1/2.4 inch phase focus depth analysis Sony IMX230

Sony's Exmor RS series products are no strangers to those who are familiar with the smartphone industry. From the original Sony Exmor R (back-illuminated CMOS) to the later Exmor RS (stacked CMOS), this series has become the choice of many mobile phone manufacturers for its excellent imaging performance. Following the previously popular IMX135 and IMX214, Sony launched a new generation of Exmor RS products - IMX230 in November last year.

Unlike previous generations of star products, the IMX230 has significantly increased the pixel value from 13 million to 21 million. In addition, the size of the CMOS has also increased from 1/3 inch to 1/2.4 inch, which is close to the level of a compact camera, making the image quality even better. Of course, the most important thing is that the IMX230 supports phase detection autofocus technology. I will analyze these selling points mentioned above in detail below.

Compared with the early back-illuminated CMOS, the stacked CMOS uses a chip with a signal processing circuit to replace the supporting substrate in the back-illuminated CMOS image sensor, and overlaps the pixel part of the back-illuminated CMOS element on the chip, thereby realizing the process of forming a large number of pixels on a smaller chip size. Since the pixel part and the circuit part are independent, the pixel part can be optimized for high image quality, and the circuit part can be optimized for high performance.

In layman's terms, stacked CMOS can be seen as a derivative and evolution of back-illuminated CMOS. By placing the circuit components below the photosensitive components, more space is freed up for the device, improving performance while reducing the size. The IMX230 mentioned in this article belongs to the latest generation of Sony stacked CMOS.

Support phase focus faster

The size of the photosensitive element is a hard indicator to measure the imaging level of a CMOS. Generally speaking, its imaging quality is proportional to the area of ​​the photosensitive element. Compared with the traditional 1/3.06-inch CMOS, the diagonal length of the IMX230 has increased from 5.867mm to 7.487mm. If the Pythagorean theorem is used to calculate, the area of ​​a 1/2.4-inch CMOS is about 1.64 times that of a 1/3-inch CMOS, which is a clear advantage. Although the CMOS area of ​​the IMX230, which is about 27mm2, is less than one-tenth of the CMOS of a traditional APS-C camera, within the scope of a smartphone, such an improvement can still have a significant impact on the output image quality.

As mentioned above, the biggest highlight of IMX230 is its support for phase detection autofocus. According to Sony's official introduction, IMX230 supports up to 192 autofocus points, so even when shooting high-speed moving objects, it is not easy to have the common ghosting in the past.

The full name of phase focus is Phase Detection Auto Focus. Its principle is to reserve some masked pixels on the photosensitive element specifically for phase detection. The focus offset value is determined by the distance between pixels and its changes to achieve accurate focus.

The masked pixel is composed of two pixels in pairs, and the two pixels are imaged separately through the microlens. The focusing system can determine whether the lens should be shifted forward or backward based on the position of the signal peak, so as to quickly and accurately focus. Compared with contrast focusing, phase focusing does not require repeated movement of the lens, the focusing stroke is much shorter, and the focusing process is refreshing and without hesitation.

In addition, IMX230 continues to support video HDR recording, but the resolution is increased to 4K (4096*2160). Maybe you usually use HDR mode to shoot more static images. In fact, HDR video recording plays a very powerful role in video shooting. Like static images, it can also adjust the light and dark contrast in high-contrast environments to show more details in the dark.

The cost is high and it will take some time for it to be popularized

The effective pixel of IMX230 is increased to 21 million, which means it can capture images with a resolution of up to 5344*4016, showing more details. Due to the large number of pixels and the limited CMOS area, the unit pixel size cannot be too large, only 1.12μm.

When it was released last November, Sony expected that IMX230 would be put into mass production in April 2015. In fact, Sony first applied this CMOS to the latest Z4 (Chinese version is called Z3+ Dual) in April this year, and LeEco's Le Max also occupied a place in IMX230 by "occupying the pit first and then planting vegetables" (releasing products first). The Honor 7, which was launched not long ago, became the latest product equipped with IMX230.

According to Sony's official introduction, the price of this IMX230 is 2100 yen (about 106 yuan). Judging from this price, IMX230 is destined to remain exclusive to flagship phones in the short term, and products priced at 1,000 yuan are not yet equipped with this CMOS on a large scale. According to our evaluation of Sony Z3+ Dual and Honor 7, the photo quality of these two phones equipped with IMX230 photosensitive elements is still satisfactory. It can be foreseen that as IMX230 is widely distributed, it is expected to become another star product after IMX135 and IMX214.

As a winner of Toutiao's Qingyun Plan and Baijiahao's Bai+ Plan, the 2019 Baidu Digital Author of the Year, the Baijiahao's Most Popular Author in the Technology Field, the 2019 Sogou Technology and Culture Author, and the 2021 Baijiahao Quarterly Influential Creator, he has won many awards, including the 2013 Sohu Best Industry Media Person, the 2015 China New Media Entrepreneurship Competition Beijing Third Place, the 2015 Guangmang Experience Award, the 2015 China New Media Entrepreneurship Competition Finals Third Place, and the 2018 Baidu Dynamic Annual Powerful Celebrity.