I am trying to reconstruct this interesting piece of the puzzle that a long time ago, my father brought me. It has cards from A to B, mentioning a word using the same. For example J for Joker. Nothing is visible using naked eyes. But when you place a plastic semi-transparent/translucent sheet on the card the actual figure becomes clearly visible. Unfortunately, I lost the plastic sheet. Following are the two cards:
If you zoom in on these pictures, some patterns are slightly visible. For example, start from the left corner you would see some part of the joker.
Has anybody come across this or something similar to this kind of puzzle? Can you give some idea how probably this could be made especially the plastic sheet that reveals the hidden images?
Note: Please note that the cards are black & white and not colored.
The closest match is "red-reveal". But the principle looks different.
This question falls under
This is called a hidden picture puzzle. All such puzzles have an associated special trick of printing. In this particular card, one has to first guess what is the hidden object by close observation (just like in the link). Then it is verified with the help of the plastic sheet. These particular cards though have a slightly different aim: to teach the children about English alphabets. Whether it is a puzzle or a teaching aid, it is for sure that the underlying technology is the same.
While the answer by SpiritFryer is useful as a digital tool to decipher the hidden information in the puzzle, I am still looking for physical version of this tool which will give me a tactile experience just like the original kit having the plastic sheet for deciphering.
Update: Kindly update your answers so that I could award the bounty to the most eligible answer.