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How laser rangefinder or laser distance meter work and what chip can measure Time of Flight ?

Started by a a August 12, 2022
On 12/08/2022 20:31, Ed Lee wrote:
> On Friday, August 12, 2022 at 9:06:42 AM UTC-7, TTman wrote: >> On 12/08/2022 14:46, Ed Lee wrote: >>> On Friday, August 12, 2022 at 3:23:57 AM UTC-7, a a wrote: >>>> On Friday, 12 August 2022 at 12:18:44 UTC+2, a a wrote: >>>>> what chip, clocked at what frequency, is used to measure Time of Flight of laser light at sucjh short time intervals ? >>> >>> GHz ASIC >>> 3E-9 second per meter >>> >>> >> FPGA...I worked on one... > > Too slow. I have only seen a few hundred MHz FPGA.
Enough to get time of flight... My test gear used Atmel running at 20MHz to get +/- 50nS resolution, checking the FPGA output and my test gear simulating the return pulse and seeing the answer in the test kit, provided by the FPGA. Test pulse was designed to simulate 10Km out and back. -- This email has been checked for viruses by Avast antivirus software. www.avast.com
On Saturday, August 13, 2022 at 7:24:12 AM UTC-4, TTman wrote:
> On 12/08/2022 17:48, Ricky wrote: > > On Friday, August 12, 2022 at 12:06:42 PM UTC-4, TTman wrote: > >> On 12/08/2022 14:46, Ed Lee wrote: > >>> On Friday, August 12, 2022 at 3:23:57 AM UTC-7, a a wrote: > >>>> On Friday, 12 August 2022 at 12:18:44 UTC+2, a a wrote: > >>>>> what chip, clocked at what frequency, is used to measure Time of Flight of laser light at sucjh short time intervals ? > >>> > >>> GHz ASIC > >>> 3E-9 second per meter > >>> > >>> > >> FPGA...I worked on one... > > > > I have one of the laser devices. It measures to a fraction of an inch. That would be an equivalent frequency of maybe 100 GHz which is a bit difficult, even inside an FPGA. Does this require multiple inputs with varying delays to define timing to a finer resolution than the clock period? > > > How much did you pay for it?
I don't recall exactly, but it was under $50 or I wouldn't have bought it. -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
a a <manta103g@gmail.com> wrote:
> On Friday, 12 August 2022 at 23:58:11 UTC+2, Ed Lee wrote: >> On Friday, August 12, 2022 at 2:31:31 PM UTC-7, a a wrote: >> > On Friday, 12 August 2022 at 22:37:28 UTC+2, Ed Lee wrote: >> > > On Friday, August 12, 2022 at 1:06:35 PM UTC-7, a a wrote: >> > > > On Friday, 12 August 2022 at 21:55:26 UTC+2, Ed Lee wrote: >> > > > > On Friday, August 12, 2022 at 11:45:18 AM UTC-7, a a wrote: >> > > > > > On Friday, 12 August 2022 at 15:46:11 UTC+2, Ed Lee wrote: >> > > > > > > On Friday, August 12, 2022 at 3:23:57 AM UTC-7, a a wrote: >> > > > > > > > On Friday, 12 August 2022 at 12:18:44 UTC+2, a a wrote: >> > > > > > > > > what chip, clocked at what frequency, is used to measure Time of Flight of laser light at such short time intervals ? >> > > > > > > GHz ASIC >> > > > > > > 3E-9 second per meter >> > > > > > c = 299 792 458 m/s > >>> c = 300 000 000 m/s >> > > > > > >> > > > > > 3E-9 s/m x 300 000 000 m/s = 0.9 >> > > > > > >> > > > > > ok >> > > > > > but for 1 cm resolution >> > > > > > we need 100 x faster clock >> > > > > > >> > > > > > and for parallel analysis of point cloud 100 x 100 >> > > > > > we need 100 x 100 faster clock >> > > > > > >> > > > > > could you explain ? >> > > > > There is no point in measuring all 10,000 points all at once. >> > > > so do you suggest, >> > > > what is marketed by iPhone and called Lidar in smartphone, >> > > > is a single point Laser Range Meter functionality ? >> > > > >> > > > If you are correct, so why do they present 2D laser scanner functionality on images ? >> > > > >> > > > Single point laser Lidar requires rotating head to work >> > > > >> > > > \so some kind od mechanics is involved >> > > Yes, precisely, to have better relative positioning with multi-sensors. However, there is no need to measure them all within E-9 second. >> > -E-9 second cloc k is for 1m resolution >> > for 1 cm resolution >> > you need >> > E-9 * 10-2 second clock >> > >> > but we still discuss a single-point operation >> With 5GHz (close to current fab cap) hardware counters, we can count pulses to the same point 100 times. If we get 25 pulses of 1 meter and 75 pulses of 1.1 meter, we can guess that the distance is close to 1.025 meters. >> >> Give me $100,000 and i can build you the chip to prove it. > -==c = 299 792 458 m/s > >>> c = 300 000 000 m/s > > -===3E-9 s/m x 300 000 000 m/s = 0.9 > > 300 000 000 m/s = 100 * 300 000 000 cm/s > > = 30 000 000 000 cm/s > > so you need 30 GHz clock x 2 to get 1 cm resolution for a single point > > ok, for 1 m distant object > 300 MHz x 2 clock can do the job > > but if you need mobile laser range meter to scan objects on the fly, to act as 2D scanner, > 1 cm counts and makes the difference
Love all this retarded math and units. Here's the short story. Light travels about 1 foot per nanosecond. If you're measuring reflections the distance traveled is twice between you and the target, so this in essense doubles your resolution. A 1GHz clock should be fine for measuring in increments of fractions of a foot.
Anthony William Sloman <bill.sloman@ieee.org> wrote:
> On Saturday, August 13, 2022 at 11:19:41 AM UTC+10, Ed Lee wrote: >> On Friday, August 12, 2022 at 6:12:58 PM UTC-7, bill....@ieee.org wrote: >> > On Saturday, August 13, 2022 at 11:00:46 AM UTC+10, Ed Lee wrote: >> > > On Friday, August 12, 2022 at 5:52:21 PM UTC-7, bill....@ieee.org wrote: >> > > > On Saturday, August 13, 2022 at 9:10:07 AM UTC+10, Ed Lee wrote: >> > > > > On Friday, August 12, 2022 at 3:40:38 PM UTC-7, a a wrote: >> > > > > > On Friday, 12 August 2022 at 23:58:11 UTC+2, Ed Lee wrote: >> > > > > > > On Friday, August 12, 2022 at 2:31:31 PM UTC-7, a a wrote: >> > > > > > > > On Friday, 12 August 2022 at 22:37:28 UTC+2, Ed Lee wrote: >> > > > > > > > > On Friday, August 12, 2022 at 1:06:35 PM UTC-7, a a wrote: >> > > > > > > > > > On Friday, 12 August 2022 at 21:55:26 UTC+2, Ed Lee wrote: >> > > > > > > > > > > On Friday, August 12, 2022 at 11:45:18 AM UTC-7, a a wrote: >> > > > > > > > > > > > On Friday, 12 August 2022 at 15:46:11 UTC+2, Ed Lee wrote: >> > > > > > > > > > > > > On Friday, August 12, 2022 at 3:23:57 AM UTC-7, a a wrote: >> > > > > > > > > > > > > > On Friday, 12 August 2022 at 12:18:44 UTC+2, a a wrote: >> > > > <snipped uninformed comment> >> > > Yes, we should. >> > > > >> > > > https://en.wikipedia.org/wiki/Tellurometer >> > > > >> > > > was the original wavelength-based range-finder, and it didn't send out a pulse and measure the time until it returned. >> > > > >> > > > Measuring the phase shift along the path to the reflector and back is a more practical scheme. >> > > >> > > This is talking about microwave. We are talking about lightwave (laser). >> > Both are electromagnetic waves and phase shift works for both. HP's laser interferomenter certainly measured to small fractions of the helium-neon laser wavelength (which I used to know to ten significant digits when we were designing one in). >> The difference is the much higher frequencies of lightwave vs. microwave. >> > The bottom of the Tellurometer page offers a link to a page on laser rangefinders. I haven't clicked on it in years. Maybe you should. >> >> Yes, you should listen to your own advice: >> >> "The most common form of laser rangefinder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the object and measuring the time taken by the pulse to be reflected off the target and returned to the sender." >> >> https://en.wikipedia.org/wiki/Laser_rangefinder > > It isn't all that accurate. The other techniques can do better, but they do tend to be more expensive, as more accurate instruments can afford to be. > > "Multiple frequency phase-shift - this measures the phase shift of multiple frequencies on reflection then solves some simultaneous equations to give a final measure. > > Interferometry - the most accurate and most useful technique for measuring changes in distance rather than absolute distances."
Is it 10 millionths of an in per "ring" on a optical flat with the blue/krypton light when measuring surface flatness? It's pretty amazing you can actually see such levels of interference. Autocollimators are pretty fascinating devices too.
Ed Lee <edward.ming.lee@gmail.com> wrote:
> On Friday, August 12, 2022 at 7:30:48 PM UTC-7, whit3rd wrote: >> On Friday, August 12, 2022 at 7:01:58 PM UTC-7, Ed Lee wrote: >> > On Friday, August 12, 2022 at 6:57:16 PM UTC-7, whit3rd wrote: >> > > On Friday, August 12, 2022 at 6:19:41 PM UTC-7, Ed Lee wrote: >> > > >> > > > "The most common form of laser rangefinder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the object and measuring the time taken by the pulse to be reflected off the target and returned to the sender." >> > > > >> > > > https://en.wikipedia.org/wiki/Laser_rangefinder >> > > Yeah, for rangefinding the corner-cube reflector left on Luna, that simple scheme's workable. For shorter >> > > distances, though, modulation of an FM burst, and detection of the interference of outgoing >> > > and incoming to generate the difference frequency, is the most practical way of doing it. >> > > >> > > I'm pretty sure my Hot Wheels radar gun isn't "measuring the time" with a digital clock, directly. >> > Yes, Bill and you are bring up all possible ways to measure distance. But OP specifically asked for digital processing of laser range-finder. >> Do you have an objection? A "laser range finder" is a broad class of instruments, with no particular >> 'digital processing' specificity, and digital processing is not, in the general case, superior >> or practical in the pulse/clock-and-count scenario, so we discuss others. > > I am just responding to OP direct question of: > "what chip, clocked at what frequency, is used to measure Time of Flight of laser light at sucjh short time intervals ?"
LM555
On Sat, 13 Aug 2022 16:26:51 -0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

>a a <manta103g@gmail.com> wrote: >> On Friday, 12 August 2022 at 23:58:11 UTC+2, Ed Lee wrote: >>> On Friday, August 12, 2022 at 2:31:31 PM UTC-7, a a wrote: >>> > On Friday, 12 August 2022 at 22:37:28 UTC+2, Ed Lee wrote: >>> > > On Friday, August 12, 2022 at 1:06:35 PM UTC-7, a a wrote: >>> > > > On Friday, 12 August 2022 at 21:55:26 UTC+2, Ed Lee wrote: >>> > > > > On Friday, August 12, 2022 at 11:45:18 AM UTC-7, a a wrote: >>> > > > > > On Friday, 12 August 2022 at 15:46:11 UTC+2, Ed Lee wrote: >>> > > > > > > On Friday, August 12, 2022 at 3:23:57 AM UTC-7, a a wrote: >>> > > > > > > > On Friday, 12 August 2022 at 12:18:44 UTC+2, a a wrote: >>> > > > > > > > > what chip, clocked at what frequency, is used to measure Time of Flight of laser light at such short time intervals ? >>> > > > > > > GHz ASIC >>> > > > > > > 3E-9 second per meter >>> > > > > > c = 299 792 458 m/s > >>> c = 300 000 000 m/s >>> > > > > > >>> > > > > > 3E-9 s/m x 300 000 000 m/s = 0.9 >>> > > > > > >>> > > > > > ok >>> > > > > > but for 1 cm resolution >>> > > > > > we need 100 x faster clock >>> > > > > > >>> > > > > > and for parallel analysis of point cloud 100 x 100 >>> > > > > > we need 100 x 100 faster clock >>> > > > > > >>> > > > > > could you explain ? >>> > > > > There is no point in measuring all 10,000 points all at once. >>> > > > so do you suggest, >>> > > > what is marketed by iPhone and called Lidar in smartphone, >>> > > > is a single point Laser Range Meter functionality ? >>> > > > >>> > > > If you are correct, so why do they present 2D laser scanner functionality on images ? >>> > > > >>> > > > Single point laser Lidar requires rotating head to work >>> > > > >>> > > > \so some kind od mechanics is involved >>> > > Yes, precisely, to have better relative positioning with multi-sensors. However, there is no need to measure them all within E-9 second. >>> > -E-9 second cloc k is for 1m resolution >>> > for 1 cm resolution >>> > you need >>> > E-9 * 10-2 second clock >>> > >>> > but we still discuss a single-point operation >>> With 5GHz (close to current fab cap) hardware counters, we can count pulses to the same point 100 times. If we get 25 pulses of 1 meter and 75 pulses of 1.1 meter, we can guess that the distance is close to 1.025 meters. >>> >>> Give me $100,000 and i can build you the chip to prove it. >> -==c = 299 792 458 m/s > >>> c = 300 000 000 m/s >> >> -===3E-9 s/m x 300 000 000 m/s = 0.9 >> >> 300 000 000 m/s = 100 * 300 000 000 cm/s >> >> = 30 000 000 000 cm/s >> >> so you need 30 GHz clock x 2 to get 1 cm resolution for a single point >> >> ok, for 1 m distant object >> 300 MHz x 2 clock can do the job >> >> but if you need mobile laser range meter to scan objects on the fly, to act as 2D scanner, >> 1 cm counts and makes the difference > >Love all this retarded math and units. > >Here's the short story. Light travels about 1 foot per nanosecond. If you're measuring reflections the >distance traveled is twice between you and the target, so this in essense doubles your resolution. A 1GHz >clock should be fine for measuring in increments of fractions of a foot. >
Fast clocks are power hogs. There are better ways to measure nanoseconds.
On Saturday, 13 August 2022 at 18:30:51 UTC+2, Cydrome Leader wrote:
> Anthony William Sloman <bill....@ieee.org> wrote: > > On Saturday, August 13, 2022 at 11:19:41 AM UTC+10, Ed Lee wrote: > >> On Friday, August 12, 2022 at 6:12:58 PM UTC-7, bill....@ieee.org wrote: > >> > On Saturday, August 13, 2022 at 11:00:46 AM UTC+10, Ed Lee wrote: > >> > > On Friday, August 12, 2022 at 5:52:21 PM UTC-7, bill....@ieee.org wrote: > >> > > > On Saturday, August 13, 2022 at 9:10:07 AM UTC+10, Ed Lee wrote: > >> > > > > On Friday, August 12, 2022 at 3:40:38 PM UTC-7, a a wrote: > >> > > > > > On Friday, 12 August 2022 at 23:58:11 UTC+2, Ed Lee wrote: > >> > > > > > > On Friday, August 12, 2022 at 2:31:31 PM UTC-7, a a wrote: > >> > > > > > > > On Friday, 12 August 2022 at 22:37:28 UTC+2, Ed Lee wrote: > >> > > > > > > > > On Friday, August 12, 2022 at 1:06:35 PM UTC-7, a a wrote: > >> > > > > > > > > > On Friday, 12 August 2022 at 21:55:26 UTC+2, Ed Lee wrote: > >> > > > > > > > > > > On Friday, August 12, 2022 at 11:45:18 AM UTC-7, a a wrote: > >> > > > > > > > > > > > On Friday, 12 August 2022 at 15:46:11 UTC+2, Ed Lee wrote: > >> > > > > > > > > > > > > On Friday, August 12, 2022 at 3:23:57 AM UTC-7, a a wrote: > >> > > > > > > > > > > > > > On Friday, 12 August 2022 at 12:18:44 UTC+2, a a wrote: > >> > > > <snipped uninformed comment> > >> > > Yes, we should. > >> > > > > >> > > > https://en.wikipedia.org/wiki/Tellurometer > >> > > > > >> > > > was the original wavelength-based range-finder, and it didn't send out a pulse and measure the time until it returned. > >> > > > > >> > > > Measuring the phase shift along the path to the reflector and back is a more practical scheme. > >> > > > >> > > This is talking about microwave. We are talking about lightwave (laser). > >> > Both are electromagnetic waves and phase shift works for both. HP's laser interferomenter certainly measured to small fractions of the helium-neon laser wavelength (which I used to know to ten significant digits when we were designing one in). > >> The difference is the much higher frequencies of lightwave vs. microwave. > >> > The bottom of the Tellurometer page offers a link to a page on laser rangefinders. I haven't clicked on it in years. Maybe you should. > >> > >> Yes, you should listen to your own advice: > >> > >> "The most common form of laser rangefinder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the object and measuring the time taken by the pulse to be reflected off the target and returned to the sender." > >> > >> https://en.wikipedia.org/wiki/Laser_rangefinder > > > > It isn't all that accurate. The other techniques can do better, but they do tend to be more expensive, as more accurate instruments can afford to be. > > > > "Multiple frequency phase-shift - this measures the phase shift of multiple frequencies on reflection then solves some simultaneous equations to give a final measure. > > > > Interferometry - the most accurate and most useful technique for measuring changes in distance rather than absolute distances." > Is it 10 millionths of an in per "ring" on a optical flat with the blue/krypton light when measuring > surface flatness? It's pretty amazing you can actually see such levels of interference. Autocollimators are > pretty fascinating devices too.
Very cheap unique wavelength light for using with Optical Flats... Using a 532nm. 50mw LED laser 22,458 views 27 Jan 2018 546 Dislike Share Clip Save Pierre's Garage 18.3K subscribers In this video, I&rsquo;ll be showing as a proof of concept how to make a real cheap, but, quite reliable light source using a 50 mw. LED pointer with a fixed wavelength in order to use with Optical Flats. A Xenon or any laboratory type fixed wavelength is quite out of reach for any hobbyist or small shop owner, this option of using a LED with a known wavelength isn&rsquo;t pretending to be as precise as a multi thousand of dollars instrument, but, will allow for reasonably accurate measurements in non-critical situations. The fixed wavelength allows the Optical Flats to create a pattern by reflection and diffraction on a polished surface, the goal is to measure the flatness of that surface, and, knowing the wavelength we&rsquo;re being able to quantify the amount of irregularity if there is any. Please take note that I'm using the term laser for the light emitting diodes, in fact a real laser is a very different technology, it's a bad habit to call a LED a laser diode... https://youtu.be/xSYl7q6yKPU
On Saturday, August 13, 2022 at 12:26:58 PM UTC-4, Cydrome Leader wrote:
> a a <mant...@gmail.com> wrote: > > On Friday, 12 August 2022 at 23:58:11 UTC+2, Ed Lee wrote: > >> On Friday, August 12, 2022 at 2:31:31 PM UTC-7, a a wrote: > >> > On Friday, 12 August 2022 at 22:37:28 UTC+2, Ed Lee wrote: > >> > > On Friday, August 12, 2022 at 1:06:35 PM UTC-7, a a wrote: > >> > > > On Friday, 12 August 2022 at 21:55:26 UTC+2, Ed Lee wrote: > >> > > > > On Friday, August 12, 2022 at 11:45:18 AM UTC-7, a a wrote: > >> > > > > > On Friday, 12 August 2022 at 15:46:11 UTC+2, Ed Lee wrote: > >> > > > > > > On Friday, August 12, 2022 at 3:23:57 AM UTC-7, a a wrote: > >> > > > > > > > On Friday, 12 August 2022 at 12:18:44 UTC+2, a a wrote: > >> > > > > > > > > what chip, clocked at what frequency, is used to measure Time of Flight of laser light at such short time intervals ? > >> > > > > > > GHz ASIC > >> > > > > > > 3E-9 second per meter > >> > > > > > c = 299 792 458 m/s > >>> c = 300 000 000 m/s > >> > > > > > > >> > > > > > 3E-9 s/m x 300 000 000 m/s = 0.9 > >> > > > > > > >> > > > > > ok > >> > > > > > but for 1 cm resolution > >> > > > > > we need 100 x faster clock > >> > > > > > > >> > > > > > and for parallel analysis of point cloud 100 x 100 > >> > > > > > we need 100 x 100 faster clock > >> > > > > > > >> > > > > > could you explain ? > >> > > > > There is no point in measuring all 10,000 points all at once. > >> > > > so do you suggest, > >> > > > what is marketed by iPhone and called Lidar in smartphone, > >> > > > is a single point Laser Range Meter functionality ? > >> > > > > >> > > > If you are correct, so why do they present 2D laser scanner functionality on images ? > >> > > > > >> > > > Single point laser Lidar requires rotating head to work > >> > > > > >> > > > \so some kind od mechanics is involved > >> > > Yes, precisely, to have better relative positioning with multi-sensors. However, there is no need to measure them all within E-9 second. > >> > -E-9 second cloc k is for 1m resolution > >> > for 1 cm resolution > >> > you need > >> > E-9 * 10-2 second clock > >> > > >> > but we still discuss a single-point operation > >> With 5GHz (close to current fab cap) hardware counters, we can count pulses to the same point 100 times. If we get 25 pulses of 1 meter and 75 pulses of 1.1 meter, we can guess that the distance is close to 1.025 meters. > >> > >> Give me $100,000 and i can build you the chip to prove it. > > -==c = 299 792 458 m/s > >>> c = 300 000 000 m/s > > > > -===3E-9 s/m x 300 000 000 m/s = 0.9 > > > > 300 000 000 m/s = 100 * 300 000 000 cm/s > > > > = 30 000 000 000 cm/s > > > > so you need 30 GHz clock x 2 to get 1 cm resolution for a single point > > > > ok, for 1 m distant object > > 300 MHz x 2 clock can do the job > > > > but if you need mobile laser range meter to scan objects on the fly, to act as 2D scanner, > > 1 cm counts and makes the difference > Love all this retarded math and units. > > Here's the short story. Light travels about 1 foot per nanosecond. If you're measuring reflections the > distance traveled is twice between you and the target, so this in essense doubles your resolution. A 1GHz > clock should be fine for measuring in increments of fractions of a foot.
How about fractions of an inch, like a tenth? -- Rick C. -+ Get 1,000 miles of free Supercharging -+ Tesla referral code - https://ts.la/richard11209
Ed Lee wrote:
> On Friday, August 12, 2022 at 3:40:38 PM UTC-7, a a wrote: >> On Friday, 12 August 2022 at 23:58:11 UTC+2, Ed Lee wrote: >>> On Friday, August 12, 2022 at 2:31:31 PM UTC-7, a a wrote: >>>> On Friday, 12 August 2022 at 22:37:28 UTC+2, Ed Lee wrote: >>>>> On Friday, August 12, 2022 at 1:06:35 PM UTC-7, a a wrote: >>>>>> On Friday, 12 August 2022 at 21:55:26 UTC+2, Ed Lee wrote: >>>>>>> On Friday, August 12, 2022 at 11:45:18 AM UTC-7, a a wrote: >>>>>>>> On Friday, 12 August 2022 at 15:46:11 UTC+2, Ed Lee wrote: >>>>>>>>> On Friday, August 12, 2022 at 3:23:57 AM UTC-7, a a wrote: >>>>>>>>>> On Friday, 12 August 2022 at 12:18:44 UTC+2, a a wrote: >>>>>>>>>>> what chip, clocked at what frequency, is used to measure Time of Flight of laser light at such short time intervals ? >>>>>>>>> GHz ASIC >>>>>>>>> 3E-9 second per meter >>>>>>>> c = 299 792 458 m/s > >>> c = 300 000 000 m/s >>>>>>>> >>>>>>>> 3E-9 s/m x 300 000 000 m/s = 0.9 >>>>>>>> >>>>>>>> ok >>>>>>>> but for 1 cm resolution >>>>>>>> we need 100 x faster clock >>>>>>>> >>>>>>>> and for parallel analysis of point cloud 100 x 100 >>>>>>>> we need 100 x 100 faster clock >>>>>>>> >>>>>>>> could you explain ? >>>>>>> There is no point in measuring all 10,000 points all at once. >>>>>> so do you suggest, >>>>>> what is marketed by iPhone and called Lidar in smartphone, >>>>>> is a single point Laser Range Meter functionality ? >>>>>> >>>>>> If you are correct, so why do they present 2D laser scanner functionality on images ? >>>>>> >>>>>> Single point laser Lidar requires rotating head to work >>>>>> >>>>>> \so some kind od mechanics is involved >>>>> Yes, precisely, to have better relative positioning with multi-sensors. However, there is no need to measure them all within E-9 second. >>>> -E-9 second cloc k is for 1m resolution >>>> for 1 cm resolution >>>> you need >>>> E-9 * 10-2 second clock >>>> >>>> but we still discuss a single-point operation >>> With 5GHz (close to current fab cap) hardware counters, we can count pulses to the same point 100 times. If we get 25 pulses of 1 meter and 75 pulses of 1.1 meter, we can guess that the distance is close to 1.025 meters. >>> >>> Give me $100,000 and i can build you the chip to prove it. >> -==c = 299 792 458 m/s > >>> c = 300 000 000 m/s >> >> -===3E-9 s/m x 300 000 000 m/s = 0.9 >> >> 300 000 000 m/s = 100 * 300 000 000 cm/s >> >> = 30 000 000 000 cm/s >> >> so you need 30 GHz clock x 2 to get 1 cm resolution for a single point > > 3GHz (reasonable clock) for 10cm resolution. > >> ok, for 1 m distant object >> 300 MHz x 2 clock can do the job >> >> but if you need mobile laser range meter to scan objects on the fly, to act as 2D scanner, >> 1 cm counts and makes the difference > > https://en.wikipedia.org/wiki/Oversampling > for higher resolution. >
The usual method is a time-to-amplitude converter. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Ricky <gnuarm.deletethisbit@gmail.com> wrote:
> On Saturday, August 13, 2022 at 12:26:58 PM UTC-4, Cydrome Leader wrote: >> a a <mant...@gmail.com> wrote: >> > On Friday, 12 August 2022 at 23:58:11 UTC+2, Ed Lee wrote: >> >> On Friday, August 12, 2022 at 2:31:31 PM UTC-7, a a wrote: >> >> > On Friday, 12 August 2022 at 22:37:28 UTC+2, Ed Lee wrote: >> >> > > On Friday, August 12, 2022 at 1:06:35 PM UTC-7, a a wrote: >> >> > > > On Friday, 12 August 2022 at 21:55:26 UTC+2, Ed Lee wrote: >> >> > > > > On Friday, August 12, 2022 at 11:45:18 AM UTC-7, a a wrote: >> >> > > > > > On Friday, 12 August 2022 at 15:46:11 UTC+2, Ed Lee wrote: >> >> > > > > > > On Friday, August 12, 2022 at 3:23:57 AM UTC-7, a a wrote: >> >> > > > > > > > On Friday, 12 August 2022 at 12:18:44 UTC+2, a a wrote: >> >> > > > > > > > > what chip, clocked at what frequency, is used to measure Time of Flight of laser light at such short time intervals ? >> >> > > > > > > GHz ASIC >> >> > > > > > > 3E-9 second per meter >> >> > > > > > c = 299 792 458 m/s > >>> c = 300 000 000 m/s >> >> > > > > > >> >> > > > > > 3E-9 s/m x 300 000 000 m/s = 0.9 >> >> > > > > > >> >> > > > > > ok >> >> > > > > > but for 1 cm resolution >> >> > > > > > we need 100 x faster clock >> >> > > > > > >> >> > > > > > and for parallel analysis of point cloud 100 x 100 >> >> > > > > > we need 100 x 100 faster clock >> >> > > > > > >> >> > > > > > could you explain ? >> >> > > > > There is no point in measuring all 10,000 points all at once. >> >> > > > so do you suggest, >> >> > > > what is marketed by iPhone and called Lidar in smartphone, >> >> > > > is a single point Laser Range Meter functionality ? >> >> > > > >> >> > > > If you are correct, so why do they present 2D laser scanner functionality on images ? >> >> > > > >> >> > > > Single point laser Lidar requires rotating head to work >> >> > > > >> >> > > > \so some kind od mechanics is involved >> >> > > Yes, precisely, to have better relative positioning with multi-sensors. However, there is no need to measure them all within E-9 second. >> >> > -E-9 second cloc k is for 1m resolution >> >> > for 1 cm resolution >> >> > you need >> >> > E-9 * 10-2 second clock >> >> > >> >> > but we still discuss a single-point operation >> >> With 5GHz (close to current fab cap) hardware counters, we can count pulses to the same point 100 times. If we get 25 pulses of 1 meter and 75 pulses of 1.1 meter, we can guess that the distance is close to 1.025 meters. >> >> >> >> Give me $100,000 and i can build you the chip to prove it. >> > -==c = 299 792 458 m/s > >>> c = 300 000 000 m/s >> > >> > -===3E-9 s/m x 300 000 000 m/s = 0.9 >> > >> > 300 000 000 m/s = 100 * 300 000 000 cm/s >> > >> > = 30 000 000 000 cm/s >> > >> > so you need 30 GHz clock x 2 to get 1 cm resolution for a single point >> > >> > ok, for 1 m distant object >> > 300 MHz x 2 clock can do the job >> > >> > but if you need mobile laser range meter to scan objects on the fly, to act as 2D scanner, >> > 1 cm counts and makes the difference >> Love all this retarded math and units. >> >> Here's the short story. Light travels about 1 foot per nanosecond. If you're measuring reflections the >> distance traveled is twice between you and the target, so this in essense doubles your resolution. A 1GHz >> clock should be fine for measuring in increments of fractions of a foot. > > How about fractions of an inch, like a tenth?
You better ask the trillion of centimeters per second folks to do the math for you in that.