Pulse grayscale test card-Global supplier

No. 112 Yingchun South Road, International Science and Technology Building, Wuzhong District, Suzhou City, Jiangsu Province

Introduction to Pulse Grayscale Test Card

This grayscale test card is designed for halftone reproduction and frequency response evaluation of modulation depth in electronic cameras.

A row of gratings is arranged at the center position of the gray background (D=0.75, reminder=18%), generating camera output information at frequencies ranging from 0.5 to 10MHz. Distribution of black and white grayscale test strips with upstream and downstream counter currents.

The density and reflectivity values of the calibrated gray blocks from 1 to 11 are shown in the following table:

Level	Density	Remission in %
1	0.15	71.0
2	0.30	50.0
3	0.45	35.0
4	0.60	25.0
5	0.75	18.5
6	0.90	13.0
7	1.05	9.0
8	1.20	6.0
9	1.35	4.5
10	1.50	3.2
11	1.65	2.2

The density mentioned here is based on BASO4=0 and a level equal to 0.15. The two outer regions (0 and 12) are white (D=0.05, reflectivity=90%) and black. Due to the potential application of reflective materials in this field, test cards with lower densities than grade 11 (D~1.55) can be designed.

Evaluation of grayscale implementation for halftone reproduction. Equipped with a special measurement system (VX700, video options, Optest VTC1）， It can also determine the gamma of the camera.

Using a line grid can determine the contrast transformation function. The reference value for pulse signal amplitude is at 0.5MHz. In order to measure the CTF (Contrast Transfer Function) of the middle, upper, and lower edges, the camera must rotate up and down. Caution must be taken to avoid signal attenuation affecting black and white level determination.

Measurement steps

Measurement can be performed on various camera output signals, but it is preferred to use Y brightness signal (or encode Y with perfect B and W balance). Measure the horizontal color difference of the captured lens at the center and corners of the image. In addition to determining a specific value of 5MHz for camera response, draw a curve based on the measured values of responses at other frequencies, and provide contrast loss (or modulation) based on the spatial frequency analyzed by the test card. Recommend measuring frequency pulse trains at 0.5 MHz and 1 to 7 MHz. Measure the CTF.

The calculation formula can be used to calculate MTF based on CTF value:
MTF（8N）=π/4 CTF（N）+1/3 CTF（3N） - 1/5 CTF（5N）+1/7 CTF（7N） - 1/9 CTF（9N）+1/11 CTF （11N）...]
Among them, N is the spatial frequency of the analyzed test card; N=TVL/ H