An imaging device comprising an image sensor, an imaging lens, an infrared light source to illuminate a scene, and an infrared autofocus system for providing an autofocus function, wherein the image sensor comprises an array of sensor pixels each arranged as dual pixel comprising two separate pixel sensors per dual pixel to record the image data as a sum signal from both pixel sensors and providing infrared data as individual signals from each of the two pixel sensors for phase contrast autofocusing, wherein an infrared filter arranged between an aperture of the imaging device and an imaging sensor and is adapted to locally transmit only a portion of the infrared light to the imaging sensor by comprising at least one first area arranged as infrared blocking area and at least one second area arranged as infrared bandpass area. The invention further relates to a method to automatically focusing this device.