Optical filter array, multiwavelength sensor, and two-color temperature measurement apparatus

Abstract

To provide an optical filter array having a high degree of freedom of a transmission wavelength, a multiwavelength sensor, and a two-color temperature measurement apparatus.SOLUTION: An optical filter array 12 has a plurality of first bandpass filters F1 transmitting light of a first wavelength and a plurality of second bandpass filters F2 transmitting light of a second wavelength. The first bandpass filters F1 and the second bandpass filters F2 are arranged in a mosaic pattern. The first bandpass filters F1 and the second bandpass filters F2 are interference filters constituted by a multilayer film that is formed such that a high refractive index film having a relatively high refractive index and a low refractive index film having a relatively low refractive index are alternately stacked.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an optical filter array, a multi-wavelength sensor, and a two-color temperature measurement device. [Background technology]

[0002] Two-color temperature measurement devices are known that use a two-color method to obtain the temperature distribution of an object. In two-color temperature measurement devices, images based on the radiance of at least two different wavelengths are obtained. In two-color temperature measurement devices, the radiance ratio between corresponding pixels in each obtained image is converted to temperature, and a thermogram is generated in which each pixel indicates a temperature.

[0003] There are two-sensor type and single-plate type two-color temperature measuring devices (see, for example, Patent Document 1). For example, in a two-sensor type two-color temperature measuring device, incident light is split into two by a beam splitter and imaged on two image sensors in front of which bandpass filters that transmit different wavelengths are arranged. On the other hand, in a single-plate type two-color temperature measuring device, an optical filter in which filters that transmit different wavelengths are arranged in a mosaic pattern in front of one image sensor is arranged as a multi-wavelength sensor. For example, an optical filter array is used in which a color filter that transmits one of the colors R (red), G (green), or B (blue) is arranged in each pixel of an image sensor used in a normal color camera. In such a single-plate type two-color temperature measuring device, for one pixel that receives light of one color, the radiance of the light of the other two colors is interpolated based on the signal from the pixel that receives light of the other color around the pixel to obtain the ratio of the radiance of three colors or two colors. The color filters are formed by applying a color resist, which is a photosensitive resin containing a pigment for coloring, onto glass and then patterning the color resist. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-272278 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned color filters have a problem that the range in which the transmission wavelength can be set is limited and the degree of freedom is low, since the transmission wavelength is set by a color resist in which the color is adjusted by a color pigment. Also, in a multi-wavelength sensor that performs multi-wavelength sensing using an optical filter array, if the above-mentioned color filters are used in the optical filter array, the range in which the transmission wavelength can be set is similarly limited, and the degree of freedom is low.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide an optical filter array, a multi-wavelength sensor, and a two-color temperature measuring device that have a high degree of freedom in terms of transmitted wavelengths. [Means for solving the problem]

[0007] The optical filter array of the present invention comprises a substrate formed of a material that transmits light of a first wavelength and light of a second wavelength different from the first wavelength, a plurality of first bandpass filters provided on one substrate surface of the substrate and transmitting light of the first wavelength, and a plurality of second bandpass filters provided on the other substrate surface and transmitting light of the second wavelength, wherein the first bandpass filters are made of a multilayer film in which a first high refractive index material having a relatively high refractive index and a first low refractive index material having a relatively low refractive index are alternately laminated, and the second bandpass filters are made of a multilayer film in which a second high refractive index material having a relatively high refractive index and a second low refractive index material having a relatively low refractive index are alternately laminated, and the first bandpass filters and the second bandpass filters are arranged one-dimensionally or two-dimensionally in a predetermined pattern. It is something.

[0008] A multi-wavelength sensor of the present invention includes the optical filter array described above, and an image sensor having a plurality of light receiving elements provided corresponding to each of the first bandpass filter and the second bandpass filter.

[0009] The two-color temperature measuring device of the present invention comprises the above-mentioned optical filter array, an image sensor having a plurality of light receiving elements corresponding to each of the first bandpass filter and the second bandpass filter, and acquiring images of an object with light of the first wavelength and the second wavelength as radiance information, respectively, and a processing unit that acquires temperature information of the object based on the radiance information of the first wavelength and the radiance information of the second wavelength acquired from the image sensor. Effect of the Invention

[0010] According to the present invention, a first bandpass filter that transmits light of a first wavelength is a multilayer film formed by alternately stacking a first high refractive index material and a first low refractive index material, and a second bandpass filter that transmits light of a second wavelength is a multilayer film formed by alternately stacking a second high refractive index material and a second low refractive index material, which are provided on a substrate surface. This makes it possible to set the first and second wavelengths, which are the transmission wavelengths of the optical filter array, in a wide range, and to increase the degree of freedom, by changing the thickness of each film constituting each multilayer film, or by changing the refractive indexes of the first high refractive index material, the first low refractive index material, the second high refractive index material, and the second low refractive index material. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing a configuration of a two-color temperature measuring device. [Diagram 2] 4 is a cross-sectional view showing the arrangement of light receiving elements of an image sensor and bandpass filters of an optical filter array. FIG. [Diagram 3] FIG. 2 is an explanatory diagram showing an arrangement of first band-pass filters and second band-pass filters in an optical filter array. [Figure 4] FIG. 2 is a cross-sectional view showing a layer structure of an optical filter array. [Diagram 5] 1 is a graph showing the transmittance of Si, SiO2, Ge, and TiO2. [Figure 6] 1 is a graph showing the refractive indices of Si, SiO2, Ge, and TiO2. [Figure 7]5A to 5C are explanatory views showing a process of forming the first band-pass filter and the second band-pass filter. [Figure 8] 1A to 1C are explanatory diagrams showing a process of forming a black matrix and an anti-reflection film. [Figure 9] 4 is a graph showing the spectral transmittance of exemplary configurations of a first bandpass filter and a second bandpass filter having transmission wavelengths in the near-infrared range. [Figure 10] 1 is a graph showing the spectral transmittance of examples of a bandpass filter having a transmission wavelength in the visible light range. [Figure 11] 11 is a cross-sectional view showing an example in which a black matrix is ​​provided on the surface of the peripheral portion of a second bandpass filter overlapped on the peripheral portion of a first bandpass filter. FIG. [Figure 12] 11 is a cross-sectional view showing an example in which a black matrix is ​​provided in a groove portion at the boundary between a first band-pass filter and a second band-pass filter. FIG. [Figure 13] FIG. 2 is an explanatory diagram showing an example of an optical filter array in which a first bandpass filter and a second bandpass filter are arranged in a striped pattern. [Figure 14] 1 is an explanatory diagram showing an example of an optical filter array in which a first band-pass filter and a second band-pass filter are each circular. FIG. [Figure 15] 11 is a cross-sectional view showing an example in which a first band-pass filter and a second band-pass filter are each provided with a microlens. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In FIG. 1, a two-color temperature measuring device 10 as a multi-wavelength sensing device includes an imaging lens 11, an optical filter array 12, an image sensor 13, a signal processing circuit 14, and a monitor 15. The two-color temperature measuring device 10 acquires the temperature of each part of an object based on the radiance ratio of a first wavelength and a second wavelength that are different from each other, and displays the temperature distribution image on the monitor 15. The first wavelength and the second wavelength may be in the visible light range (wavelength 360 nm to 760 nm) or the infrared range (wavelength 760 nm to 1 mm). In the infrared range, it is preferable to set the wavelength range to the near infrared range (wavelength 750 nm to 2500 nm), and particularly to a wavelength range of 1200 nm to 1700 nm for temperatures of 300° C. to 900° C. In addition, the light will be described as including electromagnetic waves (electromagnetic radiation) such as infrared rays with wavelengths longer than visible light as well as visible light.

[0013] The emissivity of light emitted from an object (heat source) varies depending on the temperature zone and wavelength range. On the other hand, when temperature is obtained from the radiance ratio of light of two wavelengths as in the two-color temperature measurement device 10, it is desirable for the emissivity of the first wavelength and the second wavelength to be close to each other in order to improve sensing accuracy (temperature measurement accuracy) according to the principle of the calculation. When the temperature to be measured is 300°C to 900°C, it is possible to select the first wavelength and the second wavelength, which have similar emissivity, in the above-mentioned wavelength range of 1200 nm to 1700 nm.

[0014] The imaging lens 11 converges light emitted from an object and forms an image of the object on the light receiving surface of the image sensor 13. The imaging lens 11 is preferably made of a material having high transmittance for the first wavelength and the second wavelength.

[0015] The image sensor 13 is an area sensor in which a plurality of light receiving elements 13a (see FIG. 2) are arranged two-dimensionally (in a matrix). That is, the light receiving elements 13a are arranged in a line shape at a constant arrangement pitch in the row direction, and a plurality of rows of the light receiving elements 13a are arranged at a constant arrangement pitch in a column direction perpendicular to the row direction. The light receiving elements 13a are sensitive to light of the first wavelength and the second wavelength. For example, when the first wavelength and the second wavelength are in the infrared region, an InGaAs photodiode or the like having sensitivity to infrared light may be used. When the first wavelength and the second wavelength are in the visible light region, a Si photodiode or the like may be used.

[0016] The optical filter array 12 is disposed in front of the light receiving surface of the image sensor 13, and constitutes a multi-wavelength sensor together with the image sensor 13. As shown in Fig. 2, the optical filter array 12 has a plurality of first bandpass filters F1 that transmit light of a first wavelength and a plurality of second bandpass filters F2 that transmit light of a second wavelength, and these first bandpass filters F1 and second bandpass filters F2 are arranged in a predetermined pattern. Note that the first bandpass filter F1 has a finite transmission band (bandwidth) with the first wavelength as the center wavelength, and the second bandpass filter F2 has a finite transmission band (bandwidth) with the second wavelength as the center wavelength.

[0017] Either a first bandpass filter F1 or a second bandpass filter F2 is disposed in front of one light receiving element 13a. Each light receiving element 13a receives light of a first wavelength transmitted through the first bandpass filter F1, or receives light of a second wavelength transmitted through the second bandpass filter F2, and converts the received light into a detection signal according to the intensity of the received light. The optical filter array 12 and the image sensor 13 obtain the radiance of each part of the object for the first wavelength and the second wavelength. In this way, the image sensor 13 obtains the image of the object for the first wavelength and the second wavelength as radiance information.

[0018] In FIG. 1, the signal processing circuit 14 obtains the temperature of the object based on the detection signal for each light receiving element 13a, that is, for each pixel. The signal processing circuit 14 obtains the ratio between the radiance of the first wavelength and the radiance of the second wavelength obtained from the detection signal for each pixel, and converts the radiance and the ratio into temperature. Since each light receiving element 13a receives either the light of the first wavelength or the light of the second wavelength, the signal processing circuit 14 performs an interpolation process for a pixel of the light receiving element 13a that receives light of the first wavelength, for example, to obtain the average value of the detection signals (radiance) of each pixel of the light receiving element 13a that receives light of the second wavelength around the pixel as the detection signal of the pixel. Similarly, for a pixel of the light receiving element 13a that receives light of the second wavelength, the signal processing circuit 14 performs an interpolation process for obtaining the average value of the detection signals (radiance) of each pixel of the light receiving element 13a that receives light of the first wavelength around the pixel as the detection signal of the pixel.

[0019] In this manner, the signal processing circuit 14 obtains the temperatures of all pixels as temperature information, thereby generating a temperature distribution image showing the temperature distribution of one screen. The temperature distribution image expresses high and low temperatures, for example, by different colors. In this manner, the signal processing circuit 14 as a processing unit obtains temperature information of the object based on the radiance information of the first wavelength and the radiance information of the second wavelength.

[0020] The monitor 15 displays the temperature distribution image generated by the signal processing circuit 14. As the image sensor 13 continuously captures images, the displayed temperature distribution image changes in response to the movement of the object and its temperature change.

[0021] In Fig. 3, the first band-pass filter F1 and the second band-pass filter F2 are arranged in a mosaic pattern. That is, the first band-pass filter F1 and the second band-pass filter F2 are alternately arranged at a constant arrangement pitch in the row direction (left and right direction in Fig. 3) and column direction (up and down direction in Fig. 3) in which the light receiving elements 13a of the image sensor 13 are arranged. The first band-pass filter F1 and the second band-pass filter F2 are rectangular with a side length of, for example, several tens of µm or less. Note that the first band-pass filter F1 and the second band-pass filter F2 are not limited to rectangular shapes.

[0022] In this example, the arrangement pitch of the first bandpass filter F1 and the second bandpass filter F2 in each of the row direction and the column direction is twice the arrangement pitch of the light receiving elements 13a in the image sensor 13. Therefore, one light receiving element 13a corresponds to one first bandpass filter F1 or one second bandpass filter F2. With N and M being integers of 1 or more, each arrangement pitch of the first bandpass filter F1 and the second bandpass filter F2 in the row direction may be 2N times the arrangement pitch of the light receiving elements 13a, and each arrangement pitch in the column direction may be 2M times the arrangement pitch of the light receiving elements 13a, or the arrangement pitch may be different in the row direction and the column direction (N ≠ M). In this case, N rows and M columns of light receiving elements 13a are regarded as one block, and one first bandpass filter F1 or one second bandpass filter F2 is arranged in each block.

[0023] As shown in FIG. 4, the optical filter array 12 has a first bandpass filter F1 and a second bandpass filter F2 formed on one substrate surface 17a of a substrate 17. The substrate 17 is made of a material having high transmittance for light of the first wavelength and the second wavelength. For example, the substrate 17 is made of quartz, sapphire, glass, highly heat-resistant transparent resin, etc. When the first wavelength and the second wavelength are 1.1 μm or more, the substrate 17 can be made of single crystal silicon (Si). In FIG. 4, the optical filter array 12 is drawn with the light receiving surface side of the image sensor 13 facing upward. The same applies to FIGS. 7, 8, 11, 12, and 15. In FIG. 4, hatching other than that of a black matrix 26, which will be described later, is omitted.

[0024] The first bandpass filter F1 and the second bandpass filter F2 are interference filters composed of a multilayer film in which a high refractive index film with a relatively high refractive index and a low refractive index film with a low refractive index are alternately laminated. The first bandpass filter F1 is configured by alternately laminating a first high refractive index film 21a formed of a first high refractive index material and a first low refractive index film 21b formed of a first low refractive index material having a lower refractive index than the first high refractive index material. The second bandpass filter F2 is configured by alternately laminating a second high refractive index film 22a formed of a second high refractive index material and a second low refractive index film 22b formed of a second low refractive index material having a lower refractive index than the second high refractive index material. The high and low refractive indices of the first high refractive index material and the first low refractive index material of the first bandpass filter F1 correspond to a first wavelength, and the high and low refractive indexes of the second high refractive index material and the second low refractive index material of the second bandpass filter F2 correspond to a second wavelength.

[0025] In the first bandpass filter F1, the refractive index and thickness of each of the first high-refractive index films 21a and each of the first low-refractive index films 21b are adjusted so that the first wavelength is the central wavelength. Similarly, in the second bandpass filter F2, the refractive index and thickness of each of the second high-refractive index films 22a and each of the second low-refractive index films 22b are adjusted so that the second wavelength is the central wavelength of the transmission band. The refractive index is adjusted by selecting the refractive index materials as the first high-refractive index material, the second high-refractive index material, the first low-refractive index material, and the second low-refractive index material. The number of layers of the refractive index films of the first bandpass filter F1 and the second bandpass filter F2 is arbitrary, but it is preferable to have six layers or more in order to achieve a narrow half-width of the transmission band and high transmittance.

[0026] As described above, the first bandpass filter F1 can set the first wavelength by adjusting the film thickness and the refractive index of the first high refractive index film 21a and the first low refractive index film 21b, and the second bandpass filter F2 can set the second wavelength by adjusting the film thickness and the refractive index of the second high refractive index film 22a and the second low refractive index film 22b, within a wide wavelength range including the visible light region and the infrared region. In this way, the optical filter array 12 is configured with a high degree of freedom for the first wavelength and the second wavelength. In addition, the first bandpass filter F1 and the second bandpass filter F2 can be made to have a narrow transmission band by adjusting the number of layers, the refractive index, and the film thickness of the refractive index film that constitutes them. This can improve the sensing accuracy, in this example, the measurement accuracy of temperature.

[0027] 4, the first bandpass filter F1 and the second bandpass filter F2 are illustrated as being formed in the order of low refractive index film, high refractive index film, low refractive index film, etc. from the substrate 17 side, but they may be formed in the order of high refractive index film, low refractive index film, high refractive index film, etc. The order of the high refractive index film and the low refractive index film may be reversed between the first bandpass filter F1 and the second bandpass filter F2. The first high refractive index material and the second high refractive index material may be different or the same, and the first low refractive index material and the second low refractive index material may be different or the same.

[0028] When the first wavelength and the second wavelength are set in the infrared region and the visible light region, the first high refractive index material, the first low refractive index material, the second high refractive index material and the second low refractive index material can preferably be, for example, SiO2, TiO2, Y2O3, HfO2, ZrO, Al2O3, MgF2, or CaF.

[0029] As shown in FIG. 5, Si and Ge have high transmittance for infrared rays including near infrared rays of 1.1 μm or more. Therefore, Si and Ge can be preferably used as the first high refractive index material, the first low refractive index material, the second high refractive index material, and the second low refractive index material of the first bandpass filter F1 and the second bandpass filter F2 for such near infrared or infrared regions. As shown in FIG. 5, these Si and Ge have a higher refractive index than SiO2 and TiO2 for infrared rays of 1.1 μm or more. Therefore, Si and Ge can be preferably used as the first high refractive index material and the second high refractive index material having a higher refractive index than SiO2 or TiO2, for example. Si3N4 has a high transmittance for infrared rays of 1.1 μm or more, so it can be preferably used as the first high refractive index material, the first low refractive index material, the second high refractive index material, and the second low refractive index material of the bandpass filter in the infrared region.

[0030] Therefore, for the first and second wavelengths in the visible light range or less than 1.1 μm, SiO2, TiO2, Y2O3, HfO2, ZrO, Al2O3, MgF2, and CaF can be preferably used as the first high refractive index material, the first low refractive index material, the second high refractive index material, and the second low refractive index material. On the other hand, for the first and second wavelengths of 1.1 μm or more, Si, Ge, Si3N4, SiO2, TiO2, Y2O3, HfO2, ZrO, Al2O3, MgF2, and CaF can be preferably used as the first high refractive index material, the first low refractive index material, the second high refractive index material, and the second low refractive index material.

[0031] However, when an optical filter array is constructed using color filters made of color resist as in the conventional method, the color filters absorb a part of the light incident on them, and thus generate heat and the temperature rises. This temperature rise not only causes problems with the heat resistance of the color filters, but also leads to deterioration of the color filters. Furthermore, when an image sensor with high sensitivity in the infrared region is used, this temperature rise in the color filters causes measurement noise in the radiance, increasing measurement errors.

[0032] However, the first bandpass filter F1 and the second bandpass filter F2 configured as described above attenuate and block light outside the transmission band by reflection, so that heat generation is suppressed accordingly. As a result, the first bandpass filter F1 and the second bandpass filter F2 can suppress deterioration due to temperature rise by the amount of heat generation suppressed. Furthermore, since the first bandpass filter F1 and the second bandpass filter F2 can suppress temperature rise, they are less likely to affect the measurement of radiance even when an image sensor 13 having high sensitivity in the infrared range is used, and measurement errors can be reduced. In this way, the configuration using the first bandpass filter F1 and the second bandpass filter F2 is suitable as the optical filter 12 for multi-wavelength sensing.

[0033] The first bandpass filter F1 and the second bandpass filter F2 preferably have a transmittance of 50% or more at the center wavelength in order to increase the S / N of the detection signal output from the image sensor 13. In addition, in order to suppress the incidence of light of different wavelengths, a transmittance of 10% or less is defined as the cut band of the bandpass filter, and the rest is defined as the transmission band, and it is preferable that the transmission band of the first bandpass filter F1 and the transmission band of the second bandpass filter F2 do not overlap. In addition, the lower the transmittance when defining the cut band, the more preferable it is, specifically, 1% or less. In addition, the sum of the thicknesses of the high refractive index films and the low refractive index films constituting each bandpass filter, that is, the thicknesses of the first bandpass filter F1 and the second bandpass filter F2, is preferably thin from the viewpoint of forming a highly precise mosaic pattern, and is preferably 1 / 10 or less of the minimum width of the filter arrangement pattern. In this example, the thicknesses of the first bandpass filter F1 and the second bandpass filter F2 are preferably 2.35 μm or less. The minimum width of the filter arrangement pattern is the length of one side for a square, the length of the short side for a rectangle, the diameter for a circle, and the short axis diameter for an ellipse.

[0034] An anti-reflection film 23 is formed on the other substrate surface 17b of the substrate 17. This anti-reflection film 23 suppresses reflection of light when it propagates inside the substrate 17 and is emitted from the substrate surface 17b. In this example, the anti-reflection film 23 is formed as a single layer film made of a material having a lower refractive index than the substrate 17. The anti-reflection film 23 is preferably made of a material that transmits the first wavelength and the second wavelength, and has a high transmittance for these wavelengths. The anti-reflection film 23 may be a multi-layer film. Both substrate surfaces 17a, 17b are flat surfaces.

[0035] The optical filter array 12 is provided with a black matrix 26 at the boundary between the first bandpass filter F1 and the second bandpass filter F2. In this example, the first bandpass filter F1 and the second bandpass filter F2 are formed adjacent to each other without overlapping each other, and the surface where they contact is the boundary, and the black matrix 26 is formed with a predetermined width on the first bandpass filter F1 and the second bandpass filter F2 so as to cover the boundary (line) on the surface of the optical filter array 12. Therefore, the black matrix 26 is provided around each surface of the first bandpass filter F1 and the second bandpass filter F2. The black matrix 26 is formed of a material having a light-shielding property for the first wavelength and the second wavelength, such as chromium (Cr).

[0036] The black matrix 26 suppresses optical crosstalk. That is, light that passes obliquely through one of the first bandpass filter F1 and the second bandpass filter F2, for example the first bandpass filter F1, is prevented from entering the light receiving element 13a corresponding to the second bandpass filter F2. This improves the accuracy of temperature measurement for each pixel and improves the contrast of the temperature distribution image.

[0037] Next, the manufacturing procedure of the optical filter array 12 will be described with reference to Figures 7 and 8. In manufacturing the optical filter array 12, a first bandpass filter forming process, a second bandpass filter forming process, a black matrix forming process, and an anti-reflection film forming process are performed in this order. Note that the order of each forming process can be changed as appropriate, and for example, the anti-reflection film forming process may be performed before the other forming processes. Also, hatching is omitted in Figures 7 and 8.

[0038] In the first bandpass filter forming process, a first bandpass filter F1 is formed on the substrate surface 17a of the substrate 17. First, a resist is applied to the substrate surface 17a and patterned by photolithography. This exposes the portion of the substrate surface 17a where the first bandpass filter F1 is to be formed, and a resist layer 31 is formed to cover the other portions (step 701). Next, for example, electron beam deposition is performed while alternately exchanging the first high refractive index material and the first low refractive index material as targets. This fabricates the first bandpass filter F1 by alternately stacking the first high refractive index film 21a and the first low refractive index film 21b on the substrate surface 17a (step 702). At this time, the thicknesses of the first high refractive index film 21a and the first low refractive index film 21b are adjusted by, for example, increasing or decreasing the output power of the electron beam. Next, the resist layer 31 and the stack 32 of the first high refractive index material and the first low refractive index material thereon are removed by lift-off. This leaves only the first bandpass filter F1 on the substrate surface 17a (step 703).

[0039] After the first bandpass filter forming process, a second bandpass filter forming process is performed. In the second bandpass filter forming process, a second bandpass filter F2 is formed on the substrate surface 17a. In the second bandpass filter forming process, a resist is applied and a portion of the substrate surface 17a on which the second bandpass filter F2 is to be formed is exposed by photolithography, and a resist layer 33 covering the portion of the first bandpass filter F1 is formed (step 704). Next, electron beam deposition is performed while alternately exchanging the second high refractive index material and the second low refractive index material as targets. As a result, the second high refractive index film 22a and the second low refractive index film 22b are alternately laminated on the substrate surface 17a to fabricate the second bandpass filter F2 (step 705). Next, the resist layer 33 and the laminate 34 of the second high refractive index material and the second low refractive index material thereon are removed by lift-off, leaving the first bandpass filter F1 and the second bandpass filter F2 on the substrate surface 17a (step 706).

[0040] After the second bandpass filter forming process, a black matrix forming process is performed. In this black matrix forming process, a black matrix 26 is formed. First, a resist is applied and a boundary portion of the surfaces of the first bandpass filter F1 and the second bandpass filter F2 is exposed by a predetermined width by photolithography, and a resist layer 35 is formed so as to cover the surfaces of the other first bandpass filter F1 and the second bandpass filter F2 (step 801). Next, the material of the black matrix 26 is evaporated by electron beam evaporation using the resist layer 35 as a mask (step 802). After this, the material 38 of the black matrix 26 is removed together with the resist layer 35 by lift-off. As a result, the black matrix 26 is formed on the surfaces of the first bandpass filter F1 and the second bandpass filter F2 along their boundary (step 803).

[0041] After the black matrix forming process, an anti-reflection film forming process is performed. In the anti-reflection film forming process, the anti-reflection film 23 is formed. In this anti-reflection film forming process, the material of the anti-reflection film 23 is deposited on the entire surface of the substrate surface 17b by electron beam deposition, thereby forming the anti-reflection film 23 (step 804).

[0042] In this example, the first bandpass filter F1, the second bandpass filter F2, and the black matrix 26 are formed by electron beam evaporation, but the formation method is not limited to this, and for example, sputtering or the like may be used.

[0043] Table 1 shows an example of the configuration (material and thickness) of the optical filter array 12 in which the first and second wavelengths are set in the near infrared region. The first bandpass filter F1 has a central wavelength of 1300 nm, and the second bandpass filter F2 has a central wavelength of 1600 nm. FIG. 9 shows the transmission spectra of the first bandpass filter F1 and the second bandpass filter F2 in this configuration example. The layer numbers in Table 1 are numbered in order from the substrate 17 side as 1, 2, 3, etc. The film thicknesses of the first bandpass filter F1 and the second bandpass filter F2 were measured from a TEM (transmission electron microscope) image of a cross section of the optical filter array 12. The correspondence between the transmission spectrum in FIG. 9 and the first bandpass filter F1 and the second bandpass filter F2 is shown by their central wavelengths in Table 1.

[0044] The first bandpass filter F1 and the second bandpass filter F2 of the configuration example shown in Table 1 both have a structure in which SiO2 and Si are alternately stacked, and the first bandpass filter F1 has a total thickness of 2319 nm (2.319 μm), and the second bandpass filter F2 has a total thickness of 1867 nm (1.867 μm).

[0045] [Table 1]

[0046] By using the first bandpass filter F1 and the second bandpass filter F2 that transmit light of the first and second wavelengths in the near-infrared region as described above, it is possible to accurately measure not only temperatures above 900°C, but also temperatures below 900°C (for example, temperatures within the range of 300°C to 900°C). In addition, a single-plate type, i.e., one image sensor 13, receives light of two different wavelengths and obtains the temperature from the radiance ratio of those light. Therefore, unlike a two-sensor type two-color temperature measuring device, there is no influence of sensitivity variations in each image sensor, and measurement errors are unlikely to occur.

[0047] Tables 2 to 4 show configuration examples of bandpass filters that are the first bandpass filter F1 and the second bandpass filter F2, with transmission wavelengths (first wavelength, second wavelength) set in the visible light range. FIG. 10 shows the transmission spectra of these bandpass filters. The center wavelength of the bandpass filter in Table 2 is 450 nm, the center wavelength of the bandpass filter in Table 3 is 550 nm, and the center wavelength of the bandpass filter in Table 4 is 630 nm. The correspondence between the transmission spectra in FIG. 10 and the configuration examples in Tables 2 to 4 is shown by their center wavelengths. The optical filter array 12 for the visible light range can be made by selecting two of the configurations shown in Tables 2 to 4 that are the first bandpass filter F1 and the second bandpass filter F2. The layer numbers in Tables 2 to 4 are numbered in order from the substrate 17 side, as 1, 2, 3, etc.

[0048] [Table 2]

[0049] [Table 3]

[0050] [Table 4]

[0051] 11 shows an example in which the peripheral portion F2a of the second bandpass filter F2 is formed by overlapping the peripheral portion F1a of the first bandpass filter F1, and a black matrix 26A is provided to cover the peripheral portion F2a of the second bandpass filter F2. In this example, the first bandpass filter F1 is provided with the peripheral portion F2a of the adjacent second bandpass filter F2 overlapping the peripheral portion F1a. The overlapping portion of the peripheral portion F1a and the peripheral portion F2a protrudes from the central portions of the first bandpass filter F1 and the second bandpass filter F2, and the black matrix 26A is provided to cover the protruding portion. In this way, the black matrix 26A is provided at the substantial boundary between the first bandpass filter F1 and the second bandpass filter F2. Since the black matrix 26A covers the protruding portion, i.e., the black matrix 26A protrudes, it blocks light incident near the boundary between the first bandpass filter F1 and the second bandpass filter F2, and can block light that enters near the boundary, passes through, and diffuses in the lateral direction (in-plane direction of the first bandpass filter F1 and the second bandpass filter F2), thereby suppressing unnecessary light from entering the image sensor 13. Note that hatching other than that of the black matrix 26A is omitted in Fig. 11.

[0052] In this example, in the second bandpass filter forming process following the first bandpass filter forming process, a resist layer is formed by patterning so as to open larger than the size of the exposed substrate surface 17a when the first bandpass filter F1 is not formed. That is, the resist layer is formed so as to expose the peripheral portion F1a of the first bandpass filter F1. After this, the second high refractive index film 22a and the second low refractive index film 22b are alternately laminated in the opened portion of the resist layer by electron beam deposition or the like.

[0053] In the black matrix forming process, a resist layer is formed by patterning so as to expose the peripheral portion F2a of the second bandpass filter F2 overlapping the peripheral portion F1a of the first bandpass filter F1 and to cover the surfaces of the remaining first bandpass filter F1 and the second bandpass filter F2. Then, the black matrix 26A is formed by electron beam deposition or the like.

[0054] FIG. 12 shows an example in which a groove 37 is formed between the first bandpass filter F1 and the second bandpass filter F2, and a black matrix 26B is provided so as to cover the inner surface of the groove 37. In this example, the adjacent first bandpass filter F1 and second bandpass filter F2 are provided at a predetermined interval. The gap between the first bandpass filter F1 and the second bandpass filter F2 is the groove 37 with the substrate surface 17a as the bottom surface, and the black matrix 26B is provided so as to cover the inner surface of the groove 37, i.e., the substrate surface 17a exposed in the groove 37 and each side surface of the first bandpass filter F1 and the second bandpass filter F2. Note that hatching other than that of the black matrix 26B is omitted in FIG. 12.

[0055] Therefore, the first bandpass filter F1 and the second bandpass filter F2 have the black matrix 26B formed on each side thereof and are surrounded by the black matrix 26B. The black matrix 26B may be provided so as to fill the groove 37, thereby covering the inner surface of the groove 37 with the black matrix 26B. By providing the black matrix 26B in this manner, crosstalk can be more effectively suppressed.

[0056] In this example, in the first bandpass filter forming process and the second bandpass filter forming process, the first bandpass filter F1 and the second bandpass filter F2 are sequentially formed using a resist layer that allows the adjacent first bandpass filter F1 and second bandpass filter F2 to be formed with a gap between them as described above. In the subsequent black matrix forming process, a resist layer 33 is formed so as to expose only the groove portion 37 formed between the first bandpass filter F1 and the second bandpass filter F2, and a black matrix 26B is formed by electron beam deposition or the like.

[0057] Although an example in which two types of refractive index films having different refractive indexes are laminated as the first bandpass filter and the second bandpass filter has been described above, three or more types of refractive index films having different refractive indexes may be laminated.

[0058] The above describes an example of a two-color temperature measuring device using an optical filter array having two types of bandpass filters with different transmission wavelengths (center wavelengths), but the optical filter array and multi-wavelength sensing device are not limited to this.

[0059] The optical filter array 12A shown in FIG. 13 shows an example in which the first bandpass filter F1 and the second bandpass filter F2 are alternately arranged in a shape extending in one direction, i.e., in a stripe shape. In this example, the first bandpass filter F1 and the second bandpass filter F2 are each in a stripe shape extending in the column direction, and are alternately arranged in the row direction at the same arrangement pitch as the light receiving elements 13a. The width (length in the row direction in this example) of the first bandpass filter F1 and the second bandpass filter F2 is the same as the arrangement pitch, which is several tens of μm. Each first bandpass filter F1 corresponds to one column of light receiving elements 13a for the first wavelength, and each second bandpass filter F2 corresponds to one column of light receiving elements 13a for the second wavelength. In the optical filter array 12A, a black matrix may be formed along the boundary between the first bandpass filter F1 and the second bandpass filter F2 adjacent to each other in the row direction.

[0060] The optical filter array 12B shown in FIG. 14 has circular first bandpass filters F1 and second bandpass filters F2 arranged in a mosaic pattern similar to the optical filter array 12 described above. The diameters of the first bandpass filters F1 and second bandpass filters F2 in this example are about several tens of μm, but are smaller than their arrangement pitch. As a result, the adjacent first bandpass filters F1 and second bandpass filters F2 are arranged at a predetermined distance from each other. For the optical filter array 12B in which the adjacent first bandpass filters F1 and second bandpass filters F2 are spaced from each other, it is preferable to provide a black matrix to cover the inner surface of the groove formed between the first bandpass filters F1 and the second bandpass filters F2, for example, as shown in the example of FIG. 12.

[0061] Also, as shown in the example of FIG. 15, a microlens array 41 may be provided. The optical filter array 12C shown in FIG. 15 has a microlens array 41 provided on one surface (the surface on the image sensor 13 side). The microlens array 41 is composed of a plurality of microlenses 41a provided on the surfaces of the first bandpass filter F1 and the second bandpass filter F2, respectively. The microlenses 41a provided on the first bandpass filter F1 collect light transmitted through the first bandpass filter F1 and make it incident on the light receiving element 13a, and the microlenses 41a provided on the second bandpass filter F2 collect light transmitted through the second bandpass filter F2 and make it incident on the light receiving element 13a. The microlens array 41 can be provided on the optical filter array 12 provided with a black matrix in the manner shown in FIG. 11 or FIG. 12. Hatching other than that of the black matrix 26 is omitted in FIG. 15.

[0062] Also, for example, the optical filter array may be arranged such that the first bandpass filter and the second bandpass filter are arranged one-dimensionally, i.e., the first bandpass filter and the second bandpass filter are arranged alternately in a line. Such an optical filter array in which the first bandpass filter and the second bandpass filter are arranged in a line can be applied to an image sensor (line sensor) in which light receiving elements are arranged in a line, and can be used, for example, for measuring the temperature of an object that is conveyed linearly. Three or more types of refractive index films with different refractive indices may be laminated.

[0063] The optical filter array may include three or more types of bandpass filters with different transmission wavelengths (center wavelengths), and may use a metal thin film such as chrome to block light instead of some of the bandpass filters. That is, the first bandpass filter, the second bandpass filter, and the metal light-shielding film may be arranged one-dimensionally or two-dimensionally in a predetermined pattern. Furthermore, the arrangement pattern of each bandpass filter may be determined according to the application of the multi-wavelength sensing device, the target of sensing, the manner of signal processing, and the like. The optical filter array and the image sensor may also be used as a multi-wavelength sensor of a spectroscopic spectrum analyzer that, for example, applies light to an analysis target and measures and analyzes the spectrum of the light transmitted through the target or the light reflected from the target. [Explanation of symbols]

[0064] 10. Two-color temperature measuring device 12, 12A, 12B, 12C Optical filter array 13 Image Sensor 13a Photodetector 17 Substrate 17a Board surface 17b Board surface 21a First high refractive index film 21b First low refractive index film 22a Second high refractive index film 22b Second low refractive index film 23 Anti-reflection coating 26, 26A, 26B Black matrix 37 Groove 41 Microlens Array 41a Micro Lens F1 1st bandpass filter F2 2nd bandpass filter

Claims

1. a substrate formed of a material that transmits light of a first wavelength and light of a second wavelength different from the first wavelength; a plurality of first bandpass filters provided on one substrate surface of the substrate and transmitting light of the first wavelength; a plurality of second bandpass filters provided on the one substrate surface and transmitting light of the second wavelength; Equipped with The first bandpass filter is a multilayer film in which a first high refractive index material having a relatively high refractive index and a first low refractive index material having a relatively low refractive index are alternately laminated, The second band pass filter is a multilayer film in which a second high refractive index material having a relatively high refractive index and a second low refractive index material having a relatively low refractive index are alternately laminated, an optical filter array, in which the first bandpass filter and the second bandpass filter are arranged one-dimensionally or two-dimensionally in a predetermined pattern;

2. The optical filter array according to claim 1 , further comprising a black matrix provided on a surface of a boundary between the first bandpass filter and the second bandpass filter.

3. a peripheral portion of the first band-pass filter is provided so as to overlap a peripheral portion of the second band-pass filter adjacent to the first band-pass filter, The optical filter array according to claim 1 , wherein the second bandpass filter is provided with a black matrix so as to cover a peripheral portion of the second bandpass filter.

4. a groove is formed between the first band-pass filter and the second band-pass filter adjacent to each other, The optical filter array according to claim 1 , wherein the groove is provided with a black matrix so as to cover an inner surface of the groove.

5. the first wavelength and the second wavelength are 1.1 μm or more; The first high refractive index material, the first low refractive index material, the second high refractive index material, and the second low refractive index material are each selected from the group consisting of Si, Ge, and Si. ３ N ４ , SiO ２ , TiO ２ , Y ２ O ３ , HfO ２ , ZrO, Al ２ O ３ , MgF ２ 2. The optical filter array of claim 1, wherein the material is either CaF or CaF.

6. The first wavelength and the second wavelength are wavelengths within the visible light range or the near infrared range of less than 1.1 μm, Each of the first high refractive index material, the first low refractive index material, the second high refractive index material, and the second low refractive index material is SiO ２ , TiO ２ , Y ２ O ３ , HfO ２ , ZrO, Al ２ O ３ , MgF ２ 2. The optical filter array of claim 1, wherein the material is either CaF or CaF.

7. The optical filter array according to claim 1 , wherein the first wavelength and the second wavelength are set within a wavelength range of 1200 nm to 1700 nm.

8. 2. The optical filter array according to claim 1, further comprising an anti-reflection film provided on the other surface of said substrate.

9. The optical filter array of claim 1 , wherein the first bandpass filters and the second bandpass filters are arranged in a mosaic pattern.

10. 2. The optical filter array according to claim 1, which is used in a two-color temperature measurement device that obtains temperature information of an object based on radiance information of the first wavelength and radiance information of the second wavelength obtained from an image sensor, and light that has passed through the first bandpass filter and the second bandpass filter is received by the image sensor.

11. An optical filter array according to any one of claims 1 to 9; an image sensor having a plurality of light receiving elements provided corresponding to each of the first band pass filter and the second band pass filter; A multi-wavelength sensor comprising:

12. An optical filter array according to any one of claims 1 to 9; an image sensor having a plurality of light receiving elements provided corresponding to each of the first band pass filter and the second band pass filter, and configured to obtain images of an object using light of the first wavelength and light of the second wavelength as radiance information; a processing unit that obtains temperature information of the object based on radiance information of the first wavelength and radiance information of the second wavelength obtained from the image sensor; A two-color temperature measuring device comprising:

13. 2. The optical filter array of claim 1, wherein a microlens is provided on each surface of the first bandpass filter and the second bandpass filter, respectively.

14. 2. The optical filter array according to claim 1, wherein the first bandpass filter, the second bandpass filter and the metal light-shielding film are arranged one-dimensionally or two-dimensionally in a predetermined pattern.

Images