| 简介 |
PROBLEM TO BE SOLVED : To provide a far-infrared lens which uses only a small number of lenses made of expensive optical glass materials, such as rare metals, and thus minimizes light intensity loss caused by lens transmission and lens surface reflection inherent to an increase in the number of lenses and lens surfaces, and to provide a far-infrared image capturing device.SOLUTION : A far-infrared lens includes at least one negative lens located on the object side from an optical aperture stop, at least one positive lens located on the image side from the optical aperture stop, and a diffractive optical element provided on a most image-side surface of the far-infrared lens, and satisfies a conditional expression (1) 0.400≤|fn|/fp≤6.500, where fn represents a focal length of the negative lens at a wavelength of 10 μm and fp represents a focal length of the positive lens at a wavelength of 10 μm.SELECTED DRAWING : Figure 2 |
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