Need help assembling a circuit

Hey everyone,
We are drawing up a new circuit for our robot based upon 5x SD5443 Photodiodes for infra-red detection. They are going to be placed in a setup
like the following:
| | | | |
Where each " | " is an SD5443 module. The idea behind the circuit is that an average of the 2 sensors on the left and right are taken and compared to each other (left is compared to right). Then we will be given a value that is either telling us that left is higher, right is higher or they are basically reading the same strength (that is neither can see it or both can). That is the reason for the middle sensor, to tell if there is nothing there or if there is something there. However, we do not wish to calibrate the middle sensor based on ambient light readings so it will also have to be related to the average of the other 2 sensor clusters in some manner.
Does anyone have any ideas on how to do this?
It is likely that when we compare the values of left and right despite the background light that is coming in they will be basically equal due to the averaging so long as there is a lack of IR source other than ambience.
The values that we are reading from all 5 sensors are likely to all be very similar for most of the time until an IR source is introduced and then we should be able to accurately tell where the IR is coming from. We intend to overly filter out IR interference with some IR Film from a camera store or something like that, unless anyone else here has a better suggestion on how to remove external interference based on ambient light.
We would also like to amplify the signal using another opamp to make it easier to determine where the ball is at different stages. Is this a good idea?
Can anyone help us out with a basic circuit to get this working? We are drawing some ideas up ourselves but I am not sure if they will work or not.
TIA
Jeff
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Firstly, I'd encourage you to try your ideas out - you will learn far more by doing so than asking. Try and devise simple tests to validate your basic assumptions, before you worry about designing complete systems. So in this case, take a single photosensor and see just what you can detect with it. Will it work ? Well, if you do a bit of homework on photosensors you will discover that most schemes use pulsed sources, rather than just measuring a phototransistor output. Understanding why will tell you a lot about the strengths and weaknesses of your idea.
Dave
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