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

Started by August 12, 2022
```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.
```
```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.
```
```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.
```
```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
```
```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 ?"
```
```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 <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
```
```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
```
```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
```
```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?

--
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```