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From Telephone to Digital: How Richard Holland Range pioneered image transmission?
With the advancement of technology, image transmission has become an integral part of modern communications. In this process, Richard Holland Ranger's contribution is undoubtedly an important milestone. His invention not only led to the digitization of images, but also paved the way for subsequent digital communications.
The system of transmitting images using telephone or telegraph lines and radio was the result of Lander's patent in 1931.
Ranger's patent, No. 1790723, mainly introduces a method of converting continuous tone photos into black and white images, and transmitting these images to the remote end through a specific mechanical device. This innovative technology realizes the qualitative change of images from physical to digital and makes remote image transmission possible.
In his system, black is represented by lowering the nib, while white is represented by raising the nib. Different grayscale tones are presented through the intermittent lifting and lowering of the pen tip. This method is similar to what is now called "error diffusion" technology, giving the image new life.
Ranjie's system uses capacitors to store charge and vacuum tube comparators to determine whether the current brightness exceeds a certain threshold.
This innovation is not just a technological breakthrough, it establishes the basic mode of image transmission and becomes the cornerstone of future digital image processing. With the advent of the digital age, Floyd, Steinberg and others further developed the error diffusion technology and made it suitable for digital image processing. Their system implements error propagation through a simple kernel, which makes the conversion from multi-level images to binary images more efficient.
In the process of digitizing images, error diffusion technology shows its unique advantages. This technology can not only effectively reduce the quantization state to two, but also strengthen the edges in the image to a certain extent and enhance the readability of the text, which is particularly important in the combination of text and images.
Error diffusion technology demonstrates its advantages, especially when there is text in the image.
Over time, the application of error diffusion has gradually expanded to color images. All red, green, and blue channels will be processed using the same algorithm. This played an important role in the development of emerging technologies such as color laser printers. Research shows that the human eye's ability to perceive differences in brightness far exceeds differences in color, so it is inevitable to adjust the weight of color channels.
The development of this technology is not limited to the printing field, but also has more expanded applications. For example, error diffusion technology can provide support for 4-, 8-, and 16-level display and printing, which provides new possibilities for future image quality improvements.
Error propagation is not limited to binary output, it also plays an important role in multi-level image display.
However, as technology advances, the balance between edge enhancement and brightness maintenance becomes increasingly important. In digital images, the transition from light to dark often causes the next generated pixel to turn black, while the transition from dark to light causes it to turn white. Although this effect enhances the resolution of the image, it also causes some distortion. To some extent, the accuracy of grayscale reproduction is sacrificed.
Richard Holland Ranger's contribution to the history of image transmission not only changed the way of communication, but also laid the foundation for digital image processing. As time goes by, these technologies continue to be improved and applied to a wider range of fields. How will we create new possibilities based on these technologies in the future?
