Method of Bonding Two Parts Together

The invention will now be described in greater detail, by way of example, with reference to a drawing, in which

FIGS. 1a and b demonstrate the method with reference to a side-sectional elevations of an assembly of two parts of an optical filter and the optical filter formed from this assembly.

FIG. 2 is a cross-sectional view of a lens having an electro-optical layer which can be influenced.

FIG. 3 is a cross-sectional view of a polarizing beam splitter.

FIG. 1a is a cross-sectional view through the components of an optical filter. Dichroic layers consisting of mirrors 3 and 4 are vapour deposited on glass parts 1 and 2 and have a coefficient of reflection which is 99% or larger for a given wavelength range. The glass part 1 consists of a central part 5 and a coaxial part 6 which is separated from part 5 by a coaxial slot 7 so as to prevent deformation of the mirror 3. A stack of dichroic layers 8 which is as thick as the stack on part 5 is vapour deposited on part 6 as well as on part 5. A ring 9 of vapour deposited glass having a thickness of, for example, 0.5 .mu.m is provided on the mirror 4 on part 2 for accurately adjusting the spacing between the mirrors 3 and 4. The ring 9 and the layers 8 are then activated for 1 minute by slightly polishing them with cerium oxide (CeO.sub.2) and are then placed against each other (FIG. 1b) as a result of which the bond is obtained by wringing in contact. The reduction of the thickness of the layer as a result of the slight polishing treatment with cerium oxide is negligibly small. Said slight polishing treatment, however, is very effective for the wringability. As a matter of fact polishing serves for the (chemical) activation of the surfaces.

FIG. 2 is a sectional view through a lens. Said lens comprises two lens halves 20 and 21 of glass. A 0.5 .mu.m thick indium-tin oxide layer 22 is provided on lens half 20 and on said layer a 2 .mu.m thick BaTiO.sub.3 layer 23 is provided on which again a 0.5 .mu.m thick indium-tin oxide layer 24 is provided. The latter layer is slightly polished with cerium oxide and the similarly slightly polished surface 25 of lens part 21 is then bonded to layer 24 by wringing in contact. By applying a suitable potential difference between the layers 22 and 24, layer 23 may be made to be polarizing. So far lenses and lens parts have been bonded together by means of glue (for example, lens bond type M62, a type indication of Summers Labs. Inc. Optical Division, Fort Washington, Pa. 190 34, USA). Bonding by means of wringing in contact is more lasting and the penetration of dirt into the bond is much less than in a glued joint.

FIG. 3 is a sectional view of a polarizing beam splitter which is used in glass-fibre communication systems and in so-called laser vision systems in which an optical information carrier is read by means of a laser beam. Said beam splitter consists of a first glass prism 30 and a second glass prism 31. The glass of the prism has a refractive index of 1.52 (n=1.52). Provided on prism 30 is a layer stack 32 consisting of 19 layers which is composed of alternately MgO (n=1.7) and MgF.sub.2 (n=1.4) layers each having an optical thickness of .tau./4. This system may also be represented as follows:

glass (HL) .sup.9 H glass

wherein

H are the MgO layers and

L are the MgF.sub.2 layers.

After slightly polishing the last H layer (MgO) and the surface 33 of the second prism, the second prism is bonded to the last H layer by wringing in contact.

It will be obvious that the method may also be used to bond together parts which consist of a material other than glass, for example, aluminum oxide, semiconductor materials, etc.