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Differential laser Doppler velocimetry for cross-sectional velocity distribution measurements using 48-channel spatial encoding and nonmechanical scanning
摘要： A differential laser Doppler velocimeter using 48-channel spatial encoded measurement points is proposed for dense cross-sectional velocity distribution measurements. An asymmetrical push–pull configuration and multiple photodiodes are employed to increase the number of the measurement points. The functionality of the proposed structure is experimentally demonstrated. The results indicate that a cross-sectional velocity distribution is successfully measured with the proposed structure.
关键词： Nonmechanical scanning,Spatial encoding,Interferometry,Laser Doppler velocimetry
更新于2025-09-19 17:13:59
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A Traceable High-Accuracy Velocity Measurement by Electro-Optic Dual-Comb Interferometry
摘要： An electro-optic dual-comb Doppler velocimeter for high-accuracy velocity measurement is presented in this paper. The velocity information of the object can be accurately extracted from the change of repetition frequency, which is in the microwave frequency domain and can be locked to an atomic clock. We generate two optical combs by electro-optic phase modulators and trace their repetition frequencies to the rubidium clock. One functions as the measurement laser and the other the reference. Experimentally, we verify its high accuracy in the range of 100–300 mm/s with a maximum deviation of 0.44 mm/s. The proposed velocimeter combines the merits of high accuracy and wide range. In addition, since the repetition frequency used for the measurement is traceable to the rubidium clock, its potential superiority in traceability can be utilized in velocity metrology.
关键词： electro-optic dual-comb interferometry,Traceability,laser Doppler velocimetry
更新于2025-09-12 10:27:22
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Assessing the infinitely expanding intersection region for the development of large-scale multipoint laser Doppler velocimetry
摘要： Multipoint laser Doppler velocimetry (MLDV) has been effective for non-invasively measuring the flow velocity distribution with a high-spatial and high-time resolution. The flow velocity can be estimated using a scattered light signal by seeding particles passing through a fringe pattern formed in the intersection region of two laser beams. The shape of this intersection region can be easily changed by changing the optical components and positions of the lasers. An infinitely expanding intersection region is proposed in the present paper. A wide intersection region was indicated by the measurement results of flow velocity. The intersection region is evaluated using a flow channel (1.4 mm ? 1.4 mm). The area of the operating measurement region exceeds 150 mm in the horizontal direction and is less than ?10 mm in the vertical direction. This new MLDV is referred to as a large-scale MLDV.
关键词： flow velocity distribution,high-spatial resolution,large-scale MLDV,intersection region,high-time resolution,Multipoint laser Doppler velocimetry,MLDV
更新于2025-09-12 10:27:22
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Revascularization of Free Skin Grafts Overlying Modified Hughes Tarsoconjunctival Flaps Monitored Using Laser-Based Techniques
摘要： Purpose: It has recently been shown that the flap pedicle does not supply blood to a tarsoconjunctival graft in the modified Hughes procedure in patients. This raises questions concerning the rate of revascularization of the free skin graft commonly used to reconstruct the anterior lamella. The aim of this study was, thus, to monitor the course of revascularization in free skin grafts overlying modified Hughes tarsoconjunctival flaps, using laser-based techniques. Methods: Free skin grafts from the upper eyelid or upper arm in 9 patients were used to cover a tarsoconjunctival flap according to the modified Hughes procedure. Blood perfusion was monitored using laser speckle contrast imaging, and vascular reactivity was studied with laser Doppler velocimetry after heating the tissue to 44°C. Measurements were made at the time of surgery (baseline) and at 1, 3, 8, and 16 weeks postoperatively. Results: The gradual increase in perfusion of the free skin grafts during the healing process indicates revascularization. A slight increase in perfusion was seen already after 1 week. Perfusion reached 50% of the baseline after 3 weeks, and complete restoration of perfusion was seen after 8 weeks. The vascular function monitored with heat-induced hyperemia increased in a similar fashion. Conclusions: Full-thickness skin grafts revascularize within 3 to 8 weeks, despite overlying a tarsoconjunctival flap, which has recently been reported to be avascular. This provides further evidence that it should be possible to repair large eyelid defects using free full-thickness eyelid grafts.
关键词： laser Doppler velocimetry,revascularization,laser speckle contrast imaging,free skin grafts,modified Hughes tarsoconjunctival flaps
更新于2025-09-11 14:15:04