An optical doppler intravital velocimeter
Related Experiment Video
Updated: Feb 9, 2026

Blood Flow Imaging with Ultrafast Doppler
Published on: October 14, 2020
Abstract:
A system has been implemented for measurement of red blood cell velocity in microvessels by using an optical Doppler technique. Ronchi rulings are used to stimulate a differential grating to translate red blood cell movement to light intensity variations. These variations are sensed by two photodiodes coupled in a resistive subtraction mode. The nonelectronic subtraction allows high transimpedance gains (2 X 10(9) V/I) while noise is held to a minimum (4.5 mv RMS in a 5-kHz bandwidth). To derive average velocity the average frequency determination of the amplified signal is performed with a thresholding frequency-to-voltage functional block. The velocimeter provides the typical performance features of an optical Doppler system, including high-frequency response, without the need for the complications of the laser Doppler technique or the requirement of custom micro-prism gratings. The device represents a cost-effective approach to intravital work, and offers significant improvements in performance over standard techniques.
Related Concept Videos
Doppler Effect - I
Doppler Effect - II
Assessing Blood pressure using a doppler ultrasound
Pre-Procedural Guidelines for Doppler Ultrasound Blood Pressure Assessment:
Preparation of Equipment:
Properties of Enantiomers and Optical Activity
Imaging Biological Samples with Optical Microscopy
In optical microscopy, the specimen to be viewed is placed on a glass slide and clipped on the stage...
Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...

