Beamforming with directional sensors Having photo-diodes with a very narrow field of view (+-10 degrees for half power) what should I consider when designing a beam-forming algorithm?

I know that I could use many photo-diodes mounted in an arc to cover 180 degrees for example but the uncertainty of 10 degrees is too big. As an alternative to classical beam-forming, what would be the methods to use to isolate a signal coming from one direction with a high precision (under 1 degree)?

My goal is to analyze the flickering of lamps, knowing their position from analyzing camera data, I want to isolate the signal coming from their direction.
Given the horizontal and vertical component of the distance vector from the source to the sensor array be X and Y, then the angle between the sensor array and the source is given by:
$$ \theta = \tan^{-1} (Y/X) $$ 

If the linear distance between each sensor is $d$, each sensor should experience a delay:
$$ \delta t = d \sin(\theta)/c $$

Now if you can measure the delays (high precision measurement will lead to higher accuracy), and have the knowledge of $d$, you can find the angle $\theta$. 

Warning: Practical errors and considerations are not taken into account in this approach.