RU2305865C2 - Device for reading graphical and textual information - Google Patents

Abstract

FIELD: tool-making industry, possible use for reading graphical and textual information, such as passport and visa documents at customs checkpoints, at customs control stations of airports, railroads and automobile roads.

SUBSTANCE: device includes lighting device and, mounted serially: four-sided prism with a part for positioning object of reading, three-sided rectangular prism, flat-concave lens, objective, matrix photo-receiver and block for processing image of the object of reading, connected to the matrix photo-receiver. Prism system has height which is substantially less than the smallest linear dimension of the document being read. Light beam from illuminated object of reading after multiple reflections in prism system is focused by objective in matrix photo-receiver without geometrical distortions of image of the object of reading.

EFFECT: simplified design of the block for processing image of the object of reading.

4 cl, 21 dwg

Description

The invention relates to the field of instrumentation and can be used to read graphic and textual information, for example passport and visa documents, at checkpoints at border checkpoints, in places of customs control of airports, railways and highways.

A photographing device is known (RU 2222033 C1, cl. 7 G02B 6/24, G06K 7/14, 2004/01/20) used in authentication devices for banknotes and other valuable documents.

Known photo-reading device contains a Central fiber and optically and mechanically associated with it, at least one pair of side fibers with radiation sources. One end of the central fiber is facing the illuminated object under study, the other end is facing a matrix photodetector connected to the registration unit.

The reasons that impede the achievement of the technical result indicated below when using a known device include the need to scan information stored on the medium.

Also known is a photo-reading device for text and graphic information (RU 2032217 C1, cl. 6 G06K 7/14, 03/27/1995), containing a light source, a semiconductor laser, a focusing element, a mirror in series, mounted at an angle of not more than 45 ° to the normal the plane of the information carrier and optically connected through it to the lens, a line of independent photodetector elements, each of which is connected through an amplifier to the corresponding threshold element.

When the information carrier is moved in two coordinates relative to the backlight created by the laser, images of the information carrier sections are sequentially projected onto the photocell array, while the reaction of the photocells carries the information available on the medium.

The reasons that impede the achievement of the technical result indicated below when using a known device include the need to scan information stored on the medium.

The closest in technical essence and the achieved result to the claimed technical solution relates to a known device for reading graphic and textual information (RU 2237282 C2, CL 7 G06K 7/10, G02B 6/10, H04N 1/00, 09/27/2004).

The known device contains a radiation source, made in the form of a line of incandescent lamps, a fiber with a section optically connected to the storage medium, and a photodetector - a line of photodetector elements connected to an analog-to-digital converter. The fiber is made in the form of an optically transparent plane-parallel plate, one of the ends of which (facing the document to be read) is perpendicular to the side faces of the plate, and the opposite end, under which the radiation source is located, is beveled at an angle to the side faces of the plate. The second end faces of the plate are made reflective.

The image of the illuminated section of the information carrier, reflected from the beveled end of the plate, is sent to the lens, in the image plane of which there is a line of photodetector elements, the signals from which after analog-to-digital conversion in the converter are stored in memory or processed further in the usual way.

To read the full amount of information from the carrier, it is moved (scanned) relative to the end face perpendicular to the side faces of the plate — the input face of the fiber.

The reasons that impede the achievement of the technical result indicated below when using the known device include the nonlinearity of the readable portion of the medium projected onto the line of photodetector elements due to its “barrel-like” distortion at the edges of the lens’s working field, the limited field of view of the device and the need to scan the information on the medium.

The task to which the invention is directed is to increase the speed of reading information, reducing the size of the device and improving the image quality.

The technical result obtained by the implementation of the invention is to increase the field of view of the device while reducing its size and improving image quality.

The specified technical result in the implementation of the invention is achieved by the fact that in the inventive device for reading graphic and textual information, including a illuminator, sequentially installed optical fiber with a section of optical communication with the reading object, a lens, an array photodetector and an image processing unit of the reading object connected to it, unlike the known device, the fiber is made in the form of two in series with the gap of the installed prisms - tetrahedral with a section for placing the object reading and a smaller width of a triangular rectangular; the illuminator is made in the form of at least one pair of rulers of light sources installed symmetrically near the opposite side faces of the tetrahedral prism and / or near its exit face symmetrically with respect to the trihedral prism; for a tetrahedral prism, the reflecting face adjacent to the site for the reading object is commensurate with it and forms an acute angle with the input face, which provides full internal reflection of the line of sight returned to it, and the reflecting face opposite the input forms an optical wedge with it; in this case, other angles between the faces of the tetrahedral prism and their lengths are selected from the condition of triple reflection of the line of sight from it and its fall on the output face and the input hypotenous face of the rectangular prism, which is at an angle close to normal, located at an obtuse angle to the input one, and the parameters of a rectangular prism are selected from the condition of reflection of the line of sight from its first leg, placed in the same plane as the input face of the first prism, the second total internal reflection from the input hypotenuse face and falling on the output second cathete face at a normal angle; at the same time, an additional negative plane-concave lens is installed between the lens and the output face of the rectangular prism, with the center pupil of the spherical surface of which on the line of sight is the entrance pupil of the lens, in the image plane of which an array photodetector is installed.

The specified technical result is also achieved by the fact that the side faces and / or the illuminated sections of the output face of the tetrahedral prism are made opaque, with the exception of local sections on them that are interfaced with light sources, the area for accommodating the reading object is equipped with a protective glass installed with a gap in the form of a plane-parallel plate, and a rotary mirror is mounted between the negative lens and the lens.

Figure 1 shows the inventive device, figure 2 is the same, a top view.

The inventive device for reading graphic and textual information comprises a illuminator 1, a sequentially mounted light guide 2, a flat-concave lens 3, a lens 4, an array photodetector 5 and an image processing unit 6 of the readout object 7 connected to it.

The light guide 2 (figure 1) is a sequentially mounted tetrahedral 8 - the first prism and a trihedral rectangular 9 - the second prism with a gap 10 between them. The tetrahedral prism 8 has an input 11, two reflective - 12 and 13, and an output 14 of the face. On the input face 11 there is a section 15 for placing on it an object of reading 7 - a carrier of graphic and text information.

The lighter 1 of the reading object 7 is one or more pairs of rulers 16 of light sources, preferably LEDs, which are installed (Fig. 2) pairwise symmetrically near the side faces 17 and 18 of the tetrahedral prism 8 or near sections 19 and 20 of the output face 14 symmetrically with respect to the trihedral prism 9, the width of which is less than the width of the tetrahedral prism 8. Pairs of rulers 16 of light sources can be installed in both of these places.

At the tetrahedral prism 8, the reflecting face 12 adjacent to the plot 15 for receiving the reading object 7 is comparable with it and forms an acute angle with the input face 11, which ensures complete internal reflection from it by the returned face line 12 of the line of sight. The reflecting face 13 of the opposite input face 11 forms an optical wedge with it, with the base mating with the edge of the reflecting face 12.

The angle of the optical wedge between the input 11 and the reflecting 13 faces, the obtuse angle between the input 11 and the output 14 faces, as well as the lengths of all the faces of the tetrahedral prism 8 are selected to be minimal from the condition that the line of sight reflects from them three times and falls onto the output face 14 and mated with it input hypotenuse face 21 of a rectangular prism 9 at an angle close to normal.

One cathete face 22 of a rectangular prism 9, located in the same plane as the input face 11 of the tetrahedral prism 8, forms an angle with the hypotenuse face 21, which provides full internal reflection of the hypotenuse face 21, reflected by the cathet face 22 of the returned line of sight and its drop on the output - another cathet face 23 of a rectangular prism 9 at a normal angle.

The reflecting faces 12 and 13 of the tetrahedral prism 8 and the reflecting cathet face 22 of the rectangular prism 9 are expediently made mirror.

A negative plane-concave lens 3 is installed behind the exit face 23 of the rectangular prism 9, with the center pupil of the spherical surface of which on the line of sight is the entrance pupil of the lens 4, in the image plane of which there is an array photodetector 5 connected to the image processing unit 6 of the reading object 7.

The lateral faces 17 and 18 of the tetrahedral prism 8 and / or sections 19 and 20 of its output face 14, depending on where the line of 16 LEDs will be installed, it is advisable to make matte with the exception of local sections on them, interfaced with the light sources of the lines 16.

Section 15 to accommodate the reading object 7 on the input face 11 of the tetrahedral prism 8, it is advisable to provide installed with a gap protective glass 24 in the form of a plane-parallel plate.

A rotary mirror 25 can be installed between the negative lens 3 and the lens 4 to reduce the longitudinal dimensions of the device along the length.

A device for reading graphic and text information works as follows.

The radiation of the LEDs of the rulers 16 passing through the non-attenuating light fluxes of the polished sections of the matte surfaces, for example, the side faces 17 and 18 of the tetrahedral prism 8, undergoing multiple reflections inside the prism, including from the matte surfaces, creates uniform diffuse illumination of the portion 15 for accommodating the reading object 7 and, accordingly, placed on the protective glass 24 of the reading object 7 itself.

The beam of rays, and, accordingly, the line of sight from the illuminated reading object 7, located in the objective plane of the lens 4, passing through the protective glass 24 and the input face 11 of the tetrahedral prism 8, is reflected from the adjacent face 15 of the face 12 towards the input face 11 at an angle providing full internal reflection from it.

After the second reflection from the face 11, the beam falls on the reflecting face 13 and, reflected from it (third reflection), is directed at an angle close to normal to the output face 14 of the tetrahedral prism 8. Next, the light beam passes through the output face 14 of the first prism 8 and the input hypotenuse face 21 of the second prism 9 mating with it, is reflected from its cathet face 22, falls onto the hypotenuse face 21 at an angle providing full internal reflection from it. Reflected, the beam of rays through the output cathete face 23 at a normal angle leaves the prism system. Next, the beam of rays passes through a negative plane-concave lens 3, which reduces the angle of convergence of the beam, and after the pivoting mirror 25 is focused by the lens 4 in the image plane - on the photodetector 5, creating an image of the readable object 7.

From the matrix photodetector 5, the signal enters the image processing unit 6, where the subsequent processing of the read image takes place.

The angle between the faces 11 and 12 of the prism 8 and the length of the face 12 is selected from the condition of ensuring the minimum thickness of the tetrahedral prism 8 and ensuring full internal reflection by the input face 11 of the beam returned to it. Due to this, the developed prism system (fiber 2) has a height less than the smallest linear size of the document being read, and due to the multiple reflection of the beam in the prisms, it increases the optical path length of the beam, which, in turn, reduces the length of fiber 2 and reduces the requirements to lens quality 4.

The entire readable document is in the field of view of the optical system of the device, which eliminates the need for scanning and increases the speed of its reading.

The sight line in the optical system of the device is perpendicular to the plane of the read document 7, which allows you to get an image of the read document 7 on the matrix photodetector 5 without geometric distortions, which, in turn, simplifies and speeds up the subsequent processing of the image of the read document, at the same time simplifies and cheapens the image processing unit 6 reading object.

In the prototype of the inventive device for reading text and graphic information as components, a ruler with L-314LWC LEDs from PARA LIGHT ELECTRONICS CO, Ltd, Taiwan, a lens model TV Lens F1,4-16 from ERNITEC were used as illuminators , Denmark, as the receiver - a matrix photodetector with an image processing unit for the reading object model MAA-3150LC-U, ZAO Ista-tehnika, Russia. Tests of the prototype showed that the time of reading and recognition of the image of the passport is less than 1 s.

Thus, it is seen that the above information confirms the possibility of implementing the claimed invention, achieving the specified technical result and solving the problem.

Claims (4)

1. A device for reading graphic and textual information, including a illuminator, a fiber-optic cable sequentially mounted with an optical communication section with a reading object, a lens, a photodetector array and an image processing unit of a reading object connected to it, characterized in that the fiber is made in the form of two in series with a gap established prisms - tetrahedral with a site for the location of the reading object and a smaller triangular rectangular; the illuminator is made in the form of at least one pair of rulers of light sources installed symmetrically near the opposite side faces of the tetrahedral prism and / or near its exit face symmetrically with respect to the trihedral prism; for a tetrahedral prism, the reflecting face adjacent to the site for the reading object is commensurate with it and forms an acute angle with the input face, providing full internal reflection of the line of sight returned to it; and the reflecting face opposite the input forms an optical wedge with it; in this case, other angles between the faces of the tetrahedral prism and their lengths are selected from the condition of triple reflection of the line of sight from it and its fall on the output face and the input hypotenous face of the rectangular prism, which is at an angle close to normal, located at an obtuse angle to the input one, and the parameters of a rectangular prism are selected from the condition of reflection of the line of sight from its first leg, placed in the same plane as the input face of the first prism, the second total internal reflection from the input hypotenuse face and falling on the output second cathete face at a normal angle; at the same time, an additional negative plane-concave lens is installed between the lens and the output face of the rectangular prism, with the center pupil of the spherical surface of which on the line of sight is the entrance pupil of the lens, in the image plane of which an array photodetector is installed. 2. The device according to claim 1, characterized in that the side faces and / or the illuminated portions of the output face of the tetrahedral prism are made opaque, with the exception of local portions on them, mating with light sources. 3. The device according to claim 1 or 2, characterized in that the plot for accommodating the reading object is equipped with a protective glass installed with a gap in the form of a plane-parallel plate. 4. The device according to claim 1 or 2, characterized in that a rotary mirror is installed between the negative lens and the lens.

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