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In an apparatus using an intensity-modulated light for detection of spatial information based upon light intensity of light reflected from a target space, a timing synchronization circuit is provided to synchronize a phase of the intensity-modulated light from a light-emitting element with a timing

In an apparatus using an intensity-modulated light for detection of spatial information based upon light intensity of light reflected from a target space, a timing synchronization circuit is provided to synchronize a phase of the intensity-modulated light from a light-emitting element with a timing of operating a light-receiving element receiving the intensity-modulated light. The light-receiving element is caused to operate for enabling the detection of intensity of the received light for each of a plurality of phase regions within one cycle of the intensity-modulated light. The timing synchronization circuit functions to compare a cyclic variation determining the operation of the light-receiving element with a cyclic variation associated with an output from a light-emitting element driving circuit in order to keep a constant phase difference between these two cyclic variations.

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The invention claimed is: 1. A spatial information detection apparatus comprising: a light-emitting element (100) configured to emit an intensity-modulated light to a target space; a lighting signal generation circuit (10) configured to generate a lighting timing signal (E1) which determines a ligh

The invention claimed is: 1. A spatial information detection apparatus comprising: a light-emitting element (100) configured to emit an intensity-modulated light to a target space; a lighting signal generation circuit (10) configured to generate a lighting timing signal (E1) which determines a lighting timing of said light-emitting element, a light-emitting element driving circuit (30) configured to output a light-emitting element driving signal (E2) in response to said lighting timing signal for generation of said intensity-modulated light from said light-emitting element; a light-receiving element (200) configured to receive said intensity-modulated light reflected from an object in said target space; an information output circuit (300) configured to extract a light intensity of the light received at the said light-receiving element for each of a plurality of phase ranges (P0, P1, P2, and P3), determine a relation between said intensity-modulated light from said light-emitting element and said intensity-modulated light received at said light-receiving element based upon a variation of said extracted light intensities, and output spatial information within said target space; a light-receiving element driving circuit (40; 40A; 40B) configured to output a plurality of light-receiving element driving signals D2 which are out of phase relation from each other to said light-receiving element in order to activate said light-receiving element for each of said phase ranges; a detection signal generation circuit (20) configured to provide to said light-receiving element driving circuit a detection timing signal (D1) for determination of a timing of generating said light-receiving element driving signal; and a timing synchronization circuit (70; 70A; 70B) configured to compare a cyclic variation associated with the output from said light-emitting element driving circuit with a cyclic variation determined by said detection timing signal, and modify at least one of said detection timing signal (D1) and said lighting timing signal (E1) in order to keep a constant phase difference between said cyclic variations. 2. A spatial information detection apparatus as set forth in claim 1, wherein said timing synchronization circuit (70) is configured to obtain a cyclic variation of said light-receiving element driving signal (D2) from said light-receiving element driving circuit as said cyclic variation to be determined by said detection timing signal for comparison with the light-emitting element driving signal (E2) from said light-emitting element driving circuit (30). 3. A spatial information detection apparatus as set forth in claim 1 or 2, wherein said timing synchronization circuit (70) is configured to modify said lighting timing signal into a modified lighting timing signal (E1x) and feed said modified lighting timing signal to said light-emitting element driving circuit. 4. A spatial information detection apparatus as set forth in claim 3, wherein said timing synchronization circuit (70) is interposed between said lighting signal generation circuit (10) and said light-emitting element driving circuit (30), and comprises: a phase adjusting circuit (76) configured to shift a phase of the lighting timing signal output from said lighting signal generation circuit to said light-emitting element driving circuit (30) by variable a phase shift value, and a phase comparator (72) configured to determine said phase shift value in accordance with a phase difference between the cyclic variation output from said light-receiving element driving element circuit and the light-emitting element driving signal from said light-emitting element driving circuit (30). 5. A spatial information detection apparatus as set forth in claim 3, wherein said light-receiving element driving circuit (40) is configured to determine said light-receiving element driving signal based upon a plurality of detection timing signals output from said detection signal generation circuit, and a selector (80 is provided to selectively extract the light-receiving element driving signals which are out of phase relation from each other, said timing synchronization circuit (70) being configured to modify said lighting timing signals based upon a phase difference between said light-receiving element driving signals (D2) selected from said selector 80 and the cyclic variation (E2) associated with the output from said light-emitting element driving circuit (30). 6. A spatial information detection apparatus as set forth in claim 5, wherein said information output circuit (300) is configured to integrate the received light intensities over a plurality of times for each of said phase regions (P0, P1, P2, P3) corresponding to said light-receiving element driving signals, said information output circuit being configured to obtain the received light intensity from said light-receiving element (200) at each of said phase regions (P0, P1, P2, P3) in synchronous with the light-receiving element driving signal D2 selected from said selector (80). 7. A spatial information detection apparatus as set forth in claim 2, further including: a supplemental phase adjusting circuit (90 interposed between said detection signal generation circuit (20) and said light-receiving element driving circuit (40) and configured to shift the phase of said detection timing signal by a variable shift phase value and output said detection timing signal to said light-receiving element driving circuit; a supplemental phase comparator (92) configured to detect a phase difference between said detection timing signal (D1) and the cyclic variation (D2) output from said light-receiving element driving circuit for providing an output indicative of said phase difference to said supplemental phase adjusting circuit; said supplemental phase adjusting circuit (90) being configured to determine said phase shift value based upon said phase difference for keeping a predetermined value given for the phase difference between said detection timing signal (D1) and said light-receiving element driving signal (D2) from the light-receiving element driving circuit. 8. A spatial information detection apparatus as set forth in claim 1, wherein said timing synchronization circuit (70; 70A) is configured to compare the cyclic variation (E2) resulting from the output from said light-emitting element driving circuit (30) with said detection timing signal (D1) from the detection signal generation circuit (20). 9. A spatial information detection apparatus as set forth in claim 8, wherein said timing synchronization circuit (70) is configured to modify said lighting timing signal to provide the modified lighting timing signal (E1x) to said light-emitting element driving circuit. 10. A spatial information detection apparatus as set forth in claim 8, wherein said timing synchronization circuit (70A) is configured to modify said detection timing signal (D1) into a modified detection timing signal (D1x) and provide the modified detection timing signal to said light-receiving element driving circuit (40). 11. A spatial information detection apparatus as set forth in claim 10, wherein said timing synchronization circuit (70A) is interposed between said detection signal generation circuit (20) and said light-receiving element driving circuit (40), and comprises: a phase adjusting circuit (76A) configured to shift a phase of said detection timing signal (D1) from said detection signal generation circuit by a variable phase shift value and output said detection timing signal to said light-receiving element driving circuit (40); and a phase comparator (72A) configured to determine said phase shift value based upon the phase difference between the cyclic variation output from said light-emitting element driving circuit and said detection timing signal from said detection signal generation circuit. 12. A spatial information detection apparatus as set forth in claim 10, further including: a supplemental phase adjusting circuit (90A) interposed between said timing synchronization circuit (70A) and said light-receiving element driving circuit (40) and configured to shift a phase of said modified detection timing signal (D1x) by a variable phase shift value; a supplemental phase comparator (92A configured to detect a phase difference between said modified detection timing signal (D1x) and the light-receiving element driving signal (D2) from said light-receiving element driving circuit (40) to provide an output indicative of said phase difference to said supplemental phase adjusting circuit (90A), and said supplemental phase adjusting circuit (90A) configured to determine said phase shift value based upon said phase difference for keeping a predetermined value given for the phase difference between said modified detection timing signal (D1x) from said timing synchronization circuit (70A) and said light-receiving element driving signal (D2) from the light-receiving element driving circuit (40). 13. A spatial information detection apparatus as set forth in claim 10, further including: a reference light-receiving element (110) configured to receive a portion of said intensity modulated light from said light-emitting element to output an corresponding light intensity; and said timing synchronization circuit (70A) being configured to use the light intensity as indicative of the cyclic variation associated from the output from said light-emitting element driving circuit (30). 14. A spatial information detection apparatus as set forth in claim 10, wherein said timing synchronization circuit (70B) comprises: an oscillation circuit (78) configured to use a signal of which frequency varies with a varying input voltage and provide the signal as said modified detection timing signal to said light-receiving element driving circuit (40), and a phase comparator (72B) configured to generate a voltage indicative of a phase difference between the cyclic variation (E2) associated with the output from said light-emitting element driving circuit (30) and the detection timing signal (D1x) from said detection signal generation circuit (20), and provide said voltage to said oscillation circuit. 15. A spatial information detection apparatus as set forth in claim 1, wherein said timing synchronization circuit comprises: a first timing synchronization circuit (70) interposed between said lighting signal generation circuit (10) and said light-emitting element driving circuit; and a second timing synchronization circuit (70A) interposed between detection signal generation circuit and said light-receiving element driving circuit; said first timing synchronization circuit (70) comprising a first phase adjusting circuit (76) configured to shift a phase of said lighting timing signal (E1) from said lighting signal generation circuit (10) by a variable phase shift value, and output said lighting timing signal to said light-emitting element driving circuit (30), a first phase comparator (72) configured to determine said phase shift value based upon a phase difference between the cyclic variation (E2) output from said light-emitting element driving circuit (30) and said detection timing signal (D1) from said detection signal generation circuit (20); said second timing synchronization circuit (70A) comprising a second phase adjusting circuit (76A) configured to shift a phase of said detection timing signal (D1) from said detection signal generation circuit (20) by a variable phase shift amount, and output said detecting timing signal to said light-receiving element driving circuit (40), and a second phase comparator (72A) configured to determine said phase shift value based upon a phase difference between said lighting timing signal (E1) from said lighting signal generation circuit (10) and said light-receiving element driving signal (D2) from said light-receiving element driving circuit (40). 16. A spatial information detection apparatus as set forth in claim 1, wherein said light-receiving element has a capacitive reactance and is configured to operate on a DC current supplied from a DC power source (210), said light-receiving element driving circuit (40B) comprising: an output switch (50) connected between said DC power source and said light-receiving element to supply said DC current to said light-receiving element in synchronization with said detection timing signal; a temperature sensor (150) for detection of an ambient temperature; and a current controller (160) configured to regulate the current being fed to said light-receiving element in such a manner as to keep the current being fed to said light-receiving element at a predetermined varying rate. 17. A spatial information detection apparatus as set forth in claim 16, wherein said current controller (160) includes a memory means (162) configured to store the varying rate of the current through said light-receiving element in association with the temperature, said current controller being configured to read out from said memory means (162) the current varying rate corresponding to the temperature output from said temperature sensor (150) and control the current flowing through the light-receiving element in match with the reading of the current varying rate. 18. A spatial information detection apparatus as set forth in claim 1, wherein said light-receiving element has a capacitive reactance and is configured to operate on a DC current supplied from a DC power source (210), said light-receiving element driving circuit 40A comprising: an output switch (50) connected between said DC power source and said light-receiving element to supply said DC current to said light-receiving element in synchronization with said detection timing signal; a current monitoring circuit (60) configured to monitor a varying rate of the current being fed to said light-receiving element and provides a current variation output indicative of the varying rate; and a current controller (66) configured to operate in response to said current variation output for regulating the current being fed to said light-receiving element in such a manner as to keep the current being fed to said light-receiving element at a predetermined varying rate. 19. A spatial information detection apparatus as set forth in claim 18, wherein said current monitoring circuit (60) comprises: a differential circuit (62) configured to calculate an instant varying rate of the current flowing through the light-receiving element; and a peak detection circuit (64) configured to detect a maximum of said instant varying rate from said differential circuit; said current controller (66) being configured to control the current flowing through said light-receiving element based upon said maximum of the instant varying rate from said peak detection circuit in order to keep the varying rate at a predetermined value. 20. A spatial information detection apparatus as set forth in claim 19, wherein said light-receiving element driving circuit further comprising: a temperature sensor (130) for detection of an ambient temperature; a register (68) configured to hold a maximum of said instant varying rate detected at said peak detection circuit (64); a temperature table (140) configured to store the output of said temperature sensor at a predetermined interval; and an activation circuit (120) configured to activate said differential circuit and said peak detection circuit only when there is detected a temperature difference exceeding a predetermined level between a current temperature and a past temperature recorded at a predetermined past time. 21. A spatial information detection apparatus comprising: a light-emitting element (100) configured to emit an intensity-modulated light to a target space; a lighting signal generation circuit (10) configured to generate a lighting timing signal (E1) which determines a lighting timing of said light-emitting element, a light-emitting element driving circuit (30) configured to output a lighting-element driving signal (E2) in response to said lighting timing signal for generation of said intensity-modulated light at said light-emitting element; a light-receiving element (200) configured to receive said intensity-modulated light reflected from an object in said target space; an information output circuit (300 configured to obtain a light intensity of the light received at the said light-receiving element for each of a plurality of phase ranges (P0, P1, P2, P3), determine a relation between said intensity-modulated light from said light-emitting element and said intensity-modulated light received at said light-receiving element based upon a variation of said light intensities, and output spatial information within said target space; a light-receiving element driving circuit (40; 40A; 40B) configured to output a plurality of light-receiving element driving signals (D2) which are out of phase relation from each other to said light-receiving element in order to activate said light-receiving element for each of said phase ranges; a detection signal generation circuit (20) configured to provide to said light-receiving element driving circuit a detection timing signal (D1) for determination of a timing of generating said light-receiving element driving signal; and a timing synchronization circuit (70; 70A; 70B) configured to compare a cyclic variation of the lighting timing signal from said lighting signal generation circuit with a cyclic variation determined by said detection timing signal, and modify at least one of said detection timing signal (D1) and said lighting timing signal (E1) in order to keep a constant phase difference between said cyclic variations, wherein said timing synchronization circuit (70) comprises: an oscillation circuit (78) configured to use a signal of which frequency varies with an input voltage and provide the signal as said modified detection timing signal (E1x) to said light-emitting element driving circuit, and a phase comparator (72) configured to generate a voltage indicative of a phase difference between the cyclic variation (D2) associated with the output from said light-receiving element driving circuit and the lighting timing signal (E1) from said lighting signal generation circuit, and provide said voltage to said oscillation circuit.