I need to know the spectral response curve of a compact digital camera which has a CCD image sensor. However, I don't have the facilities for the same at the moment and I need to address this issue quickly. So I was wondering whether how variable these curves are for the compact cameras which are easily available in the market and cost around 75-100$ ? Will it be fine to use the response curve for some other camera?
There isn't any such thing unless you have a camera which outputs RAW images. For all cameras the internal preprocessing (which generates the JPGs) applies responsivity corrections before you ever see the data. I doubt you'll find a camera in that cost range which has RAW output.
Now, as a Systems Engineer and Analyst, I always ask: What is the problem you are trying to solve? THere may be a completely different approach which will work better for you. There's also another important design rule: Good; Fast; Cheap: pick any two. Which is to say, you simply cannot achieve success under your proposed approach (since you basically required Fast and Cheap).
Just take your own measurements
You don't really need complete response curves, just single data points for the leds you use.
Compare photos of your leds set to multiple power levels.
Shoot in manual mode, in case your camera does some tricks and effects to "improve" the result.
If using JPEG, apply reverse gamma function to obtain linear intensity values.
Defocusing your led image will allow you to apply high brighness (more signal and less noise) and sample (average out) many image pixels without overexposing.