Detecting laser in a small area

As the title says, i need to be able to detect where a laser is pointing in a small area. I know that it is possible using computer vision. But is there any other way?

How small is small? 1 dimension or 2? You have to give us those sorts of details if you want good answers. Try to be as descriptive as possible.

Light sensors.

Delta_G:
How small is small? 1 dimension or 2? You have to give us those sorts of details if you want good answers. Try to be as descriptive as possible.

Around a 3x3 cm square

What do you mean detect where a laser is pointing?
A simple yes/no, or do you need to know positions within that 3x3 cm?

{sigh} How big is the spot, and how accurately do you need to localise it? (And how often and how quickly?)

INTP:
What do you mean detect where a laser is pointing?
A simple yes/no, or do you need to know positions within that 3x3 cm?

I need to know its position within the region.

AWOL:
{sigh} How big is the spot, and how accurately do you need to localise it? (And how often and how quickly?)

The spot is around 0.5 cm. So if it can localise to 0.5 cm, it would be great but can do with up to 1cm. The detecting part is done just once per operation cycle. The speed is not an issue unless it is too long.
The details like spot size and accuracy is tentative right now, since first i need to know if there is a way to do it.

The detecting part is done just once per operation cycle. The speed is not an issue unless it is too long.

Get back to us when you're past the vague hand-waving phase of whatever it is you're suffering from.

Once you figure out what resolution you want, buy that many LDRs and arrange them in a grid. E.g., 9 LDRs with each spot being 1x1cm. Some diffusive material to fill out the hitbox.

A lesser known fact: a standard issue cheap Radio Shack LED can be used as a photodiode. According to a local university student who used this in a class project, it's good for 250 khz

An intense light on the face of an LED lowers the internal resistance. If you set up

+VDC
a 1 k resistor tied to
the anode of an LED
with a grounded cathode

the assembly acts like a PNP transistor; the light is the signal at the base, the junction of the LED and the resistor acts like the collector of the transistor

the best way to get the light to the face of the LED is to drill a hole through the housing of the LED and run a fiber optic cable flush against the LED.

this might work with an LED array with the plastic covers cut off the LED, and intense lasers. you would need to scan the array for the lowest voltage coming off an LED, and remember that the surface area of the LEDs is only a fraction of the space the array occupies

A lesser known fact: a standard issue cheap Radio Shack LED can be used as a photodiode

Or, you could use a photodiode.

[quote author=Geek Emeritus date=1504729183 link=msg=3403397]
An intense light on the face of an LED lowers the internal resistance.[/quote]
Nitpicking, but light on a photo diode generates a voltage. Light on a light dependent resistor changes the internal resistance.

AWOL:
Or, you could use a photodiode.

One can get an inexpensive single package LED matrix which might be an advantage in this particular application.

Google "quadrant photodiode" (images).
Leo..

AWOL:
Get back to us when you're past the vague hand-waving phase of whatever it is you're suffering from.

If you do not want to try to help, then you do not need to answer. At least, do not be rude. The other guy got what I was trying to say.

INTP:
Once you figure out what resolution you want, buy that many LDRs and arrange them in a grid. E.g., 9 LDRs with each spot being 1x1cm. Some diffusive material to fill out the hitbox.

I thought of something similar but was unsure for the spots uncovers. Your idea for using diffusive material should work out for me. I am going to try it. Thanks for the help.

If you don't want to waste other peoples' time (probably the ultimate rudeness, in my book), don't post pointless, subjective measures like "small area", "once per operation cycle" and "too long"