Extremely-low-density flow field schlieren measurement system and method based on programmable spatial light modulator

Abstract

The invention belongs to the technical field of schlieren measurement imaging, discloses an extremely-low-density flow field schlieren measurement system and method based on a programmable spatial light modulator, and aims to solve the problem that low-density flow field shock waves cannot be clearly captured in the prior art. According to the invention, an optical signal is focused on the programmable spatial light modulator through a first focusing mirror; programmable control is carried out on the programmable spatial light modulator through an image fed back by a first CCD image sensor; and the programmable spatial light modulator deflects a relatively bright low-frequency part in a focusing light spot, leaves a relatively dark high-frequency part, reflects the relatively dark high-frequency part to a second focusing reflector, and focuses the relatively dark high-frequency part to a second CCD image sensor through the second focusing reflector, so that imaging observation of a low-density flow field shock wave image is realized. According to the invention, a few nanometers of signals can be detected by filtering out the relatively bright low-frequency part in the light spot, so that the detection of schlieren shock waves in an extremely low-density flow field is realized.

Description

technical field [0001] The invention belongs to the technical field of schlieren measurement and imaging, and in particular relates to a system and method for measuring schlieren in an extremely low-density flow field based on a programmable spatial light modulator. Background technique [0002] Schlieren imaging technology uses the disturbance of airflow to light waves to convert the change of airflow into an image. That is to say, the principle of the schlieren instrument to capture the flow field is to display the refractive index according to the angular deflection of light passing through the airflow of different densities. It is a device for measuring the small deflection angle of light. It converts the change of the density gradient in the flow field into the change of the relative light intensity on the recording plane, making the shock wave and compression wave in the compressible flow field where the density changes rapidly become possible. Observe, distinguishable...

AI Technical Summary

Problems solved by technology

[0013] In order to solve the problem that the existing schlieren method cannot clearly capture the low-density flow field shock wave, a very low-density flow field schlieren measurement system and method based on a programmable spatial light modulator are provided, which can measure the air density below The flow field shock wave under the condition of 10Pa is measured

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