1-10. (canceled)
11. A method of driving a photosensitive device including at least one photosensitive pixel with a photodiode connected to a switching element, comprising:
subjecting the photosensitive pixel during a read phase to a cycle of successive images including a useful image preceded by at least one offset image produced at an initial instant; and
applying a correction established during a calibration phase to the useful image, the correction being based on the offset image taken at the initial instant and on a time separating the useful image from the offset image taken at the initial instant, and wherein the calibration phase precedes the read phase.
12. The method as claimed in claim 11, wherein, in the calibration phase, the method comprises taking plural pairs of offset images, two images of each pair being separated by a given time, the given times of the plural pairs being distributed within a usable time interval in the read phase, determining and then storing the difference between the second offset image and the first offset image of each pair, and then in the read phase subtracting a current offset image from the useful image, the current offset image depending on the offset image taken at the initial instant and on the stored difference corresponding approximately to the time separating the useful image from the offset image taken at the initial instant.
13. The method as claimed in claim 11, wherein, in the calibration phase, the method comprises taking plural pairs of offset images, two images of each pair being separated by a given time, the given times of the plural pairs being distributed within a usable time interval in the read phase, storing the second offset image of each pair, and then, in the read phase, subtracting the second offset image from a pair corresponding approximately to the time separating the useful image from the offset image taken at the initial instant.
14. The method as claimed in claim 12, wherein the current offset image is approximately equal to the offset image taken at the initial instant, from which is subtracted the stored difference conventionally chosen as being equal to the first offset image from which the second offset image is subtracted.
15. The method as claimed in claim 12, wherein, in the calibration phase, each offset image pair is preceded by an unused offset image and wherein, for all of the pairs, an approximately fixed time separates the unused offset image from the first offset image of the pair in question.
16. The method as claimed in claim 12, wherein, in the calibration phase, the difference between the second offset image and the first offset image is determined for each photosensitive pixel.
17. The method as claimed in claim 12, wherein, in the calibration phase, the difference between the second offset image and the first offset image is determined based on a mean level of each offset image.
18. The method as claimed in claim 12, wherein, in the calibration phase, the difference between the second offset image and the first offset image is determined based on a mean level of parts of each offset image.
19. The method as claimed in claim 11, further comprising taking a current offset image after the useful image and separated by a time from the useful image, the time corresponding to the time separating the useful image from the offset image taken at the initial instant, and then subtracting a current offset image from the useful image.
20. The method as claimed in claim 11, wherein a correction is applied to the useful image, said correction depending on a temperature at which the useful image is taken.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An operating circuit applied to a backlight, wherein the backlight comprises at least one lighting element, the lighting element comprises at least one lighting unit, and the operating circuit comprises:
at least one current control circuit, coupled to the lighting element, for controlling a current of the lighting element, wherein the current control circuit comprises:
a first transistor having a gate, a first electrode and a second electrode, wherein the first electrode is coupled to the lighting element, and the second electrode is coupled to a resistor;
an operational amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal; and
a switch module, coupled between the first transistor, the operational amplifier and a reference voltage, for switching a connection relationship between the positive input terminal, the negative input terminal, the reference voltage and the second electrode of the first transistor, and for switching a connection relationship between the positive output terminal, the negative output terminal and the gate of the first transistor to make the close loop form a negative feedback, and the current of the lighting element not influenced by an offset voltage of the operational amplifier.
2. The operating circuit of claim 1, wherein during a first period, the switch module is controlled to connect the positive input terminal of the operational amplifier to the reference voltage, and to connect the negative input terminal of the operational amplifier to the second electrode of the first transistor, and to connect the positive output terminal to the gate of the first transistor; and during a second period, the switch module is controlled to connect the positive input terminal of the operational amplifier to the second electrode of the first transistor, and to connect the negative input terminal of the operational amplifier to the reference voltage, and to connect the negative output terminal to the gate of the first transistor.
3. The operating circuit of claim 2, wherein the first period and the second period are active periods of two adjacent cycles of a pulse width modulation signal, respectively, and the pulse width modulation signal is utilized for controlling an enabling statedisabling state of the lighting element.
4. The operating circuit of claim 1, further comprising:
a second transistor having a gate, a first electrode and a second electrode, wherein the first electrode is coupled to the lighting element, and the second electrode is coupled to the first electrode of the first transistor; and
a first control voltage generating unit, coupled to the second transistor, for generating a first control voltage to the gate of the second transistor.
5. The operating circuit of claim 4, wherein when the lighting element is enabled, the first control voltage generating unit controls the second transistor to be operated in a triode region; and when the lighting element is disabled, the first control voltage generating unit controls the second transistor to be disabled.
6. The operating circuit of claim 1, further comprising:
a third transistor having a gate, a first electrode and a second electrode, wherein the first electrode is coupled to the lighting element, and the second electrode is coupled to the first electrode of the first transistor; and
a second control voltage generating unit, coupled to the third transistor, for generating a second control voltage to the gate of the third transistor according to a voltage level of the first electrode of the third transistor.
7. The operating circuit of claim 6, wherein the second control voltage generating unit comprises:
an analog-to-digital converter, for generating a digital signal according to the voltage level of the first electrode of the third transistor; and
a digital-to-analog converter, coupled to the analog-to-digital converter, for receiving the digital signal to generate the second control voltage.
8. The operating circuit of claim 1, wherein the lighting unit is a light-emitting diode (LED), and the lighting element is a LED string.
9. An operating method applied to a backlight, wherein the backlight comprises at least one lighting element, the lighting element comprises at least one lighting unit, and the operating method comprises:
providing at least one current control circuit coupled to the lighting element, wherein the current control circuit is utilized for controlling a current of the lighting element, and the current control circuit comprises:
a first transistor having a gate, a first electrode and a second electrode, wherein the first electrode is coupled to the lighting element, and the second electrode is coupled to a resistor;
an operational amplifier having a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal; and
switching a connection relationship between the positive input terminal, the negative input terminal, a reference voltage and the second electrode of the first transistor, and switching a connection relationship between the positive output terminal, the negative output terminal and the gate of the first transistor to make the close loop form a negative feedback, and the current of the lighting element not influenced by an offset voltage of the operational amplifier.
10. The operating method of claim 9, wherein a step of switching the connection relationship between the positive input terminal, the negative input terminal, the reference voltage and the second electrode of the first transistor, and switching the connection relationship between the positive output terminal, the negative output terminal and the gate of the transistor comprises:
during a first period, connecting the positive input terminal of the operational amplifier to the reference voltage, connecting the negative input terminal of the operational amplifier to the second electrode of the first transistor, and connecting the positive output terminal to the gate of the first transistor; and
during a second period, connecting the positive input terminal of the operational amplifier to the second electrode of the first transistor, connecting the negative input terminal of the operational amplifier to the reference voltage, and connecting the negative output terminal to the gate of the first transistor.
11. The operating method of claim 10, wherein the first period and the second period are active periods of two adjacent cycles of a pulse width modulation signal, respectively, and the pulse width modulation signal is utilized for controlling an enabling statedisabling state of the lighting element.
12. The operating method of claim 9, further comprising:
providing a second transistor having a gate, a first electrode and a second electrode, wherein the first electrode is coupled to the lighting element, and the second electrode is coupled to the first electrode of the first transistor; and
generating a first control voltage to the gate of the second transistor.
13. The operating method of claim 12, wherein a step of generating the first control voltage to the gate of the second transistor comprises:
when the lighting element is enabled, controlling the second transistor to be operated in a triode region; and
when the lighting element is disabled, controlling the second transistor to be disabled.
14. The operating method of claim 9, further comprising:
providing a third transistor having a gate, a first electrode and a second electrode, wherein the first electrode is coupled to the lighting element, and the second electrode is coupled to the first electrode of the first transistor; and
generating a second control voltage to the gate of the third transistor according to a voltage level of the first electrode of the third transistor.
15. The operating method of claim 14, wherein a step of generating the second control voltage to the gate of the third transistor according to the voltage level of the first electrode of the third transistor comprises:
generating a digital signal according to the voltage level of the first electrode of the third transistor; and
receiving the digital signal to generate the second control voltage.
16. The operating method of claim 9, wherein the lighting unit is a light-emitting diode (LED), and the lighting element is a LED string.