Transmitter and transmitting method

• US 9,377,639 B2
• Filed: 06/30/2014
• Issued: 06/28/2016
• Est. Priority Date: 02/19/2014
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Inventors: Aoyama, Hideki, Oshima, Mitsuaki
• Primary Examiner(s): Vu, Phu
• Application Number:
  US14/318,745
• Publication Number:
  US 20150234218A1
• Time in Patent Office: 729 Days
• US Class Current: 1/1
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/133342 for double-sided displays
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133524 Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/133626 providing two modes of illumination, e.g. day-night
• CPC Class Codes: G02F 1/135 Liquid crystal cells structurally associated with a photoconducting or a ferro-electric layer, the properties of which can be optically or electrically varied G02F1/133348 takes precedence
• CPC Class Codes: H04B 10/116 Visible light communication

Abstract

A transmitter that is difficult to be affected by structural constraints includes: a liquid crystal board; a first board having translucency; and a second board; and a control unit that changes, by switching transmittance of the liquid crystal board with respect to outside light through application, to the liquid crystal board, of a control voltage corresponding to a signal to be transmitted, an amount of light reflected by the first board and emitted toward the receiver via the liquid crystal board, wherein the control unit maintains, when switching the transmittance of the liquid crystal board to a low transmittance, the transmittance of the liquid crystal board at the low transmittance until the outside light that passed through the liquid crystal board is reflected by the second board and reaches the liquid crystal board.

Claims

1. A transmitter that transmits a signal to a receiver by changing an amount of light emitted, the transmitter comprising:

a liquid crystal board;

a first board having translucency;

a second board disposed to sandwich the first board with the liquid crystal board; and

a control unit configured to, by switching transmittance of the liquid crystal board with respect to outside light between a first transmittance and a second transmittance through application, to the liquid crystal board, of a control voltage corresponding to a signal to be transmitted, change an amount of outside light reflected by the first board and emitted toward the receiver via the liquid crystal board,

wherein the control unit is configured to, when switching the transmittance of the liquid crystal board to the second transmittance, maintain the transmittance of the liquid crystal board at the second transmittance until outside light that passed through the liquid crystal board is reflected by the second board and reaches the liquid crystal board via the first board, the second transmittance being lower than the first transmittance.

2. The transmitter according to claim 1,

wherein the liquid crystal board includes:

a first polarizing board provided on a surface side of a liquid crystal display;

a liquid crystal; and

a second polarizing board disposed to sandwich the liquid crystal board with the first polarizing board, and

the second polarizing board is installed on the liquid crystal display so that a polarizing direction of the second polarizing board is perpendicular to a polarizing direction of the first polarizing board.

3. The transmitter according to claim 1,

wherein a signal transmitting unit including the liquid crystal board, the first board, and the second board is formed only at an end of a surface of a liquid crystal display.

4. The transmitter according to claim 1,

wherein a signal transmitting unit including the liquid crystal board, the first board, and the second board is formed only on a rim of a surface of a liquid crystal display.

5. The transmitter according to claim 1,

wherein a signal transmitting unit including the liquid crystal board, the first board, and the second board is formed only in a portion along a boundary between a plurality of liquid crystal displays that are disposed adjacent to each other, in each surface of the plurality of liquid crystal displays.

6. The transmitter according to claim 1,

wherein the control unit is configured to, by changing a control voltage to be applied to the liquid crystal board in a range higher than a predetermined voltage value, switch the transmittance of the liquid crystal board between the first transmittance and the second transmittance.

7. The Transmitter according to claim 6,

wherein the predetermined voltage value is 0 V.

8. The transmitter according to claim 1,

wherein the control unit is configured to, when transmitting a k-th signal in a case where different frequencies are assigned to respective 0th to n-th signals, apply a control voltage that changes at a frequency assigned to the k-th signal to the liquid crystal board, k being an integer from 0 to n, n being an integer of at least 0, and

when, in the assignment of the different frequencies, a value of an i-th signal is represented by (a+b×

i) using constants a and b, the different frequencies are assigned so that a difference between a frequency f (i) assigned to the i-th signal and a frequency f (i−

1) assigned to an (i−

1)th signal is larger or smaller as i is larger, i being an integer from 0 to 1.

9. The transmitter according to claim 1,

wherein in at least one of two polarizing boards included in the liquid crystal board, an area in which polarization is not performed on outside light is uniformly formed with respect to the at least one of two polarizing boards.

10. A transmitting method of transmitting, by a transmitter, a signal to a receiver by changing an amount of light emitted, the transmitter including:

a liquid crystal board;

a first board having translucency; and

a second board disposed to sandwich the first board with the liquid crystal board,

the transmitting method comprising;

changing, by switching transmittance of the liquid crystal board with respect to outside light between a first transmittance and a second transmittance through application, to the liquid crystal board, of a control voltage corresponding to a signal to be transmitted, an amount of outside light reflected by the first board and emitted toward the receiver via the liquid crystal board; and

maintaining, when the transmittance of the liquid crystal board is switched to the second transmittance, the transmittance of the liquid crystal board at the second transmittance until outside light that passed through the liquid crystal board is reflected by the second board and reaches the liquid crystal board via the first board, the second transmittance being lower than the first transmittance.

11. A non-transitory computer-readable recording medium for use in a computer, the recording medium having recorded thereon a program for controlling a transmitter that transmits a signal to a receiver by changing an amount of light emitted, the transmitter including:

a liquid crystal board;

a first board having translucency; and

a second board disposed to sandwich the first board with the liquid crystal board, the program causing the computer to execute;

changing, by switching transmittance of the liquid crystal board with respect to outside light between a first transmittance and a second transmittance through application, to the liquid crystal board, of a control voltage corresponding to a signal to be transmitted, an amount of outside light reflected by the first board and emitted toward the receiver via the liquid crystal board; and

maintaining, when the transmittance of the liquid crystal board is switched to the second transmittance, the transmittance of the liquid crystal board at the second transmittance until outside light that passed through the liquid crystal board is reflected by the second board and reaches the liquid crystal board via the first board, the second transmittance being lower than the first transmittance.