In many ambient light sensing applications, the sensor is placed behind a dark glass for aesthetic purposes. The material type and spectral transmission properties will determine the level of overall light transmission. In any application, the OPT4003-Q1 sensor area must be centered with respect to any window opening. These dimensions are described in Figure 4-1, with the channel 0 photodiode indicated with light gray and the channel 1 photodiode indicated with dark gray. Refer to Section 10 of the OPT4003-Q1 data sheet for complete package dimensions.

Figure 4-1 OPT4003-Q1 Sensor Position

Dark materials allow less light to illuminate the sensor, impeding accuracy. Choosing a material that is dark enough to optimize the balance between the aesthetics of the device and sensor performance is important.

In automotive applications that require light source detection the OPT4003-Q1, can be placed behind the windshield, in addition to dark cover glass.

Dark inks used on cover materials typically pass 2% to 20% of the light incident, reducing the amount of light hitting the sensor and reducing low light sensitivity of the sensor.

For example, if the ink transmits 2% of ambient light at 50 lux, the sensor can only see 1 lux. System resolution can be calculated using Equation 2, based on the transitivity of the cover material.

For more detailed information regarding proper window sizing and cover glass compensation, please refer to the Ambient Light Sensor Application Guide.