The Influence of IR CUT Dual Filter on Video Imaging Technology

The infrared cut-off degree, transmittance, and light shaping effect of the filter directly affect the image clarity or color of CCD and CMOS.

The image sensor plays a crucial role in the imaging effect. The higher the pixel, the more photosensitive electrodes integrated inside the image sensor. At the same time, we should also consider that increasing the pixel potential inevitably involves manufacturing costs. For every level increase, the price of digital cameras will be higher. Moreover, after reaching a certain level of improvement, CCD sensors are difficult to break through in a short period of time due to manufacturing process limitations.

At present, mainstream DSLR models use CCDs with a maximum of around 6 million pixels. Even though Sony has produced CCDs with 7 million or 8 million pixels, if they are to be installed inside the DSLR body, the final effect will only go against expectations and be unrealistic. However, CMOS sensors have over 16 million pixels.

The imaging principle of CMOS

CMOS can be divided into Passive Pixel Sensor CMOS and Active Pixel Sensor CMOS. It was originally an important chip in computer systems, storing the most basic information for system booting. But someone accidentally discovered that CMOS processing can also be used as an image sensor in digital cameras. It was first introduced to the market by XirLink in 1999, and in May 2000, Omnivision, a US company, launched a new generation of CMOS chips.

CMOS was initially attempted to be used in digital cameras, but compared to the then popular CCD, it had poor signal-to-noise ratio and insufficient sensitivity, so it did not occupy the mainstream position. Of course, it also has multiple advantages. Ordinary CCDs require at least three power supply voltages, but CMOS can operate on a single power supply and consumes less power at the same pixel level compared to CCD products. In addition, CMOS is a standard process that can utilize existing semiconductor manufacturing lines without the need for additional investment in production equipment, and its quality can be improved with the advancement of semiconductor technology. This is precisely why Sony's IRCUT dual filter has been able to develop and manufacture CMOS chips in a very short period of time this year.

From a technical perspective, the imaging principle is composed of a photosensitive electrode, an electrical signal conversion unit, a signal transmission transistor, and a signal amplifier per unit pixel in the core structure. In theory, the light sensed by CMOS is converted into negative and positive charges on the electrodes through photoelectric conversion. The electrical signals (current or potential difference) generated by these two complementary effects are sequentially extracted by CMOS from one pixel to an external A/D converter, and then recorded and interpreted into images by the processing chip.

In specific work, the horizontal transmission unit first collects signals, and then the vertical transmission unit sends out all signals. Therefore, CMOS sensors can amplify signals on a pixel by pixel basis. This method can perform fast data scanning and can handle information processing speeds of millions of pixels, which CCD alone cannot match.

Although CMOS had many drawbacks at the time, practical solutions have been found over the years. Canon is considered the most accomplished manufacturer in the CMOS field, making revolutionary changes to CMOS technology in 2001. Currently, several other technologies have Canon's technological influence.

a. Partial surface noise reduction technology. In order to eliminate the drift and noise of each pixel, the original sensor control part has been redesigned with an amplification circuit that only absorbs noise signals and does not process optical signals. This can remove noise from the optical signal, allowing the sensor to read the signal with a high signal-to-noise ratio.

b. Full pixel charge transfer technology. Due to the fact that the initial value changes every time the signal is read, relying solely on noise elimination techniques on the sensor control circuit cannot perfectly solve this problem. By introducing full pixel charge transfer technology, optical signals can be maintained and high signal-to-noise ratio processing can be achieved.

c. Sensor simulation processing technology. A PGA programmable gain converter is integrated into the sensor control electrical circuit, effectively reducing noise and accelerating signal output capability, making high-speed continuous shooting of about 3 frames per second possible.

The Future of CMOS Development

From the perspective of two types of sensors, CMOS can overcome the difficulties of high pixel manufacturing processes without modifying the manufacturing assembly line, and the improvement of pixels is slightly easier than CCD. The production line is the weakness of CCD manufacturing. As the size of CCD increases, the production line often needs to be adjusted accordingly. Therefore, this is also the reason why the price of high pixel CCD remains high in the international market. Basically, the increase in pixel count in CMOS is complementary to the increase in sensor size, which prevents the scene that occurs in CCD at this time; — The use of a 5-megapixel 2/3-inch frame with 8 million pixels is still a tough situation, so its tolerance, signal-to-noise ratio, and other aspects are superior to small-sized CCDs. This is also one of the reasons why 8-megapixel CCDs cannot be used in DSLR bodies to this day.

The development and use of CMOS was originally just a relief measure by Canon to avoid being controlled by others. Now it seems that CMOS has truly embodied the myth of an ugly duckling turning into a white swan. Looking at the current security market, the vast majority of network cameras, especially high-definition network cameras, use CMOS models, with pixel counts generally divided into 300000, 1.3 million, 2 million, and 5 million pixels.

Due to the continuous improvement of CMOS quality and the significant decrease in production costs, CMOS has already taken up half of the market share and has the potential to replace CCD.

Ruicheng Optoelectronic Technology Co., Ltd. specializes in the production of various optical filters, including bandpass filters, narrowband filters, long wave pass filters, short wave pass filters, dichroic mirrors, spectrometers, lenses, attenuators, polarizers, infrared cut-off filters, transparent infrared acrylic filters, notch filters, biochemical testing equipment filters, four-wheel alignment instrument filters, enzyme-linked immunosorbent assay (ELISA) filters, biometric filters, infrared induction filters, laser rangefinder filters, window lenses, laser equipment lenses, full reflection mirrors, half reflection mirrors, focusing mirrors, compound mirror groups, laser marking machine lenses, laser welding machine lenses, laser cutting machine lenses, laser laser engraving machine lenses, focusing lenses, etc. Our company is a design and research and development company. A professional team that integrates production and sales, The optical solution provider around you!