Method of detecting a defocus of an image sensor and image sensor

A method of detecting a defocus of an image sensor, comprising:

• providing an image sensor comprising a plurality of pixels, a pixel comprising a first subpixel and a second subpixel, wherein the first subpixel comprises m photodiode units providing first readout values and a first microlens structure overlaying the photodiode units, the second subpixel comprises m photodiode units providing second readout values and a second microlens structure overlaying the photodiode units, and the first microlens structure is structurally different from the second microlens structure, wherein m is a positive integer;
• interpolating the first readout values of the photodiode units of the first subpixel to positions of n of the photodiode units of the second subpixel to obtain interpolated values, wherein n is a positive integer;
• and
• obtaining an imbalance value by using the interpolated values and the second readout values provided by the n of the photodiode units of the second subpixel.