Meditative visuals when tired. Lucid dreaming?

Recently when I have been tired I have noticed a fascinating phenomenon- I am not usually a visual person, that is, it is sometimes difficult for me to maintain mental images in my head. However, I have been meditating quite a lot recently, and when I have been tired, especially if I am not going to sleep but just resting my eyes, I have been paying attention to the shapes and colors playing behind my eyelids. The greater my focus, and greater my relaxation, (I am often meditating casually as I rest) the more real they appear, like the images that can guide you into dreams directly from waking, something I have frequently experienced since the time I was young. I have either been waking up to jot it down or falling asleep, but my goal is to be able to enter lucid dreams from this state, which I'm pretty sure is possible even though I have been as yet unable to control them.