Capacitance Technology

Film that conveys my feeling merely by touch It’s not magic, It’s technology.

Alps Electric Technology: Answering needs of
people wanting to use digital equipment comfortably.

It’s all about "People Comfort" so human factors are our starting point.

In terms of our relationship with electricity, we humans are classed as "conductors." That is to say electricity passes through us, as we all remember being taught in our science classes. However, our bodies also generate electricity (*1). Did you know that current actually flows through us?
There is a connection between the electricity generated by the human body and one of the mobile society’s technologies.

(*1) Electricity generation - straight from the heart

In 1903, the Dutch physiologist Willem Einthoven used a machine to measure the heart’s electricity. As this machine proved to be the forerunner of the electrocardiogram used in medical examinations today, Einthoven is known as the father of the electrocardiogram and was awarded the Nobel Prize.

Assignment:combine lightness and slimness with high performance

Information input and output devices are indispensable when using a personal computer (PC). Typical information input devices include the keyboard, all of the keys and the mouse; the typical output device is the monitor. As market needs changed from large desktop PCs to notebook PCs, a lot of consideration was given to how space-consuming input and output devices can be integrated and made portable.

Many of the hurdles that had to be overcome in the development of notebook PCs involved a pointing device to support mouse operations. Even the functions of the on-screen cursor and icons, which are necessary to give the computer a personal feel, were a major aspect in making computers user-friendly. These needs were brilliantly met by the development of the touchpad or GlidePoint™(to give it its Alps Electric product name).

GlidePoint™ is a pointing device that synchronizes the tracing of a finger over a film with the movement of a cursor on a screen. Users operate the cursor simply by freely moving their fingertips; the operating feel of GlidePoint™ has received widespread acclaim. Because of its superior lightness, together with the slim and compact construction that its sheet-structure provides, GlidePoint™ has become an indispensable pointing device for notebook PCs.

Electrical energy flows from fingers

At the core of GlidePoint™ is capacitance sensing technology. Capacitance shows how much electrical energy is stored by a conductor (*2). Humans have dielectric properties, which means that we store rather than conduct direct current electricity. Thus when a person’s finger comes into contact with GlidePoint™, electrical energy flows from that person and the capacitance inside GlidePoint™ changes. Capacitance sensing technology uses this change in capacitance to detect the position and movement of the finger.

Electrical energy flows from fingers

Let’s see how GlidePoint™ works. Firstly, a sensor serves to detect finger movement. The sensor section is a grid structure made up of 16 X and 12 Y electrodes, between which electrical energy is stored. When not in operation, two electrodes form a stable electrical field. However, when a human finger approaches, this acts as an earth and changes the electrical field. The electrostatic capacitance value falls in the section that the finger touches, thanks to the phenomenon of electricity generation caused by human conductivity (*3). The X and Y electrodes can each detect 128 levels of change in electrostatic capacitance, so strong pressure is not necessary for the touch of a finger to be detected. Next, the coordinate detector senses the approach of a finger. The coordinate detector section scans the X and Y electrodes at a rate of 100 cycles per minute, instantly detect any finger movement, thereby realizing smooth operability.

Pointing devices which operate using the capacitance method can be operated with the merest touch and therefore do not put pressure on the operating surface. For this reason, there is almost no qualitative deterioration in the operation section, and high reliability is assured. Thanks to Alps Electric’s proprietary technologies, it is now also possible to laminate the printing of a capacitance sensor on film, achieving an even slimmer format.

Using this film’s special characteristics, Alps Electric’s pointing devices based on the capacitance method can also be produced in various shapes and sizes. There is absolutely no restriction on the shape of the device on which they can be mounted. We are currently exploiting the electrical characteristics of capacitance, and can envisage its uses branching out from the field of input devices for notebook PCs to different kinds of devices. Mobile telephones are one example. Already mobile phones have been developed with a keypad for smooth handwritten inputs (for China) or for viewing an Internet site clearly. Apart from this, we are currently planning to widen the technology’s application to encompass slim and compact-format portable devices, personal AV devices and multifunctional remote controls for digital consumer electronics.

(*2) Capacitance and the knight

The international unit of capacitance is the farad (symbol "F"), named in honor of the British physicist, Michael Faraday. Faraday was apprenticed to a bookbinder at the age of 13, but at age 22 he was appointed chemical assistant at the Royal Institution. In a stunning career, he went on to discover, among other things, the principles of electrolysis and of electromagnetic induction. Faraday declined a knighthood and all other honors, being known throughout his life as plain Michael Faraday and for his commitment to his research.

(*3) A little bit of you and me

When objects move, friction occurs between them and sometimes between the objects and the air. This friction causes a positive [+] or negative [-] bias in the electrical polarity of the electrons inside the object. Whether the bias is [+] or [-] differs depending on the object. We humans are inclined to the [+] side, and because of this we absorb [-] particles from other objects. By the way, the bioelectric current that runs through our bodies is around 200 microamperes, which is almost too weak to detect.

Taking "People Comfort" into consideration technology is advancing.

"The human machine interface" is one of the R&D themes at Alps Electric. Realizing the application of capacitance control technology in pointing devices is one example. Focusing on the dielectric qualities of the human body is leading to advanced technologies, and these have led to the development of new input devices.
Technology provides the idea, users provide the inspiration.
Taking this two-pronged approach makes full use of both to create innovative input devices.

Which products will be next to showcase the human skills and characteristics that inspired them? From Alps Electric to the mobile society: new products which generate electricity from a surprising source. "The human-machine interface" is Alps Electric’s goal and dream.