TW202032408A - Fingerprint image detection method in which a one-dimensional collimated light ray is used to detect and generate a fingerprint image for subsequent recognition of the fingerprint - Google Patents

Abstract

The present invention discloses a fingerprint image detection method, which uses at least a one-dimensional collimated detection light ray of a collimation light source to transmit into a light guide plate and uses amplified detection light to detect a fingerprint in order to generate a collimated fingerprint signal. The fingerprint signal is reduced in the light guide plate and the fingerprint signal so reduced and involving no reversed phase leaves the light guide plate from a bottom surface thereof. Then, after restoration of the fingerprint signal, recognition of the fingerprint can be performed to obtain a fingerprint image. By using the above solution, the present invention effectively fulfills the purpose of fingerprint recognition.

Description

Fingerprint image sensing method

The present invention relates to an image sensing technology, in particular to a fingerprint image sensing method using a collimated light source for sensing and identification.

Image recognition has a wide range of applications. The application of biometric recognition technology is closer to life, especially fingerprint recognition, which uses the unique fingerprint information on the human finger to recognize personal identity and achieve the purpose of controlling electronic equipment. Fingerprint recognition is widely used because of its advantages in security and convenience; currently, the most common smartphone with fingerprint recognition function is to use fingerprints to add and unlock.

The general optical fingerprint recognition technology mainly uses the incident light emitted by the light source into the light guide plate, so that the fingerprint signal generated by the finger is projected to the photosensitive element through the optical path. Because the wave peak of the fingerprint reflects light, the wave trough will absorb the light, so the reflection The formed fingerprint signal will form light and dark contrast stripes, so that the photosensitive element can achieve fingerprint recognition. Of course, fingerprint recognition is not limited to this. Based on this spirit, various fingerprint image sensing technologies have been developed.

US Patent US 2017/0255813 proposes an image sensor with a light guide plate. The image sensor system disclosed in it uses a volumetric holographic grating (VHG). As shown in Figure 1, multiple light waves 404 reflected by the thumb fingerprint 406 can be captured within an interval distance d from the surface of the light guide plate 408. The light waves 404 are diffracted from the volume holographic grating 402 and then pass through the light guide plate 408. Transmission, gradually converges and reverses phase, and then leaves from the side of the light guide plate 408 and is transmitted to the image sensor 410. The result image 403 sensed by the image sensor 410 is finally transmitted to the image processing circuit and software 412 for processing Shadow fingerprint recognition processing.

In conclusion, the present invention also proposes a fingerprint image sensing method to effectively achieve the function of fingerprint image sensing and identification.

The main purpose of the present invention is to provide a fingerprint image sensing method, which uses at least one-dimensional collimated sensing light to sense the fingerprint to generate a collimated fingerprint signal, and then reduce the fingerprint signal without inversion The bottom surface of the light guide plate is separated to achieve the optimized fingerprint recognition effect.

Another object of the present invention is to provide a fingerprint image sensing method, which can sense all or part of the area on the light guide plate, and the sensing range can be large or small, so designers can have more flexibility in selection and Meet the flexibility of users.

To achieve the above objective, the fingerprint image sensing method of the present invention includes the following steps: providing a collimated light source to generate at least one-dimensional collimated sensing light into a light guide plate; according to a fingerprint sensing range, in the light guide plate After enlarging the sensing light, make the sensing light correspond to a fingerprint to be recognized to generate a fingerprint signal; then, after the fingerprint signal is reduced in the light guide plate, it leaves from the bottom surface of the light guide plate.

The fingerprint signal connection mentioned above will go through the step of restoring the fingerprint signal, and then perform fingerprint image recognition processing on the restored fingerprint signal to obtain the final fingerprint image.

The following detailed descriptions are provided with specific embodiments and accompanying drawings, so that it is easier to understand the purpose, technical content and effects of the present invention.

The invention utilizes at least one-dimensional collimated sensing light generated by a collimated light source to enter the light guide plate to sense the fingerprint to be recognized on the light guide plate, so that the fingerprint signal obtained can be effectively self-guided through the optical path in the light guide plate The bottom of the light board is passed out for subsequent restoration and identification of fingerprint signals.

Figure 2 is a flowchart of the first embodiment of image sensing of the present invention. As shown in the figure, the fingerprint image sensing method of the present invention includes the following steps: First, as shown in step S10, a standard is provided. The straight light source can be selected from a one-dimensional collimated light source or a two-dimensional collimated light source. The collimated light source generates at least one-dimensional collimated light to enter a light guide plate, and the surface of the light guide plate is further provided with at least one fingerprint sensor The fingerprint sensing area is the entire area or partial area of the surface of the light guide plate for placing fingerprints to be recognized; as shown in step S11, the fingerprint sensing area provided by the fingerprint sensing area is in the light guide plate Amplify the sensing light, for example, using the optical element in the light guide plate to make the sensing light larger due to the characteristics of the optical element; as shown in step S12, the sensing light corresponds to the fingerprint to be recognized in the fingerprint sensing area on the light guide plate, and senses The light irradiates the fingerprint to be recognized and reflects it to generate a fingerprint signal; the fingerprint signal continues to travel in the light guide plate, and then as shown in step S13, after the fingerprint signal is reduced in the light guide plate, it leaves the light guide plate from the bottom surface of the light guide plate.

After the fingerprint signal leaves from the bottom surface of the light guide plate, as shown in step S14, the fingerprint signal is restored and enlarged to the original specification; finally, as shown in step S15, fingerprint image recognition processing is performed on the restored fingerprint signal to obtain a fingerprint image.

Figure 3 is a flowchart of the second embodiment of image sensing of the present invention. As shown in the figure, the fingerprint image sensing method of the present invention includes the following steps: First, as shown in step S20, one One-dimensional collimated light source, which produces one-dimensional collimated sensing light entering a light guide plate. The collimated dimension is the average transmission direction after entering the light guide plate. The surface of the light guide plate is provided with at least one fingerprint sensing area, and The fingerprint sensing area can be the entire area or a partial area of the surface of the light guide plate; then, as shown in step S21, in the light guide plate, in the collimated dimension, reflection amplification is used to sense light, for example, the optical characteristics of a mirror , The cross-sectional area of the reflected sensing light is enlarged and enlarged. At this time, the magnification and collimation are in the same dimension; and as shown in step S22, the sensing light corresponds to the fingerprint to be recognized in the fingerprint sensing area on the light guide plate, The sensing light will be reflected by the fingerprint to be recognized to generate a fingerprint signal; the generated fingerprint signal will continue to travel in the light guide plate, and then as shown in step S23, in the collimated dimension, the fingerprint signal is reduced by reflection, such as using a mirror The optical characteristics make the cross-sectional area of the reflected sensing light smaller and smaller. The reduced fingerprint signal leaves the light guide plate from the bottom surface of the light guide plate, and the aforementioned reduction and enlargement are in the same dimension. After the fingerprint signal leaves from the bottom surface of the light guide plate, as shown in step S24, the fingerprint signal is restored and enlarged to the original specification; finally, as shown in step S25, fingerprint image recognition processing is performed on the restored fingerprint signal to obtain a fingerprint image.

Figure 4 is a flowchart of the third embodiment of image sensing of the present invention. As shown in the figure, the fingerprint image sensing method of the present invention includes the following steps: First, as shown in step S30, a standard is provided. The straight light source can be selected from a one-dimensional collimated light source or a two-dimensional collimated light source. The collimated light source generates at least one-dimensional collimated light to enter a light guide plate, and the surface of the light guide plate is further provided with at least one Fingerprint sensing area, the fingerprint sensing area can be the entire area or partial area of the surface of the light guide plate for placing fingerprints to be recognized; as shown in step S31, according to the fingerprint sensing range provided by the fingerprint sensing area, The sensing light is amplified to a certain ratio in the light plate; then, as shown in step S32, the amplified sensing light corresponds to the fingerprint to be recognized in the fingerprint sensing area on the light guide plate, so that the sensing light irradiates the fingerprint to be recognized and is reflected to produce a fingerprint Signal; the generated fingerprint signal will continue to travel in the light guide plate, and then as shown in step S33, after the fingerprint signal is reduced in the light guide plate according to the ratio, for example, the area of the fingerprint sensing area on the light guide plate surface and Sensing the ratio of the cross-sectional area of the light to produce a reduced fingerprint signal, and then leaving the light guide plate from the bottom surface of the light guide plate. When the reduced fingerprint signal leaves the bottom surface of the light guide plate, as shown in step S34, the fingerprint signal is restored and enlarged to the original specifications; finally, as shown in step S35, the restored fingerprint signal is subjected to fingerprint image recognition processing to obtain The corresponding fingerprint image.

Figure 5 is a flowchart of the fourth embodiment of image sensing of the present invention. As shown in the figure, the fingerprint image sensing method of the present invention includes the following steps: First, as shown in step S40, a collimator is provided The light source can be selected from one-dimensional or two-dimensional collimated light sources. The collimated light source generates at least one-dimensional collimated light to enter a light guide plate, and the surface of the light guide plate is further provided with at least one fingerprint sensing area, The fingerprint sensing area can be the entire area or a partial area on the surface of the light guide plate for placing fingerprints to be recognized; as shown in step S41, the light guide plate continuously reflects and magnifies the sensing light according to a ratio, and the magnification ratio is the same as The area of the fingerprint sensing area, the angle of reflection and the thickness of the light guide plate are related; and as shown in step S42, the sensing light correspondingly irradiates the fingerprint to be recognized in the fingerprint sensing area on the light guide plate, and is reflected by the fingerprint to be recognized Generate a fingerprint signal; then the fingerprint signal will continue to travel in the light guide plate, and then as shown in step S43, according to the proportion of continuous reflection and reduction in the light guide plate, at least one-dimensional collimated fingerprint signal is generated from the light guide plate The bottom surface leaves the light guide plate. After the fingerprint signal leaves from the bottom surface of the light guide plate, as shown in step S44, the fingerprint signal is restored and enlarged to the original specifications; finally, as shown in step S45, the restored fingerprint signal is subjected to fingerprint image recognition processing to obtain the corresponding fingerprint image .

Among them, the collimation of the present invention may be one-dimensional collimation or two-dimensional collimation, and the dimension of the one-dimensional collimation is the average transmission direction of the fingerprint signal in the light guide plate. The allowable range of the collimation deviation in the forward direction of the sensing light or fingerprint signal is about ±0.25~±0.5 degrees, and the radial direction is not specifically limited (about ±10 degrees).

After describing the various implementation aspects of the fingerprint image sensing method of the present invention, the fingerprint image sensing device specific application of the present invention will be explained. As shown in Fig. 6, a fingerprint image sensing device 10 includes: The light guide plate 12 is provided with at least one fingerprint sensing area 121 on its surface. Here, a fingerprint sensing area is taken as an example, and the fingerprint sensing area 121 can be the entire area or a partial area of the surface of the light guide plate 12. For placing a fingerprint 20 to be recognized; a first reflector 123 is provided at the light entrance end 122 of the light guide plate 12, and a second reflector 125 is provided at the light exit end 124 of the light guide plate 12. A collimated light source 14 is arranged facing the bottom surface of the light entrance end 122 of the light guide plate 12, so that the collimated light source 14 can face the bottom surface of the light guide plate 12 to generate at least one-dimensional collimated sensing light. The collimated light source 14 can be One-dimensional collimated light source or two-dimensional collimated light source, such as laser (Laser) or vertical cavity surface shot laser (VCSEL), etc. When the collimated light source 14 generates a sensing light, the sensing light enters the light guide plate 12 from the light entrance 122, is reflected and amplified by the first reflector 123, and is incident on the fingerprint 20 to be recognized on the fingerprint sensing area 121. A fingerprint signal is generated after the identification fingerprint 20 is reflected. The fingerprint signal continues to travel in the light guide plate 12 toward the light-emitting end 124, and then is reflected and reduced by the second mirror 125. The reduced fingerprint signal follows the optical path from the bottom surface of the light guide plate 12 Leave the light guide plate 12. A restoration reflector 16 is further provided under the light emitting end 124 of the light guide plate 12, and the fingerprint signal leaving from the bottom surface of the light guide plate 12 travels to the restoration reflector 16, and the restoration reflector 16 is used to restore the fingerprint signal. Another image sensor 18 is arranged on the bottom surface of the light guide plate 12 and corresponds to the position of the restored reflector 16 to receive the restored fingerprint signal and perform fingerprint image recognition processing on the fingerprint signal to obtain a fingerprint image. The angles of the first reflector 123, the second reflector 125, and the restoration reflector 16 corresponding to the bottom surface of the light guide plate 12 depend on the ratio of the area of the fingerprint sensing area 121 to the cross-sectional area of the collimated light source 14.

Specifically, in the fingerprint image sensing device 10 of the actual case, the cross-sectional area of the collimated light source 14 is 1 mm * 1 mm, the fingerprint capturing area of the fingerprint sensing area 121 is 10 mm * 10 mm, and the image sensing The image captured by the device 18 is 6 mm * 4 mm (abandoning the fingerprint signal on the outer side). The angle between the first mirror 123, the second mirror 125, and the restoration mirror 16 and the front of the light guide plate 12 is 40 degrees (approximately enlarged Or 10 times), and the thickness of the side of the light guide plate 12 is 1 mm. These ranges are only specific cases of the present invention. When this is not a limitation, it still depends on actual needs.

Furthermore, if the angle between the first reflector 123 of the light incident end 122 and the bottom surface of the light guide plate 12 is 78 degrees, the reflection magnification will be close to 5 times, and two consecutive reflection magnifications can reach 25 times, which can greatly reduce the space required for the light source. . The second reflector 125 of the light-emitting end 124 is symmetrical to the light-incident end 122, which can reduce the space occupied by the fingerprint signal to 1/25 before leaving the light guide plate 12. The reduced fingerprint signal passes through the restored mirror 16 symmetrical to the second mirror 125 of the light emitting end 124, and is restored to the original size of the fingerprint signal on the receiving surface of the image sensor 18.

In summary, the fingerprint image sensing method proposed by the present invention uses an enlarged collimated light source for fingerprint sensing to generate a collimated fingerprint signal, and then the reduced fingerprint signal is separated from the bottom of the light guide plate to Provide follow-up restoration identification, and then achieve the best fingerprint identification effect. Therefore, the present invention uses a reduced fingerprint signal that is not inverted to leave from the bottom surface of the light guide plate. This technical feature is completely different from the aforementioned patents. In addition, the present invention can sense all or partial areas on the light guide plate. The measurement range can be large or small, so designers can have a wider range of design options and can meet the flexibility of users.

The above-mentioned embodiments are only to illustrate the technical ideas and features of the present invention. Their purpose is to enable those familiar with the art to understand the content of the present invention and implement them accordingly. When they cannot limit the scope of the present invention, that is, Any equivalent changes or modifications made in accordance with the spirit of the present invention should still be covered by the patent scope of the present invention.

10: Fingerprint image sensor 12: Light guide plate 121: Fingerprint sensing area 122: light end 123: The first mirror 124: light end 125: second mirror 14: Collimated light source 16: restore mirror 18: Image sensor S10~S15: steps S20~S25: steps S30~S35: steps S40~S45: steps 402: Volume Holographic Raster 404: Lightwave 403: result image 406: Thumb Fingerprint 408: light guide plate 410: Image Sensor 412: Image processing circuit and software d: separation distance

Figure 1 is a schematic diagram of the image sensing system disclosed in the previous US patent. Figure 2 is a flowchart of the first embodiment of image sensing in the present invention. FIG. 3 is a flowchart of the second embodiment of image sensing according to the present invention. FIG. 4 is a flowchart of the third embodiment of image sensing of the present invention. FIG. 5 is a flowchart of the fourth embodiment of image sensing according to the present invention. FIG. 6 is a schematic diagram of the structure of the fingerprint image sensing device used in the present invention.

Step: S10~S15

Claims (6)

A fingerprint image sensing method, which includes: Provide a collimated light source, which generates at least one-dimensional collimated sensing light and sensing light enters a light guide plate; Amplify the sensing light in the light guide plate according to a fingerprint sensing range; The sensing light corresponds to a fingerprint to be recognized and generates a fingerprint signal; and After reducing the fingerprint signal in the light guide plate, leave the light guide plate from the bottom surface of the light guide plate. The fingerprint image sensing method according to claim 1, further comprising: restoring the fingerprint signal. The fingerprint image sensing method according to claim 2, further comprising: performing image recognition processing on the restored fingerprint signal to obtain a fingerprint image. The fingerprint image sensing method according to claim 1, wherein the collimated light source is a one-dimensional collimated light source or a two-dimensional collimated light source. The fingerprint image sensing method according to claim 1, wherein the surface of the light guide plate is further provided with at least one fingerprint sensing area to provide the fingerprint sensing range. The fingerprint image sensing method according to claim 5, wherein the fingerprint sensing area is all or a partial area of the surface of the light guide plate.

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