Wavelength detection device and confocal measurement device

Abstract

The present invention provides a wavelength detection device (10) provided with: a plurality of optical filters (12a, 12b); a splitting unit (11) which splits light and allows the split light to pass through each of the plurality of optical filters (12a, 12b); a plurality of light receiving elements (13a, 13b) which detect the intensities of different beams of light which have passed through the optical filters, respectively; and a calculation unit (16) which calculates, from the outputs of the plurality of light receiving elements, physical quantities related to the transmittances of the plurality of optical filters, and calculates the wavelengths of the beams of light which have passed through the plurality of optical filters, on the basis of the transmittance characteristics, wherein the transmittance characteristics of the plurality of optical filters have an inclination section in different wavelength ranges of the wavelength range of the object to be measured.

Claims

1. A wavelength detection device, comprising: a plurality of optical filters with different transmittance characteristics and allowing different wavelength ranges of light to pass through, respectively; a splitting unit which splits light and allows the split lights to pass through the plurality of optical filters; a plurality of light receiving elements which detect the intensities of the lights which have passed through each of the plurality of optical filters or are reflected by each of the plurality of optical filters; and a calculation portion which derives a physical quantity related to the transmittances of the plurality of optical filters from the outputs of the plurality of light receiving elements, and derives the wavelengths of the lights which have passed through the plurality of optical filters on the basis of the transmittance characteristic which is a relationship between the physical quantity related to the transmittance and the wavelength of the light for the plurality of optical filters; wherein the transmittance characteristic of each of the plurality of optical filters has an inclination portion in different wavelength ranges of the wavelength range to be measured, and the inclination portions in the transmittance characteristics of the plurality of the optical filters as a whole are arranged so as to cover different wavelength ranges in the wavelength range to be measured without any gap.

2. The wavelength detection device according to claim 1, wherein the physical quantity related to the transmittance is transmittance, and wherein in the transmittance characteristic for each of the plurality of optical filters, the transmittance of each of the optical filters changes between approximately 0 and approximately 1 in the inclination portion.

3. The wavelength detection device according to claim 1, wherein the physical quantity related to the transmittance is transmittance, and wherein the absolute value of at least one inclination of the inclination portion is 0.0033 (1/nm) or more.

4. The wavelength detection device according to claim 1, wherein the plurality of optical filters are configured by dividing one filter plate into a plurality of regions having different transmittance characteristics, and at least one of the plurality of regions having different transmittance characteristics is formed of a transparent plate.

5. The wavelength detection device according to claim 4, wherein the plurality of light receiving elements are arranged on the same substrate so as to be to respectively receive the light transmitted through the plurality of regions.

6. The wavelength detection device according to claim 4, wherein the intensity of the light entering the plurality of optical filters and the transparent plate is non-uniform.

7. A confocal measurement device, comprising: a light source that emits light of a plurality of wavelengths; a chromatic aberration imparting unit for generating chromatic aberration in the light emitted from the light source along an optical axis direction; an objective lens for condensing the light having chromatic aberration generated by the chromatic aberration imparting unit on a measurement object; a pinhole that allows the light focused on the measurement object in the light condensed by the objective lens to pass through; and the wavelength detection device according to claim 1; wherein the confocal measurement device measures a displacement of the measurement object from the wavelength of the light that has passed though the pinhole.

8. A wavelength detection device, comprising: a plurality of optical filters; a splitting unit which splits light and allows the split lights to pass through the plurality of optical filters; a plurality of light receiving elements which detect the intensities of the lights which have passed through each of the plurality of optical filters or are reflected by each of the plurality of optical filters; and a calculation portion which derives a physical quantity related to the transmittances of the plurality of optical filters from the outputs of the plurality of light receiving elements, and derives the wavelengths of the lights which have passed through the plurality of optical filters on the basis of the transmittance characteristic which is a relationship between the physical quantity related to the transmittance and the wavelength of the light for the plurality of optical filters; wherein the transmittance characteristic of each of the plurality of optical filters has an inclination portion in different wavelength ranges of the wavelength range to be measured, wherein among the transmittance characteristics of each of the plurality of optical filters, two or more of the transmittance characteristics consist of curves that periodically change in the wavelength range to be measured and the curves related to each of the transmittance characteristics have different phases.

9. The wavelength detection device according to claim 8, wherein the transmittance characteristics of each of the plurality of optical filters further include a transmittance characteristic consisting of a straight line or a curve that monotonically increases or monotonically decreases in the wavelength range to be measured.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic configuration of a wavelength detection device and a transmittance characteristic of each filter according to an application example of the present invention.

(2) FIG. 2 is a diagram showing a schematic configuration of a confocal measurement device according to an application example of the present invention.

(3) FIG. 3 shows a schematic configuration of a wavelength detection device and a transmittance characteristic of each filter according to Example 1 of the present invention.

(4) FIG. 4 is a diagram showing another example of the transmittance characteristic of each filter according to Example 1 of the present invention.

(5) FIG. 5 shows a transmittance characteristic of each filter and an intensity distribution for each wavelength of a light source according to Example 2 of the present invention.

(6) FIG. 6 shows a transmittance characteristic of each filter according to Example 3 of the present invention.

(7) FIG. 7 is a diagram showing a relationship between the transmittance characteristic and a wavelength distribution in a light source according to the Example 3 of the present invention.

(8) FIG. 8 shows a mode of incidence of light on a filter plate and a relationship between the transmittance and wavelength detection precision when light enters the filter plate non-uniformly according to Example 4 of the present invention.

(9) FIG. 9 explains a conventional basic principle of an optical wavelength monitor device using an optical filter.

DESCRIPTION OF THE EMBODIMENTS

Application Example

(10) Next, an application example of the present invention is described with reference to the drawings. As shown in FIG. 1, in a wavelength detection device 10 of the present application example, the light which enters an incident light fiber 14 is branched into a first branching fiber 14a, a second branching fiber 14b, and a third branching fiber 14c by a branching coupler 11 serving as a splitting unit. Then, the light emitted from each of the first branching fiber 14a, the second branching fiber 14b and the third branching fiber 14c is respectively converted into parallel rays by a first condenser lens 15a, a second condenser lens 15b, and a third condenser lens 15c.

(11) The light that has passed through the first condenser lens 15a passes through a first filter 12a and then is received by a first light receiving element 13a, and the intensity thereof is converted into an electric signal. Similarly, the light that has passed through the second condenser lens 15b passes through a second filter 12b and then is received by a second light receiving element 13b, and the intensity thereof is converted into an electric signal. The light that has passed through the third condenser lens 15c is directly received as reference light by a third light receiving element 13c, and the intensity thereof is converted into an electric signal.

(12) Then, in a calculation device 16 serving as a calculation portion, the intensity of the light received by the first light receiving element 13a is divided by the intensity of the light received by the third light receiving element 13c, and thereby the transmittance of the first filter 12a is calculated and derived. In addition, the intensity of the light received by the second light receiving element 13b is divided by the intensity of the light received by the third light receiving element 13c, and thereby the transmittance of the second filter 12b is calculated and derived.

(13) (b) of FIG. 1 shows a relationship between the transmittance and the wavelength of the first filter 12a and the second filter 12b (hereinafter, also referred to as transmittance characteristic). As shown in (b) of FIG. 1, the first filter 12a has a characteristic that the transmittance sharply changes from 1 to 0 in the wavelength range of 500 nm to 575 nm, and has a characteristic that all the light is allowed to pass through when the wavelength is shorter than 500 nm (transmittance 1) and no light is allowed to pass through when the wavelength is longer than 575 nm (transmittance 0). On the other hand, the second filter 12b has a characteristic that the transmittance sharply changes from 1 to 0 in the wavelength range of 575 nm to 650 nm, and has a characteristic that all the light is allowed to pass through when the wavelength is shorter than 575 nm (transmittance 1) and no light is allowed to pass through when the wavelength is longer than 650 nm (transmittance 0).

(14) Then, in the wavelength detection device 10, the calculation device 16 detects the wavelength of the incident light according to the transmittance of the light that has passed through the first filter 12a and the transmittance of the light that has passed through the second filter 12b. In the example of (b) of FIG. 1, the transmittance of the light that has passed through the first filter 12a is 0, and the transmittance of the light that has passed through the second filter 12b is 0.5. Then, the wavelength λ at which the transmittance of the light that has passed through the second filter 12b is 0.5 is derived. More specifically, the calculation device 16 has a table storing a relationship between the wavelength λ, the transmittance of the first filter 12a, and the transmittance of the second filter 12b, the relationship corresponding to the graph of (b) of FIG. 1. The wavelength 2 of the incident light is derived according to the table and the values of the transmittance of the light that has passed through the first filter 12a and the transmittance of the light that has passed through the second filter 12b.

(15) In the application example, two filters which have transmittance characteristics of having steep inclinations with respect to changes in wavelength in different wavelength ranges of 500 nm to 575 nm and 575 nm to 650 nm are used to detect the wavelength of the incident light. Therefore, it is possible to detect the wavelength in a wide wavelength range of 500 nm to 650 nm by utilizing steep transmittance characteristic. Moreover, in the above application example, the branching coupler 11 splits the incident light into three lights. Besides, the wavelength range to be measured is measured by using transmittance characteristics of two types of filters, but the number of the filter is not limited to two. The number of the filter may be three types or more.

(16) In addition, in the above application example, the absolute value of the inclination is 0.0133 (1/nm), which is a sufficiently steep inclination. In addition, because the transmittance characteristic of the first filter 12a and the transmittance characteristic of the second filter 12b are arranged without any gap with respect to the wavelength, the wavelength detection is possible with respect to the light having any wavelength in the wavelength range (500 nm to 650 nm) to be measured. Furthermore, because the transmittance characteristic of the first filter 12a and the transmittance characteristic of the second filter 12b are distributed from 0 to 1 with respect to the transmittance, a steeper transmittance characteristic can be easily realized.

(17) Next, a confocal measurement device 50 including the wavelength detection device 10 of the present invention is described.

(18) FIG. 2 is a schematic diagram showing the configuration of the confocal measurement device 50 including the wavelength detection device 10. The confocal measurement device 50 shown in FIG. 2 is a measurement device that measures the displacement of the measurement object ob by using a confocal optical system. The confocal measuring device 50 includes a head portion 60 having a confocal optical system, a controller portion 70 optically connected through a light fiber 61, and a monitor portion 80 displaying a signal output from the controller portion 70. The head portion 60 has a diffractive lens 62 serving as a chromatic aberration imparting unit, and generates chromatic aberration along the optical axis direction in the light emitted from a light source 71 described later (for example, a white light source) that emits lights of a plurality of wavelengths. Then, the light having the chromatic aberration generated by the diffractive lens is condensed on the measurement object ob by an objective lens 64.

(19) The light emitted from the light source 71 arranged in the controller portion 70 is guided to the head portion 60 through the light fiber 61. The light fiber 61 is a light path from the head portion 60 to the controller portion 70 and also functions as a pinhole 63. That is, among the light condensed by the head portion 60, the light focused on the measurement object ob is focused on the opening portion of the light fiber 61. Therefore, the light fiber 61 functions as the pinhole 63 that blocks light having a wavelength that is not focused on the measurement object ob and allows light that is focused on the measurement object ob to pass through. By using the light fiber 61 in the light path from the head portion 60 to the controller portion 70, it is not necessary to separately arrange a pinhole.

(20) The confocal measurement device 50 may has a configuration in which a pinhole is separately arranged in the light path from the head portion 60 to the controller portion 70 without using the light fiber 61. The controller portion 70 includes the light source 71, which is a white light source, and the wavelength detection device 10. A white LED can be illustrated as an example of the light source 71, and another light source may be illustrated as long as it is a light source that can emit white light.

(21) That is, in the confocal measurement device 50, chromatic aberration is given to the light having a plurality of wavelengths emitted from the light source 71 in the diffractive lens 62 of the head portion 60, and an image is formed on the measurement object ob. Only the light of the wavelength at which an image is accurately formed on the measurement object ob passes through the opening of the light fiber 61 also serving as the pinhole 63, and reaches the controller portion 70 through the light fiber 61. Then, the wavelength is detected by the wavelength detection device 10. Besides, the controller portion 70 is provided with a displacement calculation portion 73 having a table of the relationship between the wavelength of the reflected light from the measurement object ob and the displacement of the measurement object ob. The displacement of the measurement object ob is calculated according to the wavelength measured by the wavelength detection device 10, and the monitor portion 80 displays the result.

(22) Because the confocal measurement device 50 in the present application example includes the wavelength detection device 10 of the present invention, it is possible to more precisely measure the wavelength of the light imaged and reflected on the measurement object ob. As a result, it is possible to more precisely measure the displacement of the measurement object ob. In addition, the wavelength detection device used in the confocal measurement device 50 is not limited to the wavelength detection device described in the application example, and may be wavelength detection devices described in following embodiment examples.

Example 1

(23) Next, Example 1 of the present invention is described. In the present example, an example is described in which a plurality of filters having different transmittance characteristics are formed on one filter plate, and as for the light receiving element, split light receiving elements obtained by arranging a plurality of light receiving elements on one substrate are used, thereby the structure is further simplified and the number of the inclination portion in the wavelength range to be measured is increased.

(24) The configuration of the wavelength detection device 20 in the present example is shown in FIG. 3. In the present example, the incident light is parallelized by a collimator lens that is not shown. Then, the incident light enters a four-division filter 22 without using a branching coupler. In the four-division filter 22, the incident surface of the filter is divided into four, and filters 22a to 22c having three types of different transmittance characteristics and a transparent plate 22d that allows light of all wavelengths in the wavelength range to be measured to pass through are formed. Then, the light that has been parallelized enters and passes through the four-division filter 22 in a manner of evenly entering the filters 22a to 22c and the transparent plate 22d. Then, in each of light receiving elements 23a to 23d of a four-division light receiving element 23 which is arranged on the rear side, the intensity of the light that has passed through the filters 22a to 22c and the transparent plate 22d is measured.

(25) Then, in the calculation device 26 serving as the calculation portion, the intensity of the light received by the light receiving elements 23a to 23c is divided by the intensity of the light received by the light receiving element 23d, and thereby the transmittance of the light that has passed through the filters 22a to 22c is calculated and derived. Furthermore, in the calculation device 26, the wavelength of the incident light is detected according to the transmittance of the light that has passed through the filters 22a to 22c and the known transmittance characteristic of the filters 22a to 22c. Further, the filters 22a to 22c may be formed on a transparent substrate by evaporation or the like, or may be formed by a color glass filter or a multilayer film filter. Further, in the present example, the filters 22a to 22c and the transparent plate 22d correspond to a plurality of regions. In addition, the configuration in which the light that has been parallelized enters the four-division filter 22 in a manner of evenly entering the filters 22a to 22c and the transparent plate 22d corresponds to the splitting unit.

(26) Here, (b) of FIG. 3 shows the transmittance characteristic of the filters 22a to 22c. In the four-division filter 22, the transmittance characteristic of the filter 22a has a steep inclination portion with respect to the wavelength range of 500 nm to 550 nm. The transmittance characteristic of the filter 22b has a steep inclination portion with respect to the wavelength range of 550 nm to 600 nm. The transmittance characteristic of the filter 22c has a steep inclination portion with respect to the wavelength range of 600 nm to 650 nm. Besides, in each wavelength range, the transmittances of the filters 22a to 22c change from 0 to 1. Thus, in the four-division filter 22 of the present example, the transmittance characteristic of each of the three filters 22a to 22c has an inclination portion in different wavelength ranges. Further, the absolute value of the inclination of each inclination portion is 0.02 (l/nm), which is sufficiently large, and it is possible to detect the wavelength of light precisely.

(27) Alternatively, if the transmittance characteristic of each of the filters 22a to 22c is set to be gentler, it is possible to detect the wavelength of light in a wider wavelength range.

(28) Next, FIG. 4 shows another example of the transmittance characteristic of the filters 22a to 22c to be used in the wavelength detection device 20. In the present example, in the transmittance characteristic of each of the filters 22a to 22c of the four-division filter 22, the inclination portion when the transmittance increases from 0 to 1, and the inclination portion when the transmittance decreases from 1 to 0 are arranged. Accordingly, it is possible to arrange as many inclination portions as twice the number of filters with respect to the wavelength range to be measured. Then, as shown in FIG. 4, more inclination portions can be distributed in the wavelength range to be measured, and it is possible to further increase the measurement precision in the wavelength range.

(29) In addition, as shown in FIG. 4, the transmittance characteristic of the filters 22a to 22c in this case has a flat portion at the peak or the bottom. For example, in the transmittance characteristic of the filter 22a, in the range of 525 nm to 575 nm, there is a portion where the transmittance does not change regardless of the change in wavelength. In the portion, it becomes impossible to detect the wavelength of light from the transmittance of the filter 22a. In contrast, in the present example, due to the inclination portion of the transmittance characteristic of the filter 22b, it is possible to detect the wavelength of light in the wavelength range of 525 nm to 550 nm, and due to the inclination portion of the transmittance characteristic of the filter 22c, it is possible to detect the wavelength of light in the wavelength range of 550 nm to 575 nm. As described above, in the example, at least one of the transmittance characteristics of the three filters 22a to 22c has an inclination portion in the wavelength range to be measured. Therefore, it is possible to detect any wavelength with high precision.

(30) In addition, the filters 22a to 22d in the present example may be installed on the surface of the four-division light receiving element 23, or may be formed directly on the surface of the four-division light receiving element 23 by a method such as evaporation. Further, in the present example, the number of the filter is four including the transparent plate, but the number of the filter is not limited to four. For example, the number of the filter may be three or may be five or more.

Example 2

(31) Next, Example 2 of the present invention is described. In the present example, an example is described in which a four-division filter is used as in the case of Example 1 and the transmittance characteristic of each filter is selected according to the intensity distribution for each wavelength in the light source.

(32) Because the hardware configuration of the present example is the same as that of the wavelength detection device 20 of Example 1, the same symbols are used and the description thereof is omitted. Besides, in the present example, the transmittance characteristic of each of the filters 22a to 22c of the four-division filter 22 is as shown in (a) of FIG. 5. In the present example, the filter 22a has a relatively steep inclination portion in the wavelength range of 500 nm to 535 nm. In addition, the filter 22b has a relatively gentle inclination in the wavelength range of 535 nm to 620 nm. Furthermore, the filter 22c has a relatively steep inclination portion in the wavelength range of 620 nm to 650 nm.

(33) (b) of FIG. 5 shows the intensity distribution of each wavelength of the light source in the wavelength detection device 20. In the intensity distribution, the light intensity is particularly weak in the wavelength range of 520 nm or less and the wavelength range of 620 nm or more. Thus, there is a risk that the SN ratio of the light receiving element 23 becomes low in the wavelength ranges described above.

(34) In contrast, in the present example, by setting the transmittance characteristic of each filter to be the transmittance characteristic as shown in (a) of FIG. 5, there is a particularly steep inclination portion in the wavelength range of 535 nm or less and the wavelength range of 620 nm or more, and the deterioration in the measurement precision of wavelength detection in this portion is suppressed.

(35) As described above, in the present example, by determining and combining inclinations of the transmittance characteristics of the filters 22a to 22c of the four-division filter 22 according to the intensity distribution of each wavelength in the light source, it is possible to detect the wavelength with high precision and little fluctuation in precision regardless of the intensity distribution of the light source.

Example 3

(36) Next, Example 3 of the present invention is described. In the present example, as in Example 2, the hardware configuration is the same as that of the wavelength detection device 20 described in Example 1. In the present example, an example is described in which the filter has a transmittance characteristic that periodically changes in the wavelength range to be measured.

(37) The transmittance characteristics of the filters 22a to 22c of the filter 22 in the present example are shown in FIG. 6. In the present example, the filter 22a and the filter 22b both have a transmittance characteristic in which periodical changes with phases different from each other are made with respect to the change in wavelength. Thus, it is possible to arrange a large number of extremely steep inclination portions in the wavelength range to be measured, and to detect the wavelength with higher precision. Further, because the changes in the transmittance characteristics of the filter 22a and the filter 22b differ in phase from each other, in the wavelength range where the transmittance characteristic of one of the filter 22a and the filter 22b has a small or flat inclination at the peak or the bottom, the transmittance characteristic of the other of the filter 22a or the filter 22b has a steep inclination portion, and it is possible to perform precise wavelength detection by using the transmittance characteristic of either the filter 22a or the filter 22b.

(38) Further, in the present example, the transmittance characteristic of the filter 22c has a characteristic of gently and linearly increasing in the wavelength range to be measured. That is, because the transmittance characteristics of the filter 22a and the filter 22b change periodically, it becomes difficult to determine on which number of cycle of the inclination portion is the transmittance based. At this time, by measuring the transmittance in combination with the transmittance of the filter 22c, it is possible to determine whether the transmittance is measured based on which number of cycle of the inclination portion.

(39) As described above, in the present example, first, because the transmittance characteristics having periodic and steep inclination portions are adopted in two filters, it is possible to distribute a larger number of inclination portions in the wavelength range to be measured, and it is possible to improve the wavelength detection precision. In addition, a phase difference is arranged in the periodic transmittance characteristics of the two filters, and in the wavelength range where the transmittance characteristic of one filter has a small or flat inclination at the peak or the bottom, the transmittance characteristic of the other filter has an inclination portion. Furthermore, by combining with a filter that has a transmittance characteristic that monotonously decreases or monotonically increases gently in the wavelength range to be measured, it is possible to determine whether the transmittance is measured based on which cycle of the inclination portion. According to the above, it is possible to detect the wavelength in a wider wavelength range with higher precision.

(40) (b) of FIG. 6 shows a simulation result of actual transmittance characteristics of the filter 22a and the filter 22b. As described above, it is known that as the actual transmittance characteristic of the filter, a characteristic that periodically changes can be sufficiently realized. The filter can be realized by using an etalon or the like constructed according to the principle of Fabry-Perot interferometer.

(41) Further, it is desirable that the half width at the peak portion of the transmittance characteristic of the filter in the present example is larger than the half width of the wavelength distribution of the light source, as shown in FIG. 7. Otherwise, the wavelength distribution of the light source is applied to an adjacent cycle in the transmittance characteristic of the filter, and it is difficult to perform accurate measurement. By satisfying the condition, it becomes possible to perform more precise wavelength measurement even if the light source has a certain wavelength distribution.

(42) Moreover, the transmittance characteristic that periodically changes in the present example may be a sinusoidal change, a trapezoidal change or a triangular wave change. Even in a case that the triangular wave change is adopted as the transmittance characteristic, a sharp change may not always be achieved at the top or the bottom, and thus phases of periodic changes in transmittance characteristics of two filters should be different. Further, in the present example, the waveform or the cycle of the transmittance characteristics of the two filters may be changed.

Example 4

(43) Next, Example 4 of the present invention is described. In the present example, the hardware configuration is also the same as that of the wavelength detection device 20 described in Example 1. In the present example, an example is described in which the four-division filter 22 is used and the entering of the incident light is made non-uniform with respect to the four filters 22a to 22d.

(44) Here, in a case where the wavelength detection is performed by the wavelength detection device 20, when the light enters toward the direction or the opposite direction of the transparent plate 22d with shifting from the center of the four-division filter 22, the precision of the wavelength detection can be expressed as in equation (2) below.

(45) $\begin{array}{cc}\left[\mathrm{Mathematical}\mathrm{formula}2\right]& \\ {\sigma }_{\lambda }={\sigma }_T{.Math.\frac{\mathrm{dT}}{d\lambda }.Math.}^{-1}=\frac{1}{\mathrm{SN}}\sqrt{1/{\alpha }^2+T^2}{.Math.\frac{\mathrm{dT}}{d\lambda }.Math.}^{-1}& \left(2\right)\end{array}$
Here, σ.sub.λ represents the wavelength detection precision, and σ.sub.T represents the variation in transmittance. In addition, α is a light amount division ratio which is a ratio between the light amount applied to the filter 22a and the light amount applied to the transparent plate 22d (light amount applied to filter 22a/light amount applied to transparent plate 22d) when the incident position of light on the four-division filter 22 is shifted in the direction of the transparent plate 22d or in the opposite direction (direction of the filter 22a) as shown in (a) of FIG. 8. In addition, dT/dλ represents the inclination in the transmittance characteristic of the filter, T represents the transmittance, and SN represents the SN ratio of the received signal at the light receiving element 23d that receives the light transmitted through the transparent plate 22d.

(46) In this way, the wavelength precision is affected by the light amount division ratio α. (b) of FIG. 8 is a diagram showing the relationship between the transmittance and the wavelength detection precision with the light amount division ratio α as a parameter. In (b) of FIG. 8, the horizontal axis represents the transmittance T and the vertical axis represents the wavelength detection precision σ.sub.λ, and the wavelength detection precision σ.sub.λ is a numerical value that is higher in precision as the numerical value decreases. As shown in (b) of FIG. 8, compared with the case where the light amount division ratio α is 1, that is, the light enters the filter 22a and the transparent plate 22d evenly, when α is increased, it is possible to improve the wavelength detection precision in the region where the transmittance is low. Further, by reducing α, it is possible to reduce the change in wavelength detection precision caused by the transmittance. Thus, by intentionally irradiating the four filters 22a to 22d including the transparent plate with light unevenly, it is possible to appropriately control the wavelength detection precision.

(47) In addition, in the above examples, examples have been described in which the physical quantity related to the transmittance is the transmittance and the light that has passed through the filters 12a, 12b, 22a to 22d is received by the light receiving elements. However, in the above examples, the light that has been reflected in the filters 12a, 12b, 22a to 22d may be received by the light receiving elements, and the physical quantity related to the transmittance may be detected from the intensity of the reflected light. In this case, the physical quantity related to the transmittance may be reflectance, or the transmittance may be obtained by subtracting the reflectance from 1 or the like.

(48) In addition, in order to make it possible to compare constitutional requirements of the present invention with constitutions of the examples, the constitutional requirements of the present invention are described with reference to symbols in the drawings.

(49) <Invention 1>

(50) A wavelength detection device (10), including:

(51) a plurality of optical filters (12a, 12b);

(52) a splitting unit (11) which splits light and allows the split lights to pass through the plurality of optical filters (12a, 12b);

(53) a plurality of light receiving elements (13a, 13b) which detect the intensities of the lights which have passed through each of the plurality of optical filters (12a, 12b) or are reflected by each of the plurality of optical filters (12a, 12b); and

(54) a calculation portion which derives a physical quantity related to the transmittances of the plurality of optical filters (12a, 12b) from the outputs of the plurality of light receiving elements (13a, 13b), and derives the wavelengths of the lights which have passed through the plurality of optical filters (12a, 12b) on the basis of the transmittance characteristic which is a relationship between the physical quantity related to the transmittance and the wavelength of the light for the plurality of optical filters (12a, 12b);

(55) wherein the transmittance characteristic of each of the plurality of optical filters (12a, 12b) has an inclination portion in different wavelength ranges of the wavelength range to be measured.

(56) <Invention 2>

(57) The wavelength detection device according to Invention 1, wherein the physical quantity related to the transmittance is transmittance, and

(58) wherein in the transmittance characteristic for each of the plurality of optical filters (12a, 12b), the transmittance of each of the optical filters (12a, 12b) changes between approximately 0 and approximately 1 in the inclination portion.

(59) <Invention 3>

(60) The wavelength detection device according to Invention 1 or 2, wherein the physical quantity related to the transmittance is transmittance, and

(61) wherein the absolute value of at least one inclination of the inclination portion is 0.0033 (1/nm) or more.

(62) <Invention 4>

(63) The wavelength detection device according to any one of Inventions 1 to 3, wherein the inclination portion in the transmittance characteristic of each of the plurality of optical filters (12a, 12b) is arranged so as to cover the wavelength range to be measured without any gap.

(64) <Invention 5>

(65) The wavelength detection device according to any one of Inventions 1 to 4, wherein among the transmittance characteristics of each of the plurality of optical filters (12a, 12b), two or more of the transmittance characteristics consist of curves that periodically change in the wavelength range to be measured and the curves related to each of the transmittance characteristics have different phases.

(66) <Invention 6>

(67) The wavelength detection device according to Invention 5, wherein the transmittance characteristics of each of the plurality of optical filters (12a, 12b) further include a transmittance characteristic consisting of a straight line or a curve that monotonically increases or monotonically decreases in the wavelength range to be measured.

(68) <Invention 7>

(69) The wavelength detection device according to any one of Inventions 1 to 6, wherein the plurality of optical filters are configured by dividing one filter plate (22) into a plurality of regions (22a to 22d) having different transmittance characteristics, and at least one of the plurality of regions (22a to 22d) having different transmittance characteristics is formed of a transparent plate (22d).

(70) <Invention 8>

(71) The wavelength detection device according to Invention 7, wherein the plurality of light receiving elements (23a to 23d) are arranged on the same substrate (23) so as to be able to respectively receive the light transmitted through the plurality of regions.

(72) <Invention 9>

(73) The wavelength detection device according to Invention 7 or 8, wherein the intensity of the light entering the plurality of optical filters (22a to 22c) and the transparent plate (22d) is non-uniform.

(74) <Invention 10>

(75) A confocal measurement device (50), including:

(76) a light source (71) that emits light of a plurality of wavelengths;

(77) a chromatic aberration imparting unit (62) for generating chromatic aberration in the light emitted from the light source (71) along an optical axis direction;

(78) an objective lens (64) for condensing the light having chromatic aberration generated by the chromatic aberration imparting unit (62) on an measurement object;

(79) a pinhole (63) that allows the light focused on the measurement object in the light condensed by the objective lens (64) to pass through; and

(80) the wavelength detection device (10) according to any one of Inventions 1 to 9;

(81) wherein the confocal measurement device (50) measures a displacement of the measurement object from the wavelength of the light that has passed through the pinhole (63).