A new design based on a stacked n-i-p-n-i-p heterojunction is proposed for the Colour Laser Scanned Photodiode image sensor and compared with performance presented by a sensor whose capture element is based on a single p-i-n structure. Results show that the double structure presents a higher light-to-dark sensitivity. A black and white image is acquired with an improved resolution when compared with the single structure. The readout frequency is optimized showing that scans speeds up to 10(4) lines per second can be achieved without degradation in the resolution. A physical model is presented and supported by an electrical and a numerical simulation of the output characteristics of the sensor.