optical calibration plate

application field

Hongcheng Optical Glass Series Calibration Plates and Ceramic Series Calibration Plates are commonly used calibration tools specially used by customer groups such as university experiments, research unit project development, and machine vision integrator product calibration. They can easily obtain camera calibration data.

Function of the calibration plate:

In order to correct lens distortion, determine the conversion relationship between physical size and pixels, and determine the relationship between the three-dimensional geometric position of a point on the surface of a space object and its corresponding point in the image, a geometric model of camera imaging needs to be established. It is a dedicated high-precision calibration tool for research units and the field of vision. It mainly obtains data of camera calibration results through calibration software for three-dimensional image measurement, three-dimensional reverse engineering, stereo matching, three-dimensional reconstruction, etc.

Hongcheng Optics can customize various calibration plates and correction plates.

Calibration plate material:

Material 1: Soda glass: The color of the calibration plates used in Russia is silver; the color of the calibration plates in Germany and Austria is blue; the color of the calibration plates in the United States and Japan is yellow. This color is determined by the coating process, and the quality of the calibration plate cannot be judged by the color alone. The high-end color of the domestic calibration plate is yellow, and the cost of other colors is relatively low. Standard production process: The glass substrate must be polished, cleaned, coated, etc. The film layer is firm and there are few defects during the post-production process. If one of the processes is reduced or the machine used is not very good, the cost of the product will be much cheaper, and the quality will not be very good. Example: If it is made according to normal processes, the size is 63mm * 63mm, and the price of mass production will be at least more than 100 yuan.

Material 2: The standard plate with ceramic substrate has the characteristics of small thermal expansion coefficient, high strength, high hardness, good wear resistance, low thermal conductivity, and good acid and alkali resistance. It also has good surface diffuse reflection treatment, which solves the problem of the application process. During the process, the problem of reflecting light from the glass calibration plate under the condition of a front light source can be better identified, and the detailed information of the calibration plate pattern can be better identified to achieve higher calibration accuracy and measurement accuracy.

Material 3: Quartz material has good light transmission and the biggest advantage: small expansion coefficient. During the process of calibrating the instrument, it is less affected by the ambient temperature. The corresponding cost is also high. Quartz materials are divided into JGS1 and JGS2. JGS1 is expensive. JGS2 is relatively cheap and has bubbles inside.

Material 4: Matte metal and aluminum calibration plate: The biggest advantage of this calibration plate is that it is resistant to fall, durable, and is opaque to light and non-reflective. Its good surface diffuse reflection treatment solves the problem of reflecting light from the glass calibration plate under the condition of front light source during application, and better identifies the details of the calibration pattern to achieve higher calibration accuracy and measurement accuracy.

Material 5: Photo paper material: Advantages: Light and thin, non-reflective, low cost, easy to produce. The disadvantage is that it is not waterproof and oil resistant.

Material 6: Film material: Film is also film. It is generally composed of five parts of materials: protective film, photosensitive emulsion, adhesive layer, film base, and anti-halo layer. When light shines on the silver halide, the silver halide transforms into black silver, which is fixed on the film base after a development process, becoming a black-and-white negative we often see. Color negatives are coated with three layers of silver halide to express the three primary colors.

About calibration plate selection:

I. Select calibration plate size:

Select the appropriate calibration plate according to the size of the field of view. The halcon document recommends that the size of the calibration plate pattern should be at least larger than 1/4 of the field of view and smaller than the entire field of view, and take 15-20 calibration images; it is recommended that the calibration plate pattern should be larger than 1/3 of the field of view and smaller than the entire field of view, and the number of calibration images depends on requirements; for the halcon12 version of the calibration plate, it is recommended that the calibration plate pattern should be larger than the field of view area, and about 5 calibration images should be used in different postures; Halcon12 version of calibration boards currently only supports halcon12 , but halcon12 version software can use previous versions of calibration boards.

2. 2. How to select the material of the calibration plate:

Please choose a ceramic/metal calibration plate for the front light source to avoid reflection. Optical glass material can be selected for the backlight source.

III. The drawings of the calibration plate are as follows:

1. Materials need to be attached

2. accuracy

3. Overall size tolerance, thickness

4. Making effect drawings: grading of positive and negative boards. (If you consider price factors, you need to emphasize how many factors are allowed to see flaws below)

5. Detailed CAD drawings need to be provided (it is better not to draw scale drawings). The above is complete information on making a calibration board

Our calibration plate accuracy can reach 1um. The color can be dark yellow, blue, silver, and dark blue. Positioning holes can be made on the board, and the size can be made into a large calibration board with a size of about 800*960mm to meet customers 'large field of view calibration needs.

Calibration plate selection parameter table:

Regular halcon dots:

Common specifications for halcon dot calibration plate

model

Overall size (mm)

Effective area (mm)

Circle diameter (mm)

Center distance (mm)

array

HC-H5.6-0.35

Slightly larger than the graphic area

5.6*5.6

0.35

0.7

7*7

HC-H8-0.5

8.8*8.8

8*8

0.5

1

7*7

HC-H10-0.625

Slightly larger than the graphic area

10*10

0.625

1.25

7*7

HC-H16-1

16*16

16*16

1

2

7*7

HC-H20-1.25

Slightly larger than the graphic area

20*20

1.25

2.5

7*7

HC-H30-1.6

50*50 or 30*30

30*30

1.6

3.2

7*7

HC-H30-1.875

50*50 or 30*30

30*30

1.875

3.75

7*7

HC-H36-2

63*63

36*36

2

4

7*7

HC-H63-3

63*63

63*63

3

6

7*7

HC-H100-4

100