Evaluating Laser Rangefinder

Evaluating The Performance Of A Laser Rangefinder

A laser rangefinder, laser range finder, eye safe laser rangefinder performance is mainly see working distance, measuring rate and reliability life.

  •  The maximum range depends on a target type, albedo, angle, size, shape and rate as well as weather conditions. 

 

1,   If target type is different, then albedo is very different. Tank albedo is very different with 2.3m x 2.3m target, 2.3m x 2.3m target can be reflective plate that even albedo can be 90%.

       For example:

       one LRF measure high albedo 2.3m x 2.3m target 12km, then said their LRF that measure NATO 2.3m x 2.3m 30% reflectivity target 12km. this is why many 30% albedo NATO 2.3m x 2.3m target 12km laser rangefinder can not measure tank 10km in standard 23.5km visibility.

 

       In fact, when one LRF measure big target 20km in standard 23.5km visibility, then, normal measure 30% albedo 2.3m x 2.3m target can only ensure 9km and at most 12km with same condition.

       Then, when you see one LRF for 2.3m x 2.3m target 10% reflection 10km in 10km visibility or 2.3m x2.3m target 18km in 23km visibility, you can ask for why the LRF can only measure big target about 20km in 23.5km visibility.

      Or, when you see one LRF for max range 12km, then you can ask for how to measure 2.3m x 2.3m vehicle 10km.

 

 

 2,   If effect area is differnt, then measuring distance is different too, For example, tank have many types, also tank have front, side, behind etc, their effect area is different. 

       For example:

      one LRF measure 10 square meter vehicle 12km, then normal measure 5 square meter vehicle is about 10km.

      Also, when the angle of the LRF to the target changes, then, measuring range will change too, even rapidly changing.

 

 

 3,   When LRF increases the measurement frequency, then, LRF distance performance will decay, even decay rapidly. normal eye safe high rate mid-long range LRF laser energy need 5mJ and at least 2mJ.

       For example, 

      when one LRF measure tank 10km with 1Hz, then, if use for 10Hz measuring rate, then maybe the LRF measure tank is only 7km.

     When this LRF laser energy is very low, then attenuation speed will accelerate, even only balance less than 40% for 1Hz to 10Hz.

 

 

4,   Air visibility will affect distance performance, when air visibility is very bad, then distance performance will decay rapidly.

     For example,

     500m visibility is very different with 20km visibility. this is why many LRF is only said 2.3m x 2.3m vehicle 8km without any air visibility contidtion.

 

 

 5,    Continuous measurement and single measurement mean is very different, especially low energy Erbium-glass laser and fiber optic laser.

       For example:

       1Hz 2minutes 10km and 1Hz single measurement 10km is very different, when 1Hz is single measurement, then, normal typical rate is only 10ppm to 12ppm (0.2Hz) continuous.

       Some low energy LRF can be 1Hz continuous 2minutes, but, the starting measuring distance is different from the final measuring distance for max distance. This is very evident under the relevant standard conditions, especially strict and extreme measurement conditions.

 

 

6,    Temperature condition will affect some LRF distance performance.

        For example:

       some LRF can measure max 18km in -20ºC, when temperature is -40ºC, then max disance is only 12km and even do not work.

 

 

  • Each one LRF have own typical measuring rate, some LRF have also max measuring rate mode and burst mode, burst mode measuring rate is very different with typcial measuring rate.

       

       For example,

       one LRF burst mode measuring rate is 6Hz continuous 30 seconds, then maybe typical measuring rate is only 1Hz continuous, when use for 3Hz measuring rate, then normal 3Hz can be continuous about 1 minute;

       one LRF burst mode measuring rate is 1Hz contnuous 20 seconds, then maybe typical measuring rate is only 10ppm continuous to 0.2Hz continuous;

       One LRF burst mode measuring rate is 3Hz, then, typical measuring rate is only 0.5Hz continuous, when use for 1Hz measuring rate, then 1Hz is only continuous about 1 minute(some model can be 90 seconds to 2 minutes). 

       One LRF single measurement is 1.5 seconds, in fact, the measuring rate is burst mode,  real typical measuring rate is only 5ppm to 8ppm, especially low energy LRF.

 

      Also, LRF must note meausring rate details, then can show the LRF real performance.

      For example, typical 1Hz continuous 10minutes is very different with typical 1Hz continuous 30 seconds.  this is why many LRF meausring rate is only show 5Hz, 1Hz, 0.5Hz without any details.

This is why 6Hz burst mode and 3Hz burst mode typical measuring rate performance is lower than typical 1Hz continuous 10minutes.

 

  • Each one LRF have own typical reliability life, typical reliability life is LRF overall life performance, including all LRF part life and technological level . when use for cheap cost part or only assembled, then LRF cost can reduce, even reduce much, this is why some LRF do not show their reliability life and only said price is cheap.

     

       For example,

      one LRF reliability life is 20000 range measurement is lower than 100000 range measurement, many cheap LRF reliability life is only 5000 to 20000 range measurement, even lower than 5000 range measurement.

Shot lifetime is only set laser life or one part module life, such as Xenon lamp, diode pump etc, that is only one part for LRF.

       Also, if working temperature condition is different, then shot lifetime is different too, even very different.

This is why normal best LRF reliability life can ensure at least 1000000 range measurement.

      Then, when one LRF is used for bad cable, messy interface, messy wiring etc, then you can ask for how to warranty reliability life.

 

 Here are some examples of bullshit:
 

1, One Europe compact 1.5µm 32km LRF write :

           Ranging capability:                     32km, 

           Extinction Ratio:                         41.2dB with 500 m, visibility 23 km and target reflectivity 85 %, 

           NATO target:                               12km with Target size 2.3 x 2.3 m, visibility 25 km, reflectivity 30 %,

          Single Measurement Mode:          1.5 seconds,

          Continuous Measurement mode:   1, 4, 10, 20,100, 200Hz.

         Show some video and image to prove it.

 

  • how to ranging 32km? no one knows.

    show video and image is only 21.9km for big target in good visibility and good condition too.
     
  • If 21.9km is at 23km visibility, then, normal 30% albedo NATO target is at most 11km, how to measure 12km?

    when then visibility is more than 23km, then, 30% albedo NATO target distance will reduce at 23km visibility.


     
  • When extinction ratio 41.2dB is real, then, normal only ensure 8km and at most 10km for 30% albedo NATO target with same condition, then, how to measure 12km for 30% albedo NATO target?


      maybe their 30% albedo NATO target is one type about 50% albedo 2.3m x 2.3m reflective plate.
 

  • If ensure 12km for 30% albedo NATO target, then, normal corresponding extinction ratio is at least 45dB with 500m 85% reflectivity and 23 visibility.


      So, is this a machine lying or a human lying?
 

  • When single measurement mode is 1.5 seconds, then, typical measuring rate is only 5ppm to 8ppm continuous, if laser energy is very low, even no have continuous mode;

    then, 1Hz continuous is from where? here is not say 4Hz, 10Hz, 100Hz and 200Hz continuous.

 

 

2, One Europe compact 1.5µm 39km LRF write :

            Ranging capability:                        39km,

           Extinction Ratio:                             45dB with 500 m, visibility 23 km and target reflectivity 85 %, 

           NATO target:                                   17.3km with target 2.3 x 2.3 m, visibility 25 km, and reflectivity 30 %,

           Single Measurement Mode:             1.5 seconds,

           Continuous Measurement mode:     1, 4, 10, 20,100, 200Hz.

 

          Extinction Ratio:                              36.5dB with 500 m, visibility 23 km and target reflectivity 85 %,

          NATO target:                                    7.3km with Target size 2.3 x 2.3 m, visibility 25 km,reflectivity 30 %,

          Continuous Measurement Mode:     10Hz.

 

  • how to ranging 39km? no one knows.
     
  • When extinction ratio 45dB is real, then, normal only ensure about 11km and at most 14km for 30% albedo NATO target with same condition, then, how to measure 17.3km for 30% albedo NATO target?


       maybe their 30% albedo NATO target is one type beyand 50% albedo 2.3m x 2.3m reflective plate.
 

  • If ensure 17.3km for 30% albedo NATO target, then, normal corresponding extinction ratio is at least 50dB with 500m 85% reflectivity and 23km visibility.


       So, is this a machine lying or a human lying?

 

  • When single measurement mode is 1.5 seconds, then, typcial measuring rate is only 5ppm to 8ppm continuous, if laser energy is very low, even no have continuous mode;
     
  • About 10Hz continuous measurement mode, how to continuous? no one knows.

    If laser energy is not high, 10km LRF measuring rate may be up to 10Hz single measurement or at most 10Hz burst, then, how to 10Hz continuous?

    Normal very low energy LRF no have real high rate continuous measurement mode with mid-long range.

 

 

3, One China 1570nm 1Hz-10Hz 50km LRF write :

           Ranging capability:                     50km for large targets, visibility≥40km, 

           Vehicle:                                        25km with 2.3m×2.3m, 0.3 reflectivity vehicle, visibility≥35km.

           Measurement rate:                       1~10hz(adjustable) .

           Receiver aperture :                      67mm,

           Divergence angle:                        0.6mrad

           Laser energy:                               10mJ

          Show calculation formula and calculation method to prove it.

 

  • Can theory data use in real world? 

    This is a large listed company that claims to have relevant background in R&D and production, this LRF introduction is from the company.

    Here is not say calculation formula and calculation method.

     
  • How to ranging 50km typical large target with 1-10Hz rate and 40km visibility for 10mJ laser energy plus 67mm received apeature? 

    Simple 10mJ energy plus mid-big received apeature can measure 50km?

    1Hz and 10Hz ranging capability is same? here is not say 1Hz continuous and 10Hz continuous too.

    When you do real test, you will know that is a joke.

     
  • How to ranging 25km with 30% albedo 2.3m x 2.3 target 1-10Hz rate and 35km visibility for 10mJ laser energy plus 67mm received apeature? ?

    1Hz and 10Hz ranging capability is same? here is not say 1Hz continuous and 10Hz continuous too.

    When you do real test, you will know that is a joke.

     
  • So, when you test it with relevant standard, you do not know this LRF is what.

    If make 50km laser rangefinder is very easy and very simple, marketed decades ago.

    This is why many companies spend a long time researching to successfully provide 1Hz-10Hz continuous 10km -20km laser rangefinder with relevant standard, then, but price is not cheap.

    Here is not say real 25km-50km and even 120km 1Hz-40Hz continuous LRF.

 

 

 

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