Display is dimming during use

Have a 3rd gen iPod Touch 32 gb that works great other than the screen brightness will dim to almost nothing during use. It does not seem to happen with any predictability, it occurs sometimes immediately after one swipes to "wake up the device" and other times it allows user to work with apps for a while and then the screen goes dim. The screen does not return back to brightness until it has sat for a while either charging and or not-charging. Device does not get "hot". Device functions well, even when screen is dimmed, you can open and use apps provided you can view them.

Anyone experience this condition?

I am contemplating replacing the display, but am unsure if this is the true source of the problem or not. Are there other parts that may be the problem?

Thank you in advance for any assistance that you may provide in resolving this matter.

-charley