Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1989-02-14
1990-08-14
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
2502014, 250216, G01N 2186, G01J 120, H01J 314
Patent
active
049489844
DESCRIPTION:
BRIEF SUMMARY
Optical scanning heads according to this invention are intended for incorporation in CD-players and serve for reading the optical information stored on the CD (compact disc). Due to the fact that the measuring light source is not located on the objective axis, on the contrary on an axis at right angles thereto and the measuring light is focussed by way of a deflecting mirror from the measuring light source by way of the objective on the surface to be scanned, one obtains a particularly low overall height of the scanning head, which makes it possible to produce CD-players with such a low overall height that they correspond to the standard dimensions of car radios.
This type of construction of the scanning head has the further advantage, which is not relevant for use in motor vehicle CD-players, that the path of rays between the measuring light source and objective is accessible for manipulations, since the deflecting mirror is inserted in an opening in the housing of the scanning head.
It was already proposed (DE-OS 35 36 700), to use such scanning heads of CD-players also for the high resolution measurement of the profiling and of the surface roughness of work-piece surfaces. In this case it would occasionally be advantageous if one could also visually inspect the surface section just measured.
It was then recognised that by slightly varying the deflection mirror on an optical scanning head, such as is used in motor vehicle CD-players at very low costs one could provide the additional possibility of direct observation of the point of the work-piece surface just measured.
For this purpose, it is proposed according to the invention to use a deflection mirror, which is indeed impermeable to the measured light, but is permeable for at least one wavelength in the visible region of the spectrum and has optical quality not solely on the reflecting front side, but also on its rear side. One can then position an observation device directly behind this deflecting mirror. Since the deflecting mirror is frequently originally a dielectric mirror, thus comprises a basic member (generally of glass) permeable to visible light, in many cases it is sufficient to remove the easily accessible deflecting mirror, already located on the scanning head intended for CD-players, to additionally polish it to optical quality on its rear side and then to re-install it. The observation optical system may be a commercially available microscope-eye-piece.
The modification according to the invention of the optical scanning head thus allows a visual observation of the respectively measured point of the work-piece surface, with very low additional costs. The additionally provided optical parts do not need to be manufactured specially, they do not require a great deal of space and do not considerably increase the weight of the scanning head.
Since the objectives used in CD-scanning heads have a very short focal length (in practice 4.5 mm) and also have a small diameter (in practice 6-8 mm), these objectives correspond very closely to microscope objectives. Thus, together with a commercially available microscope-eye-piece, according to the invention one obtains a microscope integrated in the scanning head.
With the development another embodiment of the invention a visual inspection of the measuring point is then possible even if the ambient light is very poor and the scanning head casts shadows. The observation device containing the scanning head and illumination device forms a compact, smooth-surfaced unit. Furthermore, the observation light falls exactly onto the measuring point, so that the illumination device requires only low power.
The development of the invention according to another embodiment is an advantage with regard to a solely low overall height even of the modified scanning head.
The development of the invention according to another embodiment ensures that one can carry out the visual observation of a point of the work-piece surface and the measurement of this point simultaneously, without the measurement result being adulterate
REFERENCES:
patent: 4433235 (1984-02-01), Akiyama et al.
patent: 4563058 (1986-01-01), Yardy
patent: 4595829 (1986-06-01), Neumann et al.
patent: 4611115 (1986-09-01), Rich
patent: 4680745 (1987-07-01), Ota et al.
patent: 4734570 (1988-03-01), Horikawa et al.
Focus MeBtechnik GmbH & Co KG
Messinger Michael
Nelms David C.
Philpitt Fred
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