Dual-band infra-red vision system for motor-vehicles

Abstract: An infrared vision system for motor vehicles comprises a device (8) for detecting infrared radiation, which is designed to detect both infrared radiation in a first wave band, which corresponds to the radiation spontaneously emitted by the objects making up the scene in front of the motor vehicle, and infrared radiation in a second wave band, which is in part emitted spontaneously by the objects of the scene and in part is emitted by a source (5) of infrared radiation which forms part of the vision system (1) and is reflected by the objects in front of the vehicle towards the said detecting device (8).

Description: The present invention relates to infrared vision systems for motor vehicles, of the type comprising an infrared-radiation detecting device designed to be mounted on the front of a motor vehicle, the device including infrared sensor means designed to emit electrical signals according to the infrared radiation detected, optical imaging means for focusing the infrared image of the scene in front of the vehicle on said sensor means, electronic means for processing the signals issued by the sensor means, and image-displaying means controlled by said electronic means. The known infrared vision systems that have so far been produced exploit infrared radiation in a wave band ranging from 8 to 14 micron (longwave window - LW), which is emitted spontaneously to a variable extent by all the objects of the scene in front of the motor vehicle. These systems do not enable optimal results to be achieved, especially in particular conditions, such as in the presence of fog. An infrared vision system according to the preamble of claim 1 is known from FR-A-2 730 035. The purpose of the present invention is to propose a new infrared vision system for motor vehicles that enables improvement of night vision in all conditions, and in particular in the presence of thick fog. In order to achieve the above purpose, the subject of the invention is a vision system of the type specified above, characterized in that the aforesaid optical imaging means are designed to focus both infrared radiation in a first wave band, corresponding to the radiation spontaneously emitted by the objects of the scene in front of the motor vehicle, and infrared radiation in a second wave band, which is in part emitted spontaneously by the objects of the scene, and in part is emitted by a source of infrared radiation which forms part of the vision system and is reflected by the objects in front of the vehicle towards said detecting device. As has already been mentioned, the radiation emitted spontaneously by the scene falls within a wavelength range of between 8 and 14 micron (longwave window - LW). In a preferred embodiment of the invention, the above-mentioned infrared-radiation source forming part of the system is designed to emit radiation in a wave band of between 3 and 5 micron (midwave window - MW). This radiation is reflected by the objects of the scene, and is then detected by the sensor means forming part of the system according to the invention. Again according to the invention, the aforesaid optical imaging means comprise two optical imaging devices, which are combined in such a way as to minimize dispersion between the two aforesaid wave bands, and a discriminator designed to send to the sensor means alternately the radiation in the first band and the radiation in the second band (for example, a discriminator of a rotary type). In a preferred embodiment, the above-mentioned sensor means consist of a matrix of non-cooled thermal sensors, of a type chosen from among pyro-electric sensors, resistive bolometers, ferro-electric bolometers, and thermo-electric sensors of a conventional type. Again in the case of the preferred embodiment, the said infrared-radiation source consists of a headlight of the motor vehicle which has a front element that is at least in part transparent to infrared radiation. In this case, the detecting device of the vision system according to the invention is built into the said headlight of the motor vehicle. The control electronics forming part of the system according to the invention makes it possible to read, interpret and superimpose the infrared images in the two bands acquired by the sensors, so presenting a single infrared image of the scene on the display means at output. The main advantage of the system according to the invention is that it enables simultaneous exploitation of the greater intensity of the IR image in the 8-14 micron LW window and the greater contrast of the IR image in the 3-4 micron MW window in the temperature range of interest. Further characteristics and advantages of the invention will emerge from the ensuing description with reference to the attached drawings, which are provided purely as a non-limiting example and in which: Figure 1 is a cross-sectional schematic view of a vision system according to the invention; Figure 2 is a front view of a rotary discriminator forming part of the system of Figure 1; and Figure 3 illustrates a variant of Figure 2. In Figure 1, the reference number 1 designates, as a whole, a motor-vehicle headlight comprising a rigid casing 2 inside which is set a headlight 3 including a parabolic dish 4 associated to a lamp 5. The reference number 6 designates the transparent front element of the headlight 3, which presents, in the case of the example illustrated, peripheral windows 7 that are transparent to infrared radiation. The lamp 5 is chosen so as to emit infrared radiation in a wave band of between 3 and 5 micron. The body 2 of the headlight 1 also includes an infrared-radiation detecting device 8 comprising infrared sensor means 9 consisting of a matrix of non-cooled thermal sensors, for example pyro-electric sensors or resistive bolometers, or ferro-electric bolometers, or thermoelectric sensors of a conventional type, which are designed to send electrical signals according to the infrared image detected to a processing electronic control unit 10. The detecting device 8 comprises an optical imaging system 11 which is designed to focus on the sensors 9 both the infrared image in the 3-5 micron wave band, which is reflected by the objects of the scene in front of the vehicle, and the infrared radiation in the 8-14 micron wave band, which is emitted spontaneously by the objects of the scene. The detecting device 8 has, at the front, a window 13 which is transparent to infrared radiation. Between the optical imaging system 11 and the matrix of sensors 9 is set a rotary optical discriminator 14, of which Figure 2 and 3 illustrate two possible embodiments. In both cases, the said optical discriminator 14 consists of a disc having sectors A that are transparent to infrared radiation of between 8 and 14 micron, sectors B that are transparent to infrared radiation of between 3 and 5 micron, and opaque sectors C that clearly divide the sectors A from the sectors B. The rotary discriminator 14 is used to send alternately the 8-14 micron infrared radiation and the 3-5 micron infrared radiation to the sensor means 9. The electronic control unit 10 is designed to read, interpret and superimpose the infrared images in the two bands acquired by the sensors, presenting at output, on a display 15 provided on the motor vehicle dashboard or on the windscreen itself, according to a HEAD-UP type technology, a single infrared image of the scene. As has already been mentioned, the main advantage of the device lies in the fact that it enables simultaneous exploitation of the greater intensity of the IR image in the 8-14 micron band and the greater contrast of the IR image in the 3-5 micron band. The source of 3-5 micron IR radiation could also be a dedicated source, distinct from the vehicle headlight. Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to what is herein described and illustrated purely for the purpose of providing an example, without thereby departing from the scope of the present invention as defined by the appended claims.

Claims: An infrared vision system for motor vehicles, comprising a source (5) of infrared radiation and an infrared-radiation detecting device (8) designed to be mounted on the front of a motor vehicle, the device including infrared sensor means (9) designed to emit electrical signals according to the infrared radiation detected, optical imaging means (11) for focusing the infrared image of the scene in front of the vehicle on said sensor means (9), electronic means (10) for processing the signals issued by the sensor means (9), and image-displaying means (15) controlled by said electronic means (10), characterized in that said optical imaging means (11) are designed to focus both infrared radiation in a first wave band, corresponding to the radiation spontaneously emitted by the objects of the scene in front of the motor vehicle, and infrared radiation in a second wave band, which is in part emitted spontaneously by the objects of the scene, and in part is emitted by the source (5) of infrared radiation which forms part of said vision system (1) and is reflected by the objects in front of the vehicle towards said detecting device (8). A vision system according to Claim 1, characterized in that the optical imaging means (11) comprise two optical imaging devices, which are combined in such a way as to minimize dispersion between the two aforesaid wave bands, and a rotary discriminator (14) designed to send to the sensor means (9) alternately the radiation in the first band and the radiation in the second band. A vision system according to Claim 2, characterized in that the sensor means (9) consist of a matrix of non-cooled thermal sensors, of a type chosen from among pyro-electric sensors, resistive bolometers, ferro-electric bolometers, and thermo-electric sensors of a conventional type. A vision system according to Claim 1, characterized in that said first band includes wavelengths ranging from 8 to 14 micron. A vision system according to Claim 1, characterized in that said second band includes wavelengths ranging from 3 to 5 micron. A vision system according to Claim 1, characterized in that said infrared-radiation source (5) consists of a headlight (3) of the motor vehicle, which has a front element (6), at least part (7) of which is transparent to said infrared radiation. A vision system according to Claim 1, characterized in that the control electronics forming part of the system according to the invention makes it possible to read, interpret and superimpose the infrared images in the two bands acquired by the sensors, so presenting a single infrared image of the scene on the display means at output.

Inventors: BIGLIATI CLAUDIA, LAMBERTINI VITO, PERLO PIERO, REPETTO PIERMARIO, SINESI SABINO, BIGLIATI, CLAUDIA, LAMBERTINI, VITO, PERLO, PIERO, REPETTO, PIERMARIO, SINESI, SABINO
Applicants: FIAT RICERCHE, C.R.F. SOCIETA CONSORTILE PER AZIONI
Application year: 2000
Main classification: B60Q1
IPC codes: B60Q1