JP2000069223A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the mechanism from becoming complicated in mechanism and making the cause of troubles since the mechanism which opens and closes an inspection window is to be incorporated, when the inspection window is formed in a device enclosure and is made to open and close by a shutter. SOLUTION: While a confirmation window for confirming the reading position of an original is composed of optical filters (plastics 12a, 12b and 12c) for almost cutting component which has a wavelength out of a diffused external light longer than, for example 600 nm, an optical filter 17 is arranged which transmits the wavelength element of illumination lights for LEDs 15a and 15b and cuts the wavelength component of the diffused external light superimposed upon a reading light, and a wavelength region to be used for reading of original and the wavelength region to be used for the confirmation of the original reading position are separated.

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 for reading an original, and more particularly to an image reading apparatus for selectively reading image information of a desired area in the original.

[0002]

2. Description of the Related Art In contrast to an image reading apparatus that reads the entire original, there is an image reading apparatus that is small and reads only a necessary portion of the original. As the image sensor used in this type of image reading apparatus, a sensor using a linear image sensor has been mainly used. In the image reading apparatus using the linear image sensor, it is necessary to move the reading portion on the document by hand scanning, so that there is a problem that scanning unevenness occurs and the read image is distorted.

On the other hand, as an application of an image reading apparatus for reading only a necessary portion in a document image, there is a use for reading an information pattern in a document such as a two-dimensional bar code. But,
In this application, when the image distortion as described above occurs, the pattern recognition accuracy deteriorates. For this reason, it is necessary for the user to master the manual scanning of the document with high accuracy.
It becomes inconvenient to use. To solve this problem, there is an idea that the image distortion caused by the scanning unevenness in the manual scanning is eliminated by capturing the entire screen in one shot using the area image sensor.

However, when an area image sensor is used, there is a new problem that it is difficult to confirm the position of the reading area. In other words, in order to perform a reading operation while keeping the focus state and the reading magnification constant, it is desirable that the reading window be brought into close contact with the document in order to fix the position of the document surface of the imaging optical system. Becomes a blind spot in the apparatus main body, and it cannot be confirmed which area is being read.

To cope with such a problem, a method of displaying a read image on an LCD (Liquid Crystal Display) and monitoring the read range in real time is considered.
The large power consumption of the D-monitor makes it easy for the battery to be consumed, and mounting the LCD leads to an increase in the cost of the device itself. In addition, there is a problem that it is difficult to grasp the position of the read image in the whole image.

[0006] On the other hand, a method of directly checking the reading range by providing a window (finder) through which the reading position can be viewed in the apparatus main body can be considered. However, in this case, disturbance light (external light) incident from the viewing window fluctuates the illumination light amount and illumination distribution at the reading position, and the recognition accuracy of a pattern such as a two-dimensional barcode decreases. In order to solve such a problem, an information reading apparatus has a configuration in which a window (finder) through which a reading position can be viewed is provided in the apparatus main body, a shutter is attached to the viewing window, and the shutter is closed at the time of imaging to cut off disturbance light. It has been proposed (see JP-A-8-87565).

[0007]

However, since the above-mentioned conventional reading apparatus employs a structure in which a shutter which operates mechanically is provided, a mechanism such as a motor for opening and closing the shutter is incorporated. Therefore, the mechanism becomes complicated and causes a failure. In addition, if the viewing window is shielded during actual image reading, the operator may be concerned about whether the reading position is correct.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to bring an apparatus body into close contact with a document in order to selectively read an image in a desired area on the document. It is an object of the present invention to provide an image reading apparatus capable of more accurately confirming a reading position on a document when reading.

[0009]

According to the present invention, there is provided an image reading apparatus comprising: an illumination unit for illuminating an original reading area in an apparatus housing having a confirmation window for confirming an original reading area; An image reading apparatus incorporating a reading means for reading information in a reading area based on reading light from a document based on the document, wherein an optical path from the illumination means to the document is obstructed in a light path from the confirmation window to the document. A first optical filter provided at a position not to restrict the spectral characteristic, and a first optical filter provided at a position not obstructing an optical path from the confirmation window to the document in an optical path from the document to the reading means, and a spectral wavelength range of the illumination means. And a second optical filter having a spectral wavelength transmission region in which a part or all of the light enters.

In the image reading apparatus having the above-described structure, the first optical filter restricts the spectral characteristics so that of the disturbance light (external light) entering the apparatus housing from the confirmation window, the first optical filter has a wavelength in a specific transmission band. Only light is transmitted. The transmitted light reaches the reading area of the document, is reflected there, and goes out of the apparatus housing through the confirmation window, so that the position of the reading area can be confirmed from the confirmation window. On the other hand, the reflected light from the reading area based on the illumination light from the illumination means passes through the second optical filter as the reading light and reaches the reading means. At this time, even if a part of the disturbance light is superimposed on the reading light, it is cut by the spectral wavelength transmission region of the second optical filter and does not reach the reading unit.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view showing a configuration of an image reading apparatus according to a first embodiment of the present invention, and FIG. 2 is a right sectional view thereof.

In FIG. 1 and FIG. 2, the apparatus housing 11 has, for example, a rectangular parallelepiped shape, and is formed of plastics 12a, 12b, and 12c of Sian color on the front side below the middle part and the front sides on both left and right sides. I have. In this device case 11, Sian plastic 12a,
Since 12b and 12c have transparency, the device housing 1
1 has a function as a confirmation window for confirming the inside from outside.

On a bottom surface 12d of the apparatus housing 11, a rectangular reading window 14 for reading an image of a desired area in the read document 13 is formed. Also, the device housing 1
In the unit 1, for example, LEDs (light emitting diodes) 15 a and 15 b are arranged obliquely above the reading window 14 as illumination means for illuminating the reading area of the document 13 through the reading window 14. The illuminating means is not limited to the LED, and another light source such as an incandescent lamp can be used.

An image forming lens 16, an optical filter 17, and an area-type CCD (Charge Coupled Device) image sensor (hereinafter, referred to as an area CCD sensor) 18 are provided above the reading window 14 in the apparatus housing 11. They are arranged in order from the bottom of the figure. The image forming lens 16 passes the reading light (image light) from the reading area of the original 13 based on the illumination light from the illumination LEDs 15 a and 15 b to an optical filter 17.
To form an image on the imaging surface of the area CCD sensor 18.

The optical filter 17 cuts unnecessary spectral components of the reading light. The area CCD sensor 18
The original image formed by the image forming lens 16 is photoelectrically converted in pixel units and output as an analog image signal. This analog image signal is converted into a digital image signal by an A / D converter in a signal processing system 19 and stored in a memory. The signal processing system 19 is disposed, for example, in the upper space 11A of the device housing 11, as shown in FIG. The battery 20 is disposed in the rear space 11B of the device housing 11.

In the image reading apparatus according to the first embodiment having the above-described structure, the Sian plastics 12a, 12a
FIG. 3 shows the spectral characteristics of b and 12c. This spectral characteristic is
The transmittance is small at a wavelength of 600 nm or more corresponding to the red region to the infrared region, for example, 10% or less on average in the spectral wavelength transmission region of the optical filter 17 (see FIG. 4). Therefore, the material itself of the plastics 12a, 12b, 12c serving as the confirmation window plays the role of an optical filter (filter 1), and limits the spectral range of light rays incident from the outside.

In this embodiment, the plastics 12a,
Although it is assumed that 12b and 12c themselves have the spectral characteristics shown in FIG. 3, the same applies when a transparent plastic is used for the confirmation window and a film having the spectral characteristics shown in FIG. The operation and effect of the present invention can be obtained.

As shown in the characteristic diagram of FIG. 4, the optical filter (filter 2) 17 disposed behind the imaging lens 16 has a characteristic of transmitting almost no light having a wavelength of 600 nm or less. On the other hand, as described above, LEDs 15a and 15b having a spectral characteristic as shown in FIG. 5 and having a peak wavelength of about 660 nm are used as light sources for illuminating the original.

Here, the influence of the reading illumination light and the disturbance light will be described. First, since the read illumination light has the characteristics shown in FIG. 5, the optical filter 1 having the spectral characteristics shown in FIG.
7 largely pass through to reach the imaging surface of the area CCD sensor 18. As a result, information of the reading area on the document 13 is read by the area CCD sensor 18. On the other hand, the wavelength component longer than the wavelength of 600 nm of the disturbance light is cut by about 90% by the material of the plastics 12a, 12b, and 12c, which are confirmation windows, and hardly reaches the reading area of the document 13.

This mechanism will be described in more detail with reference to the principle diagram of FIG. Wavelength range R incident from outside
The light of (red) is cut by the plastics 12a, 12b, and 12c having a function as an optical filter. On the other hand, the plastics 12a, 12b, and 12c transmit light in the wavelength ranges B (blue) and G (green). Therefore, the wavelength range B
The light reaches the reading area of the document 13 from the outside and exits as reflected light from the document 13.

Therefore, the reading area of the original 13 can be observed by the light in the wavelength range B from the outside. In particular, a wavelength band near 550 nm having high relative luminous efficiency can be used for document confirmation from the outside of the apparatus housing 11, so that the reading area can be positioned more accurately. Moreover, since the light in the wavelength range B is cut by the optical filter 17 having the spectral characteristics shown in FIG. 4, external light does not overlap the reading light and enter the imaging surface of the area CCD sensor 18.

Next, the light in the wavelength range R illuminating the reading area of the original 13 is reflected by the reading area, passes through the optical filter 17 as reading light, and is transmitted to the area CCD sensor 18.
To the imaging surface of. Therefore, the area CCD sensor 18 reads an image with the light in the wavelength range R.

If the ambient light is white light of about 1000 [lx] as ordinary office lighting, the irradiance is about 1 W / m ² over each of the B, G (green) and R wavelength ranges.
Equivalent to the degree. On the other hand, 660n used for illumination of the original
The irradiance of m LEDs is about 2 W / m ² .

The spectral sensitivity curve of the area CCD sensor is
As shown in the characteristic diagram of FIG. 7, the sensitivity is high near 450 to 600 nm, gradually decreases at 600 nm or more, and almost disappears at 1000 nm. Considering the sensitivity, 500-600
Although an LED having a light emission peak at nm can effectively convert light into light, an LED having a light emission peak with a wavelength of 660 nm is used for document illumination in the present embodiment because the light emission efficiency of a LED having a longer wavelength is higher. I use it as a light source.

When an image reading apparatus is constructed using such an area CCD sensor and a document illumination LED, unless a structure for preventing disturbance light is employed, disturbance light having a high sensitivity of the area CCD sensor near 450 to 600 nm is obtained. As a subject,
More than twice the sensor output of the LED illumination light,
The reading level becomes unstable depending on the incident direction of disturbance light and the like, and the illumination distribution also fluctuates, so that the pattern reading accuracy is deteriorated and stable pattern recognition cannot be performed.

FIG. 8 shows a sensor output component for each wavelength band when disturbance light having a flat spectral characteristic is incident.
This is a relative value when the signal level by the LED illumination light is 1, and the sum of all wavelength ranges is the actual sensor output level. Optical filter (Filter 2)
600 having a large effect on the sensor output due to the function of
By cutting the output below nm, the disturbance light component can be reduced to about ４ compared to when the optical filter 17 is not provided. Note that the filter 1 is Sian plastics 12a, 12b, and 12c.

Further, a plastic 12 serving as a confirmation window
By the filter action of the materials a, 12b and 12c,
Since the wavelength component of 600 nm or more can be cut to about 1/10, the influence of disturbance light can be almost completely eliminated.

In the case of office fluorescent lamp illumination, this filter works more effectively because there are few components at 650 nm or more in spectral characteristics. Also, in the case where outdoor light enters, the light intensity is normally about 1000 [lx] because of the characteristic that a peak exists at about 500 nm, and even if direct sunlight with the level of FIG. Unless otherwise, the disturbance light problem does not occur.

As described above, in the image reading apparatus according to the first embodiment, the confirmation window for confirming the reading position of the original 13 is provided with an optical element that substantially cuts a component of the disturbance light having a wavelength longer than, for example, 600 nm. The filter 13 (plastics 12a, 12b, 12c) and the original 13
LED1 in the path from the
While transmitting the wavelength components of the illumination light of 5a and 15b,
An optical filter 17 that cuts a wavelength component of disturbance light superimposed on the reading light is arranged to separate a wavelength range used for reading a document from a wavelength range used for confirming a reading position of a document. Therefore, fluctuations in the reading conditions due to the influence of the above can be minimized, so that stable document reading and pattern information recognition can be performed.

Moreover, since the original can be observed from outside the device housing 11 within the visible light range, the original can be used without any discomfort even for an original containing color information. Also, as a confirmation window,
As shown in the perspective view of FIG. 1, the front and both sides of the device housing 11 are constituted by the transparent plastics 12 a, 12 b, and 12 c instead of the openings (viewing windows) of a limited size. Manuscript 1 very easily from the side
There is also an advantage that the position of the reading area 3 can be confirmed, and the image reading apparatus is very easy to use.

FIG. 9 is a side sectional view showing the structure of an image reading apparatus according to a second embodiment of the present invention. In FIG.
The device housing 21 has a box-like shape in which the upper surface and the bottom surface are larger in area than the side surfaces, and the device housing 21 is externally mounted on the upper surface.
While a confirmation window 22 for confirming the inside of is formed,
A reading window 24 for reading an image of a desired area in the read document 23 is formed substantially immediately below the confirmation window 22 on the bottom surface.

In the apparatus housing 21, as an illuminating means for illuminating the reading area of the original 23 through the reading window 24, for example, an LED 25 is disposed diagonally above the reading window 24. As the illumination LED 25, one having a peak wavelength of about 660 nm having a spectral characteristic as shown in FIG. 5 is used. The illuminating means is not limited to the LED, and another light source such as an incandescent lamp can be used.

A dichroic mirror (dichroic mirror) 26 is attached to the confirmation window 22 of the device housing 21 in a state inclined with respect to the bottom surface. This dichroic mirror 26 has a wavelength of 6 as shown in the characteristic diagram of FIG.
It has a spectral characteristic that reflects light of 00 nm or more and transmits light below that. Accordingly, light having a wavelength of less than 600 nm can enter and exit from the outside of the apparatus housing 21, so that the reading position of the document 23 can be confirmed from the confirmation window 22. In FIG. 10, a broken line indicates the reflectance, and a solid line indicates the transmittance.

The device housing 21 further includes a mirror 27,
Imaging lens 28, optical filter 29, and area CCD
The sensors 30 are arranged so as to be substantially parallel to the bottom surface in order from the left side of the figure. Mirror 27 is LED2
5 receives the reading light of the wavelength component reflected by the dichroic mirror 26 from the reading light (image light) from the reading area of the original 23 based on the illumination light from
It is folded back in the direction of the sensor 30.

The imaging lens 28 passes the reading light turned back by the mirror 27 through an optical filter 29 to an area CCD.
An image is formed on the imaging surface of the sensor 30. Optical filter 29
Has a spectral characteristic as shown in FIG. 4 and cuts unnecessary spectral components of the reading light. Area CCD sensor 30
Converts the original image formed by the image forming lens 28 into photoelectric conversion in pixel units and outputs it as an analog image signal.

Although not shown, a signal processing system, a battery, and the like are built in an appropriate place in the apparatus housing 21 in the present embodiment, as in the first embodiment.

In the image reading apparatus according to the second embodiment having the above structure, the wavelength of 600
The light below nm is the dichroic mirror 2 in the confirmation window 22
6, the reading position of the document 23 can be confirmed more accurately. On the other hand, LE
Illumination light having a wavelength of 660 nm from D25 is reflected as reading light in the reading area of the document 23, further reflected by the dichroic mirror 26, turned back by the mirror 27, and enters the imaging lens 28.

As described above, by forming the optical system by folding the image forming optical path using the two mirrors 26 and 27, there is an advantage that the size of the image reading apparatus can be reduced. Here, the light reaching the dichroic mirror 26 from the document 23 has a wavelength of 6 by the dichroic mirror 26.
Disturbance light components of less than 00 nm are released to the outside so as not to enter the imaging optical path.

On the other hand, a dichroic mirror 26
The light having a wavelength of less than 600 nm that is directly incident on the mirror 27 through the mirror is incident on the imaging lens 28, and this wavelength component has the spectral characteristic shown in FIG. It is cut by the optical filter 29 and does not reach the imaging surface of the area CCD sensor 30.

As described above, in the image reading apparatus according to the second embodiment, the wavelength range used for reading the document and the wavelength range used for confirming the position of the reading area are separated. Confirmation window 2
The use of the dichroic mirror 26 as the optical filter mounted on the optical filter 2 and the use of the mirror 27 so that the image forming optical path is folded back has an advantage that it can greatly contribute to miniaturization of the apparatus.

In each of the above embodiments, the optical filters 17 and 29 are optical filters that transmit a wavelength range of 600 nm or less. However, bandpass optical filters that transmit about 600 nm to 750 nm may be used. good. In this case, by cutting the wavelength of 750 nm or more, the disturbance component in FIG. 8 can be further reduced to about half, which is effective in a case where direct sunlight enters.

In each of the above embodiments, an LED having an emission peak wavelength of 660 nm is used as a light source for illuminating a document. However, an LED having an emission peak in the near infrared region around 800 to 900 nm may be used. In this case, area C
The area where the sensitivity of the CD sensor is low will be used for reading, and in order to cover the decrease in output, a higher output LED must be used. Since it is sufficient to cut off the spectral characteristics of only the infrared portion, the transmittance of visible light is increased, and the visibility of the reading position can be further improved.

Further, in each of the above embodiments, the confirmation window is provided with the optical filter (plastics 12a, 12b, 12c, and the dichroic mirror 26) for cutting a specific wavelength component of the disturbance light. Instead, the position may be any position in the optical path from the confirmation window to the document and not obstructing the optical path from the illumination light source to the document. The position where the optical filters 17 and 29 are disposed is not limited to the position behind the imaging lenses 16 and 28, but is in the optical path from the original to the area CCD sensor and extends from the confirmation window to the original. Any position that does not obstruct is acceptable.

[0044]

As described above, according to the present invention,
By separating the wavelength range used for reading the original from the wavelength range used for confirming the reading position of the original, fluctuations in reading conditions due to the influence of disturbance light can be minimized. Without being affected by the light of
It is possible to perform stable document reading and pattern information recognition.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a side sectional view illustrating a configuration of the image reading apparatus according to the first embodiment.

FIG. 3 is a characteristic diagram showing a spectral transmission characteristic of the filter 1;

FIG. 4 is a characteristic diagram showing a spectral transmission characteristic of the filter 2;

FIG. 5 is a characteristic diagram showing spectral characteristics of the illumination LED.

FIG. 6 is a principle diagram for explaining a mechanism of the image reading apparatus according to the first embodiment.

FIG. 7 is a characteristic diagram showing a spectral sensitivity characteristic of the area CCD sensor.

FIG. 8 is a diagram showing the degree of influence of disturbance light due to the action of a filter.

FIG. 9 is a side sectional view illustrating a configuration of an image reading apparatus according to a second embodiment of the present invention.

FIG. 10 is a characteristic diagram showing spectral characteristics of a dichroic mirror.

[Explanation of symbols]

11, 21 ... device housing, 12a, 12b, 12c ... Sian plastic, 14, 24 ... reading window, 15
a, 15b, 25: LED for illumination, 16, 28: imaging lens, 17, 29: optical filter, 18, 30: area CCD sensor, 22: confirmation window, 26: dichroic mirror, 27: mirror

Claims (5)

[Claims] An illumination unit for illuminating a reading area of a document in an apparatus housing having a confirmation window for checking a reading area of the document, and reading the document based on reading light from the document based on illumination light by the illumination unit. An image reading apparatus incorporating reading means for reading information in an area, provided in a position not interfering with an optical path from the illumination means to the document, in a light path from the confirmation window to the document, and having a spectral characteristic. A first optical filter to be restricted, and a part provided in the optical path from the document to the reading means at a position not obstructing the optical path from the confirmation window to the document, and a part or the whole of the spectral wavelength range of the illuminating means. An image reading apparatus comprising: a second optical filter having a spectral wavelength transmission band. 2. The image reading apparatus according to claim 1, wherein a spectral wavelength transmission range of the second optical filter is in a range exceeding a wavelength at which a spectral sensitivity of the reading unit is high. 3. The image reading apparatus according to claim 2, wherein the transmission of the second optical filter in a spectral wavelength range is in an infrared range. 4. The image reading apparatus according to claim 1, wherein a spectral wavelength transmission range of the first optical filter is lower than a spectral wavelength transmission range of the second optical filter. apparatus. 5. The image reading apparatus according to claim 1, wherein said first optical filter is constituted by a dichroic mirror.