CN100405391C - Living body fingerprint collecting method and apparatus - Google Patents

Abstract

The present invention relates to a method and device for collecting living finger and palm prints. A collection device consisting of a prism, a light source, a lens assembly, and an image sensor is used, and the collection surface of the prism is attached to the living finger and palm to be collected. A finger and palm print pattern is formed on the surface; the infrared light source is turned on, so that the light beam for collection enters the prism from the incident surface and is projected onto the palm print pattern, and the light beam for collection is reflected by the collection surface to form a The image beam of the palmprint pattern is output through the image output surface, and the wavelength range of the image beam is 700nm to 1100nm; the image beam is projected onto the image sensor through the lens assembly, and the image sensor converts the optical signal into Electrical signals to complete the collection of living finger and palm prints. The invention applies the color image sensor to the collection of photoelectric fingerprints and palm prints without the problems of chromatic aberration and image resolution reduction, and reduces product cost.

Description

A method for collecting living fingerprints and palm prints

technical field

The invention relates to a method and device for collecting living finger and palm prints. The method and device use a specific infrared light source for illumination and rely on an image sensor for signal conversion to realize the collection of living finger and palm prints.

Background technique

In the prior art, the commonly used photoelectric collection method of fingerprints and palmprints is realized by utilizing the total reflection characteristics of prisms. The prism has a light splitting effect. In order to avoid chromatic aberration from affecting the image quality of fingerprints and palmprints, a monochrome light source and a monochrome image sensor must be used. Generally, red light is used as the monochromatic light source, and some schemes use infrared light source. Chinese patent 94239537.9 discloses an infrared fingerprint identification device, which includes a housing, a camera and a computer. An isosceles right-angled prism with two slopes located in the housing is installed in the window hole of the housing panel, and a fingerprint image camera and infrared light are installed in the housing. The generator and an image processing board are respectively connected with the camera and the computer, and a group of fingerprint confirmation buttons are arranged on the casing. The infrared fingerprint identification device is simple in structure, and the collection, storage, transfer, comparison and identification of fingerprint images are fast, convenient and accurate. The purpose of using the infrared light source in this patent is to "provide the most sensitive light source for the camera with infrared light of a specific wavelength".

Generally speaking, monochrome image sensors are cheaper than color image sensors, and finger and palm print images are monochrome, so it is not necessary to conduct in-depth research on the application of color image sensors to optical live finger and palm print collection. With the rapid development of semiconductor image sensor technology, the popularity of digital cameras and digital video cameras has been driven. Since the market for color image sensors is much larger than that of monochrome image sensors, the emergence of mobile phones with camera functions has further stimulated the market demand for color image sensors. Therefore, manufacturers now mainly produce color image sensors, and the CMOS monochrome image sensors commonly used in optical fingerprint collection devices are difficult to find in the market, and their prices are higher than those of color. In order to solve these problems, some design schemes try to apply color image sensors with high market share and sufficient supply to optical fingerprint collection devices. These devices still use monochromatic visible light as the design scheme of the light source, generally red or green light is used as the light source. However, this brings about the problem of loss of image sensor resolution. Accompanying drawing 1 is a schematic diagram of pixel arrangement of a color image sensor, and the arrangement form is a Bayer pattern. Its green pixels account for 1/2 of all pixels, red and blue pixels each account for 1/4 of all pixels, and each color pixel only experiences light of one color. It can be seen from Figure 1 that there is a problem of sensor resolution reduction for monochrome images. When a green light source is used, only the green pixels are sensitive, and the image resolution is reduced to half of the sensor resolution; when a red or blue light source is used, only the red or blue pixels are sensitive, and the image resolution is reduced to the sensor resolution a quarter of. Therefore, need to propose a kind of new living body finger and palmprint collection method and device to solve the above problems.

Contents of the invention

The purpose of the present invention is to provide a method and device for collecting living finger and palm prints. The method adopts a specific infrared light source for illumination and a color image sensor for signal conversion, which can realize the collection of living finger and palm prints without loss of resolution. Filter films and sheets can eliminate the interference of visible light in the environment.

The purpose of the present invention is achieved by the following technical solutions: a living body finger and palm print collection method, using a collection device made of prism, light source, lens assembly, image sensor, is characterized in that:

The light source is an infrared light source, so that the infrared light source emits a monochromatic collection beam with a wavelength range of 700nm to 1100nm;

The prism has at least one light beam incident surface for collection, one image output surface, and one collection surface;

The collection surface of the prism is attached to the living finger and palm to be collected, and a finger and palm print pattern is formed on the collection surface;

Turn on the infrared light source so that the collection light beam enters the prism from the incident surface and is projected onto the finger and palm print pattern, and the collection surface reflects the collection light beam to form an image carrying the finger and palm print pattern The light beam is output through the image output surface;

The image light beam is projected onto the image sensor through the lens assembly, and the image sensor converts the optical signal into an electrical signal to complete the collection of living finger and palm prints.

A device for collecting living finger and palm prints has a housing, which is characterized in that: a prism is arranged on the top of the housing, and the prism has at least one light beam incident surface for collection, an image output surface, and a collection surface; One side of the surface is provided with an infrared luminescent plate, the normal line of the infrared luminescent plate is perpendicular to the incident surface of the light beam for collection, and a lens assembly is provided on the image output surface side, and an image sensor is provided at the output end of the lens assembly. The optical axis of the lens assembly is perpendicular to the image output surface; the infrared luminous plate, lens assembly and image sensor are installed in the housing.

Compared with the prior art, the present invention has the following advantages:

1. The present invention utilizes the spectral response characteristics of the color image sensor and uses near-infrared monochromatic light as the light source, so that the color image sensor can be applied to the collection of photoelectric fingerprints and palmprints without the problems of chromatic aberration and image resolution reduction.

2. The present invention avoids the influence of high price and unstable supply of monochrome image sensors, and reduces product cost.

3. The present invention uses infrared filter films and sheets to prevent the passage of visible light, eliminates the influence of ambient light and the interference of stains on the collection surface, and improves the quality of collected images.

Description of drawings

Figure 1 is a schematic diagram of the pixel arrangement of a color image sensor

Fig. 2 is a schematic diagram of embodiment one of the present invention

Figure 3 is the spectral response diagram of the color image sensor

Figure 4 is the spectral distribution diagram of infrared light-emitting diodes

Fig. 5 is a schematic view of the device structure of the present invention

Figure 6 is a longitudinal sectional view of the present invention

Fig. 7 is the plan view of the present invention (the view that cuts off the housing top)

Fig. 8 is the prism figure of the present invention

Fig. 9 is another kind of prism structure schematic diagram of the present invention

specific embodiment

Embodiment one:

A kind of collection method of living finger and palm print, referring to Fig. 2, uses a collection device that is made of prism 2, light source 1, lens assembly 4, image sensor 5, and its steps are:

The light source is an infrared light source, so that the infrared light source emits a monochromatic collection light beam with a wavelength range of 700nm to 1100nm; the infrared light source can use GL4910 infrared light-emitting tube products to form an array; the collection light beam refers to the collection of light emitted by the light source .

The prism has at least one light beam incident surface for collection, one image output surface, and one collection surface;

The collection surface of the prism is attached to the living finger and palm to be collected, and a finger and palm print pattern is formed on the collection surface; the so-called living finger and palm refer to human fingers, toes, palms, and soles of feet. The so-called finger and palm print patterns refer to people's hand fingerprint patterns, toe print patterns, palm print patterns, and foot print patterns.

Turn on the infrared light source so that the light beam for collection enters the prism from the incident surface and is projected onto the fingerprint pattern, the light beam for collection is reflected by the collection surface to form an image beam carrying the palmprint pattern and output through the image output surface, the wavelength of the image beam is in the range of 700nm to 1100nm;

The image light beam is projected onto the image sensor through the lens assembly, and the image sensor converts the optical signal into an electrical signal to complete the collection of living finger and palm prints. The lens assembly refers to a combination of multiple lenses capable of imaging, which belongs to the scope of the prior art, and will not be described in detail in this embodiment.

During the routine collection of living fingerprints and palmprints, the collection surface of the prism is often polluted and exposed to ambient light. The main component of its spectrum is in the visible light range. If it is not cleaned in time, the quality of the fingerprints and palmprints will be affected. For this reason, the present invention filters the output image beam (see the optical filter 3 provided in Figure 2), so that the infrared light of 850nm wavelength in the image beam passes through, forming an image beam of 850nm wavelength, preventing visible light from passing through, eliminating The influence of ambient light and the interference of smudges on the acquisition surface are eliminated.

In order to reduce the cost of the equipment used in the present invention, the present invention projects the image beam through the lens assembly onto the color image sensor, and the image sensor converts the light signal into an electrical signal; adjusts the red and green color of the color image sensor The gain of the three channels of blue and blue makes it have the same image signal output intensity for the same light within the wavelength range of 700nm to 1100nm.

Embodiment two:

Referring to Fig. 5, Fig. 6, Fig. 7, Fig. 8, a kind of living body finger and palmprint collection device has a housing 10, a collection window 11 is arranged on the top of the housing, a prism 12 is housed on it, and the prism has at least one collection window 10. With beam incidence surface 123, an image output surface 122, a collection surface 121; In said incidence surface one side is provided with infrared light-emitting plate 13, the normal line of this infrared light-emitting plate is orthogonal to collection with beam incidence surface (can also be provided with into a substantially orthogonal state), a lens assembly 14 is arranged on one side of the image output surface, an image sensor 15 is arranged at the output end of the lens assembly, and the optical axis of the lens assembly is orthogonal to the image output surface; the infrared The light emitting board, the lens assembly and the image sensor are installed in the housing. Referring to Fig. 8, the prism used in this embodiment is a polygonal prism, the collection surface of the prism is set on the top surface of the housing, the beam incident surface is set in the housing, the image output surface is set in the housing, and its output optical axis is in a horizontal state. Referring to FIG. 9 , the prism of the present invention can use another structural form, which is different from the prism structure shown in FIG. 8 , but its principle and function are the same.

In this embodiment, the infrared light-emitting boards are made of GL4910 infrared light-emitting tubes from SHARP Corporation of Japan to form an array. The surface of the infrared luminescent plate is provided with a uniform light plate, so that the infrared luminescent plate emits light uniformly and softly. Referring to Fig. 4, the peak emission wavelength of the infrared light-emitting diode is 850nm.

In this embodiment, either a monochrome image sensor or a color image sensor may be used. For the sake of cost reduction and ease of acquisition, the color image sensor OV9620 from Omnivision of the United States is the first choice. See Figure 3 for its spectral response. The red, green, and blue pixel sensitivity curves of this color image sensor have a peak at 840nm, and the sensitivity is similar . That is to say, for the same light, at 840nm, the red, green, and blue pixels of the entire sensor output signals with strong and close amplitudes, so that the pixels of the sensor are 100% utilized. When actually using a color CMOS digital image sensor, the gains of the three channels of red, green, and blue should be set so that they have the same signal output strength for the same light, so as to obtain the same effect as the monochrome image sensor.

In order to output the collected finger and palmprint patterns to the computer equipment, a USB interface circuit can be added in this embodiment.

The principle of finger and palmprint imaging in the present invention is: under the illumination of an infrared light source, when a finger or palm is pressed on the collection surface of a prism, the contact part of the skin texture and the surface destroys the total reflection condition of light, while the fingerprint or palmprint The valley part is not in contact with the collection surface of the prism, and the infrared light can still be totally reflected there, thus forming texture images with different brightness and darkness.

In order to improve the image quality of the present invention, an infrared transmission and visible absorption filter can be arranged on the element between the image output surface of the prism and the image sensor. In this embodiment, the image output surface of the prism and the lens assembly An infrared transmission and visible absorption filter (not shown in the figure) is arranged between the input ends, and an infrared bandpass filter can also be arranged on the element between the image output surface of the prism and the image sensor. This embodiment is An infrared bandpass filter is arranged between the image output surface of the prism and the input end of the lens assembly, and an infrared transmission and visible absorption filter can also be arranged on the element between the image output surface of the prism and the image sensor In this embodiment, an infrared-transmitting and visible-absorbing filter film is arranged between the image output surface of the prism and the input end of the lens assembly (the film can be plated on the mirror surface by a special process), and it can also be placed on the prism An infrared band-pass filter film is provided on the element between the image output surface of the lens assembly and the image sensor, or an infrared band-pass filter film is provided between the output end of the lens assembly and the image sensor (the film can be coated with a special process on the mirror surface).

Claims (3)

1. a living body fingerprint collecting method uses a harvester that is made of prism, light source, lens assembly, imageing sensor, it is characterized in that:

Described light source is an infrared light supply, makes infrared light supply send the monochrome collection light beam that wavelength coverage is 700nm～1100nm;

Described prism possesses a collection beam incident surface at least, an image output face, a collection face;

The collection face of described prism is fitted with the live body fingers and palms that will gather, on collection face, form fingers and palms line pattern;

Open described infrared light supply, make described collection enter described prism by the described plane of incidence and project on the described fingers and palms line pattern, will gather with light beam by collection face and reflect to form the image beam that is loaded with fingers and palms line pattern and export by described image output face with light beam;

Described image beam is projected on the imageing sensor by lens assembly, convert light signal to electric signal, finish the collection of living body fingerprint by this imageing sensor.

2. living body fingerprint collecting method according to claim 1 is characterized in that: with processings that filter of the image beam of described image output face output, the infrared light of 850nm wavelength in the image beam is passed through, the image beam of formation 850hm wavelength.

3. living body fingerprint collecting method according to claim 1 is characterized in that: described image beam is projected on the color image sensor by lens assembly, convert light signal to electric signal by this imageing sensor; Adjust the gain of three passages of red, green, blue of described color image sensor, make it in 700nm～1100nm wavelength coverage, identical picture signal output intensity is arranged for identical illumination.

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