A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

Phase shifting algorithms for fringe projection profilometry: A review

In an apparatus for producing a three-dimensional object by laser sintering the object is produced by successive solidification of layers of a powder material at points corresponding to a cross-section of said object using radiation for solidifying said powder material. The apparatus includes a support having a substantially plane upper side for supporting the object, a material applying device for applying a layer of the material onto the upper side or onto another layer formed on the upper side, and a solidification device for solidifying a layer of the material by irradiation. The material applying device has a coating device and a drive for displacing the coating device in a direction parallel to the upper side of the support. The coating device has a first side face, a second side face, a base surface parallel to the upper side and facing the same, a first edge portion between the first side face and the base surface, the first edge portion including a first angle of inclination with the base surface, and a second edge portion between the second side face and the base surface, the second edge portion including a second angle of inclination with the base surface, the second angle of inclination being smaller than the first angle of inclination.

Method and apparatus for producing a three-dimensional object

An augmented reality system provides improved focus of real and virtual objects. A see-through display device includes a variable focus lens a user looks through. A focal region adjustment unit automatically focuses the variable focus lens in a current user focal region. A microdisplay assembly attached to the see-through display device generates a virtual object for display in the user's current focal region by adjusting its focal region. The variable focus lens may also be adjusted to provide one or more zoom features. Visual enhancement of an object may also be provided to improve a user's perception of an object.

Automatic focus improvement for augmented reality displays

The technology provides an augmented reality display system for displaying a virtual object to be in focus when viewed by a user. In one embodiment, the focal region of the user is tracked, and a virtual object within the user focal region is displayed to appear in the focal region. As the user changes focus between virtual objects, they appear to naturally move in and out of focus as real objects in a physical environment would. The change of focus for the virtual object images is caused by changing a focal region of light processing elements in an optical path of a microdisplay assembly of the augmented reality display system. In some embodiments, a range of focal regions are swept through at a sweep rate by adjusting the elements in the optical path of the microdisplay assembly.

Automatic variable virtual focus for augmented reality displays

A new type of heterodyne interferometer was made through direct modulation of a diode laser wavelength. A measurement accuracy of better than λ/50 and repeatability of λ/100 were obtained. This interferometer shows promise for use in testing wavefront aberrations, especially in optical disk systems.

Diode laser direct modulation heterodyne interferometer.

An optical module for an optical device and an optical fiber is constituted by a pre-molded plastic package. In forming the plastic package, the main flowing direction of the molding resin is substantially parallel with the optical axis of the optical fiber. The optical module is formed by molding the resin by an injection method using pressure and then solidifying the resin. When the plastic package is formed by comprehensive molding, the flowing direction of the resin is parallel with the optical axis direction of the optical fiber to be installed in the optical module. As a result, for comprehensive molding, the molding pressure applied to the optical fiber is reduced. By using the resin case that is formed, the resulting package exhibits high rigidity and low thermal expansion properties in connection with the flowing direction of the resin, thus reducing the external stress and thermal stress applied to the optical fiber.

Optical module, method for manufacturing optical module and optical communication apparatus

An optical device includes a phase-locked diodelaser array (10), a collimator lens (17), and behind the collimator lens a prism system (30, 34) of at least one prism to broaden the far field radiation pattern in the lateral plane (XY) and a spatial filter (19) to select a favored mode The laser radiation is concentrated into a single, round and diffraction limited spot (V)

Optical device with phase-locked diodelaser array

An optical disk head having a short wavelength light source has an aperture diaphragm placed in the course of its focusing optical system which can change its aperture diameter depending on the pit size on an optical disk in order to allow recording on and reproducing from not only a short wavelength optical disk, but also a long wavelength optical disk. The aperture diameter is made larger for the smaller pit size and vice versa, and the light source output is adjusted depending on the aperture diameter so that the light amount coming from the disk surface to a photodetector cannot be changed with the aperture diameter.

Short wavelength optical disk head having a changeable aperture

The green noise in intracavity-doubled Nd:YVO4 lasers can be eliminated by single-mode operation of the device, although good long-term stability remains a problem. We have studied the threshold when multimode operation sets in, with both respect to polarization modes and longitudinal modes, as a function of various cavity parameters. It is demonstrated that the device is sensitive to perturbations in the birefringence and the optical path length of the elements in the cavity. The influence of energy migration and intensity-dependent losses that are due to frequency conversion is also discussed. Good control of the cavity temperature and dimensions is a key point for long-term stability.

Kimio Tatsuno

Papers

Diode laser direct modulation heterodyne interferometer.

Optical module, method for manufacturing optical module and optical communication apparatus

Optical device with phase-locked diodelaser array

Short wavelength optical disk head having a changeable aperture

Stable single-mode operation of intracavity-doubled diode-pumped Nd:YVO 4 lasers: theoretical study