Patent Description:
In recent years, with the rapid development of precision manufacturing, the requirements for measurement technology have greatly increased. Spectral confocal sensor is a non-contact displacement sensor based on wavelength displacement modulation, which has become a hot research topic and been widely used in the fields of film thickness measurement, precision positioning, and precision instrument manufacturing, because its measurement accuracy reaches sub-micron or even nanometer level, and it is not sensitive to object tilt and surface texture, etc., it also has strong stray light resistance ability.

The spectral confocal measurement system based on spectral confocal technology uses a light source to irradiate the surface of the object to be measured, and reflected spectral information is detected by a CCD industrial camera or spectrometer, etc., to determine the peak wavelength focused on the surface of the object, thereby obtaining axial distance information of the surface of the object to be measured. The principle is to use a dispersive objective lens group to focus and disperse the light from the light source, and form a continuous monochromatic light focus on the optical axis with different distances to the dispersive objective lens group, thereby establishing a linear relationship between wavelength and axial distance, and then use the spectral information reflected by the surface of the object to be measured to obtain the corresponding position information.

<FIG> shows an existing spectral confocal measurement device. The light is emitted from the light source <NUM>', enters the coupling portion <NUM>' to be transmitted to the sampling portion <NUM>', and then is projected to the measured object <NUM>' which reflects a reflected light carrying measurement information to return back to the coupling portion <NUM>'along the original light path. Subsequently, partial or all of the reflected light passes through the beam splitter <NUM>', and is finally converted into an electrical signal by the sensor <NUM>', thereby analyzing and obtaining location measurement results.

In this measurement device and method, since the reflected light returns to the light-incident hole along a reverse direction of the incident light path, the purity of the spectrum received by the light-incident hole is not high, which leads to deviations in measurement results and reduces measurement accuracy. Application <CIT> discussed a chromatic confocal measurement device using a plurality of wavelengths and a plurality of beam splitters. Application <CIT> discussed a confocal distance sensor emitting an illumination light with different spectral components to reach onto the measurement object surface.

Therefore, there is an urgent need for an improved spectral confocal measurement device and measurement method to overcome the above shortcomings.

One objective of the present invention is to provide a spectral confocal measurement device, thereby improving measurement accuracy and reducing production cost.

Another objective of the present invention is to provide a spectral confocal measurement method, thereby improving measurement accuracy and reducing production cost.

To achieve the above-mentioned objective, the present invention provides a spectral confocal measurement device according to claim <NUM>.

Preferably, the light source portion further includes a focusing lens located below the light source.

Preferably, the optical sampling portion further includes a reflecting mirror located between the dispersive objective lens group and the light-incident hole, the reflecting mirror is arranged on an axis of the dispersive objective lens group, and configured to receive the reflected light output from the dispersive objective lens group and guide the reflected light to the light-outgoing hole.

Preferably, the light source portion further includes a reflecting mirror located between the focusing lens and the light-incident hole, the reflecting mirror is arranged on an axis of the dispersive objective lens group, and configured to receive the reflected light output from the dispersive objective lens group and guide the reflected light to the light-outgoing hole, and the light-outgoing hole and the light-incident hole are the same hole.

Preferably, the dispersive objective lens group includes a first-stage dispersive objective lens group located below the light source and a second-stage dispersive objective lens group located below the first-stage dispersive objective lens group.

Preferably, a diaphragm is provided between the first-stage dispersive objective lens group and the second-stage dispersive objective lens group.

Preferably, the measurement portion includes:.

Accordingly, the present invention provides a spectral confocal measurement method according to claim <NUM>.

In comparison with the prior art, a specific optical path is configured in the spectral confocal measurement device and method of the present invention, specifically, the incident measurement beam is emitted along a first predetermined path and reflected along a second predetermined path that is different from the opposite direction of the first predetermined path. In such a way, undesired beams are filtered, so that the purity of the spectrum of the emitted light can be improved, and the measurement accuracy of the subsequent measurement portion is improved accordingly.

The present invention will become clearer through the following description in conjunction with the accompanying drawings, which are used to explain the embodiments of the present invention.

A distinct and full description of the technical solution of the present invention will follow by combining with the accompanying drawings.

As described above, the essence of the present invention is to provide an improved spectral confocal measurement device and measurement method thereof, which optimizes the light path by controlling the direction of incident light, thereby improving measurement accuracy and reducing production costs.

Referring to <FIG>, a spectral confocal measurement device <NUM> includes a light source portion <NUM>, an optical sampling portion <NUM> and a measurement portion <NUM>. Specifically, the light source portion <NUM> is configured to emit a broad-spectrum light beam with a certain wavelength range in a first predetermined path; the optical sampling portion <NUM> is configured to converge the broad-spectrum light beam emitted from the light source portion <NUM> on different measurement surfaces of an object to be measured, and output a reflected light in a second predetermined path that is different from a reverse direction of the first predetermined path; and the measurement portion <NUM> is configured to receive and process the reflected light from the optical sampling portion <NUM> to obtain a measurement result.

Specifically, as shown in <FIG>, the light source portion <NUM> is encapsulated by a housing 210a and includes a light source <NUM>, a light source controller <NUM> connected to the light source <NUM>, and a focusing lens <NUM> located below the light source <NUM>. The light source <NUM> may be a point light source or a line light source, such as an LED light source, a laser, or other light sources such as mercury vapors. Specifically, the light source <NUM> is configured to emit continuous visible light beams having different wavelengths from the blue wavelength range to the red wavelength range as the measurement light. The light source controller <NUM> is configured to control the direction and path of the incident light of the light source, thereby optimizing the direction and the path of the outgoing light. In view of the difference between the point light source and the line light source, the direction and the path of the outgoing light of the present invention are different, which will be described in detail below in conjunction with different embodiments. Since the light beam needs to be focused before entering the optical sampling portion <NUM>, the focusing lens <NUM> is arranged on the optical sampling portion <NUM>.

The light source portion <NUM> and the optical sampling portion <NUM> are connected, by an optical fiber, for example, and a light-incident hole (that is, a port) is provided therebetween, and the light-incident hole is provided at the focal point of the focusing lens <NUM>. Specifically, the optical sampling portion <NUM> is encapsulated by a housing 220a, and includes a light-incident hole <NUM>, a dispersive objective lens group <NUM>, a light-outgoing hole <NUM> and a reflecting mirror <NUM>. Specifically, the light-incident hole <NUM> and the light-outgoing hole <NUM> are arranged on the housing 220a, the dispersive objective lens group <NUM> is arranged in the housing 220a, and the reflecting mirror <NUM> is located between the dispersive objective lens group <NUM> and the light-incident hole <NUM>, and located at the axis of the dispersive objective lens group <NUM>. Further, the light-outgoing hole <NUM> is located on the other side of the housing 220a to connect with the measurement portion <NUM>. Optionally, the light-outgoing hole <NUM> can be a pinhole or an aperture. The shape of the housing 220a of the optical sampling portion <NUM> can be set according to actual requirements, which is not limited.

Specifically, a measurement beam emitted from the light source portion <NUM> is emitted to inside of the housing of the optical sampling portion <NUM> by passing through the focusing lens <NUM> and the light-incident hole <NUM>, and then passes through the dispersive objective lens group <NUM> and is emitted to a measurement surface S from an irradiation surface 220b provided at the front end of the housing. The dispersive objective lens group <NUM> is at least one lens involved in the spectral confocal sensor and configured to generate axial chromatic aberration. Specifically, the dispersive objective lens group <NUM> is configured to focus the light incident on the optical sampling portion <NUM> at a focal position of the optical axis corresponding to the wavelength. Therefore, the light beams of different wavelengths contained in the corresponding light source are focused to different focus positions. Generally, the light source includes continuous visible light beams with a certain wavelength range, for example, light beams of red, green and blue are separated from each other and emitted from the irradiation surface of the housing to the measurement surface. It should be noted that, light with other colors and other wavelengths may also be emitted.

Specifically, the measurement beam is reflected by the measurement surface, passes through the dispersive objective lens group <NUM> to enter the reflecting mirror <NUM>, and then is guided to the light-outgoing hole <NUM>, to reach the measurement portion <NUM> finally.

Specifically, the measurement portion <NUM> includes a spectrometer <NUM>, a sensor <NUM>, and a processor (not shown). The spectrometer <NUM> is configured to receive and process the reflected light from the optical sampling portion <NUM>, the sensor <NUM> is configured to convert the reflected light from the spectrometer <NUM> into an electrical signal, and the processor is configured to calculate a measurement result according to the electrical signal of the sensor <NUM>.

As shown, the spectrometer <NUM> includes a collimator lens <NUM>, a diffraction grating <NUM>, and a focusing lens <NUM>. The collimator lens <NUM> is configured to make the measurement beam emitted from the light-outgoing hole irradiate to the diffraction grating <NUM> in a substantially collimated manner, the diffraction grating <NUM> is configured to diffract the substantially collimated measurement beam, and the focusing lens <NUM> is configured to image the diffracted light diffracted by the diffraction grating <NUM> on the sensor <NUM>. Normally, +<NUM>-order diffracted light is imaged on the sensor <NUM>, but other diffracted light such as of -<NUM>-order diffracted light may also be imaged. It should be noted that the specific structure and configuration of the diffraction grating <NUM> is not limited.

It should be noted that the focusing lens <NUM> is a lens with small chromatic aberration, and can image diffracted light on the sensor <NUM> regardless of the wavelength of the measurement light.

The specific structure of the sensor <NUM> is not limited. For example, a CMOS line sensor or a CCD line sensor can be used. The sensor <NUM> is configured to convert the measurement light into an electrical signal and transmit the electrical signal to the processor. Based on the received signal, the processor can calculate the position of the object to be measured. The specific calculation method may refer to the prior art, which will not be described in detail here.

The light path control of the present invention will be described in detail below according to several embodiments.

As shown in <FIG>, under the control of the light source controller <NUM>, a measurement beam is emitted from the point light source <NUM> to enter the focusing lens <NUM> in the form of a whole light beam (that is, the beam that does not shield any area), and then is focused on the light-incident hole <NUM> to enter the housing 220a of the optical sampling portion <NUM>, and then enters the dispersive objective lens group <NUM> in a predetermined direction in a form of an annular light beam (that is, the beam that shields the central area), as shown by the arrow A1 in the figure. It should be noted that, the first predetermined path (that is the light incident path) of the point light source <NUM> in the disclosure is defined as follow: the light beam from the light source enters the dispersive objective lens group <NUM> through the light-incident hole <NUM>, and then reaches the measurement surface S. The second predetermined path (that is the light outgoing path) of the point light source <NUM> in the disclosure is defined as follow: the light beam reflected from the measurement surface S passes through the dispersive objective lens group <NUM>, and then passes through the light-outgoing hole to enter the measurement portion <NUM>. The first predetermined path described herein may refer to a complete or partial light path, and the second predetermined path described herein may refer to a complete or partial light path. As shown in <FIG>, the first predetermined path is A1+a1, and the second predetermined path is C1+c1. As shown, taking the measurement surface S of the object as the reference, the dispersive objective lens group <NUM> is parallel to the measurement surface S, and the measurement beam of the point light source is emitted at a certain angle with the measurement surface S along a predetermined path A1 to the dispersive objective lens group <NUM>. Specifically, the measurement beam is emitted in the form of annular light beam, with the beam at the center being shielded, and then passes through the dispersive objective lens group <NUM> to reach the measurement surface S, and then the reflected light from the measurement surface S passes through the central part of the dispersive objective lens group <NUM> along the path of C1, finally, the beam is reflected from the reflecting mirror <NUM> to the light-outgoing hole <NUM>. It can be seen that the light outgoing path of the measurement beam does not return from the original light incident path, but takes the above-mentioned specific path. In such an arrangement, inconsistent and undesirable beams are filtered, so that the purity of the spectrum of the emitted light can be improved, thereby improving the measurement accuracy of the subsequent measurement portion.

Preferably, the light source <NUM>, the focusing lens <NUM>, the light incident hole <NUM>, the dispersive objective lens group <NUM>, and the measurement surface S and the reflecting mirror <NUM> are arranged coaxially, that is, their centers are located on the same straight line. In such an arrangement, the volume of the entire spectral confocal measurement device can be reduced, thereby reducing production costs.

In addition, the measurement accuracy is greatly improved by the above-mentioned light path control. The number of dispersive objective lenses in the dispersive objective lens group <NUM> in the optical sampling portion <NUM> of the present invention is not limited, and can be set to one or more to meet different design requirements.

<FIG> shows an example using a point light source. The differences from the first embodiment include: the light outgoing manner of the point light source <NUM> before entering the optical sampling portion <NUM>, the arrangement of the light-incident hole, and the arrangement of the reflecting mirror <NUM>' for guiding the light to the measurement portion <NUM>.

Specifically, as shown, the central light of the measurement beam emitted from the point light source <NUM> is shielded, that is, the measurement beam in the form of annular light beam is emitted into the focusing lens <NUM>, and then is focused on the light-incident hole <NUM> to enter the housing 220a of the optical sampling portion <NUM>, and then enters the dispersive objective lens group <NUM> in the form of annular light beam. The specific light incident paths A2 and a2 are the same with the paths A1 and a1 in the above embodiment, but the light outgoing paths are different. Specifically, the reflecting mirror <NUM>' for guiding light in this embodiment is provided at the light source portion <NUM> instead of the optical sampling portion <NUM>. That is, the reflecting mirror <NUM>' is located between the focusing lens <NUM> and the light incident hole <NUM>, and the reflecting mirror <NUM>' is arranged on the axis of the dispersive objective lens group <NUM>. In other words, the light-outgoing hole and the light-incident hole in this embodiment are the same hole. When the light outputs, after the measurement beam is reflected from the measurement surface S, the reflected light passes through the center part of the dispersive objective lens group <NUM> along the path C2, and then passes through the light-incident hole <NUM> again to enter the reflecting mirror <NUM>' in the light source portion <NUM>, and finally is directly guided to the measurement portion <NUM> by the reflecting mirror <NUM>'. That is, the light outgoing path includes C2 and c2. Such a specific light path can also filter out non-conforming and undesirable light beams, so that the purity of the spectrum of the emitted light can be improved, thereby improving the measurement accuracy of the subsequent measurement portion. In this embodiment, since the light incident and light reflection share the same light-incident hole, the installation and debugging efficiency is higher therefore.

The measurement portion <NUM> has the same structure as that in the first embodiment, which will not be repeated here.

As a third embodiment, <FIG> shows another measurement structure and light path control. In the embodiment, either a line light source or a point light source can be served as the incident light source. Taking the line light source <NUM>' as an example, differing from the previous two embodiments, a two-stage dispersive objective lens group including a first-stage dispersive objective lens group 222a, a second-stage dispersive objective lens group 222b is included in this embodiment, that is, the first-stage dispersive objective lens group 222a, the second-stage dispersive objective lens group <NUM> and the measurement surface S are arranged coaxially from up to bottom (as shown in <FIG>). Under the control of the light source controller, the measurement beam of the linear light source <NUM>' passes through the light-incident slit <NUM>' and only enters the single side of the first-stage dispersive objective lens group 222a and then enter the single side of the second stage dispersive objective lens group 222b along the first predetermined path A3, and reaches the measurement surface S. Subsequently, the measurement beam is reflected from the measurement surface S and emitted from the opposite symmetrical side of the second-stage dispersive objective lens group 222b along the second predetermined path C3, and then is reflected to the light-incident slit <NUM>' of the line light source, and then enters the measurement portion (not shown) located on one side of the light-incident slit <NUM>' for measurement. In this light path control manner, only the beam with a specific wavelength on the confocal line can enter the dispersive lens group through the measurement surface and finally enter the measurement portion (imaging system) through the light-incident slit <NUM>', and the undesirable beam cannot enter the measurement portion. As a result, the interference of other reflection wavelengths outside the confocal line is effectively reduced, so that the test sensitivity is higher and the measurement accuracy is improved. The measurement portion in this embodiment has the same structure as that in the first embodiment, which will not be repeated here.

<FIG> show the structure and light path control of another preferred embodiment of the spectral confocal measurement device of the present invention. In this embodiment, the confocal measurement device uses a linear light source. Similarly as the embodiment as shown in <FIG>, the light source <NUM> and the measurement portion <NUM> are located on the same side of the light-incident slit <NUM>', the first-stage dispersive objective lens group 222a and the second-stage dispersive objective lens group 222b are arranged coaxially. Differing from the previous embodiment, a diaphragm <NUM> is provided between the first-stage dispersive objective lens group 222a and the second-stage dispersive objective lens group 222b. As shown in <FIG>, the diaphragm <NUM> is provided with two channels 26a and 26b, respectively, for allowing the beams to input or output. Preferably, the shape of the two channels is square, but other shapes are also available. With the help of the diaphragm <NUM>, the light incident path and the light reflection path can be effectively separated, so that stray light can be filtered, thereby reducing the interference of other reflection wavelengths beyond the confocal line.

The specific light path control follows. Under the control of the light source controller, the measurement beam of the light source <NUM> passes through the light-incident slit <NUM>', enters from the single side of the first-stage dispersive objective lens group 222a along the first predetermined path A4, then passes through the light-incident port 26a of the diaphragm <NUM> to enter the single side of the second-stage dispersive objective lens group 222b, and then reaches the measurement surface S. The measurement beam is then reflected from the measurement surface S and emitted along the second predetermined path C4 from the opposite symmetrical side of the second-stage dispersive objective lens group 222b. Specifically, the reflected beam is emitted from the second-stage dispersive objective lens group 222b, then passes through the light-outgoing port 26b of the diaphragm <NUM> to pass through the light entrance slit <NUM>', and finally enters the measurement portion <NUM> located on the side of the light-incident slit <NUM>' to make the measurements.

It is should be noted that, the focusing lens and the reflecting mirror shown in <FIG> are not required in this embodiment shown in <FIG> and <FIG>, and therefore the structure is more simpler.

<FIG> and <FIG> respectively show examples of the spectral confocal measurement of the present invention, wherein <FIG> is a modified example of <FIG>, and <FIG> is a modified example of <FIG>. The light path of the two embodiments is opposite to the foregoing path: the dispersive objective lens group is used as the description reference, the measurement beam enters from the central area of the dispersive objective lens group, and the reflected measurement beam is emitted from the outer periphery of the dispersive objective lens group in the form of an annular light beam. The specific light path control and structure follow. The specific light paths in the two embodiments may filter out non-conforming and undesirable light beams, so that the purity of the spectrum of the emitted light can be improved, thereby improving the measurement accuracy of the subsequent measurement portion.

An example shown in <FIG> is obtained by interchanging the positions of the light source portion and the measurement portion shown in <FIG>. That is, the light source <NUM> in the light source portion <NUM> emits the measurement beam towards the housing of the optical sampling portion <NUM> through the focusing lens <NUM> and the light-incident hole <NUM>, and the measurement beam is reflected by the reflected mirror <NUM>, and then passes through the central part of the dispersive objective lens group <NUM>, and reaches the measurement surface S, as shown the local light incident path indicated by sections A5+a5. Then, the light beam reflected from the measurement surface S passes through the periphery of the dispersive objective lens group in a form of annular light beam, and then enters the measurement portion <NUM> from the light-outgoing hole <NUM>, as shown the local light outgoing path indicated by C5+c5.

Similarly, an example shown in <FIG> is obtained by interchanging the positions of the light source portion and the measurement portion shown in <FIG>, and the light-incident hole <NUM> and the light-outgoing hole <NUM> still share the same hole. It should be noted that the position of the reflecting mirror <NUM>' remains unchanged. As shown in <FIG>, the light from the light source <NUM> in the light source portion <NUM> is focused onto the reflecting mirror <NUM>' through the focusing lens <NUM>, and then is guided through the light-incident hole <NUM> to enter the interior of the optical sampling portion <NUM>, specifically passes from the central part of the dispersive objective lens group <NUM> to reach the measurement surface S, as shown the local light incident path indicated by sections A6+a6. Then, the light beam reflected from the measurement surface S passes through the periphery of the dispersive objective lens group in a form of annular light beam, and then enters the measurement portion <NUM> from light-incident hole <NUM> again, as shown the local light outgoing path indicated by C6+c6.

Accordingly, the present invention further discloses a spectral confocal measurement method according to claim <NUM>.

In summary, a specific optical path is configured in the spectral confocal measurement device and method of the present invention, specifically, the incident measurement beam is emitted along a first predetermined path and reflected along a second predetermined path that is different from the opposite direction of the first predetermined path. In such a way, undesired beams are filtered, thereby effectively reducing the interference of other reflected wavelengths beyond the confocal line, so that the purity of the spectrum of the emitted light can be improved, and the test sensitivity and measurement accuracy of the subsequent measurement portion are improved accordingly. Moreover, the device has a simple structure to reduce production costs.

Claim 1:
A spectral confocal measurement device (<NUM>), comprising:
a light source portion (<NUM>), configured to emit a broad-spectrum light beam with a certain wavelength range in a first predetermined path;
an optical sampling portion (<NUM>), configured to converge the broad-spectrum light beam emitted from the light source portion (<NUM>) on different measurement surfaces of an object to be measured, and output a reflected light in a second predetermined path that is different from a reverse direction of the first predetermined path; and
a measurement portion (<NUM>), configured to receive and process the reflected light from the optical sampling portion to obtain a measurement result;
wherein the light source portion (<NUM>) comprises a light source (<NUM>') and a light source controller (<NUM>) connected to the light source (<NUM>') and the optical sampling portion (<NUM>) comprises a light-incident hole (<NUM>'), a dispersive objective lens group (<NUM>) and a light-outgoing hole (<NUM>') the light source (<NUM>') is a line light source, under controls of the light source controller (<NUM>), the broad-spectrum light beam of the line light source is emitted through the light-incident hole (<NUM>') and then into a first side of the dispersive objective lens group (<NUM>) and reaches the measurement surface through the first predetermined path; and the second predetermined path follows: the reflected light reflected from the measurement surface is output from a second side of the dispersive objective lens group (<NUM>) that is opposite to the first side, and enters the measurement portion through the light-outgoing hole (<NUM>'), characterised in that the light-outgoing hole (<NUM>') and the light-incident hole (<NUM>') are the same hole.