After the launch of OPPO Find 5, time is limited. The author briefly introduced the source and advantages of the "stack CMOS" sensor (see《 Against the sky! Find 5 uses a stacked CMOS sensor 》）There are not many technical explanations. In fact, there is not much discussion about the concept of stacked CMOS sensors in the mobile phone industry, but people in the imaging industry are more concerned about it. Now that Find 5 is used for the first time, more manufacturers will use this technology in the future, including Apple, Samsung, Sony, etc. At that time, the highlights will be very rich, even unexpected. For example, how to upgrade the camera of the next generation iPhone? What will it be upgraded to? Now, there is hope.
Without much gossip, we should return to the "stacked CMOS" sensor technology. Stacked CMOS, called "Stacked CMOS" in English, is sometimes translated as "Stacked CMOS". In fact, these concepts refer to the same thing. When it comes to stack CMOS, we should first talk about Sony.
Start with Sony
In the sensor field, the top manufacturers are Sony, Panasonic OmniVision、Aptina、 Samsung, Canon, etc., of which Sony's mobile camera technology makes it difficult for other manufacturers to match, while there is also a significant gap in market share. In terms of the sensor market share in 2011, Sony alone accounted for more than 30%, more than double the second place. Sensors, to a certain extent, highlight Sony's outstanding achievements in the field of optics.
Backlit CMOS
For mobile phone cameras, the sensors used in them are generally CMOS sensors. An obvious disadvantage of early CMOS is that it is easy to generate heat when the current changes, which will eventually cause the image to appear stray spots and affect the image quality. At this time, CMOS cannot be compared with CCD.
With the continuous progress of science and technology, the shortcomings of CMOS have been gradually solved. In June 2008, Sony announced the backlight CMOS sensor, which caused a great response in the industry. Next, more and more cameras began to be equipped with back lit CMOS. Until today, CMOS has been widely used. Especially on mobile phones, almost all have been covered by CMOS.
IPhone 4 starts to adopt back illuminated CMOS
Backlit CMOS is sometimes referred to as "BSI". The advantage is that the imaging effect will be better when taking pictures at night and in high sensitivity.
Why is the backlight CMOS imaging better?
Backlit CMOS has different design methods and better imaging effect than traditional CMOS. The photodiode of the traditional surface illumination camera sensor is located at the lowest layer of the entire chip, while the A/D converter and amplification circuit are located at the upper layer of the photodiode, so the photodiode is farther away from the lens, and the light is easier to lose. At the same time, these line connection layers will also block the light path from the color filter to the photodiode, which directly leads to less light sensitivity. The backlight camera sensor solves this problem. Backlit CMOS sensors have made a qualitative leap in sensitivity compared with traditional CMOS sensors, resulting in a great improvement in focusing ability and image quality under low illumination. The following picture shows the difference between the two.
However, the change in the direction of CMOS means that the board carrying the diode should be very thin, about one percent of the traditional CMOS, and the technical requirements for the production process and micro processing are quite high, which is not easy in the past few years. However, the development of science and technology has changed, and now the technical level has fully met the requirements, so the backlight CMOS has also been widely used. In particular, high-end mobile phones will use back lit CMOS, such as Xiaomi 2, Sony LT26i, Apple iPhone 4, and so on.
Sony Exmor R CMOS
In order to raise the brand height, Sony has uniformly named its own backlight CMOS as the "Exmor R CMOS" brand, which is believed that most people have heard of. Now mainstream flagship phones, such as iPhone 5, Samsung Galaxy S3, Samsung Galaxy Note 2, and Sony LT26ii, all use Sony's sensor products. Of course, this only refers to the main camera. Just take Apple as an example, the camera used by iPhone 4 is still provided by OmniVision, which is also a backlit camera. After 4S, it has been fully replaced by Sony, which reflects the advancement of Sony's backlit CMOS technology to some extent. In addition, due to cost constraints, the camera sensors Apple uses on The New iPad and iPad 4 are not provided by Sony, so the photography level is relatively general.
Back to Sony Exmor R CMOS. Up to now, Exmor R CMOS has accumulated a very good reputation among users and has become synonymous with high-end cameras, which can be said to be "successful". Even Samsung, which also produces sensors, uses Sony products, which shows that its irreplaceability is extraordinary.
How is Gao Fushai Exmor R CMOS refined?
In addition to Sony, other manufacturers such as Panasonic OmniVision、Aptina、 Samsung and others are capable of producing back lit CMOS cameras. But why are they not as good as Sony? The reason is still the core technology. Technology changes destiny, and technology makes life. Let's talk about how Gao Fushai's Exmor R CMOS was refined.
To understand the reason, we need to discuss it more deeply. Sony's backlight CMOS uses SOI (Silicon on Insulator) wafers, which are conducive to grinding and thinning. The thinner the SOI wafers are, the easier the lighting is. The better the lighting ability is, the better the imaging effect can be obtained. Other manufacturers, such as Samsung and OmniVision, mostly use ordinary silicon wafers (bulk silicon wafers). In terms of thickness, SOI wafers can achieve about 1/30 of the bulk silicon wafers, and the advantages of imaging effect can be imagined. However, its cost is 3-4 times higher. In general, the price of Sony's back illuminated CMOS is not low. However, at present, the flagship mobile phone still has a special liking for this CMOS, and the Exmor R CMOS produced by Sony has become a symbol of high-end photography.
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Against the sky! Find 5 uses a stacked CMOS sensor
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