Optimized diffusion sheet position adjusting method of Kohler lighting system

Abstract

The invention provides a method for adjusting the position of an optimized diffusion sheet of a Kohler lighting system, which is used for correcting the Kohler lighting system, and comprises the following steps: firstly, when a diffusion sheet rotates, acquiring an initial dynamic image of a measured object when the diffusion sheet is positioned at an initial position by using an image sensor; analyzing whether a deviation displacement vector of at least one speckle is converged in a preset range or not according to the initial dynamic image of the measured object; then, if the deviation displacement vector of the speckle is kept converged in a preset range, defining the initial position of the diffusion sheet as an optimized diffusion sheet position with the optimal light field uniformity, otherwise, adjusting the position of the diffusion sheet until the deviation displacement vector of the speckle is kept converged in the preset range, and defining the corrected position of the diffusion sheet as the optimal position with the optimal light field uniformity.

Description

Technical Field

[0001] The present invention relates to a method for adjusting an illumination system, and more particularly to a method for adjusting an optimal object distance of a Kohler illumination system. Background Art

[0002] In existing optical measurement technology, in order to effectively collect the image of the sample, a suitable light source must be used for illumination, and the illumination methods are divided into critical illumination and Kohler illumination ( There are two types of illumination, critical illumination, in which the characteristics of the light source itself will be displayed in the image of the sample, overlapping and causing interference. Therefore, in the existing optical field, the Kohler illumination technology is mainly used to provide uniform illumination.

[0003] See also Figure 1 , Figure 1 A schematic plan view of a Kohler illumination system of the prior art is shown. Figure 1 As shown, a Kohler illumination system PA100 includes an illumination light source PA1, a light collecting lens PA2, a diffuser PA3, a focusing lens PA4, a beam splitter PA5, an objective lens PA6, a tube lens PA7 and an image sensor PA8; wherein the diffuser PA3 is rotatably disposed between the illumination light source PA1 and the light collecting lens PA2, so that a laser beam PALB projected by the illumination light source PA1 is evenly diffused by the rotation of the diffuser PA3, and then irradiates the object to be measured located on an illuminated surface PAIP in sequence through the light collecting lens PA2, the focusing lens PA4, the beam splitter PA5 and the objective lens PA6, and then the image sensor PA8 collects the image of the object to be measured reflected on the illuminated surface PAIP through the tube lens PA7, the beam splitter PA5 and the objective lens PA6.

[0004] Please continue reading Figure 2 , Figure 2 It shows that when the existing Kohler illumination system uses laser as the illumination light source, the random speckle image presented by the illuminated surface is collected when the diffuser PA3 is stationary. Figure 1 and Figure 2 As shown, in some optical applications, in order to achieve sufficient power density (generally known as brightness), a laser with high coherence must be used as the illumination light source PA1. However, when a laser is used as the illumination light source PA1, when the diffuser PA3 is stationary, the image sensor PA8 will capture a speckle image SI containing multiple speckle noises on the illuminated surface PAIP, and the presence of speckle will cause serious uneven illumination, making the image captured by the image sensor PA8 almost unrecognizable.

[0005] As mentioned above, in order to reduce the negative impact of speckle, the prior art generally sets a diffuser PA3 between the illumination light source PA1 and the light collecting lens PA2, and uses the rotation of the diffuser PA3 to make the laser light pass through the rotating diffuser PA3 to form an equivalent light source, and then pass through the light collecting lens PA2 and the focusing lens PA4 to focus on the back focal plane of the objective lens PA6, and then projected on the object to be measured (not shown) located on the illuminated surface PAIP through the objective lens PA6; thereby, from the equivalent light source to the illuminated surface PAIP is a typical Kohler illumination architecture. Subsequently, the light is reversed through the objective lens PA6, the beam splitter PA5 and the tube lens PA7 to form an image on the image sensor PA8, and the observed image is effectively uniformed during the exposure time due to the rotation of the diffuser PA3. This type of technology is generally referred to as despeckle technology.

[0006] From the above description, it can be seen that the purpose of rotating the diffuser PA3 is to achieve the effect of eliminating speckles (achieving uniform illumination on a smaller scale), while the purpose of the Kohler illumination system PA100 is to achieve uniform illumination of the macroscopic view. In order to achieve uniform illumination of the macroscopic view, the position of the diffuser PA3 (i.e., the equivalent light source) must be properly adjusted so that the diffuser PA3 and the illuminated surface PAIP satisfy the optical Fourier plane relationship.

[0007] Generally speaking, a person skilled in the art can preliminarily set the relative positions of the diffuser PA3, the image sensor PA8 and the above objects through the optical mechanism according to the nominal specifications of the light collecting lens PA2, the focusing lens PA4, the objective lens PA6 and the tube lens PA7. However, in practice, due to various processing and assembly errors, the position of the diffuser PA3 usually fails to form the best macroscopic uniform illumination on the illuminated surface PAIP (equivalent to the conjugate surface of the image sensor PA8). At this time, it is necessary to place a standard object to be tested on the illuminated surface PAIP, observe the illumination distribution on the standard object to be tested through the image sensor PA8, and then fine-tune the position of the diffuser PA3 so that the illumination distribution on the standard object to be tested presents the best macroscopic uniform illumination. However, since the laser beam passing through the diffuser PA3 will cause the image observed by the image sensor PA8 to have strong random speckles, it is difficult to judge whether the standard object to be tested presents macroscopic uniform illumination. Therefore, an effective judgment and adjustment method is needed to judge and adjust the optimal setting position of the diffuser PA3. Summary of the invention

[0008] In view of the prior art, although the existing Kohler illumination system can provide higher illumination brightness through the laser light source, in order to eliminate the speckle generated when using the laser light source, a diffuser is usually set, and the light field is made uniform by rotating the diffuser. However, in actual use, the setting position of the diffuser often does not necessarily make the illuminated surface align with the object to be tested, so the object to be tested cannot be illuminated in the most uniform way. Therefore, the main purpose of the present invention is to provide an optimized diffuser position adjustment method for the Kohler illumination system, which can effectively find the optimal diffuser setting position so that the object to be tested can be illuminated by a uniform light field.

[0009] The present invention solves the problems of the prior art. The necessary technical means adopted by the present invention is to provide a method for calibrating the position of an optimized diffuser of a Kohler illumination system, which is used to calibrate a Kohler illumination system. The Kohler illumination system includes a laser light source, a collector, a diffuser, a focusing lens, a beam splitter, an objective lens, a tube lens, and an image sensor. The diffuser is rotatably disposed between the laser light source and the collector, so that a laser beam projected by the laser light source is uniformly diffused by the rotation of the diffuser, and then irradiated to a device under test (DUT) in sequence through the collector, the focusing lens, the beam splitter, and the objective lens, so that the image sensor collects an image reflected by the DUT through the tube lens, the beam splitter, and the objective lens. The calibration method of the Kohler illumination system includes the following steps (A) to (C).

[0010] First, step (A) is to use the image sensor to capture an initial dynamic image of the object under test when the diffuser is at an initial position, and analyze whether a deviation displacement vector of at least one speckle in the initial dynamic image of the object under test remains within a predetermined range.

[0011] Next, in step (B), if the deviation displacement vector of the at least one speckle in step (A) remains within the predetermined range, the initial position of the diffuser is defined as an optimized diffuser position with the best light field uniformity; otherwise, step (C) is continued.

[0012] Finally, step (C) is to adjust the position of the diffuser if the deviation displacement vector of the at least one speckle in step (A) exceeds the predetermined range until the deviation displacement vector of the at least one speckle remains within the predetermined range, and define a corrected position of the diffuser after adjustment as the optimized diffuser position with the best light field uniformity.

[0013] In an auxiliary technical means derived from the above necessary technical means, the laser light source has an optical axis, and the step (C) further includes the following steps (C1) to (C4).

[0014] Step (C1) is to move the diffuser to a first calibration position along a first direction parallel to the optical axis, so as to use the image sensor to capture a first calibrated dynamic image of the object under test, and analyze the first calibrated dynamic image to see whether the deviation displacement vector of the at least one speckle remains within the predetermined range.

[0015] Step (C2) is to define the first correction position of the diffuser as the optimized diffuser position with the best light field uniformity if the deviation displacement vector of the at least one speckle in step (C1) remains converged within the predetermined range; otherwise, continue to execute step (C3).

[0016] Step (C3) is to move the diffuser along the first direction or a second direction opposite to the first direction to a second calibration position to collect a second calibration dynamic image of the object under test by using the image sensor if the deviation displacement vector of the at least one speckle in step (C1) exceeds the predetermined range, and analyze the second calibration dynamic image to see whether the deviation displacement vector of the at least one speckle remains within the predetermined range. If the deviation displacement vector of the at least one speckle remains within the predetermined range, the calibrated position of the diffuser at the second calibration position is defined as the optimized diffuser position with the best light field uniformity. Otherwise, step (C4) is continued.

[0017] Step (C4) is to repeat step (C1) to step (C3) until the deviation displacement vector of the at least one speckle remains within the predetermined range, and the diffuser position is defined as the optimized diffuser position with the best light field uniformity.

[0018] As described above, in the step (C3), when the vector magnitude of the deviation displacement vector of the at least one speckle in the step (C1) exceeds the predetermined range, and the vector direction of the deviation displacement vector of the at least one speckle in the step (C1) is opposite to the vector direction of the deviation displacement vector measured when the diffuser is located at the previous position, the diffuser is moved along the second direction opposite to the first direction to the second correction position.

[0019] In addition, in the step (C3), when the vector magnitude of the deviation displacement vector of the at least one speckle in the step (C1) exceeds the predetermined range, if the direction of the deviation displacement vector of the at least one speckle in the step (C1) is the same as the direction of the deviation displacement vector measured when the diffuser is located at a previous position, but the magnitude of the deviation displacement vector of the at least one speckle in the step (C1) is smaller than the vector magnitude of the deviation displacement vector measured when the diffuser is located at the previous position, the diffuser is moved along the first direction to the second correction position.

[0020] In contrast, in the step (C3), when the vector magnitude of the deviation displacement vector of the at least one speckle in the step (C1) exceeds the predetermined range, if the direction of the deviation displacement vector of the at least one speckle in the step (C1) is the same as the direction of the deviation displacement vector measured when the diffuser is located at a previous position, but the magnitude of the deviation displacement vector of the at least one speckle in the step (C1) is greater than the vector magnitude of the deviation displacement vector measured when the diffuser is located at the previous position, the diffuser is moved along the second direction opposite to the first direction to the second correction position.

[0021] In one embodiment, the diffuser moves along the first direction to approach the light collecting lens, and moves along the second direction to move away from the light collecting lens; in another embodiment, the diffuser moves along the first direction to move away from the light collecting lens, and moves along the second direction to approach the light collecting lens.

[0022] Preferably, the step (A) utilizes a computer host electrically connected to the image sensor to perform image analysis on the initial dynamic image of the object being measured, the step (C1) utilizes the computer host to perform image analysis on the first dynamic image, and the step (C3) utilizes the computer host to perform image analysis on the second dynamic image.

[0023] In addition, the first corrected dynamic image includes two first corrected static images, and the two first corrected static images have a time difference between each other. The second corrected dynamic image includes two second corrected static images, and the two second corrected static images have a time difference between each other.

[0024] In an auxiliary technical means derived from the above necessary technical means, the initial dynamic image of the object to be measured includes two initial static images, and the two initial static images have a time difference between each other.

[0025] As described above, the present invention mainly uses an image sensor to first collect an initial dynamic image of the object to be measured when the diffuser rotates, so as to analyze whether the deviation displacement vector of the speckle remains converged within a predetermined range, and then judge whether the diffuser is in an optimized position. If not, the position is continuously adjusted until the speckle position of the collected image is in a pattern of increasing and decreasing in situ, which means that the corrected position of the diffuser is the optimized position with the best light field uniformity.

[0026] The specific embodiments of the present invention will be further described through the following embodiments and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic plan view showing a Kohler illumination system of the prior art;

[0028] Figure 2 It shows that when the existing Kohler illumination system uses laser as the illumination light source, it collects random speckle images presented by the illuminated surface;

[0029] Figure 3 A schematic diagram showing a Kohler illumination system in which an object to be measured is placed on an illuminated surface and applied to the method for adjusting the position of an optimized diffuser of the Kohler illumination system of the present invention;

[0030] Figure 4 A schematic diagram showing the initial dynamic image of the object to be measured collected by the image sensor in the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention;

[0031] Figure 5 A schematic diagram showing the deviation displacement vector generated by using a cross-correlation function to analyze the initial dynamic image of the object to be measured in the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention;

[0032] Figure 6 A schematic plan view showing the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention, in which the object to be measured is moved along a first direction to a first calibration position when the deviation displacement vector of the speckle of the initial dynamic image of the object to be measured is analyzed and does not remain converged within a predetermined range;

[0033] Figure 7 A schematic diagram showing a first calibrated dynamic image captured by an image sensor in the method for calibrating the optimal diffuser position of a Kohler illumination system of the present invention;

[0034] Figure 8 A schematic diagram showing the deviation displacement vector generated by analyzing the first calibration dynamic image using a cross-correlation function in the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention;

[0035] Fig. 9A schematic plan view showing the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention, in which the diffuser is moved along the second direction to a second calibration position when the deviation displacement vector of the speckle of the first calibration dynamic image is analyzed and does not remain converged within a predetermined range;

[0036] Fig.10 A schematic diagram showing a second calibration dynamic image captured by an image sensor in the method for adjusting the position of an optimized diffuser of a Kohler illumination system of the present invention;

[0037] Fig.11 A schematic diagram showing the deviation displacement vector generated by analyzing the second corrected dynamic image using a cross-correlation function in the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention;

[0038] Fig.12 A schematic plan view showing the deviation displacement vector corresponding to the diffuser moving from an initial position along a first direction to a first calibration position, and from the first calibration position along a second direction to a second calibration position in the optimal diffuser position adjustment method of the Kohler illumination system of the present invention;

[0039] Fig.13 A schematic plan view showing the method for adjusting the position of the diffuser of the Kohler illumination system according to the present invention, wherein the diffuser is moved along a first direction to a first calibration position, and then moved along the first direction to a second calibration position;

[0040] Fig.14 show Fig.13 A plan view of a diffusion sheet moving from an initial position along a first direction to a first correction position and a deviation displacement vector corresponding to a second position;

[0041] Fig.15 A schematic plan view showing the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention, wherein after the diffuser is moved to a first calibration position along a first direction away from or close to the light collecting mirror, the diffuser needs to be moved along an opposite second direction because the deviation displacement vector still does not remain converged within a predetermined range; and

[0042] Fig.16 show Fig.15 A plan view of a deviation displacement vector corresponding to a diffuser moving along a first direction away from or close to a light collecting mirror to a first correction position.

[0043] Wherein, the reference numerals are:

[0044] PA100: Kohler Lighting System

[0045] PA1: Lighting source

[0046] PA2: Light collecting mirror

[0047] PA3: Diffuser

[0048] PA4: Focusing lens

[0049] PA5: Beamsplitter

[0050] PA6:Objective lens

[0051] PA7: Tube lens

[0052] PA8: Image Sensor

[0053] PALB: Laser Beam

[0054] PAIP: illuminated surface

[0055] SI: Speckle Imaging

[0056] 100: Kohler Lighting System

[0057] 1: Laser light source

[0058] 2: Light collecting mirror

[0059] 3: Diffuser

[0060] 4: Focusing lens

[0061] 5: Beam splitter

[0062] 6: Objective lens

[0063] 7: Tube mirror

[0064] 8: Image sensor

[0065] DUT: Object under test

[0066] LB:Laser beam

[0067] OA: Optical Axis

[0068] SI1: Initial dynamic image of the object being measured

[0069] SI1a, SI1b: Initial static image

[0070] SI2: First calibration dynamic image

[0071] SI2a, SI2b: First calibrated static image

[0072] SI3: Second Correction Dynamic Image

[0073] SI3a, SI3b: Second Corrected Still Image

[0074] S1, S1a, S2, S2a, S3, S3a: Speckle

[0075] SR: Reserved Range

[0076] dV0,dV1,dV1a,dV1b,dV2,dV2a: deviation displacement vector

[0077] D1, D1b: First direction

[0078] D2, D2b: Second direction

[0079] P0: Initial position

[0080] P1, P1a, P1b, P1c: First calibration position

[0081] P2, P2a: Second calibration position

[0082] CC1, CC2, CC3: images of cross-correlation operation results. DETAILED DESCRIPTION

[0083] The technical content and detailed description of this application are described below with reference to the accompanying drawings:

[0084] See also Figure 3 , Figure 3 A schematic plan view showing a Kohler illumination system in which an object to be measured is placed on an illuminated surface and in which the Kohler illumination system in which the method for adjusting the position of an optimized diffuser of the Kohler illumination system of the present invention is applied is shown.

[0085] like Figure 3 As shown, a Kohler illumination system 100 includes a laser light source 1, a collector 2, a diffuser 3, a condenser 4, a beam splitter 5, an objective 6, a tube lens 7 and an image sensor 8; wherein the diffuser 3 is rotatably disposed between the laser light source 1 and the collector 2, so that a laser beam LB projected by the laser light source 1 is uniformly diffused by the rotation of the diffuser 3, and then irradiated to a device under test (DUT) DUT in sequence through the collector 2, the condenser 4, the beam splitter 5 and the objective 6, and then the image sensor 8 collects an image reflected by the DUT through the tube lens 7, the beam splitter 5 and the objective 6.

[0086] As described above, the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention is mainly used to calibrate the position of the DUT in the Kohler illumination system 100 so that the DUT can be illuminated by the most uniform light field.

[0087] Please continue reading Figure 4 and Figure 5 , Figure 4A schematic diagram showing the initial dynamic image of the object to be measured collected by the image sensor in the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention; Figure 5 A schematic diagram showing the deviation displacement vector generated by using the cross-correlation function to analyze the initial dynamic image of the object to be measured in the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention. Figures 3 to 5 As shown, in order to optimize the position of the diffuser 3, the method for adjusting the optimal diffuser position of the Kohler illumination system of the present invention includes the following steps S110 to S130.

[0088] First, in this embodiment, step S110 is to collect an initial dynamic image SI1 of the object under test DUT when the diffusion sheet 3 is located at an initial position P0 by using the image sensor 8 when the diffusion sheet 3 rotates, and analyze whether a deviation displacement vector dV0 of multiple specks S1 (there are multiple specks in the figure, only one is marked) remains converged within a predetermined range SR for the initial dynamic image SI1 of the object under test; wherein, step S110 is to use a computer host (not shown) electrically connected to the image sensor 8 to perform image analysis on the initial dynamic image SI1 of the object under test by a cross-correlation operation to obtain a cross-correlation operation result image CC1, so as to display the deviation displacement vector dV0. Although in this embodiment, the deviation displacement vector dV0 of the speckle S1 is obtained by cross-correlation operation of the change characteristics of multiple specks S1, in other embodiments, if there is only one speckle S1, cross-correlation operation can also be performed.

[0089] Next, in step S120, if the deviation displacement vector dV0 of the speckle S1 in step S110 remains within the predetermined range SR, the position of the diffuser 3 at the initial position P0 is defined as an optimized diffuser position with the best light field uniformity, otherwise, step S130 is continued to be executed. In this embodiment, since it is determined in step S120 that the deviation displacement vector dV0 of the speckle S1 in step S110 does not remain within the predetermined range SR, that is, the deviation displacement vector dV0 of the speckle S1 exceeds the predetermined range SR, step S130 is then executed.

[0090] In step S130, if the deviation displacement vector dV0 of the speckle S1 in step S130 exceeds the predetermined range SR, the diffuser 3 is moved to adjust the position of the diffuser 3 until the deviation displacement vector dV0 of the speckle S1 remains within the predetermined range SR, and the corrected position of the diffuser 3 is defined as the optimized diffuser position with the best light field uniformity.

[0091] As mentioned above, when the initial position P0 of the diffuser 3 is set as Figure 3When the ideal illuminated surface IP (equivalent to the focusing surface of the objective lens 6) is not aligned with the surface of the object under test DUT, the initial dynamic image SI1 of the object under test collected by the image sensor 8 will be as shown in FIG. Figure 4 The illustrated example includes two initial static images SI1a and SI1b ; wherein the two initial static images SI1a and SI1b have a time difference between each other.

[0092] It should be particularly noted that, when the image sensor 8 captures the initial dynamic image SI1 of the object under test by capturing one image per second, the two initial static images SI1a and SI1b can be, for example, adjacent frames separated by one second, that is, the initial static image SI1b is captured one second after the initial static image SI1a is captured; but not limited to this, the two initial static images SI1a and SI1b can also be interval frames separated by two seconds, that is, after the initial static image SI1a is captured, the next frame of the initial static image SI1a is skipped and the next frame is taken as the initial static image SI1b.

[0093] In addition, in actual use, the peak value of the speckle S1 (similar to the weighted average position of all speckles S1 in the picture) and the peak value of the speckle S1a are calculated respectively by the above-mentioned computer host, and then the change of the peak value is calculated by cross-correlation to obtain the deviation displacement vector dV0. For example, the initial static images SI1a and SI1b of the present invention may be, for example, 100×100 pixels, and when the speckle S1 is about 4 to 6 pixels, the predetermined range SR may be, for example, a tolerance range divided by taking 6 to 9 pixels as the allowable deviation amount and taking the peak value of the speckle S1 as the origin and the allowable deviation amount as the positive and negative value boundary, and whether the deviation displacement vector dV0 remains converged in the predetermined range SR is mainly determined based on whether the peak value of the speckle S1a is located in the predetermined range SR1.

[0094] From the two initial static images SI1a and SI1b, it can be seen that the position of the speckle S1 in the initial static image SI1a is significantly different from the position of the speckle S1a in the initial static image SI1b, and the displacement deviation vector dV0 between the peak of the speckle S1a and the peak of the speckle S1 has exceeded the predetermined range SR set with the peak of the speckle S1 as the center. Therefore, corresponding to the above step S120, it can be seen that the diffuser 3 is Figure 3 The set initial position P0 is not the position with the best light field uniformity, so it is necessary to proceed to step S130. Specifically, in addition to taking the peak of the speckle S1 as the center, the predetermined range SR can be set to, for example, 100% to 200% of the original range of the speckle S1, and the smaller the range setting, the more accurate it is.

[0095] In this embodiment, the above-mentioned step S130 may further include the following detailed steps S131 to S134 .

[0096] Please continue reading Figures 6 to 8 , Figure 6 A schematic plan view showing the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention, in which the diffuser is moved along a first direction to a first calibration position when the deviation displacement vector of the speckle of the initial dynamic image of the object under test does not remain converged within a predetermined range; Figure 7 A schematic diagram showing a first calibrated dynamic image captured by an image sensor in the method for calibrating the optimal diffuser position of a Kohler illumination system of the present invention; Figure 8 A schematic diagram showing the deviation displacement vector generated by analyzing the first calibrated dynamic image using a cross-correlation function in the method for optimizing the diffuser position adjustment of the Kohler illumination system of the present invention.

[0097] like Figures 3 to 8 As shown, after determining in step S120 that the initial position P0 of the diffuser 3 is not the position with the best light field uniformity, step S131 is to move the diffuser 3 along a first direction D1 parallel to an optical axis OA of the laser beam LB to a position as shown in FIG. Figure 6 The first calibration position P1 is shown, and the image sensor 8 is used to collect a first calibration dynamic image SI2 of the object under test DUT located at the first calibration position P1, and the deviation displacement vector dV1 of the speckle S2 is analyzed for the first calibration dynamic image SI2 to see whether it remains within the predetermined range SR. In step S131, the computer host is also used to perform image analysis on the first calibration dynamic image SI2 through cross-correlation operation to obtain a cross-correlation operation result image CC2 showing the deviation displacement vector dV1.

[0098] As mentioned above, the first corrected dynamic image SI2 includes two first corrected static images SI2a and SI2b, and the two first corrected static images SI2a and SI2b are collected in a similar manner to the two initial static images SI1a and SI1b, and also have a time difference, and the difference mainly depends on the different positions of the diffuser 3; wherein, after the first corrected static images SI2a and SI2b are analyzed by the cross-correlation function, a displacement deviation vector dV1 between the peak value of the speckle S2 and the peak value of the speckle S2a can be obtained, and the displacement deviation vector dV1 still exceeds the predetermined range SR and does not converge within the predetermined range SR, thus it can be known that when the diffuser 3 is moved along the first direction D1 to the first correction position P1, the overall light field uniformity generated is not optimal, and since the direction of the displacement deviation vector dV1 is opposite to the direction of the displacement deviation vector dV0, it can be known that the diffuser 3 should then be moved along a second direction D2 opposite to the first direction D1, so that the diffuser 3 may be close to the position with the best light field uniformity.

[0099] Next, in step S132, when the deviation displacement vector dV1 of the speckle S2 in step S131 remains within the predetermined range SR, the corrected position of the diffuser 3 when it is located at the first correction position P1 is defined as the optimized diffuser position with the best light field uniformity; however, in this embodiment, since the deviation displacement vector dV1 of the speckle S2 does not converge within the predetermined range SR, the following step S133 needs to be continued.

[0100] Please continue reading Figures 9 to 11 , Fig. 9 A schematic plan view showing the method for adjusting the position of the diffuser of the Kohler illumination system of the present invention, in which the diffuser is moved along the second direction to a second calibration position when the deviation displacement vector of the speckle of the first calibration dynamic image is analyzed and does not remain converged within a predetermined range; Fig.10 A schematic diagram showing a second calibration dynamic image captured by an image sensor in the method for adjusting the position of an optimized diffuser of a Kohler illumination system of the present invention; Fig.11 A schematic diagram showing the deviation displacement vector generated by analyzing the second calibrated dynamic image using a cross-correlation function in the method for optimizing the diffuser position adjustment of the Kohler illumination system of the present invention.

[0101] like Figures 3 to 11 As shown, step S133 is to move the diffuser 3 to a second calibration position P2 along a second direction D2 opposite to the first direction D1 when the deviation displacement vector dV1 of the speckle S2 in step S131 exceeds the predetermined range SR, so as to collect a second calibration dynamic image SI3 of the diffuser 3 at the second calibration position P2 by using the image sensor 8, and analyze whether the deviation displacement vector dV2 of the speckle S3 remains converged within the predetermined range SR for the second calibration dynamic image SI3, if the deviation displacement vector dV2 of the speckle S3 remains converged within the predetermined range SR, then the calibrated position of the diffuser 3 at the second calibration position P2 is defined as the optimized diffuser position with the best light field uniformity, otherwise, continue to execute step S134. Wherein, step S133 is also to use the computer host to perform image analysis on the second calibration dynamic image SI3 through cross-correlation operation to obtain a cross-correlation operation result image CC3 showing the deviation displacement vector dV2.

[0102] As mentioned above, the second corrected dynamic image SI3 includes two second corrected static images SI3a and SI3b, and the two second corrected static images SI3a and SI3b are collected in a similar manner to the two initial static images SI1a and SI1b, and also have a time difference, and the difference mainly depends on the different positions of the diffuser 3; wherein, after the second corrected static images SI3a and SI3b are analyzed by the cross-correlation function, the displacement deviation vector dV2 between the peak value of the speckle S3 and the peak value of the speckle S3a can be obtained, and since the displacement deviation vector dV2 remains converged within the predetermined range SR, the corrected position of the diffuser 3 (the second corrected position P2) can be defined as the optimized diffuser position with the best light field uniformity.

[0103] Please continue reading Fig.12 , Fig.12 A schematic diagram showing the deviation displacement vector corresponding to the diffusion plate moving from the initial position along the first direction to the first calibration position, and from the first calibration position along the second direction to the second calibration position in the method for adjusting the position of the optimal diffusion plate of the Kohler illumination system of the present invention. Figures 3 to 12 As shown, since the deviation displacement vector dV0 obtained by calculating the cross-correlation function exceeds the predetermined range SR when the diffuser 3 is at the initial position P0, according to the above-mentioned step S130, the diffuser 3 needs to be moved along the first direction D1. At this time, the first direction D1 refers to the direction in which the diffuser 3 moves for the first time in step S130, and the first direction D1 can be close to the light collecting mirror 2 or away from the light collecting mirror 2. In the present embodiment, the first direction D1 is the direction close to the light collecting mirror 2.

[0104] As mentioned above, in the present embodiment, the deviation displacement vector dV0 exceeds the predetermined range SR mainly means that the vector size of the deviation displacement vector dV0 exceeds the allowable offset from the center to the boundary of the predetermined range SR. In more detail, the optimal ideal position of the diffuser 3 allows the light spot S1 to almost disappear in place, and the deviation displacement vector dV0 is determined by the offset and direction between the speckle S1 and the speckle S1a. Therefore, when calculating the deviation displacement vector dV1 and the predetermined range SR, the speckle S1 (or the peak value of the speckle S1) is used as the origin, and the predetermined range SR is the positive and negative error range set with the origin as the center. Thus, when the deviation displacement vector dV0 obtained by the diffuser 3 at the initial position is a positive vector compared to the above-mentioned origin, the deviation displacement vector dV1 centered at the origin and opposite to the deviation displacement vector dV0 is a negative vector.

[0105] Thus, in the above step S131, because the vector magnitude of the displacement deviation vector dV1 (equivalent to the absolute value of the vector when only the magnitude is considered without considering the direction) generated by the diffuser 3 at the first correction position P1 exceeds the predetermined range SR (i.e., a simple numerical magnitude comparison based on the above-mentioned origin), and the vector direction of the displacement deviation vector dV1 generated by the first correction position P1 is opposite to the vector direction of the deviation displacement vector dV0 measured when the diffuser 3 is at the previous position (initial position P0), it means that the diffuser 3 is in the opposite direction and further away from the predetermined range SR. Therefore, the diffuser 3 needs to be moved along the second direction D2 opposite to the first direction D1 in order to make the diffuser 3 approach the ideal position.

[0106] Please continue reading Fig.13 and Fig.14 As shown in the figure, in step S133 of another embodiment, when the diffuser 3 of step S131 moves from the initial position P0 along the first direction D1 to a first correction position P1a, and the deviation displacement vector dV1a obtained by calculating the cross-correlation function still exceeds the predetermined range SR, if the direction of the deviation displacement vector dV1a is the same as the direction of the deviation displacement vector dV0 measured when the diffuser 3 is located at the previous position (initial position P0), but the vector magnitude of the deviation displacement vector dV1a is smaller than the vector magnitude of the deviation displacement vector dV0 of the diffuser 3 at the previous position (initial position P0), it means that the diffuser 3 moves along the first direction D1 to the first correction position P1a which is closer to the predetermined range SR, and therefore the diffuser 3 needs to be further moved along the first direction D1.

[0107] As mentioned above, when the diffuser 3 moves from the first correction position P1a to the second correction position P2a along the first direction D1, and the deviation displacement vector dV2a obtained by calculating the cross-correlation function converges within the predetermined range SR, the corrected position (second correction position P2a) of the diffuser 3 can be defined as the optimized diffuser position with the best light field uniformity.

[0108] Please continue reading Fig.15 and Fig.16As shown in the figure, in step S133 of another embodiment, when the diffuser 3 moves from the initial position P0 along a first direction D1b to a first correction position P1b, when the deviation displacement vector dV1b obtained by calculating the cross-correlation function still exceeds the predetermined range SR, if the direction of the deviation displacement vector dV1b is the same as the direction of the deviation displacement vector dV0 measured when the diffuser 3 is located at the previous position (initial position P0), but the vector magnitude of the deviation displacement vector dV1a is greater than the vector magnitude of the deviation displacement vector dV0 of the diffuser 3 at the previous position (initial position P0), it means that the diffuser 3 moves along the first direction D1 to the first correction position P1b, not only does not move to the predetermined range SR compared to the initial position P0, but is further away from the predetermined range SR, so the diffuser 3 needs to be moved along the second direction D2b opposite to the first direction D1b.

[0109] In summary, the method for adjusting the position of the optimal diffuser of the Kohler illumination system of the present invention mainly uses the image sensor to collect the initial dynamic image of the object to be measured when the diffuser rotates, so as to analyze whether the deviation displacement vector of the spot remains converged within a predetermined range, and then judge whether the diffuser is in the optimal position. If not, the position is adjusted until the speckle position of the collected image is a pattern of in-situ expansion and contraction, which means that the corrected position of the diffuser is the optimal position with the best light field uniformity. Compared with the prior art that only uses the rotation of the diffuser to eliminate speckles but cannot set the object to be measured at a position where it can be illuminated most evenly, the present invention can indeed set the diffuser position at an optimal position that can optimize the uniformity of the illumination light field on the object to be measured, thereby effectively improving the quality of the collected image.

[0110] Through the detailed description of the preferred embodiments above, it is hoped that the features and spirit of the present invention can be more clearly described, and the scope of the present invention is not limited by the preferred embodiments disclosed above. On the contrary, its purpose is to cover various changes and arrangements with equivalents within the scope of the patent scope that the present invention intends to apply for.

Claims

1. A method for calibrating the position of an optimized diffuser of a Kohler illumination system, for calibrating a Kohler illumination system, characterized in that: The Kohler illumination system includes a laser light source, a light collecting lens, a diffuser, a focusing lens, a beam splitter, an objective lens, a tube lens, and an image sensor. The diffuser is rotatably disposed between the laser light source and the light collecting lens, so that a laser beam projected by the laser light source is uniformly diffused by the rotation of the diffuser, and then irradiated to an object to be measured in sequence through the light collecting lens, the focusing lens, the beam splitter, and the objective lens, so that the image sensor collects an image reflected by the object to be measured through the tube lens, the beam splitter, and the objective lens. The adjustment method of the Kohler illumination system includes the following steps: (A) when the diffuser rotates, using the image sensor to capture an initial dynamic image of the object to be measured when the diffuser is located at an initial position, and analyzing, with respect to the initial dynamic image of the object to be measured, whether a deviation displacement vector of at least one speckle remains within a predetermined range; (B) if the deviation displacement vector of the at least one speckle in step (A) remains within the predetermined range, the initial position of the diffuser is defined as an optimized position with the best light field uniformity; otherwise, step (C) is continued; and (C) If the deviation displacement vector of the at least one speckle in step (A) exceeds the predetermined range, the position of the diffuser is adjusted until the deviation displacement vector of the at least one speckle remains within the predetermined range, and a corrected position of the diffuser after adjustment is defined as the optimized position with the best light field uniformity.

2. The method for optimizing the object distance adjustment of the Kohler illumination system according to claim 1, wherein: The laser light source has an optical axis, and step (C) further comprises the following steps: (C1) moving the diffusion sheet along a first direction parallel to the optical axis to a first calibration position, so as to use the image sensor to capture a first calibrated dynamic image of the object under test, and analyzing the first calibrated dynamic image to determine whether the deviation displacement vector of the at least one speckle remains within the predetermined range; (C2) if the deviation displacement vector of the at least one speckle in step (C1) remains within the predetermined range, the corrected position of the diffuser when it is at the first correction position is defined as the optimized position with the best light field uniformity; otherwise, continue to execute step (C3); (C3) if the deviation displacement vector of the at least one speckle in step (C1) exceeds the predetermined range, move the diffuser along the first direction or a second direction opposite to the first direction to a second calibration position, so as to use the image sensor to capture a second calibration dynamic image of the object under test, and analyze the second calibration dynamic image to see whether the deviation displacement vector of the at least one speckle remains within the predetermined range; if the deviation displacement vector of the at least one speckle remains within the predetermined range, define the calibrated position of the diffuser at the second calibration position as the optimized position with the best light field uniformity; otherwise, continue to execute step (C4); and (C4) Repeating the steps (C1) to (C3) until the deviation displacement vector of the at least one speckle remains within the predetermined range, the corrected position of the diffuser being defined as the optimized position with the best light field uniformity.

3. The method for adjusting the optimal diffuser position of a Kohler illumination system according to claim 2, wherein: In the step (C3), when the vector magnitude of the deviation displacement vector of the at least one speckle in the step (C1) exceeds the predetermined range, and the vector direction of the deviation displacement vector of the at least one speckle in the step (C1) is opposite to the vector direction of the deviation displacement vector measured when the diffuser is located at a previous position, the diffuser is moved along the second direction opposite to the first direction to the second correction position.

4. The method for adjusting the optimal diffuser position of a Kohler illumination system according to claim 2, wherein: In the step (C3), when the vector magnitude of the deviation displacement vector of the at least one speckle in the step (C1) exceeds the predetermined range, if the direction of the deviation displacement vector of the at least one speckle in the step (C1) is the same as the direction of the deviation displacement vector measured when the diffuser is located at a previous position, but the magnitude of the deviation displacement vector of the at least one speckle in the step (C1) is smaller than the vector magnitude of the deviation displacement vector measured when the diffuser is located at the previous position, then the diffuser is moved along the first direction to the second correction position.

5. The method for adjusting the optimal diffuser position of a Kohler illumination system according to claim 2, wherein: In step (C3), when the vector magnitude of the deviation displacement vector of the at least one speckle in step (C1) exceeds the predetermined range, if the direction of the deviation displacement vector of the at least one speckle in step (C1) is the same as the direction of the deviation displacement vector measured when the diffuser is located at a previous position, but the magnitude of the deviation displacement vector of the at least one speckle in step (C1) is greater than the vector magnitude of the deviation displacement vector measured when the diffuser is located at the previous position, then the diffuser is moved along the second direction opposite to the first direction to the second correction position.

6. The method for adjusting the optimal diffuser position of a Kohler illumination system according to claim 2, wherein: The diffusion sheet moves along the first direction to approach the light collecting lens, and the diffusion sheet moves along the second direction to move away from the light collecting lens.

7. The method for adjusting the optimal diffuser position of a Kohler illumination system according to claim 2, wherein: The diffusion sheet moves along the first direction to be away from the light collecting lens, and the diffusion sheet moves along the second direction to be close to the light collecting lens.

8. The method for adjusting the optimal diffuser position of a Kohler illumination system as claimed in claim 2, wherein: In step (A), a computer host electrically connected to the image sensor is used to perform image analysis on the initial dynamic image of the object being measured. In step (C1), the computer host is used to perform image analysis on the first dynamic image. In step (C3), the computer host is used to perform image analysis on the second dynamic image.

9. The method for adjusting the optimal diffuser position of a Kohler illumination system according to claim 2, wherein: The first corrected dynamic image includes two first corrected static images, and the two first corrected static images have a time difference between each other. The second corrected dynamic image includes two second corrected static images, and the two second corrected static images have a time difference between each other.

10. The method for adjusting the optimal diffuser position of a Kohler illumination system according to claim 1, wherein: The initial dynamic image of the object to be measured includes two initial static images, and there is a time difference between the two initial static images.

Images