JP6775196B2 - Photodetector - Google Patents

Description

The present disclosure relates to a photodetector including an interfering element.

A device that measures the shape and distance of an object with high accuracy and non-contact by utilizing the interference phenomenon of light has been put into practical use. Generally, in such a device, the light reflected or transmitted through an object (object light) and the light reflected by a reference surface (reference light) are made to interfere with each other, and the generated interference light is imaged and observed. When the flatness of the reference surface is sufficiently guaranteed, the interference fringes of the interference light are generated corresponding to the optical path length of the object light. Since the interference fringes of one period are generated by the change of the optical path length corresponding to the wavelength of light, the three-dimensional shape of the measurement target surface of the object can be obtained from the pattern of the interference fringes.

Differences in optical path lengths above the wavelength of light occur as repeated interference fringes. If the measurement target surface of the object is smooth, it is possible to estimate the difference in the optical path length exceeding the wavelength of light by counting the number of the interference fringes.

When there is a step exceeding the wavelength on the measurement target surface of the object, the interference fringes are missing at the step portion, so that the difference in the optical path length cannot be obtained correctly. A two-wavelength interferometry is known as a method for measuring the shape of an object in such a case. The two-wavelength interferometry is described in, for example, Patent Document 1 and Non-Patent Document 1.

The two-wavelength interferometry measures interference using light of two wavelengths. Images of interference fringes due to light of each wavelength are taken independently or simultaneously, and the shape of the measurement target surface of the object is obtained based on the interference fringe information of both wavelengths. Assuming that the two wavelengths are λ ₁ and λ ₂ , it is known that the effective measurement wavelength λ _eff by the two-wavelength interferometry is as follows.

For example, when λ ₂ = 1.1 × λ ₁ , λ _eff = 11 × λ ₁ , and a larger step can be estimated correctly.

Japanese Unexamined Patent Publication No. 10-220132

You-Yen Change and James C.I. Wyant: "Two-wavelength phase shifting interferometry", Applied Optics, vol. 23, No. 14, P4539-4543

An exemplary, but not limited, embodiment of the present disclosure provides a photodetector having smaller optical portions and less sensitive to the surrounding environment.

The photodetector according to one aspect of the present disclosure includes an image sensor including a plurality of first pixels, a plurality of second pixels, a plurality of third pixels, and a plurality of fourth pixels, a plurality of first incident regions, and a plurality of first incident regions. An interference element having a second incident region and light in the first wavelength band are incident on the plurality of first incident regions, and light in a second wavelength band different from the first wavelength band is incident on the plurality of second incident regions. It is provided with an optical system for incident. The interfering element interferes with a part of the light in the first wavelength band incident on the two first incident regions adjacent to each other among the plurality of first incident regions, and causes the interfered light to interfere with the plurality of first incident regions. The other part of the light in the first wavelength band incident on any of the two first incident regions is guided to one of the plurality of second pixels, and the plurality of second incident regions are guided. Of these, a part of the light in the second wavelength band incident on the two adjacent second incident regions is made to interfere with each other, and the interfered light is guided to one of the plurality of third pixel groups, and the two The other part of the light in the second wavelength band incident on the second incident region is guided to any of the plurality of fourth pixels.

According to the present disclosure, it is possible to realize a photodetector having a smaller optical portion and less susceptible to the influence of the surrounding environment.

Schematic diagram of the configuration of the photodetector according to the first embodiment of the present disclosure. The figure which shows the specific example of the optical system which concerns on 1st Embodiment of this disclosure. The figure which shows another specific example of the optical system which concerns on 1st Embodiment of this disclosure. The figure which shows another specific example of the optical system which concerns on 1st Embodiment of this disclosure. The figure which shows another specific example of the optical system which concerns on 1st Embodiment of this disclosure. The figure which shows another specific example of the optical system which concerns on 1st Embodiment of this disclosure. The figure which shows still another specific example of the optical system which concerns on 1st Embodiment of this disclosure. The figure which shows still another specific example of the optical system which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the incident area group which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the incident area group which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the incident area group which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the incident area group which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the incident area group which concerns on 1st Embodiment of this disclosure. The figure which shows the specific example of the interference element which concerns on 1st Embodiment of this disclosure. The figure which shows the specific example of the interference element which concerns on 1st Embodiment of this disclosure. The figure which shows the specific example of the interference element which concerns on 1st Embodiment of this disclosure. The figure which shows the specific example of the interference element which concerns on 1st Embodiment of this disclosure. The figure which shows another specific example of the interference element which concerns on 1st Embodiment of this disclosure. The figure which shows another specific example of the interference element which concerns on 1st Embodiment of this disclosure. The figure which shows another specific example of the interference element which concerns on 1st Embodiment of this disclosure. The figure which shows another specific example of the interference element which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the pixel group which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the pixel group which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the pixel group which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the pixel group which concerns on 1st Embodiment of this disclosure. The figure which shows the arrangement example of the pixel group which concerns on 1st Embodiment of this disclosure. The figure which shows the output example of the light intensity signal which concerns on 1st Embodiment of this disclosure. The figure which shows the specific example of the arithmetic unit which concerns on 1st Embodiment of this disclosure. Schematic diagram of the configuration of the photodetector according to the second embodiment of the present disclosure. Schematic diagram of the configuration of the photodetector according to the third embodiment of the present disclosure. The figure which shows the structure of the interference element which concerns on embodiment of this disclosure. The figure which shows the relationship between the phase difference of incident light and the intensity of interference light and transmitted light which concerns on embodiment of this disclosure. The figure which shows the shape of the object (sample) to be measured which concerns on 1st Example of this disclosure. The figure which shows the shape of the object (sample) to be measured which concerns on 1st Example of this disclosure. The figure which shows the intensity of the light incident on each pixel of the 1st pixel group which concerns on 1st Example of this disclosure. The figure which shows the intensity of the light incident on each pixel of the 2nd pixel group which concerns on 1st Example of this disclosure. The figure which shows the intensity of the light incident on each pixel of the 3rd pixel group which concerns on 1st Example of this disclosure. The figure which shows the intensity of the light incident on each pixel of the 4th pixel group which concerns on 1st Example of this disclosure. The figure which shows the distribution of the phase difference absolute value at the center wavelength λ _{1 which} concerns on _1st Example of this disclosure. The figure which shows the distribution of the phase difference absolute value at the center wavelength λ ₂ which concerns on 1st Example of this disclosure. The figure which shows the distribution of the phase difference value at the center wavelength λ _{1 which} concerns on _1st Example of this disclosure. The figure which shows the distribution of the phase difference value at the center wavelength λ ₂ which concerns on 1st Example of this disclosure. The figure which shows the distribution of the phase difference value at the equivalent wavelength λ _{eff2 which concerns} on 1st Example of this disclosure. The figure which shows the distribution of the phase value at the equivalent wavelength λ _{eff2 which concerns} on 1st Example of this disclosure. The figure which shows the distribution of the phase value at the center wavelength λ _{1 which} concerns on _1st Example of this disclosure. The figure which shows the distribution of the phase value at the center wavelength λ ₂ which concerns on 1st Example of this disclosure. The figure which shows the sample shape restored at the equivalent wavelength λ _eff2 which _concerns on 1st Example of this disclosure. The figure which shows the sample shape restored at the center wavelength λ ₁ which concerns on _1st Example of this disclosure. The figure which shows the sample shape restored at the center wavelength λ ₂ which concerns on 1st Example of this disclosure. The figure which shows the shape of the object (sample) to be measured which concerns on 2nd Example of this disclosure. The figure which shows the relationship between the step of the object to be measured at the center wavelength λ ₁ and the intensity of interference light and transmitted light which concerns on 2nd Example of this disclosure. The figure which shows the relationship between the step of the object to be measured at the center wavelength λ ₂ and the intensity of interference light and transmitted light which concerns on 2nd Example of this disclosure. The figure which shows the relationship between the step of the object to be measured at the center wavelength λ _eff and the interference light intensity which concerns on 2nd Example of this disclosure The figure which shows the relationship between the step of the object to be measured at the center wavelength λ _eff and the transmitted light intensity which concerns on 2nd Example of this disclosure. The figure which shows an example of the relationship between an illumination light and a bandpass filter Diagram showing another example of the relationship between illumination light and a bandpass filter

(Background to one aspect of this disclosure)
The present disclosure relates to a photodetector that acquires information related to the shape and distance of an object as an image by utilizing the light interference phenomenon. In particular, the present invention relates to a photodetector capable of measuring a step or a change in shape exceeding a wavelength with high accuracy as an image. The present inventors have examined in detail the conventional photodetectors disclosed in Patent Document 1 and Non-Patent Document 1. According to the photodetectors disclosed in these documents, a half mirror for generating interference light is indispensable, and an image pickup tube or an image pickup element may be required for each wavelength. Therefore, it is considered that there is a limit to miniaturizing the optical system in the photodetector. In addition, since the optical path exists in a predetermined space, it is considered that it is easily affected by changes in the surrounding environment such as air convection and vibration of the optical system.

In view of these problems, the present inventors have conceived a new photodetector that can reduce the size of the optical system and is not easily affected by the surrounding environment.

The light detection device of one aspect of the present disclosure includes an image sensor including a plurality of first pixels, a plurality of second pixels, a plurality of third pixels, and a plurality of fourth pixels, a plurality of first incident regions, and a plurality of first. An interference element having two incident regions and light in the first wavelength band are incident on the plurality of first incident regions, and light in a second wavelength band different from the first wavelength band is incident on the plurality of second incident regions. It is equipped with an optical system to make it work. The interfering element interferes with a part of the light in the first wavelength band incident on the two first incident regions adjacent to each other among the plurality of first incident regions, and causes the interfered light to interfere with the plurality of first incident regions. The other part of the light in the first wavelength band incident on any of the two first incident regions is guided to one of the plurality of second pixels, and the plurality of second incident regions are guided. Of these, a part of the light in the second wavelength band incident on the two adjacent second incident regions is made to interfere with each other, and the interfered light is guided to one of the plurality of third pixel groups, and the two The other part of the light in the second wavelength band incident on the second incident region is guided to any of the plurality of fourth pixels.

Here, the "light in the first wavelength band" is light having any wavelength included in the first wavelength band. Further, the "light in the second wavelength band" is light having any wavelength included in the second wavelength band. Therefore, the light in the first and second wavelength bands may be light having a single wavelength or light having a predetermined bandwidth.

The light detection device obtains the first phase difference information from the light intensity information detected by the plurality of first pixels and the light intensity information detected by the plurality of second pixels, and the light intensity detected by the plurality of third pixels. An arithmetic circuit that obtains the second phase difference information from the information and the light intensity information detected by the plurality of fourth pixels may be further provided.

From the first phase difference information and the second phase difference information, the arithmetic circuit obtains phase difference information at equivalent wavelengths of the first wavelength included in the first wavelength band and the second wavelength included in the second wavelength band. You may ask.

The interference element may include a plurality of optical coupling layers, and each of the plurality of optical coupling layers may include a waveguide layer having a diffraction grating.

The interference element may have a first light-shielding region located between the two first incident regions and a second light-shielding region located between the two second incident regions. The plurality of optical coupling layers include the two first incident regions and the first light-shielding region, or the photo-bonding layers located corresponding to the two second incident regions and the second light-shielding region. May be good. The plurality of second pixels may include two second pixels located corresponding to the two first incident regions. The plurality of first pixels may include a first pixel located corresponding to the first shading region. The plurality of fourth pixels may include two fourth pixels located corresponding to the two second incident regions. The plurality of third pixels may include a third pixel located corresponding to the second shading region.

The interference element may include a first light propagation path, a second light propagation path, and a third light propagation path connecting the first light propagation path and the second light propagation path.

The first light propagation path includes an incident portion in which light from one of the two first incident regions or one of the two second incident regions is incident, and a part of the incident light in the plurality of second incident regions. An exiting portion that emits light to any of the pixels or any of the plurality of fourth pixels may be provided. The second light propagation path includes an incident portion where light from the other of the two first incident regions or the other of the two second incident regions is incident, and a part of the incident light is the plurality of second incident regions. An exiting portion that emits light to any of the pixels or any of the plurality of fourth pixels may be provided.

The interference element further includes a fourth light propagation path, and the fourth light propagation path includes an incident portion connected to the third light propagation path and the plurality of first pixels of light incident from the incident portion. It may be provided with an exiting portion that emits light to any one of the above or any of the plurality of third pixels.

The optical system is a filter array having a plurality of first bandpass filters that selectively transmit light in the first wavelength band and a plurality of second bandpass filters that selectively transmit light in the second wavelength band. May include.

The optical system includes a first bandpass filter that selectively transmits light in the first wavelength band, a second bandpass filter that selectively transmits light in the second wavelength band, and the first bandpass. The light of the first wavelength band transmitted through the filter is incident on the plurality of first incident regions, and the light of the second wavelength band transmitted through the second bandpass filter is incident on the plurality of second incident regions. It may be provided with an array-shaped optical element for incident.

The photodetector of another aspect of the present disclosure includes an image pickup element including a plurality of fifth pixels and a plurality of sixth pixels, an interference element including a plurality of fifth incident regions, light in a first wavelength band, and the first wavelength band. It is provided with an illumination that emits light in a second wavelength band different from the one wavelength band. The interfering element interferes with a part of the light of the first wavelength band incident on the two adjacent fifth incident regions of the plurality of fifth incident regions, and causes the interfered light to interfere with the plurality of third incident regions. The other part of the light in the first wavelength band incident on the two fifth incident regions is guided to one of the five pixels and guided to one of the plurality of sixth pixels, and the two fifth incident regions are guided. A part of the light of the second wavelength band incident on the second wavelength band is interfered with, and the interfered light is guided to any of the plurality of fifth pixels, and the second wavelength band incident on the two fifth incident regions. The other part of the light is guided to any of the plurality of sixth pixels.

The illumination may simultaneously emit light in the first wavelength band and light in the second wavelength band. The illumination may emit light in the first wavelength band and light in the second wavelength band in a time-division manner.

The first, second and third light propagation paths may be composed of photonic crystals. The first, second, third and fourth light propagation paths may be composed of photonic crystals.

Hereinafter, embodiments of the photodetector according to the present disclosure will be specifically described with reference to the drawings.

(Outline of the first embodiment)
FIG. 1 is a schematic diagram showing an outline of the configuration of the photodetector according to the first embodiment of the present disclosure. The photodetector includes an optical system 101, an interference element 106, and an image pickup element 109. For the sake of explanation, the interference element and the image pickup element are shown in cross section in this figure. Further, in order to facilitate understanding of the figures, the directions of the three axes in the xyz direction (left-handed system) are also shown in each of the figures after FIG. Specific examples of each component will be described later.

The image pickup device 109 includes first, second, third, and fourth pixel groups 110, 111, 112, and 113 having a plurality of pixels, respectively. The reflected light from the object whose three-dimensional shape and distance are to be accurately measured is incident on the optical system 101 as incident light.

The optical system 101 causes the light 102 in the first wavelength band and the light 103 in the second wavelength band to enter the interference element 106. The interference element 106 includes a first incident region group 104 and a second incident region group 105, each having a plurality of incident regions. The optical system 101 mainly causes the light 102 in the first wavelength band to be incident on the first incident region group 104 of the interference element 106. Further, the optical system 101 mainly causes the light 103 in the second wavelength band to be incident on the second incident region group 105.

Here, the light 103 in the second wavelength band has a central wavelength different from that of the light 102 in the first wavelength band. Further, it is more preferable that the band of the light 103 in the second wavelength band and the band of the light 102 in the first wavelength band do not overlap, because the step and shape of the object can be obtained more accurately. Further, it is more preferable that the bandwidths of the light 102 in the first wavelength band and the light 103 in the second wavelength band are 20 nm or less, respectively, because the central wavelengths of the light in the two wavelength bands can be brought closer to each other and the measurement range can be expanded. It is more preferable if it is 5 nm or less.

The first incident region group 104 and the second incident region group 105 existing in the interference element 106 need only have an opening through which light can be transmitted, and may not have a physical structure. Further, the first incident region group 104 and the second incident region group 105 may be physically the same. The reason why the "first" incident region group and the "second" incident region group are described separately in the present specification is that the properties of the light incident on each incident region group are different.

Of the light incident on the first incident region group 104, a part of the light incident from at least one pair of adjacent incident regions interferes with each other in the interference element 106 and is radiated to the image sensor 109 side as interference light 107. Let me. Further, another part of the light incident from the pair of incident regions is directly radiated to the image sensor 109 side as transmitted light 108 without interfering with each other. The light incident on the second incident region group 105 is also radiated to the image sensor 109 side as interference light 107 and transmitted light 108 in the same manner as the light incident on the first incident region group 104.

It is desirable that the distance between the interference element 106 and the image pickup element 109 is close to each other in order for the interference light 107 and the transmitted light 108 to be efficiently incident on each pixel of the image pickup element (that is, to increase the coupling efficiency). The distance is preferably 100 μm or less, and more preferably 10 μm or less.

The interference light 107 generated from the light 102 in the first wavelength band is mainly guided to the first pixel group 110 in the image sensor 109, and the transmitted light 108 is mainly guided to the second pixel group 111. Similarly, the interference light 107 and the transmitted light 108 generated from the light 103 in the second wavelength band are mainly guided to the third pixel group 112 and the fourth pixel group 113, respectively.

Here, the first to fourth pixel groups 110 to 113 may be any photodetector such as a photodiode, and all of them may be detectors having the same physical structure. The reason why the "first" to "fourth" pixel groups are described separately in this specification is that the properties of the light incident on each pixel group are different.

The photodetector further includes a first arithmetic unit 114, a second arithmetic unit 115, and a third arithmetic unit 118 in order to process the electrical signal obtained from the image sensor 109. The intensity information of the light incident on the first pixel group 110 and the second pixel group 111 is input to the first calculation unit 114 as an electric signal. The first calculation unit 114 calculates and outputs the first phase difference information 116 based on the input signal. This corresponds to the phase difference information with respect to the central wavelength of the first wavelength band (that is, λ _{1 of the} conventional example).

Similarly, the intensity information of the light incident on the third pixel group 112 and the fourth pixel group 113 is input to the second calculation unit 115 as an electric signal. The second calculation unit 115 calculates and outputs the second phase difference information 117 based on the input signal. This corresponds to the phase difference information with respect to the central wavelength of the second wavelength band (that is, λ _{2 in the} conventional example).

The third calculation unit 118 calculates and outputs equivalent phase difference information 119 (that is, phase difference information with respect to λ _{eff in the} conventional example) based on the first phase difference information 116 and the second phase difference information 117.

With such a configuration, it is possible to realize a photodetector having a smaller optical portion, less susceptible to the influence of the surrounding environment, and capable of measuring the shape of an object having a step exceeding the wavelength of light without error.

(Specific configuration example of optical system)
Next, a specific configuration example of the optical system 101 will be described with reference to FIGS. 2 and 3A to 3F.

FIG. 2 includes a filter array as part of the optical system 101. The filter array includes a plurality of first bandpass filters 201 and a plurality of second bandpass filters 202 arranged close to the light incident side of the interference element 106. The first bandpass filter 201 has a wavelength characteristic of transmitting light in the first wavelength band, and is arranged adjacent to the first incident region group 104. The second bandpass filter 202 has a wavelength characteristic of transmitting light in the second wavelength band, and is arranged adjacent to the second incident region group 105. The bandpass filter is manufactured, for example, by forming a dielectric multilayer film or a pigment. In the optical system 101, the region where the bandpass filter does not exist is preferably a light-shielding region.

3A to 3D show an example in which the optical system 101 includes a bandpass filter and an array-shaped optical element provided in the vicinity of the pupil region. The optical system 101 includes a diaphragm 306 having a pupil region, a filter array 307, a lens 304, and an array-shaped optical element 305. FIG. 3A shows an outline of the configuration of the optical system 101, and FIG. 3B shows a planar structure of the filter array 307. FIG. 3C is a schematic perspective view of the array-shaped optical element 305, and FIG. 3D schematically shows light transmitted through the optical system 101 and incident on the interference element 106.

As shown in FIGS. 3A and 3B, the pupil region of the diaphragm 306 is divided into regions D1 and D2 by a plane extending in the horizontal direction including the optical axis V of the optical system 101. The filter array 307 includes a second bandpass filter 303 arranged in the region D2 and a first bandpass filter 302 arranged in the region D1.

The incident light that has passed through the first and second optical regions D1 and D2 is focused by the lens 304 and is incident on the array-shaped optical element 305. The array-shaped optical element 305 is, for example, a lenticular lens in which a plurality of cylindrical lenses extending in the x direction are arranged in the y direction. The array-shaped optical element 305 causes the light in the first wavelength band transmitted through the first bandpass filter 302 to enter the first incident region group 104, and emits the light in the second wavelength band transmitted through the second bandpass filter 303. , The second incident region group 105 is incident. A microlens array 308 may be provided on the surface of the interference element 106 in order to increase the incident efficiency to the first incident region group 104 and the second incident region group 105. As will be described later, the filter array 307 and the array-shaped optical element 305 may have the shapes shown in FIGS. 3E and 3F.

The transmission wavelength characteristics of the first and second bandpass filters 302 and 303 are the same as the transmission wavelength characteristics of the first and second bandpass filters 201 and 202 described in FIG. 2, respectively. The difference is that the size of the bandpass filter is large, and the large size has the advantage of facilitating production. Further, the measurable range can be changed by replacing only the bandpass filter with a filter having a different center wavelength.

In the examples shown in FIGS. 2 and 3A to 3F, even when the wavelength bandwidth of the incident light is relatively wide (for example, when a halogen lamp or a white LED light source is used), the bandpass filter is suitable for light in two wavelength bands. Can be taken out (see FIG. 26). When the two wavelength bands contained in the incident light originally have a bandwidth equal to or less than the transmission wavelength band of the bandpass filter (for example, two laser light sources), the transmission bandwidth of the bandpass filter is It doesn't have to be narrow. In such a case, the transmission bandwidth of the bandpass filter may be relatively wide as long as the light in the two wavelength bands can be separated from each other. Instead of the bandpass filter, a low-pass filter that transmits light in the first wavelength band and a high-pass filter that transmits light in the second wavelength band may be used (see FIG. 27). Optical filters with a wide transmission bandwidth can be easily manufactured.

(Example of arrangement of incident area group)
Although the interference element 106 is shown as a cross-sectional view in FIG. 1, an example of arranging the incident region group in the interference element when viewed from the front (that is, the light incident side) will be described with reference to FIG.

FIG. 4A is an example in which the first incident region group 104 and the second incident region group 105 are arranged side by side in a row. With such an arrangement, one-dimensional shape and distance information of the object to be measured can be measured by using a line-type image sensor.

FIG. 4B is an example in which the first incident region group 104 and the second incident region group 105 are arranged side by side in a row. If such an arrangement is used, there is an advantage that the interference element can be easily produced when the interference element is produced by using the grating (described later).

FIG. 4C is a two-dimensional extension of the arrangement of the incident region group shown in FIG. 4B. The two-dimensional shape and distance information of the object to be measured can be measured as an image.

FIG. 4D is another two-dimensional arrangement example of the incident region group. The first incident region group 104 and the second incident region group 105 are arranged every two rows. In this example, when a bandpass filter is provided close to each incident region group, the width of each bandpass filter can be widened (that is, the width can be set to the width of two rows of the incident region group), so that the bandpass filter can be easily manufactured. There is an advantage.

FIG. 4E is yet another two-dimensional arrangement example of the incident region group. The first incident region group 104 and the second incident region group 105 are arranged in 4 rows and 4 columns (8 regions in total), respectively. In this case as well, since the width of each bandpass filter can be widened (that is, the width can be set to the width of four columns), there is an advantage that the bandpass filter can be easily manufactured.

The shape of the incident region when viewed from the front does not necessarily have to be square, and may be circular, rectangular, or the like.

When a filter array arranged close to the light incident side of the interfering element 106 is used as the optical system 101 as shown in FIG. 2, the first incident region group 104 and the second incident region group 104 and the second are shown in FIGS. 4A to 4E. A filter array in which a plurality of first bandpass filters 201 and a plurality of second bandpass filters 202 are arranged may be used corresponding to the arrangement of the incident region group 105.

As described with reference to FIGS. 3A to 3D, when the optical system 101 includes a bandpass filter and an array-shaped optical element provided in the vicinity of the pupil region, it is configured as described below.

First, as shown in FIG. 4A, when the first incident region group 104 and the second incident region group 105 are arranged one-dimensionally in the y direction in the interference element 106, as shown in FIG. 3A, the first incident region group 104 and the second incident region group 105 are arranged one-dimensionally. A filter array 307 in which a two-bandpass filter 303 and a first bandpass filter 302 are arranged in the y direction, and an array-shaped optical element (wrenchular) in which cylindrical lenses extending in the x direction are arranged in the y direction as shown in FIG. 3C. Lens) 305 is used. In this case, since the first incident region group 104 and the second incident region group 105 of the interference element 106 are arranged one-dimensionally, the length of the array-shaped optical element 305 in the x direction may be one pixel.

When the interference elements 106 in which the first incident region group 104 and the second incident region group 105 are arranged in different rows are used as shown in FIGS. 4B to 4D, they are shown in the filter arrays 307 and 3C shown in FIG. 3A. The arrangement of the array-shaped optical elements 305 in the x-direction and the y-direction is exchanged, that is, a filter array in which the second bandpass filter 303 and the first bandpass filter 302 are arranged in the x-direction, and a cylindrical extending in the y-direction. Use a lenticular lens in which the lenses are arranged in the x direction. As shown in FIGS. 4B and 4C, when the interference element 106 in which the pair of the first incident region group 104 in one row and the second incident region group 105 in one row is arranged as one unit is used, each of the lenticular lenses is used. The width of the cylindrical lens has a width corresponding to two pixels. Further, as shown in FIG. 4D, when the interference element 106 in which the pair of the first incident region group 104 in the two rows and the second incident region group 105 in the second row are arranged as one unit is used, each of the lenticular lenses is used. The width of the cylindrical lens has a width corresponding to four pixels.

When the interference element 106 in which the first incident region group 104 and the second incident region group 105 are arranged in a check pattern as shown in FIG. 4E is used, the filter array 307 shown in FIG. 3E is used. The pupil region of the diaphragm 306 is divided into regions D1 to D4 by two planes orthogonal to each other including the optical axis V of the optical system 101. The filter array 307 includes a second bandpass filter 303 arranged in the regions D2 and D4, and a first bandpass filter 302 arranged in the regions D1 and D3. As the array-shaped optical element 305, as shown in FIG. 3F, a microlens array arranged in the x-direction and the y-direction is used. Each microlens M corresponds to the size of 16 pixels arranged four each in the x direction and the y direction.

(Specific configuration example of the interference element)
Next, a specific configuration example of the interference element 106 and the arrangement relationship with the pixel group will be described with reference to FIGS. 5 and 6.

5A to 5D show a cross-sectional view of an example in which a plurality of optical coupling layers are used for the interference element 106.

Each of the plurality of optical coupling layers 502 includes a waveguide layer 504 on which the grating 503 is formed. The waveguide layer 504 is located corresponding to two incident regions adjacent to each other in the first incident region group 104 or two incident regions adjacent to each other in the second incident region group 105. The base material of the interference element 106 is, for example, SiO ₂ . The waveguide layer 504 is a layer having a higher refractive index than the base material, and is made of, for example, Ta ₂ O ₅ . The waveguide layer 504 is not limited to one layer, and may be composed of a plurality of layers with a layer having a low refractive index interposed therebetween.

A grating 503 having a predetermined pitch is located at least at the interface on the incident side of the waveguide layer 504. The grating 503 is a linear grating, and the direction of its grating vector is parallel to the plane of the optical coupling layer 502 in the vertical direction of the paper surface of FIGS. 5A to 5D.

On the light incident side of the interference element 106, a light shielding region 501 is provided in a region other than the first and second incident region groups 104 and 105. That is, a light-shielding region is located between the two incident regions adjacent to each other in the first incident region group 104 and the two incident regions adjacent to each other in the second incident region group 105. The light-shielding region 501 is made of a reflective metal material such as Al, Ag, or Au, and has a thickness sufficient to sufficiently block light in the first and second wavelength bands.

Hereinafter, the optical path of the light incident on the first incident region group 104 will be described with reference to FIG. 5A. If the pitch of the grating 503 is set so that the light in the first wavelength band is combined, a part of the light incident on the two incident regions 104a and 104b adjacent to each other in the first incident region group will be the waveguide light 506a and a part, respectively. As 506b, it is incident on the waveguide layer 504 and propagates. The waveguide light 506a and 506b interfere with each other in the waveguide layer 504, are radiated from the waveguide layer 504 to the image sensor 109 side as interference light 107a, and are incident on one pixel 110a of the first pixel group 110. Here, the waveguide light 506a and 506b are light propagating from a pair of adjacent incident regions 104a and 104b, respectively. The intensity of the interference light 107 depends on the phase difference of the light incident on the first incident region group 104. Another part of the light incident on the incident regions 104a and 104b is radiated to the image sensor 109 side as transmitted light 108a and 108b instead of being waveguide light, and pixels 111a and 111b of the second pixel group 111. Incident in. Therefore, by detecting the intensity of the light incident on the pixels 110a, 111a and 111b, the phase difference of the light in the first wavelength band incident on the incident regions 104a and 104b can be obtained.

As shown in FIG. 5A, the optical path of the light incident on the second incident region group 105 can be described in the same manner as described above. The reason why the phase difference of the light incident on the pair of adjacent incident regions in the second incident region group 105 can be obtained from the intensity of the light incident on the third pixel group 112 and the fourth pixel group 113 is also the first reason. This is the same as in the case of the incident region group.

FIG. 5A shows the cross-sectional configuration of the plurality of optical coupling layers 502 in the interference element 106 in which the first and second incident region groups 104 and 105 are arranged one-dimensionally as shown in FIG. 4A. In this configuration, since both the first incident region group 104 and the second incident region group 105 exist in the direction of the grating lattice vector, the waveguide layer 504 at the boundary between the first and second incident region groups 104 and 105 The plurality of optical coupling layers 502 may be separated via a medium having a low refractive index. In this way, the light in the first and second wavelength bands separated by the bandpass filter does not interfere with each other, so that the phase difference of the light in the first wavelength band and the phase difference of the light in the second wavelength band are independent of each other. Can be detected.

5B and 5C show the cross-sectional configuration of the optical coupling layer 502 when the first and second incident region groups 104, 105 are arranged in different rows as shown in FIGS. 4B, 4C and 4D. There is. FIG. 5B is a cross-sectional view when cut in the row of the first incident region group 104, and FIG. 5C is a cross-sectional view when cut in the row of the second incident region group 105. In this configuration, since either the first incident region group 104 or the second incident region group 105 exists in the direction of the grating lattice vector, the position of the light in the first wavelength band does not need to be separated from the optical coupling layer. The phase difference and the phase difference of the light in the second wavelength band can be detected independently. The structure in which the photobonding layer 502 is not separated makes it easier to fabricate the photobonding layer 502.

FIG. 5D shows the cross-sectional configuration of the plurality of optical coupling layers 502 when the first and second incident region groups 104 and 105 are arranged in a check pattern as shown in FIG. 4E. In this configuration, as in FIG. 5A, since both the first incident region group 104 and the second incident region group 105 exist in the direction of the grating lattice vector, at the boundary between the first and second incident region groups 104 and 105. A plurality of optical coupling layers may be separated, and the pixels immediately below the portion where the optical coupling layers are separated may be regarded as unused pixels 505 and may not be used for calculating the phase difference information.

(Another example of the specific configuration of the interfering element)
6A to 6D show a cross-sectional view of an example in which a photonic crystal is used for the interference element 106.

The photonic crystal 601 is used to form a light propagation path. The light propagation path includes at least the first and second light propagation paths 602 and 603, and the third light propagation path 604 connecting the first light propagation path 602 and the second light propagation path 603. The incident portion of the first light propagation path 602 is arranged at a position different from the incident portion of the second light propagation path 603, and the exit portion of the first light propagation path 602 is different from the emission portion of the second light propagation path 603. Placed in different positions. The light propagation path shown in FIG. 6 further includes a fourth light propagation path 605. The fourth light propagation path 605 is connected to the third light propagation path 604, and the light incident from the third light propagation path 604 propagates. When the interference light and the transmitted light are separately detected as in the case where the interference element is composed of the plurality of optical coupling layers 502, the light propagation path preferably includes the fourth light propagation path 605. However, since the intensity of the emitted light of the first and second light propagation paths 602 and 603 changes depending on the phase difference of the light incident on the first and second light propagation paths 602 and 603, the fourth light propagation It is possible to obtain the phase difference information even in a configuration in which the path 605 does not exist.

The photonic crystal 601 is composed of, for example, a periodic arrangement of cavities, regions having different refractive indexes, dielectric posts, and the like, and a light propagation path is formed by removing a part of the periodic arrangement. The positions of the incident portions of the first and second light propagation paths 602 and 603 coincide with the two incident regions adjacent to each other in the first incident region group 104, respectively. That is, the first and second light propagation paths 602 and 603 are connected to two incident regions adjacent to each other in the first incident region group 104, respectively. The first incident region group 104 includes a plurality of pairs of two incident regions adjacent to each other as described above. The second incident region group 105 also includes a plurality of pairs of two incident regions adjacent to each other. A plurality of sets of first and second light propagation paths are arranged in the same manner as described above corresponding to the set of these plurality of incident regions. Further, corresponding to each set of the first and second light propagation paths, they were connected to the third light propagation path and the third light propagation path connecting the first light propagation path and the second light propagation path. A fourth light propagation path is provided.

Further, one of the pixels of the second pixel group 111 is arranged adjacent to the respective emission portions of the first and second light propagation paths 602 and 603, and the second pixel is adjacent to the emission portion of the fourth light propagation path 605. Any pixel of one pixel group 110 is arranged. Similarly, for the emission portions of the first and second light propagation paths corresponding to each set of the other incident regions of the first incident region group 104, any one of the second pixel groups 111 is adjacent to each of these emission portions. Pixels are arranged. Further, any one of the first pixel group 110 is adjacent to the exit portion of the fourth light propagation path connected to the third light propagation path connecting the first light propagation path and the second light propagation path. Pixels are arranged. Similarly, the emission portions of the first and second light propagation paths corresponding to each set of the incident regions of the second incident region group 105 are also adjacent to each of these emission portions and are any of the fourth pixel group 113. Pixels are arranged. Further, any one of the third pixel group 112 is adjacent to the exit portion of the fourth light propagation path connected to the third light propagation path connecting the first light propagation path and the second light propagation path. Pixels are arranged.
In this configuration, since both the first incident region group 104 and the second incident region group 105 exist in the direction in which the third light propagation path 604 extends, the dielectric material is present at the boundary between the first and second incident region groups 104 and 105. The third light propagation path 604 may be separated by leaving a post. In this way, the light in the first and second wavelength bands separated by the bandpass filter does not interfere with each other, so that the phase difference of the light in the first wavelength band and the phase difference of the light in the second wavelength band are independent of each other. Can be detected.

With such a configuration, a part of the light incident from the pair of adjacent incident regions in the first and second incident region groups 104 and 105 interferes in the third light propagation path, and becomes the interference light 107. Emit from the interference element 106. The state of light interference in the third light propagation path changes depending on the phase difference of light incident from a pair of adjacent incident regions. Further, another part of the light incident from the incident region is emitted from the interference element 106 as transmitted light 108. By detecting the intensities of the interference light 107 and the transmitted light 108 with the pixels of the image pickup element 109, it is possible to obtain the phase difference information of the light as in the case where the interference element is composed of the plurality of optical coupling layers 502. ..

FIG. 6A shows the cross-sectional configuration of the interference element 106 in which the first and second incident region groups 104 and 105 are arranged one-dimensionally as shown in FIG. 4A.

6B and 6C show the cross-sectional configuration of the interfering elements 106 when the first and second incident region groups 104 and 105 are arranged in different rows as shown in FIGS. 4B, 4C and 4D. .. In this configuration, since either the first incident region group 104 or the second incident region group 105 exists in the direction in which the third light propagation path 604 extends, the first light propagation path 604 does not need to be separated. The phase difference of light in the wavelength band and the phase difference of light in the second wavelength band can be detected independently.

FIG. 6D shows the cross-sectional configuration of the interference element 106 when the first and second incident region groups 104 and 105 are arranged in a check pattern as shown in FIG. 4E. In FIGS. 6A and 6D, the first and second incident region groups 104 and 105 are arranged in the same row. In such a configuration, as shown in FIGS. 6A and 6D, if the light propagation path is separated for each incident wavelength band from the incident region, the phase difference of the light in the first wavelength band and the second wavelength band can be obtained. The phase difference of light can be detected independently.

(Pixel arrangement of image sensor)
Although the image pickup device 109 is shown as a cross-sectional view in FIGS. 1, 5 and 6, FIGS. 7A to 7E show examples of arrangement of pixel groups in the image pickup device 109 when viewed from the front (that is, the light incident side). It will be described using.
7A to 7E show an example of arranging the pixel groups when the first and second incident region groups 104 and 105 are arranged as shown in FIGS. 4A to 4E, respectively. The interference light 107 of the light incident on the first incident region group 104 is on any pixel of the first pixel group 110, and the transmitted light 108 of the light incident on the first incident region group 104 is on the second pixel group 111. Interference light 107 of light incident on the second incident region group 105 on any of the pixels is transmitted light of light incident on any pixel of the third pixel group 112. The pixel group arrangement is such that 108 is incident on any pixel of the fourth pixel group 113. It is more preferable that the position of each incident region and the position of each pixel are substantially the same, that is, there is almost no deviation, because unnecessary crosstalk components to each pixel can be reduced.

(Configuration example of calculation unit)
An example of the signal flow from the image pickup device 109 and the configuration of the calculation unit in the photodetector shown in FIG. 1 will be described with reference to FIGS. 8 and 9.

As shown in FIG. 8, the incident region, the light-shielding region, and the signals output from each pixel of the image sensor are defined. Each signal is output according to the intensity of light incident on each corresponding pixel.

The incident area and the light-shielded area are called as follows. The nth incident region belonging to the mth incident region group is represented by _Amn . The pair of A _m1 and A _{m2 and} the pair of A _m3 and A _m4 are a pair of adjacent incident regions of the mth incident region group, respectively. The nth light-shielding region (or non-incident region) between the incident regions is represented by S _0n .

The signal is called as follows. From the pixel immediately below the entrance region A _mn or shading region S _mn, a signal of the transmitted light expressed by t _mn. The signal of the interference light from the pixel directly under the incident region A _mn or the light-shielding region S _mn is represented by i _mn .

As shown in FIG. 9, the first calculation unit 114 inputs signals t ₁₁ , i ₀₁ , t ₁₂ , t ₁₃ , i ₀₃ , and t _14, and first phase difference information p ₁₁ , p ₀₁ , p ₁₂ , P ₁₃ , p ₀₃ , p ₁₄ are output. Further, the second calculation unit 115 inputs signals t ₂₁ , i ₀₂ , t ₁₂ , t ₂₃ , i ₀₄ , and t ₂₄ , and the second phase difference information p ₂₁ , p ₀₂ , p ₂₂ , p ₂₃ , p. ₀₄ , p ₂₄ is output. In addition, the third calculation unit 118 uses the first phase difference information p ₁₁ , p ₀₁ , p ₁₂ , p ₁₃ , p ₀₃ , p ₁₄ and the second phase difference information p ₂₁ , p ₀₂ , p ₂₂ , p _23. , P ₀₄ , p ₂₄ are input, and the equivalent phase difference information E ₁₁ , E ₀₁ , E ₁₂ , E ₁₃ , E ₀₂ , E ₂₂ , E ₁₃ , E ₀₃ , E ₁₄ , E ₂₃ , E ₀₄ , E ₂₄ are input. Output. These pieces of information may be represented by electrical signals, or may be information held in a memory of a computer or the like. Further, the first, second and third arithmetic units 114, 115, 118 may be composed of one or a plurality of electronic circuits, and may be used as a program operating in a computer, a server, a portable electronic device, or the like. It may be included.

The first phase difference information 116 is the phase difference information with respect to the central wavelength of the first wavelength band (that is, λ _{1 of the} conventional example), and the second phase difference information 117 is the central wavelength of the second wavelength band (that is, λ _{2 of the} conventional example). ) Phase difference information. The phase difference information between light separated by the adjacent distance d _adj (i.e., the distance between adjacent pairs of the incident region) from the position of the incident region A _mn or shading region S _mn represented by p _mn.

The equivalent phase difference information 119 is the phase difference information with respect to the equivalent wavelength (that is, λ _{eff of the} conventional example). Represented by incident region A _mn or shielding region S adjacent the position of _mn distance d _adj (i.e., the distance between adjacent pairs of the incident region) only the equivalent phase difference information between light away E _mn.

The first calculation unit 114 calculates each incident from the signals (t ₁₁ , i ₀₁ , t ₁₂ , t ₁₃ , i ₀₃ , t ₁₄ ) output by interfering or transmitting light in the first wavelength band. Obtain the phase difference information (p ₁₁ , p ₀₁ , p ₁₂ , p ₁₃ , p ₀₃ , p ₁₄ ) in the region or the light-shielding region. In this method, the relationship between the light intensity of the interference light 107 or the transmitted light 108 and the phase difference in the incident region or the light-shielding region directly above is obtained by an experiment in advance, and the table or calculation is held in the memory as a table or calculation formula. It can be calculated using an equation. For example, light of two first wavelengths having a known phase difference is incident on two adjacent incident regions of the first incident region group, and the intensity of interference light or transmitted light is measured. The relationship between the phase difference and the light intensity can be experimentally obtained by making the phase differences of the two first wavelength lights different and repeating the measurement of the intensity of the interference light or the transmitted light. The distance corresponding to the phase difference can be calculated from the wavelength of the light used.

Similar to the first calculation unit 114, the second calculation unit 115 interferes with or transmits light in the second wavelength region and outputs signals (t ₂₁ , i ₀₂ , t ₁₂ , t ₂₃ , i ₀₄ , t _24). ) from the calculation, determining the phase difference information in each incidence area or the light-shielding region _{(p 21, p 02, p} 22, p 23, p 04, p 24).

Third arithmetic unit 118, a first phase difference information relating to the light in the first wavelength band _{(p 11, p 01, p} 12, p 13, p 03, p 14), associated with the light in the second wavelength band Equivalent phase difference information (E ₁₁ , E ₀₁ , E ₁₂ , E ₁₃ , E ₀₂ , using the second phase difference information (p ₂₁ , p ₀₂ , p ₂₂ , p ₂₃ , p ₀₄ , p ₂₄ ) E ₂₂ , E ₁₃ , E ₀₃ , E ₁₄ , E ₂₃ , E ₀₄ , E ₂₄ ). Equivalent phase difference information can be obtained by using a known method described in Patent Document 1 and Non-Patent Document 1.

Here, the phase difference information does not necessarily have to be obtained in association with all incident regions or light-shielding regions (that is, pixels of the image sensor). The average phase difference information of a region extending over a plurality of incident regions or light-shielding regions (for example, A ₁₁ , S _01, and A ₁₂ regions in FIG. 8) may be obtained. Further, the actual phase difference value itself does not have to be obtained as the phase difference information, and it may be a value related to the phase difference of the light incident between the specific regions of the interfering element. Based on this phase difference information, the shape of the object to be measured is obtained.

(Effect of the first embodiment)
According to this embodiment, since the interference light is generated inside the interference element 106 close to the image sensor 109, large optical components such as a half mirror and a reference mirror are not required, and light detection smaller than the conventional one is required. The device can be realized. In addition, since the two wavelength bands are separated by a bandpass filter provided directly above the interference element or near the pupil region, it is not necessary to use a plurality of image pickup tubes or image pickup elements, and the optical portion of the photodetector is made smaller than before. it can. Further, since light in a plurality of wavelength bands is used for measurement, the shape of an object having a step exceeding the wavelength of light can be measured without error. Further, since it is not necessary to route the optical path in the air due to the occurrence of the interference phenomenon, it is possible to obtain a precise measurement result that is not easily affected by the surrounding environment (for example, air convection or vibration).

(Second Embodiment)
In the first embodiment, the incident light is transmitted through a bandpass filter to obtain light in two wavelength bands having different center wavelengths. According to the first embodiment, even when the incident light has a wide wavelength band to some extent (for example, a halogen lamp or a white LED light source), the band pass filter having a pass band narrower than the wavelength band of the incident light can be used appropriately. Light in two wavelength bands can be obtained.

On the other hand, if each of the two wavelength bands of incident light originally has a wavelength spectrum having a width similar to that of the transmission wavelength band of the bandpass filter, the embodiment of the configuration without the bandpass filter Is also possible. Hereinafter, the embodiment will be described. Examples of such a light source include a laser light source.

FIG. 10 is a diagram illustrating the configuration of the second embodiment of the present disclosure.

The illumination 1001 irradiates the object to be measured with light in the first or second wavelength band. The wavelength band switch 1002 controls the illumination 1001 so that the illumination 1001 switches and emits light in two wavelength bands having different center wavelengths in a time-divided manner.

For example, the illumination 1001 may include a wavelength tunable laser light source, and the wavelength band switch 1002 may include a circuit for switching the wavelength of the wavelength tunable laser light source. Further, the illumination 1001 may include two laser light sources having different radiation wavelength bands, and the wavelength band switch 1002 may include a circuit for alternately switching between radiation and non-radiation of the two laser light sources. Further, even if the illumination 1001 includes a light source having a relatively wide wavelength band and a plurality of bandpass filters, and the wavelength band switch 1002 includes a mechanism for alternately switching the bandpass filters arranged on the optical path from the light source. Good.

The light transmitted or reflected from the object to be measured is incident on the optical system 1003 as incident light. The optical system 1003 causes the light 1004 in the first or second wavelength band to be incident on the fifth incident region group 1005 without spatially dividing the wavelength band of the incident light. The process of generating the interference light 107 and the transmitted light 108 in the interference element 106 is the same as that of the first embodiment. Further, the process of generating the interference light 107 and the transmitted light 108 in the fifth pixel group 1006 and the sixth pixel group 1007 of the image pickup device 109 is also the same as in the first embodiment. The difference from the first embodiment is that light 1004 in the first and second wavelength bands can be incident on any incident region and any pixel.

The light intensity signals output from the fifth pixel group 1006 and the sixth pixel group 1007 are input to the fourth calculation unit 1009. The fourth calculation unit 1009 calculates and outputs the first phase difference information 116 and the second phase difference information 117 based on the input signal. The process of obtaining the phase difference information from the light intensity signal is the same as that of the first embodiment. The difference is that the first phase difference information 116 is obtained by using the light intensity signal at the timing when the light in the first wavelength band is irradiated based on the synchronization signal 1008 from the wavelength band switch 1002, and the second The second phase difference information 117 is obtained by using the light intensity signal at the timing when the light in the wavelength band is irradiated.

Similar to the first embodiment, the third calculation unit 118 calculates and outputs the equivalent phase difference information 119 based on the first phase difference information 116 and the second phase difference information 117.

In such a configuration, it is not necessary to use a bandpass filter in the optical system, so that a photodetector having a simpler configuration can be realized.

(Third Embodiment)
In the second embodiment, a configuration has been described in which illumination in two wavelength bands having different center wavelengths is switched and emitted in a time-division manner. In the third embodiment, a configuration in which illuminations in these two wavelength bands are simultaneously irradiated will be described.

FIG. 11 is a diagram illustrating the configuration of the third embodiment of the present disclosure.

The illumination 1101 in the first wavelength band and the illumination 1102 in the second wavelength band simultaneously irradiate the object to be measured. These two lights have emission wavelength bands with different center wavelengths. Further, it is more preferable that these two lights are radiated with the same optical axis and radiation direction by using, for example, a beam splitter.

The light transmitted or reflected from the object to be measured is incident on the optical system 1003 as incident light. The optical system 1003 causes the light 1103 in the first and second wavelength bands to be incident on the fifth incident region group 1005 without spatially dividing the wavelength band of the incident light. Similar to the second embodiment, light in the first and second wavelength bands can be incident on any incident region and any pixel of the fifth incident region group.

Interference light 107 is incident on the fifth pixel group 1006, and transmitted light 108 is incident on the sixth pixel group 1007. Here, since the interference light 107 and the transmitted light 108 are generated from the light in both the first and second wavelength bands, the light in the two wavelength bands is superposed.

In this state, the light intensity signal based on the phase difference between the first and second wavelength bands cannot be acquired independently, but instead, the signal from the pixel group includes light incident on a pair of adjacent incident regions. The component corresponding to the case where the phase difference of is observed at the equivalent wavelength is included. The fifth calculation unit 1104 extracts the components corresponding to the observation at the equivalent wavelength and calculates the equivalent phase difference information 119.

In such a configuration, it is not necessary to switch the illumination by time division, so that a photodetector having a simpler configuration can be realized.

(First Example)
The first embodiment of the present disclosure will be described below.

In this embodiment, the arrangement of the first incident region group 104 and the second incident region group 105 is as shown in FIG. 4C. That is, in the interference element 106, the first incident region group and the second incident region group are alternately arranged in each row. In other words, the light in the first wavelength band (the central wavelength of this light is λ ₁ ) and the light in the second wavelength band (this light is λ ₂ ) alternate in a row on the interfering element 106. Incident in. In each row, incident areas and light-shielded areas are arranged alternately.

The first to fourth pixel groups 110 to 113 have the form shown in FIG. 7C. As described above, the first and second pixel groups and the first incident region group, and the third and fourth pixel groups and the second incident region group are in a corresponding relationship, respectively. The number of pixels was 100 pixels × 100 pixels.

FIG. 12 shows a specific cross-sectional structure of the interference element used in this embodiment. The interfering element 106 has an optical coupling layer. The incident light is emitted toward the incident region 1201 and the light-shielding region 501. The light-shielding layer 1202 is provided to distinguish between the incident area and the light-shielding area. The material of the light-shielding layer was Al and the thickness was 100 nm. The widths of the incident region and the light-shielded region are both 5.6 μm.

The optical coupling layer 502 is composed of six waveguide layers, and gratings are formed at the upper and lower interfaces of the waveguide layer. The waveguide layer is a transparent layer having a relatively high refractive index, and was constructed using Ta ₂ O ₅ in this example. The material sandwiching the waveguide layer is a transparent layer having a relatively low refractive index, and in this embodiment, SiO ₂ is used. The grating depth is 0.2 μm, and the pitch (Λ in FIG. 12) is 0.45 μm. The thickness of the Ta ₂ O ₅ layer (t _{1 in} FIG. 12) was 0.34 μm, and the thickness of the SiO ₂ layer between the waveguide layers (t _{2 in} FIG. 12) was 0.22 μm.

When light having a wavelength of 850 nm is incident on the interference element 106 having such a structure perpendicularly to the incident surface, the intensity of the interference light 107 emitted from the interference light region 1203 and the transmission emitted from the transmitted light region 1204. The intensity of the light 108 was calculated by the FDTD (Finite-difference time-domine method) method. As a parameter of the incident light, the intensity of the light incident on the adjacent incident region 1201 was made equal, and the phase difference was changed from −180 degrees to 180 degrees.

FIG. 13 shows the calculation results of the intensities of the interference light 107 and the transmitted light 108 with respect to the phase difference of the incident light (in the figure, the unit “degree” of the phase difference is expressed as [deg.]). The intensity ratio indicates the ratio of the incident light to the intensity.

When the phase difference is approximately 0 degrees (that is, in-phase), the intensity of the interference light is maximized and the intensity of transmitted light is minimized. When the phase difference is approximately ± 180 degrees, the intensity of the interference light is the minimum and the intensity of the transmitted light is the maximum. From these results, it can be seen that the intensities of the interference light and the transmitted light change according to the phase difference. This indicates that the interference light and the transmitted light are emitted as a result of the light incident from the adjacent incident regions interfering with each other in the interference element.

Next, using this result, the process of estimating the shape of the object from the light transmitted through the object to be measured will be described by calculation.

A sample having the shape shown in FIG. 14A is set as the object to be measured. The sample consists of a narrow wedge-shaped bottom and a central protrusion. FIG. 14B shows an outline of the shape when the sample is viewed from the x direction. The thickness of the wedge is 600 nm, and the height of the convex portion is 50 μm. The refractive index of the sample was 1.45.

It is assumed that the light incident from the bottom surface side of this sample passes through the sample and enters the optical system as incident light in a state where a difference in optical path length is generated. Further, it is assumed that the light passing through the region corresponding to the plane in the range of x = 1 to 100 and y = 1 to 100 of the sample is incident on the pixels in the range of 100 × 100 pixels of the image sensor.

The central wavelengths of the light incident on the sample were λ ₁ = 845 nm and λ ₂ = 855 nm. The bandwidth of each light is 5 nm in full width at half maximum.

FIG. 15 shows the intensity of light incident on each pixel of the image sensor. FIG. 15A is interference light having a center wavelength λ ₁ (that is, light incident on the first pixel group), FIG. 15B is interference light having a center wavelength λ ₂ (that is, light incident on the second pixel group), and FIG. 15C is a center wavelength λ. ₁ transmitted light (that is, light incident on the second pixel group), FIG. 15D is transmitted light having a center wavelength λ ₂ (that is, light incident on the fourth pixel group). In each of the figures of FIG. 15, the pixels that do not correspond to the pixel group shown (for example, the pixels that correspond to the second, third, and fourth pixel groups of FIG. 15A) are shown with the intensity set to zero. From each figure of FIG. 15, it can be seen that when viewed in the column direction (that is, in the y direction of the figure), a large intensity change occurs at a portion where the optical path length difference greatly changes in the adjacent incident region.

In the actual measurement, if the relationship shown in FIG. 13 is used, the absolute value of the phase difference in each pixel of the image sensor can be obtained from the intensity of the light incident on each pixel. This is a calculation performed by the first calculation unit 114 and the second calculation unit 115, and corresponds to a step of obtaining phase difference information. However, since the phase difference value of the center wavelength λ _{1 and} the phase difference value of the center wavelength λ ₂ are acquired alternately for each column, the columns for which the absolute value of the phase difference cannot be acquired at each center wavelength are, for example, on both sides. The absolute value of the phase difference is obtained by interpolating from the absolute value of the phase difference of the column. The absolute values of the phase differences at the center wavelengths λ ₁ and λ ₂ calculated in this way are shown in FIGS. 16A and 16B, respectively.

To determine the polarity of the phase difference, for example, the change in the absolute value of the phase difference when the sample is slightly tilted about the x direction may be observed. This is because the direction of increase / decrease in the absolute value of the phase difference changes depending on the polarity of the phase difference. In this way, the values of the phase difference at the center wavelengths λ ₁ and λ ₂ obtained with polarity are shown in FIGS. 17A and 17B, respectively.

It is described in Patent Document 1 and Non-Patent Document 1 that the value of the phase difference of adjacent incident regions at the equivalent wavelength λ _eff is calculated from the value of the phase difference of adjacent incident regions at the center wavelengths λ ₁ and λ ₂ . It is possible by using the method described. This is a calculation performed by the third calculation unit 118, and corresponds to a step of obtaining phase difference information. The phase difference value at the equivalent wavelength λ _eff obtained in this way is shown in FIG.

The phase value at λ _eff can be calculated by integrating the phase difference value at λ _eff in the column direction. FIG. 19 shows the calculation result of the phase value at λ _eff .

The phase difference values at λ ₁ and λ ₂ may be integrated in the column direction to calculate the phase values at λ ₁ and λ _{2, and} the phase value at λ _eff may be obtained from the calculation results. The phase values at λ ₁ and λ ₂ are shown in FIGS. 20A and 20B, respectively.

Since the distribution of the optical path length difference can be obtained from the phase value at λ _eff , the shape of the sample can be restored and estimated by using the value of the refractive index of the sample. The estimated shape is shown in FIG. It can be seen that the shape of the original sample shown in FIG. 14A can be almost restored.

The reason why the shape with a step of about 50 μm in height like this sample could be restored without error is because light of two wavelengths λ ₁ and λ ₂ was used. Since the equivalent wavelength λ _eff of this embodiment is (855 × 845) / (855-845) = 72.2 μm, any step corresponding to the optical path length difference not exceeding this equivalent wavelength can be restored without error. become. For comparison, the results of restoring the shape from only the light of either λ ₁ or λ ₂ are shown in FIGS. 22A and 22B. Since the step of the convex part of the sample exceeds the wavelength, it can be seen that the shape cannot be accurately restored.

As described above, the present disclosure provides a photodetector having a smaller optical portion, less susceptible to the influence of the surrounding environment, and capable of measuring the shape of an object having a step exceeding the wavelength of light without error.

(Second Example)
The second embodiment of the present disclosure will be described below.

This embodiment describes a method of measuring a step of an object to be measured by the photodetector described in the third embodiment of the present disclosure.

The photodetector uses the configuration shown in FIG. That is, the light in the first and second wavelength bands is not spatially separated by the optical system. The structure of the interfering element is the same as that of the first embodiment. Further, as in the first embodiment, the central wavelengths of the light incident on the sample were λ ₁ = 845 nm and λ ₂ = 855 nm.

As the object to be measured, a sample having the shape shown in FIG. 23 was assumed. Two samples with different heights are placed in contact with each other, and the step between the samples is L. The refractive index of the sample was 1.45.

The light incident from the bottom surface side of this sample passes through the sample, and the light path length difference is caused by the step, and the light is incident on the optical system as incident light.

When the light incident on the pair of adjacent incident regions has this optical path length difference, the intensities of the interference light and the transmitted light obtained are shown in FIGS. 24A and 24B, respectively. The intensity ratio indicates the ratio of the intensity of the interference light or the transmitted light to the incident light. The intensity ratio was plotted separately for the center wavelengths λ ₁ and λ ₂ with the step L as a parameter. Since λ ₁ and λ ₂ have different wavelengths, the phase difference is shifted even at the same step L. As a result, it can be seen that the intensities of the interference light and the transmitted light also deviate between λ ₁ and λ _{2 due} to the step L.

In the configuration of the photodetector shown in FIG. 11, light having central wavelengths λ ₁ and λ ₂ is simultaneously incident on the pixels of the image sensor, so that the light intensity signal obtained from the image sensor superimposes the light of λ ₁ and λ _2. It will be a combination. The plots of the intensities of the superposed interference light and transmitted light and the relationship with the step L are shown in FIGS. 25A and 25B, respectively. As can be seen from the figure, it can be seen that the component of the envelope changes gently with respect to the step L in both the interference light and the transmitted light. This is the component corresponding to the case where the phase difference is observed at the equivalent wavelength λ _eff .

By using this phenomenon, for example, the sample can be thermally expanded and the change in the step L can be measured. That is, if the intensity of the interference light or the transmitted light is observed while changing the step L and the envelope component is extracted (this corresponds to the step of calculating by the fifth calculation unit), the wavelength of the incident light is exceeded. It is possible to measure the step without error.

In the photodetector of the above embodiment, the incident light is light in two bands having different center wavelengths, but it may be in three or more bands. Further, the wavelength value is not limited to the above, and an optimum value may be set according to the application.

Further, the configuration of the photodetector used in the above embodiments and examples is not limited to the above, and can be changed to an appropriate one within a range satisfying the configurations and effects of the above invention. ..

The photodetector of the present disclosure can be applied to measurement for industrial use, medical use, beauty use, security use, in-vehicle use, and the like. Further, a new imaging function such as a phase difference distribution or a phase distribution can be added to a digital still camera, a video camera, or the like.

101 Optical system 102 Light in the first wavelength band 103 Light in the second wavelength band 104 First incident region group 105 Second incident region group 106 Interfering element 107 Interfering light 109 Imaging element 110-113 First to fourth pixel groups 114 First 1 Calculation unit 115 Second calculation unit 116 First phase difference information 117 Second phase difference information 118 Third calculation unit 119 Equivalent phase difference information 201 First bandpass filter 202 Second bandpass filter 302 First bandpass filter 303 2 Bandpass Filter 304 Lens 305 Array Optical Element 306 Aperture 307 Filter Array 308 Microlens Array 501 Shading Region 502 Optical Coupling Layer 503 Glazing 504 Waveguide Layer 505 Unused Pixels 506a Waveguide Light 601 Photonic Crystal 602-605 1st 1st 4th light propagation path 1001 Illumination 1002 Wave band switch 1003 Optical system 1004, 1103 Light 1006 5th pixel group 1007 6th pixel group 1008 Synchronous signal 1009 4th arithmetic unit 1101, 1102 Illumination 1104 5th arithmetic unit 1201 Incident region 1202 Shading layer 1203 Interference light region 1204 Transmitted light region

Claims (15)

An image sensor including a plurality of first pixels, a plurality of second pixels, a plurality of third pixels, and a plurality of fourth pixels.
Interfering elements having a plurality of first incident regions and a plurality of second incident regions,
An optical system in which light in the first wavelength band is incident on the plurality of first incident regions and light in a second wavelength band different from the first wavelength band is incident on the plurality of second incident regions.
With
The interfering element is
A part of the light of the first wavelength band incident on the two adjacent first incident regions of the plurality of first incident regions is interfered with, and the interfered light is made to interfere with any one of the plurality of first pixels. To guide the other part of the light in the first wavelength band incident on the two first incident regions to any of the plurality of second pixels.
A part of the light of the second wavelength band incident on the two adjacent second incident regions of the plurality of second incident regions is made to interfere with each other, and the interfered light is caused by any of the plurality of third pixel groups. A photodetector that guides the other part of the light in the second wavelength band incident on the two second incident regions to any of the plurality of fourth pixels. The first phase difference information is obtained from the light intensity information detected by the plurality of first pixels and the light intensity information detected by the plurality of second pixels.
The photodetector according to claim 1, further comprising an arithmetic circuit for obtaining second phase difference information from the light intensity information detected by the plurality of third pixels and the light intensity information detected by the plurality of fourth pixels. .. From the first phase difference information and the second phase difference information, the arithmetic circuit obtains phase difference information at equivalent wavelengths of the first wavelength included in the first wavelength band and the second wavelength included in the second wavelength band. The optical detection device according to claim 2. The interfering element includes a plurality of optical coupling layers.
The photodetector according to claim 1, wherein each of the plurality of optical coupling layers includes a waveguide having a diffraction grating. The interference element has a first light-shielding region located between the two first incident regions and a second light-shielding region located between the two second incident regions.
The plurality of optical coupling layers include the two first incident regions and the first light-shielding region, or the photo-bonding layers located corresponding to the two second incident regions and the second light-shielding region.
The plurality of second pixels include two second pixels located corresponding to the two first incident regions.
The plurality of first pixels include a first pixel located corresponding to the first shading region.
The plurality of fourth pixels include two fourth pixels located corresponding to the two second incident regions.
The photodetector according to claim 4, wherein the plurality of third pixels include a third pixel located corresponding to the second light-shielding region. The interfering element is
The first light propagation path and
The second light propagation path and
The photodetector according to claim 1, further comprising a third light propagation path connecting the first light propagation path and the second light propagation path. The first light propagation path includes an incident portion in which light from one of the two first incident regions or one of the two second incident regions is incident, and a part of the incident light in the plurality of second incident regions. A light emitting unit that emits light to any one of the pixels or any of the plurality of fourth pixels is provided.
The second light propagation path includes an incident portion where light from the other of the two first incident regions or the other of the two second incident regions is incident, and a part of the incident light is the plurality of second incident regions. The light detection device according to claim 6, further comprising an exit unit that emits light to any one of the pixels or any of the plurality of fourth pixels. The interfering element further comprises a fourth light propagation path.
The fourth light propagation path has an incident portion connected to the third light propagation path and light incident from the incident portion to either one of the plurality of first pixels or the plurality of third pixels. The light detection device according to claim 7, further comprising an emitting unit for emitting light. The optical system is a filter array having a plurality of first bandpass filters that selectively transmit light in the first wavelength band and a plurality of second bandpass filters that selectively transmit light in the second wavelength band. The optical detection device according to claim 1. The optical system is
A first bandpass filter that selectively transmits light in the first wavelength band,
A second bandpass filter that selectively transmits light in the second wavelength band,
The light in the first wavelength band transmitted through the first bandpass filter is incident on the plurality of first incident regions, and the light in the second wavelength band transmitted through the second bandpass filter is incident on the plurality of first incident regions. An array of optical elements incident on the second incident region and
The photodetector according to claim 1. An image sensor containing a plurality of fifth pixels and a plurality of sixth pixels,
Interfering elements containing a plurality of fifth incident regions and
Lighting that emits light in the first wavelength band and light in a second wavelength band different from the first wavelength band, and
With
The interfering element is
A part of the light of the first wavelength band incident on the two adjacent fifth incident regions of the plurality of fifth incident regions is interfered with, and the interfered light is made to interfere with any one of the plurality of fifth pixels. To guide the other part of the light in the first wavelength band incident on the two fifth incident regions to any of the plurality of sixth pixels.
A part of the light in the second wavelength band incident on the two fifth incident regions is interfered with, and the interfered light is guided to one of the plurality of fifth pixels to the two fifth incident regions. A photodetector that guides another portion of incident light in the second wavelength band to any of the plurality of sixth pixels. The light detection device according to claim 11, wherein the illumination simultaneously emits light in the first wavelength band and light in the second wavelength band. The light detection device according to claim 11, wherein the illumination emits light in the first wavelength band and light in the second wavelength band in a time-divided manner. The photodetector according to claim 6, wherein the first, second, and third light propagation paths are composed of photonic crystals. The photodetector according to claim 8, wherein the first, second, third, and fourth light propagation paths are composed of photonic crystals.

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