Application of CINOGY Beam Quality Analyzer in Laser Beam Measurement with Large Divergence Angle

1.

There are different kinds of applications where angular response needs to be considered

Linear transmission at the angle of incidence αin can be described mathematically if the transmission index is known for the vertical beam T0 and the refractive index n is known

Because for absorptive filters, T0 has a very linear relationship with wavelength, the relative transmittance Trel, which is related to the angle of incidence, is also closely related to wavelength

Figure 1: Angular linear sensitivity of KAI-16070 to monochromatic light (unknown wavelength)

Figure 2 Angular linear sensitivity of CMX4000 white light

As these examples show, the angular response can be quite different for different types of sensors

2 coats

With a special coating, we can eliminate (mainly suppress) the angle generation of the sensor itself

The main advantage:

1) The remaining angular response is isotropic, which means it no longer depends on the azimuth of the incident angle

2) The correction factor for the remaining angular response is smaller and therefore less error-prone

The graph below shows two angular response measurements at 940nm for the CinCam cmos Nano 1.
001 with a CMV4000 sensor in front and an OD8 absorption filter
.

The cameras in the first chart are with default settings and no special coatings
.

Figure 3: Angular response of the CMV 4000 sensor in the x (blue) and y (orange) directions with an OD8 absorption filter in front, measured at 940nm
.
The upper part shows the relative angular response, and the lower part shows the relative deviation between the measured points and the best-fit curve
.

The camera in the second picture is made with a special coating
.

Figure 4: Angular response in the x (blue) and y (orange) directions of the CMV 4000 sensor with a special coating and an OD8 absorption filter in front, measured at 940 nm
.
The upper part shows the relative angular response, and the lower part shows the relative deviation between the measured points and the best-fit curve
.

Here, the angular response is isotropic and smooth, and the drop-off effect is less pronounced for large angles
.
The CinCam CMOS Nano Plus-X is optimized for extremely short distances between the sensor and the front of the case
.
This enables angular response measurements at incident angles up to 65°
.

3 Fitting function of angle response

The fitting function is a Zernike2 polynomial, where the sine of the angle of incidence is used for the radius
.
These polynomials provide simple interpolation in the x and y directions for arbitrary directions of the angle of incidence
.
In this way, we can describe measurements up to ±60 degrees with a small number of coefficients
.

4 Uniformity

Due to production reasons, the coating does not have the exact same thickness everywhere
.
This results in increased non-uniformity in camera sensitivity
.
This shortcoming is compensated by further uniformity calibration
.

 

Figure 5: Relative sensitivity of the 940 nm uncoated sensor (purple) and after uniformity calibration (green)
.

5 Accuracy

Overall accuracy depends on the following:

1) Fitting accuracy
.

2) The isotropy of the angular response
.

3) The accuracy of the vertical beam position (x, y)
.

4) Accuracy (z) of the optical distance from the vertex to the sensor
.

5) Angular response drops at maximum angle
.

With special coatings, we can improve the fitting accuracy and the isotropy of the angular response
.
Furthermore, the relative drop in sensitivity at large angles is much weaker
.

6 Correction Requirements in RayCi

In order to correct image data according to the angular response, the following requirements must be met:

1) Angular response calibration data must be available for each wavelength
.
The data consists of the Zernike polynomial coefficients of the best fit
.

2），xy
。

3）
。

4）CINOGY Technologies
。

5）
。

6）RayCi 2.
5.
7
。

Cinogy，CMOS，CMOS30mm，19Mpixel
。、、
。CinCamC/F-Mount ，、、、
。24mmCinCam CMOS-3501CinCam CMOS-3502RayCi-Standard/Pro， 、 、、、（）、/（） 、（） 、 （）、 ， ，PDF
。

：

 1、，36mm

 2、，4.
6um

 3、C/C++, C#, Labview, Java

：
 

RT option: 

CMOS/ccd-xxx-RT：：320~1150nm

UV option:

CMOS/CCD-xxx-UV: Response wavelength range: 150nm~1150nm

CMOS/CCD-xxx-OM: Response wavelength range: 240nm~1150nm

IR option:

CMOS-xxx-IR: Response wavelength range: 400~1150nm + 1470nm~1605nm

For more product information about CINOGY laser beam quality analyzer, please refer to the official website link:

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