A real-time reference free background oriented schlieren system is provided. One embodiment includes a display device capable of generating an image pattern projected onto a retroreflective background. A beam splitter is used to transmit a portion of the projected image pattern towards a reference image sensor and another portion of the image pattern towards the retroreflective background and past a density object. The retroreflective background reflects the projected pattern back through the beam splitter and onto a signal imaging sensor. Collected data from the reference image sensor and the signal image sensor may be processed in real-time. The image pattern may be altered as necessary without requiring a new reference image, reducing the amount of time required to set up and adjust the system. A display device may be capable of switching between a schlieren visualization capability to a shadowgraph system allowing for the use of two different imaging techniques.

Light is projected through a grid (e.g., a Ronchi ruling) and onto a background, where it forms an image of the ruling. The light from this projected image is then reflected back onto the same grid, with a polarizing refractor (e.g., a Rochon polarizing prism) imparting a small offset between the projected and reflected light, and then on to an imaging camera. Thus, a separate source and cutoff grid is not needed, resulting in a focusing schlieren system that is compact and easy to construct and align. In some embodiments, translation of the polarizing refractor along the instrument axis provides a sensitivity adjustment of the resulting schlieren images. Manipulation of the polarization state of the light through the system allows the projected and reflected light to be coincident, maintaining a small footprint for the system, which can be mounted to the front of the imaging camera.

A method for determining a local refractive power in a volume element of a transparent object using a pattern includes observing the pattern through the transparent object by a first camera, determining, using the observed pattern, a three-dimensional (3-D) shape and position of a surface of a particular volume element of the transparent object facing the pattern and using the determined 3-D shape and surface position of the particular volume element, determining a local refractive power for the particular volume element.

A system for visualizing catheter irrigation, the system includes a fluid container, a pump, a schlieren imaging assembly and a processor. The fluid container is configured to: (i) contain a first fluid, which is at least partially transparent and has a first temperature, and (ii) receive into the first fluid a catheter having one or more irrigation holes. The pump is configured to inject, through the one or more irrigation holes, a second fluid, which is at least partially transparent and has a second different temperature. The schlieren imaging assembly is configured to acquire schlieren images of turbulence occurring in the first fluid when injecting the second fluid, and the processor is configured to visualize the irrigation using the schlieren images.

An apparatus includes a schlieren imaging assembly and a processor. The schlieren imaging assembly includes one or more two-dimensional (2D) schlieren imaging systems and is configured to acquire two-dimensional (2D) schlieren images of turbulence occurring in fluid media from a plurality of viewing angles. The processor is configured to produce, from the 2D schlieren images, a time-series of three-dimensional (3D) schlieren images corresponding to respective time instances.

A system for measuring (200) a sample (2) by deflectometry comprising: a source (10) for generating a light beam in a source plane (105); an illumination module (19) for forming an illumination beam (9) comprising: a first converging optical element (18); a first selection optical element (16) with a first aperture (160); reflective matrix optical modulation means (30) to form a pattern (7), said first aperture (160) being configured to control the angles of said illumination beam (9) on said reflective matrix optical modulation means (30); a Schlieren lens (20) for obtaining an angle-intensity encoding of said pattern (7) on the sample (2); imaging (40) and detecting means (50) for detecting an image of said sample (2).

Embodiments of the present application are directed toward a focusing Schlieren technique that is capable of adding color-coded directional information to the visualization of density gradients. Other advantages of the technique can include that it does not require manual calibration, has a simple design and is sensitive enough to be used in compact experimental setups. Certain embodiments include the use of a color-coded source image that replaces the conventional source grid. The technique may benefit from a computer-controlled digital background, which is used for both illumination and display of color-coded source images.

According to one embodiment, an optical test apparatus includes a light convergence element, an optical filter, and an image sensor. The light convergence element converges light from a subject. The optical filter is arranged on an optical axis of the light convergence element. The image sensor is arranged in an effective region not crossing the optical axis of the light convergence element, and receives light passing through the light convergence element and the optical filter.

A real-time reference free background oriented schlieren system is provided. One embodiment includes a display device capable of generating an image pattern projected onto a retroreflective background. A beam splitter is used to transmit a portion of the projected image pattern towards a reference image sensor and another portion of the image pattern towards the retroreflective background and past a density object. The retroreflective background reflects the projected pattern back through the beam splitter and onto a signal imaging sensor. Collected data from the reference image sensor and the signal image sensor may be processed in real-time. The image pattern may be altered as necessary without requiring a new reference image, reducing the amount of time required to set up and adjust the system. A display device may be capable of switching between a schlieren visualization capability to a shadowgraph system allowing for the use of two different imaging techniques.

According to one embodiment, a measurement method includes: acquiring a first picture including a background image and a substance, the substance allowing transmission of light from the background image; acquiring a second picture including the background image and the substance in a different positional relation with respect to the first picture; and calculating a first displacement amount representing a difference in position of the background image between the first picture and the second picture.