A laser detector comprising: a forward facing array of sensor elements, and a lens arrangement positioned in front of the sensor array; a computer processor arranged to receive image data from the sensor array and to determine from the received data the presence of light from a laser source, based at least in part on the brightness of pixels in the image data; characterised in that: the lens arrangement is positioned relative to the array of sensor elements such that any substantially point-like distal light sources where incoming light rays are substantially parallel give rise to a characteristic out of focus image that spans at least eight pixels in the plane of the array of sensor elements; the lens arrangement is arranged to provide an out of focus image at the sensor array from light sources at substantially optical infinity, and to provide an in-focus image at the sensor array from proximal light sources at a predetermined proximal distance or the lens arrangement is arranged to provide an out of focus image at the sensor array from light sources at optical infinity, and to provide an even more out of focus image at the sensor array from more proximal light sources; the computer processor is arranged to process the received image data to identify the characteristic out of focus image in the image data, and to disregard different images that are a different size and their associated light sources; and the forward facing array of sensor elements is provided as a bayer type sensor having different regions devoted to different wavebands, and the laser detector is arranged to measure the wavelength of the substantially point-like distal light source solely from inside the characteristic out of focus image. a forward facing array of sensor elements, and a lens arrangement positioned in front of the sensor array; a computer processor arranged to receive image data from the sensor array and to determine from the received data the presence of light from a laser source, based at least in part on the brightness of pixels in the image data; characterised in that: the lens arrangement is positioned relative to the array of sensor elements such that any substantially point-like distal light sources where incoming light rays are substantially parallel give rise to a characteristic out of focus image that spans at least eight pixels in the plane of the array of sensor elements; the lens arrangement is arranged to provide an out of focus image at the sensor array from light sources at substantially optical infinity, and to provide an in-focus image at the sensor array from proximal light sources at a predetermined proximal distance or the lens arrangement is arranged to provide an out of focus image at the sensor array from light sources at optical infinity, and to provide an even more out of focus image at the sensor array from more proximal light sources; the computer processor is arranged to process the received image data to identify the characteristic out of focus image in the image data, and to disregard different images that are a different size and their associated light sources; and the forward facing array of sensor elements is provided as a bayer type sensor having different regions devoted to different wavebands, and the laser detector is arranged to measure the wavelength of the substantially point-like distal light source solely from inside the characteristic out of focus image.