Image capturing system and image capturing method

An image capturing system, comprising:

• an image capturer to acquire a background image by performing image capturing of a background surface;
• and
• processing circuitry to execute a process of detecting condition of fluid as a detection target existing between the image capturer and the background surface, wherein
• the image capturer includes a first optical adjustment unit to make adjustment of at least one of a focal position and a depth of field of the image capturer, and
• the processing circuitry
• divides an image capturing visual field of the image capturer into a plurality of image capturing regions based on distance information indicating a distance to the background surface,
• acquires a plurality of image capturing region images as the background images of the plurality of image capturing regions by having the first optical adjustment unit make the adjustment and having the image capturer perform the image capturing of the background surface in regard to all or part of the plurality of image capturing regions, and
• executes the process of detecting the condition of the fluid based on the plurality of image capturing region images.