JPH06273506A - Target detector - Google Patents

Abstract

PURPOSE:To make it possible to determine a target by the difference of luminance of the image of an object due to the difference of detected wavelength band using a plurality of infrared image parts having wavelength bands limited by infrared filters. CONSTITUTION:Infrared ray focused through infrared lenses 1a, 1b passes through first and second infrared filters 2a, 2b having different transmission wavelength bands and impinges on two-dimensional infrared detectors at first and second infrared imaging sections 3a, 3b then outputted in the form of an infrared image. Images at the imaging sections 3a, 3b are synchronized by a synchronization signal generator 7. First and second target detecting sections 4a, 4b output target candidates of two images having different wavelength bands. A target deciding section 5 compares image luminance of target candidate between respective images and decides a target and then presents a target data at a display section 6. This constitution reduces possibility of detecting the background erroneously as a target.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a target detecting device which is mounted on, for example, an aircraft and detects a high temperature target such as a missile fired toward itself.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a conventional target detecting apparatus. In the figure, 1 is an infrared lens, 3a is an infrared imaging unit, 4a is a target detection processing unit, and 6 is a display unit.

Next, the operation will be described. The infrared light imaged by the infrared lens 1 enters the two-dimensional infrared detector of the infrared imaging unit 3a and is output as an infrared image. The output infrared image is subjected to binarization processing in the target detection processing unit 4a to select a target candidate, and with respect to the selected candidate, characteristic amount measurement such as image position, image brightness, and area is performed. The target candidate is narrowed down, the target is determined by looking at the reproducibility of the target candidate in the images of several frames that are temporally consecutive, and the target data is output to the display unit 6.

[0004]

Since the conventional target detecting device is constructed by one infrared image pickup unit as described above,
A high-brightness background object (for example, an object that reflects sunlight) may be erroneously detected as a target. This is because, as shown in FIG. 6, the infrared imaging unit 3a is incident without distinction between a high-intensity background object and a target, and the brightness proportional to the energy is output as an infrared image. This is because the processing unit 4c uses the binarization process as an object having an object having a prescribed image brightness or higher.

The present invention has been made to solve the above problems. In addition to the above-described target detection method, the brightness of the target image by two infrared image pickup units having different detection wavelength bands can be adjusted. An object of the present invention is to obtain a target detection device that can perform a target determination process focusing on the difference.

[0006]

A target detecting apparatus according to the present invention detects image brightness of an object to be imaged by using two infrared image pickup units having different wavelength bands whose detection wavelength bands are limited by an infrared filter. By utilizing the fact that it differs depending on the wavelength band, a process for discriminating between the target and other objects is added.

[0007]

The target detecting apparatus according to the present invention uses two infrared imaging units having different wavelength bands, a target detecting processing section, and a target discriminating processing section, and thus, in addition to the target detecting method similar to that of the conventional target detecting apparatus. , Target discrimination is performed based on the difference in image brightness of the object to be captured due to the difference in detection wavelength band.

[0008]

【Example】

Embodiment 1 FIG. 1 is a block diagram showing an embodiment of the present invention.
In the figure, 1 and 6 are the same as the conventional device. Reference numerals 2a and 2b are first and second infrared filters having different transmission wavelength bands, and 3a and 3b are first and second infrared imaging units 4a, 3a and 3b which synchronize the images by a synchronization signal generator 7. Reference numeral 4b denotes first and second target detection processing units that output respective target candidates of images having different wavelength bands. Reference numeral 5 denotes the image brightness of the target candidates output from the respective images by the target detection processing units 4a and 4b. It is a target determination processing unit that determines a target by comparing differences.

Next, the outline of the target determination process will be described. It is known from Planck's law that an object emits infrared rays according to the temperature of the object itself. The radiation radiant emittance spectrum W of an object having a temperature T [K] and a wavelength λ [μm] is It is represented by.

[0010]

[Equation 1]

Here, the ratio k of the radiant emittance spectra for _two different wavelengths (λ ₁ , λ ₂ ) is

[0012]

[Equation 2]

[0013] On the other hand, k is image brightness N ₁ and N _{2 at} wavelengths λ ₁ and λ ₂ , spectral sensitivities G ₁ and G _{2 of the} infrared imaging unit, spectral transmittances τ ₁ and τ _{2 of} the atmosphere, and emissivity of the object ( The reflectance is calculated from η ₁ and η ₂ by the following formula.

[0014]

[Equation 3]

The spectral transmittance of the atmosphere changes depending on the weather conditions, and the emissivity (reflectance) of the imaged object varies depending on the imaged object, but is in the 2 μm band (2 to 2.2 μm) and the 4 μm band (3.
8 to 4 μm) does not change much, so approximately

[0016]

[Equation 4]

Considering the above, the value of k can be calculated from the image brightness in two wavelength bands.

The detection wavelength band of the two infrared imaging units is 2 μm
Assuming the band (λ ₁ ) and the 4 μm band (λ ₂ ), k and temperature T
2 is as shown in FIG. In the figure, assuming that the target temperature is 900 K to 3000 K, the value of k will be 0.4 to 7.4. It is unlikely that there will be objects over 900K on the ground. Further, the value of k is about 11.3 because the object reflected by sunlight corresponds to the temperature of the sun of 6000K. As described above, it is possible to discriminate between the target and other objects based on the value of k. It is possible to distinguish between the target and the background by setting the range of the value of k depending on the target in consideration of the error in the result of FIG.

Embodiment 2 FIG. 3 is a block diagram showing another embodiment of the present invention. In the figure, 4a is a target detection processing unit in which a target detection processing unit in the conventional apparatus is added with a process for classifying images with different wavelength bands, and 5a is a target discrimination processing unit in the first embodiment, which is a process for classifying images with different wavelength bands Is added to the target discrimination processing unit 8 to synchronize the image with the first and second infrared filters 2
It is a filter switching unit that switches between a and 2b. In the second embodiment, the filter switching section 8 alternately receives the infrared filters 2
By switching a and 2b, infrared images having different wavelength bands are alternately obtained, and the images are obtained by one target detection processing unit 4a.
It is designed to be processed in.

Embodiment 3 FIG. 4 is a block diagram showing another embodiment of the present invention. In the figure, 1 to 7 are the same as those in the first embodiment. Reference numeral 9 denotes a temperature determination processing unit that measures the blackbody equivalent temperature of the non-imaging object from the image brightness of the two infrared imaging units and outputs the result to the display unit 7.

Next, an outline of the temperature determination processing section will be described. Solving "Equation 2" for temperature T

[0022]

[Equation 5]

It becomes Since k can be calculated from the image brightness as shown in “Equation 3” and “Equation 4”, the temperature T
Can be calculated by the above formula.

By determining the temperature of the target candidate as described above, the data of the temperature measurement results of the target and the background obtained by mistake can be obtained, and by accumulating this data, the type of the target and the background can be obtained. Can be determined. It can also be used as a temperature measuring device for high temperature objects.

[0025]

As described above, according to the present invention, the conventional apparatus detects a target for one wavelength band by using one infrared image pickup unit, whereas it detects a target for two wavelength bands. Since the detection method is adopted, it is possible to incorporate the difference in image brightness depending on the wavelength band as the target detection processing method, so that it is possible to reduce false detection of the background as the target.

Further, according to the present invention, it is possible to measure the blackbody equivalent temperature of the target candidate from the difference in image brightness in the two wavelength bands, and therefore it can be used as a temperature measuring device for a high temperature object.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the temperature of an object to be imaged and k.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a block diagram showing another embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional target detection device.

FIG. 6 is a diagram showing a high-intensity background object and a target.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 infrared lens 2a infrared filter (transmission wavelength band is, for example, 2 μm band) 2b infrared filter (transmission wavelength band is for example, 4 μm band) 3a infrared imaging unit 3b infrared imaging unit 4a target detection processing unit 4b target detection processing unit 4c target detection processing unit 5 Target Discrimination Processing Section 6 Display Section 7 Synchronous Signal Generation Section 8 Filter Switching Section 9 Temperature Discrimination Processing Section 10 Conventional Device 11 Target Object 12 Sun 13 Reflected Object 14 Ground

Claims (3)

[Claims] 1. An infrared ray having first and second infrared ray lenses for focusing infrared light, first and second infrared ray filters having different transmission wavelength bands, and a two-dimensional infrared image pickup device. The first and second infrared imaging units that output an image, and the first and second infrared imaging units are provided in correspondence with each other, process the infrared image to detect a target candidate, and image brightness related to the target candidate. Target detection processing unit that measures the feature amount of the target candidate and target target detection unit that detects the target by comparing the difference between the feature amounts of the target candidates output from the first and second target detection processing units. A processing unit, a display unit that displays the detection result of the processing unit, and a synchronization signal generator that supplies a synchronization signal to the first and second infrared imaging units and the first and second target detection processing units. A target detecting device characterized by being performed. 2. An infrared lens for imaging infrared light, a filter switching unit for switching two infrared filters attached to an infrared light incident section and having different transmission wavelength bands in synchronization with an image, and switching the infrared filter. And an infrared imaging unit capable of outputting images of different wavelength bands in synchronism with each other and the infrared images of different wavelength bands alternately sent from the infrared imaging unit are processed to detect target candidates. A target detection processing unit, a target determination processing unit that compares the target feature amounts of two wavelengths output from the target detection unit, and a synchronization signal generation that matches the synchronization of the infrared imaging unit, the target detection processing unit, and the filter switching unit. And a target detection device. 3. The target detecting apparatus according to claim 1, further comprising a temperature determination processing unit that measures a target converted temperature based on a difference in image brightness between two wavelengths.