Abstract: An optical filter is configured to have a regular transmittance of 60% of higher for light having a wavelength of 950 nm. The optical filter is also configured such that in a state in which a light resistance test of irradiating the optical filter for 300 hours with light from a xenon arc lamp having a wavelength not shorter than 300 nm and not longer than 400 nm and a wattage of 120 W/m2 is performed, the optical filter exhibits a change in C* having an absolute value of 6 or smaller between before and after the light resistance test, the C* being measured by the SCE method by use of a spectrophotometer.

Abstract: An optical filter is configured to have a regular transmittance of 60% or higher for light having a wavelength of 950 nm. The optical filter is also configured to be contracted by being heated at a temperature of 85° C. or higher, or a size change of the optical filter occurs from room temperature to 300° C. as monotonous increase in a tensile mode of a thermomechanical analyzer (TMA).

Abstract: Disclosed is an optical filter with L* measured by the SCE method being 20 or greater, wherein: the linear transmittance with respect to light with wavelengths being at least a portion of a wavelength range from 760 nm to 2000 nm is 60% or greater; and, before and after a light resistance test wherein light of a xenon arc lamp (average integrated illuminance of light with wavelengths from 300 nm to 400 nm:120 W/m2) is shone for 300 hours, the absolute value of a change in C* measured by the SCE method using a spectroscopic colorimeter is 6 or less.

Abstract: An optical filter has a back-scattering property. The linear transmittance thereof to light of at least some avelengths in the wavelength range of 760-2000 nm is 60% or higher. The azimuth is 20° from an incidence plane when the polar angle of the direction of incidence of incident light is 0°. The value of a bidirectional reflectance distribution function in the direction ‘here the polar angle is ?60’ is BRDF (0°; 20°, ?60°). The azimuth is 20° from an incidence plane when the polar angle of the direction of incidence of incident light is 30°. The value of a bidirectional reflectance distribution function in the direction where the polar angle is ?60° is BRDF (30°; 20°, ?60°). The azimuth is 20° from an incidence plane when the polar angle of the direction of incidence of incident light is 60°.

Abstract: This optical filter 10 has an L* of at least 20 as measured by the SCE method, wherein the linear transmittance is at least 60% with respect to light the wavelength of which falls at least partially within the wavelength range of 760 nm-2,000 nm, and the temperature, at which the optical filter contracts by being heated, is at least 85° C.

Abstract: A current resonance type switching power supply circuit in which a power factor and a voltage regulation in the power supply are improved includes switching elements for interrupting either a voltage or a current output from a DC power supply and supplying the output to primary windings of an insulating transformer and a non-insulating transformer. The switching power supply circuit receives a predetermined alternating voltage from the insulating transformer, and is driven by a DC power supply including a rectifying means for rectifying an AC power supply, a decoupling capacitor arranged at an output side of the rectifying means so as to eliminate noise, a secondary winding of the non-insulating transformer, and a smoothing capacitor charged by a charging circuit including a diode and a choke coil.