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. <EOS>