JPH05332924A - Measuring apparatus of absorbance of infrared ray of object - Google Patents

Abstract

PURPOSE:To correctly measure a moving object such as a living creature with good response by forming a filter in stripes or mosaic and dispersing an area allowing the light of a plurality of wavelengths to pass, and then photographing by an image sensor. CONSTITUTION:A polarization filter 2 for removing the surface scattering light of an object, and a wavelength selecting filter 3 which selectively passes infrared rays of wavelengths lambda1, lambda2, lambda3 are mounted in front of the photodetecting surface of an infrared vidicon camera 1 which photographs the scattering/reflecting light from the object. The filter 3 is formed of black stripes BS as light shielding areas and stripes of light passing areas which are alternately and uniformly distributed. The output of the camera 1 is amplified at 4 and input to a separating circuit 5. The separating circuit, 5 separates the outputs of the camera 1 per wavelength and constructs again. Therefore, the photographing timing is the same for a plurality of wavelengths, so that the correctness is not lost by the move of the object,.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image measuring apparatus for infrared absorption of an object to be measured containing an infrared absorbing substance.

[0002]

2. Description of the Related Art Measuring the infrared absorption of an object makes it possible to determine the material of the object (measurement object).
As such a conventional technique, there is a method of irradiating infrared light of a plurality of wavelengths and detecting reflected light scattered light thereof, and an apparatus therefor is proposed.

[0003]

However, in the conventional measuring apparatus, the object to be measured is imaged by two cameras having different wavelengths having sensitivity, or one camera is used to set the object to be measured. Since it is necessary to replace the filter and capture an image of another wavelength at another timing, there is a drawback that simultaneous measurement cannot be performed.

Particularly, when the object to be measured is a living body, for example, an image of wavelength λ ₁ is taken at time T ₁ and wavelength λ ₁ at time T _2.
Since that will the _second imaging, the time difference (T ₁ -T
_{When the} living body moves in ₂ ), the comparison of images and the calculation between images cannot be executed accurately.

The present invention is intended to solve such a problem, and was completed on the premise of the following knowledge by the present inventor. That is, H-O-H, R
-OH, O-D, C-H, and N-H bonds exhibit stretching spectra in the infrared light region, overtones of bending vibrations, and bond sounds, each exhibiting a characteristic absorption spectrum in the near infrared region. ..

This is specifically shown in FIGS. 1 and 2. The present inventor has found that the wavelength is from 1100 nm to 2600.
In the range of nm, water, heavy water, ethanol, benzene, petroleum ether, and n-hexylamine were examined for the wavelength dependence of the absorbance. For substances other than water and heavy water, the scale on the vertical axis is 5 times.

What is clear from this is that if the wavelength of infrared light is appropriately selected, the object to be measured can be observed under the condition that the absorbance is significantly different, which has a double meaning. First, if the two wavelengths for measurement are set in a region where the differential coefficient of absorbance is large and the above two wavelengths are close to each other, the scattering degree can be made substantially equal by Mie's scattering theory, so the infrared absorbance It is possible to measure with high accuracy.
Second, if you select two wavelengths that have a large difference in absorbance,
Infrared light of low absorbance reaches a deep region of the object to be measured, and infrared light of high absorbance reaches only a shallow region, so that it is possible to obtain so-called depth information.

The present invention makes it possible to perform these measurements accurately and responsively even on an object to be measured which is moving like a living body.

[0009]

SUMMARY OF THE INVENTION A measuring device for infrared absorption of an object to be measured according to the present invention irradiates the object to be measured with infrared light of at least two wavelengths which have sufficiently different absorptions by infrared absorbing substances. Illuminating means, a filter formed by substantially uniformly spatially distributing a plurality of transmission regions for each wavelength that selectively transmits at least two wavelengths of infrared light, and a light-receiving surface facing the filter. An image sensor that is arranged and detects the transmitted light of the filter for each of a plurality of transmission areas on the light-receiving surface and outputs it, a separation means that separates the output of the image sensor for each wavelength and outputs the plurality of transmission areas, and a separation means. Output display means for displaying the output of at least every two wavelengths.

[0010]

According to the present invention, the filter is formed into a stripe shape or a mosaic shape, the regions that transmit light of a plurality of wavelengths are dispersed, and the transmitted light is imaged by the image sensor. Then, the output of this image sensor is sorted by wavelength by the sorting means and reconstructed.
The imaging timings of a plurality of wavelengths are the same, so that the accuracy is not lost due to the movement of the measured object.

[0011]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 3 shows the main configuration of the apparatus of the embodiment. An object to be measured (not shown) is illuminated by a light source (not shown) as an illumination unit, and scattered and reflected light from the object to be measured is imaged by the infrared vidicon camera 1. Here, on the front surface of the light receiving surface of the infrared vidicon camera 1, a polarization filter 2 for removing surface scattered light of the object to be measured,
Wavelength λ _1, λ _2, the wavelength selection filter 3 which selectively transmits infrared light of lambda ₃ is mounted.

Here, the wavelength selection filter 3 is composed of black stripes BS serving as light-shielding areas and stripe-shaped transmission areas alternately and uniformly and spatially distributed. The longitudinal direction of this stripe is orthogonal to the scanning direction of the infrared vidicon camera 1, and therefore the output signal from the infrared vidicon camera 1 is in the order of black stripe BS, λ ₁ transmissive region, λ ₂ transmissive region, λ ₃ transmissive region. become.

The output of the infrared vidicon camera 1 is amplified by the preamplifier 4 and input to the classification circuit 5. Sorting circuit 5
Is a comparator 51 that binarizes the output of the preamplifier 4 at the threshold level V _th , a phase shift circuit 52 that outputs pulses φ _{1 to} φ ₃ delayed by a certain time according to the output pulse φ ₀ , and this output pulse φ It has a MOS transistor Q _1, Q _2, Q ₃ of the ₁ to [phi] ₃ becomes oN, respectively, and an operation switch S _1, S _2, S ₃ of these connected in series.

The operation of the classification circuit 5 is as shown in the timing chart of FIG. Here, I ₀ corresponds to the output of the preamplifier 4, that is, the image output when the light receiving surface (photoconductive surface) of the infrared vidicon camera 1 is scanned with an electron beam (scanning in the direction orthogonal to the stripe), and φ ₀
Is the output of the comparator 51, that is, the pulse output that falls at the timing when the electron beam scans the black stripe BS.

Φ _{1 to} φ ₃ are output pulses of the phase shift circuit 52, which are delayed from the pulse φ ₀ by time t _{1 to} t ₃ , respectively. The amount of delay by the phase shift circuit 52 corresponds to the scanning speed of the electron beam of the infrared vidicon camera 1, and the falling periods of the pulses φ _{1 to} φ ₃ are λ _{1 to} λ.
₃ It matches the scanning timing of the transparent area. Therefore, each MOS transistor Q ₁ to Q ₃ is turned ON by the scanning timing of lambda ₁ to [lambda] ₃ transmission region by a pulse phi ₁ to [phi] _3.

Now, the output level (luminance level) of the preamplifier 4 when the λ _{1 to} λ ₃ transmissive region is scanned is I ₁₀ , I.
₂₀ and I ₃₀ , the MOS transistors Q _{1 to} Q
The output level of ₃ is I _{10 to} I ₃₀ . Therefore, if the operation switch S ₁ is manually turned on, the video signal corresponding to the λ ₁ transmission area is output from the classification circuit 5, and if the operation switches S ₁ and S ₂ are simultaneously turned on, the classification circuit 5 outputs. Video signals corresponding to the λ ₁ and λ ₂ transmission areas are output.

Output of the classification circuit 5 (image data for each wavelength λ _{1 to} λ ₃ or image data obtained by combining a plurality of wavelengths)
Are provided to the image processing apparatus 6 and stored in the storage unit 61. Then, the calculation unit 62 performs a calculation process described later,
It is sent to the output device 7. The output device 7 has a CRT display or a video printer (both not shown), and the above image data is output and displayed.

FIG. 5A shows an example constituted by the CCD image sensor 11. The wavelength selection filter 3 includes λ ₁ to λ ₄ transmission regions arranged in a mosaic pattern, and the CCD image sensor 11 correspondingly has a large number of pixels (photodiodes). In this case, by using the scanning clock of the CCD image sensor 11 as a synchronizing signal, the image data can be separately output for each wavelength λ _{1 to} λ ₄ . The polarization filter 2 is mounted on the front surface of the wavelength selection filter 3.

FIG. 5B shows an example in which the linear image sensor 12 is used. The wavelength selection filter 3 has λ ₁ and λ ₂
The transmission area for two wavelengths is included. Then, photodiodes are arranged in an array on the linear image sensor 12 corresponding to the transmissive regions. Also in this case, the scanning clock may be used as the synchronization signal, and the polarization filter 2
As a result, the influence of the surface scattering component is reduced.

Next, a mode of measurement using the apparatus of the above embodiment will be described.

First Embodiment It is assumed that the inside of an object to be measured contains an absorbing substance and a scattering substance to be measured, and a wavelength (λ ₁ ,
It is assumed that infrared light of λ ₂ ) is irradiated. Where infrared light λ
_It is assumed that the attenuation coefficients due to the DUT that scatters and absorbs ₁ and λ ₂ are k ₁ and k ₂ , and that they are distinguishable from each other. The wavelength lambda _1, by irradiation of lambda ₂ light, the wavelength lambda ₁ of course, through the filter of the scattered reflected light stripe or mosaic pattern of lambda _2, are detected by the image sensor, the detected light intensity D _1, Let it be D ₂ .

Assuming that there is not a large difference in the scattering coefficient between the wavelengths λ ₁ and λ ₂ , the detected light amount D
₁ , D ₂ has a value corresponding to an attenuation coefficient in which absorption is dominant, and the detected light amount D ₁ of a wavelength with a small attenuation coefficient (assumed to be λ ₁ ) has a relatively large amount of deep position information.
Detected light intensity D for wavelengths with a large attenuation coefficient (assumed to be λ ₂ ).
₂ will have relatively more information on shallow locations.

This is shown in FIG. Curves a ₁ and a ₂ shown by solid lines are the intensities of the illumination light of wavelengths λ ₁ and λ _{2 at} the depth: x, and the illumination light of wavelength λ _{1 having} a small attenuation coefficient is compared to the illumination light of wavelength λ _2. You can see that it has reached a deep position. The scattered reflected light that is the illumination light scattered by the scattering substance and returns to the surface of the object to be measured is as shown by the curved lines b ₁ and b ₂ , and b ₁ = a ₁ × a ₁ and b ₂ = It is calculated as a ₂ × a ₂ . That is, the detection light amount D ₁ of the wavelength lambda ₁
It is understood that includes not only a shallow position of the object to be measured but also a large amount of scattering information at a deep position, and the detected light amount D ₂ of the wavelength λ ₂ mainly includes a large amount of shallow position scattering information.

Therefore, when these differences c are calculated as c = b ₁ -b ₂ = a ₁ × a ₁ -a ₂ × a ₂ , c is the detected light amount difference D ₁ -D _2, which is scattered and absorbed. It can be seen that the distribution of the amount of scattered reflected light that contributes from each depth in the measured object is shown. Here, the detection timings of the wavelengths λ ₁ and λ ₂ are the same,
The movement of the DUT does not impair the accuracy.

Here, the depth information d as an average barycentric value that the difference in the amount of scattered reflection light from the object to be measured has, for example, the following equation:

[0027]

[Equation 1]

Quantitatively determined by

Second Embodiment It is assumed that the object to be measured is formed by impregnating plant fiber as a scatterer with water as a light-absorbing substance, and two wavelengths (λ ₁ , λ ₂₎ close to each other are formed. ) Infrared light is irradiated. That is, according to Mie's scattering theory, the degree of scattering is substantially equal, and the absorption spectrum of the O—H bond contained in water is monotonically continuous in the wavelength region with the largest differential coefficient around the maximum wavelength [λ ₀ ]. The wavelengths are set to two arbitrary points.

Here, it is assumed that the scattering degrees of the infrared light λ ₁ and λ ₂ are S ₁ and S ₂ , and the absorption degrees thereof are A ₁ and A ₂ . By irradiating this wavelength λ ₁ and λ ₂ light, the wavelength λ
The scattered reflected lights of ₁ and λ ₂ are detected through a mosaic or stripe wavelength selection filter, and the energies of the detected lights are E ₁ and E ₂ . Irradiation light energy is E
_Letting S be the degree of scattering and A be the degree of absorption, where _{0 is} the reflected light energy and E is E = E ₀ · e ^{− (A + S)} (1), ln (E ₁ / E0) = - a _{(a 1 + S 2) ...} (3) - (a 1 + S 1) ... (2) ln (E 2 / E 0) =. When determining the difference between (2) and _{(3), ln (E 1 / E 0} ) -1n (E 2 / E 0) = - (A 1 + S 1) + (A 2 + S 2) ... (4 ) Becomes.

Here, if the scattering degrees S ₁ and S ₂ are equivalent because the wavelengths λ ₁ and λ ₂ are similar, then S ₁ = S ₂ can be obtained, and the equation (4) is obtained. the _{ln (E 1 / E 2)} = - a _{(a 1 + a 2) ...} (5). This is a difference only in the absorbance, and means that the absorption information in which the scattering information is substantially deleted can be obtained by the calculation of the equation (5) based on the data measured at the same timing.

The above principle will be described with reference to FIG.

As shown in FIG. 7A, the absorbance A of the object to be measured is
Has a peak value at the wavelength λ ₀ and a bottom value at the wavelength λ ₃ , the absorption curve has a large differential coefficient at the wavelengths λ ₁ and λ ₂ therebetween. On the other hand, as shown in FIG. 7B, the scattering degree S gradually changes over the wavelength λ ₀ → λ ₁ → λ ₂ → λ ₃ and is approximately equal at the approximated wavelengths λ ₁ and λ ₂ . .. Therefore, by subtracting the contribution of the scattering degree S, only the contribution of the absorption degree A can be obtained. The measurement data corresponding to the absorbance A corresponds to the concentration of the substance (light absorbing substance) contained in the DUT 2, and therefore the concentration can be quantified. Moreover, in the present invention, since the measurement timings of the wavelengths λ ₁ and λ ₂ are the same time,
Infrared absorbance can be measured with extremely high responsiveness.

[0034]

As described above, the filter is formed into a stripe shape or a mosaic shape, the regions that transmit light of a plurality of wavelengths are dispersed, and the transmitted light is imaged by the image sensor. Then, the output of this image sensor is
Since the wavelengths are separated and reconstructed by the separating means, the imaging timings of a plurality of wavelengths are the same, and therefore the accuracy is not lost due to the movement of the measured object. Therefore, the infrared absorption can be measured with extremely high responsiveness.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of infrared absorbance.

FIG. 2 is an explanatory diagram of infrared absorbance.

FIG. 3 is a configuration diagram of an apparatus according to an embodiment.

FIG. 4 is a timing chart showing the operation.

FIG. 5 is a schematic view of an apparatus according to another embodiment.

FIG. 6 is an explanatory diagram of a first usage mode.

FIG. 7 is an explanatory diagram of a second usage mode.

[Explanation of symbols]

1 ... Infrared vidicon camera, 11 ... CCD image sensor, 12 ... Linear image sensor, 2 ... Polarization filter,
3 ... Wavelength selection filter, 4 ... Preamplifier, 5 ... Separation circuit, 51 ... Comparator, 52 ... Phase shift circuit, 6 ... Image processing device, 61 ... Storage unit, 62 ... Arithmetic unit, 7 ... Output device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Hiramatsu 1126-1, Nomachi, Hamamatsu City, Shizuoka Prefecture Hamamatsu Photonics KK

Claims (8)

[Claims] 1. An apparatus for measuring the infrared absorption of an object to be measured containing an infrared absorbing substance, the illumination irradiating the object to be measured with infrared light of at least two wavelengths, the absorbances of which are sufficiently different. Means, a filter formed by a plurality of transmission regions for each wavelength selectively transmitting infrared light of at least two wavelengths are formed in a substantially uniform positional distribution, the light-receiving surface is opposed to the filter. An image sensor that is arranged in a plurality and that detects the light transmitted through the filter on the light receiving surface for each of the plurality of transmission regions and outputs the light, and separates the output of the image sensor for each of the at least two wavelengths from each of the plurality of transmission regions. And an output display unit for displaying the output of the separation unit for each of the at least two wavelengths. Measuring device. 2. The apparatus for measuring infrared absorption of an object to be measured according to claim 1, wherein the infrared absorbing substance is a substance having an X—H or X—D (where X = C, N, O) group. .. 3. The object to be measured according to claim 1, wherein the illuminating unit outputs infrared light of at least two wavelengths whose scattering degrees by the surface of the object to be measured and scatterers contained therein are sufficiently approximate. Infrared absorption measuring device. 4. The apparatus for measuring infrared absorption of an object to be measured according to claim 1, wherein the filter is configured by alternately arranging the striped transmission regions for each of the at least two wavelengths. 5. The apparatus for measuring infrared absorption of an object to be measured according to claim 1, wherein the filter l is configured by arranging the dot-shaped transmission regions alternately in a mosaic pattern for each of the at least two wavelengths. .. 6. The filter has a plurality of light-shielding regions arranged in a substantially uniform positional distribution, and the classification unit extracts a scan timing of the light-shielding region from an output of the image sensor. The apparatus for measuring infrared absorption of an object to be measured according to claim 1, wherein the outputs of the plurality of transmission regions are separated for each of the at least two wavelengths based on the scanning timing. 7. The apparatus for measuring infrared absorption of an object to be measured according to claim 1, wherein the classification means classifies outputs of the plurality of transmission regions for each of the at least two wavelengths based on a scanning signal of the image sensor. .. 8. A calculation means for performing a predetermined image calculation between outputs of said at least two wavelengths from said classification means, said output display means outputting and displaying a calculation result of said calculation means. Item 1. A device for measuring infrared absorption of an object to be measured according to item 1.