How to find out if my specific idea is really new, or if someone has already worked on it? I started working on my PhD few months ago and I am trying to solve a problem in a particular topic. The topic is quite specific and many people have already worked on it before. I am stuck at the following two scenarios: 


I would like to extend the topic in some particular direction which I think is interesting and new. How will I know if people have already worked on that 'new extended topic'? I google hoping to find something, but I don't. I read some review papers (but most of them are old) and they don't cover any. Also, I think it is very difficult to read all recent papers related to the topic of research in a hope to land on my specific topic.
I would like to solve an existing specific topic in a new way, which may be quite simple, but looks efficient. But, I have the feeling that people should have already solved the problem in 'my new way'. How will I find if that has been done? I use google again and land up in quite interesting papers but it still do not solve my problem.


How do you tackle the above situations? I think one way is to do a very extensive literature review of the topic, but how will you achieve that? Review papers? Reading 'all' papers in that topic? I tried to do that right at the beginning, but I realized I can not and should not know everything, but should have a very rough overview of the topic and in depth knowledge in my way of solving the problem. 

Edit: My research is in the topic of Computer Vision, in the field of Computer Science. My very specific topic is the topic of marker-less augmented reality.
What I find most critical: figure out the nomenclature. Look for articles about your research question in your own words and create a list of keywords that are frequently used. There is usually no consensus, so you will end up with synonyms. 

Once you know the words used by the community in your field to describe the concepts and problems, literature searches get a lot easier. My usual approach is to use a large database of publications (in my field Medline is good, I guess your field has its equivalent) and look for the few keywords I listed. Now, don't read all articles of course, do a selection based on the title first, then on the abstract. There is a lot of redundancy in published papers so you will be able to weed out a majority of the papers at this point.

In some fields, senior researchers sometimes write review articles that list the 'open problems' in the field. Even if they don't give such a list, good review papers give an overview of the state of the art and are a great source of secondary citations.

Of course, discuss the matter with your colleagues and adviser, read prominent blogs and if possible go to (a) good conference(s). Conferences are great to grasp what others do and don't, and they help to make sure you don't reinvent the wheel. 

Finally, I think you shouldn't worry too much at this point, here are a few words form my answer to this question Is there any research on the prevalence of academic theft?


  The chances that your idea is absolutely original is close to zero. Concepts, ideas and theories are almost always due to an
  intellectual environment in which many researchers are present. Even
  theories traditionally attributed to a single individual [...] were the result of
  inputs from several individuals over several years.
  
  The chances that your state of research, access to resources and previous intellectual work is similar for someone else is very small.
  Research breakthrough are a result of the right coincidence of
  opportunity, resources and intellectual maturity.