The Chronoscope was invented by Frank Friedman Oppenheimer 1912-1995.
The principle of the Chronoscope is based on the theory that every light particle or foton is unique, that it has a, what you might call, timestamp and that it will exist eternally.
In other words light particles are identifiable because each particle has a unique key, and that unique key relates to a certain point in time.
By grouping, sorting and filtering on a certain time period it is possible to view that certain time period.
Frank Oppenheimer devised the so called "Oppenheimer
Time Equation" which allowed him to put the theory into
practice by creating the Chronoscope.
In contradiction to what some people might think, the
Chronoscope is not a time machine, it is a time viewer.
Of course it is only possible to look into the past, although
some experiments gave indications that looking into the
future is also possible.
Frank Oppenheimer was working on a revision of his
"Oppenheimer Time Equation" to include that "future"
His death in 1995 has halted research into that direction.
A Journey into Other Dimensions