Anti-reflection film and microscope having optical element with the same anti-reflection film applied thereto

An image-pickup unit that achieves removable mount on a microscope, comprising:

• an image-pickup device having an image-pickup element that picks up an image by the microscope;
• and
• a dust protection glass arranged in front of the image-pickup device,
• wherein the dust protection glass is provided with an anti-reflection film having a layered structure having first to seventh layers of films, in order from a surface of the dust protection glass, formed of a middle-refractive-index material for the first layer, a high-refractive-index material for each of the second, fourth, and sixth layers, a low-refractive-index material or a middle-refractive-index material for each of the third and fifth layers, and a low-refractive-index material for the seventh layer, with a range of an optical film-thickness nd of each layer in reference to a design wavelength λ being “(1.04˜1.13)×λ/4” for the first layer, “(0.30˜1.46)×λ/4” for the second layer, “(0.13˜0.46)×λ/4” for the third layer, “(0.56˜1.26)×λ/4” for the fourth layer, “(0.22˜0.56)×λ/4” for the fifth layer, “(0.31˜0.41)×λ/4” for the sixth layer, and “(1.05˜1.13)×λ/4” for the seventh layer.