Technical Article

Do you know the four questions about clarity/MTF?

Do you want to study the resolution/clarity/sharpness/MTF of imaging systems in depth? Are you interested in their development history? If it is, you can follow our discussion of the phenomenon and read it:

Phenomenon 1:

There have been many types of test optical imaging system Resolution target patterns in history, such as the famous MIL-STD-150A (USAF 1951) and the wedge diagram in ISO12233:2000, and some other unremarkable but still have the same as the above two Test pattern of the same function.

USAF 1951

ISO12233:2000中的楔形图

具有跟以上两种相同功能的测试图样

At present, many engineers in the mobile phone industry still refer to the measurement results using the former as MTF. So, how do these test patterns relate to MTF?

MTF

Phenomenon 2:

One of the advantages of using the concept of MTF is that the MTF of the system can be decomposed into the product of the MTF of each part. A typical solid-state photoelectric imaging system (such as a camera photoelectric module) is mainly composed of a lens and an imaging sensor. However, we often talk about the MTF of the lens and the SFR of the system (spatial frequency response defined in the ISO 12233 standard) , Then, what is the concept of the MTF of the sensor? What are the factors related to it?

Phenomenon 3:

Many engineers are familiar with the point spread function (PSF) and optical transfer function (OTF) of an optical imaging system as a Fourier transform pair. OTF is a complex variable function, its modulus is our common modulation transfer function (MTF), and its argument is called the phase transfer function (PTF). So, why do we pay little attention to PTF, and what is the relationship between PTF and image quality?

Phenomenon 4:

In the development and testing of imaging systems, we often need to calculate the sampling frequency (and Nyquist frequency) of the area array imaging sensor. For "black and white" monochrome sensors, the calculation of the sampling frequency seems easy.

However, the green channel of the three-color sensor with Bayer-type CFA is staggered, so how to calculate its sampling frequency?