Optoelectronic device

An optoelectronic device comprising:

• a light emitter for emitting a light beam on a reflection medium, a light-beam-dividing element having a first diffraction grating region and a second diffraction grating region located in the vicinity of the first diffraction grating region, being located between the light emitter and the reflection medium, and a photodetector for receiving light diffracted at the diffraction grating region of the light-beam-dividing element, among returning light beams reflected by the reflection medium, wherein
• an entire light beam emitted from the light emitter enters the first diffraction grating region and is reflected by the reflection medium, whereby the photodetector receives only a portion of the returning light that passes through the first diffraction grating region,
• the second diffraction grating region prevents the portion of the returning light beam which enters the second diffraction grating region from entering the photodetector, where the returning light beams are ±first order diffracted light generated when a light beam emitted from the light emitter enters the first diffraction grating region and is reflected by the reflection medium,
• the second diffraction grating region has a 0th-order diffraction efficiency of light reflected by the reflection medium that is 5% at most, and
• the second diffraction grating region has a convexity and a concavity different from each other in the optical path length by m/2 times a wavelength of the reflected light, where m denotes an odd number.

An optoelectronic device comprising:

• a light emitter for emitting a light beam on a reflection medium;
• a light-beam-dividing element having a first diffraction gating region and a second diffraction grating region located in the vicinity of the first diffraction grating region, being located between the light emitter and the reflection medium;
• a photodetector for receiving light diffracted at the diffraction grating region of the light-beam-dividing element, among returning light beams reflected by the reflection medium;
• and
• a plurality of photodetectors, each of which is located between a spot of mth-order diffracted light and a spot of (m+1)th-order diffracted light of the returning light beam provided by second diffraction grating region located in an optical axis direction of the returning light beam with respect to the other photodetector, where m denotes an integer,
• wherein an entire light beam emitted from the light emitter enters the first diffraction grating region and is reflected by the reflection medium, whereby the photodetector receives only a portion of the returning light that passes through the first diffraction grating region,
• the second diffraction grating region prevents the portion of the returning light beam which enters the second diffraction grating region from entering the photodetector, where the returning light beams are ±first order diffracted light generated when a light beam emitted from the light emitter enters the first diffraction grating region and is reflected by the reflection medium, and
• the second diffraction grating region has a 0th-order diffraction efficiency of light reflected by the reflection medium that is 5% at most.