Method for detecting object on an operation interface of a touchable device and touchable device using the same

• US 8,934,681 B2
• Filed: 11/01/2011
• Issued: 01/13/2015
• Est. Priority Date: 02/23/2011
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Lin, Yao-Hsuan, Wu, Chih-Yen
• Primary Examiner(s): Desire, Gregory M
• Application Number:
  US13/286,805
• Publication Number:
  US 20120212452A1
• Time in Patent Office: 1,169 Days
• Field of Search: 345/163, 345/175, 345/204, 382/124
• US Class Current: 382/124
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0425 using a single imaging device like a video camera for tracking the absolute position of a single or a plurality of objects with respect to an imaged reference surface, e.g. video camera imaging a display or a projection screen, a table or a wall surface, on which a computer generated image is displayed or projected tracking a projected light spot to determine a position on a display surface G06F3/0386

Abstract

A method for detecting an object and a touchable device are presented, which is capable of detecting an object having a fingerprint feature on an operation interface of the touchable device. An image sensor is used for acquiring acquiring an image on the operation interface, and the acquired image is converted into a signal denoted in a frequency domain by using a frequency conversion function. Signals at a medium-high frequency (MHF) signal region among the signals of the frequency domain are analyzed, so as to generate a first signal and a second signal according to a distribution of the signals of the frequency domain. The first signal indicates existence of the object on the operation interface, and the second signal indicates inexistence of the object on the operation interface.

Claims

1. A method for detecting a object, applicable to a touchable device, for detecting the object having a fingerprint feature and placed on an operation interface of the touchable device, comprising:

acquiring, by an image sensor of the touchable device, an image on the operation interface;

converting, by a processor of the touchable device, the acquired image in a spatial domain into a signal of a frequency domain by using a frequency conversion function; and

generating a first signal and a second signal according to a distribution of the signals of the frequency domain in a medium-high frequency (MHF) signal region, wherein the first signal indicates existence of the object on the operation interface, and the second signal indicates inexistence of the object on the operation interface.

2. The method according to claim 1, wherein the analyzing step comprises:

calculating energy of signals in the MHF signal region;

comparing the calculated energy of the signals with a threshold value; and

generating the first signal when the energy of the signals is greater than the threshold value.

3. The method according to claim 2, wherein the calculating step comprises:

equally dividing the signals of the frequency domain into N×

N regions, wherein N is an integer greater than 1; and

defining K×

K regions within the scope of the N×

N regions, wherein K is a positive integer smaller than N;

calculating energy of the signals, other than signals in K×

K regions, at an upper left corner of the N×

N regions.

4. The method according to claim 1, wherein the analyzing step comprises:

calculating a number of the signals at the MHF signal region;

comparing the calculated number with a threshold value;

generating the first signal when the number is greater than the threshold value; and

generating the second signal when the number is not greater than the threshold value.

5. The method according to claim 1, wherein the frequency conversion function is one selected from Discrete Fourier Transform (DFT) function, a Discrete Cosine Transform (DCT) function, and a Discrete Wavelet Transform (DWT) function.

6. The method according to claim 1, further comprising:

when the object exists on the operation interface, calculating a displacement amount of the object by using the acquired image in response to the first signal.

7. The method according to claim 1, further comprising:

when the object exists on the operation interface, enabling a displacement sensor of the touchable device to output a displacement amount corresponding to a movement track of the object according to the first signal.

8. A touchable device, comprising:

an operation interface;

an image sensor, configured corresponding to the operation interface, and for acquiring an image on the operation interface, the acquired image being in a spatial domain;

a processor, connected to the image sensor, and for determining whether an object having a fingerprint feature exists on the operation interface by converting the acquired image into a signal of a frequency domain and analyzing frequency components of the acquired image; and

a track detector, connected to the processor, and for detecting a movement track of the object on the operation interface.

9. The touchable device according to claim 8, wherein the processor converts the acquired image into the signal of the frequency domain by using a frequency conversion function, and determines whether the object exists on the operation interface according to energy of the signals of the frequency domain in a medium-high frequency (MHF) signal region.

10. The touchable device according to claim 9, wherein the processor compares the energy of the signals in the MHF signal region with a threshold value, and determines that the object exists on the operation interface when the energy of the signals is greater than the threshold value.

11. The touchable device according to claim 8, wherein the processor converts the acquired image into the signal of the frequency domain by using a frequency conversion function, and determines whether the object exists on the operation interface according to a number of signals of the frequency domain in an MHF signal region.

12. The touchable device according to claim 11, wherein the processor compares the number of the signals located at the MHF signal region with a threshold value, and determines that the object exists on the operation interface when the number of the signals is greater than the threshold value.

13. The touchable device according to claim 8, wherein when the object exists on the operation interface, the processor enables the track detector to detect the movement track of the object.

14. The touchable device according to claim 8, wherein the track detector is a displacement sensor.

15. The touchable device according to claim 8, wherein the track detector is an image sensor.

16. A touchable device, comprising:

an operation interface;

an image sensor, configured corresponding to the operation interface, and for acquiring an image on the operation interface, the acquired image being in a spatial domain; and

a processor, connected to the image sensor, for determining whether an object having a fingerprint feature exists on the operation interface by converting the acquired image into a signal of a frequency domain and analyzing frequency components of the acquired image, and calculating a displacement amount of the object by using the acquired image when the object exists on the operation interface.

17. The touchable device according to claim 16, wherein the processor converts the acquired image into the signal in the frequency domain by using a frequency conversion function, and determines whether the object exists on the operation interface according to energy of signals in the frequency domain in a medium-high frequency (MHF) signal region signals of the frequency domain.

18. The touchable device according to claim 17, wherein the processor compares the energy of the signals located at the MHF signal region with a threshold value, and determines that the object exists on the operation interface when the energy of the signals is greater than the threshold value.

19. The touchable device according to claim 16, wherein the processor converts the acquired image into the signal in the frequency domain by using a frequency conversion function, and determines whether the object exists on the operation interface according to a number of signals in the frequency domain in an MHF signal region.

20. The touchable device according to claim 19, wherein the processor compares the number of the signals located at the MHF signal region with a threshold value, and confirms that the object exists on the operation interface when the number of the signals is greater than the threshold value.