Showing papers on "Depth of focus published in 1982"

Improving resolution in photolithography with a phase-shifting mask

Abstract: The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10X tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

Dynamic focusing in the confocal scanning microscope

Abstract: SUMMARY The previously reported depth discrimination property of the confocal scanning microscope, whereby detail outside the focal plane is effectively suppressed from the image, is exploited to give a high resolution system with in principle an indefinitely large depth of focus. The object is scanned axially, and the image built up as each section of the object passes through the focal plane.

Chromatic aberration of a dipteran corneal lens

Abstract: The longitudinal chromatic aberration (variation in the position of focus with wavelength) of corneal facet lenses of the houseflyMusca domestica is measured directly. The result is shown to agree with that calculated using the thick-lens formulas, the measured lens parameters and the dispersion of the refractive index of the lenses, measured with an interference microscope. The longitudinal chromatic aberration between the two wavelengths of peak absorption of fly rhabdomeres (360 nm and 495 nm) is about 2.5 μm and comparable to the depth of focus of the lens, assuming the lens to be diffraction limited. Chromatic aberration is therefore expected to have little effect on optical image quality in the fly; in particular the effect on the modulation transfer function at the receptor level and on the angular sensitivity of the rhabdomeres is insignificant.

Automatic focusing apparatus in optical drawing machine

Abstract: Automatic focusing apparatus in an optical drawing machine, comprising a drawing optical means having a dichroic mirror which transmits light for drawing and reflects light for detecting the focus to apply the focus detecting light to which a photosensitive material is insensitive onto the latter, an imaging lens means, and a focus detecting device for detecting whether the surfaces of the photosensitive material are located in the depth of focus of the drawing optical means.

Characterization Of The Ultratech Wafer Stepper

Abstract: A brief characterization of the Ultratech Model 900 wafer stepper is presented. Excellent control critical dimensions for 1-gum minimum features is accomplished by using a broad spectral bandwidth for exposure which minimizes standing wave effects and by using numerical aperture of 0.315 illuminated with coherence factor of 0.45. Minimal variation in linewidth is seen over 5000A to 8000A poly and metal steps with little evidence of standing wave patterns in the resist profiles. A large depth of focus is obtained with a highly corrected 1:1 lens design which keeps astigmatism and field curvature below 0.5um. The automatic site-by-site alignment system on the Model 900 has proven extremely reliable at all wafer levels with a repeatability better than 0.16um (2 sigma). Lens-to-lens distortion below 0.2um (2 sigma) results from the inherent symmetry in the folded 1:1 design and from careful lens fabrication. A precision lenedistortion test is described with a 2 sigma error below 0.04um and the overlay distortion for the three Ultratech lenses is presented.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Electronic scan type ultrasonic flaw detector

Abstract: PURPOSE:To increase the directional resolution over the entire part of a section image, by extracting only the reflected echo near the focus of an ultrasonic beam by the focal region gate signal which moves in accordance with the depth of focus. CONSTITUTION:The oscillator groups 2 of an array type probe is shifted one by one, and a fan-shape scan is carried out by the focused ultrasonic wave beam having the variable incident angle. Then the signals having different phases and received from the corresponding ultrasonic wave receiver groups are led to a delaying circuit 15, and the delay time equivalent to that of the transmitter side is given so as to be coincident with the center beam of the ultrasonic wave receiver. The output of the circuit 15 is turned into the original waveform by an adder 16 and then receives the wave detection through a wave detector 17. The focal region gate position setting signal corresponding to each set incident angle is delivered to a focal region gate setting circuit 18 from a main control part 5 via a control bus. Then the operation is started and stopped at the focal region gate starting point and with the set value within the focal region gate range. The propagation time of the ultrasonic wave is limited, and only the reflected echo received at the area near the desired focal point is extracted a gated video signal.

Ultrasonic wave receiving circuit

Abstract: PURPOSE:To enable the formation of a clear sectional image by outputting a received ultrasonic wave signal adjusted in the depth of focus as synthesized via a delay circuit, a BPF and the like with a sequential switching. CONSTITUTION:With an ultrasonic beam emitted to an object from vibrators C1-C8, echo signals are received with the vibrators C1-C8 corresponding to depths of the object. The echo signals corresponding to depth shallow are inputted into a time/gain control circuit M or the like via a delay circuit DL1 matching the focal length of the signals, a band pass filter F1 likewise matching it and a coupling circuit H. Similarly, received ultrasonic wave signals adjusted in the depth of focus with the delay circuit and a band-pass filter, e.g. a DL2, F2, DL3, F3 and the like are outputted sequentially via the circuit H. This enables the formation of a clear sectional image depending on an echo signal of the optimum resolution and a high signal-noise ratio with the control interlocking the focusing and filter characteristics to match the depth.

On Easy-to-Handle Holocameras for Endoscopic Applications

Abstract: In spite of the fact that in recent years the performance of the various endoscopes — especially after the introduction of fiber optics — has considerably been improved, they still have several drawbacks. One of these is the very limited depth of focus, another that they have a rather restricted field of view, thus, if information from the entire wall of the cavity.to be investigated is needed, the endoscope has to be rotated around its optical axis.

Stop position learning method for delivering and storehousing crane

Abstract: PURPOSE:To perform a learning work with high accuracy by means of a low- priced photo switch by taking a specified detected place within the depth of focus of one of plural different photo switches to send out a detecting signal. CONSTITUTION:A plurality of limited reflection-type photo switches 49a, 49b having different focal distances are disposed vertically adjacent to each other as detecting means 43 for detecting a support 12 of a shelf 2 at the central position of a carriage 7 in the travelling direction of a crane in such a manner that the read ranges (depth of focus D) overlap each other. The photo switches are connected with a OR gate circuit to output a support detecting signal when at least either of the photo switches 49a, 49b detects the support 12.

Terminal part of image fiber

Abstract: PURPOSE:To prevent the brightness of an image from lowering in circumferential end parts by keeping the difference in heights in an optical axis direction of concave and convex at the end face of an image fiber at <=2tF (t: the spacing between the picture elements of the image fiber, F: F number of an imaging lens). CONSTITUTION:Depth of focus (d) is given by + or -tF when the distance between the picture elements of an image fiber is expressed as t, and the F number of an imaging lens as F as described above. If the end face of the image fiber is of hyperbola, the maximum improvement in coupling efficiency is anticipated, but in general in the stepped curved surface where each split region is constituted of part of the curves convex on the object side, the rays arriving at the end face of the image fiber by passing the center of the lens are more refracted to the optical axis direction as compared to the case of an ordinary end face of a flat surface shape, and therefore the improvement in the coupling efficiency is achieved.

Optical gauge for measuring outer diameter

Abstract: PURPOSE:To permit accurate measurement regardless of positions of a matter by using a parallel light beam obtained through a linear light source and a collimator lens in an optical gauge for measuring outer diameters. CONSTITUTION:A collimator lens 2 is disposed in front of a linear filament light source 10 at a position spaced therefrom by a distance of focal length (f). A light from the light source is turned to a prallel beam through the lens 2. An optical image formed on an image sensor 4 via an aperture slit 3 is dimmed in its part where the beam is interrupted by a bar-like body. Due to use of the parallel light beam in place of a diffusion light from a point light source, there can be eliminated such a need that the material has to be disposed within the depth of focus of the lens, or such a defect that magnification is varied dependent on focus positions.

Microscope depth of focus increasing system - involves axial oscillation of specimen, illuminated by frequency interlocked stroboscopic light source

Abstract: The arrangement is intended for increasing the depth of focus of a light incorporating microscope. The specimen is oscillated in the direction of the optical axis, whilst illuminated, by a narrow-beam or monochromatic triggered light source, e.g. a stroboscopic lamp. The specimen may be oscillated by piezoelectric, mechanical, pneumatic, hydraulic or electromagnetic elements, whilst the light frequency is an integral multiple of the oscillation frequency, the two frequencies preferably being interlocked. Oscillation at 30 Hz, combined with a 300 Hz stroboscopic frequency, results in doubling the depth of focus.

A Two-Dimensional Phased Array with an Extended Depth of Focus: Some Preliminary Results

Abstract: Many pulse-echo acoustic imaging procedures include near-field operation and hence demand some kind of focusing. The medical imaging field, for instance fetal imaging, is but one example where near-field operation is desirable. Acoustic lenses can be used, but these generally result in either a narrow depth of focus, or a small aperture. Alternatively, for imaging systems employing multiple elements, focusing can be achieved by electronic means (Welsby, 1968), a technique which can be extended to permit dynamic focusing (Thurstone and von Ramm, 1973). Yet another approach is the use of annular apertures (Vilkomerson, 1973; Burckhardt et al, 1973, 1975), which can offer a highly directive field pattern in two dimensions extending over a long axial distance. This can be achieved without any kind of physical lens or its electronic analogue, and is a result of the equivalence (apart from amplitude factors) of the field pattern in the Fresnel and Fraunhofer regions of the annular aperture. An annular array has the additional advantage of permitting high speed electronic scanning in two dimensions, resulting in greater versatility and allowing unconventional scan modes. It is the purpose of this paper to describe some results of simulations and experimental work on multi-element annular arrays, operating in pulse-echo at a centre frequency of 2MHz.