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

[whit3rd]

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.

 

[Ed Lee]

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.

 

[Anthony William Sloman]

On Saturday, August 13, 2022 at 12:01:58 PM UTC+10, 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.

But the OP is a a, and he\'s time-wasting half-wit. Nobody sane is going to spend time on responding to him. You are the sucker who did.

--
Bill Sloman, Sydney

 

[Ed Lee]

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 ?\"

 

[Ed Lee]

On Friday, August 12, 2022 at 7:37:13 PM UTC-7, bill....@ieee.org wrote:

On Saturday, August 13, 2022 at 12:01:58 PM UTC+10, 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.
But the OP is a a, and he\'s time-wasting half-wit. Nobody sane is going to spend time on responding to him. You are the sucker who did.

It\'s a rare on-topic case related to electronics and worth answering.

 

[whit3rd]

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.

 

[Mike Monett]

whit3rd <whit3rd@gmail.com> 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.

I believe most short distance laser rangefinders use a simple capacitive
charging circuit with the outoing pulse as the start and the reflection as
the terminator. The capacitor voltage measures the distance. An example is
a CDN$35 unit from Amazon Canada:

https://www.amazon.ca/Distance-Handheld-Portable-Precision-
Apartment/dp/B08Y96T271/

Other methods perform interferometric distance measurements. It is the most
precise and fastest distance measurement method, but interferometric
rangefinders are expensive and susceptible to damage. This makes them
unreliable in the field.




--
MRM

 

[Anthony William Sloman]

On Saturday, August 13, 2022 at 12:39:13 PM UTC+10, Ed Lee wrote:

On Friday, August 12, 2022 at 7:37:13 PM UTC-7, bill....@ieee.org wrote:
On Saturday, August 13, 2022 at 12:01:58 PM UTC+10, 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.
But the OP is a a, and he\'s time-wasting half-wit. Nobody sane is going to spend time on responding to him. You are the sucker who did.
It\'s a rare on-topic case related to electronics and worth answering.

Not when a a asks the question.

--
Bill Sloman, Sydney

 

[Ricky]

On Friday, August 12, 2022 at 2:49:04 PM UTC-4, a a wrote:

On Friday, 12 August 2022 at 18:48:21 UTC+2, 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?

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209
thank you Ricky
since iPhone claims Lidar in smartphone and parallel distance array calculation on-the-fly

For 1cm resolution 10 GHz single point
turns into 100 x 100 x 10 GHz clock frequency
for 100 points x 100 points array

What 100 x 100 point array???

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[TTman]

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?

--
This email has been checked for viruses by Avast antivirus software.
www.avast.com

 

[TTman]

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

 

[Ricky]

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

 

[Cydrome Leader]

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.

 

[Cydrome Leader]

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.

 

[Cydrome Leader]

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

 

[John Larkin]

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.

 

[a a]

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
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Pierre\'s Garage
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In this video, I’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’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’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

 

[Ricky]

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

 

[Phil Hobbs]

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

 

[Cydrome Leader]

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.