JPH09160999A - Optical reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the complicated process for forming a multilayer film filter on the surface of an image forming lens which has been conventionally performed to obtain a desired band pass characteristic and to reduce the manufacturing cost. SOLUTION: Inside a body 1, a red filter 3 selectively transmitting the main spectral part and the part whose wavelength is longer than the main spectral part of irradiation light B by covering and closing a reading window 1a and dichroic mirror 6 which is arranged with the inclination of about 45 deg. to a circuit board 9, reflects the main spectral part and the part whose wavelength is shorter than the main spectral part of the irradiation light B at roughly right angles and guides the light to a line sensor 7, are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reading device which irradiates a recording medium on which information is optically recorded such as a bar code with light and receives the reflected light to read the information.

[0002]

2. Description of the Related Art There are various types of optical reading devices such as bar code scanners. Among them, for example, a touch type bar code scanner which has recently become widespread has an inside of a housing held by an operator. In addition, an LED array for supplying the irradiation light to the recording medium, a reflecting mirror for changing the optical path of the reflected light of the light irradiated on the recording medium, and an image of the light reflected by the reflecting mirror are formed. Image forming lens and a line sensor (CC) for receiving light that has passed through the image forming lens.
D) or a reading circuit (MPU) mounted on the circuit board for decoding the optical information received by this line sensor
A line sensor standing upright with respect to the circuit board is usually opposed to the imaging lens. However, since unnecessary light other than the light emitted by the LED array is emitted to the recording medium, in order to eliminate the adverse effect of such ambient light, the conventional product has a multilayer film filter on the surface of the imaging lens in the housing. Is formed.

That is, in order that only the reflected light of the irradiation light (usually red light) of a specific wavelength band emitted from the LED array is guided to the line sensor, it is arranged at a position facing the line sensor. In advance on the surface of the image lens
By using vacuum deposition technology, etc., a multilayer film filter having a bandpass characteristic of selectively transmitting only light in a specific wavelength band is formed, which allows reflection of ambient light having a wavelength different from that of the irradiation light. Since it becomes impossible to reach the line sensor, the change in the signal level and the deterioration in the SN ratio due to the ambient light can be greatly improved, and the reading accuracy can be improved.

The same configuration is also used in other optical reading devices such as image scanners.

[0005]

However, in the above-mentioned conventional optical reading device, by repeating the vapor deposition process for the image-forming lens after polishing in a vacuum device, 50 or more layers are formed on the surface of the lens. Since it is necessary to form a filter composed of the multilayer film, the processing cost of the multilayer film filter increases, which is a factor of increasing the cost of the product. Further, in the multilayer film filter thus formed on the curved surface of the lens surface, there is a possibility that the desired bandpass characteristic may not be obtained because the film thickness tends to vary due to unevenness of vapor deposition.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention provides a means for removing light having a wavelength shorter than the main spectrum portion of irradiation light in the optical path of reflected light from a recording medium, and a means longer than the main spectrum portion. By separately providing means for removing light of a wavelength, it is possible to obtain a desired bandpass characteristic that can receive only the main spectrum portion without forming a multilayer film filter on the surface of the imaging lens. It was decided to provide an optical reading device capable of reducing the manufacturing cost.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical reading device according to the present invention comprises an illumination means such as an LED for supplying irradiation light to a recording medium, and a line sensor for receiving reflected light of the light irradiated on the recording medium. An optical filter which is disposed in the optical path of the reflected light and selectively transmits light of a main spectrum portion of the irradiation light and light having a wavelength longer than that, and The main spectrum portion of the irradiation light and the dichroic mirror for selectively guiding the light having a wavelength shorter than that to the main spectrum portion of the irradiation light are arranged in the optical path of the reflected light.

For example, a reading window opened in the housing for allowing the reflected light to enter the inside is closed by the optical filter, and the light transmitted through the optical filter is guided to the dichroic mirror. It is preferable to have such a configuration.

As the dichroic mirror,
The main spectrum part of the illuminating light and the one that reflects light having a shorter wavelength than that and transmits light having a longer wavelength than the main spectrum part are used, and this dichroic mirror is tilted in the optical path of the reflected light. It is preferable to arrange them.

That is, in the optical reading apparatus having such a structure, when the reflected light reflected by the recording medium and entering the inside of the housing passes through the optical filter, the irradiation light supplied from the illuminating means. When the light having a wavelength shorter than that of the main spectrum portion is removed and the reflected light is incident on the dichroic mirror, the light having a wavelength longer than the main spectrum portion is removed. Of these, only the main spectrum portion of the irradiation light reaches the light receiving means, and a desired bandpass characteristic can be obtained. Moreover,
An inexpensive resin filter can be used for the optical filter,
In addition, since the process of depositing a multilayer film filter with about half the number of layers on the surface of a flat dichroic mirror is relatively easy, provide a filter consisting of a multilayer film of 50 layers or more on the surface of the imaging lens. Compared with existing products,
Manufacturing costs can be significantly reduced.

When the reading window of the housing is closed with the optical filter, the dustproof cover is not required, and the increase in the number of parts can be suppressed. Further, the dichroic mirror is tilted, for example, by about 45 degrees with respect to the circuit board on which the light receiving means is mounted, and the light reflected by the dichroic mirror at a substantially right angle is guided to the light receiving means. If so, the wiring can be simplified because the light receiving means such as the line sensor can be directly mounted on the circuit board on which the reading circuit such as the MPU is mounted without standing up.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical reading device according to the present invention will be described below with reference to FIGS. Here, FIG. 1 is an explanatory diagram showing an internal configuration of the barcode scanner according to the present invention, and FIG. 2 is an explanatory diagram showing a path of light reflected by a recording medium and incident on the barcode scanner.

As shown in FIGS. 1 and 2, the bar code scanner according to the present invention is provided on the end surface of the casing 1 held by the operator.
A reading window 1a is provided for allowing the reflected light A of the light applied to the recording medium 10 to enter the inside thereof, and the irradiation light B is applied to the area in which the barcode of the recording medium 10 is written inside the housing 1.
(The wavelength of the main spectrum part is 600 to 720 nm), the red LED array 2 for supplying the red filter 3 for closing the reading window 1a, and the reflecting mirror for changing the optical path of the reflected light A. 4, an image forming lens 5 for forming an image of the light reflected by the reflecting mirror 4, and an image forming lens 5
A dichroic mirror 6 that reflects or transmits light incident from a light source, a line sensor (CCD) 7 for receiving the reflected light A reflected by the dichroic mirror 6, and a line sensor Reading circuit (MPU) 8 for decoding the optical information received at 7.
Also, the reading circuit 8 and the circuit board 9 on which the line sensor 7 is mounted are incorporated to form a schematic configuration. That is, the red filter 3, the reflecting mirror 4, the imaging lens 5, and the dichroic mirror 6 are sequentially arranged in the optical path of the reflected light A entering the housing 1, and the red filter 3 among them is An optical filter that selectively transmits the main spectrum part of the irradiation light B and light having a wavelength longer than that,
Further, the dichroic mirror 6 reflects the main spectrum part of the irradiation light B and light having a shorter wavelength than that to guide it to the line sensor 7, and transmits the light having a longer wavelength than the main spectrum part of the irradiation light B. Have. That is, the dichroic mirror 6 is arranged in the optical path of the reflected light A with an inclination. Specifically, by tilting the dichroic mirror 6 with respect to the circuit board 9 by about 45 degrees, the dichroic mirror 6 of the reflected light A is reflected by the dichroic mirror 6. It is set so that the light reflected at a substantially right angle is guided to the line sensor 7.

The bar code scanner thus constructed irradiates the bar code area of the recording medium 10 with the irradiation light B from the red LED array 2 and the reflected light A is received by the line sensor 7. The bar code is designed to be read by the reading circuit 8, but the recording medium 1
Unnecessary light other than the irradiation light B is irradiated onto the barcode description area of 0. Therefore, in order to eliminate the adverse effect of the disturbance light, the irradiation light is combined with the red filter 3 and the dichroic mirror 6. Care is taken so that light having a different wavelength from B does not reach the line sensor 7. That is, in this bar code scanner, when the reflected light A reflected on the bar code writing area of the recording medium 10 and incident on the inside of the housing 1 passes through the red filter 3, the main spectrum portion of the irradiation light B is more than the main spectrum part. When short-wavelength light (light having a wavelength of 600 nm or less) is removed, and then the reflected light A is incident on the dichroic mirror 6 through the reflecting mirror 4 and the imaging lens 5, the main spectrum portion of the irradiating light B is emitted. Since long-wavelength light (light having a wavelength of 720 nm or more) is transmitted and deviates from the reflected light path toward the line sensor 7, only the main spectrum part of the irradiation light B can reach the line sensor 7 in the reflected light A. Thus, the desired bandpass characteristic can be obtained. Therefore, there is no possibility that the ambient light having a wavelength different from that of the main spectrum portion of the irradiation light B changes the signal level or deteriorates the SN ratio, so that good reading accuracy can always be expected.

Moreover, as the red filter 3, an inexpensive resin filter which also serves as a dust cover for closing the reading window 1a can be used, and a flat dichroic mirror having a multilayer film filter having about half the number of layers of the conventional product can be used. Since the process of vapor deposition on the surface of 6 is relatively easy, when compared with the conventional product having a dustproof cover and a filter composed of a multilayer film of 50 layers or more on the surface of the imaging lens, Code scanners can significantly reduce manufacturing costs.

Furthermore, in this bar code scanner, the dichroic mirror 6 is mounted on the circuit board 9 by about 4 mm.
By inclining by 5 degrees, the line sensor 7 is directly mounted on the circuit board 9 on which the reading circuit 8 is mounted without standing up. Therefore, the line sensor board is erected on the circuit board on which the reading circuit is mounted. This has the advantage that the wiring can be simplified as compared with the conventional product, which used complicated wiring.

Although the bar code scanner has been described in the above-mentioned embodiments, it goes without saying that the present invention can be applied to other optical reading devices such as an image scanner.

[0018]

As described above, in the optical reading device according to the present invention, even if the multilayer film filter is not formed on the surface of the imaging lens, the main spectrum portion of the irradiation light supplied from the illumination means such as the LED is used. By using an optical filter that removes light having a short wavelength and a dichroic mirror that removes light having a wavelength longer than the main spectrum part, a desired bandpass characteristic that can receive only the main spectrum part can be obtained. Therefore, there is an excellent effect that the manufacturing cost can be reduced without deteriorating the reading accuracy.

Further, if the reading window of the housing is closed with the optical filter, the dust-proof cover is not required, and the increase in the number of parts can be suppressed. Furthermore, the dichroic mirror is tilted by about 45 degrees with respect to a circuit board on which light receiving means such as a line sensor is mounted, and the light reflected from the recording medium at a substantially right angle is reflected by the dichroic mirror. If the light receiving means is guided to the light receiving means, the light receiving means can be directly mounted on the circuit board on which the reading circuit such as the MPU is mounted without standing up, and thus the wiring can be simplified.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an internal configuration of a barcode scanner according to the present invention.

FIG. 2 is an explanatory diagram showing a path of light reflected by a recording medium and incident on the barcode scanner shown in FIG.

[Explanation of symbols]

 1 Case 1a Reading Window 2 Red LED Array 3 Red Filter 4 Reflecting Mirror 5 Imaging Lens 6 Dichroic Mirror 7 Line Sensor (CCD) 8 Reading Circuit (MPU) 9 Circuit Board 10 Recording Medium A Reflected Light B Irradiated Light

Claims (6)

[Claims] 1. The reflection light is provided inside a housing incorporating illumination means for supplying irradiation light to a recording medium and light receiving means for receiving reflected light of the light irradiated on the recording medium. An optical filter that is arranged in the optical path of the irradiation light and selectively transmits light having a longer wavelength than that of the irradiation light, and a main spectrum portion of the irradiation light that is arranged in the optical path of the reflected light and An optical reading device comprising: a dichroic mirror that selectively guides light having a wavelength shorter than that to the light receiving means. 2. The light passing through the optical filter according to claim 1, wherein a reading window opened in the housing for allowing the reflected light to enter the inside is covered with the optical filter. The optical reading device is characterized in that it is guided to the dichroic mirror. 3. The dichroic mirror according to claim 1, wherein the dichroic mirror reflects the main spectrum portion of the irradiation light and light having a wavelength shorter than that, and transmits light having a wavelength longer than the main spectrum portion. The optical reading device is characterized in that the dichroic mirror is used in a tilted manner in the optical path of the reflected light. 4. The dichroic mirror according to claim 3, wherein the dichroic mirror is tilted by about 45 degrees with respect to the circuit board on which the light receiving means is mounted, and the reflected light is reflected by the dichroic mirror at a substantially right angle. An optical reading device characterized in that light is guided to the light receiving means. 5. The optical reading device according to claim 1, wherein a line sensor is used as the light receiving unit. 6. The optical reading device according to claim 1, wherein a red LED is used as the illuminating means, and a red filter is used as the optical filter.