Measurement support device, endoscope system, processor for endoscope system, and measurement support method for measuring object size

A measurement support method using a measurement support device including a head including a collimator that emits measurement auxiliary light emitted from a light source as a collimated beam, an imaging unit that acquires an image of a subject, on which a spot is formed with the measurement auxiliary light, via an imaging optical system and an imaging element, and a memory that stores information indicating a relationship between each of a plurality of predetermined positions of the spot on the imaging element and a corresponding actual size of the subject, wherein the relationship is determined in advance without use of a distance measured to the subject, and wherein the method comprises:

• emitting the measurement auxiliary light such that an optical axis of the auxiliary light has an inclination angle that is not 0 degrees with respect to an optical axis of the imaging optical system in a case where an optical axis of the measurement auxiliary light emitted from the head is projected on a plane including the optical axis of the imaging optical system;
• acquiring an image of the subject, on which the spot is formed with the measurement auxiliary light, via the imaging unit;
• measuring the position of the spot on the imaging element on the basis of the image of the subject;
• using the information indicating the relationship from the memory and the measured position of the spot on the imaging element to determine the actual size of the subject corresponding to the measured position of the spot, and creating a marker indicating the corresponding actual size of the subject by obtaining a number of pixels corresponding to the marker on the imaging element;
• and
• making a display device display the image of the subject on which the spot is formed and the marker, and the marker be displayed in the vicinity of the spot in the image of the subject.