Patent ID: 6093911
Filing Date: 2000-07-25
Classification: H01L

Abstract:
In a vacuum heating furnace comprising a translucent container for retaining therein a heated object and a heating light source for heating said heated object retained in said translucent container, said vacuum heating furnace characterized in that said translucent container has on its surface formed a tapered portion to receive transmitted light totally reflected on the inner surface of said translucent container at an angle smaller than a critical angle, wherein said translucent container includes a reinforcing rib made of the same material as that of said translucent container, said reinforcing rib being protruded to the outside of said translucent container and said tapered portion is formed at a protruded end of said reinforcing rib, and wherein when .alpha. assumes an angle formed relative to one side surface of said rib by said tapered portion and .theta. assumes a critical angle of said translucent container, said tapered portion and said rib are constructed so as to satisfy the following equations:-.theta.c-2.theta.c<.alpha.2.theta.c90.degree.-.theta.c<.alpha.<45.degree.+.theta.c.