A monochromator has three ports or slits including two entrance slits and an exit slit. A single mirror and a diffraction grating define a first, folded path between an entrance slit on one side of the housing and an exit slit on the opposite side of the housing. The mirror is movable in and out of a second path between the second entrance slit and the grating so that a second path may be completed from the second entrance slit to the grating and thence to the exit slit. Alternatively two of the ports may be used as exit slits and one as an entrance slit.
A spectroanalytical gas measuring apparatus has a radiation source (36), a transmitting condensor (19), an objective (13) and a beam divider (11) which deflects at least a part of the radiation reflected back to the apparatus by a reflector (40) to a polychromator or spectrometer (32). The transmitted radiation falls after the beam divider (11) onto a deflecting mirror (12) which is adjustable between two positions and which directs the light to an objective reflector (13). The objective reflector (13) reflects the radiation to a follow-up mirror (15) arranged opposite to the beam passage opening (14). At least one long and one short focal length objective reflector (13) are provided in order to ensure different ranges of distance in conjunction with the adjustable deflecting mirror (12).
In a color measuring instrument, an integrating sphere is used to illuminate the sample and fiber optics are used to carry light diffusely reflected from the sample and from an interior wall of the sphere to a spectrometer. The transmitting ends of the fiber optic bundles are fixed in the housing of the spectrometer as entrance slits for the spectrometer, which includes a fixed grating and one or two arrays of photodetectors to detect the spectra dispersed by the grating from light received from the two transmitting ends.
For mounting the optical components of optical apparatus in an adjusted manner, the optical components are either adjusted and permanently fixed in or on shaped component bodies having accurately defined dimensions, or are produced on such bodies at an accurate location and with accurate alignment. Then, the shaped component bodies are assembled in a defined manner, so that the optical components assume the precisely correct location relative to one another.
An oxygen sensor contains an indicator whose change in absorption is a function of the concentration of oxygen in a sample bathing the indicator. Light transmitted and reflected through the indicator of the sensor undergoes an absorption that is characteristic of the concentration of oxygen. The indicator is a viologen whose absorption returns to a steady-state value after it has been subjected to a pulse of short-wavelength light. The rate at which the absorption returns to the steady-state value is a function of the concentration of oxygen bathing the viologen indicator. A measurement system for use with the pO.sub.2 sensor causes a short-wavelength flash to be sent to the sensor and thereafter monitors the time-varying absorption of the sensor to measure the oxygen content of the sample bathing the viologen indicator.
