1. An optical scanner comprising:
a light source configured to emit light;
a light source driving device configured to drive the light source;
a light deflector having at least one rotating reflection plane and configured to deflect the light emitted from the light source to a scanning area; and
a light detector configured to output a signal to control a timing at which scanning of the scanning area by the light deflected by the light deflector starts,
the light detector and the scanning area being sequentially scanned in a single scanning by one of the at least one rotating reflection plane of the light deflector,
the light source driving device driving the light source using a first driving method when the light deflected by the light deflector scans the light detector, and driving the light source using a second driving method that is different from the first driving method when the light deflected by the light deflector scans the scanning area.
2. The optical scanner according to claim 1, wherein the light source driving device drives the light source to emit light continuously in the first driving method, and drives the light source to emit pulses of light in the second driving method.
3. The optical scanner according to claim 1, wherein the light source driving device includes a first current path that corresponds to the first driving method and a second current path that corresponds to the second driving method.
4. The optical scanner according to claim 3, wherein
the light source driving device includes a power source and a capacitor,
the first current path is a current path through which electric current is mainly supplied from the power source to the light source, and
the second current path is a current path through which electric current is mainly supplied from electric charge accumulated in the capacitor to the light source.
5. The optical scanner according to claim 1, wherein a peak value of an optical output of the light source in the second driving method is set to be at least a hundred times greater than a peak value of an optical output of the light source in the first driving method.
6. The optical scanner according to claim 1, wherein
an output signal of the light detector is a pulse signal that is synchronized with a rotation of the reflection plane of the light deflector, and
the light source driving device determines a light emission interval in the second driving method based on the output signal of the light detector.
7. The optical scanner according to claim 6, wherein the light source driving device determines the light emission interval in the second driving method based on an immediately preceding pulse interval in the output signal of the light detector.
8. The optical scanner according to claim 6, wherein
the light deflector has n reflection planes, where n is an integer equal to or greater than 2, and
the light source driving device determines the light emission interval in the second driving method based on a n-th previous pulse interval in the output signal of the light detector.
9. The optical scanner according to claim 6, wherein
the light deflector has n reflection planes, where n is an integer equal to or greater than 2, and
the light source driving device determines the light emission interval in the second driving method based on an average of from a n-th previous pulse interval to an immediately preceding pulse interval in the output signal of the light detector.
10. An object detector comprising:
the optical scanner according to claim 1, and
a light receiving device configured to receive light that is emitted from the optical scanner to a scanning area and is reflected at an object when the object is placed within the scanning area.
11. The object detector according to claim 10, wherein in the second driving method, the light source driving device of the optical scanner drives the light source to emit pulses of light with a duty ratio equal to or less than 1 percent.
12. The object detector according to claim 10, wherein
in the first driving method, the light source driving device of the optical scanner drives the light source to emit light continuously for equal to or longer than 1 \u03bcs, and
in the second driving method, the light source driving device of the optical scanner drives the light source to emit pulses of light with a pulse width of equal to or shorter than 100 ns.
13. A sensing apparatus comprising:
the object detector according to claim 10; and
a monitoring controller configured to determine whether or not an object is present, and obtain at least one of position and speed of the object, based on output from the object detector.
14. The sensing apparatus according to claim 13, wherein
the sensing apparatus is mounted on a vehicle, and
the monitoring controller determines whether or not there is danger based on at least one of information on position and movement of the object.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An antenna device comprising:
an antenna having a feeding point and an end portion apart from the feeding point, the end portion being an open end;
a variable impedance matching circuit connected to the antenna at the feeding point;
a probe placed in such a position that a distance from the end portion to a tip of the probe is equal to or shorter than one eighth of a wavelength corresponding to a maximum radio frequency used in the antenna device; and
a controller controlling the variable impedance matching circuit based on an electrical signal measured with the probe, the controller being connected to the probe.
2. The device according to claim 1, wherein a resonant frequency of the probe is higher than the maximum radio frequency.
3. The device according to claim 1, wherein the probe is a differential probe.
4. The device according to claim 1, wherein
the antenna has a shape splitting into branches when seen from the feeding point,
end portions of all the branches are open ends, and
the probe is placed in such a position that each of the distances from the end portions to the tip of the probe is equal to or shorter than one eighth of the wavelength corresponding to the maximum radio frequency used in the antenna device.
5. The device according to claim 1, wherein
the controller comprises:
a power detector connected to the probe;
an AD converter converts an analog output of the power detector into binary data;
a buffer stores binary data at a certain sampling time;
a comparator compares a value of the binary data from the AD converter with a value of the binary data stored in the buffer; and
an updown counter having the number of counts increasing or decreasing with comparison logic performed by the comparator, a binary output of the updown counter being connected to a plurality of variable impedance elements in the variable impedance matching circuit.
6. The device according to claim 1, wherein
the controller comprises:
a power detector connected to the probe;
an AD converter converts an analog output of the power detector into binary data;
a first buffer stores the binary data at a first time;
a second buffer stores binary data at a second time, the second time being one sampling time before the first time;
a comparator compares a value of the binary data stored in the first buffer with a value of the binary data stored in the second buffer;
an updown counter having the number of counts increasing or decreasing with comparison logic performed by the comparator; and
a DA converter outputs a bias voltage to the variable impedance matching circuit in accordance with a binary value of the number of counts in the updown counter.
7. The device according to claim 1, further comprising
a power amplifier connected to the opposite side of the variable impedance matching circuit from the antenna,
wherein
a gain signal of the power amplifier is input to the controller, and
based on the gain signal, the controller controls the variable impedance matching circuit.
8. The device according to claim 1, wherein the antenna is an inverted L antenna.
9. The device according to claim 1, wherein the variable impedance matching circuit comprises a variable inductor and a variable capacitor.
10. The device according to claim 1, wherein the variable impedance matching circuit comprises a variable-capacitance diode and an inductor.
11. A wireless communication apparatus comprising
an antenna device and a wireless device,
the antenna device comprising:
an antenna having a feeding point and an end portion apart from the feeding point, the end portion being an open end;
a variable impedance matching circuit connected to the antenna at the feeding point;
a probe placed in such a position that a distance from the end portion to a tip of the probe is equal to or shorter than one eighth of a wavelength corresponding to a maximum radio frequency used in the antenna device; and
a controller controlling the variable impedance matching circuit based on an electrical signal measured with the probe, the controller being connected to the probe,
the wireless device being connected to the opposite side of the variable impedance matching circuit from the antenna.
12. The apparatus according to claim 11, wherein a resonant frequency of the probe is higher than the maximum radio frequency.
13. The apparatus according to claim 11, wherein the probe is a differential probe.
14. The apparatus according to claim 11, wherein
the antenna has a shape splitting into branches when seen from the feeding point,
end portions of all the branches are open ends, and
the probe is placed in such a position that each of the distances from the end portions to the tip of the probe is equal to or shorter than one eighth of the wavelength corresponding to the maximum radio frequency used in the antenna device.
15. The apparatus according to claim 11, wherein
the controller comprises:
a power detector connected to the probe;
an AD converter converts an analog output of the power detector into binary data;
a buffer stores binary data at a certain sampling time;
a comparator compares a value of the binary data from the AD converter with a value of the binary data stored in the buffer; and
an updown counter having the number of counts increasing or decreasing with comparison logic performed by the comparator, a binary output of the updown counter being connected to a plurality of variable impedance elements in the variable impedance matching circuit.
16. The apparatus according to claim 11, wherein
the controller comprises:
a power detector connected to the probe;
an AD converter converts an analog output of the power detector into binary data;
a first buffer stores the binary data at a first time;
a second buffer stores binary data at a second time, the second time being one sampling time before the first time;
a comparator compares a value of the binary data stored in the first buffer with a value of the binary data stored in the second buffer;
an updown counter having the number of counts increasing or decreasing with comparison logic performed by the comparator; and
a DA converter outputs a bias voltage to the variable impedance matching circuit in accordance with a binary value of the number of counts in the updown counter.
17. The apparatus according to claim 11, wherein
the antenna device further comprises a power amplifier connected to the opposite side of the variable impedance matching circuit from the antenna,
a gain signal of the power amplifier is input to the controller, and
based on the gain signal, the controller controls the variable impedance matching circuit.
18. The apparatus according to claim 11, wherein the antenna is an inverted L antenna.
19. The apparatus according to claim 11, wherein the variable impedance matching circuit comprises a variable inductor and a variable capacitor.
20. The apparatus according to claim 11, wherein the variable impedance matching circuit comprises a variable-capacitance diode and an inductor.