Spectral confocal three-dimensional measurement system based on spatial modulation

Abstract

The utility model discloses a spectral confocal three-dimensional measurement system based on spatial modulation, comprising a light source used for generating a compound color light beam; the light space modulation element is used for adjusting the incident space position of the incident light of the light source in a time-sharing manner; the dispersion imaging optical assembly is used for dispersing the multi-color light beams adjusted by the light space modulation element and focusing the multi-color light beams to different depths in the first space direction; after the position of the incidence space is adjusted, light with different depths correspondingly enters different positions of the surface of a sample to be measured, is reflected by the sample to be measured and then is coupled into an imaging spectrometer. According to the system realized by the utility model, the measurement precision and the measurement speed can be effectively improved by virtue of the change of the light position in space by the light space modulation element and the combination of the corresponding dispersion imaging light path element.

Description

Technical Field

[0001] This utility model relates to the field of microstructure three-dimensional measurement technology, and in particular to a spectral confocal three-dimensional measurement system based on spatial modulation. Background Technology

[0002] 3D inspection technology based on spectral confocalization is a commonly used technique in the field of optical inspection of 3D microstructures such as wafers, LED panels, and PCBs. It has the advantages of high inspection accuracy and fast inspection speed.

[0003] A schematic diagram of a 3D microstructure detection system based on spectral confocalization is shown below. Figure 1 As shown, the basic principle of its detection is as follows. The polychromatic light beam emitted by the polychromatic light source will undergo dispersion along the z-axis after passing through lens group 01 and lens group 02. That is, beams of different wavelengths will be focused at different positions along the z-axis, as shown in the figure, the focal planes along the z-axis from top to bottom are λ1, λ2, and λ3. Assuming that the surface of a certain area of ​​the sample to be tested is located on the focal plane of the beam with wavelength λ2, the beam with wavelength λ2 will converge into a focal spot on the surface of that area of ​​the sample, while the beams with wavelengths λ1 and λ3 will be diffused in that area. Lens group 03 is the same as lens group 01, and the slit position is conjugate with the position of the polychromatic light source. Therefore, after the beam reflected back from the sample passes through lens group 02, the beam splitter, and lens group 03, the portion of the beam with wavelength λ2 will still converge into a focal spot on the slit plane, while the portions of the beam with wavelengths λ1 and λ3 will also form diffused spots on the slit plane. After spatial filtering by the slit, the imaging spectrometer will obtain the spectral line with wavelength λ2. When the stage moves to focus the light beam onto another region of the sample, if the surface height of that region changes, the spectrometer will acquire spectral lines of the corresponding wavelength. In this way, three-dimensional detection of the sample can be performed through scanning.

[0004] Existing point scanning and line scanning systems require mechanical scanning to achieve three-dimensional measurement of the entire DUT. Mechanical scanning inevitably introduces vibration, reducing measurement accuracy. Furthermore, mechanical scanning takes longer.

[0005] Therefore, those skilled in the art urgently need to develop and acquire a spatially modulated spectral confocal three-dimensional measurement system. Utility Model Content

[0006] In view of one or more of the above-mentioned defects or improvement needs of the prior art, and to overcome the problems caused by the existing point scanning system and line scanning system, this utility model proposes a spectral confocal three-dimensional measurement system based on spatial modulation. The implementation of the system according to this utility model effectively improves the measurement accuracy and measurement speed of the three-dimensional system.

[0007] The aforementioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0008] This utility model discloses a spatial modulation-based spectral confocal three-dimensional measurement system, which includes,

[0009] A light source used to produce polychromatic light beams;

[0010] An optical spatial modulation element is used to adjust the incident spatial position of the incident light from the light source in a time-division manner;

[0011] A dispersive imaging optical component is used to disperse the polychromatic beam after it has been modulated by the optical spatial modulation element and focus it to different depths in a first spatial direction.

[0012] After the light is spatially positioned by the optical spatial modulation element, it passes through the dispersive imaging optical component and is incident on different positions on the surface of the sample to be measured. After being reflected by the sample, it is coupled into the imaging spectrometer.

[0013] The first spatial direction is the optical axis direction of the dispersive imaging optical component or the direction of the dispersive imaging optical component parallel to the optical axis direction.

[0014] Furthermore, the optical spatial modulation element has multiple light flux units arranged at the incident space position, and the multiple light flux units are turned on or off, corresponding to the incident light being reflected or not reflected; the optical spatial modulation element is a digital micromirror array, and the light adjustment unit is a micromirror.

[0015] Furthermore, the optical spatial modulation element is located on the object plane of the system formed by the dispersive imaging optical components.

[0016] Furthermore, a micropore array for spatial filtering is provided in front of the imaging spectrometer, and the micropore array corresponds one-to-one with the light adjustment unit in the digital micromirror array.

[0017] Furthermore, the dispersive imaging optical component includes a telecentric dispersive objective lens, so that light from different positions on the surface of the sample to be measured is dispersed by the telecentric dispersive objective lens in a first spatial direction, generating dispersive light micromirrors digital micromirrors focused at different depths in the first spatial direction.

[0018] Furthermore, after the incident light is collimated, it is reflected by the first beam splitter and then incident on the optical spatial modulation element. The light, which is spatially modulated by the optical spatial modulation element, is transmitted through the first beam splitter and then enters the dispersive imaging optical component.

[0019] Furthermore, the dispersive imaging optical component further includes a first lens group and a second beam splitter. The light that enters the dispersive imaging optical component after being transmitted through the first beam splitter passes through the first lens group, the second beam splitter, and the telecentric dispersive objective in sequence before reaching the surface of the measurement sample. The light reflected from the surface of the measurement sample is reflected by the telecentric dispersive objective and the second beam splitter before entering the imaging spectrometer.

[0020] Furthermore, the imaging spectrometer also includes a second lens group for focusing the light reflected by the second beam splitter.

[0021] Furthermore, the optical spatial modulation element is a digital micromirror array, the polychromatic beam is a linear beam, the first region of the digital micromirror array is in a light-reflecting state, and the other regions are in a non-light-reflecting state, the linear beam is reflected from the first region, and the first region includes one or more rows of the digital micromirror array.

[0022] Furthermore, the optical spatial modulation element also includes a galvanometer, which is a second-level adjustable dispersion imaging optical component that adjusts the incident spatial position of the light passing through the optical adjustment unit.

[0023] In summary, the beneficial effects of the above-described technical solutions conceived by this utility model compared with the prior art include:

[0024] This invention proposes a spatial modulation-based spectral confocal three-dimensional measurement system. Compared with the mechanical scanning methods in existing point scanning and line scanning systems, this invention achieves scanning of the sample surface through optical spatial modulation element control. The optical spatial modulation element is set on the object plane of the dispersive imaging optical component. The incident light is controlled by the optical spatial modulation element so that different incident lights are incident on the sample surface to be measured. In this way, accurate and rapid scanning of the sample surface can be achieved.

[0025] This invention places a spatial modulation element on the incident light path, enabling spatial adjustment of the incident light. Furthermore, by adjusting the area of ​​the element, scanning of different positions on the surface of the sample to be measured can be achieved in spatial location.

[0026] This invention enables two-dimensional or three-dimensional measurement of samples, effectively improving measurement accuracy and speed. Furthermore, the spatial modulation method avoids frequent movement of the physical optical path during scanning, effectively enhancing measurement speed and stability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a spectral confocal three-dimensional detection system implemented according to existing technology.

[0028] Figure 2 It is a schematic diagram of the sample cross-section and the spectrum of the sample surface obtained by the system in the spectral confocal three-dimensional detection implemented in the existing technology.

[0029] Figure 3 This is a schematic diagram of the composition structure of a spatially modulated spectral confocal three-dimensional measurement system implemented according to this utility model. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the invention. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Existing spectral confocal detection systems can be divided into two types based on the light source: point light source and line light source.

[0033] In such Figure 1 In the point-scanning confocal spectral detection system shown, the polychromatic beam emitted by the point polychromatic light source converges into a single point on the corresponding focal plane, representing the height of the sample area illuminated by that point in a single exposure. Therefore, the stage needs to move and scan in both the x and y directions to perform three-dimensional measurements of the sample.

[0034] In such Figure 1 In the line-scanning confocal spectral detection system shown, the line polychromatic light source is placed along the x-axis. The polychromatic beams emitted from this source converge at their respective focal planes to form a line along the x-axis. Therefore, a single camera exposure can acquire all spectral information corresponding to different heights within the entire linear region of the sample illuminated by this line. Thus, three-dimensional measurement of the sample can be performed simply by moving the stage along the y-axis.

[0035] In an online scanning spectral confocal detection system, Figure 2 (a) is the cross-section of the sample. Figure 2 (b) is a spectral schematic image of the sample surface structure obtained by the system in a single exposure; calculation Figure 2 (b) The width Δp of the raised spectral line and its wavelength difference Δλ with the base spectral line can be obtained respectively. Figure 2(a) shows the width Δd and height Δh of the rectangular raised surface of the sample. Both the raised spectral lines and the substrate spectral lines have corresponding intensity distributions along the spectral wavelength. The algorithm first determines the wavelength λ2 corresponding to the peak intensity of the raised spectral line and the wavelength λ1 corresponding to the peak intensity of the substrate spectral line, and then subtracts them to obtain the wavelength difference Δλ, i.e., Δλ = λ2 - λ1.

[0036] This utility model discloses a spatially modulated spectral confocal three-dimensional measurement system, which includes a light source 01 for generating a polychromatic light beam;

[0037] The optical spatial modulation element is used to adjust the incident spatial position of the incident light from the light source 01. At this time, the optical spatial modulation element can adjust the incident spatial position of the incident light without any mechanical movement in space. The adjustment of the incident spatial position ultimately results in the adjustment and change of the incident position on the surface of the sample 06 to be measured during the propagation of the light source.

[0038] The optical spatial modulation element in this invention can adjust the incident position without moving in space. The optical spatial modulation element is set on the incident light path of the light source. The polychromatic light beam generated by the light source 01 forms uniform illumination on the optical spatial modulation element after optical path processing.

[0039] The optical spatial modulation element has an array-type optical adjustment unit, which can realize the reflection or non-reflection of light in the array area based on micro-switches. Thus, when the incident spatial position of the incident light is changed, the incident position falling on the surface of the sample 06 to be measured is also changed accordingly.

[0040] The specific implementation of the optical spatial modulation element is a digital micromirror array, with each micromirror acting as a light adjustment unit. Each micromirror can be moved to reflect or not reflect light, allowing each light adjustment unit to adjust the position of the polychromatic light within its array's spatial location. The final effect is that the position of the light projected onto the surface of the sample 06 to be measured varies.

[0041] A dispersive imaging optical component is used to disperse a polychromatic beam after it has been modulated by an optical spatial modulation element and focus it to different depths in a first spatial direction.

[0042] After the light is spatially adjusted by the optical spatial modulation element, it passes through the dispersive imaging optical component and is incident on different positions on the surface of the sample to be measured. After being reflected by the sample, it is coupled into the imaging spectrometer. The first spatial direction is the optical axis direction of the dispersive imaging optical component or a direction parallel to the optical axis direction. Different reflection positions correspond to different positions on the surface of the sample to be measured.

[0043] An optical spatial modulation element arranges multiple luminous flux units at an incident spatial position. The incident spatial position corresponds to multiple dimensions. The first dimension is the direction of light propagation, and the second dimension is the plane in which the optical spatial modulation element is arranged in its array. The multiple luminous flux units of the optical spatial modulation element are arranged at a height along a plane in the incident light direction.

[0044] Alternatively, multiple optical modulation elements can be arranged sequentially along the incident light direction, resulting in non-overlapping or overlapping projected areas on the surface of the sample to be measured. This projected area is the projected area of ​​the optical system. This means that the optical spatial modulation elements are arranged in an array with a height difference along the direction of light propagation in space, or that the array arrangement is not absolutely planar. Therefore, the spatial misalignment can be used to adjust the angle of the light incident position by amplification.

[0045] Multiple luminous flux units are turned on or off, corresponding to whether the incident light is reflected or not. In this way, the incident position of the light source is adjusted and changed. With the components in the overall optical path remaining unchanged, the position of the light source illuminating the surface of the sample to be measured changes after the incident position of the light source is changed.

[0046] Multiple optical flux units of an optical spatial modulation element are arranged at a plane height along the incident light direction. In one embodiment, the optical spatial modulation element is a digital micromirror array. In other embodiments, the multiple optical flux units are arranged at multiple plane heights staggered by a certain size along the incident light direction, so that the light incident from the light source, after propagation through the sequence of optical spatial modulation elements, forms spatially tunable resolution.

[0047] The spatial modulation-based spectral confocal three-dimensional measurement system implemented according to this utility model, in a specific optical path structure embodiment, is as follows: Figure 3 As shown, the dispersive imaging optical component includes a telecentric dispersive objective lens 07, so that light from different positions on the surface of the sample 06 to be measured is dispersed by the telecentric dispersive objective lens 07 in the first spatial direction, generating dispersive light focused at different depths in the first spatial direction.

[0048] After collimation, the incident light is reflected by the first beam splitter 03 and then enters the optical spatial modulation element. The light, after being spatially modulated by the optical spatial modulation element 04, is transmitted through the first beam splitter 03 and enters the dispersive imaging optical component.

[0049] The dispersive imaging optical component also includes a first lens group 05 and a second beam splitter 06. Light entering the dispersive imaging optical component after being transmitted through the first beam splitter 03 passes through the first lens group 05, the second beam splitter 06, and the telecentric dispersive objective lens 07 in sequence before reaching the surface of the sample 08 to be measured. The light reflected from the surface of the sample 08 to be measured is reflected by the telecentric dispersive objective lens 07 and the second beam splitter 06 and then enters the imaging spectrometer 11. At this time, the optical axis refers to the line connecting the center points of the lens 05 and the lens 07.

[0050] The imaging spectrometer 11 also includes a second lens group 09, which is used to focus the light reflected by the second beam splitter 06.

[0051] The optical spatial modulation element is a digital micromirror array, the polychromatic beam is a linear beam, the first region of the digital micromirror array is in a light-reflecting state, and the other regions are in a non-light-reflecting state. The linear beam is reflected from the first region, which includes one or more rows of the digital micromirror array.

[0052] A micro-aperture array 10 is provided in front of the imaging spectrometer 09, and the micro-aperture array 10 corresponds one-to-one with the optical spatial modulation element 04. The spectroscopic optical component includes a telecentric dispersive objective lens 07, which generates depth of focus in the first spatial direction for light at different positions. In one embodiment of this invention, it is a telecentric dispersive objective lens, which generates depth of focus in the first spatial direction for light at different reflection positions. The telecentric dispersive objective lens arranges the wavelengths in the first spatial direction in a direction that is nearly perpendicular to the normal, for example. This arrangement, firstly, enables higher-precision identification and measurement of the surface Δh of an object, and secondly, enables precise measurement of the corresponding structure for some concave depth structures that are basically parallel to the normal direction.

[0053] The optical spatial modulation element is a digital micromirror array, the polychromatic beam is a linear beam, the first region of the digital micromirror array is in a light flux state, and the other regions are in a non-light flux state. The linear beam passes through the first region, which includes one or more rows of the digital micromirror array.

[0054] The optical spatial modulation element further includes a galvanometer in the first dimension, along the direction of light propagation, which adjusts the spatial position of the light passing through the optical flux unit. The galvanometer is adjustable in position on a plane along the incident light direction. In this way, the digital micromirror array generates a first-level adjustment of the incident light position, followed by a second-level adjustment in the direction of light propagation after passing through the galvanometer.

[0055] The dispersive imaging optical component also has a lens group 05 and a beam splitter 06 arranged sequentially in the incident light path in the direction of light source propagation, and a lens group 07 is also provided between the beam splitter 06 and the micro-aperture array 10 in the reflected light path.

[0056] This invention proposes a spectral confocal three-dimensional measurement system based on a DMD (Digital Micromirror Device). Compared with the mechanical scanning method in point scanning and line scanning systems, this system achieves scanning and measurement of the entire DUT by controlling the DMD to perform spatial light modulation. It is vibration-free and has a fast measurement speed.

[0057] A specific implementation of the DMD-based spectral confocal three-dimensional measurement system has the following optical path structure: Figure 3 As shown. The polychromatic light source 01, after passing through the illumination lens group 02 and the beam splitter prism 03, forms uniform illumination on the DMD (Digital Micromirror Device) 04. The beam splitter prism 03, lens group 05, beam splitter 06, and lens group 07 together constitute a dispersive imaging system, and the DMD is located on the object plane of this dispersive system. The beam reflected by each micromirror element of the DMD, after passing through the dispersive imaging system (composed of the beam splitter prism 03, lens group 05, beam splitter 06, and lens group 07), forms an axially dispersive beam in the sample space 08. The beam reflected from the sample surface, after passing through the lens group 07, beam splitter 06, and lens group 09, is imaged onto the microaperture array 10 for spatial filtering (which can be finely adjusted so that each aperture of the microaperture array corresponds one-to-one with each micromirror of the DMD), and finally coupled into the imaging spectrometer 11.

[0058] This invention achieves sample scanning by controlling the opening or closing of each channel of the DMD, replacing the mechanical scanning method in point scanning and line scanning systems. The specific implementation principle is as follows: In the dispersive imaging system composed of fractional prism 03, lens group 05, beam splitter 06, and lens group 07, the DMD is located on the object plane of the dispersive imaging system, while the sample to be measured is located in the image plane space formed by a series of different wavelengths, which are conjugate.

[0059] When a measurement is required at position I' of the sample, the corresponding column I of the DMD (along the X-axis) is activated, while other columns are deactivated. The polychromatic beam reflected from column I enters the dispersive imaging system and, after passing through the system, forms a series of images at position I' of the sample along the Z-axis. Assuming the surface of sample I' is located on the focal plane formed by the beam with wavelength λ3, the beam reflected from the sample surface, after passing through lens group 07, beam splitter 06, and lens group 09, is imaged onto the microaperture array 10. The corresponding column (along the X-axis) on the microaperture array undergoes spatial filtering, filtering out the beams with wavelengths λ1 and λ2, while the beam with wavelength λ3 remains unaffected and is coupled into the imaging spectrometer 11 through the microaperture array.

[0060] Following the same principle, when it is necessary to measure the position of sample II' or III', column II or column III on the DMD is activated accordingly (one column is activated at a time, and the others are deactivated). Accordingly, the polychromatic beams reflected from column II or III will enter the dispersive imaging system. Assuming that positions II' and III' on the sample surface are located on the focal planes of the λ2 and λ1 component beams, respectively, after spatial filtering by the corresponding columns of the micro-aperture array, the λ2 and λ1 component beams will be coupled into the imaging spectrometer 11, respectively.

[0061] Based on the above principle, by simply turning on one column of the DMD (along the X-axis) and turning off the other columns, the surface of the sample to be tested can be scanned, thus achieving three-dimensional measurement.

[0062] The description in this specification is merely an illustrative example of the present invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the content of this specification or exceed the scope defined in the claims, they shall all fall within the protection scope of this invention.

Claims

1. A spatially modulated spectral confocal three-dimensional measurement system, characterized by, The system includes, Light source (01) is used to generate polychromatic light beams; The optical spatial modulation element (04) is used to adjust the incident spatial position of the incident light from the light source (01) in a time-division manner; Dispersive imaging optical components (05, 06, 07) are used to disperse the polychromatic beam after it has been modulated by the optical spatial modulation element (04) and focus it to different depths in the first spatial direction; After the light is spatially adjusted by the optical spatial modulation element (04), it passes through the dispersive imaging optical components (05, 06, 07) and is incident on different positions on the surface of the sample to be measured (08). After being reflected by the sample to be measured (08), it is coupled into the imaging spectrometer (11). The first spatial direction is the optical axis direction of the dispersive imaging optical components (05, 06, 07) or a direction parallel to the optical axis direction.

2. A spatially modulated spectral confocal three-dimensional measurement system as claimed in claim 1, characterized in that The optical spatial modulation element (04) has multiple optical adjustment units arranged at the incident space position. The multiple optical adjustment units are turned on or off, corresponding to the incident light being reflected or not reflected. The optical spatial modulation element (04) is a digital micromirror array, and the optical adjustment unit is a micromirror.

3. A spatially modulated spectral confocal three-dimensional measurement system as claimed in claim 1, characterized in that The optical spatial modulation element (04) is located on the object plane of the system formed by the dispersive imaging optical components (05, 06, 07).

4. A spatially modulated spectral confocal three-dimensional measurement system as claimed in claim 2, characterized in that The imaging spectrometer (11) is provided with a micro-pore array (10) for spatial filtering, and the micro-pore array (10) corresponds one-to-one with the light adjustment unit in the digital micromirror array.

5. A spatially modulated spectral confocal three-dimensional measurement system according to any one of claims 1 to 4, characterized in that The dispersive imaging optical components (05, 06, 07) include a telecentric dispersive objective (07), so that light from different positions on the surface of the sample to be measured (08) is dispersed by the telecentric dispersive objective (07) in the first spatial direction, generating dispersive light focused at different depths in the first spatial direction.

6. The spatial modulation-based spectral confocal three-dimensional measurement system as described in claim 5, characterized in that, After collimation, the incident light is reflected by the first beam splitter (03) and then incident on the optical spatial modulation element (04). The light, which is spatially modulated by the optical spatial modulation element (04), is transmitted through the first beam splitter (03) and enters the dispersive imaging optical component.

7. A spatially modulated spectral confocal three-dimensional measurement system as claimed in claim 6, characterized in that The dispersive imaging optical components (05, 06, 07) also include a first lens group (05) and a second beam splitter (06). The light that enters the dispersive imaging optical components after being transmitted through the first beam splitter (03) passes through the first lens group (05), the second beam splitter (06), and the telecentric dispersive objective (07) in sequence before reaching the surface of the measurement sample (08). The light reflected from the surface of the measurement sample (08) is reflected by the telecentric dispersive objective (07) and the second beam splitter (06) before entering the imaging spectrometer (11).

8. A spatially modulated spectral confocal three-dimensional measurement system as claimed in claim 7, characterized in that The imaging spectrometer (11) also includes a second lens group (09) for focusing the light reflected by the second beam splitter (06).

9. A spatial modulation based spectroscopic confocal three-dimensional measurement system as claimed in claim 2, characterized in that, The polychromatic beam is a linear beam. The first region of the digital micromirror array is in a light-reflecting state, while the other regions are in a non-light-reflecting state. The linear beam is reflected from the first region, which includes one or more rows of the digital micromirror array.

10. A spatially modulated spectral confocal three-dimensional measurement system as claimed in claim 2, characterized in that The optical spatial modulation element (04) further includes a galvanometer, which performs a second-level adjustment of the incident spatial position of the light passing through the optical adjustment unit.

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