Hacker News Reader

Comment by fisherjeff | Hacker News Reader

Based on the diagram, I believe they're estimating distance based on parallax rather than time of flight

I agree.

The wikipedia article on LIDAR says

"Lidar [...] combine[s] laser-focused imaging with the ability to calculate distances by measuring the time for a signal to return using appropriate sensors and data acquisition electronics."

So this is not LIDAR. Still impressive though, I love the simplicity!

That's probably an overly specific definition. Their source for the lidar definition is a NOAA webpage [0] with a broader definition that doesn't include specifics about implementation:

> LIDAR, which stands for Light Detection and Ranging, is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth.

Most lidar does use timing but I'd argue that's a type of implementation instead of a necessary part of the broader category of lidar devices.

[0] https://www.webcitation.org/6H82i1Gfx?url=http://oceanservic...

The LIDAR acronym doesn't specify the specific measurement technique, although Time Of Flight is by far the most common. There are other designs with interesting differences, for example Strobe[0] which varies the frequency of the transmitted light and measures the freq and phase delay of the returning light rather than straight delay.

I believe this design still qualifies as LIDAR, just with significantly worse performance than a typical system.

[0] https://spectrum.ieee.org/cars-that-think/transportation/sel...

For me paralax-based sensors (in the sense of draw a line with swept laser and look at it with some kind of imager) are the first thing I imagine when hearing "LIDAR". For a long time most industrial lidar sensors used that principle (the 25k+ ones ten years ago).

As far as I know "varies the frequency of the transmitted light and measures the freq and phase delay" is the standard way of measuring ToF in case of lasers. You modulate the laser diode by a signal of a wide range of frequencies and you subtract returned signal (after cleanup). The observation is done on a spectrum. Low frequencies give you wide range but low precision and high frequencies higher precision but lower range but you can use them enhance precision of the former.

Reply on news.ycombinator.com