Aperture, Yas, PV, RMS, these words are often encountered in optical processing, but different people have different understandings, and even people from the same company are difficult to agree on an understanding.
Here is an excerpt from the optoelectronics-related forums on the Internet and the statements of professionals in the community for your reference.
Three-sided mutual inspection" expressed the following opinions.
There are three main types of surface shape for general evaluation: PVRMS calculated by aperture local aperture interferometer; There are also some indicators in IS010110-5.
I understand the aperture as the difference in radius between the reference and the measured, whether it is a flat template or a spherical template, if it is a circle, then a circle (a stripe interval) represents 05 wavelength surface shape, if the interferometer measures the time, if it is in a circle, then there are two cases, the aperture can be obtained from a single interferogram when measuring the plane, but when measuring the sphere, the aperture cannot be measured, that is, the interferometer can not measure the aperture when measuring the sphere, and in order to get the radius difference of the sphere, it needs to be equipped with a length measuring device. Because the standard spherical mirror of the interferometer only provides a standard spherical wave, and this spherical wave is of any radius, while the standard spherical surface of the model method provides a standard spherical surface with a fixed radius, which is said above.
The second is the astigmatism, he said that between the optical surface and the reference surface between the two perpendicular directions of the number of apertures corresponding to the deviation, the two directions n subtraction, but also look at the aperture symbol, for example, in the case of circular astigmatism, the two directions n symbols are the same, in the saddle shape astigmatism, the two directions n symbols are opposite.
A local aperture is a local deviation corresponding to a local irregularity. The main thing to look at is the ratio between the local fringe offset and the ideal fringe spacing.
The interferometer generally obtains the PV value and RMS value after measurement, the PV value corresponds to the difference between the peak value and the valley value of the wave surface, or it is considered to be the sum of the collapsed edge and the warped edge, and the local aperture is the maximum value between the collapsed edge and the warped edge. Evaluating PV alone is sometimes not objective. RMS is a statistic, mainly to see the slow change of the wave surface, and the RMS value may reflect the wave surface more objectively.
In IS0 10110-5, the wavesurface obtained by the interferometer is divided into SAG and IRR (irregularity), and IRR is divided into rotational symmetry and non-rotational symmetry. For the plane, SAG corresponds to the radius difference, which is a bit similar to the aperture, and also corresponds to the power value (just close), and the IRR is the wavesurface after deducting the SAG, which is a bit similar to the local aperture. It was said above that the interferometer cannot measure the aperture of the spherical optical element, so the interferometer can only get the IRR when measuring the sphere, and the SAG can be calculated by matching the length measuring device, or using the spherical diameter meter, and then entering the reference radius and the comparison radius.
catianshi "Comment as.
The difference between the highest point and the lowest point of the uneven surface of the PV lens, and irregularity is the local aperture, we consider the local aperture of a lens is the ratio of the irregular part of the same interference fringe that deviates from the regularity, but it is not necessarily the difference between the highest point and the lowest point, it is definitely less than or equal to!
When the aperture is less than one, it can be roughly divided into two types, one is that the aperture becomes a straight line, we are used to calling it zero aperture, and the other is an arc, we are used to calling it half an aperture. Yas is a term for Japanese companies, and state-owned or mostly domestic companies are called local errors. Yas's judgment is mainly a comparative method, in the standard interference fringes, the fringe distance is certain, then the distance between the two fringes can be regarded as an aperture, then between the irregular fringes, that is, when Yas appears, it is necessary to see that the line deviates from the standard spacing many times is 02 times, 03 times or more. However, this method is observed with the naked eye, and the error is not small. "Bricks" to express opinions such as.
When the aperture lens and the sample are placed together, they form interference fringes and form a circle. The number of rings is the number of stops. Yas didn't know if that was what you were talking about -- if it was, it should be a mishematism deviation, a deformation of the stripes that were supposed to be circular. If not, then you have to ask the master.
The difference between the highest and lowest points on the surface of a PV lens. The average value of the difference between those potholes on the surface of the RMS lens.
The above data is for reference only and is provided by Nanyang Jingliang Optoelectronics.