can be applied to a book-type image reading device in which a document is fixed and a mirror, an optical system, etc. are transported.

In short, various embodiments are possible without departing from the technical idea of the present invention, and the present invention can be applied to all devices that read color originals.

(Effects) According to the present invention, it is possible to provide an image reading device that achieves high-speed and stable color document reading.

[Brief explanation of the drawing]

1 to 3 are diagrams showing one embodiment of the image reading device of the present invention, and FIG. 1 is a configuration diagram of main parts of the image reading device, and FIG.
The figure is a sectional view of a main part of the light source unit, and FIG. 3 is a diagram showing another aspect of this embodiment. FIG. 4 is a diagram showing the main parts of a conventional image reading device. Image reading device, original, light source (white light source) LCD shutter Red filter Green filter Blue filter Fig. 1 Systems Intelligence Products Co., Ltd. Fig. 2 / Fig. Fig.

Claims (1)

[Scope of Claims] An image reading device that illuminates the surface of a document with light having emission wavelengths of red, green, and blue, which are the three primary colors of light, and obtains image signals corresponding to each color component of red, green, and blue. three white light sources that irradiate light onto the document surface; a liquid crystal shutter that is provided between the document surface and each white light source and transmits or blocks the irradiated light from the white light sources; An image reading device characterized by comprising: red, green, and blue filters that are provided between each white light source and separate the irradiated light from each white light source into red, green, and blue emission wavelengths, respectively. .