Projector and control method for projector

A projector for displaying an image on a screen comprising:

• a light source;
• a light modulation device having a light modulation area for modulating light that exits the light source to effective image light representing an image;
• an image pickup unit which picks up an image of an area including the screen and the image light and generates a picked-up image;
• a first outer peripheral line calculating unit which calculates each side of an outer peripheral line of the image light, based on the picked-up image;
• a second outer peripheral line calculating unit which calculates each side of an outer peripheral line of the screen, based on the picked-up image;
• an imaginary screen outer peripheral line calculating unit which, when the second outer peripheral line calculating unit detects three of four sides of the outer peripheral line of the screen in the picked-up image, calculates a first imaginary screen outer peripheral line by supplementing one side that is undetected with one side of the outer peripheral line of the image light calculated by the first outer peripheral line calculating unit;
• an imaginary screen aspect ratio calculating unit which calculates an imaginary screen aspect ratio that is an aspect ratio of an area defined by the first imaginary screen outer peripheral line;
• an imaginary aspect ratio determining unit which determines whether the imaginary screen aspect ratio is more vertically oriented than a first ratio or not;
• an imaginary screen outer peripheral line re-calculating unit which, when a result of determination by the imaginary aspect ratio determining unit is more vertically oriented than the first ratio, changes the imaginary screen aspect ratio to a second ratio that is different from the first ratio, calculates the one undetected side according to the second ratio, corrects the first imaginary screen outer peripheral line, and calculates a second imaginary screen outer peripheral line;
• and
• a correction image light modulation area calculating unit which calculates a correction image light modulation area that is an area in a part of the light modulation area so as to fit inside the second imaginary screen outer peripheral line.