Abstract: The annular reflector for a dark-field, vertically-illuminated microscope objective must have a peculiar curvature to obtain a uniform distribution of the light on the object surface being viewed. Four reflectors are disclosed. Each reflector is suitable for use in a respective microscope objective.

Abstract: An injector-type razor into which a blade may be mounted by means of a blade dispenser. The razor comprises the two-part assembly of a plastic molded main frame with handle and a spring-tensioned blade seat.

Abstract: A pair of identical bi-convex triplets, a mirror, and a pentaprism are used to extend the parallel light zone between the objective and the telescope lens of a conventional infinity corrected microscope system. Specific values for the components and spacings between the same are given.

Abstract: An input overload protection circuit particularly suited for use with a high impedance differential amplifier having two inputs is provided. The protection circuit prevents the flow of substantially all leakage currents for input signals within the linear operating range of the amplifier, and includes a first and second serial plurality of diode-action clamping means, such as diodes, connected respectively between the first and second input conductors to the amplifier input and a third conductor connected to a reference potential. Driven guard means operate to apply the voltage appearing on the respective first and second input conductors at their junction with the respective first and second clamping means to the respective first and second plurality of clamping means intermediate the respective ends thereof, thereby to substantially prevent leakage current from flowing through the clamping means from the pair of conductors.

Abstract: Glass lenses or lens blanks, containing all the ingredients necessary to produce phototropic or photochromic behavior, are treated in a conventional production furnace to produce a locally variable heat treatment, wherein at least one portion thereof is raised to a temperature exceeding the glass strain point but not the softening point, and other portions are heated to variable temperatures decreasing from the strain point. The treatment causes development of phototropic or photochromic behavior only in those portions of the lenses or lens blanks exposed to the temperature above the strain point.

Abstract: A stop for an instrument focusing shaft wherewith the extent of its rotational excursion in one direction may be readily adjusted and repeated. A gear fixed to the focusing shaft and in mesh with additional gearing is selectively stopped by another gear caused to mesh across two gears of the system. The stop gear may be carried out of mesh by reverse rotation of the focusing shaft.

Abstract: An improved method and apparatus for determining blood pressure in a system employing a variable pressure cuff and having means for sensing a quantity comprising the sum of applied cuff pressure and a component representative of pulsatile pressure in a blood vessel, a particular time derivative of at least the fluctuating component of the quantity is obtained and utilized for determining blood pressure. More specifically, the particular time derivative comprises the second (or greater) derivative and it is analyzed to determine at what applied pressure it first and last crosses a negative threshold value, those pressures then being indicated as diastolic and systolic pressure depending on whether applied pressure is increased or decreased. The threshold value may be dynamically determined.

Abstract: In cardiac signal processing apparatus, there is provided improved means for suppressing pacer signal artifacts, including both the discharge pulse and the recharge waveform (tail) of such artifact. Rate-limiting circuitry is used to substantially suppress the discharge pulse. However additional circuitry responsive to the detection of a pacer pulse is operative to obtain a measure of the electrical discharge of the discharge portion of the respective pacer pulse and to use such measure to generate a tail suppression signal which, when added to the original signal, substantially cancels the original pacer tail.A feed-back loop is opened by the rate-limiter when a pacer pulse occurs and in turn permits a large signal to be imposed on a threshold-level-type pacer pulse detector for connecting the large signal (pacer pulse) to a capacitor during the discharge portion of the pacer pulse.

Abstract: A safety razor contains a blade cartridge in which two blades are rigidly secured. The cartridge has a seat member with an integral blade edge guard disposed transversely along its forward margin. A first razor blade is disposed on a planar surface of the seat member and has its cutting edge located rearwardly of the guard. A second razor blade having a cutting edge located parallel to and rearwardly of the first blade edge is in contact with a mating surface of a cap member. The cap member is secured to the seat member thereby clamping the blades in desired position. The blades are maintained at a predetermined distance apart by spacing means and the guard member has a plurality of projecting teeth transversely arrayed across the guard member forming a comb guard.

Abstract: An improved fast-recovery circuit for ECG amplifiers and the like. The fast-recovery circuit includes threshold responsive circuitry connected in parallel with part of the resistance associated with the integrator in a feedback circuit of the amplifier. The threshold responsive circuitry operates to increase feedback frequency response of the integrator when the normally very low frequency output signal of the amplifier exceeds a certain threshold. The improved circuit prevents the threshold circuitry from responding to pulses or excursions in the output signal of a relatively higher frequency content and which exceed the amplitude threshold for less than a predetermined interval, as for instance caused by pacer spikes, large QRS complexes and the like. Preferably, the improved threshold responsive means comprises transistor means connected across the integrator's resistance and having capacitance means across the base-emitter circuit thereof for inhibiting response to certain short duration signals.

Abstract: In systolic pressure determining apparatus utilizing a pressure cuff and means for measuring a fluctuating quantity proportional to the sum of the cuff pressure and the fluctuating component proportioned to the pulsatile blood pressure, and including means for determining the maximum value of the fluctuating component as cuff pressure is varied, the improvement comprising means for converting the quantity into a representation of a time derivative of the fluctuating component means for obtaining the time integral of the time derivative over an interval of predetermined limits between initiation of systolic rise and systolic peak in each blood pressure pulse, and means extending the time integral, as a measure of pulse pressure amplitude, to the maximum value determining means. Specifically, certain crossings of a reference value by the time derivative are recognized as being the initiation of systolic rise and the systolic peak respectively, and the integration occurs over this interval.

Abstract: Improved method and apparatus for identifying and quantizing a substantially periodic, steeply rising wavefront of a signal in the possible presence of low amplitude interference. A time derivative of at least the steep wavefront is obtained. The derivative is then integrated over a predetermined interval in each of successive repetitions of the steep wavefront, the interval being that during which the derivative exceeds a reference level. A threshold value is established, preferably dynamically, to verify or validate that when the derivative exceeds the reference level it indeed represents the steeply rising wavefront. The integrated derivative is recognized as the quantized value of the steeply rising wavefront only if such verification occurs. The invention is suited to oscillometric determination of systolic pressure in a patient, where measurement of signal amplitude is preferably achieved by integrating the time derivative of the systolic rise wavefront.

Abstract: The specific disclosure provides a soft contact lens comprising an eye contacting inner surface, and an annular carrier portion including an outer surface spaced from the eye contacting inner surface not greater than a predetermined distance. An optical portion is encompassed by the carrier portion and includes an outer surface with all points thereon spaced from the inner surface a distance greater than the predetermined distance. An intermediate portion interconnects the carrier and optical portions and includes an outer surface extending downwardly and outwardly from the outer surface of the optical portion to the outer surface of the carrier portion.

Abstract: A DC isolation amplifier having improved conductive isolation between its input and output. The amplifier includes an input section having a modulator and an output section having a demodulator and an oscillator section. The modulator and demodulator are nonconductively coupled through inductive loops of two closed-loop cores of magnetic material each having windings inductively coupled to the material of their associated core and to the other of the modulator or the demodulator. Additionally, a unitary closed loop winding couples the two cores such that the net EMF induced in the turns of the winding accordingly such that the respective component of the external magnetic field of the turns is substantially normal to the respective plane of each turn of this plurality. Additionally, this unitary loop is twisted between the cores to comprise a twisted pair additionally to minimize the effects from external magnetic fields. In the preferred embodiment, this loop is limited to two turns per core.

Abstract: Apparatus for measuring the refractive powers of a lens and displaying the measured powers in so-called prescription form. A focimeter is equipped with means for generating electrical signals indicative of the net refractive powers of the lens, which signals are extended to novel electronic logic and control means for ultimately reading out and/or displaying the lens powers in a prescription form having "sphere" and "cylinder" components of power. Selectively activable control means determine whether the prescription is displayed in so-called "+ cylinder" notation or "- cylinder" notation. Additional means are provided for indicating which of two possible axis angles is correctly associated with the particular displayed component of cylinder power.

Abstract: In an EKG monitor capable of monitoring the stimulation pulse of a heart pacer, the inclusion of means for determining the polarity of the pacer pulse detected in the ECG signal and then for generating a standardized pacer pulse signal of the same polarity as detected. The apparatus further includes summing means for summing the ECG signal with the standardized pacer pulse to be included in the output of the monitor.

Abstract: A system for the cyclical time-compression of a continuous physiologic waveform provides scan-type display without loss of data during retrace by recording original data at one rate during a retrace-trace cycle, and read-out at a faster rate during the trace period for the compressed display. A feature of the system is use of a single random-access memory which has only the relatively small capacity for storing the data entered from the beginning of the retrace in a time compression cycle until readout at trace period in that cycle begins.

Abstract: A system for the cyclical time-compression of a signal waveform, particularly applicable to displays. Continuous input data is temporarily stored, as in a recirculating memory, during the trace and retrace phases (B & A) of a processing or display operation. The stored data is subsequently read out in time-compressed form during the trace phase (B) of the cycle. The average rate at which data is read out of storage is faster than the average rate at which it is entered, the ratio of average readout rate to average entry rate being the compression ratio of the system and corresponding herein with the ratio of a full display sweep cycle to the trace portion of that cycle such that the initial waveform, time-compressed, is displayed in its entirety. In an illustrated embodiment, the data is entered into a recirculating memory at a rate resulting in apparent precession of the data in memory.

Abstract: An improved atrial synchronous heart pacer includes means for generating an atrio-ventricular (A-V) interval control signal of automatically variable duration, which duration is a function of the sensed atrial heart rate (i.e. P-wave rate). A timing circuit establishes a basic timing interval for the generation of ventricular stimulation pulses, which interval may be modified by the control of the A-V interval signal. The A-V interval control signal preferably comprises the output of a P-wave triggered monostable multivibrator. The time constants of the multivibrator's timing circuits are scaled such that operation within the heart-rate range of 55-150 beats per minute prevents full recovery of the multivibrator following each sensed atrial beat and generation of an A-V output pulse, resulting in an A-V output pulse whose duration is a function of the time since the preceding trigger (i.e. rate).