Patent Description:
Fingerprint is commonly used in electronic devices for verification or authentication of personal identity. It is desirable to have quick and accurate recognition of the fingerprint. Among many sensing techniques that have been widely developed, under-display sensing is one of the promising techniques used in fingerprint recognition. Sensing device utilizing such technique includes a fingerprint sensing module that is disposed under a touch screen. However, the position of the fingerprint sensing module in this type of sensing device makes the sensing light to be easily interfered or influenced by the touch screen, resulting in low sensitivity, low resolution and slow recognizing speed.

Referring to <FIG>, a conventional under-display sensing device for generating three dimensional fingerprinting data is disclosed in <CIT>. The sensing device includes an array of pixels <NUM> serving as a light source, an optical image sensor <NUM> disposed under the pixels <NUM>, a first optically clear adhesive (OCA) layer <NUM> disposed above the optical image sensor <NUM>, a transparent support member <NUM> disposed above the first OCA layer <NUM>, a pin hole array mask layer <NUM> spaced from the optical image sensor <NUM> by the transparent support member <NUM> and disposed under the pixels <NUM>, a display encapsulation layer <NUM> covering the pixels <NUM>, a second OCA layer <NUM> disposed over the display encapsulation layer <NUM>, a transparent cover layer <NUM> disposed over the second OCA layer <NUM> and defining a finger placement surface, and optionally a light source <NUM> for directing light to a user's finger <NUM> or directing light to the optical image sensor <NUM>. In particular, the pin hole array mask layer <NUM> has a plurality of openings <NUM> to permit light passing therethrough. When the user's finger <NUM> contacts the finger placement surface, a light from the pixels <NUM> is reflected by the finger <NUM>, then passes through the openings <NUM> of the pin hole array mask layer <NUM>, and finally is captured by the optical image sensor <NUM> for sensing. The image resolution may be controlled by adjusting the spacing between the openings <NUM>, the diameter of each opening <NUM>, and the thickness of the transparent support member <NUM> and the transparent cover layer <NUM>, thereby increasing the resolution of the fingerprinting data. Moreover, the pin hole array mask layer <NUM> may further include lenses (not shown in <FIG>) in the openings <NUM> to improve image quality and signal-to-noise ratio (SNR).

The man skilled in the art knows also Patent Application <CIT>, which discloses a liquid crystal display panel using an OLED light-emitting screen body as a backlight assembly.

Despite the rapid development of fingerprint recognition, there is still a need for further improvement in the sensitivity of fingerprint sensing method.

Therefore, an object of the disclosure is to provide a method for detecting a biometric object that can alleviate at least one of the drawbacks of the prior art.

This goal is achieved by the method according to claim <NUM>.

Referring to <FIG> and <FIG>, an embodiment of a method for sensing a biometric object <NUM> (such as a finger) using an electronic device is provided. The electronic device includes a liquid crystal display (LCD) <NUM>, an optical sensing unit <NUM> disposed under the LCD <NUM> and a housing (not shown in the figures). The LCD <NUM> and the optical sensing unit <NUM> of the electronic device are integrated into the housing.

The LCD <NUM> includes a first transparent substrate <NUM>, a second transparent substrate <NUM> spaced apart from the first transparent substrate <NUM>, a liquid crystal layer <NUM> disposed between the first and second transparent substrates <NUM>, <NUM>, a backlight unit <NUM> disposed at a side opposite to the liquid crystal layer <NUM> for emitting a sensing light, and a control unit <NUM>. The first transparent substrate <NUM> includes a display surface <NUM> opposite to the liquid crystal layer <NUM> and has a sensing region <NUM> for recognizing the biometric object <NUM>. Taking mobile phone as an example, the sensing region <NUM> maybe a region of the home button for fingerprint recognition of the biometric object <NUM>. A polarizing film, which is configured to polarize light, may be formed on each of the first and second transparent substrates <NUM>, <NUM> (not shown in <FIG> and <FIG>).

The LCD <NUM> also includes a color filter unit <NUM> formed on the first transparent substrate <NUM> opposite to the display surface <NUM>. That is, the color filter unit <NUM>, the liquid crystal layer <NUM> and the backlight unit <NUM> are sequentially disposed under the display surface <NUM> in such order. The color filter unit <NUM> includes multiple color filters that contain at least two groups of color filters for filtering different colors of light. For example, the color filter unit <NUM> may include a first group of the color filters that is transparent to red light (simply referred to as red light filter 214R), a second group of the color filters that is transparent to green light (simply referred to as green light filter <NUM>), and a third group of the color filters that is transparent to blue light (simply referred to as blue light filter 214B).

The LCD <NUM> further includes a common electrode <NUM> formed on the color filter unit <NUM> opposite to the first transparent substrate <NUM>, and a plurality of pixel electrodes <NUM> formed on the second transparent substrate <NUM> opposite to the backlight unit <NUM>. The arrangement of the liquid crystal molecules <NUM> can be controlled by applying voltages between the common electrode <NUM> and the pixel electrodes <NUM>. Moreover, the control unit <NUM> includes a first control circuit <NUM> connected between the common electrode <NUM> and the pixel electrodes <NUM> for controlling arrangement of the liquid crystal molecules <NUM>, and a second control circuit <NUM> for controlling the backlight unit <NUM> to emit a sensing light L1. It should be noted that the structure, material and operation of each components of the LCD <NUM> are well known to a person skilled in the art, and thus a detailed description thereof is omitted herein for brevity.

The optical sensing unit <NUM> includes a circuit board <NUM>, a plurality of optical sensing chips <NUM> disposed on the circuit board <NUM>, a plurality of film transistors (not shown) electrically connected to the optical sensing chips <NUM>, and a control circuit <NUM> electrically connected to the circuit board <NUM>. The film transistors are communicatively connected to the control circuit <NUM> via the circuit board <NUM> and may control the signal transmission of the optical sensing chips <NUM> via the control circuit <NUM>. In certain embodiments, a projection of the optical sensing unit <NUM> is located at the sensing region <NUM> on the display surface <NUM>. The optical sensing chips <NUM> may be one of a charge-coupled device (CCD) and a complementary metal-oxide semiconductor (CMOS).

It should be noted that the control circuit <NUM> and the control unit <NUM> may be provided independently, or the control circuit <NUM> may be integrated into the control unit <NUM> of the LCD <NUM>. As shown in <FIG>, the control circuit <NUM> and the control unit <NUM> of the LCD <NUM> are provided independently.

According to this disclosure, the embodiment of the method for sensing the biometric object <NUM> using the abovementioned electronic device includes steps (a) and (b). In this embodiment, the electronic device is a mobile phone and the biometric object <NUM> is a user's finger for fingerprinting.

First, referring to <FIG>, in step (a), a sensing light L1 is emitted from the backlight unit <NUM> when the biometric object <NUM> contacts the sensing region <NUM> on the display surface <NUM>. The sensing light L1 is allowed to pass through the color filter unit <NUM> and then reach and be reflected by the biometric object <NUM> to return as a reflected light L2.

Referring to <FIG>, in step (b), the arrangement of the liquid crystal molecules <NUM> located in a first region of the liquid crystal layer <NUM> is controlled to define a first light path. The first region is underneath the sensing region <NUM> of the display surface <NUM> and corresponds in position to the color filter unit <NUM>. The reflected light L2 having predetermined wavelengths is allowed to pass through the color filter unit <NUM> and the first light path to reach and be detected by the optical sensing unit <NUM>. Specifically, the reflected light L2 passes through at least one group of the color filters 214R, <NUM>, 214B located in a position corresponding to the first region of the liquid crystal layer <NUM> and the first light path, and then reaches and is detected by the optical sensing unit <NUM>. In this embodiment, the color filter unit <NUM> includes three groups of color filters 214R, <NUM>, 214B for filtering red, green and blue colors of light, respectively, and in step (b), the arrangement of the liquid crystal molecules <NUM> located in the first region (i.e., corresponding in position to the green light filter <NUM> underneath the sensing region <NUM> of the display surface <NUM>) is controlled by the first control circuit <NUM>. As such, the reflected light L2 having the predetermined wavelengths ranging from <NUM> to <NUM> (i.e., green light) is allowed to pass through the green light filter <NUM> underneath the sensing region <NUM> of the display surface <NUM> and the first light path, and then reaches and is detected by the optical sensing unit <NUM>.

In certain embodiments, the arrangement of the liquid crystal molecules <NUM> located in a remaining region of the liquid crystal layer <NUM> other than the first region is also controlled by the first control circuit <NUM>. As shown in <FIG>, the remaining region of the liquid crystal layer <NUM> includes a non-detected region not underneath the sensing region <NUM> of the display surface <NUM>, and a region corresponding in position to the blue light filter 214B underneath the sensing region <NUM> of the display surface <NUM>. With such arrangement, the reflected light L2 that does not have the predetermined wavelengths and that passes through the remainder of these groups of the color filters 214R, <NUM>, 214B (i.e., the red light filter 214R and blue light filter 214B) and the remaining region is blocked (e.g., by the polarizing film) and cannot reach and be detected by the optical sensing unit <NUM>. Therefore, only the reflected light L2 having a wavelength range of green light is capable of passing through the LCD <NUM> and being detected by the optical sensing unit <NUM>, thereby increasing the detection sensitivity.

In certain embodiments, step (a) includes controlling the arrangement of the liquid crystal molecules <NUM> located in a second region of the liquid crystal layer <NUM> to define a second light path, and allowing the sensing light L1 emitted from the backlight unit <NUM> to pass through the second light path and the color filters 214R, <NUM>, 214B located in a position corresponding to the second region of the liquid crystal layer <NUM> so as to reach the biometric object <NUM>. The second region covers the first region. As shown in <FIG>, the second region includes a first region corresponding in position to the green light filter <NUM> underneath the sensing region <NUM> of the display surface <NUM>, and a region corresponding in position to the color filters (i.e. blue light filter 214B) underneath the sensing region <NUM> of the display surface <NUM>. That is, the sensing light L1 passing through the green light filter <NUM> and the blue light filter 214B underneath the sensing region <NUM> of the display surface <NUM> reaches the biometric object <NUM>. Alternatively, the second region may be the same as the first region, and thus the first light path is the same as the second light path, such that the sensing light L1 reaching the biometric object <NUM> may have similar wavelengths to the reflective light L2 to be detected by the optical sensing unit <NUM>. For example, only the green light is capable of reaching the biometric object <NUM> and being detected by the optical sensing unit <NUM>, thereby reducing the interference of light having undesired wavelengths so as to further improve the detection sensitivity.

In certain embodiments, in step (a), the liquid crystal molecules <NUM> located in the non-detected region other than the second region is also controlled such that the sensing light L1 that passes through the non-detected region is blocked (e.g., by the polarizing film) and is not emitted outside of the LCD <NUM>.

To sum up, by virtue of using the color filter unit <NUM> and controlling of the arrangement of the liquid crystal molecules <NUM>, only filtered light with predetermined wavelengths reaches the optical sensing unit <NUM> for sensing and the interference of the reflected light L2 that does not have the predetermined wavelengths can be reduced. Thus, the sensitivity of the method for sensing of this disclosure, which is performed using the electronic device is improved.

Claim 1:
A method for sensing a biometric object (<NUM>) using an electronic device, the electronic device including a liquid crystal display, LCD (<NUM>) and an optical sensing unit (<NUM>) disposed under the LCD (<NUM>), the LCD (<NUM>) including a display surface (<NUM>) having a sensing region (<NUM>) for the biometric object (<NUM>), and a color filter unit (<NUM>) including a horizontal array of color filters that contains at least two groups of color filters (214R, <NUM>, 214B), each one of the groups of color filters (214R, <NUM>, 214B) being adapted for exclusively allowing a light of a specific wavelength range, which is different from wavelength ranges of the others of said groups, to pass through, a liquid crystal layer (<NUM>) containing a plurality of liquid crystal molecules (<NUM>), and a backlight unit (<NUM>) vertically and sequentially disposed under the display surface (<NUM>) in such order, the method comprising the step of:
a) emitting a sensing light (L1) from the backlight unit (<NUM>) upon the biometric object (<NUM>) contacting the sensing region (<NUM>) on the display surface (<NUM>), and allowing the sensing light (L1) to pass through the color filter unit (<NUM>) and then reach and be reflected by the biometric object (<NUM>) to return as a reflected light (L2);
characterized by the step of:
b) controlling arrangement of the liquid crystal molecules (<NUM>) located in a first region of the liquid crystal layer (<NUM>) to define a first light path, the first region being underneath the sensing region (<NUM>) of the display surface (<NUM>) and vertically corresponding in position to a specific one (<NUM>) of the at least two groups of the color filters (214R, <NUM>, 214B) of the color filter unit (<NUM>), and by said controlling, allowing the reflected light (L2) having predetermined wavelengths to pass through the specific one (<NUM>) of the at least two groups of the color filters (214R, <NUM>, 214B) and the first light path to reach and be detected by the optical sensing unit (<NUM>) and at the same time controlling the liquid crystal molecules located in a remaining region of the liquid crystal layer (<NUM>) other than the first region such that the reflected light (L2) that has wavelengths other than the predetermined wavelengths and that passes through the remainder of the at least two groups of the color filters (214R, <NUM>, 214B) and the remaining region is blocked from reaching and being detected by the optical sensing unit (<NUM>).