It will be difficult, if not impossible, for you to get much time for yourself in the first few months if it is just you and the baby.
Especially in the first month or so, you'll be struggling to find time just to sleep. Your entire routine will be overthrown, and it will be hard enough just finding time enough to do basic necessities while balancing the baby (e.g. simple tasks like bathing, feeding yourself, sleep, getting dressed, etc. will frequently have to be crammed into moments when the baby is sleeping).
There are a couple of strategies that you can use to maximize what little time you'll have during these weeks:
Establish a schedule - Disclaimer: your baby will have his/her own schedule, which will largely dictate your schedule. Additional disclaimer: your baby will regularly change their schedule, and by extension, yours. Flexibility is essential. Still, once you have an idea of your current routine (i.e. how often the baby naps, and for how long; when the baby feeds), you can start identifying pockets of time that become opportunities for you to use for your own needs. These breaks start off short, but frequent. Over time, they will become longer, but less frequent.
Plan ahead - In addition to planning how to use the gaps in the schedule, you should start early. In fact, start before the baby is even born. Identify tasks that your spouse or family members can and and willing to do, and arrange to have them take over as many as possible (e.g. someone does laundry for you on weekends or in the evening; someone else cleans up the dishes in the evening/morning; etc.). If you have enough freezer space available, a great strategy is to pre-make 1-2 months worth of frozen meals, and then freeze them until needed during your leave. We had friends and family come over about 3 months before our son was born to fill our chest freezer with 2 months worth of meals for both my wife and I.
Get help!!! - This is the single best strategy for finding time for yourself, if it is an option (it won't be for everyone). Frequently, friends or family will say things like "let us know if there's anything we can do to help." Don't be too proud to take them up on this offer! Even someone coming over for an hour or two to keep an eye on the baby while you're in the other room getting a nap/reading a book/watching a movie/debugging code will be a help that you will appreciate. Other possible forms of assistance friends and family can provide include running errands for you, delivering meals, helping with basic chores around the house, or even just delivering your mail (this may be more important than you may expect, particularly if the circumstances of your delivery prevent you from walking up/down stairs for a few weeks).
Edits in response to clarification of the question:
Sleep is NOT a way of relaxation for me. The things which would actually relax me are software development, photography, and meditation at home. I usually do not sleep at day time.
Sleep is a prerequisite of relaxation. Sleep will quickly become a scarce commodity for you, and it will likely be difficult, if not impossible, to maintain your previous habits (such as not sleeping during day time).
At first, your baby will not sleep for more than a couple of hours at a time, and will need to be fed, changed, and cuddled in between their naps. This doesn't stop at night time; you will be up at least 2-3 times each night for several weeks. If you only sleep at night, and only sleep when the baby sleeps, you will quickly become too tired to do anything approaching relaxation during the few breaks you have during the day.
Software development, as you know, requires an alertness of mind that sleep deprivation will make extremely difficult.
Mediation, on the other hand, may be a more practical alternative. I find that meditation can be very restful. However, I also find that meditating while very tired usually is a good way to fall asleep :) Keep in mind though that you may very well be holding your little one while they sleep. This may be difficult to do while achieving deeper relaxation states during meditation (I can't even sleep while holding my son, let alone meditate to any extent beyond basic breathing exercises).
Photography will be an option, though. You'll have many, many opportunities for pictures of your baby :) If you find photography relaxing, you'll have more good shots than you can count! Just make sure you have plenty of storage space on your camera (or film, if you prefer). I would suggest placing multiple cameras in strategic places throughout the house, if at all possible, to take advantage of those chance opportunities. It is exceptionally difficult to get newborns to pose the way you want them to (at least while they're awake!), but if you are ready, you'll be able to catch some wonderful candids.