Liquid crystal display device provided with an image capturing function

• US 7,463,297 B2
• Filed: 11/30/2004
• Issued: 12/09/2008
• Est. Priority Date: 12/12/2003
• Status: Expired due to Fees

• Current Assignee: Japan Display Central Incorporated (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Inventors: Nakamura, Takashi, Yoshida, Masahiro, Hayashi, Hirotaka, Tada, Norio, Hirota, Jun, Kinoshita, Masaki
• Primary Examiner(s): Ometz; David
• Assistant Examiner(s): Giles; Nicholas G
• Application Number:
  US10/998,836
• Publication Number:
  US 20050128331A1
• Time in Patent Office: 1,470 Days
• Field of Search: 348/310, 348/308, 348/302, 348/311, 348/294, 345/102, 345/98, 345/100, 345/103, 345/90, 345/92
• US Class Current: 348/294
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H01L 27/146 Imager structures

Abstract

To enable acquisition of image data in multiple tone levels in a short capturing time, a liquid crystal display device 1 includes a photodiode having sensitivity R, a capacitor having capacitance C and configured to store a charge in response to an electric signal converted by the photodiode in a state where an initial voltage V is applied thereto, a SRAM configured to retain binary data which indicate as to whether or not an amount of charge stored in the capacitor is equal to or above a threshold voltage Vth, an image capturing control unit 5 configured to generate pixel data in multiple tone levels based on the binary data outputted from the SRAM of a plurality of adjacent pixels. Here, at least any one value of R, V, C, and Vth in each of the pixels is set to a different value from relevant values of other adjacent pixels.

Claims

1. A liquid crystal display device comprising:

a plurality of pixels;

a plurality of optical sensors corresponding to each of the plurality of pixels, each optical sensor having a sensitivity R and each optical sensor being configured to convert an accepted light into an electric signal;

a plurality of charge storage units corresponding to each of the plurality of optical sensors, each charge storage unit having a capacitance C and each charge storage unit being configured to store a charge in response to the electric signal converted by the optical sensor while the optical sensor has an initial voltage V applied;

a plurality of retention units corresponding to each of the plurality of charge storage units, each retention unit being configured to retain a plurality of binary data, said binary data indicating whether an amount of charge stored in the charge storage unit is equal to or above a threshold voltage Vth;

an image capturing control unit configured to generate a plurality of pixel data in a plurality of tone levels, based on the binary data outputted from each of the retention units of the plurality of adjacent pixels by image capturing for N times, wherein at least one value of sensitivity R, capacitance C, initial voltage V, and threshold voltage Vth in each of the pixels is set to a different value from a relevant value of other adjacent pixels; and

wherein, in terms of p×

q adjacent pixels of the plurality of adjacent pixels, an exposure time T(n) for an n-th (n=1, 2, . . . , N) image capturing by a specified pixel is calculated based on an average dark current I₀, a reversal exposure time Tw in terms of a white standard subject for the specified pixel, a reversal exposure time Tb in terms of a black standard subject for the specified pixel, and with equations expressed as

$\frac{1}{T<br><br>\left(n\right)}=\frac{1}{\mathrm{Tw}}-n<br><br><br><br>\mathrm{\Delta <br><br>},\mathrm{\Delta <br><br>}=\left(\frac{1}{\mathrm{Tw}}-\frac{1}{\mathrm{Tb}}\right)/N,$

and

a parameter k, to determine an amount of variation of sensitivity for each of the plurality of pixels, is set in a range defined as 1≦

k≦

N−

p×

q+1 and, based on a standard value of sensitivity R₁ set in the specified pixel, a plurality of respective values of sensitivity R₂ to R<sub>p×

q</sub> set in other pixels are calculated by equations expressed as

$R_{m+1}=R_1+m<br><br><br><br>\mathrm{\delta <br><br>}<br><br><br><br>R,\frac{\mathrm{\delta <br><br>}<br><br><br><br>R}{R_1}=\mathrm{\Delta <br><br>}·<br><br>T<br><br>\left(k\right)·<br><br>\frac{1}{1-\frac{I_0<br><br>T<br><br>\left(k\right)}{C_1<br><br>\left(V_1-{\mathrm{Vth}}_1\right)}}$

(where m=1, 2, . . . , p×

q−

1).

2. The liquid crystal display device according to claim 1,

wherein, in terms of p×

q adjacent pixels of the plurality of adjacent pixels, exposure time T(n) for an n-th (n=1, 2, . . . , N) image capturing by a specified pixel is calculated based on an average dark current I₀, a reversal exposure time Tw in terms of a white standard subject for the specified pixel, a reversal exposure time Tb in terms of a black standard subject for the specified pixel, and with equations expressed as

$\frac{1}{T<br><br>\left(n\right)}=\frac{1}{\mathrm{Tw}}-n<br><br><br><br>\mathrm{\Delta <br><br>},\mathrm{\Delta <br><br>}=\left(\frac{1}{\mathrm{Tw}}-\frac{1}{\mathrm{Tb}}\right)/N,$

and

a parameter k, to determine an amount of variation of sensitivity for each of the plurality of pixels, is set in a range defined as 1≦

k≦

N−

p×

q+1, and, based on a standard value of capacitance C₁ set in the specified pixel, a plurality of respective values of capacitance C₂ to C<sub>p×

q</sub> set in other pixels are calculated by equations expressed as

$C_{m+1}=C_1-m<br><br><br><br>\mathrm{\delta <br><br>}<br><br><br><br>C,\frac{\mathrm{\delta <br><br>}<br><br><br><br>C}{C_1}=\mathrm{\Delta <br><br>}·<br><br>T<br><br>\left(k\right)$

(where m=1, 2, . . . , p×

q−

1).

3. The liquid crystal display device according to claim 1,

wherein, in terms of p×

q adjacent pixels of the plurality of adjacent pixels, exposure time T(n) for an n-th (n=1, 2, . . . , N) image capturing by a specified pixel is calculated based on an average dark current I₀, a reversal exposure time Tw in terms of a white standard subject for the specified pixel, a reversal exposure time Tb in terms of a black standard subject for the specified pixel, and with equations expressed as

$\frac{1}{T<br><br>\left(n\right)}=\frac{1}{\mathrm{Tw}}-n<br><br><br><br>\mathrm{\Delta <br><br>},\mathrm{\Delta <br><br>}=\left(\frac{1}{\mathrm{Tw}}-\frac{1}{\mathrm{Tb}}\right)/N,$

and

a parameter k, to determine an amount of variation of sensitivity for each of the plurality of pixels, is set in a range defined as 1≦

k≦

N−

p×

q+1, and, based on a standard value of initial voltage V₁ set in the specified pixel, a plurality of respective values of initial voltage V₂ to V<sub>p×

q</sub> set in other pixels are calculated by equations expressed as

$V_{m+1}=V_1-m<br><br><br><br>\mathrm{\delta <br><br>}<br><br><br><br>V,\frac{\mathrm{\delta <br><br>}<br><br><br><br>V}{V_1-V<br><br><br><br>{\mathrm{th}}_1}=\mathrm{\Delta <br><br>}·<br><br>T<br><br>\left(k\right)$

(where m=1, 2, . . . , p×

q−

1).

4. The liquid crystal display device according to claim 1,

wherein, in terms of p×

q adjacent pixels of the plurality of adjacent pixels, exposure time T(n) for an n-th (n=1, 2, . . . , N) image capturing by a specified pixel is calculated based on an average dark current I₀, a reversal exposure time Tw in terms of a white standard subject for the specified pixel, a reversal exposure time Tb in terms of a black standard subject for the specified pixel, and with equations expressed as

$\frac{1}{T<br><br>\left(n\right)}=\frac{1}{\mathrm{Tw}}-n<br><br><br><br>\mathrm{\Delta <br><br>},\mathrm{\Delta <br><br>}=\left(\frac{1}{\mathrm{Tw}}-\frac{1}{\mathrm{Tb}}\right)/N,$

and

a parameter k, to determine an amount of variation of sensitivity for each of the plurality of pixels, is set in a range defined as 1≦

k≦

N−

p×

q+1, and, based on a standard value of threshold voltage Vth₁ set to the specified pixel, a plurality of respective values of threshold voltage Vth₂ to Vth<sub>p×

q</sub> set in other pixels are calculated by equations expressed as

${\mathrm{Vth}}_{m+1}={\mathrm{Vth}}_1+m<br><br><br><br>\mathrm{\delta <br><br>}<br><br><br><br>\mathrm{Vth},\frac{\mathrm{\delta <br><br>}<br><br><br><br>\mathrm{Vth}}{V_1-V<br><br><br><br>{\mathrm{th}}_1}=\mathrm{\Delta <br><br>}·<br><br>T<br><br>\left(k\right)$

(where m=1, 2, . . . , p×

q−

1).