Endoscope system

1. An endoscope system comprising:

an illumination portion that comprises an emitter and that is configured to radiate illumination light beam onto an imaging subject, the illumination light beam having intensity distribution in which light portions and dark portions are spatially repeated in a beam cross section perpendicular to an optical axis;

a controller configured to cause widths of the dark portions in the intensity distribution of the illumination light beam to change;

an imager configured to acquire a plurality of illumination images of the imaging subject being illuminated with illumination light beams in which the widths of the dark portions are different from each other; and

at least one processor comprising hardware, the processor being configured to:

create first separation images and second separation images from each of the plurality of illumination images, the first separation images containing a greater quantity of information about a deep layer of the imaging subject than the second separation images do; and

calculate information about depths of a feature portion in the imaging subject on the basis of the plurality of the first separation images and the plurality of the second separation images created from the plurality of illumination images,

wherein the processor is configured to:

create the first and second separation images on the basis of at least two types of intensity values among the intensity values of pixels that are in the illumination images and that respectively correspond to, in the intensity distribution, the light portions, the dark portions, and portions having intensity values that are between those of the light portions and those of the dark portions; and

calculate the information about the depths of the feature portion on the basis of changes among the plurality of first separation images and changes among the plurality of second separation images.

2. The endoscope system according to claim 1 , wherein the illumination portion is configured to emit the illumination light beam in a form of divergent beam so that pattern of the light portions and the dark portions on the imaging subject expands in a proportional matter with respect to an image-capturing distance between the imager and the imaging subject.

3. The endoscope system according to claim 1 , further comprising:

a meter configured to measure an image-capturing distance between the imager and the imaging subject,

wherein the controller is configured to change periods of the light portions and the dark portions in the intensity distribution on the basis of the image-capturing distance so that the intensity distribution of the illumination light beam on the imaging subject becomes constant independently of a distance between the imager and the imaging subject.

4. The endoscope system according to claim 1 , wherein the illumination light beam consists of a plurality of light beams having wavelengths that are different from each other, and the plurality of light beams have the intensity distribution in which periods of the light portions and the dark portions decrease with an increase in the wavelengths.

5. The endoscope system according to claim 1 , wherein the intensity distribution of the illumination light beam has a stripe-like pattern in which the band-like light portions and dark portions are repeated in an alternating manner in a width direction.

6. The endoscope system according to claim 5 , wherein an intensity profile of the light portions and the dark portions of the intensity distribution of the illumination light beam in the width direction has a substantially sine-wave shape.

7. The endoscope system according to claim 1 , further comprising:

a first polarizer configured to control polarization states of the illumination light beam; and

a second polarizer configured to select a polarization state of light coming into the imager from the imaging subject.

8. The endoscope system according to claim 1 , wherein the processor is configured to calculate the information about the depths of the feature portion on the basis of a correspondence table in which the widths of the dark portions and separation depths between the first separation images and the second separation images are associated with each other.

9. The endoscope system according to claim 8 , wherein the processor is configured to:

respectively calculate contrasts of multiple sets of the first and second separation images; and

calculate the information about the depths of the feature portion on the basis of the contrasts and the correspondence table.