Abstract:
A light chopper for chopping the monochromatic light beam of a spectrophotometer system, has a rotatable shaft driven by a synchronous motor at a frequency proportional to the power line frequency. An aperture bearing disc rotates with the shaft in relation to a photocell/detector array for generating digital timing signals for use by a microcomputer to control the tasks of the spectrophotometer system in synchronism with line frequency. The microcomputer monitors line frequency for responsively programming a programmable divider for generating an index signal for proportionally sequencing the wavelength of the monochromatic beam through a predetermined spectral range.The rotatable shaft is coupled to the synchronous motor via a mechanical pin drive and a set of attracting magnets which are spaced in face confronting relation at the point of coupling for providing compliance and damping between the coupled shaft and synchronous motor, thus minimizing phase jitter of the timing system and permitting rejection of time frequency stray circuit pickup.
Abstract:
A dual beam spectrophotometer includes a radiation chopper, a monochrometer, and a diffraction grating moved by a stepper motor. The chopper includes a gate pulse generator which produces gate pulses G.sub.S and G.sub.R corresponding to periods during which radiation from the source passes through a sample cell and a reference cell respectively. A stepper motor drive circuit produces pulses to step the stepper motor which are synchronized with the chopping cycle by means of the G.sub.R and G.sub.S pulses. The stepper motor is arranged to step an equal number of times in each half of a chopping cycle. A further condition which is preferably satisfied is that the first pulse of a sequence should start in the opposite half of the chopping cycle from that in which the first pulse started in a previous chopping cycle. At low stepping rates the motor will step twice in one chopping cycle and then pause for several cycles before again stepping twice.
Abstract:
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.
Abstract:
An analytical apparatus is described having a non-dispersive, multiwavelength photometric analyzer which is adapted to provide simultaneous display of chromatography peaks at a plurality of different analytical wavelengths. In a particular arrangement, the apparatus includes a chromatograph for separating a sample to be examined into components.
Abstract:
A spectrophotometer comprising means for producing electrical signals Er and Es corresponding to reference and measuring beams, respectively; means for multiplying the value Es by a factor k to produce an electrical signal corresponding to the value kEs; means for controlling said signal producing means so as to keep the value (Er + kEs) constant; and means for producing an electrical signal corresponding to the value (Er - kEs), whereby minute changes of the absorbance of a sample can be accurately measured without logarithmic conversion.
Abstract:
A sample chamber for an optical spectrometer comprising means for selecting one of two modes of operation: a transmission mode or a reflection mode. The mode-selecting means comprise optical elements for switching the path of the optical beam passing through the sample chamber so that the beam either passes through a sample or is incident upon and reflects off of a surface of a sample. Coupled to the path-selecting means are means for moving a sample to the position and orientation relative to the optical beam which is appropriate to the mode of operation selected.
Abstract:
A pair of beam splitters for an optical instrument wherein one beam splitter is used to divide source radiation into a sample and reference beam while the second beam splitter recombines the sample and reference beams prior to their entering a monochromator. In order to reduce schlieren effects, each beam splitter is provided with stripes of alternating reflective and transmitting portions. The edges of the stripes of each beam splitter lie wholly within the optical aperture while the ends of the stripes extend outwardly of the optical aperture. The beam splitters are oriented in such a manner that the stripes are orthogonal.
Abstract:
An illuminator system for use in a spectrophotometer by which the mode of operation can be easily changed in a simple manner. To this end, means for shielding either of the beams emerged from respective monochromatic beam generators and means for shielding, when said first mentioned means is in the inoperative condition, the other of said beams that has passed through the sector diaphragm. By operating the above mentioned two means, the double wavelength, single beam spectrophotometer can be used as a single wavelength dual beam spectrophotometer and vice versa.