Lidar Functions

Chapter 8.1
• Operation
• Physical Configurations
• Controls
• Aim Dot / Displays

Operation

• Transmits in Infrared Band
  -- typically 904 nm (± 5 nm) wavelength
• Beamwidth
  3 - 4 milliradians (0.17° - 0.23°)
• Sample Time (minimum time to get one speed measurement)
  -- typically 0.3 - 0.7 seconds (300 ms - 700 ms)
• Pulse Width
  5 - 35 nanoseconds (ns)
• PRF (Pulse Repetition Frequency)
  100 - 500 Hertz (pulses per second)
• Maximum Range
  2000 feet or about 600 meters (on a good day if lucky)

Many lidars have a Timing Mode. The range between two points is entered into (measured by) the lidar, the operator pushes a button when a target passes between the two points and the lidar displays the calculated speed (without transmitting).

Lidars do not have a moving mode.

Physical Configurations

Most lidars are hand-held single unit devices. Many models have optional tripods to make it easier for the operator to keep the beam center on the same spot on a moving target (vehicle). Some models have a shoulder mount to keep the lidar steady while tracking a vehicle.

• Single unit with Scope / HUD -- hand-held lidar gun
  (power supplied by car battery and/or internal battery)
  
• Binoculars Style -- hand-held
  (power supplied by internal battery)

Controls

• Power (On/Off)
• Trigger (transmits only when pressed)
  -- holds last speed/range measurement when depressed.
  -- clears measurements when pressed again.
• Range -- Sets maximum range for speed measurements.
• Traffic Direction
  -- On-coming
  -- Going
  -- On-coming or Going
• Audio Volume -- Aim and Speed tones.
  -- strong AIM tone when reflection strong.
  -- speed tone proportional to measured speed.
• Display (and/or HUD) Brightness
• Test (self-test mode)
• Speed Threshold -- Speed that triggers external signal(s) to other devices (cameras).

Aim Dot / Displays

• Aim (point) Device
  • HUD -- Heads-Up-Display (aim dot/speed/range projected to clear glass so operator can view traffic/data).
    
  • Scope -- Rifle type scope with aim cross-hairs.
    
  • Binoculars -- Aim Dot/Speed/Range projected onto one eye piece.
• Speed Display
  -- has a minimum and maximum speed measuring range
  -- mph, km/hr (some models operator selects)
  -- Traffic Direction (not all models) indicates on-coming (approaching) or going (receding) traffic.
• Range Display
  -- has a minimum and maximum range (feet or meters)
• Speaker (Aim and Speed tones)
  -- strong AIM tone when reflection strong.
  -- speed tone proportional to measured speed.
• Indicators (typical)
  
  • TRANSMIT / STANDBY (ON)
    -- TRANSMIT -- lidar transmitting
    -- STANDBY -- lidar on but not transmitting
  • RFI -- Radio Frequency Interference
    -- Most models inhibit speed measurements.
  • BIT ERROR -- Built-in-test error
    -- lidar test (automatically and/or operator initiated) portion of electronics.
  • LOW VOLTAGE -- power (voltage) below specification.
    -- operation inhibited, some models display warning.
  • POWER ON/OFF -- Radar On
    -- Many units run self-test (several seconds) on power-up.