Schott Ag

Carl-zeiss-smt Ag

Schott Glas

Hellma Materials Gmbh & Co. Kg

Christian Kusch

Lutz Parthier

Gunther Wehrhan

Joerg Staeblein

Wolfgang Singer

Frank-Thomas Lentes

Michael Gerhard

Ewald Moersen

The method produces low-stress, large-volume crystals with low birefringence and uniform index of refraction. The method includes growing the crystal with larger than desired dimensions including diameter and height from a melt; cooling and tempering the crystal with the larger than desired dimensions and after the cooling and tempering removing edge regions of the crystal with the larger than desired dimensions so that a diameter reduction and a height reduction of at least five percent occurs respectively and so that the crystal has the desired dimensions of diameter and height. No further tempering takes place after removing of the edge regions.

Method for making low-stress large-volume crystals with reduced stress birefringence and more uniform refractive index and crystals made thereby

A method is described for making an especially not-(111)-oriented low-stress large-volume crystal having a glide plane with reduced stress birefringence and more uniform refractive index. The method includes growing and tempering the crystal while heating and/or cooling to form a temperature gradient in order to relax stresses arising along the glide plane. During the tempering the heating and/or cooling occurs by heat transfer in a heat transfer direction and the heat transfer direction or temperature gradient is oriented at an angle of from 5&#xb0; to 90&#xb0; to the glide plane. Crystals with a uniform refractive index with variations of less than 0.025&#xd7;10(RMS value) are produced by the method.

Method for making low-stress large-volume not-(111)-oriented crystals with reduced stress birefringence and more uniform refractive index and crystals made thereby

The method for evaluating schlieren in glassy or crystalline optical materials includes irradiating a test sample of the optical material with light and producing a shadow image of the test sample on a projection screen. The shadow image of the test sample is received in an electronic image receiving device, such as a digital camera, and is compared with another shadow image of schlieren obtained with a comparison sample by means of interferometry. Then the optical material of the test sample is evaluated with the help of the comparison results.

Method and apparatus for analysis of schlieren

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Jena, Germany

Christian Kusch