Visible light signal generating method, signal generating apparatus, and program

1. A method comprising:

generating a preamble in which a first luminance value and a second luminance value alternately appear along a time axis, the first luminance value and second luminance value being different luminance values from each other;

generating a first payload in which the first luminance value and the second luminance value alternately appear along the time axis by determining a first time length of the first luminance value and a second time length of the second luminance value using a first formula, the first time length being a time length in which the first luminance value continues in the first payload, the second time length being a time length in which the second luminance value continues in the first payload, the first formula determining the first time length and the second time length according to a transmission target signal;

generating a visible light signal by joining the preamble and the first payload; and

transmitting the visible light signal by a change in luminance of a light source.

2. The visible light signal generating method according to claim 1 , further comprising:

generating a second payload by determining the time length according to a second mode, the second payload having a complementary relationship with a luminance expressed by the first payload, the time length being the time length during which each of the first and second luminance values continues in the data in which the first and second luminance values alternately appear along the time axis, the second mode matching the transmission target signal; and

generating the visible light signal by joining the preamble and the first and second payloads in order of the first payload, the preamble, and the second payload.

3. The visible light signal generating method according to claim 2 , wherein

the preamble is a header of the first and second payloads,

luminance values appear in the header in order of the first luminance value of a first time length and the second luminance value of a second time length,

the first time length is 100 μ seconds, and

the second time length is 90 μ seconds.

4. The visible light signal generating method according to claim 2 , wherein

the preamble is a header of the first and second payloads,

luminance values appear in the header in order of the first luminance value of a first time length, the second luminance value of a second time length, the first luminance value of a third time length, and the second luminance value of a fourth time length,

the first time length is 100 μ seconds,

the second time length is 90 μ seconds,

the third time length is 90 μ seconds, and

the fourth time length is 100 μ seconds.

5. The visible light signal generating method according to claim 3 , wherein

the transmission target signal includes six bits of a first bit x 0 to a sixth bit x 5 ,

luminance values appear in the first and second payloads in order of the first luminance value of a third time length and the second luminance value of a fourth time length, and

when a parameter y k is expressed by y k =x 3k +x 3k+1 ×2+x 3k+2 ×4 (k is 0 or 1),

the first payload is generated by determining each of the third and fourth time lengths of the first payload according to a time length P k =120+30×(7−y k ) [μ second] that is the first mode, and

the second payload is generated by determining each of the third and fourth time lengths of the second payload according to a time length P k =120+30×y k [μ second] that is the second mode.

6. The visible light signal generating method according to claim 4 , wherein

the transmission target signal includes 12 bits of a first bit x 0 to a twelfth bit x 11 ,

luminance values appear in the first and second payloads in order of the first luminance value of a fifth time length, the second luminance value of a sixth time length, the first luminance value of a seventh time length, and the second luminance value of an eighth time length, and

when a parameter y k is expressed by y k =x 3k +x 3k+1 ×2+x 3k+2 ×4 (k is 0, 1, 2 or 3),

the first payload is generated by determining each of the fifth to eighth time lengths of the first payload according to a time length P k =120+30×(7−y k ) [μ second] that is the first mode, and

the second payload is generated by determining each of the fifth to eighth time lengths of the second payload according to a time length P k =120+30×y k [μ second] that is the second mode.

7. The visible light signal generating method according to claim 1 , wherein

the preamble is a header of the first payload,

luminance values appear in the header in order of the first luminance value of a first time length, the second luminance value of a second time length, the first luminance value of a third time length, and the second luminance value of a fourth time length,

the first time length is 50 μ seconds,

the second time length is 40 μ seconds,

the third time length is 40 μ seconds, and

the fourth time length is 50 μ seconds.

8. The visible light signal generating method according to claim 7 , wherein

the transmission target signal includes 3n bits of a first bit x 0 to a 3nth bit x 3n-1 (n is an integer of 2 or more),

a time length of the first payload includes first to nth time lengths during which each of the first luminance values or the second luminance values continues, and

when a parameter y k is expressed by y k =x 3k +x 3k+1 ×2+x 3k+2 ×4 (k is an integer from 0 to (n−1)),

the first payload is generated by determining each of the first to nth time lengths of the first payload according to a time length P k =100+20×y k [μ second] that is the first mode.

9. An apparatus comprising:

a processor; and

a memory storing thereon a computer program, which when executed by the processor, causes the processor to perform operations including:

generating a preamble in which a first luminance value and a second luminance value alternately appear along a time axis, the first luminance value and second luminance value being different luminance values from each other;

generating a first payload in which the first luminance value and the second luminance value alternately appear along the time axis by determining a first time length of the first luminance value and a second time length of the second luminance value using a first formula, the first time length being a time length in which the first luminance value continues in the first payload, the second time length being a time length in which the second luminance value continues in the first payload, the first formula determining the first time length and the second time length according to a transmission target signal;

generating a visible light signal by joining the preamble and the first payload; and

transmitting the visible light signal by a change in luminance of a light source.

10. A non-transitory recording medium storing thereon a computer program, which when executed by a processor, causes the processor to perform operations including:

generating a preamble in which a first luminance value and a second luminance value alternately appear along a time axis, the first luminance value and second luminance value being different luminance values from each other;

generating a first payload in which the first luminance value and the second luminance value alternately appear along the time axis by determining a first time length of the first luminance value and a second time length of the second luminance value using a first formula, the first time length being a time length in which the first luminance value continues in the first payload, the second time length being a time length in which the second luminance value continues in the first payload, the first formula determining the first time length and the second time length according to a transmission target signal;

generating a visible light signal by joining the preamble and the first payload; and

transmitting the visible light signal by a change in luminance of a light source.