Pen input apparatus and pen input method for detecting approach of pen to display integrated tablet by controlling lighting of back light

Claim 2

The pen input apparatus according to claim 1, wherein said generation means (5) provides at least two pulses of said inversion signal while said back light (2) is turned off by said control means (6), and said determination means (14) compares voltage values of at least two direct-current voltages converted by said first conversion means (11) according to said at least 2 pulses with said predetermined value for determining whether said detection pen (3) is close to said liquid crystal panel (1).

Claim 3

The pen input apparatus according to claim 1, further comprising second conversion means (12) to detect an induced voltage at said detection pen (3) for converting the induced voltage into a direct-current voltage during a period when said first conversion means (11) is not detecting a voltage induced by said detection pen (3), wherein said determination means (14) compares a voltage value of the direct-current voltage converted by said first conversion means (11) with a voltage value of the direct-current voltage converted by said second conversion means (12) to determine whether said detection pen (3) is close to said liquid crystal panel (1).

Claim 4

A pen input apparatus comprising: an inversion signal generation circuit (5) for generating an inversion signal to invert an apply direction of a voltage applied to liquid crystal of a liquid crystal panel (1), a gate signal generation circuit (7) for generating a first gate signal in synchronization with the inversion signal generated by said inversion signal generation circuit (5), a first conversion circuit (11) to detect a voltage induced at a detection pen (3) by the first gate signal generated by said gate signal generation circuit (7) for converting the induced voltage into a direct-current voltage, a comparator circuit (14) for comparing a voltage value of the direct-current voltage converted by said first conversion circuit (11) with a predetermined value to generate a detection mode signal of coordinates, and a detection period signal generation circuit (6) for generating a coordinate detection period signal to turn on a back light (2) of said liquid crystal panel (1) when said first conversion circuit (11) is not detecting an induced voltage by the first gate signal, and to turn off said back light (2) when said first conversion circuit (11) is detecting an induced voltage by the first gate signal.

Claim 5

The pen input apparatus according to claim 4, wherein said inversion signal generation circuit (5) provides at least two pulses of said inversion signal while said back light (2) is turned off by said detection period signal generation circuit (6), and said comparator circuit (14) compares voltage values of at least two direct-current voltages output from said first conversion circuit (11) by said at least two pulses with said predetermined value to generate a detection mode signal of coordinates.

Claim 6

The pen input apparatus according to claim 4, further comprising a second conversion circuit (12) to detect a voltage induced at a detection pen (3) by a second gate signal for converting the induced voltage into a direct-current voltage, wherein said gate signal generation circuit (7) generates a first gate signal in synchronization with the inversion signal generated by said inversion signal generation circuit (5), and said second gate signal which is an inverted version of said first gate signal, wherein said comparator circuit (14) compares a voltage value of the direct-current voltage converted by said first conversion circuit (11) with a voltage value of the direct-current voltage converted by said second conversion circuit (12) to generate a detection mode signal of coordinates.

Claim 7

A pen input method comprising the steps of: generating an inversion signal to invert an apply direction of a voltage applied to liquid crystal of a liquid crystal panel (1), detecting a first induced voltage induced at a detection pen (3) according to said inversion signal, determining whether said detection pen (3) is close to said liquid crystal panel (1) by comparing a voltage value of said detected first induced voltage with a predetermined value, and turning on a back light (2) of said liquid crystal panel (1) when said first induced voltage is not being detected, and turning off said back light (2) when said first induced voltage is being detected.

Claim 8

The pen input method according to claim 7, further comprising the step of detecting a second voltage induced at said detection pen (3) while said first induced voltage is not being detected, wherein said step of determination compares a voltage value of said detected first induced voltage with a voltage value of said second induced voltage for determining whether said detection pen (3) is close to said liquid crystal panel (1).