An image sensor includes a first photodiode and a second photodiode. The image sensor further includes a first color filter over the first photodiode; and a second color filter over the second photodiode. The image sensor further includes a first microlens over the first color filter and a second microlens over the second color filter. The image sensor further includes a first electro-optical (EO) film between the first color filter and the first microlens, wherein a material of the first EO film is configured to change refractive index in response to application of an electrical field. The image sensor further includes a second EO film between the second color filter and the second microlens, wherein a material of the second EO film is configured to change refractive index in response to application of an electrical field.