A method for determining a distance to a target object includes transmitting light pulses to illuminate the target object and sensing, in a first region of a light-sensitive pixel array, light provided from an optical feedback device that receives a portion of the transmitted light pulses. The feedback optical device includes a preset reference depth. The method includes calibrating time-of-flight (TOF) depth measurement reference information based on the sensed light in the first region of the pixel array. The method further includes sensing, in a second region of the light-sensitive pixel array, light reflected from the target object from the transmitted light pulses. The distance of the target object is determined based on the sensed reflected light and the calibrated TOF measurement reference information.