Color Sensor

1. What is the difference between ALS and color sensor?

ALS (Ambient Light sensor) is sensitive to visible light from 470nm to 670nm. The output is single channel and is proportional to the ambient light intensity.

Color Sensor senses the same range of visible light but there are 3 channels used to sense light – Blue, Green and Red channels. Capella’s CM33XX color sensor has peak wavelengths of 467nm, 530nm and 630nm corresponding to Blue, Green and Red channels. All channels have excellent Infrared rejection.

2. What does pulse density output of color sensor mean and what is the benefit?

Capella has an IP in Pulse Density Output for Color Sensor.

The output format is a fixed width high pulse and the frequency (Density) of output pulse is proportional to the light intensity. As the light power gets higher, the frequency of pulse gets higher as well.

For color sensor applications, pulse density output is beneficial in reducing the BOM cost and optical calibration time. For detailed information, please contact Capella Sales.

Proximity Sensor

1. A proximity sensor senses Infrared light from an IR LED . When operating in strong infrared light sources such as sunlight or incandescent light, will the sensing process be compromised?

Capella’s proximity sensor has a built-in IR LED driver to control the LED on/off. The internal DSP circuit has a background light (noise) cancellation process which avoids faulty proximity sensing under different light sources

2. What guidance is there for lens design for a ALS + Proximity sensor that needs to be hidden behind dark glass?

Customers can adopt the material with the below characteristics and keep coating surface on the bottom side:

(a) IR region (850nm) transmission need to over 50%

(b) Visible region (550nm) around 15%~20% is okay

Ambient Light Sensor

1. What are the differences between a Capella ALS and a traditional photodiode?

Capella’s light sensor uses a high sensitivity photodiode with a light spectral profile matching human eye response. The ALS has immunity to fluorescent light, excellent Infrared light rejection, a shutdown mode function, and a built-in thermal sensor to compensate over temperature.

2. What are the major design considerations for ALS?

Two of the most important factors are to account for transparency of lens cover and make sure the sensor is initially designed for a wide viewing angle. Capella offers support in mechanical design, testing the ALS in system and supporting application as it moves from design to production.


1. What is POF?

POF (Plastic Optical Fiber) or TOSLINK, Datalink is the most common format for digital audio cable to connect digital sources to digital receivers.

The POF uses a visible 650nm red light to transfer data from one device to another. A quick glance inside the cable indicates connectivity to the link---a red light seen by the human eye indicates the network is connected; on the other hand, no red light indicated, no connection.

2. What does Capella POF IC provide?

We offer both the transmitter and receiver IC
- Transmitter (Tx)→ CM3856A, CM3857 and CM3858
- Receiver (Rx) → CM3835, CM3837 and CM3838


1. What is encoder and channel?

An encoder is a sensor of mechanical motion. It translates motion (such as position, velocity, and acceleration) into electrical signals.

A channel is an electrical output signal from an encoder. Typical high performance incremental encoders have either two channels.

2. How to define resolution?

- LP (mm) = Lines per mm
- CPR = Count per revolution
- r =  Optical codewheel radius

UV Sensor

1. What benefits do Capella’s UV Sensors offer?

Capella’s UV Sensors (UVS) have excellent Ultraviolet Light sensing capability via Filtron™ technology. They can sense light in the UVA/UVB bandwidths tracking the amount of sunlight your body sees during the day, thus positively regulating one’s circadian rhythm. The sensor measures UV Index to alert us when to use protection against the sun. A shutdown function is available for system power savings.

2. What should be considered on UV sensor designs?

Lens cover design and lens material should be evaluated to make sure they can pass light in the UV spectrum. It is also important to have a mechanical design where the sensor has a wide viewing angle.