How does a Mouse know when you move it? || How Does a Computer Mouse Work?

Summary

This educational video delves into the intricate workings of a computer mouse, focusing on the image sensor technology that enables precise tracking. It explains how an infrared LED, lenses, and a 1600-pixel array capture surface texture, with the sensor taking 17,000 images per second to track mouse movement. The video also contrasts gaming mice with standard ones, highlighting differences in DPI, reporting rate, and frame rate. It touches on interpolation for higher DPI and the role of the digital signal processor in calculating movement. The script concludes with a teaser for a future video on scroll wheel technology.

Takeaways

• 🖱️ The modern computer mouse integrates 7 different technologies, showcasing a blend of sophisticated engineering.
• 🕵️‍♂️ The image sensor, a key component, uses an infrared LED, lenses, and an image pixel array to capture the texture of surfaces under the mouse.
• 🌆 The mouse doesn't capture color or design but instead detects the topographical and textural landscape of the surface due to the shallow angle of infrared light.
• 🔍 The image sensor focuses on a tiny area and takes up to 17,000 images per second to track mouse movement.
• ⏱️ The microchip compares sequential images taken 59 microseconds apart to calculate the mouse's movement in X and Y coordinates.
• 🧠 The digital signal processor (DSP) executes a cross-correlation algorithm to determine the change in position between images.
• 🎮 Gaming mice offer higher DPI (dots per inch) ranging from 12,000 to 25,000, providing greater precision and sensitivity compared to non-gaming mice.
• 📏 DPI is a measure of cursor movement per inch of mouse movement, with higher DPI indicating more units moved on the screen for the same physical distance.
• 🔄 Interpolation is used to increase DPI by subdividing each pixel into subpixels, improving the sensor's resolution without changing hardware.
• 🔋 Gaming mice report movement more frequently (1000 times per second) and have higher frame rates, which can enhance performance in fast-paced activities.
• 🔗 The video was sponsored by PCBWay, emphasizing the importance of printed circuit boards in device manufacturing and assembly.

Q & A

What is the primary function of the image acquisition system (IAS) in a computer mouse?

The image acquisition system (IAS) in a computer mouse is composed of an infrared LED, a pair of lenses, and an image pixel array. It captures the texture of the surface beneath the mouse by emitting infrared light, which reflects off the surface and is detected by the image sensor, allowing the mouse to track movement.

How does the image sensor in a computer mouse capture the texture of the surface?

The image sensor captures the texture of the surface by emitting infrared light at a shallow angle, which illuminates the ridges and valleys of the surface. The tops of the hills reflect the light and are detected, while the valleys remain dark, creating a topographically complex image.

Why do some computer mice struggle to work on glass surfaces?

Some computer mice struggle to work on glass surfaces because the surface needs to have imperfections for the infrared light to reflect and create a detectable pattern. A perfectly smooth glass surface may not provide enough texture for the mouse to accurately track movement.

How many pictures does the image sensor take per second, and what is the purpose of taking so many images?

The image sensor takes up to 17,000 pictures of the surface every second. This high frame rate allows the sensor to capture even the quickest movements, ensuring precise tracking of the mouse's position on the surface.

What is the role of the digital signal processor (DSP) in determining the mouse's movement?

The digital signal processor (DSP) executes an algorithm called cross-correlation to compare two images taken 59 microseconds apart. It calculates the difference in position between the images to determine the change in X and Y, which indicates how far and in what direction the mouse has moved.

How does the DPI (dots per inch) of a mouse relate to its image sensor and cross-correlation algorithm?

The DPI of a mouse is determined by the number of subdivisions of each pixel in the image sensor. Higher DPI values are achieved by subdividing each pixel into more subpixels using interpolation techniques, which allows for more precise tracking of movement.

What is the difference between bilinear and bicubic interpolation in the context of mouse DPI?

Bilinear interpolation involves drawing straight lines between whole integer pixels to create subpixels, while bicubic interpolation uses more complex calculations to create a smoother topography for the subpixels. Bicubic interpolation typically provides a higher quality image for determining mouse movement.

Why do gaming mice have higher DPI settings compared to non-gaming mice?

Gaming mice have higher DPI settings to provide greater precision and sensitivity, allowing for faster and more accurate cursor movements which are essential in gaming scenarios where quick reactions are often required.

How does the frame rate of a mouse affect its performance?

The frame rate, which is the number of pictures taken every second, affects the mouse's ability to track movement. A higher frame rate, like 17,000 frames per second, ensures that even quick movements are accurately captured, resulting in smoother and more responsive cursor control.

What is the significance of the reporting rate in a gaming mouse?

The reporting rate refers to how often the mouse sends movement data to the computer. Gaming mice typically have a reporting rate of 1000 times per second (1ms), which is faster than non-gaming mice, allowing for more immediate response times in gaming.

How does the image sensor adjust its frame rate based on mouse movement?

The image sensor adjusts its frame rate based on the speed of the mouse movement. When the mouse is stationary, the frame rate scales down to conserve battery life. When the mouse is in motion, especially at high speeds, the frame rate increases to capture the movement accurately.