Figure 7.

Comparison of in plane and out of plane photobleaching. Out of plane photo bleaching is measured on a stack of 41 images separated by 1 micron. First bars of the two groups indicate intensity decrease after 40 consecutively measured frames at a fixed depth location (in plane) and second bar illustrates intensity decrease for the hypothetical case of maximum out of plane bleaching when the bleaching rate of the neighboring planes would be the same as the one in the currently imaged planed which in this example is equivalent to 40×41 exposures of a single plane. Third and fourth bars indicate intensities at the bottom and top of stacks after 40 consecutive stack measurements. Contrary to TPE, OPE has out of focal plane photobleaching and bleaching at the top of the stack is increased.