Infrared wide-angle single lens for use in an infrared optical system

A single lens system comprising a single infrared wide-angle meniscus lens having positive power and a first surface made concave facing toward an object plane and a second surface made convex, said single infrared wide-angle lens satisfying the following conditional expressions (1), (2), (3) and (4);

• (1) -50.0 th<r.sub.1 <-3.5 th
• (2) -5 th<r.sub.2 <-1.1 th
• (3) 2<n<4.5
• (4) 0.5 f<bf<1.5 f
• where th is the lens thickness, r.sub.1 is the radius of curvature of the first surface, r.sub.2 is the radius of curvature of the second surface, n is the refractive index of a vitric material of the lens at a wavelength of 10 .mu.m, bf is the backfocus and f is the focal length of the lens.

A single lens system comprising a single infrared wide-angle meniscus lens having positive power and a first surface made concave facing toward an object plane and a second surface made convex, said single infrared wide-angle lens satisfying the following conditional expressions (1), (2), (3) and (4);

• (1) -50.0 th<r.sub.1 <-3.5 th
• (2) -5 th<r.sub.2 <-1.1 th
• (3) 2<n<4.5
• (4) 0.5 f<th<2f
• where th is the lens thickness, r.sub.1 is the radius of curvature of the first surface, r.sub.2 is the radius of curvature of the second surface, n is the refractive index of a vitric material of the lens at a wavelength of 10 .mu.m, th is the lens thickness and f is the focal length.

A non-contact temperature measuring device comprising:

• a measuring device body;
• an infrared detector mounted to said measuring device body;
• and
• a single infrared wide-angle lens mounted to said measuring device body, said single infrared wide-angle lens comprising a single infrared wide-angle meniscus lens having positive power and a first surface made concave facing toward an object plane and a second surface made convex, said single infrared wide-angle lens satisfying the following conditional expressions (1) , (2), (3) and (4);
• (1) -50.0 th<r.sub.1 <-3.5 th
• (2) -5 th<r.sub.2 <-1.1 th
• (3) 2<n<4.5
• (4) 0.1 f<d<0.8 f
• where th is the lens thickness, r.sub.1 is the radius of curvature of the first surface, r.sub.2 is the radius of curvature of the second surface, n is the refractive index of a vitric material of the lens at a wavelength of 10 .mu.m, an aperture stop is disposed between the object plane and the first surface, d is the distance between the aperture stop and the first surface, and f is the focal length of the lens.

A non-contact temperature measuring device comprising:

• a measuring device body;
• an infrared detector mounted to said measuring device body;
• and
• a single infrared wide-angle lens mounted to said measuring device body, said single infrared wide-angle lens comprising a single infrared wide-angle meniscus lens having positive power and a first surface made concave facing toward an object plane and a second surface made convex, said single infrared wide-angle lens satisfying the following conditional expressions (1) , (2) , (3) and (4);
• (1) -50.0 th<r.sub.1 <-3.5 th
• (2) -5 th<r.sub.2 <-1.1 th
• (3) 2<n<4.5
• (4) 0.5 f<bf<1.5 f
• where th is the lens thickness, r.sub.1 is the radius of curvature of the first surface, r.sub.2 is the radius of curvature of the second surface, n is the refractive index of a vitric material of the lens at a wavelength of 10 .mu.m, bf is the backfocus and f is the focal length of the lens.

A non-contact temperature measuring device comprising:

• a measuring device body;
• an infrared detector mounted to said measuring device body;
• and
• a single infrared wide-angle lens mounted to said measuring device body, said single infrared wide-angle lens comprising a single infrared wide-angle meniscus lens having positive power and a first surface made concave facing toward an object plane and a second surface made convex, said single infrared wide-angle lens satisfying the following conditional expressions (1), (2), (3) and (4);
• (1) -50.0 th<r.sub.1 <-3.5 th
• (2) -5 th<r.sub.2 <-1.1 th
• (3) 2<n<4.5
• (4) 0.5 f<th<2f
• where th is the lens thickness, r.sub.1 is the radius of curvature of the first surface, r.sub.2 is the radius of curvature of the second surface, n is the refractive index of a vitric material of the lens at a wavelength of 10 .mu.m, th is the lens thickness and f is the focal length.

An air-conditioner which comprises:

• a non-contact temperature measuring device;
• data forming means for forming temperature data of individual ranges based on a signal fed from said non-contact temperature measuring device;
• control signal forming means for forming an air conditioning control signal based on the data obtained from said data forming means;
• air-conditioning control means for controlling the air-conditioning based on the air-conditioning control signal obtained from said control signal forming means;
• and
• wherein said non-contact temperature measuring device comprises:
• a measuring device body;
• an infrared detector mounted to said measuring device body;
• and
• a single infrared wide-angle lens mounted to said measuring device body, said single infrared wide-angle lens comprising a single infrared wide-angle meniscus lens having positive power and a first surface made concave facing toward an object plane and a second surface made convex, said single infrared wide-angle lens satisfying the following conditional expressions (1), (2), and (3);
• (1) -50.0 th<r.sub.1 <-3.5 th
• -5th<r.sub.2 <-1.1 th
• (3) 2<n<4.5
• where th is the lens thickness, r.sub.1 is the radius of curvature of the first surface, r.sub.2 is the radius of curvature of the second surface, and n is the refractive index of a vitric material of the lens at a wavelength of 10 .mu.m.