Rangefinder Signal Processing Development

LRF & LIDAR Time of Flight & Phase Intermixed Signal Processing within a Low Cost Microcontroller

You can buy a Laser rangefinder on Alibaba for under $65 in volume. It will make all sorts of claims about its range capability and eye safety which are misleading. They have high angular divergence, poor filtering and modelling can prove they can only achieve the range to a 90% white card the size of a car.

You can pay over $500 in high volume for an OEM LRF module to embed in your sighting system and get a beautifully engineered precision optical device that uses a Power hungry DSP which will do what it claims. Low reflectivity and a smaller target. But it will eat your battery life.

The largest market for rangefinding outside of the Golf market is Outdoor Hunting. The target you are aiming at is usually small, low reflectivity and part concealed by leaves. You need the $500 performance......but you only have a $50 budget. You want your battery to last.  Here is what Photonsens is tryng to do to help...


Q.   What is Our design goal?

We intend to offer licensees a reference design for an OEM LRF that can be placed within their sighting scope that offers 2000metre range, Class 1 eye safe performance to an 18% albedo 0.7x0.7m sized target. It will be deployed within a very low cost micro-controller with low power consumption. It will offer 2mm range accuracy and pulse pair separation of ~ 2metres

Q.    What is the essential ingredient that will enables us to offer this?

Photonsens sells some excellent rangefinder technology for 15,000metre ranging (that's at 1550nm so don't get too excited about using it in a $50 LRF). There are many attributes to a good LRF design which we intimately understand. I stand by all of the products I sell as being superbly positioned for their intended markets.

Patents have come and gone, and patents still exist which are valid which allow multiple pulses to be transmitted and correlated to allow for below noise floor detection. Many have fundamental weaknesses which make them incompatible with the latest eye safety requirements of EN60825-1:2014 which stipulates limits on the Peak Power, Power within a Pulse train and on the average power that are extremely limiting at 905nm. We believe we have understood those limits and have developed an elegant implementation that allows us to deliver a low cost platform.

Previous correlation technologies also rely either upon Digital Signal Processing which is power hungry and relatively costly, or offer poor accuracy in the order of >10cm. Our signal processing can be coded to perform additional functions which will improve accuracy by more than an order of magnitude. 

We have also witnessed very poor hardware implementation of laser and APD circuitry which adds ambiguity and degrades actual performance against the theoretical capabilities of the algorithm. We are developing a hardware solution which enables the full potential to be reached.

Q.    How will we prove our platform works?

Our partners will work with us under NDA. We will present them with modelling data for a baseline reference design which we will then demonstrate via working hardware to prove the model.

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