Ranging apparatus and ranging method

1. A ranging apparatus comprising:

a light-emitting unit having a light emitter, and a light emission controller for intensity-modulating a light emitted from said light emitter and emitting the intensity-modulated light as said modulated lights;

a light-detecting unit for detecting reflected lights from an object that is irradiated with said modulated lights; and

a calculating unit for calculating a distance up to said object based on a phase difference between said modulated lights and said reflected lights,

wherein the light emission controller comprises a start phase controller for controlling phases of modulated lights which start being emitted at times different from each other,

wherein said light-detecting unit samples amounts of the reflected lights in exposure periods established at a constant cycle length from the time when the modulated lights start being emitted,

wherein said light-detecting unit comprises:

an exposure period changer for changing terminal ends of said exposure periods based on an external control signal; and

wherein said light-emitting unit comprises:

a start phase changer for changing said start phases of said modulated lights based on said exposure periods which have been changed by said exposure period changer.

2. A ranging apparatus according to claim 1 , further comprising:

a memory storing a table which registers therein information on the start phases of said modulated lights which correspond to the changed exposure periods,

wherein said start phase changer changes the start phases of said modulated lights based on the changed exposure periods and the information registered in said table stored in said memory.

3. A ranging apparatus according to claim 1 , further comprising:

a start phase calculator for calculating the start phases of said modulated lights based on the changed exposure periods,

wherein said start phase changer changes the start phases of said modulated lights based on the information on the start phases from said start phase calculator.

4. A ranging apparatus according to claim 1 , wherein said light-emitting unit emits a first modulated light at a phase over a predetermined period from a first emission start time and emits a second modulated light at a different phase over said predetermined period from a second emission start time;

said light-detecting unit detects a first reflected light from said object irradiated with said first modulated light over said predetermined period from said first emission start time and detects a second reflected light from said object irradiated with said second modulated light over said predetermined period from said second emission start time; and

said calculating unit calculates the distance up to said object based on at least the phase difference between said first modulated light and said first reflected light and the phase difference between said second modulated light and said second reflected light.

5. A ranging apparatus according to claim 4 , wherein said light-detecting unit samples an amount of the first reflected light in exposure periods established at a constant cycle length from said first emission start time and samples an amount of the second reflected light in exposure periods established at the constant cycle length from said second emission start time; and

said calculating unit calculates a value representing the sampled amount of the first reflected light which is integrated over said predetermined period, as said phase difference between said first modulated light and said first reflected light, and calculates a value representing the sampled amount of the second reflected light which is integrated over said predetermined period, as said phase difference between said second modulated light and said second reflected light.

6. A ranging apparatus comprising:

a light-emitting unit having a light emitter, and a light emission controller for intensity-modulating a light emitted from said light emitter and emitting the intensity-modulated light as said modulated lights;

a light-detecting unit for detecting reflected lights from an object that is irradiated with said modulated lights; and

a calculating unit for calculating a distance up to said object based on a phase difference between said modulated lights and said reflected lights,

wherein the light emission controller comprises a start phase controller for controlling phases of modulated lights which start being emitted at times different from each other,

wherein said light-detecting unit samples amounts of the reflected lights in exposure periods established at a constant cycle length from the time when the modulated lights start being emitted,

wherein said light-detecting unit comprises:

an exposure timing changer for changing said cycle length of said exposure periods based on an external control signal, and

wherein said light-emitting unit comprises:

a wavelength changer for changing respective wavelengths of said modulated lights based on the cycle length of said exposure periods which has been changed by said exposure timing changer; and

a start phase changer for changing said start phases of said modulated lights based on the changed cycle length of said exposure periods.

7. A ranging apparatus according to claim 6 , further comprising:

a memory storing a table which registers therein information on the wavelengths and start phases of said modulated lights corresponding to the changed cycle length of said exposure periods;

wherein said wavelength changer changes the wavelengths of said modulated lights based on the changed cycle length of said exposure periods and the information registered in said table stored in said memory; and

said start phase changer changes said start phases of said modulated lights based on the changed cycle length of said exposure periods and the information registered in said table.

8. A ranging apparatus according to claim 6 , further comprising:

a wavelength calculator for calculating the wavelengths of said modulated lights based on the changed cycle length of said exposure periods; and

a start phase calculator for calculating said start phases of said modulated lights based on the changed cycle length of said exposure periods.

9. A ranging apparatus according to claim 6 , wherein said light-emitting unit emits a first modulated light at a phase over a predetermined period from a first emission start time and emits a second modulated light at a different phase over said predetermined period from a second emission start time;

said light-detecting unit detects a first reflected light from said object irradiated with said first modulated light over said predetermined period from said first emission start time and detects a second reflected light from said object irradiated with said second modulated light over said predetermined period from said second emission start time; and

said calculating unit calculates the distance up to said object based on at least the phase difference between said first modulated light and said first reflected light and the phase difference between said second modulated light and said second reflected light.

10. A ranging apparatus according to claim 9 , wherein said light-detecting unit samples an amount of the first reflected light in exposure periods established at a constant cycle length from said first emission start time and samples an amount of the second reflected light in exposure periods established at the constant cycle length from said second emission start time; and

said calculating unit calculates a value representing the sampled amount of the first reflected light which is integrated over said predetermined period, as said phase difference between said first modulated light and said first reflected light, and calculates a value representing the sampled amount of the second reflected light which is integrated over said predetermined period, as said phase difference between said second modulated light and said second reflected light.

11. A ranging apparatus comprising:

a light-emitting unit having a light emitter, and a light emission controller for intensity-modulating a light emitted from said light emitter and emitting the intensity-modulated light as said modulated lights;

a light-detecting unit for detecting reflected lights from an object that is irradiated with said modulated lights; and

a calculating unit for calculating a distance up to said object based on a phase difference between said modulated lights and said reflected lights,

wherein the light emission controller comprises a start phase controller for controlling phases of modulated lights which start being emitted at times different from each other, further comprising:

a start phase corrector for correcting said start phases of said modulated lights based on a difference between the distance up to said object which is calculated by said calculating unit and a distance measured up to said object.

12. A ranging method comprising the steps of:

(a) emitting modulated lights by intensity-modulating lights emitted from a light-emitting unit and which have respective different start phases at which the modulated lights start being emitted;

(b) detecting reflected lights from an object that is irradiated with said modulated lights; and

(c) calculating a distance up to said object based on a phase difference between said modulated lights and said reflected lights,

wherein the emitting step (a) comprises a step of controlling phases of the modulated lights being emitted at times different from each other,

further comprising the step of:

correcting said start phases of said modulated lights based on a difference between the distance up to said object which is calculated in said step (c) and a distance measured up to said object.

13. A ranging method according to claim 12 , wherein said step (a) comprises:

emitting a first modulated light at a phase over a predetermined period from a first emission start time and emitting a second modulated light at a different phase over said predetermined period from a second emission start time;

wherein said step (b) comprises:

detecting a first reflected light from said object irradiated with said first modulated light over said predetermined period from said first emission start time, and detecting a second reflected light from said object irradiated with said second modulated light over said predetermined period from said second emission start time; and

wherein said step (c) comprises:

calculating the distance up to said object based on at least the phase difference between said first modulated light and said first reflected light, and the phase difference between said second modulated light and said second reflected light.

14. A ranging method according to claim 13 , wherein said step (b) comprises:

sampling an amount of said first reflected light in exposure periods established at a constant cycle length from said first emission start time and sampling an amount of said second reflected light in exposure periods established at the constant cycle length from said second emission start time; and

said step (c) comprises calculating a value representing the sampled amount of said first reflected light which is integrated over said predetermined period, as said phase difference between said first modulated light and said first reflected light and calculating a value representing the sampled amount of said second reflected light which is integrated over said predetermined period, as said phase difference between said second modulated light and said second reflected light.