Optimized diffusion sheet position adjustment method for kohler illumination system

Abstract

The present application provides a method for calibrating the optimal diffuser position of a Kohler illumination system. First, an initial measured object dynamic image is collected by an image sensor when a diffuser rotates to an initial position, and whether the deviation displacement vector of at least one speckle keeps converging in a predetermined range is analyzed according to the initial measured object dynamic image. Then, if the deviation displacement vector of the speckle keeps converging in the predetermined range, the initial position of the diffuser is defined as the optimal diffuser position with the best light field uniformity. Otherwise, the position of the diffuser is adjusted until the deviation displacement vector of the speckle keeps converging in the predetermined range, and the corrected position of the diffuser is defined as the optimal position with the best light field uniformity.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for calibrating an illumination system, and more particularly, to a method for calibrating an optimal object distance of a Köhler illumination system. BACKGROUND

[0002] In the prior art of optical measurement, in order to effectively collect the image of a sample, a suitable light source must be used for illumination, and the illumination method is divided into two categories: critical illumination and Köhler illumination. The critical illumination causes the characteristics of the light source to be displayed together with the image of the sample, which is superimposed together to cause interference. Therefore, in the prior art of optics, the technology of Köhler illumination is mainly used to provide uniform illumination.

[0003] Referring to Figure 1 , Figure 1 A plan view of a prior art Köhler illumination system is shown. As Figure 1 shown, a Köhler illumination system PA100 includes an illumination light source PA1, a condenser 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. The diffuser PA3 is rotatably disposed between the illumination light source PA1 and the condenser lens PA2, so that a laser beam PALB emitted by the illumination light source PA1 is uniformly diffused by the rotation of the diffuser PA3, and then sequentially irradiates the measured object on an illuminated surface PAIP through the condenser lens PA2, the focusing lens PA4, the beam splitter PA5, and the objective lens PA6, so that the image sensor PA8 collects the image reflected by the measured object on the illuminated surface PAIP through the tube lens PA7, the beam splitter PA5, and the objective lens PA6.

[0004] Referring to Figure 2 , Figure 2 When a laser is used as the illumination light source in the prior art Köhler illumination system, a random speckle image presented by the illuminated surface is collected when the diffuser PA3 is stationary. As Figure 1 and Figure 2 shown, in some optical applications, in order to achieve sufficient power density (i.e., generally referred to 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, the image sensor PA8 collects a speckle image SI containing a plurality of speckle noises on the illuminated surface PAIP when the diffuser PA3 is stationary, and the existence of the speckles causes severe uneven illumination, so that the image captured by the image sensor PA8 is almost indistinguishable.

[0005] As mentioned above, in order to reduce the negative effects of speckle, the prior art generally sets a diffusion sheet PA3 between the light source PA1 and the collector lens PA2, and uses the rotation of the diffusion sheet PA3 to form an equivalent light source by rotating the diffusion sheet PA3, and then focuses the light through the collector lens PA2 and the focusing lens PA4 on the back focal plane of the objective lens PA6, and then projects the light through the objective lens PA6 onto the measured object (not shown in the figure) located on the illuminated surface PAIP; thereby, from the equivalent light source to the illuminated surface PAIP is a typical Kohler illumination architecture. Then the light is imaged on the image sensor PA8 through the objective lens PA6, the beam splitter PA5 and the tube lens PA7 in reverse, thereby the observed image is effectively homogenized in the exposure time due to the rotation of the diffusion sheet PA3, such technology is generally referred to as despeckle.

[0006] As described above, the rotating diffusion sheet PA3 is used to achieve the effect of despeckle (homogeneous illumination on a small scale), and the Kohler illumination system PA100 is used to achieve macroscopic homogeneous illumination. In order to achieve macroscopic homogeneous illumination, the position of the diffusion sheet PA3 (i.e. the equivalent light source) must be properly adjusted so that the diffusion sheet PA3 and the illuminated surface PAIP satisfy the optical Fourier plane relationship.

[0007] Generally, those skilled in the art can preliminarily set the diffusion sheet PA3, the image sensor PA8 and the relative positions of the above-mentioned objects by optical components according to the nominal specifications of the collector lens PA2, the focusing lens PA4, the objective lens PA6 and the tube lens PA7. However, in practice, due to various machining and assembly errors, the position of the diffusion sheet PA3 usually fails to form the best macroscopic homogeneous illumination on the illuminated surface PAIP (equivalent to the conjugate surface of the image sensor PA8), at this time, a standard measured object needs to be placed on the illuminated surface PAIP, and the illumination distribution on the standard measured object is observed through the image sensor PA8, and then the position of the diffusion sheet PA3 is adjusted to make the illumination distribution on the standard measured object present the best macroscopic homogeneous illumination. However, since the laser beam passing through the diffusion sheet PA3 will cause the image observed by the image sensor PA8 to have strong random speckle, it is difficult to judge whether the standard measured object presents macroscopic homogeneous illumination, therefore, an effective judgment and adjustment method is needed to judge and adjust the best setting position of the diffusion sheet PA3. SUMMARY

[0008] In view of the prior art, although the existing Kohler illumination system can provide high illumination brightness by using a laser light source, in order to eliminate speckle generated when using the laser light source, a diffuser is usually arranged and the light field is homogenized by rotating the diffuser. However, in actual use, the arrangement position of the diffuser cannot always be aligned with the object to be measured, so that the object to be measured cannot be uniformly illuminated. Therefore, the main purpose of the present application is to provide a method for optimizing the arrangement position of a diffuser of a Kohler illumination system, which can effectively find the optimal arrangement position of the diffuser at which the object to be measured can be uniformly illuminated.

[0009] In order to solve the problems of the prior art, the necessary technical means adopted by the present application is to provide a method for optimizing the arrangement position of a diffuser of a Kohler illumination system, which is used to correct a Kohler illumination system. The Kohler illumination system includes a laser light source, a collector, a diffuser, a condenser, a beam splitter, an objective lens, a tube lens and an image sensor. The diffuser is rotatably arranged 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 sequentially irradiated to a device under test (DUT) through the collector, the condenser, the beam splitter and the objective lens, so that the image sensor collects the reflected image of the DUT through the tube lens, the beam splitter and the objective lens. The correction method of the Kohler illumination system includes the following steps (A) to (C).

[0010] Firstly, step (A) is to collect an initial dynamic image of a device under test at an initial position of the diffuser by using the image sensor when the diffuser is rotating, and to analyze whether a deviation displacement vector of at least one speckle keeps converging in a predetermined range.

[0011] Then, step (B) is to define the initial position of the diffuser as an optimal diffuser position with the best light field uniformity if the deviation displacement vector of the at least one speckle keeps converging in the predetermined range in step (A), otherwise, step (C) is continued.

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

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

[0014] Step (C1) is to move the diffuser along a first direction parallel to the optical axis to a first correction position to acquire a first correction dynamic image of the measured object by the image sensor, and analyze whether the deviation displacement vector of the at least one speckle keeps converging in the predetermined range for the first correction dynamic image.

[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) keeps converging in the predetermined range, otherwise, step (C3) is continued.

[0016] Step (C3) is to move the diffuser along the first direction or a second direction opposite to the first direction to a second correction position to acquire a second correction dynamic image of the measured object by the image sensor if the deviation displacement vector of the at least one speckle in step (C1) exceeds the predetermined range, and analyze whether the deviation displacement vector of the at least one speckle keeps converging in the predetermined range for the second correction dynamic image, define the corrected position of the diffuser at the second correction position as the optimized diffuser position with the best light field uniformity if the deviation displacement vector of the at least one speckle keeps converging in the predetermined range, otherwise, step (C4) is continued.

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

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

[0019] In addition, 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 diffusion sheet was in the previous position, but the vector 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 diffusion sheet was in the previous position, the diffusion sheet is moved in the second direction opposite to the first direction to the second correction position.

[0020] In contrast, 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 diffusion sheet was in the previous position, but the vector magnitude of the deviation displacement vector of the at least one speckle in the step (C1) is larger than the vector magnitude of the deviation displacement vector measured when the diffusion sheet was in the previous position, the diffusion sheet is moved in the second direction opposite to the first direction to the second correction position.

[0021] In one embodiment, the diffusion sheet is moved in the first direction to approach the light collector, and the diffusion sheet is moved in the second direction to move away from the light collector; in another embodiment, the diffusion sheet is moved in the first direction to move away from the light collector, and the diffusion sheet is moved in the second direction to approach the light collector.

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

[0023] In addition, the first correction dynamic image includes two first correction static images having a time difference therebetween, and the second correction dynamic image includes two second correction static images having a time difference therebetween.

[0024] In an auxiliary technical means derived from the above necessary technical means, the initial object dynamic image includes two initial static images having a time difference therebetween.

[0025] As mentioned above, the present application mainly uses the image sensor to collect the initial measured object dynamic image of the measured object when the diffuser rotates, analyzes whether the deviation displacement vector of the speckle keeps converging in the predetermined range, and then judges whether the diffuser is in the optimized position. If not, the position is continuously adjusted until the speckle position of the collected image is the mode of original place, which indicates that the corrected position of the diffuser is the optimized position with the best light field uniformity.

[0026] The specific embodiments adopted by the present application will be further described by the following examples and drawings. BRIEF DESCRIPTION OF DRAWINGS

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

[0028] Figure 2 A plan view showing a prior art Kohler illumination system using a laser as an illumination light source to collect the random speckle image presented by the illuminated surface;

[0029] Figure 3 A plan view showing a Kohler illumination system to which the optimized diffuser position adjustment method of the present application is applied, with a measured object placed on the illuminated surface;

[0030] Figure 4 A plan view showing the initial measured object dynamic image collected by the image sensor in the optimized diffuser position adjustment method of the Kohler illumination system of the present application;

[0031] Figure 5 A plan view showing the deviation displacement vector generated by analyzing the initial measured object dynamic image in the optimized diffuser position adjustment method of the Kohler illumination system of the present application;

[0032] Figure 6 A plan view showing the measured object moved to the first corrected position in the first direction when the deviation displacement vector of the speckle of the initial measured object dynamic image is not kept converging in the predetermined range in the optimized diffuser position adjustment method of the Kohler illumination system of the present application;

[0033] Figure 7 A plan view showing the first corrected dynamic image collected by the image sensor in the optimized diffuser position adjustment method of the Kohler illumination system of the present application;

[0034] Figure 8 A plan view showing the deviation displacement vector generated by analyzing the first corrected dynamic image in the optimized diffuser position adjustment method of the Kohler illumination system of the present application;

[0035] Figure 9A plan view showing the movement of the diffuser sheet to a second correction position in a second direction when the deviation displacement vector generated by analyzing the speckle of the first correction dynamic image does not remain convergent in a predetermined range in the method for optimizing the position of the diffuser sheet of the Kohler illumination system according to the present application;

[0036] Figure 10 A schematic diagram of the second correction dynamic image captured by the image sensor in the method for optimizing the position of the diffuser sheet of the Kohler illumination system according to the present application;

[0037] Figure 11 A schematic diagram of the deviation displacement vector generated by analyzing the second correction dynamic image using the cross-correlation function in the method for optimizing the position of the diffuser sheet of the Kohler illumination system according to the present application;

[0038] Figure 12 A plan view showing the deviation displacement vector corresponding to the movement of the diffuser sheet from an initial position to a first correction position in a first direction and from the first correction position to a second correction position in a second direction in the method for optimizing the position of the diffuser sheet of the Kohler illumination system according to the present application;

[0039] Figure 13 A plan view showing the movement of the diffuser sheet to a second correction position in a first direction after the movement of the diffuser sheet to a first correction position in the first direction in the method for optimizing the position of the diffuser sheet of the Kohler illumination system according to the present application;

[0040] Figure 14 A plan view showing Figure 13 the movement of the diffuser sheet from an initial position to a first correction position in a first direction according to the deviation displacement vector corresponding to the movement to the first correction position and a second position in the method for optimizing the position of the diffuser sheet of the Kohler illumination system according to the present application;

[0041] Figure 15 A plan view showing the movement of the diffuser sheet to a second correction position in a second direction opposite to the first direction after the movement of the diffuser sheet to a first correction position in a first direction away from or close to the condenser in the method for optimizing the position of the diffuser sheet of the Kohler illumination system according to the present application; and

[0042] Figure 16 A plan view showing Figure 15 the deviation displacement vector corresponding to the movement of the diffuser sheet to a first correction position in a first direction away from or close to the condenser in the method for optimizing the position of the diffuser sheet of the Kohler illumination system according to the present application.

[0043] Wherein, the reference signs are:

[0044] PA100: Kohler illumination system

[0045] PA1: illumination light source

[0046] PA2: condenser

[0047] PA3: Diffuser

[0048] PA4: Focusing mirror

[0049] PA5: Beam splitter

[0050] PA6: Objective lens

[0051] PA7: Tube lens

[0052] PA8: Image sensor

[0053] PALB: Laser beam

[0054] PAIP: Illuminated plane

[0055] SI: Speckle image

[0056] 100: Kohler illumination system

[0057] 1: Laser source

[0058] 2: Collector lens

[0059] 3: Diffuser

[0060] 4: Focusing mirror

[0061] 5: Beam splitter

[0062] 6: Objective lens

[0063] 7: Tube lens

[0064] 8: Image sensor

[0065] DUT: Device under test

[0066] LB: Laser beam

[0067] OA: Optical axis

[0068] SI1: Initial dynamic image of the device under test

[0069] SI1a, SI1b: Initial static images of the device under test

[0070] SI2: First corrected dynamic image

[0071] SI2a, SI2b: First corrected static images

[0072] SI3: Second corrected dynamic image

[0073] SI3a, SI3b: Second corrected static images

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

[0075] SR: Predetermined range

[0076] dV0, dV1, dV1a, dV1b, dV2, dV2a: bias displacement vectors

[0077] D1, D1b: first direction

[0078] D2, D2b: second direction

[0079] P0: initial position

[0080] P1, P1a, P1b, P1c: first correction position

[0081] P2, P2a: second correction position

[0082] CC1, CC2, CC3: cross-correlation operation result images DETAILED DESCRIPTION

[0083] The technical content and detailed description of the present application are described as follows in conjunction with the drawings:

[0084] Please refer to Figure 3 , Figure 3 A planar view showing a measured object placed on an illuminated surface of a Kohler illumination system to which the method for optimizing the position of a diffuser of the Kohler illumination system is applied.

[0085] As shown in Figure 3 , 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. 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 sequentially irradiated to a device under test (DUT) DUT through the collector 2, the condenser 4, the beam splitter 5, and the objective 6, thereby allowing the image sensor 8 to collect 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 optimizing the position of the diffuser of the Kohler illumination system is mainly used to correct 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 to refer to Figure 4 and Figure 5 , Figure 4The method for optimizing the position of the diffusion plate of the Kohler illumination system of the present application uses the initial dynamic image of the measured object collected by the image sensor to show the position adjustment of the diffusion plate. Figure 5 The method for optimizing the position of the diffusion plate of the Kohler illumination system of the present application uses the deviation displacement vector generated by the cross-correlation function analysis of the initial dynamic image of the measured object to show the position adjustment of the diffusion plate. Figures 3 to 5 As shown in the figure, in order to optimize the position of the diffusion plate 3, the method for optimizing the position of the diffusion plate of the Kohler illumination system of the present application includes the following steps S110 to S130.

[0088] First, in the present embodiment, step S110 is to collect an initial dynamic image SIl of the measured object DUT when the diffusion plate 3 is at an initial position P0 by using the image sensor 8, and to analyze whether the deviation displacement vector dV0 of a plurality of speckles S1 (there are a plurality of speckles in the figure, only one is marked) keeps converging in a predetermined range SR for the initial dynamic image SIl; wherein step S110 uses a computer host (not shown in the figure) electrically connected to the image sensor 8 to perform image analysis on the initial dynamic image SIl by using a cross-correlation operation to obtain a cross-correlation operation result image CC1, so as to show the deviation displacement vector dV0. Although in the present embodiment, the deviation displacement vector dV0 of the speckles S1 is obtained by cross-correlation operation of the variation characteristics of a plurality of speckles S1, in other embodiments, cross-correlation operation can also be performed if there is only one speckle S1.

[0089] Then, step S120 is to define the position of the diffusion plate 3 at the initial position P0 as the optimized diffusion plate position with the best light field uniformity if the deviation displacement vector dV0 of the speckles S1 in step S110 keeps converging in the predetermined range SR, otherwise, step S130 is continued. Since the deviation displacement vector dV0 of the speckles S1 in step S110 does not keep converging in the predetermined range SR, i.e. the deviation displacement vector dV0 of the speckles S1 exceeds the predetermined range SR, step S130 is continued.

[0090] Step S130 is to move the diffusion plate 3 to adjust the position of the diffusion plate 3 until the deviation displacement vector dV0 of the speckles S1 keeps converging in the predetermined range SR, and then define the corrected position of the diffusion plate 3 as the optimized diffusion plate position with the best light field uniformity.

[0091] As mentioned above, when the initial position P0 of the diffusion plate 3 is as shown in the figure, the deviation displacement vector dV0 of the speckles S1 exceeds the predetermined range SR, so step S130 is continued. Figure 3The initial dynamic image SI1 captured by the image sensor 8 when the ideal illuminated plane IP (equivalent to the focal plane of the objective lens 6) is not aligned with the surface of the DUT will be as shown in Fig. 1B. Figure 4 The initial dynamic image SI1 includes two initial static images SI1a and SI1b, and the two initial static images SI1a and SI1b have a time difference therebetween.

[0092] It is particularly noted that when the image sensor 8 captures the initial dynamic image SI1 by capturing one image per second, the two initial static images SI1a and SI1b may, for example, be adjacent frames separated by one second, i.e., the initial static image SI1b is captured one second after the initial static image SI1a is captured, but are not limited thereto, and the two initial static images SI1a and SI1b may, for example, be interval frames separated by two seconds, i.e., the initial static image SI1b is captured two seconds after the initial static image SI1a is captured.

[0093] In addition, in actual use, the computer host calculates the peak value of the speckle S1 (similar to the weighted average position of all speckles S1 in the frame) and the peak value of the speckle S1a, and then calculates the peak value variation by cross-correlation to obtain the deviation displacement vector dV0. For example, the initial static images SI1a and SI1b of the present application may, for example, be 100x100 pixels, and when the speckle S1 is about 4-6 pixels, the predetermined range SR may, for example, be a tolerance range divided by taking 6-9 pixels as the allowable deviation amount, with 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 convergent in the predetermined range SR is mainly determined according to whether the peak value of the speckle S1a is within the predetermined range SR1.

[0094] As shown by the two initial static images SI1a and SI1b, the position of the speckle S1 in the initial static image SI1a is obviously different from the position of the speckle S1a in the initial static image SI1b, and the displacement deviation vector dV0 between the peak value of the speckle S1a and the peak value of the speckle S1 has exceeded the predetermined range SR centered on the peak value of the speckle S1, so according to the above step S120, the diffusion sheet 3 is not in the initial position P0 set by the user, and the process proceeds to step S130. Figure 3 The initial position P0 set is not the position of optimal light field uniformity, so the process proceeds to step S130. Specifically, in addition to being centered on the peak value of the speckle S1, the predetermined range SR may, for example, be 100%-200% of the original range of the speckle S1, and the smaller the range, the more accurate the setting.

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

[0096] Please continue reading. Figures 6 to 8 , Figure 6 A planar schematic diagram showing the optimal diffuser position adjustment method of the Kohler lighting system of the present invention, which moves the diffuser to a first correction position along a first direction when the deviation displacement vector of the speckle in the initial dynamic image of the test object does not remain converged within a predetermined range. Figure 7 This diagram illustrates the optimal diffuser position adjustment method of the Kohler lighting system of the present invention, using a first corrected dynamic image acquired by an image sensor. Figure 8 This invention illustrates the optimal diffuser position adjustment method for the Kohler lighting system, which utilizes cross-correlation functions to analyze the deviation displacement vector generated by the first corrected dynamic image.

[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 optical field uniformity, step S131 moves 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 the figure. Figure 6 The first calibration position P1 is shown. An image sensor 8 is used to acquire a first calibration dynamic image SI2 of the object under test (DUT) at the first calibration position P1. The image SI2 is then analyzed to determine whether the deviation displacement vector dV1 of the speckle S2 remains converged within a predetermined range SR. Step S131 also involves using a computer host to perform cross-correlation analysis on the first calibration dynamic image SI2 to obtain a cross-correlation result image CC2 displaying the deviation displacement vector dV1.

[0098] As mentioned above, the first corrected dynamic image SI2 includes two first corrected static images SI2a and SI2b. The acquisition methods of the two first corrected static images SI2a and SI2b are similar to those of the two initial static images SI1a and SI1b mentioned above, and they also have a time difference. The difference mainly depends on the different positions of the diffuser 3. After analyzing the first corrected static images SI2a and SI2b through the cross-correlation function, the displacement deviation vector dV1 between the peak value of speckle S2 and the peak value of speckle S2a can be obtained. The displacement deviation vector dV1 still exceeds the predetermined range SR and has not converged within the predetermined range SR. Therefore, it can be seen that when the diffuser 3 is moved along the first direction D1 to the first corrected position P1, the overall light field uniformity is not optimal. Since the direction of the displacement deviation vector dV1 is opposite to the direction of the displacement deviation vector dV0, the diffuser 3 should then be moved along a second direction D2, which is opposite to the first direction D1, in order to make the diffuser 3 approach the position with the optimal light field uniformity.

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

[0100] Please continue to refer to Figures 9 to 11 , Figure 9 The planar schematic view showing the diffuser sheet moving to the second correction position in the second direction when the deviation displacement vector of the speckle in the first correction dynamic image does not keep converging in the predetermined range in the method for adjusting the optimized diffuser sheet position of the Kohler illumination system of the present application; Figure 10 The schematic view showing the second correction dynamic image collected by the image sensor in the method for adjusting the optimized diffuser sheet position of the Kohler illumination system of the present application; Figure 11 The schematic view showing the deviation displacement vector generated by analyzing the second correction dynamic image with the cross-correlation function in the method for adjusting the optimized diffuser sheet position of the Kohler illumination system of the present application.

[0101] As Figures 3 to 11 shown, step S133 is to move the diffuser sheet 3 to a second correction position P2 in the 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, to collect a second correction dynamic image SI3 of the diffuser sheet 3 located at the second correction position P2 with the image sensor 8, and analyze whether the deviation displacement vector dV2 of the speckle S3 keeps converging in the predetermined range SR for the second correction dynamic image SI3, and if the deviation displacement vector dV2 of the speckle S3 keeps converging in the predetermined range SR, then define the corrected position of the diffuser sheet 3 when the diffuser sheet 3 is located at the second correction position P2 as the optimized diffuser sheet position with the best light field uniformity, otherwise, continue to perform step S134. In step S133, the cross-correlation operation result image CC3 showing the deviation displacement vector dV2 is obtained by the computer host performing image analysis on the second correction dynamic image SI3 through the cross-correlation operation.

[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 way 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 diffusion sheet 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 converges in the predetermined range SR, the corrected position (second corrected position P2) of the diffusion sheet 3 can be defined as the optimized diffusion sheet position with the best light field uniformity.

[0103] Please continue to refer to Figure 12 , Figures 3 to 12 As shown in the plane diagram of the deviation displacement vector corresponding to the movement of the diffusion sheet from the initial position to the first corrected position along the first direction and from the first corrected position to the second corrected position along the second direction in the method for adjusting the optimized diffusion sheet position of the Kohler illumination system of the present application, as shown in Figure 13 Since the deviation displacement vector dV0 obtained by the operation of the cross-correlation function when the diffusion sheet 3 is at the initial position P0 exceeds the predetermined range SR, according to the above step S130, the diffusion sheet 3 needs to be moved along the first direction D1, and at this time, the first direction D1 refers to the direction of the first movement of the diffusion sheet 3 in step S130, and the first direction D1 can be close to or away from the collector 2, and in this embodiment, the first direction D1 is the direction close to the collector 2.

[0104] As mentioned above, in this embodiment, the deviation displacement vector dV0 exceeding the predetermined range SR mainly refers to the vector size of the deviation displacement vector dV0 exceeding the allowed deviation amount from the center to the boundary of the predetermined range SR, and more specifically, the best ideal position of the diffusion sheet 3 will make the light spot S1 almost disappear in place, and the deviation displacement vector dV0 is determined by the offset amount and direction between the speckle S1 and the speckle S1a, so when calculating the deviation displacement vector dV1 and the predetermined range SR, the speckle S1 (or the peak value of the speckle S1) is taken as the origin, and the predetermined range SR is taken as the center of the origin to set the positive and negative error range, thereby when the deviation displacement vector dV0 obtained by the diffusion sheet 3 at the initial position is a positive vector compared to the above-mentioned origin, the deviation displacement vector dV1 opposite to the deviation displacement vector dV0 with the origin as the center is a negative vector.

[0105] Therefore, in step S131, if the vector size of the displacement deviation vector dV1 generated by the diffuser sheet 3 at the first correction position P1 exceeds the predetermined range SR (i.e., the absolute value of the vector size is greater than the absolute value of the vector size of the displacement deviation vector dV0 measured at the previous position (the initial position P0) of the diffuser sheet 3), and the direction of the displacement deviation vector dV1 generated by the diffuser sheet 3 at the first correction position P1 is opposite to the direction of the displacement deviation vector dV0 measured at the previous position (the initial position P0) of the diffuser sheet 3, it means that the diffuser sheet 3 is further away from the predetermined range SR in the opposite direction. Therefore, the diffuser sheet 3 needs to be moved in the second direction D2 opposite to the first direction D1 so as to approach the ideal position.

[0106] Please continue to refer to Figure 14 and Figure 15 As shown in FIG. 6, in step S133 of another embodiment, when the diffuser sheet 3 is moved from the initial position P0 to a first correction position P1a in the first direction D1 in step S131, and the displacement deviation vector dV1a obtained by the operation of the cross-correlation function still exceeds the predetermined range SR, if the direction of the displacement deviation vector dV1a is the same as the direction of the displacement deviation vector dV0 measured at the previous position (the initial position P0) of the diffuser sheet 3, but the vector size of the displacement deviation vector dV1a is smaller than the vector size of the displacement deviation vector dV0 at the previous position (the initial position P0) of the diffuser sheet 3, it means that the diffuser sheet 3 is closer to the predetermined range SR after being moved to the first correction position P1a in the first direction D1. Therefore, the diffuser sheet 3 needs to be further moved in the first direction D1.

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

[0108] Please continue to refer to Figure 16 and ​As shown in the figure, in step S133 of another embodiment, when the diffuser 3 is moved from the initial position P0 to a first correction position P1b in a first direction D1b, if the deviation displacement vector dV1b obtained by the operation of the cross-correlation function still exceeds the predetermined range SR, and 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 was at the previous position (the initial position P0), but the vector size of the deviation displacement vector dV1a is greater than the vector size of the deviation displacement vector dV0 of the diffuser 3 at the previous position (the initial position P0), that is, the diffuser 3 is moved to the first correction position P1b in the first direction D1b, which is further away from the predetermined range SR rather than moving to the predetermined range SR compared with the initial position P0, so the diffuser 3 needs to be moved in a second direction D2b opposite to the first direction D1b.

[0109] In summary, the method for optimizing the position of the diffuser of the Kohler illumination system mainly uses the image sensor to collect the initial dynamic image of the measured object when the diffuser is rotating, analyzes whether the deviation displacement vector of the speckle keeps converging in the predetermined range, and then judges whether the diffuser is at the optimized position. If not, the position is continuously adjusted until the speckle position of the collected image is the original pattern, which means that the corrected position of the diffuser is the optimized position with the best light field uniformity. Compared with the prior art, which only uses the rotation of the diffuser to eliminate the speckle and cannot set the measured object to be under the most uniform illumination, the present application can indeed set the diffuser position at an optimized position that can make the light field uniformity of the measured object best, thereby effectively improving the quality of the collected image.

[0110] Through the above detailed description of the preferred embodiments, the features and spirits of the present application are expected to be more clearly described, and the scope of the present application is not limited by the above disclosed preferred embodiments. On the contrary, the purpose is to cover various changes and equivalent arrangements within the scope of the patent application of the present application.

Claims

1. A method for optimizing the position of a diffuser for a Kohler illumination system, for correcting a Kohler illumination system, characterized in that, The Kohler illumination system includes a laser light source, a condenser, 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 condenser, so that a laser beam emitted by the laser light source is uniformly diffused by rotation of the diffuser, and then sequentially irradiates a measured object through the condenser, the focusing lens, the beam splitter, and the objective lens, so that the image sensor collects an image reflected by the measured object through the tube lens, the beam splitter, and the objective lens. The calibration method of the Kohler illumination system includes the following steps: (A) When the diffuser is rotating, an initial measured object dynamic image of the diffuser at an initial position is collected by the image sensor, and whether a deviation displacement vector of at least one speckle keeps converging in a predetermined range is analyzed for the initial measured object dynamic image. The deviation displacement vector of the speckle is obtained by cross-correlation operation of at least one variable feature of the speckle; (B) If the deviation displacement vector of the at least one speckle keeps converging in the predetermined range in step (A), the initial position of the diffuser is defined as an optimized position with optimal light field uniformity, otherwise, step (C) is continued; and (C) If the deviation displacement vector of the at least one speckle exceeds the predetermined range in step (A), the position of the diffuser is adjusted until the deviation displacement vector of the at least one speckle keeps converging in the predetermined range, and then a corrected position of the diffuser after adjustment is defined as the optimized position with optimal light field uniformity.

2. The method of optimizing object distance adjustment of a Kohler illumination system of claim 1, wherein, The laser light source has an optical axis, and step (C) further includes the following steps: (C1) The diffuser is moved to a first corrected position along a first direction parallel to the optical axis, so that a first corrected dynamic image of the measured object is collected by the image sensor, and whether the deviation displacement vector of the at least one speckle keeps converging in the predetermined range is analyzed for the first corrected dynamic image; (C2) If the deviation displacement vector of the at least one speckle keeps converging in the predetermined range in step (C1), the corrected position of the diffuser at the first corrected position is defined as the optimized position with optimal light field uniformity, otherwise, step (C3) is continued; (C3) If the deviation displacement vector of the at least one speckle exceeds the predetermined range in step (C1), the diffuser is moved to a second corrected position along the first direction or a second direction opposite to the first direction, so that a second corrected dynamic image of the measured object is collected by the image sensor, and whether the deviation displacement vector of the at least one speckle keeps converging in the predetermined range is analyzed for the second corrected dynamic image. If the deviation displacement vector of the at least one speckle keeps converging in the predetermined range, the corrected position of the diffuser at the second corrected position is defined as the optimized position with optimal light field uniformity, otherwise, step (C4) is continued; and (C4) If the deviation displacement vector of the at least one speckle exceeds the predetermined range in step (C3), the diffuser is moved to a third corrected position along the first direction or the second direction, so that a third corrected dynamic image of the measured object is collected by the image sensor, and whether the deviation displacement vector of the at least one speckle keeps converging in the predetermined range is analyzed for the third corrected dynamic image. If the deviation displacement vector of the at least one speckle keeps converging in the predetermined range, the corrected position of the diffuser at the third corrected position is defined as the optimized position with optimal light field uniformity, otherwise, step (C5) is continued. (C4) repeating the step (C1) to the step (C3) until the deviation displacement vector of the at least one speckle keeps converging within the predetermined range, and defining the corrected position of the diffusion sheet as the optimized position with the best light field uniformity.

3. The method for optimizing the diffuser position adjustment of the Kohler lighting system as described in claim 2, characterized in that, The step (C3) is performed when the vector size of the deviation displacement vector of the at least one speckle in the step (C1) exceeds the predetermined range, and the direction of the deviation displacement vector of the at least one speckle in the step (C1) is opposite to the direction of the deviation displacement vector measured when the diffusion sheet is located at the previous position.

4. The method for optimizing the diffuser position adjustment of the Kohler lighting system as described in claim 2, characterized in that, The step (C3) is performed when the vector size of the deviation displacement vector of the at least one speckle in the step (C1) exceeds the predetermined range, and the direction of the deviation displacement vector of the at least one speckle in the step (C1) is opposite to the direction of the deviation displacement vector measured when the diffusion sheet is located at the previous position.

5. The method for optimizing the diffuser position adjustment of the Kohler lighting system as described in claim 2, characterized in that, The step (C3) is performed when the vector size of the deviation displacement vector of the at least one speckle in the step (C1) exceeds the predetermined range, and the direction of the deviation displacement vector of the at least one speckle in the step (C1) is opposite to the direction of the deviation displacement vector measured when the diffusion sheet is located at the previous position.

6. The method for optimizing the diffuser position adjustment of the Kohler lighting system as described in claim 2, characterized in that, The step (C3) is performed when the vector size of the deviation displacement vector of the at least one speckle in the step (C1) exceeds the predetermined range, and the direction of the deviation displacement vector of the at least one speckle in the step (C1) is opposite to the direction of the deviation displacement vector measured when the diffusion sheet is located at the previous position.

7. The method for optimizing the diffuser position adjustment of the Kohler lighting system as described in claim 2, characterized in that, The diffusion sheet is moved along the first direction to approach the light collector, and the diffusion sheet is moved along the second direction to move away from the light collector.

8. The method for optimizing the diffuser position adjustment of the Kohler lighting system as described in claim 2, characterized in that, The diffusion sheet is moved along the first direction to move away from the light collector, and the diffusion sheet is moved along the second direction to approach the light collector.

9. The method for optimizing the diffuser position adjustment of the Kohler lighting system as described in claim 2, characterized in that, The step (A) is performed by a computer host electrically connected to the image sensor to analyze the initial object dynamic image, the step (C1) is performed by the computer host to analyze the first corrected dynamic image, and the step (C3) is performed by the computer host to analyze the second corrected dynamic image.

10. The method for optimizing the diffuser position adjustment of the Kohler lighting system as described in claim 1, characterized in that, The first corrected dynamic image comprises two first corrected static images with a time difference therebetween, and the second corrected dynamic image comprises two second corrected static images with a time difference therebetween. The initial object dynamic image comprises two initial static images with a time difference therebetween. The initial object dynamic image comprises two initial static images with a time difference therebetween.

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