Optical Monitors

Vorelco built Dyn-Optics Model 590

The Dyn-Optics Model 590 is without question the most widely used optical monitor in the world. It is a rather basic no frills optical monitor that provides years and years of trouble free operation. Although this technology was developed in the 80's it has seen very few design improvements and Vorelco began producing the Lumiscan line of monitors that are considered the best in class. We still repair many old Dyn-Optics monitors but we no longer recommend them as there are much lower noise higher gain solutions in electro-optic product development. We still carry an inventory of parts to build them for our die hard clients however.

Dyn-Optics MODEL 590-AS has the same monitoring characteristics as the 590, however, the unit has the capability of automatically setting the starting point for each layer, thereby reducing the operator's work load and increasing the yield on long repetitive coating runs.

OPTICAL MONITOR OPERATION

The optical monitor operates on the principal of optical interference between the deposited film and the substrate. Specifically, as the film is being deposited onto a witness glass, there is a reflectance at the vacuum-film interface and the film-substrate interface.

There is a well-known relationship between the interference induced maxima and minima of reflectance and the index of refraction and the optical thickness. The optical thickness and index of refraction of the various layers of a coating design is generated by a computer and the routing operator duplicates this design in the vacuum chamber. By tracking the maxima and minima of reflectance, the operator can control the optical thickness deposited accurately and thereby fabricate a coating that duplicates the design.

CHARACTERISTICS OF OPTICAL MONITOR COMPARED WITH CRYSTAL MONITOR

The optical monitor is more accurate than a crystal monitor in the fabrication of coatings since it determines the actual optical thickness of the layers as they are being coated while the crystal monitor measures the change in frequency of a quartz crystal as it is coated. The change in frequency is related to the mass of the film which in turn is correlated to the optical thickness. The optical thickness is dependent upon all the characteristics of the vacuum chamber during coating such as degree of vacuum, temperature of substrate, rate of coating, type of substrate, history of coating material, rate of oxidation, cleanliness of the chamber, etc. Thus, the optical monitor measures the true optical thickness regardless of the chamber conditions while the crystal monitor measures the frequency change of the quartz crystal which is indirectly related to the optical thickness and often does not provide accurate information of optical thickness. As a consequence, the coating often does not duplicate the design.

Accessories for 580-D Optical Monitor

FILTER HOLDERS

The optical monitor is supplied with either a four position filter cassette or a 2x2 inch filter holder. The filters in the four position cassette are permanently mounted and the wavelength is selected by rotating the cassette to the desired value and inserting into the optical path. The optical monitor can also be modified to operate with a monochrometer in the receiver.

PERISCOPE, WINDOW AND GIMBLE ASSEMBLY

The periscope, window and gimble assembly enables the radiation from the optical monitor to be directed through the vacuum collar to the chip changer and finally back out the collar to the receiver.

ROTARY FEEDTHROUGH

The chip changer is activated, to drop a monitoring chip, by a rotation motion through the vacuum chamber. The rotary feedthrough provides a convenient means of transferring rotary motion through the base plate of the vacuum chamber.

CHIP CHANGER

The chip changer is utilized to hold glass monitoring chips that are used to measure the thickness of each coating layer.

Vorelco rebuilt DYN-OPTICS Model 580D