Infrared sensor device with temperature correction function

• US 5,994,701 A
• Filed: 10/14/1997
• Issued: 11/30/1999
• Est. Priority Date: 10/15/1996
• Status: Expired due to Term

• Current Assignee: Nippon Avionics Company Limited (NEC Corporation)
• Original Assignee: Nippon Avionics Company Limited (NEC Corporation)
• Inventors: Sema, Akira, Tsuchimoto, Kohzou
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Israel, Andrew
• Application Number:
  US08/949,719
• Time in Patent Office: 777 Days
• Field of Search: 250/351, 250/252.1, 374/120, 374/121, 374/123, 374/124, 374/130
• US Class Current: 250/351
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01J 5/064 Ambient temperature sensor; Housing temperature sensor; Constructional details thereof
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0804 Shutters
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01J 5/53 Reference sources, e.g. standard lamps; Black bodies
• CPC Class Codes: G01J 5/70 Passive compensation of pyrometer measurements, e.g. using ambient temperature sensing or sensing of temperature within housing
• CPC Class Codes: G01J 5/80 Calibration using comparison with reference sources G01J5/52
• CPC Class Codes: H04N 23/23 from thermal infrared radiation
• CPC Class Codes: H04N 23/81 for suppressing or minimising disturbance in the image signal generation
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

A shutter 3 which can be momentarily held open and immediately closed, is disposed adjacent to an aperture stop 4 in an optical system, and a temperature sensor 5 is provided for measuring the temperature of the shutter 3. The blades of the shutter 3 can be utilized as a reference heat source. With the shutter 3 disposed adjacent to the aperture stop 4, the optical equivalence in the case when a reference heat source is inserted and in the other case, is not spoiled. A shutter 202 which can be readily momentarily held open and immediately closed under control of a shutter controller 203, is disposed at the optical pupil position of a combination lens 201. When the shutter 202 is closed, thermal image data is stored in a shading memory 208. The shading data stored in the shading memory 8 is subtracted for each image element in a subtracter 207 from thermal image data, which is obtained by picking up external infrared image in the open state of the shutter, and the resultant difference data is outputted to a frame memory 209.

Claims

1. An infrared sensor device with temperature correction function comprising:

a two-dimensional infrared sensor for producing a thermal image signal corresponding to an infrared image of an object under measurement which is incident therein through an optical system;

a shutter disposed at a position in the optical system adjacent to or at an aperture stop in the optical system;

a temperature correction means for correcting an output of the infrared sensor to obtain a temperature of the object under measurement by producing as a reference output an output from the infrared sensor when the shutter is in a closed state and removing output components of the infrared sensor from objects, including the optical system, other than the object under measurement on the basis of an output of the infrared sensor when the shutter is in an opened state; and

a temperature sensor for detecting the temperature of the shutter.

2. The infrared sensor device with temperature correction function as set forth in claim 1, wherein the reference output is obtained by interpolation of data which is previously obtained at a plurality of dispersed temperatures of the shutter.

3. A temperature correction method of an infrared sensor device comprising the steps of:

producing a thermal image signal corresponding to an infrared image of an object under measurement which is incident on a two-dimensional infrared sensor through an optical system;

detecting a temperature of a shutter disposed at a position adjacent to or at an aperture stop in the optical system;

correcting an output of the infrared sensor to obtain a temperature of the object under measurement by producing as a reference output an output from the infrared sensor when the shutter is in a closed state; and

removing output components of the infrared sensor from objects, including the optical system, other than the object under measurement on the basis of an output of the infrared sensor when the shutter is in an opened state.

4. In a method of infrared thermography using an infrared sensor, an optical system for projecting an infrared image of an object under measurement on the infrared sensor, the optical system including a shutter and an aperture stop, the shutter being disposed adjacent to or at the aperture stop, a temperature sensor for detecting the temperature of the shutter, a signal processing unit for processing the output of the infrared sensor to generate a thermal image signal of the object under measurement, and a display for displaying the thermal image of the object under measurement, an infrared sensor temperature correction method for correcting the infrared sensor output such that the temperature represented thereby approaches the temperature of the object under measurement, the infrared sensor temperature correction method comprising:

comparing the output Q_R of the infrared sensor, the output Q_R being obtained when infrared rays emitted from a reference heat source at a known temperature are led to the infrared sensor in lieu of infrared rays emitted from the object under measurement, and the output Q_W being of the infrared sensor, the output Q_W being obtained when infrared rays from the object under measurement are led through the optical system to the infrared sensor, thereby removing an output component Q_E of the infrared sensor, the output component Q_E being attributable to infrared rays from objects other than the object under measurement, to obtain an output a of the infrared sensor, the output a being attributable to sole infrared rays emitted from the object under measurement, wherein;

the shutter serves as the reference heat source when it is in the closed state and the known temperature of the reference heat source is determined from the output of the temperature sensor.

5. An infrared thermographic system comprising a two-dimensional infrared sensor, an optical system for projecting an infrared image of an object under measurement on the two-dimensional infrared sensor, a signal processing unit for processing the output of the two-dimensional sensor to generate a thermal image signal of the object under measurement, and a display for displaying the thermal image of the object under measurement by receiving the thermal image signal, wherein:

the optical system includes a shutter for opening and closing its optical path, a temperature sensor for measuring the temperature of the shutter, and an aperture stop;

the infrared thermographic system further comprising a first and a second image memory, a control unit for controlling the opening and closing of the shutter and causing outputs QW and QE from the two-dimensional infrared sensor when the shutter is held open and closed, respectively, to be stored in the respective first and second image memories, and a computing unit for computing the difference Q_D between the two-dimensional infrared sensor outputs Q_W and Q_E read out from the first and second image memories and also computing the output a of the two-dimensional image sensor attributable to sole infrared rays emitted from the object under measurement, the computing unit computing an output a'"'"' of the two-dimensional infrared sensor according to the output of the temperature sensor, and by adding the output a'"'"' to the difference Q_D.

6. The infrared thermographic system according to claim 5, which further comprises storage means for storing a table showing the correspondence relation between the shutter temperature and the output Q_R of the two-dimensional infrared sensor when the two-dimensional infrared sensor receives infrared rays emitted from the shutter in the closed state thereof, the output Q_R being obtained at a plurality of dispersed temperatures of the shutter and in which:

the computing unit computes the output a'"'"' by an interpolation method, in which the table is referred to at each shutter temperature determined on the basis of the output of the temperature sensor.

7. An infrared sensor device with temperature correction function comprising:

a combination lens including a shutter for forming an infrared image;

a shutter controller for controlling the opening and closing of the shutter;

a two-dimensional infrared sensor for focusing an infrared image thereon through the combination lens;

an A/D converter for converting an analog electric signal outputted for each image element by image element scanning of the two-dimensional infrared sensor into a digital signal;

a subtracter for subtracting the output signal of the A/D converted inputted to one input terminal and a signal inputted to the other input terminal from each other;

a shading memory for storing one frame of the output of the A/D converter in the closed state of the shutter, the stored signal being read out in the subsequent open state of the shutter from the shading memory with image element position coincidence with the signal inputted to one input terminal of the subtracter and inputted to the other input terminal thereof; and

a frame memory for storing the output of the subtracter in units of frames.

8. An infrared sensor device with temperature correction function comprising:

an optical system;

a shutter means provided at a position adjacent an aperture stop in the optical system;

a two-dimensional infrared sensor for producing an infrared image thereon through the optical system;

memory means for storing one frame of the output of the two-dimensional infrared sensor in the closed state of the shutter, the stored signal being read out in the subsequent open state of the shutter; and

a subtracter for subtracting the read out signal form the memory means from the corresponding output signal of the respective image elements obtained by the two-dimensional infrared sensor, thereby removing a shading of temperature gradient caused by stray light in a casing.

9. An infrared sensor device with temperature correction function as set forth in claim 8, wherein the infrared sensor device is a non-cooled two-dimensional infrared sensor.