JP2009150842A - Temperature measuring device and vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature measuring device capable of measurement of absolute temperature distribution with high accuracy and to provide a vehicle which is equipped with the temperature measuring device. <P>SOLUTION: In the temperature measuring device, a gray scale value of each picture element is computed by compensating a pick up image signal output from a far infrared imaging part 11, and based on this gray scale value, the temperature measuring device measures the temperature of a body to be imaged. This temperature measuring device includes: a temperature parameter memory 17 which stores the relation between temperature variation quantity of the body to be imaged part corresponding to each picture element and gray scale value variation quantity of each picture element; a parameter memory 15 which stores the pick up image signal of a predetermined picture element corresponding to thermometry standard body and a corresponding relation of temperature; a temperature calculation part 14 which computes the temperature of thermometry standard body, based on the pick up image signal of the predetermined picture element, and the above corresponding relation; and a temperature correction processing part 16 which converts the gray scale value of each picture element into the gray scale value indicating the temperature of the body to be imaged, based on the temperature calculated by the temperature calculation part 14, the relation memorized by the temperature parameter memory 17, the gray scale value of the above predetermined picture element and the gray scale value of the other picture element. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a temperature measurement device that images an object to be imaged with infrared rays and measures the temperature of the object to be imaged based on a gradation value of a captured image obtained by imaging, and a vehicle equipped with the temperature measurement device.

A vehicle temperature measuring device that measures the temperature distribution in the passenger compartment has been proposed (for example, Patent Document 1). A vehicle temperature measuring device according to Patent Document 1 includes a thermopile module that measures temperature distribution in a vehicle interior by detecting infrared rays, and a standard heating element that is disposed in a detection range of the thermopile module and generates heat at a predetermined temperature. I have. In order to remove the influence of ambient light, the vehicle temperature measuring device detects infrared rays emitted from the standard heating element with a thermopile module and calibrates the temperature distribution based on the detection result.
In the vehicle temperature measuring apparatus configured as described above, the absolute temperature distribution in the passenger compartment can be accurately measured even when there is disturbance light.
On the other hand, an in-vehicle imaging device that images an object to be imaged in a vehicle interior, such as an occupant, with a long wavelength, for example, infrared rays of 8 to 14 μm, has been developed. When long wavelength infrared rays are used, the relative temperature distribution in the passenger compartment can be measured without being affected by ambient light.
JP 2006-113025 A

However, in the vehicle temperature measuring apparatus according to Patent Document 1, the temperature of the standard heating element is controlled by turning on and off the heater, so that the temperature of the standard heating element is 2 to 3 ° C. in a few minute cycle. As a result, the temperature distribution in the passenger compartment cannot be measured accurately. Specifically, when the heater is turned on, the temperature of the standard heating element instantaneously becomes high, and the temperature detected by the thermopile module is lowered by several degrees as a whole. In addition, when the heater is turned off, the temperature of the standard heating element gradually decreases, and the temperature detected by the thermopile module increases as a whole.
In addition, in order to control energization to the heater, a CPU (Central Processing Unit), a temperature sensor, a communication circuit, a power cable, and the like are required, which complicates the configuration of the vehicle temperature measurement device and increases costs. There was a problem.
Furthermore, there is a problem that power consumption increases because it is necessary to perform energization and energization control of the heater.
Furthermore, there is a problem that an arrangement space is required for arranging various circuits by routing communication lines, power cables and the like for controlling energization to the heater.

On the other hand, in a conventional vehicle-mounted imaging device, the relative temperature distribution in the passenger compartment can be measured without being affected by ambient light, but the absolute temperature of the imaging target cannot be measured. This is because the gradation value offset fluctuates due to a change in the surrounding environment of the in-vehicle imaging device, and the correspondence between the gradation value of the captured image and the temperature fluctuates. For example, even if the gradation value 32 corresponds to 20 ° C., the gradation value 32 may correspond to 25 ° C. when the surrounding environment changes.
Although fixing the offset is also conceivable, when the offset of the in-vehicle imaging device is fixed, there arises a problem that the imaging target can be imaged only in a specific ambient environment.

  The present invention has been made in view of such circumstances, and can measure the absolute temperature distribution with higher accuracy than conventional vehicle temperature measurement devices, and does not require a standard heating element and a temperature sensor. Therefore, it is an object of the present invention to provide a temperature measuring device and a vehicle equipped with the temperature measuring device that can be configured simply and at low cost.

  A temperature measurement device according to a first aspect of the present invention includes an infrared imaging unit that images an object to be imaged with infrared rays and outputs a captured image signal of each of a plurality of pixels constituting the captured image, and the imaging output from the infrared imaging unit Temperature measurement that corrects the gradation value of each pixel corresponding to the signal level of the image signal based on the imaging characteristics of the infrared imaging unit, and measures the temperature of the object to be imaged based on the corrected gradation value of each pixel An apparatus, a correspondence relationship between a captured image signal of a predetermined pixel that should correspond to a temperature measurement standard body having a predetermined infrared emissivity and a temperature of the temperature measurement standard body, and a temperature of an imaging target portion corresponding to each pixel Storage means for storing the relationship between the change amount of each pixel and the gradation value change amount of each pixel, and the temperature of the temperature measurement standard corresponding to the predetermined pixel based on the captured image signal of the predetermined pixel and the correspondence relationship Temperature calculating means for calculating Based on the temperature calculated by the temperature calculation means, the relationship stored in the storage means, the gradation value after correction of the predetermined pixel, and the gradation value after correction of other pixels, other than the predetermined pixel Conversion means for converting the gradation value of another pixel into a gradation value indicating the temperature of the imaged part corresponding to the pixel.

  In the temperature measuring device according to the second aspect of the invention, the storage means stores a plurality of the relationships that differ according to the ambient temperature, and further corresponds to the temperature based on the temperature calculated by the temperature calculation means. Selection means for selecting the relation is provided, and the conversion means converts the gradation value of the other pixel based on the relation selected by the selection means.

  In the temperature measurement device according to the third aspect of the invention, the relationship stored in the storage means is a proportional relationship between the change amount of the temperature of the imaged part corresponding to each pixel and the change amount of the gradation value of each pixel. The proportionality coefficient that defines the proportional relationship is a function of the temperature calculated by the temperature calculation means.

  A vehicle according to a fourth aspect of the invention includes the temperature measurement device according to any one of the first to third aspects of the invention, and a temperature measurement standard body that is disposed in the passenger compartment and has a predetermined infrared emissivity. The temperature measurement device is characterized in that the predetermined pixel and the temperature measurement standard body are arranged to correspond to each other.

In the first and fourth aspects of the invention, the infrared imaging unit images an object to be imaged with infrared rays, and outputs a captured image signal for each of a plurality of pixels constituting the captured image. The gradation value corresponding to the signal level of the captured image signal is corrected based on the imaging characteristics of the infrared imaging unit. The corrected gradation value has a value corresponding to the temperature of the imaging target, but the gradation value merely indicates the relative temperature of the imaging target.
The temperature calculation means calculates the temperature of the temperature measurement standard corresponding to the predetermined pixel based on the captured image signal of the predetermined pixel that should correspond to the temperature measurement standard and the correspondence stored in the storage means. In particular, according to the fourth invention, since the infrared imaging unit is arranged in the vehicle interior so that the temperature measurement standard and the predetermined image correspond to each other, the temperature is determined based on the known infrared emissivity related to the temperature measurement standard. The temperature of the measurement standard body and the captured image signal can be associated one to one.
Based on the temperature of the temperature measurement standard body calculated by the temperature calculation unit, the gradation value after correction of the predetermined pixel, and the relationship stored in the storage unit, the conversion unit converts other pixels other than the predetermined pixel. The gradation value is converted into a gradation value having a one-to-one correspondence with the temperature of the imaged part.
One temperature and one gradation value can be associated with each other based on the temperature calculated by the temperature calculation means and the gradation value of the predetermined pixel. Further, using the relationship between the amount of change in the temperature of the imaging target portion corresponding to each pixel and the amount of change in the gradation value of each pixel, using the one temperature and the one gradation value as a reference, The adjustment value can also be associated with the temperature. Therefore, the conversion means can convert the gradation value obtained by imaging into a gradation value corresponding to the temperature one to one.

In the second and fourth inventions, the storage means stores a plurality of the relationships that differ according to the ambient temperature. In general, it is known that the relationship between the amount of change in the temperature of the object to be imaged corresponding to each pixel and the amount of change in the gradation value of each pixel varies depending on the ambient temperature.
The selection unit selects a relationship corresponding to the temperature among a plurality of relationships stored in the storage unit based on the temperature calculated by the temperature calculation unit. Therefore, the conversion means can convert the temperature and the gradation value more accurately into the gradation value corresponding to the temperature on the basis of the relationship according to the ambient temperature.

In the third and fourth inventions, the storage means stores a proportional relationship as the relationship between the change amount of the temperature of the imaged part corresponding to each pixel and the change amount of the gradation value of each pixel, The proportionality coefficient that defines the proportional relationship is a function of the temperature calculated by the temperature calculation means, that is, the ambient temperature of the temperature measuring device. In general, it is known that the relationship between the amount of change in the temperature of the object to be imaged corresponding to each pixel and the amount of change in the gradation value of each pixel varies depending on the ambient temperature.
Based on the temperature calculated by the temperature calculation means, the conversion means can specify the proportional relationship between the change amount of the temperature of the imaged part corresponding to each pixel and the change amount of the gradation value of each pixel. Based on the proportional relationship according to the temperature, the gradation value obtained by imaging can be more accurately converted into a gradation value in which the temperature and the gradation value correspond one-to-one.

  According to the present invention, the absolute temperature distribution can be measured with higher accuracy than the conventional vehicle temperature measuring device, and the standard heating element and the temperature sensor are unnecessary, and the device is simple and low-cost. Can be configured.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a schematic diagram showing a configuration of a temperature measurement system according to an embodiment of the present invention. In the figure, 1 is a temperature measurement device according to the present invention mounted on a vehicle C, and the temperature measurement device 1 is connected to an ECU (Electronic Control Unit) 2 that controls the operation of the driven part 3 via a communication network. ing. The communication network is configured by, for example, a communication line such as a dedicated cable, or a wired or wireless in-vehicle LAN (Local Area Network).

FIG. 2 is a block diagram showing a configuration of the temperature measuring apparatus 1 according to the present invention. The temperature measuring device 1 includes a far-infrared imaging unit 11 that images an object to be imaged with far-infrared rays. The far-infrared imaging unit 11 is disposed in front of the driver, for example, on the steering wheel, dashboard, etc. of the vehicle C, and can capture the upper body of the driver and the ceiling portion 4 in the vehicle C. The temperature measurement standard body 4a constituting the unit enters a predetermined imaging range, and is fixed in a posture such that the distance between the far-infrared imaging unit and the temperature measurement standard body 4a is a predetermined distance.
Since the temperature measurement device 1 according to the present invention is configured to measure temperature based on the far-infrared intensity emitted from the temperature measurement standard 4a, the temperature measurement standard 4a is a member having a high infrared emissivity, for example, Cloth and rubber are preferred. Generally, the lower the infrared emissivity of the temperature measurement standard body 4a, the higher the reflected energy of the far infrared ray reflected by the temperature measurement standard body 4a, and the radiation from the temperature measurement standard body 4a according to the temperature of the temperature measurement standard body 4a. It becomes difficult to measure the intensity of the far infrared rays.
Further, the far-infrared imaging unit 11 may be arranged so that an angle formed between the normal line of the planar surface portion constituting the temperature measurement standard body 4a and the optical axis of the infrared lens 11a group is within 50 degrees. preferable.
By arranging in this way, it is possible to receive far infrared rays corresponding to the temperature of the temperature measurement standard body 4a.

The far infrared imaging unit 11 includes an infrared lens 11a and a far infrared imaging element 11b. The infrared lens 11a is a sintered body obtained by sintering, for example, zinc sulfide raw material powder, chalcogen glass, germanium, zinc selenium, and the like, and has transparency to far infrared rays in the 8 to 14 μm band.
The far-infrared imaging element 11b is an element that images a driver with far-infrared rays having a wavelength of 8 to 14 μm, that is, photoelectrically converts a far-infrared image formed by the infrared lens 11a into a captured image signal v. For example, a resistance bolometer This is a non-cooling type image sensor using a method, a ferroelectric method, an SOI diode method, a thermopile method, or the like. The far-infrared imaging element 11b has an aspect ratio of, for example, 3/2 and the number of pixels is 360 × 240. The far-infrared imaging unit 11 continuously or intermittently performs imaging processing, and captures captured image signals v (x, y) of a plurality of pixels (x, y) constituting the captured image, for example, 30 sheets per second. The frame rate is generated and output to the image configuration processing unit 12 and the temperature calculation unit 14. Note that x indicates the pixel coordinates in the horizontal direction of the captured image, and y indicates the pixel coordinates in the vertical direction of the captured image.

The image configuration processing unit 12 corrects the gradation value corresponding to the signal level of the captured image signal v output from the far-infrared imaging unit 11 based on the imaging characteristics of the far-infrared imaging unit 11, thereby correcting the level of each pixel. The tone value is calculated, and the captured image data having the tone value is given to the temperature correction processing unit 16. Specifically, the image configuration processing unit 12 AD-converts the analog captured image signal v (x, y) output from the far-infrared imaging unit 11 into digital image data, and converts the AD-converted image data into an image memory. 13 is temporarily stored. The image memory 13 is a volatile memory such as SRAM or DRAM. Then, the image configuration processing unit 12 performs various image processing such as NUC (Non-Uniformity Correction) processing for correcting non-uniformity of the captured image with respect to the image data stored in the image memory 13, and correction processing for defective pixels. The image data subjected to the image processing is supplied to the temperature correction processing unit 16. Each pixel constituting the captured image is two-dimensionally arranged, and the image data includes data indicating the luminance of each pixel indicated as the position (x, y) of each pixel and the gradation value V (x, y). Contains. The gradation value V (x, y) corrected by the NUC process is expressed by the following equation (1).
Vij = Gij · vij + Oij (1)
However, Vij is the gradation value after correction of the pixel (x, y) = (i, j), and vij is a level corresponding to the signal level of the captured image signal v of the pixel (x, y) = (i, j). A tone value, Gij is a gain correction value, Oij is an offset correction value, and i and j indicate pixel positions. Gij and Oij are calculated based on gradation values obtained by imaging an object having a uniform temperature distribution such as a black body furnace and a shutter.

  Although it is possible to measure the relative temperature distribution of the object to be imaged from the image data obtained by the image configuration processing unit 12, the gradation value V (x, y) and the temperature of each pixel are one to one. The temperature cannot be measured because it is not compatible. This is because the image configuration processing unit 12 changes the gradation value offset due to the change in the surrounding environment of the far-infrared imaging unit 11. When the offset varies, the gradation value V (x, y) varies even if the temperature of the imaging target is the same.

The temperature calculation unit 14 is provided with a parameter memory 15 that stores constants necessary for calculating the temperature of the temperature measurement standard body 4a (hereinafter referred to as a standard body temperature T _s ) that serves as a reference for temperature measurement. The parameter memory 15 is a non-volatile memory such as a flash memory, and collects the infrared emissivity ε of the temperature measurement standard 4a and the sensitivity of the far-infrared imaging device 11b, particularly far infrared rays emitted from the temperature measurement standard 4a. The sensitivity R of the image sensor pixel that emits light, the Stefan-Boltzmann constant σ, and the position (x _T , y _T ) of the pixel corresponding to the temperature measurement standard 4a are stored (see FIGS. 1 and 5). The infrared emissivity ε and the sensitivity R may be measured when the temperature measuring device 1 is manufactured, and constants obtained by the measurement may be stored in the parameter memory 15.
The temperature calculation unit 14 calculates the standard body temperature T _S based on the captured image signal v output from the far infrared imaging unit and the constant stored in the parameter memory 15.

Next, the calculation principle of the standard body temperature T _S will be described. The far-infrared radiation energy radiated from the temperature measurement standard 4a in the thermal equilibrium state and incident on the infrared lens 11a is expressed by the following formula (2). Where U is the radiant energy, λ is the wavelength of the far infrared ray emitted from the temperature measurement standard 4a, T _s is the temperature of the temperature measurement standard, Ω is a solid angle, and B _λ (T _s ) is the temperature measurement standard. The intensity of the far infrared ray having the wavelength λ when the temperature of 4a is T _s is shown. The integration range is a solid angle range in which the wavelength is 8 to 14 μm and the temperature measurement standard 4a looks into the infrared lens 11a.

When the infrared rays radiated from the temperature measurement standard 4a are incident on the infrared lens 11a and are condensed on the far-infrared imaging device 11b, the far-infrared imaging device 11b has a voltage level corresponding to the collected radiation energy. v (x _T , y _T ) is output. The signal level of the captured image signal v is expressed by the following equation (3). However, R is the sensitivity R of the far-infrared imaging device 11b, in particular, the sensitivity R of the imaging device pixel that collects the far-infrared rays emitted from the temperature measurement standard 4a.
v (x _T , y _T ) = R · U (3)

From the above formulas (2) and (3), the standard body temperature T _S is expressed by the following formula (4), and the temperature calculation unit 14 calculates the standard body temperature T _S by using the following formula (4) and calculates it. The obtained standard body temperature T _S is given to the temperature correction processing unit 16.

In calculating the temperature, only the far infrared ray radiated from the temperature measurement standard body 4a is considered. Needless to say, the infrared lens 11a, the far infrared imaging element 11b, and the infrared lens 11a constituting the far infrared imaging unit 11 are considered. The lens barrel (not shown) that holds the light also emits far infrared rays corresponding to the ambient temperature. There are also far infrared rays reflected from the surrounding environment in the passenger compartment. Therefore, in order to make the signal level of the picked-up image signal v output from the far-infrared imaging device 11b correspond to the absolute value of the temperature, it corresponds to the temperature variation of each of the infrared lens 11a, the barrel, and the far-infrared imaging device 11b. It is necessary to correct the standard body temperature T _S based on the fluctuation of the signal level of the captured image signal v. For example, it is necessary to subtract the amount of radiant energy radiated from the far-infrared imaging unit 11 and other members from the radiant energy radiated from the temperature measurement standard body 4a. The relationship between the energy radiated from the far-infrared imaging unit 11 and the temperature may be measured in advance and stored in the parameter memory 15.

  The temperature correction processing unit 16 is, for example, a microcomputer including an MPU (Microprocessor Unit), and the image data subjected to image processing by the image configuration processing unit 12 has a gradation value W (x, y) corresponding to the temperature on a one-to-one basis. A temperature correction process, which will be described later, is converted to image data having The MPU includes a ROM for recording various computer programs and data to be executed based on the control of the MPU via a bus (not shown), a RAM for recording various data temporarily generated when the computer program recorded in the ROM is executed, A frame memory for temporarily recording image data, an I / O port, and the like are connected, and the MPU executes the computer program to execute the conversion process of the gradation value W (x, y). The temperature correction processing unit 16 gives the temperature-corrected image data to the communication interface 18. The communication interface 18 converts the temperature-corrected image data into analog image signals such as NTSC (National Television System Committee Standard), digital image data conforming to IEEE 1394 and MOST standards, and transmits the digital image data to the ECU 2.

The temperature measuring device 1 also includes a temperature parameter memory 17 that stores various parameters necessary for the temperature correction process.
The temperature parameter memory 17 is a non-volatile memory such as a flash memory, and a predetermined pixel (x _T , y _T ) corresponding to the gain Db for measuring the absolute temperature distribution of the imaging target and the temperature measurement standard body 4a. Is stored. The gain Db is the amount of change in the temperature of the object to be imaged corresponding to each pixel and the amount of temporal change in the gradation value of each pixel, that is, the gradation value when the temperature of the object to be imaged is changed by 1 ° C. The amount of change is shown. Since the gain Db is a substantially constant value regardless of the temperature of the object to be imaged, the gain Db is measured when the temperature measuring device 1 is manufactured, and the gain Db obtained by the measurement is stored in the temperature parameter memory 17. good.
Further, the temperature parameter memory 17 stores a gain Dx and a measurement reference temperature T _MIN for converting the gradation value of the image data so that the external ECU 2 can recognize the absolute temperature distribution. The gain Dx is a constant represented by the following formula (5).
Dx = maximum gradation value P _MAX / (measurement upper limit temperature T _{MAX -measurement} reference temperature T _MIN ) (5)

  The gain Dx indicates the change amount of the gradation value corresponding to the change amount of the unit temperature of 1 ° C. in the image data indicating the absolute temperature distribution.

  FIG. 3 is a block diagram showing a configuration of the ECU 2. The ECU 2 is a control device that controls the operation of the driven part 3 such as an air conditioner or an airbag device by using an absolute temperature distribution in the vehicle interior. The ECU 2 includes a control unit 21, and a ROM 22, a RAM 23, a communication interface 24, an image memory 25, a control interface 26, and the like are connected to the control unit 21 via a bus 27.

The ROM 22 stores a computer program for controlling the operation of the driven unit 3 based on the processing for calculating the temperature in the vehicle interior based on the image data transmitted from the temperature measuring device 1 and the absolute temperature distribution in the vehicle interior. is doing. Further, ROM 22 stores a gain Dx, the measured reference temperature T _MIN.

  The RAM 23 is a volatile memory that stores various data generated when the control unit 21 executes the computer program.

  The communication interface 24 receives the image data transmitted from the temperature measuring device 1, and the image memory 25 temporarily stores the image data received by the communication interface 24. The control interface 26 outputs a control signal to the driven unit 3 under the control of the control unit 21 and controls the operation of the driven unit 3.

The driven unit 3 is, for example, an air conditioner, and can control the blowing temperature, the blowing direction, the blowing speed, etc. by the air conditioner using the absolute temperature distribution of the driver's upper body and its surroundings, and more comfortably The passenger compartment can be air-conditioned.
Further, the driven unit 3 is, for example, an airbag device, and by using an absolute temperature distribution, the driver's head, upper body, and surrounding portions thereof are discriminated, and the presence / absence of the driver, the presence / absence of wearing glasses, the body shape, The posture and the like can be recognized more accurately, and the airbag deployment method can be controlled according to the position of the driver's head, whether or not glasses are worn, the physique, and the posture. Can protect the driver.

FIG. 4 is a flowchart showing a processing procedure of the temperature correction processing unit 16 related to the temperature correction processing. The temperature correction processing unit 16 acquires the image data output from the image configuration processing unit 12 (step S11). Then, the temperature correction processing unit 16 causes the temperature calculation unit 14 to acquire the captured image signal v of the predetermined pixel (x _T , y _T ) (step S12), and the infrared emissivity ε, sensitivity R, and Boltzmann constant σ from the parameter memory 15. to read the (step S13), and thereby calculates a standard body temperature T _S (step S14).

Next, the temperature correction processing unit 16 specifies the gradation value Z = V (x _T , y _T ) of the predetermined pixel (x _T , y _T ) corresponding to the temperature measurement standard body 4a (step S15).

FIG. 5 is an explanatory diagram for explaining a captured image and predetermined pixels (x _T , y _T ). A horizontally long rectangular frame indicates a captured image, a horizontal axis X indicates a horizontal line, and a vertical axis Y indicates a vertical line. White circles indicate predetermined pixels (x _T , y _T ) corresponding to the temperature measurement standard 4a. The temperature correction processing unit 16 can associate one gradation value Z and one temperature T _s from the gradation value Z of the predetermined pixel (x _T , y _T ) and the standard body temperature T _S.

Next, the temperature correction processing unit 16 reads the gain Db, the gain Dx, and the measurement reference temperature T _MIN (step S16), and uses the gradation value V (x, y) as the gradation value W (x, y) indicating the temperature. ) Is performed (step S17).

Figure 6 is a graph tone value V (x, y) and indicating a correspondence relationship between the temperature T _ABS. The horizontal axis indicates the gradation value V (x, y), and the vertical axis indicates the temperature T _{ABS of the} imaging target corresponding to each pixel. The temperature T _ABS indicates the absolute value of the temperature. As shown in FIG. 6, the temperature T _ABS is proportional to the gradation value V (x, y), and the proportionality coefficient is 1 / gain Db. Therefore, from the standard body temperature T _S acquired from the temperature calculation unit 14, the gradation value Z of the predetermined pixel (x _T , y _T ) obtained by imaging the temperature measurement standard body 4a, and the gain Db, the gradation is calculated. The value V (x, y) and the temperature T _ABS can be associated one to one. The temperature T _ABS is expressed by the following formula (6).
T _ABS = V (x, y) / Db + T _s −Z / Db (6)

Note that the above equation (6) is based on the assumption that the gradation value V (x, y) is proportional to the temperature T _ABS , and contradicts that the signal level of the captured image signal v is proportional to the fourth power of the temperature. However, it is known that the gradation value V (x, y) is approximately proportional to the temperature T _ABS in the room temperature range.

However, even if the image data having the gradation value V (x, y) is transmitted to the external ECU 2 as it is, the correspondence between the gradation value V (x, y) and the temperature is not taken on the ECU 2 side. The temperature of the image pickup body cannot be calculated. Therefore, the temperature correction processing unit 16 associates the two elements. The first element is the offset, that is, the measurement reference temperature T _MIN , and the second element is the gain, that is, the ratio of the change amount of the gradation value to the change amount of the temperature. Since the ECU 2 stores the predetermined measurement reference temperature T _MIN and the gain Dx as the offset and gain, the temperature correction processing unit 16 calculates the temperature with the measurement reference temperature T _MIN and the gain Dx on the ECU 2 side. The gradation value V (x, y) is converted into a gradation value W (x, y) so that

Figure 7 is a graph showing a relationship between a gradation value and the temperature T _ABS. The horizontal axis tone value W (x, y), the vertical axis represents the temperature T _ABS. In step S15, the temperature correction processing unit 16 adjusts the gradation value 1 to the measurement reference temperature T _MIN as shown in FIG. 7 so that the change amount of the gradation value when the unit temperature changes by 1 ° C. becomes the gain Dx. The gradation value V (x, y) is converted into a gradation value W (x, y).

The temperature-corrected gradation value W (x, y) is expressed by the following equation (7).
W (x, y) = (T _ABS −T _MIN ) × Dx (7)
Eventually, the above equation (7) can be transformed into the following equation (8), and the temperature correction processing unit 16 calculates the gradation value W (x, y) by the following equation (8).
W (x, y) = Dx / Db × [V− {Z− (T _s −T _MIN ) × Db}] (8)

For example, when the measurement reference temperature T _MIN is 16 ° C. and the gain Dx is 8, the range of 16 ° C. to 48 ° C. and the gradation values 1 to 256 can be associated one to one. In this case, 20 ° C. corresponds to the gradation value 32.
Note that when the converted gradation value W (x, y) is 0 or less or greater than 256, the gradation value W (x, y) is rounded to 1 and 256, respectively.

  Next, the temperature correction processing unit 16 transmits the image data having the temperature-corrected gradation value W (x, y) to the ECU 2 (step S18).

FIG. 8 is a flowchart showing a processing procedure of the control unit 21 of the ECU 2. The control unit 21 receives the image data whose temperature has been corrected by the temperature measuring device 1 (step S21). Next, the control unit 21 reads the gain Dx and the measurement reference temperature T _MIN from the ROM 22 (step S22), and calculates the temperature T _ABS based on the gradation value W (x, y), the gain Dx, and the measurement reference temperature T _MIN. (Step S23), and the process ends.

The temperature T _ABS can be calculated by the following equation (9).
T _ABS = W (x, y) / Dx + T _MIN (9)

  In the temperature measurement device 1 and the vehicle C according to the embodiment configured as described above, the absolute temperature distribution of the imaging target can be measured more accurately than the conventional vehicle temperature measurement device. .

  Further, since the standard heating element and the temperature sensor are not required as in the prior art, various circuits for controlling the standard heating element are not required, and the temperature measuring device 1 can be configured easily and at low cost.

  Furthermore, the absolute value of the temperature of the object to be imaged can be measured with a simple configuration compared to general thermography. In thermography, it is necessary to obtain and input the value of the infrared emissivity of the measurement object every time it is measured. In the present invention, the infrared emissivity ε of the temperature measurement standard 4a is stored in the parameter memory 15 in advance. Therefore, it is possible to save the trouble of obtaining and inputting the infrared emissivity.

  Furthermore, since it is not necessary to perform energization to the heater and control of energization as in the prior art, the absolute temperature distribution of the imaging target can be measured with low power consumption.

  Furthermore, unlike the prior art, it is not necessary to route communication lines, power cables, and the like for controlling energization to the heater and to arrange various circuits, so that space can be saved. In particular, in the automobile field, since the use of electronics has progressed, the size of the vehicle C and the expansion of the interior space of the vehicle C have been demanded. Therefore, the temperature measuring device 1 mounted on the vehicle C is particularly effective.

  Furthermore, even when the image configuration processing unit 12 is configured to change the offset of the gradation value V (x, y) according to the ambient environment of the temperature measuring device, the gradation corresponding to the temperature one-to-one. The value W (x, y) can be transmitted to the external device.

  FIG. 9 is a flowchart illustrating a processing procedure of the temperature correction processing unit 16 according to the first modification. The temperature parameter memory 17 according to the first modification stores a plurality of gains Db1,..., Dbk,... That differ depending on the ambient temperature, and the temperature correction processing unit 16 obtains the gain Dbk corresponding to the ambient temperature. By using this, more accurate temperature measurement is possible. However, k is a natural number of 2 or more.

Similarly to FIG. 4, the temperature correction processing unit 16 acquires image data (step S31), causes the temperature calculation unit 14 to acquire the captured image signal v of the predetermined pixel (x _T , y _T ) (step S32), and parameters The infrared emissivity ε, sensitivity R, and Boltzmann constant σ are read from the memory 15 (step S33), and the standard body temperature T _S is calculated (step S34). Next, the temperature correction processing unit 16 specifies the gradation value Z of the predetermined pixel (x _T , y _T ) (step S35). Then, the temperature correction processing unit 16, based on the standard body temperature T _S calculated in step S34, is selected and read gain Dbk corresponding to the standard body temperature T _S (step S36). Thereafter, similarly to FIG. 4, the gain Dx and the measurement reference temperature T _MIN are read (step S37), the temperature correction process is performed (step S38), the temperature-corrected image data is transmitted (step S39), and the process ends.

  In the temperature measurement device 1 and the vehicle C according to the first modification, the gain Dbk corresponding to the ambient temperature of the temperature measurement device 1 is used, so that the temperature of the imaging target can be accurately determined regardless of the ambient temperature. It can be measured.

FIG. 10 is a flowchart illustrating a processing procedure of the temperature correction processing unit 16 according to the second modification. The temperature parameter memory 17 according to the second modification stores constants a and b that define a gain Db that linearly changes according to the ambient temperature. The constants a and b are values that define a gain Db represented by Db (T _s ) = a × T _s + b. The constants a and b are measured and calculated in advance when the temperature measuring device 1 is manufactured, and are stored in the temperature parameter memory 17. Keep it. The temperature correction processing unit 16 calculates the gain Db based on the constants a and b and the standard body temperature T _S calculated by the temperature calculation unit 14, and uses the calculated gain Db to perform more accurate temperature measurement. It is possible.

Similar to FIG. 4, the temperature correction processing unit 16 acquires image data (step S41), causes the temperature calculation unit 14 to acquire the captured image signal v of the predetermined pixel (x _T , y _T ) (step S42), and parameters. The infrared emissivity ε, sensitivity R, and Boltzmann constant σ are read from the memory 15 (step S43), and the standard body temperature T _S is calculated (step S44). Next, the temperature correction processing unit 16 specifies the gradation value Z of the predetermined pixel (x _T , y _T ) (step S45). The temperature correction processing unit 16 reads the constants a and b for calculating the gain Db from the temperature parameter memory 17 (step S46), and based on the standard body temperature T _S and the constants a and b, the gain Db (T _S ) = A × T _S + b is calculated (step S47). Thereafter, similarly to FIG. 4, the gain Dx and the measurement reference temperature _TMIN are read (step S48), the temperature correction process is performed (step S49), the temperature-corrected image data is transmitted (step S50), and the process ends.

  In the temperature measurement device 1 and the vehicle C according to the second modification, the gain Db corresponding to the ambient temperature of the temperature measurement device 1 is calculated, so that the image is captured regardless of the ambient temperature of the temperature measurement device 1. The body temperature can be measured accurately.

  In the embodiment and the modified example, the case where the imaging target is imaged with far infrared rays has been described. However, the imaging target is imaged with infrared rays in other frequency bands, and the temperature is measured. It may be configured. However, when a far-infrared imaging device is used, it is not affected by external light incident on the passenger compartment, and therefore, it is possible to accurately measure the absolute temperature distribution of the imaging target, which is preferable.

Moreover, although the case where the instantaneous temperature is used as the standard body temperature T _S has been described, a plurality of standard body temperatures T _S are obtained at different times, a moving average is calculated from the plurality of standard body temperatures T _S , You may comprise so that a gradation value may be changed using a moving average. Similarly, an IIR (Infinite Impulse Response) filter may be used to suppress fluctuations in the standard body temperature T _S. The filter period is preferably, for example, about 0.5 to 1.5 seconds, can follow a temperature change, and can effectively suppress noise. When configured in this way, it is possible to prevent the measured temperature from fluctuating due to short-term fluctuations in the standard body temperature T _S.
Furthermore, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic diagram which shows the structure of the temperature measurement system which concerns on embodiment of this invention. It is a block diagram which shows the structure of the temperature measuring device which concerns on this invention. It is a block diagram which shows the structure of ECU. It is a flowchart which shows the process sequence of the temperature correction process part which concerns on a temperature correction process. It is explanatory drawing for demonstrating a captured image and a predetermined pixel. It is a graph which shows the correspondence of a gradation value and temperature. It is a graph which shows the correspondence of a gradation value and temperature. It is a flowchart which shows the process sequence of the control part of ECU. It is a flowchart which shows the process sequence of the temperature correction process part which concerns on a 1st modification. It is a flowchart which shows the process sequence of the temperature correction process part which concerns on a 2nd modification.

Explanation of symbols

1 Temperature measuring device 2 ECU
DESCRIPTION OF SYMBOLS 3 Driven part 4 Ceiling part 4a Temperature measurement standard object 11 Far-infrared imaging part 11a Infrared lens 11b Far-infrared imaging element 12 Image structure process part 13 Image memory 14 Temperature calculation part 15 Parameter memory 16 Temperature correction process part 17 Temperature parameter memory 18 Communication interface

Claims (4)

Each pixel corresponding to the signal level of the imaged image signal output from the infrared imaging unit is provided with an infrared imaging unit that images the imaging object with infrared rays and outputs a captured image signal of each of the plurality of pixels constituting the captured image Is a temperature measuring device that corrects the gradation value based on the imaging characteristics of the infrared imaging unit and measures the temperature of the imaging target based on the corrected gradation value of each pixel,
Correspondence relationship between the imaged image signal of a predetermined pixel to be associated with a temperature measurement standard having a predetermined infrared emissivity and the temperature of the temperature measurement standard, the amount of change in the temperature of the imaged part corresponding to each pixel, and each Storage means for storing the relationship between the amount of change in the gradation value of the pixel;
Temperature calculating means for calculating the temperature of the temperature measurement standard corresponding to the predetermined pixel based on the captured image signal of the predetermined pixel and the correspondence relationship;
Based on the temperature calculated by the temperature calculation means, the relationship stored in the storage means, the gradation value after correction of the predetermined pixel, and the gradation value after correction of other pixels, other than the predetermined pixel A temperature measuring device comprising: conversion means for converting the gradation value of another pixel into a gradation value indicating the temperature of the imaged part corresponding to the pixel. The storage means stores a plurality of the relationships different depending on the ambient temperature,
And a selection means for selecting the relationship corresponding to the temperature based on the temperature calculated by the temperature calculation means,
The converting means includes
The temperature measurement device according to claim 1, wherein gradation values of the other pixels are converted based on the relationship selected by the selection unit. The relationship stored in the storage means is a proportional relationship between the change amount of the temperature of the imaging target portion corresponding to each pixel and the change amount of the gradation value of each pixel, and the proportionality coefficient defining the proportional relationship is The temperature measuring device according to claim 1, wherein the temperature measuring device is a function of the temperature calculated by the temperature calculating unit. The temperature measuring device according to any one of claims 1 to 3,
It is arranged in the passenger compartment and has a temperature measurement standard with a predetermined infrared emissivity,
The temperature measurement device is arranged such that the predetermined pixel and the temperature measurement standard body correspond to each other.

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