Volume Illumination

IES Lighting HanHhnnk. Reference Volume. Illuminating Engineering Society New York, 1981, Figures 8-21 and 8-36. 

Figure 6.9. Spectrometer depth of field, Sa, for large and small / /. The region sampled by the spectrometer is the overlap between the depth of focus and the sample volume illuminated by the laser.

These photoacoustic experiments are characterized by their geometry, as shown by Fig. 2, and by the ratio of two important time parameters [84-89]. These are the half-width of the laser pulse (tp) and the time (x,) which the acoustic wave needs to traverse the cylindrical volume illuminated by the la r beam. For x we have ... 

A UV double pulsed Nd YAG laser (Litron Lasers) illuminated the micro-fluidic device from a 45° angle with a 355 nm beam (volume illumination). The observation region was 30 mm away from the inlet. The laser beams excited the particles which emitted blue light within a band centred on 445 nm. Particle blue fluorescence was detected by a 12bit 4 MPixels 16 fjps CCD camera (TSI instmments), focused on the test section, after passing through a narrow pass band filter centred... 

Fourth in a series dating from 1977, this volume illuminates current trends and likely future developments in the field of chemical signaling in vertebrates. Going back even farther, the first chapter, a personal account of the past quarter century by Dr. Mykytowycz recalls the most important milestones, such as symposia, or the founding of societies and journals. He also credits those investigators who stand out by their seminal studies. 

Particularly the temperature measurement with encapsulated TLCs shows extensive deviation in the reflected wave length. To minimize this, the illumination technique should be enhanced to receive a uniform illuminated FOV. Furthermore strong illumination is needed for applications with high lateral and temporal resolution. Another problem is the heat introduced by the illumination especially when continuous volume illumination is used. A pulsed illumination decreases this effect. 

At visualization of flows, the measurement depth and field of view define the measurement volume. The extension of the measurement volume in the direction of the camera is the measurement depth. If volume illumination is used, the measurement depth is dependent on the depth of field of the camera optics. Otherwise, when illuminating with a light sheet, the measurement depth is... 

In volume-illumination PIV (e.g., pPIV), the particle images are more complex. Since the entire channel is illuminated, all of the particles within the depth of field of the camera contribute to the... 

In the case of volume illumination, Eqs. 11 and 12 still hold, except that the term for the particle image diameter must be replaced by an integral over the depth of the device. The cumbersome calculation of the integral term for de can be avoided by manipulation of Eqs. 11 and 12. Squaring Eq. 11 and subtracting it from the square of Eq. 12 gives the equation... 

The depth of the field for a volume-illuminated p-PIV setup does not define precisely the thickness of the measurement plane because only the sharply focused particles contribute to the correlation function. The depth of the field is defined as twice the distance from the object plane to the plane in which the object is regarded as unfocused. The depth of correlation depends on the axial distance from the object plane in which a particle becomes sufficiently out of focus so that it no longer contributes significantly to the peak in the particle-image correlation function and can be calculated according to... 

The application of TLCs in liquids is well known for bigger fields of view and slower flow rates and was employed by Dabiri and Gharib [7]. Typical investigated processes are free convection in a tube or crystallization of water (e. g. [6]). Only a few experiments have taken place with a high lateral resolution. Richards and Richards [17] put TLCs in a water droplet which was cooled by an air flow. The diameter of the droplet was less than 1 mm and they investigated the temperature profile with a spatial resolution of 100 [im. They used volume illumination and a CCD camera with a depth of field of 100 im. 

Volume illumination is an illumination method for image capturing where the whole volume around the focus plane is illuminated. The illumination axis is the same as the camera axis (one-axis-Ulumination) or the directions of illumination and camera are similar. Volume illumination and illumination with a light sheet are used for PIV... 

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