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Indoor high precision range finder

**Introduction **

Indoor high precision range finder is generally used for indoor distance measurement, compact and easy to measure. The finder is replacing the traditional tape measurements in the field of construction or decoration.

Typical range is about 60 meters .

Tolerance：+-(1~2mm)

Wavelength of laser：635nm,650nm

The power of emergent laser light：<1mw

**Portable laser rangefinder**

**Brief introduction of principle **

The frequency of radio band is used to modulate the amplitude of laser beam in phase laser ranging. The phase delay of one-round-trip modulated light is measured, and then the distance represented by the phase delay is converted according to the wavelength of modulated light. It’s an indirect method to determine the time required for the light to travel back and forth through the measuring line.

The specific formula is as follows:

The angular frequency of the modulated light is set asω, the phase delay generated by one round trip on the distance D to be measured is set as φ.

Corresponding time is set as t.
Thus,

t=φ/ω. (1)

D=(1/2 )*c*t (2)

Substituting (1) into (2) leads to:

D=1/2 ct=1/2 c•φ/ω

ω=2πf

Obtain：

D=c/(4πf) (Nπ+Δφ)= =c/4f (N+ΔN)

φ - The total phase delay generated by the signal one-round-trip.

ω - Angular frequency of modulated signal, ω=2πf,ω=2πf。

U - Unit of length, equal to 1/4 modulated wavelength

N - the number of modulated half wavelengths contained in the line

Δφ - the part less than π generated from the phase delay of the signal travel one around in the line

ΔN - the fractional part of the modulated wave contained in the line less than half wavelength

ΔN=φ/ω

The frequency c/(4πf) is a constant under given modulation and standard atmospheric conditions. At this time, the distance measurement becomes the measurement of the number of half wavelength and the fraction of less than half wavelength contained in the line, namely, N or φ.

**Schematic block diagram**

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**Recommended model **

Emitter (LD)

ADX-6305STU

Receiver (APD)

AD230-8 (TO package , LCC6.1)

AD100-8 ( TO package, LCC6.1)

AD500-8 ( LCC6.1)

RM 707-708, 258 Guoxia Road, Yangpu District,Shanghai, China PC:200433

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