Variable focal length lens device and variable focal length lens control method

A variable focal length lens device comprising:

• a variable focal length lens configured to periodically vary a focal length;
• an image detector configured to execute an image detection of a measurement target through the variable focal length lens;
• a lens controller configured to control the image detector to execute the image detection on a basis of image detection conditions regarding the focal length of the variable focal length lens;
• and
• an image-detection-condition setting unit configured to set the image detection conditions in the lens controller, wherein
• the image-detection-condition setting unit is configured to set, as the image detection conditions, a combined mode of repeating an image detection loop comprising at least one multi-plane-image-detecting operation and at least one single-plane-image-detecting operation,
• in the multi-plane-image-detecting operation, the image-detection-condition setting unit is configured to set a plurality of values of the focal length, at each of which the image detection is performed, in one cycle in which the focal length of the variable focal length lens is varied, and
• in the single-plane-image-detecting operation, the image-detection-condition setting unit is configured to set a single value of the focal length, at which the image detection is performed, in one cycle in which the focal length of the variable focal length lens is varied.