After the Powell prism is irradiated by the laser, a one-dimensional linear laser with one-dimensional divergent is formed. What is the speckle size formula of the speckle pattern obtained by the linear laser passing through the scattering plate? The divergence angle is assumed to be θ
Roughly you can estimate the speckle size in the fare field as follows:
Average Speckle diameter = Lambda*L/d, where Lambda is the wavelength, L is the distance from the scatterer to the target screen (where the speckle pattern is measured). So for the laser beam spread in line it is going to be a pattern of extremely elongated speckles.
The size in the direction across the laser line can be estimated as:
Speckle length = Lambda*L/d, where d is the effective size (thickness) of the line.
Speckle width = Lambda*L/d, where d is the effective length of the line (the peripheral and central parts contribute differently depending on the scattering diagram). Note that the speckle pattern is elongated in the direction across the laser line. Any further question (like about the dynamic speckles) let me know.
@Leonid Vesselov, thanks your anwser,However, the speckle formula I want to know is the one-dimensional divergent linear speckle size formula. According to my experiment, after a one-dimensional divergent linear laser passes through the diffuser, the speckle size in the non divergent direction is what you said, but the speckle size in the divergent direction is not like this, which is directly related to the divergence angle.
Dear Yong, the speckle pattern I described is a simple theoretical estimate.
In practice it depends the coherence of the laser beam. In your case you have high coherence in the non divergent direction but lower coherence within the high divergence line. In this case the effective length in my estimate reduces, and the speckle pattern is a combination of many partial patterns, which results in larger average speckle size. It also depends on the coherence of the laser itself. So what you can see in your experiment depends on the geometry, especially in the direction of the high divergence plane. If you provide geometry and the laser type, I might be of a better advisor for you.
@Leonid Vesselov，thank you very much for your reply again.The scattering surface is rectangular and nearly linear， its length-width is about 20mm × 0.8mm.The high divergence direction corresponds to the length and the non divergent direction corresponds to the width.The divergence angle is 30 °.The laser type is 360nm UV laser.
what is the output power of the laser? what is the distance between the diverging prism and the scattering slide? What is the distance from the scattering slide to the target where the speckle pattern is measured?
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