US 12,481,039 B2
Photoelectric sensor and optical rangefinder
Akihito Yamamoto, Osaka (JP); Takahiro Kasahara, Osaka (JP); Satoshi Arima, Osaka (JP); and Tatsuhiro Momodori, Osaka (JP)
Assigned to HOKUYO AUTOMATIC CO., LTD., Osaka (JP)
Appl. No. 18/019,699
Filed by HOKUYO AUTOMATIC CO., LTD., Osaka (JP)
PCT Filed Aug. 18, 2021, PCT No. PCT/JP2021/030146
§ 371(c)(1), (2) Date Feb. 3, 2023,
PCT Pub. No. WO2022/039186, PCT Pub. Date Feb. 24, 2022.
Claims priority of application No. 2020-137786 (JP), filed on Aug. 18, 2020.
Prior Publication US 2023/0314572 A1, Oct. 5, 2023
Int. Cl. G01S 7/4863 (2020.01); G01S 7/481 (2006.01); G01S 7/4865 (2020.01); G01S 7/489 (2006.01); G01S 17/10 (2020.01)
CPC G01S 7/4863 (2013.01) [G01S 7/4817 (2013.01); G01S 7/4865 (2013.01); G01S 7/489 (2013.01); G01S 17/10 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A photoelectric sensor for detecting an object in a monitored area, comprising:
a light emitting unit configured to emit measurement light to the monitored area;
a light receiving unit configured to convert reflected light into a current signal, the reflected light being a diffuse reflection of the measurement light from an object;
a preamplifier configured to convert the current signal converted by the light receiving unit into a voltage signal;
a first signal processing chain including a first amplifier and a first binarization circuit, the first amplifier being configured to amplify a preamplified signal output from the preamplifier by a first amplification factor A1, the first binarization circuit being configured to binarize a first output signal output from the first amplifier using a first threshold Vth1;
a second signal processing chain including a second amplifier and a second binarization circuit, the second amplifier being configured to amplify the preamplified signal output from the preamplifier by a second amplification factor A2, the second binarization circuit being configured to binarize a second output signal output from the second amplifier using a second threshold Vth2;
a distance calculation circuit configured to calculate (i) a first distance from the photoelectric sensor to an object based on an emission time of the measurement light emitted from the light emitting unit and a rising time of a first binary signal output from the first signal processing chain and (ii) a second distance from the photoelectric sensor to the object based on the emission time of the measurement light emitted from the light emitting unit and a rising time of a second binary signal output from the second signal processing chain, wherein the calculated first distance and second distance are written into a memory; and
an output selection circuit configured to output the first distance and not output the second distance in response to determining that a difference between the first distance read from the memory and the second distance read from the memory is less than a predetermined distance threshold, wherein
the first threshold Vth1 and the second threshold Vth2, and the first amplification factor A1 and the second amplification factor A2 are set so as to satisfy the following relational expression:
1<(Vth2/Vth1)<α=(A2/A1).