Us standard resolution board detailed introduction

2. Design and principle

The design of the USAF resolution board is based on the MIL-STD-150A standard, which was developed by the US Army in 1951, and although the standard was cancelled on October 16, 2006, the USAF 1951 resolution board is still widely accepted and used. It consists of a series of units of different resolutions, each consisting of three sets of lines of different widths, which can be horizontal or vertical.

The design principle of the resolution board is to use these lines to test the resolution of the optical system. When an optical system is imaging, if the spacing between the lines is small enough that they cannot be clearly distinguished, then these lines represent the resolution limit of the optical system. By looking at the clarity of these lines, we can assess the imaging quality of the optical system.

Third, structure and marking

The structure of the US standard resolution board is relatively simple, but the details are very rich. It is usually made of glass or ceramic as the base material, with the USAF 1951 pattern printed on it. This pattern consists of a series of cells of different resolutions, each with a specific group and element marker.

Group and Element are two important concepts in resolution boards. Groups represent different regions on the resolution board, each containing a set of lines with the same resolution properties. Elements are specific combinations of lines within each group, with different widths and spacing.

By looking up the table on the resolution board, we can know the resolution value corresponding to each unit. This value is usually expressed in line pairs per millimeter (lp/mm), which represents the number of lines that an optical system can resolve per millimeter.

Iv. Application

American standard resolution plates are widely used in the field of optics. It can be used not only to evaluate the imaging quality of various optical instruments and equipment, such as microscopes, parallel light tubes, telescopes, etc., but also to evaluate the imaging quality of various lenses and optical components, such as aerial reconnaissance lenses, industrial lenses, aerial mapping lenses, projection objectives, microscopic objectives, camera lenses, camera lenses and industrial camera lenses.

In the aerospace sector, American standard resolution boards are used to evaluate the performance of high-precision optical systems. These systems typically require extremely high resolution and stability to ensure that they work in extreme environments. By using resolution boards, engineers can accurately measure the resolution limits of these systems, allowing them to be optimized and improved.

In daily life, American standard resolution plates are also widely used in the manufacturing and production of optical products. For example, when making camera lenses, manufacturers use resolution boards to test the resolution and distortion of the lens. This helps them ensure that the lenses they produce meet quality standards and are able to meet the needs of consumers.

5. Use and evaluation

When using an American standard resolution plate for evaluation, it is usually necessary to place the resolution plate in front of the optical system to be tested and adjust the focal length and position of the system so that it can image clearly. Then, the resolution limit of the optical system is determined by observing the line clarity on the resolution plate.

During the evaluation process, there are several key factors to be aware of:

Lighting conditions: Lighting conditions have a great impact on the resolution of the test results. Therefore, when conducting tests, it is necessary to ensure that the lighting conditions are stable and bright enough so that the lines on the resolution board can be clearly observed.

Focal length adjustment: The adjustment of focal length is also very important to the test results. If the focal length is not correct, then the imaging system may not be able to clearly image the lines on the resolution plate, resulting in inaccurate test results.

Distortion evaluation: In addition to resolution, a resolution board can be used to evaluate the distortion of an imaging system. By observing the bending and deformation of the lines in the imaging process, the degree of distortion of the system can be judged, and it can be optimized and improved.

6. Resolution calculation and table lookup

Each unit on the US standard resolution board has a specific resolution value, which can be obtained by looking up the table. The lookup table is usually determined by the number of the group and the number of the element. For example, if the group number of a cell is -2 and the element number is 2, its resolution value can be calculated by the following formula:

Resolution_lp_per_mm = 2^(Group + (Element-1)/6)

This formula converts the number of the group and the number of the element to a resolution value (line pairs per millimeter). This value can then be used to evaluate the resolution limit of the optical system.

In addition, some resolution boards also provide line width measurement function. This is usually determined by looking at the width of the lines after imaging. There is a certain relationship between the line width and the resolution, so the resolution of the optical system can be evaluated indirectly by observing the line width.

Seven, spurious resolution and recognition

When using the US standard resolution board for evaluation, there are sometimes spurious resolutions. This means that when a set of lines is blurred enough, the overlap between them may form more flipped lines, resulting in a misreading of the resolution. This phenomenon will interfere with the judgment of the true resolution of the optical system, so special attention is needed.

In order to avoid the effects of spurious resolution, the following measures can be taken:

Use high-quality resolution boards: High-quality resolution boards have sharper lines and more accurate resolution markers, which helps reduce the appearance of spurious resolutions.

Optimize the imaging system: By optimizing the parameters of the imaging system (such as focal length, exposure time, etc.), the sharpness of the lines can be improved, thus reducing the impact of spurious resolution.

Careful observation and analysis: When making an assessment, it is necessary to carefully observe the clarity and shape of the lines, and analyze and compare them. If it is found that there is a spurious resolution, it should be adjusted and corrected in time.

Eight, different types of US standard resolution plates

Us standard resolution boards are available in a variety of types to meet different application needs. Here are some common types:

Glass base resolution plate: Glass base resolution plate has excellent stability and durability, suitable for high-precision measurement and long-term storage.

Ceramic substrate resolution board: Ceramic substrate resolution board has a low weight and good corrosion resistance, which is suitable for application scenarios requiring portability and corrosion resistance.

Positive and negative: Positive and negative are two different forms of resolution boards. A positive film has a dark pattern and a light background, while a negative film has a dark background and a light pattern. These two forms can be selected according to the actual needs.

Maintenance and maintenance

In order to ensure the accuracy and service life of the American standard resolution board, it is necessary to carry out regular maintenance and maintenance. Here are some common maintenance measures:

Cleaning: Wipe the surface of the resolution board regularly with a clean cloth or paper towel to remove dust and dirt. Be careful to avoid using rough cloth or cleaning agents with chemical substances, so as not to damage the surface of the resolution board.

Storage: Store the resolution board in a dry, cool, dark place to avoid damage caused by moisture, heat, or overexposure.

Calibration: The resolution board is calibrated regularly to ensure its accuracy and reliability. Calibration can be done by comparing it with a standard sample of known resolution.

Future development trend

With the continuous development and progress of optical technology, the US standard resolution board is also constantly improving and perfecting. In the future, we can expect the following trends:

Higher resolution: As the resolution of the optical system continues to improve, the US standard resolution board also needs to have a higher resolution to meet the test needs.

Intelligent: Through the introduction of intelligent technology, such as image recognition, data analysis, etc., the test efficiency and accuracy of the resolution board can be improved.

Multifunctional: In addition to resolution testing, other optical performance testing functions can be integrated into the resolution board to meet the needs of a wider range of applications.

Conclusion

As an important optical testing tool, American standard resolution plate has a wide range of applications and important position in the optical field. Through the detailed introduction of its principle, structure, application, use and evaluation, we can better understand and use this tool, and provide strong support for the development and manufacture of optical systems. In the future, with the continuous progress of technology and the continuous expansion of applications, American standard resolution plates will continue to play a greater role and make greater contributions to the development of the optical field.