Detection system and image forming apparatus
A detection system including a plurality of terahertz light sources; and a plurality of terahertz-wave detecting devices which detect terahertz waves, wherein the plurality of terahertz light source includes a first terahertz light source which outputs the terahertz waves in a first on/off pattern with a first cycle, and a second terahertz light source which outputs the terahertz waves in a second on/off pattern with a second cycle which is different from the first cycle.
1. A detection system comprising:
a plurality of terahertz light sources each being configured to output terahertz waves; and
a plurality of terahertz-wave detecting devices each being configured to detect the terahertz waves output from the plurality of terahertz light sources,
wherein the plurality of terahertz light sources comprises a first terahertz light source configured to output the terahertz waves in a first on/off pattern with a first cycle, and a second terahertz light source configured to output the terahertz waves in a second on/off pattern with a second cycle which is different from the first cycle, and
the plurality of terahertz wave detecting devices comprises a first terahertz-wave detecting device configured to detect the terahertz waves in synchronization with the first on/off pattern, and a second terahertz-wave detecting device configured to detect the terahertz waves in synchronization with the second on/off pattern,
wherein the plurality of terahertz-wave detecting devices perform:
a first operation of holding a first voltage signal generated in a first period; and
a second operation of generating a second voltage signal generated in a second period and of accumulating a storage voltage determined from a differential voltage signal between the first voltage signal and the second voltage signal.
2. The detection system according to claim 1 , wherein at least one of the plurality of terahertz-wave detecting devices is capable of switching between an operation of detecting the terahertz waves in synchronization with the first on/off pattern and an operation of detecting the terahertz waves in synchronization with the second on/off pattern.
3. The detection system according to claim 1 , wherein the first cycle is other than an integral multiple of the second cycle, and the second cycle is other than an integral multiple of the first cycle.
4. The detection system according to claim 1 , wherein
in one of the plurality of terahertz-wave detecting devices, the first period is a period in which light emission of the first terahertz light source is off, and the second period is a period in which the first terahertz light source is emitting light; and
in another one of the plurality of terahertz-wave detecting devices, the first period is a period in which light emission of the second terahertz light source is off, and the second period is a period in which the second terahertz light source is emitting light.
5. The detection system according to claim 1 , wherein the plurality of terahertz-wave detecting devices perform an integral operation by repeatedly accumulating the storage voltages by repeating the first operation and the second operation.
6. The detection system according to claim 1 , wherein the plurality of terahertz-wave detecting devices include a terahertz-wave detection portion, a signal amplification portion, and a signal accumulation portion,
wherein the signal amplification portion amplifies the signal generated by the terahertz-wave detection portion to generate the first voltage signal and the second voltage signal, and
wherein the signal accumulation portion accumulates the storage voltages.
7. The detection system according to claim 6 ,
wherein the signal accumulation portion includes a clamp capacitor and a storage capacitor,
wherein the first voltage signal or the second voltage signal is applied to one end of the clamp capacitor,
wherein in the first operation, the other end of the clamp capacitor is fixed to a fixed voltage, and
wherein in the second operation, the other end of the clamp capacitor is connected to the storage capacitor.
8. The detection system according to claim 6 , wherein the terahertz-wave detection portion includes an antenna and a diode.
9. The detection system according to claim 6 , wherein the plurality of terahertz-wave detecting devices reset the signal amplification portion while the first operation is performed.
10. The detection system according to claim 6 , wherein in the plurality of terahertz-wave detecting devices, a plurality of pixels having at least the terahertz-wave detection portion, the signal amplification portion, and the signal accumulation portion are disposed in a matrix state, and output signals of the pixels are read out for each line of the matrix.
11. The detection system according to claim 10 , wherein a length of a 1-line scanning period of the first terahertz-wave detecting device which detects the terahertz waves in synchronization with the first on/off pattern of the first terahertz light source and a length of a 1-line scanning period of the second terahertz-wave detecting device which detects the terahertz waves in synchronization with the second on/off pattern of the second terahertz light source are the same.
12. The detection system according to claim 11 , wherein the numbers of the 1-line scanning periods in 1-frame periods of the first terahertz-wave detecting device and the second terahertz-wave detecting device are the same.
13. The detection system according to claim 11 , wherein the numbers of the 1-line scanning periods in the 1-frame periods of the first terahertz-wave detecting device and the second terahertz-wave detecting device are different, and the one with the smaller number of accumulation times in the 1-line scanning period has a larger number of the 1-line scanning periods in the 1-frame period.
14. The detection system according to claim 11 , wherein in the first terahertz-wave detecting device and the second terahertz-wave detecting device, the 1-line scanning periods start in synchronization.
15. The detection system according to claim 11 , wherein in the first terahertz-wave detecting device and the second terahertz-wave detecting device, the 1-frame periods start in synchronization.
16. The detection system according to claim 11 , wherein a blanking period is provided in the 1-line scanning period or the 1-frame period.
17. The detection system according to claim 10 , wherein
a length of the 1-line scanning period of the first terahertz-wave detecting device which detects terahertz waves in synchronization with the first on/off pattern of the first terahertz light source and a length of the 1-line scanning period of the second terahertz-wave detecting device which detects the terahertz waves in synchronization with the second on/off pattern of the second terahertz light source are different, and
at least any one of formula 1, formula 2, and formula 3 below is satisfied:
( A− 1)× M =( B− 1)× N Formula 1
A<B, M>N Formula 2
A>B, M<N Formula 3
A: Number of 1-line scanning periods in a 1-frame period of the first terahertz-wave detecting device;
B: Number of 1-line scanning periods in the 1-frame period of the second terahertz-wave detecting device;
M: Number of on/off patterns with the first cycle in the 1-line scanning period of the first terahertz-wave detecting device; and
N: Number of on/off patterns with the second cycle in the 1-line scanning period of the second terahertz-wave detecting device.
18. An image forming apparatus comprising:
a plurality of terahertz light sources each being configured to output terahertz waves; and
a plurality of terahertz-wave detecting devices each being configured to detect the terahertz waves output from the plurality of terahertz light sources,
wherein the plurality of terahertz light sources includes a first terahertz light source configured to output the terahertz waves in a first on/off pattern with a first cycle, and a second terahertz light source configured to output the terahertz waves in a second on/off pattern with a second cycle which is different from the first cycle,
each of the plurality of terahertz-wave detecting devices has pixels having at least a terahertz-wave detection portion, a signal amplification portion, and a signal accumulation portion and disposed in plural in a matrix state, and
the plurality of terahertz detecting devices includes a first terahertz-wave detecting device configured to detect the terahertz waves in synchronization with the first on/off pattern, and a second terahertz-wave detecting device configured to detect the terahertz waves in synchronization with the second on/off pattern,
wherein the plurality of terahertz-wave detecting devices perform:
a first operation of holding a first voltage signal generated in a first period; and
a second operation of generating a second voltage signal generated in a second period and of accumulating a storage voltage determined from a differential voltage signal between the first voltage signal and the second voltage signal.