Summary of the invention
Therefore, the object of the present invention is to provide a kind of active light sensing pixel, active light sensing array and light sensing method.
In one embodiment, provide a kind of active light sensing pixel, comprising: both-end point light sensing transistor, driving transistors and replacement electric capacity.Both-end point light sensing transistor has that the first end points is coupled to first node, the second end points is coupled to the selection signal wire, and the control end points is connected in the second end points.Driving transistors has that the first end points is coupled to the first reference voltage, the second end points is coupled to output signal line, and the control end points is connected in first node.Replacement electric capacity has the first end points and is connected in the transistorized control end points of both-end point light sensing, and the second end points is connected in first node.
In another embodiment, provide a kind of active light sensing array, having comprised: a plurality of signals are selected line, a plurality of output signal line and a plurality of active light sensing pixel.Each of active light sensing pixel comprises: both-end point light sensing transistor, driving transistors and replacement electric capacity.Both-end point light sensing transistor has that the first end points is coupled to first node, the second end points is coupled to corresponding selection signal wire, and the control end points is connected in the second end points.Driving transistors has that the first end points is coupled to the first reference voltage, the second end points is coupled to corresponding output signal line, and the control end points is connected in first node.Replacement electric capacity has the first end points and is connected in the transistorized control end points of both-end point light sensing, and the second end points is connected in first node.
A kind of light sensing method also is provided in addition, is applied to active light sensing pixel, active light sensing pixel comprises: both-end point light sensing transistor, driving transistors and replacement electric capacity.Both-end point light sensing transistor has that the first end points is coupled to first node, the second end points is coupled to the selection signal wire, and the control end points is connected in the second end points.Driving transistors has that the first end points is coupled to the first reference voltage, the second end points is coupled to output signal line, and the control end points is connected in first node.Replacement electric capacity has the first end points and is connected in the transistorized control end points of both-end point light sensing, and second end points be connected in first node, the light sensing method comprises the following steps: at exposure and readout interval, provide the first voltage quasi position to selecting signal wire, so that both-end point light sensing transistor is as diode; And when both-end point light sensing transistor receives incident light, produce diode current first node is charged, so that driving transistors is according to the voltage quasi position on the first node and conducting outputs current to output signal line in order to generation.
Above-described embodiment provides active light sensing pixel and its light sensing method.Compared to known passive type light sensing pixel, the light sensing pixel of above-described embodiment has higher signal to noise ratio (S/N ratio) and driving force, therefore can satisfy the demand of large area display.In addition, the control end of above-described embodiment driving transistors is to be connected to its second end points, so display can not be activated the impact of transistor critical voltage change.The light sensing pixel of above-described embodiment and array can be arranged at the lower plate of display, and replace known Charged Coupled Device (charge coupled device, CCD) optical sensor and CMOS optical sensor.
Description of drawings
The present invention can follow appended accompanying drawing and is understood with embodiment, and appended accompanying drawing also is the part of embodiment.Known skill person should be able to know that the present patent application claim should be assert to include embodiments of the invention and modification thereof largo, wherein:
Figure 1A is the synoptic diagram of transistorized the first operator scheme of both-end point light sensing among the embodiment;
Figure 1B shows among the embodiment both-end point light sensing transistor under the first operator scheme, the voltage V of the first end points
N1With the light sensing electric current I
PhotoRelation;
Fig. 2 A is the diagram of transistorized the second operator scheme of both-end point light sensing among the embodiment;
Fig. 2 B shows both-end point light sensing transistor Q among the embodiment
1Under the second operator scheme, double-pointed voltage V
N2Relation with diode current;
Fig. 3 is the synoptic diagram of active light sensing pixel among the embodiment;
Fig. 4 shows the sequential chart of selecting signal wire, and the voltage waveform of first node;
Fig. 5 is the synoptic diagram of the active light sensing pixel of an embodiment;
Fig. 6 is diagram and the corresponding sequential chart of signal wire of the active light sensing array of an embodiment;
Fig. 7 is diagram and the corresponding sequential chart of signal wire of the active light sensing of an embodiment and array of display.
[primary clustering symbol description]
Q
1~both-end point light sensing transistor;
Q
2~driving transistors;
Q
3~switching transistor;
V
H~high voltage;
V
L~low-voltage;
Hv~incident light;
I
Photo, I '
Photo~light sensing electric current;
I
Diode, I '
Diode~diode current;
U
11, U
12, U
13, U
21, U
22, U
23, U
31, U
32, U
33, U
41, U
42, U
43~active light sensing and display pixel;
P
11, P
12, P
13, P
21, P
22, P
23, P
31, P
32, P
33, P
41, P
42, P
43~active light sensing pixel;
S
22~display pixel;
Sel_1-Sel_4~selection signal wire;
Out_0-Out_3~output signal line;
Data_1-data_4~data signal line;
V
Ref1The~the first reference voltage;
V
Ref2The~the second reference voltage;
V
Ref3The~the three reference voltage;
X
1~first node;
V
X1, V '
X1, V
N1, V
N2~voltage;
V
GH~high levle driving voltage;
V
GL~low level driving voltage;
V
Th_Q1~critical voltage;
T
1~the period 1;
T
2~second round;
Creset~replacement electric capacity;
C
LC~liquid crystal capacitance;
C
Sensitivity~sensitivity adjustment electric capacity;
M
Photo-sensing~light sensing array;
M
Sensing-display~light sensing and array of display;
N
1: the first end points;
N
2: the second end points;
50~driving circuit;
51~sensing circuit;
52~data drive circuit.
Embodiment
Figure 1A is the synoptic diagram that the both-end point light sensing transistor among the embodiment operates in one first operator scheme (first operation mode).In the present embodiment, both-end point light sensing transistor Q
1Be N-type hydrogenation non crystal silicon film transistor (N-type a-Si:H TFT), but be not limited to this.Both-end point light sensing transistor Q
1Has the first end points N
1, the second end points N
2, and the control end points.Be noted that both-end point light sensing transistor Q
1The control end points be to be connected to the second end points N
2, and form whereby both-end point light sensing transistor Q
1Two end points, i.e. the first end points N
1Be connected in the second end points N
2The control end points.In the first operator scheme, both-end point light sensing transistor Q
1The first end points N
1Be applied in high voltage V
H, and the second end points N
2Be applied in low-voltage V
LShine the both-end point light sensing transistor Q that operates in the first operator scheme as incident light hv
1The time, both-end point light sensing transistor Q
1Can produce the light sensing electric current I
PhotoFlow to the second end points by the first end points.Generally speaking, light sensing electric current I
PhotoSize be by both-end point light sensing transistor Q
1Area and the material behavior of semiconductor layer determine.In addition, light sensing electric current I
PhotoSize also can be determined by the intensity of incident light hv; In other words, if the incident light intensity is stronger, light sensing electric current I then
PhotoAlso larger.Therefore, both-end point light sensing transistor Q
1In the first operator scheme as a photoresistance (photosensitive resistor).In another embodiment, both-end point light sensing transistor Q
1Also can be P type silicon thin film transistor (P-type Si TFT), but be not limited to this.In other embodiments, both-end point light sensing transistor Q
1Also can 0 be two-carrier junction transistor (BJT) or other switch module.
Figure 1B shows both-end point light sensing transistor Q
1When operating in the first operator scheme, the voltage V of the first end points
N1With the light sensing electric current I
PhotoRelation.As shown in Figure 1B, when not having incident light hv irradiation (rhombus dotted line), the light sensing electric current I '
PhotoIt is zero (being called again cut-off region).On the contrary, when incident light hv when irradiation (square dotted line) is arranged, with known field-effect transistor (FET) similarly, the light sensing electric current I
PhotoPlay first meeting and present linear increasing, then increasing degree diminishes (being called again triode region) gradually, and levels off at last saturated (being called again the saturation region).In one embodiment, if both-end point light sensing transistor Q
1Shone by incident light and the voltage V of the first end points
N1Be 16V, then the light sensing electric current I
PhotoBe about the 7.5E-09 ampere; If both-end point light sensing transistor Q
1Do not shone by incident light and the voltage V of the first end points
N1Be 16V, then the light sensing electric current I '
PhotoIt is 0 ampere.As both-end point light sensing transistor Q
1When operating in the first operator scheme, by detected light current sensor Iphoto, just can judge both-end point light sensing transistor Q
1Whether shone by incident light.
Fig. 2 A is the synoptic diagram that both-end point light sensing transistor operates in one second operator scheme (second operation mode).Be similar to Figure 1A, both-end point light sensing transistor Q
1Control end also be connected to the second end points N
2Compared to the first operator scheme, both-end point light sensing transistor Q
1The first end points N
1Be applied in low-voltage V
L, and the second end points is applied in high voltage V
HBecause both-end point light sensing transistor Q
1Control end and the second end points be coupled to high voltage V
H(being commonly referred to " diode connection "), so in the second operator scheme, both-end point light sensing transistor Q
1As a diode, and produce diode current I
Diode(namely forward On current) is by the second end points N
2Flow to the first end points N
1
Fig. 2 B shows both-end point light sensing transistor Q
1When operating in the second operator scheme, double-pointed voltage V
N2Relation with diode current.Be similar to known diode, both-end point light sensing transistor Q
1Diode current I
DiodeOriginally be zero, then after conducting, present the increase of index pattern.At both-end point light sensing transistor Q
1(V after the conducting
N2>10V), no matter whether incident light hv irradiation is arranged, all exist diode current by the second end points N
2Flow to the first end points N
1Be noted that the diode current I of incident light hv irradiation (square dotted line)
DiodeGreater than the diode current I ' that does not have incident light hv irradiation (rhombus dotted line)
DiodeIn one embodiment, if both-end point light sensing transistor Q
1Shone and double-pointed voltage V by incident light
N2Be 15V, then diode current I
DiodeBe about the 1.0E-09 ampere.On the contrary, if both-end point light sensing transistor Q
1Do not shone and double-pointed voltage V by incident light
N2Be 15V, then diode current I '
DiodeBe about the 0.5E-09 ampere.Therefore, the second operator scheme has two kinds of purposes, and the first is by the numerical value/size of detecting/judgement diode current, just can judge both-end point light sensing transistor Q
1Whether shone by incident light.The second is to utilize diode current allow the second end points N
2To the first end points N
1Discharge.In general, because diode current I
DiodeNumerical value much larger than the light sensing electric current I
PhotoNumerical value (large approximately 1.0E+03~1.0E+04 the order of magnitude), so with respect in the first operator scheme, the light sensing electric current I
PhotoTo the first end points N
1Charging process, in the second operator scheme, diode current I
DiodeTo the second end points N
2Discharge process be faster.
Fig. 3 is the synoptic diagram of active light sensing pixel.In the present embodiment, active light sensing pixel P
22Comprise both-end point light sensing transistor Q
1, driving transistors Q
2And replacement capacitor C
ResetActive light sensing pixel P
22Be coupled to and select signal wire Sel_2, and perpendicular between the output signal line Out_2 that selects signal wire Sel_2.
In Fig. 3, both-end point light sensing transistor Q
1Has the first end points N
1Be coupled to first node X
1, the second end points N
2Be coupled to and select signal wire Sel_2, and the control end points is connected in the second end points N
2Driving transistors Q
2Have the first end points and be coupled to the first reference voltage V
Ref1, the second end points is coupled to output signal line Out_2, and the control end points is connected in first node X
1The replacement capacitor C
ResetHave the first end points and be connected in both-end point light sensing transistor Q
1The control end points, and the second end points is connected in first node X
1
The light sensing method of light sensing pixel will be such as the explanation of following examples.Fig. 4 shows the sequential chart of selecting signal wire, and first node X
1Voltage waveform, first node X wherein
1Voltage waveform comprise light sensing pixel P
22By incident light hv irradiation and by two kinds of situations of incident light hv irradiation.In Fig. 4, solid line represents respectively to select the sequential chart of signal wire Sel_2 and Sel_3, and dotted line represents as light sensing pixel P
22When being shone by incident light hv, first node X
1Voltage V
X1Waveform, dotted line represents as light sensing pixel P
22When not shone by incident light hv, first node X
1Voltage V '
X1Waveform.
The transistorized operator scheme of both-end point light sensing below is discussed.At period 1 T
1(being commonly referred to exposure and readout interval), the voltage quasi position of selection signal wire Sel_2 is pulled to and is higher than first node X
1Voltage quasi position (such as high levle driving voltage V
GH), both-end point light sensing transistor Q
1Produce diode current to first node X as diode and according to incident light hv
1Charging.For example, if this moment light sensing pixel P
22Shone both-end point light sensing transistor Q by incident light
1Can produce diode current I according to incident light hv
Diode, with first node X
1Charge to the voltage V of high levle
X1As voltage V
X1Be higher than driving transistors Q
2Critical voltage the time, driving transistors Q
2Be switched on and produce and output current to output signal line Out_2, so period 1 T
1It also is readout interval.On the other hand, at period 1 T
1If the voltage quasi position of selection signal wire Sel_2 is pulled to and is higher than first node X
1Voltage quasi position (such as high levle driving voltage V
GH), and light sensing pixel P
22When not shone by incident light, both-end point light sensing transistor Q
1Then produce diode current I '
DiodeWith first node X
1Charge to the voltage V ' of high levle
X1That used here as can be known by above discussion is both-end point light sensing transistor Q
1The second operator scheme.Be noted that as both-end point light sensing transistor Q
1During as diode, the diode current I of incident light hv irradiation is arranged
DiodeGreater than the diode current I ' that does not have incident light hv irradiation
DiodeTherefore, with driving transistors Q
2Critical voltage design between the diode current I that is shone by incident light hv
DiodeCorresponding voltage V
X1With the diode current I ' that is not shone by incident light hv
DiodeCorresponding voltage V '
X1Between, so that driving transistors Q
2Can be by diode current I
Diode(being shone by incident light) conducting, and not by diode current I '
Diode(not shone by incident light) conducting just can be judged active light sensing pixel P
22Whether shone by incident light hv.In other words, first node X
1On voltage be V
X1The time, driving transistors Q
2Meeting conducting, and first node X
1On voltage be V '
X1The time, driving transistors Q
2Then can conducting.
At T second round
2(usually weighing accommodation cycle) selected the voltage quasi position of signal wire Sel_2 to become and is lower than first node X
1Voltage quasi position (such as low level driving voltage V
GL), the replacement capacitor C
ResetBy capacity coupled effect with first node X
1Voltage V
X1Reset, so that driving transistors Q
2Be cut off.
At T second round
2, because driving transistors Q
2End, so even incident light hv irradiation this moment light sensing transistor Q
1, light sensing transistor Q
1Can not produce diode current yet.Be noted that first node X
1Voltage V
X1Replacement mainly be by the replacement capacitor C
ResetAnd finish.In the present embodiment, select the high levle driving voltage V of signal wire
GHBe 10V, select the low level driving voltage V of signal wire
GLBe 0V, the voltage V of the high levle on the first node and low level
X1And V '
X1Between V
GHAnd V
GLBetween, V wherein
X1Greater than V '
X1First node X
1Voltage waveform V
X1Than low level driving voltage V
GLAt least high V
Th_Q1, V wherein
Th_Q1Be both-end point light sensing transistor Q
1Critical voltage.
Fig. 5 is the synoptic diagram of active light sensing pixel.Present embodiment is similar to the embodiment of Fig. 3 substantially, and for the purpose of simplifying the description, the sequential chart of its circuit connecting mode and selection signal wire repeats no more.Be noted that active light sensing pixel P
22Also comprise the sensitivity adjustment capacitor C
Sensitivity, have the first end points and be connected in first node X
1, and the second end points is connected in the second reference voltage V
Ref2
The sensitivity adjustment capacitor C then is described
SensitivityEffect.As mentioned above, by adjusting driving transistors Q
2Grid voltage (be first node X
1Voltage V
X1), just can judge active light sensing pixel P
22Whether shone by incident light.In the present embodiment, first node X
1Change in voltage Δ V
X1With the change in voltage Δ V that selects signal wire Sel_2
Sel_2Have following relation:
As diode current I
Diode(Δ V when very large
X1Very large), use to have the sensitivity adjustment capacitor C of larger capacitance
SensitivityAs diode current I
Diode(Δ V when very little
X1Very little), use the sensitivity adjustment capacitor C with smaller capacitive value
SensitivityParticularly, suppose Δ V
Sel_2Be definite value, if demand motive transistor Q
2Higher sensitivity (be Δ V
X1Less), then can select the less sensitivity adjustment capacitor C of capacitance
SensitivityTherefore, make diode current I even incident light is very faint
DiodeIt is very little to become, by using the less sensitivity adjustment capacitor C of capacitance
Sensitivity, still can the faint incident light hv of sensing.Whereby, to have higher signal to noise ratio (S/N ratio).
Fig. 6 is diagram and the corresponding sequential chart of signal wire of active light sensing array.Active light sensing array M
Photo-sensingComprise a plurality of signals selection signal wire Sel_1-Sel_4, a plurality of output signal line Out_0-Out_3, a plurality of active light sensing pixel P
11-P
43, driving circuit 50, and sensing circuit 51.In the present embodiment, a plurality of active light sensing pixel P
11-P
43Each be similar to substantially the embodiment of Fig. 5.For the purpose of simplifying the description, the sequential chart of its circuit connecting mode and selection signal wire Sel_1-Sel_4 repeats no more.Sequentially activation of driving circuit 50 selects signal to a plurality of selection signal wire Sel_1-Sel_4.For example, at period 1 T
1(exposure and readout interval), the voltage quasi position of selection signal wire Sel_2 is pulled to and is higher than first node X
1Voltage quasi position (such as high levle driving voltage V
GH), both-end point light sensing transistor Q
1As diode, and according to having or not incident light hv to produce diode current I
Diode/ I '
Diode, with first node X
1Charge to the voltage V of high levle
X1/ V '
X1As first node X
1On voltage be higher than driving transistors Q
2Critical voltage, driving transistors Q
2Be switched on and produce and output current to output signal line Out_2, then sensing circuit 51 is by detecting/judge that the numerical value/stool and urine of output current can determine active light sensing pixel P
22Whether shone by incident light hv.Therefore, period 1 T
1It also is readout interval.Because driving transistors Q
2Critical voltage be the design between the diode current I that is shone by incident light hv
DiodeCorresponding voltage V
X1With the diode current I ' that is not shone by incident light
DiodeCorresponding voltage V '
X1Between, so first node X
1On voltage be V
X1The time, driving transistors Q
2Meeting conducting, and first node X
1On voltage be V '
X1The time, driving transistors Q
2Then can conducting.
Then, at T second round
2, be lower than first node X when the voltage quasi position of selecting signal wire Sel_2 becomes
1Voltage quasi position (such as low level driving voltage V
GL), driving transistors Q
2By the replacement capacitor C
ResetVoltage V with first node
X1Reset, so that driving transistors Q
2Be cut off.Be noted that when selecting signal wire Sel_2 be period 1 T
1The time, selecting signal wire Sel_1, Sel_3 and Sel_4 is T second round
2, in other words, select the corresponding scan columns of signal wire Sel_1, Sel_3 and Sel_4 to end, so select the adjacent selection signal wire Sel_1 of signal wire Sel_2 and Sel_3 can not cause interference to selecting signal wire Sel_2.In other embodiments, active light sensing array M
Photo-sensingComprise selection signal wire, the scan signal line more than three more than four, and the light sensing pixel more than 12.The demand that known skill person works as according to product designs active light sensing array M
Photo-sensing
Fig. 7 is diagram and the corresponding sequential chart of signal wire of active light sensing and array of display.Active light sensing and array of display M
Sensing-displayComprise a plurality of selection signal wire Sel_1-Sel_4, a plurality of output signal line Out_0-Out_3, a plurality of data signal line data_1-data_4, a plurality of active light sensing and display pixel U
11-U
43, driving circuit 50, sensing circuit 51, and data drive circuit 52.In Fig. 7, active light sensing and display pixel U
11-U
43Each include an active light sensing pixel (P for example
22) and a display pixel (S for example
22), wherein each active light sensing pixel can be set up with the active light sensing pixel of previous embodiment of the present invention, does not repeat them here.With reference to display pixel S
22, display pixel S
22Comprise a switching transistor Q
3An and liquid crystal capacitance C
LC, switching transistor Q wherein
3Have one first end points and be coupled to the second data line data_2, one second end points, and a control end points is coupled to second and selects signal wire Sel_2, and liquid crystal capacitance C
LCHave one first end points and be connected in switching transistor Q
3The second end points, and one second end points is coupled to the 3rd reference voltage V
Ref3
The operation of active light sensing and array of display below is discussed.For example, at period 1 T
1, the voltage quasi position of selection signal wire Sel_1 is pulled to and is higher than light sensing pixel P
22First node X
1Voltage quasi position (such as high levle driving voltage V
GH), both-end point light sensing transistor Q
1Produce diode current I as diode and according to incident light hv
Diode, and diode current I
DiodeWith first node X
1Charge to the voltage V of high levle
X1As first node X
1On voltage be higher than driving transistors Q
2Critical voltage, driving transistors Q
2Be switched on and produce and output current to output signal line Out_2, then sensing circuit 51 is by detecting/judge that the numerical value/stool and urine of output current can determine active light sensing pixel P
22Whether shone by incident light hv.Therefore, period 1 T
1It also is readout interval.Because driving transistors Q
2Critical voltage system design between the diode current I that is shone by incident light hv
DiodeCorresponding voltage V '
X1With the diode current I ' that is not shone by incident light
DiodeCorresponding voltage V '
X1Between, so first node X
1On voltage be V
X1The time, driving transistors Q
2Meeting conducting, and first node X
1On voltage be V '
X1The time, driving transistors Q
2Then can conducting.
Then, at T second round
2, select the voltage quasi position of signal wire Sel_1 to become and be lower than first node X
1Voltage quasi position (such as low level driving voltage V
GL), and by the replacement capacitor C
ResetCapacitance coupling effect with the voltage V of first node
X1Reset, so driving transistors Q
2Can be cut off.At this moment, because select also driven circuit 50 activations of signal wire Sel_2, so display pixel S
22Switching transistor Q
4Conducting.Therefore, display pixel S
22Show active light sensing and display pixel U according to the data-signal that is received by the second data signal line data_2
22Whether shone by incident light.
Above-described embodiment provides active light sensing pixel and its light sensing method.Compared to known passive type light sensing pixel, the light sensing pixel of above-described embodiment has higher signal to noise ratio (S/N ratio) and driving force, therefore can satisfy the demand of large area display.In addition, above-described embodiment driving transistors Q
1Control end be to be connected to its second end points, so display can not be activated transistor Q
1The impact of critical voltage change.The light sensing pixel of above-described embodiment and array can be arranged at the lower plate of display, and replace known Charged Coupled Device (charge coupled device, CCD) optical sensor and CMOS optical sensor.
Although the present invention discloses as above with preferred embodiment, is not to limit the present invention.In addition, known skill person should be able to know that the present patent application claim should be assert to include all embodiment of the present invention and modification thereof largo.