What is LIDAR | Laser Radar

What is LIDAR | Laser Radar | LIDAR or LADAR

This page covers Laser radar.This radar is also referred as LIDAR or LADAR. It differentiates LADAR vs RADAR and mentions similarities and difference between RADAR and LADAR. Advantages, disadvantages, applications, LIDAR classification OR types are also mentioned.

The radar which uses laser for its operation is referred as Laser Radar or LADAR or LIDAR. The full form of Laser is Light Amplification by Stimulated Emission of Radiation. The full form of LIDAR is LIght Detection And Ranging.

Ladar uses 3 semiconductor diodes to generate laser light. It uses light pulses to make two consecutive distance measurements. Then divides by time. Lenses are utilized to collimate light to narrow beam. Typically ANSI clas-I laser devices are used.

The Laser radar i.e. LIDAR consists of laser, receiver and clock. It has larger aperture gain and larger bandwidth. Hence very accurate measurement can be performed. LIDAR receiver antenna is usually not shared with transmitter part. The receiver antenna focuses incoming radiated waves to a point size. As we know EM energy at high frequencies is referred as photons or quanta.

LIDAR operates on the principle of envelope detection system which is incoherent. RCS of LIDAR is expressed by the following equation:
RCS of laser radar, σ_l = ρ * { (4*π*A²)/λ² }
Where,
ρ is reflectivity of target
A is effective intercepting area of the object or target.

Figure depicts LIDAR or LADAR system. This UPC Backscatter LIDAR has following specifications:

LASER PART:
• Energy: 0.5 J/532 nm, Divergence: 0.1 mrad, Pulse length: 10 ns, PRF: 10 Hz

RECEIVER PART:
Focal length: 2 m, Aperture φ : 20 cm, Detector: APD, Bandwidth: 10 MHz

SYSTEM SPECS:
Configuration: vertical biaxial, Acquisition: 20 MSPS/12 bit, Spacial resolution: 7.5 m, min. det. power < 5 nW.

LIDAR Classification OR Types

➨Based on their APPLICATION:
• ELASTIC-BACKSCATTER LIDAR
• WIND LIDAR (Doppler lidar)
• SPECTROSCOPIC LIDAR

➨Based on their CONFIGURATION:
• MONO-STATIC LIDAR: Backscatter, DIAL, Raman, Doppler, Fluorescence etc.
• BI-STATIC LIDAR: Long path absorption Airborne (plane,helicopter,satellite), mobile, ground based etc.

Advantages or applications of LADAR or LIDAR

Following are the applications or advantages of LIDAR (i.e. LADAR):
• It helps in precise distance measurements.
• It helps in measurement of atmospheric densities and atmospheric currents.
• It helps to obtain 3D images of objects with high resolution.
• It helps to obtain images of missiles which are at long distances by placing them in spacecraft.
• It can even recognize slow moving objects due to larger doppler shift phenomenon.

Disadvantages of LIDAR or LADAR

Following are the disadvantages of LIDAR (i.e. LADAR):
• It has limited capability to penetrate inside smoke, rain, fog, dust, clouds etc.
• It do not provide satisfactory performance for surveillance applications.
• Tracking using LADAR is difficult.

LADAR vs RADAR-Similarities and difference between RADAR and LADAR

Let us understand similarities and difference between RADAR and LADAR:
➨LADAR range equation is same as radar equation.
➨LIDAR or LADAR = LASER + RADAR , Radar uses EM waves while Ladar uses laser.
➨Ladar uses light emitted at 904 nm. It can use different wavelength depending upon object material.
➨Also refer LiDAR vs RADAR >> for difference between LiDAR and RADAR systems.