The evolution of sensors in the past ten years of iPhone

Recently, I have watched all the iPhone conferences held by Apple in the past ten years, with only one purpose, which is to study the evolution of iPhone's use of sensors. The so-called sensor is a component that can sense the surrounding environment and output electrical signals. For example, a microphone is a sensor that can sense surrounding sounds, and a camera is a visual sensor.

People perceive the surrounding stimuli through ears, eyes, skin, nose, etc., and then make decisions. The same is true for smart devices. I think the reason why the iPhone is powerful, in addition to its powerful computing power and iOS operating system, is that it uses a variety of advanced sensors to collect surrounding data. Next, I will explain the sensors used in the iPhone in chronological order, and take you to appreciate Apple's black technology.

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1. iPhone 2G (2007)

• Multi-touch screen

In early 2007, Apple released its new product, the iPhone. Before that, the iPod was already very popular, and many people were imagining what Apple's mobile phone would look like. Some people photoshopped the iPod's touch wheel into an old-fashioned telephone dial. When the iPhone was actually shown to everyone, they were still shocked. This phone actually has no physical buttons!

Of course, there were smartphones without physical buttons before, but they needed a pen because they used a resistive screen, so sensitivity was a problem. The iPhone uses a capacitive screen, which is responsive and supports multi-touch, so you can operate it very accurately with ten fingers. Even after the product was released, many people still doubted whether typing would be too painful. Now if you look down at your phone, you will know that this is no longer a problem. The multi-touch screen gives the iPhone a sense of touch.

• Proximity sensor

On the front of the iPhone, there is a proximity sensor that uses infrared sensing to detect the distance between a person's face and the phone screen. If the face is very close, the screen will be turned off. This saves power and avoids misoperation caused by face touch.

• Ambient light sensor

There is also a light sensor on the front that can obtain the surrounding light intensity, so that the screen brightness can be adjusted intelligently.

• Accelerometer

The accelerometer is used to sense the movement of the mobile phone. Its principle is like putting an iron ball in a box. Due to the effect of gravity, if the direction of the box is rotated, the pressure received by the iron ball on each side will be different, so the direction of the box can be determined.

Based on the accelerometer, the iPhone can automatically display content in widescreen when in landscape orientation. The proximity sensor, light sensor and accelerometer made the iPhone far more intelligent than the semi-smartphones of the time, not to mention the feature phones.

• 2 megapixel camera

The first generation iPhone is equipped with a 2-megapixel camera, which is not high. The Nokia 7500 I bought in 2007 also had 2-megapixel. But the photo quality is not determined by only pixels.

Each pixel is like a pit, and the amount of light absorbed by each pit is different (I will explain this in more detail in the iPhone 5S section). Coupled with Apple's high-definition screen, the photos taken are even more beautiful.

• microphone

With a microphone, you can hear sounds, and the iPhone has ears.

• Moisture Sensor (not a real sensor)

Each generation of iPhone has a humidity sensor, which is mainly used to monitor whether the iPhone is soaked in water. It is just a humidity test paper. If it is soaked in water, it will turn red and the Apple store will refuse to repair it.

As pointed out by netizens, this thing is called an immersion indicator, hidden in the charging port, headphone jack, card slot and other places. It is not a standard sensor, but it can play a role in sensing the environment.

• 2G / Wi-Fi / Bluetooth

The first generation of iPhone only supports 2G signals, like mobile phone signals are electromagnetic waves. In fact, the light we see is also electromagnetic waves. Hearing this, liberal arts students may be dizzy. If you are interested, you can re-learn high school physics. My wife, who graduated from the Chinese Department, bought a set of high school physics textbooks online at the beginning of the year.

Different signals require different receivers for decoding operations. A 2G signal receiver is an "eye" that can sense 2G electromagnetic waves. With a Wi-Fi sensor, you can connect to Wi-Fi. Yes, Wi-Fi signals are also electromagnetic waves. Bluetooth is also a sensor that receives electromagnetic waves in a certain frequency band.

Many professionals or netizens do not agree to classify these signal receiving devices as sensors. They are just signal receiving devices and do not have a process to convert a physical quantity into photoelectric quantity.

I think it is these devices that allow mobile phones to "sense" these signals. The human body is surrounded by various wireless signals but cannot sense them. Don't take my classification as a professional division, just take it as a means to promote thinking.

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2. iPhone 3G (2008)

• 3G

The second generation of iPhone added support for 3G signals, which brought a significant leap in Internet access speed.

• GPS

With a GPS sensor, you can locate the current location of your phone through satellite signals. Similarly, professionals do not consider GPS to be a sensor.

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3. iPhone 3GS (2009)

• 3-megapixel camera

The third generation of iPhone upgraded the camera to 3 million pixels and added video recording function.

• Magnetic sensor (Compass)

With GPS, you can locate your location, but you cannot tell the direction. Only when you walk 20 meters in one direction with your phone can you estimate your direction through displacement, but this is still not accurate enough. In places where satellite signals are poor, the positioning deviation may be several hundred meters, and this estimated direction is completely unreliable.

It's different with a magnetic sensor, just like a mobile phone has a compass. When we open the map, we not only know the current location, but also the current orientation of our phone. We no longer have to look at the sun to determine the direction (this ancient technology, I find that many people around me cannot master it).

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4. iPhone 4 (2010)

• Gyroscope

You may have played with a spinning top or seen a unicycle electric balance car. Both of these things use a physical principle. A rotating object will remain stable along the axis. Even if a spinning top is hit, it will still shake a few times and return to a stable downward position. Another feature of the gyroscope is that it can calculate the rotational acceleration through the rotational displacement.

Although the first generation iPhone can sense the tilt of the phone through the accelerometer, it cannot calculate the rotation of the phone very well. Especially when playing some racing games, you cannot control the steering wheel sensitively by shaking the phone.

With the gyroscope, things are different. Jobs demonstrated a game of dismantling building blocks on the spot. By rotating the phone, you can dismantle the building blocks from different angles. Jobs also put these five smart sensors together at the end, which shows that he has a special liking for sensors.

It should be added here that the gyroscope used in the iPhone is not this kind of rotating wheel type mechanical gyroscope, but a micro-electromechanical structure (MEMS), which measures the angular velocity by the change in capacitance during rotation, and then cooperates with the accelerometer sensor to calculate the posture.

(PS: I originally thought that the balance of a bicycle also used the principle of a gyroscope, but later netizens pointed out that it was not the case. If you are interested, please see: How to explain the balance principle of a bicycle? - Physics)

• Internal Temperature Sensor

The iPhone 4 also has a temperature sensor, which is not used to measure the external temperature, but mainly to monitor whether the phone itself is overheating. When the phone is overheated, it will prompt to shut down for a while and then restart.

• 5-megapixel camera

The camera has been upgraded to 5 megapixels, and the photo effect is better. What I want to say here is that the iPhone's flash will decide how bright the flash should be based on the brightness of the surrounding environment, rather than treating everyone equally, to avoid the problem of overexposure.

• 0.3-megapixel front-facing camera

Finally, there is a front-facing camera so I can see the other person’s face.

• Dual microphones

There is another microphone next to the headphone jack on the top of the phone. What is it for? I will explain it later.

iPhone 4 was the last iPhone released by Steve Jobs himself, and he died a year later. At the intersection of technology and humanity, there is no one else. Luo Yonghao tried it three years ago, but he could only stand at the intersection of UI and jokes.

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5. iPhone 4S (2011)

• Bluetooth 4.0

The iPhone 4S is said to be one of the first phones to support Bluetooth 4.0. Compared with previous versions, Bluetooth 4.0 consumes less power, and you don't have to worry about wasting power even if Bluetooth is turned on by default. This is mainly paving the way for the Internet of Things era.

• 8-megapixel camera

The iPhone 4S camera has been upgraded to 8 megapixels and supports 1080P video recording. What impressed me most about this release is the photo response speed and the shortened waiting time.

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6. iPhone 5 (2012)

• 4G (LTE)

With the addition of a 4G signal receiver, the Internet speed is no different from using Wi-Fi.

• 1.2 megapixel front camera

The front camera of iPhone 5 has been upgraded to 1.2 megapixels.

• Three microphones

I asked several friends around me if they knew what the hole between the camera and flash on the back of the iPhone was for. None of them could answer. In fact, it is a microphone. It is generally known that there is a microphone next to the headphone jack on the lower side of the Home button, which is needed when making calls.

Why add a microphone next to the flash? The answer is to reduce noise. When we make a call, the sound will be transmitted to the microphone next to the headphone jack, but there may be noise around.

These noises will be transmitted to both microphones at the same time. Therefore, we take the sound received by the main microphone and filter out the sound of the microphone next to the flash, thus achieving the purpose of noise reduction and making the sound clearer.

One more thing, there is also a microphone hidden in the earpiece of the front earphone. That is to say, the iPhone 5 is equipped with three microphones, which are combined together to reduce noise on the one hand, and receive voice from multiple angles on the other hand, making the sound more realistic.

A few months ago, I found that the other party couldn't hear me when I was using my iPhone 6 Plus for WeChat video calls, but a few weeks ago I found that I could hear them when I plugged in headphones. But when I made calls normally, it was normal, which meant that my microphone was normal. I couldn't figure it out.

After iOS 10 was released a few days ago, I upgraded it and wanted to try the new Siri, but I found that Siri could not recognize my speech. So I looked up information online and gradually realized that Siri did not receive voice through the microphone next to the Home button, but used the hidden microphone inside the receiver. I went to the Apple store for testing and found that the hidden microphone was broken. The annoying thing is that this microphone is integrated with the screen. If I want to solve this problem, I have to spend 1,100 yuan to replace the screen. I thought about it and gave up.

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7. iPhone 5C/5S (2013)

• Fingerprint recognition (Touch ID)

iPhone 5S adds fingerprint recognition, so you don't need to enter a password to disable the screen saver. Fingerprint recognition is also a sensor that recognizes fingerprints.

• Coprocessor M7 (Motion coprocessor, not a sensor, but a processor dedicated to sensors)

As more and more sensors are added, the CPU resources are increasing and the power consumption is also increasing. Therefore, Apple launched the M7 coprocessor, which collects and processes the data of these motion-related sensors (including accelerometers, gyroscopes, and magnetic sensors) to reduce power consumption and allow the CPU to do other things.

M7 is not a sensor, but a device designed by Apple specifically for sensor information processing. I list it here mainly to emphasize the effort Apple has put into sensors.

• Camera with larger pixel size

Many people have a misunderstanding that the more pixels a camera has, the better. For example, they think a 12-megapixel camera is better than an 8-megapixel camera. In fact, it is not. It also depends on the light intensity and color richness that each pixel can accept.

The iPhone 5S uses a larger image sensor, but the pixels are still 8 million. The sensor width corresponding to each pixel is increased from 1.4 microns to 1.5 microns, which means the area has increased by 15%. This allows for better lighting for each pixel, thereby improving the quality of photos.

On the contrary, some mobile phone cameras have 13 million pixels, but they may only be 1.1 microns, so the lighting conditions are worse, and the quality of the photos taken is greatly reduced. So Apple says "Bigger Pixels = Better Pictures".

This generation also upgraded the flash to dual flash, one warm light and one cold light, which, combined with the light sensor (I am not sure whether it is the light sensor next to the front earpiece, or another one hidden in the main camera or flash), can produce light that matches the environment, so that the photos taken are more integrated. The flash itself is not a sensor, and it works better with the light sensor.

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8. iPhone 6/6 Plus (2014)

• Near Field Communication (NFC)

The iPhone 5S has fingerprint recognition, and the iPhone 6 has near-field communication (also an electromagnetic wave). The two combined together become Apple Pay. From then on, swiping a card becomes swiping a phone, and entering a password becomes swiping a fingerprint.

Although these technologies have existed before, Apple is good at integrating them into high-quality services. I have used them several times in Starbucks. Unfortunately, my credit card still has a password, and I have to enter the password again after swiping it. (It is said that the password is no longer required now. I will go to confirm it another day.)

• Barometer

With a barometer, you can measure altitude, and you can also measure how many flights of stairs you climbed. For outdoor enthusiasts like me, climbing to the top of a hill is a good way to see how high it is.

Some people may have a question. Didn't we learn in junior high school textbooks about the effect of air humidity on air pressure? Will the test error be greatly affected by different weather conditions? From the information I have collected so far, this effect is very small and can be ignored.

• Six-axis gyroscope

The gyroscope in the iPhone 6 series is six-axis, which is three more axes than the three-axis gyroscope used in the iPhone 4. The main reason is that a three-axis accelerometer has been added. Logically, there is no need for a dedicated acceleration sensor, and it can be two-in-one. But after someone disassembled the phone, they found that there is also a dedicated acceleration sensor. Why is that?

The answer is experience and power consumption. It takes time for acceleration to start. A dedicated acceleration sensor only takes 3 ms, while a six-axis gyroscope takes 30 ms. In addition, when measuring acceleration, the six-axis gyroscope consumes three times more power than an acceleration sensor.

Therefore, Apple only uses the accelerometer for applications such as horizontal screen and step counting, and uses the six-axis gyroscope for more sensitive scenes. Apple is really willing to work hard on the details of the design.

• Better image sensors

iPhone 6/6 Plus uses a new image sensor, which has better photo effects. For example, it uses a technology called Focus Pixels (phase detection autofocus), which can make the focusing speed faster. I don’t know the specific technical details, but it is said that it has been maturely applied in SLR cameras for a long time, but it is still rarely used in mobile phones.

iPhone 6 Plus also adds optical image stabilization, which makes the photos clearer even when the camera is slightly shaken. The basic principle is this: when a person takes a photo and the camera shakes, the same object is projected onto different pixels of the image sensor.

Then the gyroscope detects the acceleration of the shaking, calculates the displacement, and moves the camera in the opposite direction to remove the impact of the shaking. Of course, in order to achieve this, the iPhone 6 Plus camera can not only be extended and retracted forward and backward, but also move up and down and left and right.

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9. iPhone 6S/6S Plus (2015)

• Pressure sensor (3D Touch)

iPhone 6S adds a screen pressure sensor that can detect the pressure, which allows new interactions. The screen can sense the pressure of the hand, but people don't feel that the screen is actually pressed.

In order to give people feedback, a device called TAPTIC Engine is added inside, which will produce vibrations according to the pressure, so that people can feel the pressure. But at present, the application of this function is not particularly widespread.

• 5-megapixel front-facing camera

The front camera is 5 megapixels.

• 12-megapixel camera

The rear camera has been upgraded to 12 million pixels with better light perception.

At the beginning of this year, Apple also released the iPhone SE, mainly to cater to customers who like small screens. In appearance, it is a replica of the iPhone 5S, and its configuration is closer to the iPhone 6S, such as the camera is 12 million pixels, but it does not have the 3D Touch function. There is not much to say, so just skip it.

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10. iPhone 7/7 Plus (2016)

• Non-mechanical Home button

The iPhone's Home button has been changed to a non-mechanical press-type one. If you can't feel anything when you press it, isn't that frustrating? So Apple enlarged the TAPTIC Engine vibrator used in implementing 3D Touch, so that it vibrates when you press it, giving you the illusion that the button is pressed.

With this method, firstly, it is not easy to be damaged (some people worry that even if the buttons are not broken, will the vibrator be more likely to be broken?), secondly, it is more waterproof, and thirdly, when playing games, you can use vibration feedback, just imagine a vibrating handle.

• 7-megapixel front camera

The front camera has been upgraded to 7 megapixels.

• Better cameras

With a faster image sensor, taking photos is faster. And the iPhone 7 also adds optical image stabilization, which is only available in the Plus series.

• Flicker sensor

The electric lights we usually use are all artificial lights with alternating current. The light looks stable, but it is actually flickering. When taking pictures, because the image sensor collects images row by row, the artificial light collected in different rows may have different effects, resulting in uneven colors in the photos.

So Apple added a flicker sensor to continuously collect light conditions so that corrections can be made during image processing. The flicker sensor should be a chip placed together with the image sensor, and the light should be obtained through the lens, which remains to be confirmed.

• Dual cameras

The iPhone 7 Plus uses a dual camera, one wide-angle and one telephoto, which can meet two needs and can also take macro photos. It is this dual camera that attracted me and I decided to change my phone.

Having written this, I find that the camera accounts for a very large proportion of the entire content, which shows the effort Apple has put into the camera.

Through the above review, we can see that Apple is using sensors more and more widely. In fact, not only Apple, but other companies are also using more and more sensors. With various sensors, various data can be collected, and with the addition of big data analysis technology, more and more value can be mined. I think that in the future, all devices that are powered on will have sensors, and sensors will generate a lot of data. It is based on this consideration that I named my current startup Sensors Data. I think the future is the era of sensors.

References:

• Apple press conferences over the years.

• Which iPhone do you love? Cook's iPhone 7 is on the way Which iPhone do you love?

• Accelerometer Principle: Accelerometer Principle - decemberd's column

• Accelerometers and Gyroscopes: Accelerometers and Gyroscopes

• List of sensors on the iPhone

• The Senors That Make the iPhone So Cool

• Common sensors for iOS devices: Common sensors for iOS devices

• iPhone 6 design secrets: iPhone 6 design secrets: InvenSense and Bosch accelerometers

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