Position adjustment device

Abstract

To provide a position adjustment device in which even when vibration occurs in a target object, visual feedback control of adjusting the position of the target object to a target position using a captured image can be stably and properly performed.SOLUTION: A position adjustment device 1 includes a placement unit on which a target object is placed, a stage servo circuit 131 that drives the placement unit to change the position of the target object, an acceleration sensor 14 that detects the vibration of the target object, a vibration processing unit 124 that detects the cycle of the vibration on the basis of a detection signal from the acceleration sensor 14, and a signal generation unit 12 that, during visual feedback control of moving the target object to a target position, acquires a captured image from a camera 11 capturing the target object at an acquisition timing based on the cycle of the vibration, generates a control signal for moving the target object to the target position from the acquired captured images, and sequentially outputs the generated control signals to a driving unit.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a position adjustment device for adjusting the position of an object. [Background technology]

[0002] Conventionally, position adjustment devices for adjusting the position of an object have been used in various devices. For example, a position adjustment device that adjusts the position of an object placed on a mounting surface of an XYθ stage by controlling the XYθ stage is known. In addition, in inspection, measurement, or character recognition situations, the relative position between a camera and an object is adjusted so that the imaging field of view matches the target range of the inspection, measurement, or character recognition.

[0003] The following Patent Document 1 describes a control system for adjusting the position of a workpiece on an XY stage. In this control system, two positioning marks on the workpiece are photographed by two cameras, and the difference between the current position and the target position of the workpiece is calculated. The amount of movement of the stage is then calculated based on the calculated difference, and the stage is driven by a distance and angle corresponding to this amount of movement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-203365 Summary of the Invention [Problem to be solved by the invention]

[0005] In the position adjustment device using the camera described above, when vibrations are applied to the stage and the object on the stage, the object vibrates in the imaging area of ​​the camera. As a result, the image of the object in a state where vibration blur (a blur relative to the position when there is no vibration) occurs is used for adjusting the position of the object, and the position adjustment control using the image cannot be performed properly.

[0006] In view of such problems, the present invention aims to provide a position adjustment device that can stably and appropriately perform visual feedback control, which adjusts the position of an object to a target position using captured images, even when vibrations occur in the object. [Means for solving the problem]

[0007] A position adjustment device according to a main aspect of the present invention comprises an installation unit on which an object is installed, a drive unit that drives the installation unit to change the position of the object, a detection unit that detects vibrations of the object, a vibration processing unit that detects the period of the vibrations based on a detection signal from the detection unit, and a signal generation unit that, in visual feedback control for moving the object to a target position, acquires captured images from a camera that images the object at an acquisition timing based on the period of the vibrations, generates control signals from each of the acquired captured images to move the object to the target position, and sequentially outputs the generated control signals to the drive unit.

[0008] According to the position adjustment device of this aspect, captured images for visual feedback control are acquired at acquisition timing based on the vibration period. Therefore, captured images with reduced vibration blur (blur relative to the position when there is no vibration) can be used for visual feedback control. Therefore, even if vibration occurs in the object, visual feedback control can be performed stably and appropriately. [Effects of the Invention]

[0009] As described above, according to the present invention, a position adjustment device can be provided that can stably and appropriately perform visual feedback control, which uses captured images to adjust the position of an object to a target position, even when vibrations occur in the object.

[0010] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a side view schematically showing the configuration of a position adjustment device according to the first embodiment. [Figure 2] 2(a) and 2(b) are top views each showing a schematic diagram of the operation of adjusting the position of an object on a stage according to the first embodiment. [Figure 3] FIG. 3 is a block diagram showing the configuration of a circuit section of a signal generating section according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating a correlation between a coordinate system of a captured image and a coordinate system for device control according to the first embodiment. [Figure 5] FIG. 5 is a time chart showing the process of visual feedback control executed by the control signal output from the signal generating unit according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating a schematic diagram showing that the position of the mark of the object vibrates in the captured image according to the first embodiment. [Figure 7] 7(a) is a graph for explaining acquisition of the period and frequency of vibration of an object according to embodiment 1. Fig. 7(b) is a graph for explaining a method for setting the imaging timing in the calibration process according to embodiment 1. [Figure 8] Fig. 8(a) is a schematic diagram for explaining acquisition of the reference timing according to the embodiment 1. Fig. 8(b) is a graph for explaining setting of the acquisition timing according to the embodiment 1. [Figure 9] Fig. 9(a) is a flowchart showing processing by the position adjustment device according to embodiment 1. Fig. 9(b) is a flowchart showing calibration processing according to embodiment 1. [Figure 10] FIG. 10 is a diagram schematically illustrating an ideal trajectory and additional disturbance vibration according to the second embodiment. [Figure 11] FIG. 11 is a graph schematically showing the vibration amount of the object relative to the ideal trajectory, the image capturing timing, and the positional deviation amount of the object relative to the ideal trajectory according to the second embodiment. [Figure 12] FIG. 12 is a flowchart showing a process performed by the position adjustment device according to the second embodiment. [Figure 13] FIG. 13 is a graph illustrating that spike-like vibration components are superimposed on the vibration waveform when acceleration and deceleration operations on the stage start and end, according to a modification of the second embodiment. [Figure 14] FIG. 14 is a flowchart showing a process performed by the position adjustment device according to a modification of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] <Embodiment 1> In the following embodiments, the present invention is applied to a position adjustment device that adjusts the position of an object placed on the upper surface of an XYθ stage by controlling the XYθ stage. The object is, for example, a circuit board. The drive device that drives the object is an XYθ stage. However, the application of the present invention is not limited to this type of position adjustment device. The present invention can be applied to various devices that require position adjustment.

[0014] Fig. 1 is a side view schematically showing the configuration of the position adjustment device 1. Mutually perpendicular X, Y and Z axes are indicated in Fig. 1. The positive direction of the Z axis is the vertically upward direction, which is the height direction of the position adjustment device 1.

[0015] The position adjustment device 1 includes a camera 11, a signal generation unit 12, an XYθ stage 13 (hereinafter referred to as the “stage 13”), and an acceleration sensor 14.

[0016] Camera 11 captures an image of a predetermined range from above, including object 31 placed on the top surface of stage 13. Signal generator 12 outputs a control signal to stage 13 for positioning object 31 at a target position. Stage 13 drives the top plate on which object 31 is placed, based on the control signal input from signal generator 12. Stage 13 is installed on the top surface of installation table 15. Acceleration sensor 14 is installed near the outer edge of the top surface of stage 13, and detects acceleration acting on stage 13. Acceleration sensor 14 detects acceleration at least in a direction parallel to the XY plane.

[0017] 2(a) and 2(b) are top views that schematically show the operation of adjusting the position of the object 31 on the stage 13. FIG.

[0018] Stage 13 includes a base 13a, an X-stage 13b, a Y-stage 13c, and a top plate 13d. X-stage 13b is supported on base 13a so as to be movable in the X-axis direction, and is driven by a motor in the X-axis direction. Y-stage 13c is supported on X-stage 13b so as to be movable in the Y-axis direction, and is driven by a motor in the Y-axis direction. Top plate 13d is supported on Y-stage 13c so as to be rotatable about a rotation axis that passes through the center of Y-stage 13c and is parallel to the Z-axis, and is rotated about the rotation axis by a motor.

[0019] When the object 31 is placed on the top plate 13d in the state shown in FIG. 2(a), the stage 13 drives the motors that drive the X-stage 13b, Y-stage 13c, and top plate 13d in response to a control signal from the signal generator 12, thereby driving the X-stage 13b, Y-stage 13c, and top plate 13d as shown in FIG. 2(b). As a result, the marks 31a provided near the corners of the object 31 are aligned with the target position P0, and the center of the marks 31a is aligned with the center of the target position P0. The marks 31a have a shape that makes it possible to distinguish the positions of the object 31 in the X-axis and Y-axis directions and the rotational position of the object 31 around the Z-axis. The marks 31a in FIGS. 2(a) and 2(b) have a shape formed by two rectangles intersecting at 90°. In this way, the position adjustment of the object 31 is completed.

[0020] 1 , the robot arm 2 places an article 32 on the target object 31 whose position has been adjusted as described above. If the target object 31 is a circuit board, the article 32 is a component to be placed on the circuit board. The robot arm 2 includes an arm 21, a first drive unit 22, a rotating shaft 23, a second drive unit 24, and a holding mechanism 25.

[0021] Arm 21 is a rod-shaped member extending in one direction. First drive unit 22 supports arm 21 and drives arm 21 in the longitudinal direction. Rotating shaft 23 is a cylindrical member extending vertically, and supports first drive unit 22 at its upper end. Second drive unit 24 rotates rotating shaft 23 in the circumferential direction. Holding mechanism 25 is a mechanism that can hold and release article 32. Here, holding mechanism 25 is made up of multiple fingers that open and close horizontally. Holding mechanism 25 may also be able to raise and lower the fingers.

[0022] Under the control of a controller (not shown), the robot arm 2 causes the holding mechanism 25 to hold the item 32 in the storage area for the item 32, and then drives the first drive unit 22 and the second drive unit 24 to transport the item 32 to an installation position on the target object 31, and releases the item 32 from the holding mechanism 25. As a result, the item 32 is installed at a predetermined position on the target object 31.

[0023] FIG. 3 is a block diagram showing the configuration of the circuit section of the signal generating section 12. As shown in FIG.

[0024] The signal generation unit 12 includes an image processing unit 121, a movement amount calculation unit 122, a control signal generation unit 123, and a vibration processing unit 124. The image processing unit 121, the movement amount calculation unit 122, the control signal generation unit 123, and the vibration processing unit 124 are configured by, for example, a function executed by a microcomputer according to a control program, an FPGA (Field Programmable Gate Array), or the like.

[0025] The image processing unit 121 causes the camera 11 to capture an image at a specified timing. The image processing unit 121 analyzes the captured image input from the camera 11 and extracts a predetermined target position (target position P0 in FIGS. 2(a) and 2(b)) and the current position of the target object 31 (mark 31a in FIGS. 2(a) and 2(b)) from the captured image.

[0026] A target position on the stage 13 (target position P0 in FIGS. 2(a) and 2(b)) and a detection target for the object 31 (mark 31a in FIGS. 2(a) and 2(b)) are set in the image processing unit 121 by the user via an external controller (not shown). The image processing unit 121 extracts the target position (target position P0 in FIGS. 2(a) and 2(b)) and the current position of the object 31 (mark 31a in FIGS. 2(a) and 2(b)) from the captured image by image analysis in accordance with this setting. The image processing unit 121 outputs position information of the target position and the current position on the captured image to the movement amount calculation unit 122.

[0027] Based on the target position and the current position extracted by the image processing unit 121, the movement amount calculation unit 122 calculates the movement amount (direction, distance) for moving the current position to the target position.

[0028] The control signal generating unit 123 generates a control signal for moving the target object 31 (mark 31a) to the target position, i.e., the drive amount of each motor that drives the X stage 13b, Y stage 13c, and top plate 13d in Figure 2(b), from the movement amount calculated by the movement amount calculating unit 122.

[0029] More specifically, the control signal generating unit 123 uses the correlation data to convert the amount of movement on the captured image calculated by the movement amount calculating unit 122 (the amount of movement in the coordinate system of the captured image) into the amount of movement in the coordinate system for drive control of the stage 13. From the converted amount of movement, the control signal generating unit 123 generates drive amounts for the motors that drive the X stage 13b, the Y stage 13c, and the top plate 13d, and outputs these generated drive amounts to the stage servo circuit 131.

[0030] The control signal generating unit 123 outputs the speed at which each motor drives the object 31, along with the drive amount of each motor, to the stage servo circuit 131. The movement speed and maximum acceleration of the object 31 are set in the control signal generating unit 123 from an external controller (not shown). Based on this setting, the control signal generating unit 123 generates a speed waveform at which each motor drives the object 31, and outputs a speed corresponding to the speed waveform to the stage servo circuit 131.

[0031] The stage servo circuit 131 drives each motor at the drive amount and speed input from the control signal generating unit 123 .

[0032] The vibration processing unit 124 processes the detection signal of the acceleration sensor 14 to obtain the amount of vibration of the stage 13 (the object 31 on the stage 13), and detects the period and frequency of the vibration based on the obtained amount of vibration. The vibration processing unit 124 then outputs the detected period and frequency of the vibration to the image processing unit 121. The processing using the period and frequency of the vibration will be described later with reference to FIGS. 7(a) to 8(b).

[0033] FIG. 4 is a diagram showing a schematic diagram of the correlation between the coordinate system of the captured image and the coordinate system of the device control.

[0034] In Fig. 4, the coordinate system indicated by the mutually orthogonal x-axis and y-axis is the coordinate system of the captured image, and the coordinate system indicated by the mutually orthogonal x-axis and y-axis is the coordinate system of the device control. The x-axis and y-axis in the device control coordinate system are parallel to the x-axis and y-axis in Fig. 1, respectively.

[0035] The coordinate plane of the coordinate system for the captured image and the coordinate plane of the coordinate system for device control are the same plane parallel to the XY plane. The origin of the coordinate system for the captured image and the origin of the coordinate system for device control are different from each other. The coordinate system for the captured image is tilted at a predetermined angle in a direction parallel to the XY plane with respect to the coordinate system for device control.

[0036] Furthermore, a rotating coordinate system that rotates about a center O is set for each of the coordinate system of the imaging device and the coordinate system of the device control. The centers O (origins) of the respective rotating coordinate systems coincide with each other.

[0037] The correlation between these two coordinate systems can be expressed by the following equation:

[0038] x=a1·X+b1·Y … (1) y=a2·X+b2·Y … (2) θ=c·β … (3)

[0039] In equation (3), θ is the rotation angle of the rotating coordinate system of the captured image, and β is the rotation angle of the rotating coordinate system of the device control.

[0040] 4, to align the mark 31a with the target position P0, it is necessary to move the center P11 of the mark 31a to the center P01 of the target position P0 in the coordinate system of the captured image, and then rotate the mark 31a clockwise by θ1. In this case, the movement amounts on the captured image are the movement amounts x1 and y1 for moving the center P11 to the center P01, and the clockwise movement amount θ1 of the mark 31a.

[0041] 3 calculates x1, y1, and θ1, which are the amounts of movement on the captured image, based on the current position of the mark 31a and the target position P0. The control signal generation unit 123 also applies these amounts of movement to the above equations (1) to (3) to calculate the amounts of movement X1, Y1, and β1 for device control. In this way, the object 31 is moved so that the mark 31a of the object 31 is aligned with the target position P0.

[0042] FIG. 5 is a time chart showing the process of visual feedback control executed by the control signal output from the signal generating unit 12. In FIG.

[0043] By performing an analysis process on the captured image, position information of the target position P0 and the object 31 (mark 31a) on the captured image is output from the image processing unit 121 to the movement amount calculation unit 122. This analysis process requires a period Δta.

[0044] When the position information is output, a movement amount calculation unit 122 calculates the movement amount on the captured image, and a control signal generation unit 123 generates a control signal (movement amount and speed in the coordinate system for device control). The processing by the movement amount calculation unit 122 and the control signal generation unit 123 requires periods Δtb and Δtc, respectively. The generated control signal is supplied to a stage servo circuit 131.

[0045] The stage servo circuit 131 drives the stage 13 based on the input control signal. As a result, the object 31 (mark 31a) moves toward the target position P0. The solid arrows in FIG. 5 indicate that the object 31 is being moved. The attached V11 to V15 indicate the moving speed of the object 31.

[0046] When the analysis process for one captured image is completed, the image processing unit 121 processes the next captured image and outputs position information to the movement amount calculation unit 122. As a result, a control signal based on the next captured image is output to the stage servo circuit 131. This control signal may be supplied to the stage servo circuit 131 during the process of moving the object 31 based on the control signal based on the previous captured image. In this case, the stage servo circuit 131 executes control based on the new control signal instead of moving the object 31 based on the previous control signal. The dashed line in FIG. 5 indicates that the movement of the object 31 has been stopped by the new control signal.

[0047] In this way, in visual feedback control, when a new control signal is generated by analyzing the captured image, the movement control of the object 31 is updated to control based on the new control signal. Therefore, as schematically shown in the bottom part of Figure 5, the position of the object 31 (mark 31a) quickly and accurately converges to the target position P0 without substantially overshooting the target position P0. This allows the object 31 (mark 31a) to be quickly and accurately positioned at the target position P0.

[0048] Incidentally, when visual feedback control is performed as described above, if the stage 13 and the object 31 vibrate due to the external environment or the like, the position of the mark 31a of the object 31 in the captured image will also vibrate, as shown in Fig. 6. In this case, visual feedback control will be performed based on the mark 31a whose position has shifted due to the vibration, making it difficult to accurately position the object 31 at the target position.

[0049] Therefore, in this embodiment, a calibration process is performed before visual feedback control is performed to set the timing for capturing an image taking vibration into consideration, and the image is captured at the set timing. This allows an appropriate captured image to be captured in which positional deviation of the mark 31a due to vibration is suppressed. The calibration process will be described below with reference to FIGS. 7(a) to 8(b).

[0050] FIG. 7(a) is a graph for explaining how to obtain the period T1 and frequency F1 of the vibration of the object 31.

[0051] The graph in Fig. 7(a) shows the amount of vibration acquired by the vibration processing unit 124 based on the acceleration sensor 14 when vibration is occurring. It can be assumed that the vibration detected by the acceleration sensor 14 has a substantially constant amplitude and period. In the calibration process, the vibration processing unit 124 acquires the amount of vibration based on the detection signal from the acceleration sensor 14, and acquires the period T1 and frequency F1 (=1 / T1) of the vibration of the target object 31 based on the acquired vibration amount.

[0052] FIG. 7(b) is a graph for explaining a method for setting the image capturing timing in the calibration process.

[0053] In the calibration process, the image processing unit 121 causes the camera 11 to capture images at a period T2 that is shorter than the period T1 acquired by the vibration processing unit 124. In FIG. 7(b), the image capturing timing is, for example, the timing indicated by the dashed line box. In other words, the image processing unit 121 causes the camera 11 to capture images at a frequency F2 that is higher than the frequency F1 acquired by the vibration processing unit 124. In the first embodiment, for example, the period T2 is 1 / 4 of the period T1, and the frequency F2 is 4 times the frequency F1.

[0054] FIG. 8(a) is a schematic diagram for explaining how the reference timing is obtained.

[0055] The reference timing is a timing for defining the imaging timing in visual feedback control.

[0056] As shown in Fig. 7(b), when imaging is performed in the calibration process at a period T2 shorter than the period T1 of the vibration of the object 31, multiple states of the periodically vibrating object 31 are captured, as shown in Fig. 8(a). The image processing unit 121 analyzes the vibration of the object 31 in the coordinate system of the captured images based on the multiple captured images each showing a multiple state, and determines the reference timing at which the object 31 is positioned near the center of the vibration amplitude. For example, the image processing unit 121 calculates the vibration waveform of the object 31 in the coordinate system of the captured images from the multiple captured images acquired over a predetermined period, and sets the timing at which the amplitude center arrives in the calculated vibration waveform as the reference timing.

[0057] FIG. 8(b) is a graph for explaining the setting of the acquisition timing.

[0058] In the calibration process, the image processing unit 121 sets the acquisition timing to a timing synchronized with the determined reference timing. In Fig. 8(b), the acquisition timing is the timing enclosed by the dashed line, which coincides with the reference timing. Therefore, the acquisition timing is the timing at which the object 31 is positioned near the center of amplitude in the coordinate system of the captured image.

[0059] Here, as shown in FIG. 8(b), the phase of the vibration of the object 31 in the coordinate system of the captured image may differ from the phase of the vibration based on the acceleration sensor 14 acquired by the vibration processing unit 124. For this reason, if the amplitude center of the vibration based on the acceleration sensor 14 shown in FIG. 8(b) (the vibration shown in FIG. 7(a)) is set as the acquisition timing, this acquisition timing may deviate from the timing at which the object 31 is actually positioned near the amplitude center in the coordinate system of the captured image. For this reason, in the first embodiment, a reference timing is set based on the captured image, and a series of timings synchronized with the reference timing are set as the acquisition timing. As a result, the acquisition timing becomes the timing at which the object 31 is actually positioned near the amplitude center in the coordinate system of the captured image.

[0060] Here, all the reference timings are set to the timings for acquiring the captured images, and the period of the acquisition timings is 1 / 2 of the vibration period T1. However, the reference timings may be set to the timings for acquiring the captured images every predetermined number of times. For example, every other reference timing may be set to the timings for acquiring the captured images. In this case, the period of the timings for acquiring the captured images will be the same as the vibration period T1.

[0061] In this way, when the acquisition timing is set in the calibration process and visual feedback control is started, the image processing unit 121 causes the camera 11 to capture an image at the acquisition timing. This allows the image processing unit 121 to capture an appropriate captured image in which positional deviation of the mark 31a due to vibration is suppressed. Therefore, the appropriate captured image can be used to perform visual feedback control with high accuracy.

[0062] FIG. 9(a) is a flowchart showing the processing performed by the position adjustment device 1.

[0063] The image processing unit 121 performs the calibration process described above (S11). The calibration process in step S11 is performed in a state where the object 31 is stationary before the start of visual feedback control. Subsequently, the image processing unit 121 starts visual feedback control (S12). Thereafter, the signal generating unit 12 generates a control signal for moving the object 31 (mark 31a) to the target position, and outputs the control signal to the stage servo circuit 131. As a result, the object 31 is moved to the target position.

[0064] FIG. 9B is a flowchart showing the calibration process.

[0065] As shown in FIG. 7(a), the vibration processing unit 124 acquires the period T1 and frequency F1 of vibration based on the detection signal of the acceleration sensor 14 (S101). Next, as shown in FIG. 7(b), the image processing unit 121 acquires captured images at a period T2 shorter than the period T1 acquired in step S101, and as shown in FIG. 8(a), determines a reference timing based on the captured images (S102). Next, as shown in FIG. 8(b), the image processing unit 121 sets acquisition timing based on the reference timing acquired in step S102 (S103). In step S103, the image processing unit 121 sets all of the reference timings to the acquisition timing of the captured images, for example, as shown in FIG. 8(b).

[0066] <Effects of the First Embodiment> According to the first embodiment, the following effects are achieved.

[0067] An object 31 is placed on the stage 13 (placement unit). A stage servo circuit 131 (drive unit) drives the stage 13 (placement unit) to change the position of the object 31. An acceleration sensor 14 (detection unit) detects vibration of the object 31. A vibration processing unit 124 detects a vibration period T1 (see FIG. 7(a)) based on a detection signal from the acceleration sensor 14 (detection unit). In visual feedback control for moving the object 31 to a target position, a signal generation unit 12 acquires captured images from a camera 11 that captures an image of the object 31 at an acquisition timing (see FIG. 8(b)) based on the vibration period T1, generates a control signal for moving the object 31 to the target position from each acquired captured image, and sequentially outputs the generated control signals to the stage servo circuit 131 (drive unit).

[0068] According to this configuration, captured images for visual feedback control are acquired at acquisition timing based on the vibration period T1. Therefore, captured images with reduced vibration blur (blur relative to the position when there is no vibration) can be used for visual feedback control. Therefore, even if vibration occurs in the target object 31, visual feedback control can be performed stably and appropriately.

[0069] The signal generating unit 12 causes the camera 11 to capture an image at the capture timing (see FIG. 8(b)) to acquire the captured image.

[0070] This configuration limits the capture timing of the camera 11 to the capture timing based on the vibration period T1. This prevents the capture and processing of images with vibration blur. This allows for appropriate visual feedback control while reducing power consumption.

[0071] In the calibration process for setting the acquisition timing, the signal generating unit 12 acquires multiple captured images from the camera 11 at a period T2 (see FIG. 7(b)) that is shorter than the vibration period T1 (see FIG. 7(a)), determines a reference timing from the acquired multiple captured images at which the object 31 is positioned near the center of the vibration amplitude (see FIG. 8(a)), and sets the acquisition timing (see FIG. 8(b)) based on the determined reference timing.

[0072] The timing at which the object 31 is positioned near the center of the vibration amplitude in the imaging area substantially matches the timing at which the object 31 would be positioned when there is no vibration blurring of the object 31. With this configuration, by using this timing as the reference timing and setting the timing for capturing captured images based on the vibration period T1, it is possible to sequentially capture captured images similar to those captured when there is no vibration blurring. Therefore, by using these captured images for visual feedback control, the visual feedback control can be performed appropriately.

[0073] As shown in FIG. 7(b), the signal generating unit 12 sets another period T2 so that at least four captured images are acquired during one period of vibration (period of period T1).

[0074] This configuration allows smooth and accurate detection of vibrations of the object 31 in the imaging area, and accurately determines the reference timing at which the object 31 is positioned near the center of amplitude, thereby enabling accurate visual feedback control.

[0075] As shown in FIG. 9(a), the signal generating unit 12 performs a calibration process (S11) to set the acquisition timing (see FIG. 8(b)) before starting visual feedback control (S12).

[0076] According to this configuration, the subsequent visual feedback control can be carried out appropriately and stably.

[0077] The signal generation unit 12 includes an image processing unit 121 that extracts the position of the object 31 and the target position from the captured image, and a control signal generation unit 123 that generates a control signal based on the extracted position and target position of the object 31. The image processing unit 121 acquires the captured image and performs calibration processing in visual feedback control.

[0078] According to this configuration, the image processing unit 121 can smoothly perform captured image-related processes, such as acquisition of captured images in visual feedback control and calibration processing.

[0079] <Embodiment 2> In the first embodiment, the calibration process is performed only when the target object 31 is stationary before the visual feedback control is executed. In contrast, in the second embodiment, the calibration process is also performed when additional disturbance vibration occurs after the visual feedback control is started.

[0080] FIG. 10 is a diagram schematically illustrating an ideal trajectory and additional disturbance vibration according to the second embodiment.

[0081] When the object 31 (mark 31a) moves from the start position P1 to the target position P0, first, while the object 31 is positioned at the start position P1 (stopped state), the above-described calibration process is performed and the acquisition timing (see FIG. 8(b)) is set. Then, visual feedback control is started. At this time, captured images are sequentially acquired at the acquisition timing set at the start position P1, and visual feedback control is performed. As a result, the object 31 (mark 31a) moves from the start position P1 to the target position P0 along an ideal trajectory connecting the start position P1 and the target position P0 as shown in FIG. 10.

[0082] Here, if an additional disturbance vibration occurs in a direction parallel to the xy plane while the object 31 is moving, the vibration of the object 31 will be different from the initial vibration (when the object 31 is stationary). Therefore, the timing at which the object 31 is positioned near the center of the vibration amplitude will deviate from the acquisition timing acquired when the object 31 is stationary. Therefore, if an image captured at the initial acquisition timing is used for visual feedback control after the additional disturbance vibration occurs, there is a risk that the transfer path of the object 31 will deviate from the ideal trajectory.

[0083] Therefore, in the second embodiment, if an additional disturbance vibration occurs in a direction parallel to the xy plane while the object 31 is moving, the calibration process is performed again and the acquisition timing is updated. Below, the update of the acquisition timing in the second embodiment will be described using as an example a case where the object 31 moves from the start position P1 to the target position P0 on the captured image from times t1 to t6.

[0084] FIG. 11 is a graph that schematically shows the vibration amount of the object 31 relative to the ideal trajectory, the image capturing timing, and the positional deviation amount of the object 31 relative to the ideal trajectory.

[0085] In the example of FIG. 11, initial vibration occurs when the object 31 (mark 31a) is positioned at the start position P1. In this state, calibration processing is performed as in the first embodiment. At this time, an ideal trajectory connecting the start position P1 and the target position P0 is generated on the captured image. The ideal trajectory includes, for example, the elapsed time from the start position and a position on the xy plane corresponding to the elapsed time. Thereafter, visual feedback control is initiated, and the object 31 moves toward the target position P0.

[0086] Between times t1 and t2, as shown in the upper graph, the object 31 moves toward the target position P0 while vibrating relative to the ideal trajectory. At this time, as shown in the middle graph, the image capture timing of the camera 11 is the capture timing at the start position P1, that is, the timing when the object 31 is positioned near the center of the vibration amplitude. As a result, as shown in the lower graph, the positional deviation of the object 31 (mark 31a) relative to the ideal trajectory in the captured image is approximately zero.

[0087] Thereafter, when the time of the object 31 (mark 31a) reaches t2, an additional disturbance vibration occurs in a direction parallel to the xy plane.

[0088] Between times t2 and t3, as shown in the upper graph, the vibration waveform of the object 31 differs from the vibration waveform between times t1 and t2 due to the additional disturbance vibration. In this case, as shown in the middle graph, the imaging timing remains the same as between times t1 and t2, so the amount of positional deviation of the object 31 from the ideal trajectory increases, as shown in the lower graph. When the amount of positional deviation of the object 31 from the ideal trajectory increases in this way, the signal generating unit 12 performs calibration processing again to update the acquisition timing.

[0089] Between times t3 and t4, the vibration processing unit 124 acquires the vibration period T21 of the target object 31 based on the detection signal of the acceleration sensor 14. Note that the visual feedback control based on the acquisition timing acquired at the start position P1 continues until the timing (time t4) when imaging starts at a new imaging timing in the calibration process that is performed again.

[0090] Subsequently, from time t4 to t5, the image processing unit 121 causes the camera 11 to capture images at a cycle T22, which is shorter than the cycle T21. The cycle T22 is, for example, four times the cycle T21. At this time, as shown in the middle graph, the camera 11 captures images at a high frequency, and therefore, as shown in the lower graph, multiple states of the periodically vibrating object 31 are captured. Based on the captured images captured at the cycle T22, the image processing unit 121 determines a reference timing at which the object 31 is positioned near the center of the vibration amplitude. The image processing unit 121 sets the capture timing at a cycle T21 / 2, synchronized with the reference timing determined in the calibration process from time t3 to t5. Note that from time t4 to t5, visual feedback control is performed based on the captured images captured at the cycle T22.

[0091] After time t5, as shown in the middle graph, the image processing unit 121 causes the camera 11 to capture images at the capture timings obtained in the calibration process from time t3 to t5. This allows the image processing unit 121 to capture an appropriate captured image in which positional deviation of the mark 31a due to vibration is suppressed. Therefore, as shown in the bottom graph, the amount of positional deviation of the object 31 (mark 31a) from the ideal trajectory in the captured image is approximately zero. Therefore, after time t5, visual feedback control can be performed appropriately using the captured image thus obtained.

[0092] FIG. 12 is a flowchart showing the processing performed by the position adjustment device 1 according to the second embodiment.

[0093] In the process of FIG. 12, compared to the process of the first embodiment in FIG. 9(a), step S21 is added between step S11 and step S12, and steps S22 to S24 are added after step S12.

[0094] The signal generation unit 12 performs a calibration process in a stopped state to acquire an acquisition timing (S11). The image processing unit 121 estimates an ideal trajectory for moving the start position P1 (initial position) of the object 31 to the target position P0 from the captured image of the camera 11 (S21). Then, the signal generation unit 12 starts visual feedback control (S12). As a result, the image processing unit 121 acquires a captured image at the acquisition timing acquired in step S11, and the signal generation unit 12 performs visual feedback control using the position of the object 31 (mark 31a) on the captured image.

[0095] Next, the image processing unit 121 determines whether the amount of deviation of the target object 31 (mark 31a) from the ideal trajectory in the captured image is equal to or greater than a predetermined threshold Dth (S22). The threshold Dth is set to a value slightly larger than the amount of deviation that would normally occur in the absence of vibration under visual feedback control.

[0096] If the amount of deviation of the object 31 is equal to or greater than the threshold value Dth (S22: YES), the image processing unit 121 performs the same calibration process as in step S11 (S23). This process is the same as the procedure performed, for example, from time t3 to time t5 in FIG. 11. This updates the acquisition timing. If the amount of deviation of the object 31 is smaller than the threshold value Dth (S22: NO), it is determined that no additional disturbance vibration has occurred and no further calibration process is necessary, and the process proceeds to step S24.

[0097] The image processing unit 121 determines whether the object 31 has reached the target position on the captured image (S24). If the object 31 has not reached the target position (S24: NO), the process returns to step S22. On the other hand, if the object 31 has reached the target position (S24: YES), the process of FIG. 12 ends.

[0098] <Effects of the Second Embodiment> According to the second embodiment, the following effects are achieved.

[0099] As shown in FIG. 12, after the start of visual feedback control, the signal generating unit 12 executes a calibration process (S23) and updates the acquisition timing based on the fact that a predetermined condition that may change the vibration of the object 31 is satisfied (S22: YES).

[0100] This configuration allows for smooth response to changes in vibration after the start of visual feedback control, thereby enabling subsequent visual feedback control to proceed appropriately and stably.

[0101] As shown in FIG. 12, the signal generating unit 12 estimates an ideal trajectory for moving the initial position of the object 31 to the target position from the captured image of the camera 11 (S21), and when a predetermined condition is met in visual feedback control that the position of the object 31 in the captured image acquired from the camera 11 at a predetermined period T1 deviates from the ideal trajectory (S22), the signal generating unit 12 performs a calibration process to update the acquisition timing (S23).

[0102] This configuration allows for accurate determination of a change in the vibration state and accurate updating of the acquisition timing, thereby enabling subsequent visual feedback control to proceed accurately and stably.

[0103] <Modification of the second embodiment> In the modification of the second embodiment, when an additional disturbance vibration occurs during the movement of the object 31, if the acceleration or deceleration operation of the stage 13 is started or ended, the execution of the calibration process is put on hold.

[0104] FIG. 13 is a graph for explaining that spike-like vibration components are superimposed on the vibration waveform when the acceleration and deceleration operations for the stage 13 start and end, according to this modified example.

[0105] 13, the top graph shows the moving speed of stage 13, the second graph shows the acceleration applied to stage 13, the third graph shows the jerk (jerk, jerk) applied to stage 13, and the bottom graph shows the vibration occurring in object 31 on stage 13. Time t1 is the start timing of the acceleration operation, time t2 is the end timing of the acceleration operation, time t3 is the start timing of the deceleration operation, and time t4 is the end timing of the deceleration operation.

[0106] 13, the acceleration changes suddenly at times t1, t2, t3, and t4. This causes the jerk to change suddenly at times t1, t2, t3, and t4, resulting in an impulse-like jerk waveform. This impulse-like jerk impacts the stage 13 and the object 31, causing short-term shock vibrations in the stage 13 and the object 31, as shown in the bottom graph.

[0107] Therefore, in this modification, the calibration process that is executed when additional disturbance vibration occurs is not executed during the period Pd1 in which short-term impact vibration occurs, but is executed during the subsequent period Pd2.

[0108] FIG. 14 is a flowchart showing the processing by the position adjustment device 1 according to this modified example.

[0109] In the process of Fig. 14, steps S31 and S32 are added between steps S22 and S23, compared to the process of the second embodiment of Fig. 12. The process different from Fig. 12 will be described below.

[0110] When an additional disturbance vibration occurs and the displacement of the object 31 becomes equal to or greater than the threshold value Dth (S22: YES), the image processing unit 121 determines whether an acceleration or deceleration operation has started or ended (S31). Specifically, the image processing unit 121 determines YES in step S31 if an acceleration or deceleration operation has started or ended within a predetermined time period counting back from the time when the image processing unit 121 determined YES in step S22. The image processing unit 121 determines whether an acceleration or deceleration operation has started or ended within the predetermined time period based on the speed information from the control signal generation unit 123.

[0111] If an acceleration or deceleration operation has started or ended (S31: YES), the image processing unit 121 waits for a predetermined time to elapse from the start or end of the acceleration or deceleration operation (S32). As a result, the period Pd1 (see FIG. 13) of short-term impact vibration that occurs when the acceleration or deceleration operation starts or ends has passed, and the current time becomes included in a period Pd2 other than the period Pd1.

[0112] When the predetermined time has elapsed in step S32 (S32: YES), the image processing unit 121 acquires a captured image for the calibration process from the camera 11, executes the calibration process, and updates the acquisition timing (S23).

[0113] If acceleration or deceleration has not started or ended (S31: NO), there is no short-term impact vibration and there is no need to wait, so the process proceeds to step S23.

[0114] <Effects of the modified example of the second embodiment> According to this modification, the following effects are achieved.

[0115] The signal generating unit 12 acquires an image for the calibration process from the camera 11 during a period Pd2 (see FIG. 13) other than the period Pd1 of impact vibration caused by the start and end of acceleration or deceleration operation on the stage 13 (installation portion), and performs the calibration process (S23 in FIG. 14).

[0116] This configuration makes it possible to prevent captured images that are unstable due to shock vibrations from being used in the calibration process, thereby enabling the acquisition timing to be updated appropriately in the calibration process.

[0117] <Other change examples> The configuration of the position adjustment device 1 can be modified in various ways in addition to the configurations shown in the above embodiment and modified examples.

[0118] In the above embodiment and modified examples, calibration processing may be similarly performed for vibrations in the Z-axis direction. In this case, the vibration processing unit 124 detects the period of vibration of the object 31 in the Z-axis direction based on the detection signal of the acceleration sensor 14. The image processing unit 121 acquires multiple captured images from the camera 11 at a period shorter than the period detected by the acceleration sensor 14. The image processing unit 121 analyzes focus fluctuations corresponding to the vibrations in the Z-axis direction from the multiple acquired captured images, interprets the analyzed focus fluctuations as vibrations of the object 31, determines a reference timing positioned near the center of the amplitude of the vibrations in the Z-axis direction, and sets the acquisition timing based on the determined reference timing.

[0119] As a result, captured images for visual feedback control are acquired at timing based on the period of vibration in the Z-axis direction. Therefore, captured images with reduced vibration blur in the Z-axis direction (blur relative to the position when there is no vibration) can be used for visual feedback control. Therefore, even if vibration occurs in the Z-axis direction of the object, visual feedback control can be performed stably and appropriately.

[0120] In the second embodiment and the modified example of the second embodiment, the calibration process may be performed similarly when an additional disturbance vibration occurs in the Z-axis direction and causes a change in the vibration of the object 31. In this case, the image processing unit 121 analyzes the out-of-focus state of the object 31 from the acquired captured image, determines whether or not a change has occurred in the vibration in the Z-axis direction based on the analysis result, and performs the calibration process.

[0121] Specifically, if the image processing unit 121 cannot obtain the center position of the mark 31a from the acquired captured image, it determines that a change has occurred in the vibration in the Z-axis direction and executes calibration processing. Alternatively, the image processing unit 121 may analyze the off-focus amount of the object 31 from the acquired captured image, and if the analyzed off-focus amount is equal to or greater than a predetermined threshold, it may determine that a change has occurred in the vibration in the Z-axis direction and execute calibration processing. In this case, the threshold is set to a value slightly larger than the off-focus amount that would normally occur in the absence of vibration in the Z-axis direction under visual feedback control.

[0122] In the above embodiment and modified example, the period T2 is set so that four captured images are acquired in one vibration cycle (period of period T1), but the period T2 may be set so that a number other than four captured images are acquired in one vibration cycle. However, if the period T2 is set so that three or fewer captured images are acquired in one vibration cycle, there is a risk that the reference timing at which the object 31 is positioned near the center of the vibration amplitude cannot be accurately obtained. From this perspective, it is preferable to set the period T2 so that at least four captured images are acquired in one vibration cycle.

[0123] In the second embodiment and the modified example of the second embodiment, when the deviation of the object 31 from the ideal trajectory in the captured image becomes equal to or greater than a predetermined threshold Dth, it is determined that the vibration of the object 31 has changed and additional disturbance vibration has occurred, but the determination method is not limited to this. For example, it may be determined that additional disturbance vibration has occurred when the cumulative amount of deviations for a predetermined number of consecutive times becomes equal to or greater than a predetermined threshold.

[0124] In the above embodiment and modified examples, an acceleration sensor 14 was used as a detection unit that detects vibrations of the object 31, but instead of the acceleration sensor 14, another detection unit (for example, a TOF sensor) that can detect vibrations of the object 31 may be used.

[0125] In the above embodiment and modified example, as shown in FIG. 3, the image processing unit 121 and the vibration processing unit 124 are provided as separate entities, but the image processing unit 121 and the vibration processing unit 124 may be configured by functions executed by a single microcomputer or by a single FPGA, etc.

[0126] In the above embodiment and modified examples, the position adjustment device 1 is provided with the camera 11, but a camera used for another operation may also be used to acquire images captured by the position adjustment device 1. In this case, the position adjustment device 1 causes this camera to capture images at a specified capturing timing.

[0127] In the above embodiment and modified example, the position adjustment device 1 includes the stage 13 as a control target, but the device that the position adjustment device 1 includes as a control target is not limited to this. The control target of the position adjustment device 1 may also be a camera transport device that transports the field of view of the camera 11 to the position of the characters on the board (target position), etc.

[0128] In the above embodiment and modified example, the stage 13 is an XYθ stage, but is not limited to this and may be a UVW stage.

[0129] In the above embodiment and modified example, in visual feedback control, as described with reference to FIGS. 4 and 5 , the control signal for driving the stage 13 is updated each time a captured image is acquired, based on the current position and target position of the object 31 in the captured image. However, visual feedback control is not limited to this. An initial control signal may be generated based on the initial position and target position of the object 31 in an initial captured image, and the generated initial control signal may be corrected each time a captured image is subsequently acquired based on the difference between the current position and the ideal trajectory. In this case, the ideal trajectory may be set based on the initial position and target position, or may be set based on the immediately preceding position and target position of the object 31.

[0130] The embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical idea defined in the claims.

[0131] (Addendum) The above description of the embodiments discloses the following techniques.

[0132] (Technology 1) a placement unit on which an object is placed; a driving unit that drives the installation unit to change the position of the object; a detection unit that detects vibrations of the object; a vibration processing unit that detects a period of the vibration based on a detection signal from the detection unit; In visual feedback control for moving the object to a target position, a signal generating unit is provided which acquires captured images from a camera that captures an image of the object at an acquisition timing based on the period of the vibration, generates control signals for moving the object to a target position from each of the acquired captured images, and sequentially outputs the generated control signals to the driving unit. A position adjustment device characterized by: According to this technology, captured images for visual feedback control are acquired at timing based on the vibration period. Therefore, captured images with reduced vibration blur (blur relative to the position when there is no vibration) can be used for visual feedback control. Therefore, even if vibration occurs in the target object, visual feedback control can be performed stably and appropriately.

[0133] (Technology 2) In the position adjustment device described in Technology 1, the signal generation unit causes the camera to capture an image at the capture timing to acquire the captured image; A position adjustment device characterized by: This technology limits the timing of camera capture based on the vibration period, preventing blurred images from being captured and processed. This allows for appropriate visual feedback control while reducing power consumption.

[0134] (Technology 3) In the position adjustment device according to Technology 1 or 2, In the calibration process for setting the acquisition timing, The signal generation unit acquiring a plurality of captured images from the camera at a period shorter than the period of the vibration; determining a reference timing at which the object is positioned near the center of amplitude of the vibration from the plurality of captured images; setting the acquisition timing based on the determined reference timing; A position adjustment device characterized by: The timing at which the object is positioned near the center of the vibration amplitude in the imaging area is approximately the same as the timing at which the object would be positioned if there was no vibration blurring of the object. This technology uses this timing as a reference timing and sets the timing for capturing captured images based on the vibration period, thereby enabling sequential capture of captured images similar to those captured without vibration blurring. Therefore, by using these captured images for visual feedback control, visual feedback control can be performed appropriately.

[0135] (Technology 4) In the position adjustment device described in Technical 3, the signal generation unit sets the other period so that at least four captured images are acquired in one period of the vibration. A position adjustment device characterized by: This technology allows smooth and accurate detection of the vibration of an object in the imaging area, and accurately determines the reference timing at which the object is positioned near the center of amplitude, thereby enabling accurate visual feedback control.

[0136] (Technology 5) In the position adjustment device according to technique 3 or 4, the signal generation unit performs the calibration process to set the acquisition timing before starting the visual feedback control. A position adjustment device characterized by: This technology allows subsequent visual feedback control to proceed appropriately and stably.

[0137] (Technology 6) In the position adjustment device described in Technical 5, the signal generation unit executes the calibration process and updates the acquisition timing based on a predetermined condition that may cause a change in the vibration of the object being satisfied after the start of the visual feedback control. A position adjustment device characterized by: This technology allows for smooth response to changes in vibration after the start of visual feedback control, thereby enabling subsequent visual feedback control to proceed appropriately and stably.

[0138] (Technology 7) In the position adjustment device described in Technical 6, The signal generation unit an ideal trajectory for moving the initial position of the object to a target position is estimated from the image captured by the camera; executing the calibration process for updating the acquisition timing, using as the predetermined condition that the position of the object in the captured images acquired from the camera at the predetermined period in the visual feedback control deviates from the ideal trajectory; A position adjustment device characterized by: This technology makes it possible to accurately determine whether the vibration state has changed and to appropriately update the acquisition timing, thereby enabling subsequent visual feedback control to proceed appropriately and stably.

[0139] (Technology 8) In the position adjustment device according to Technology 6 or 7, the signal generation unit acquires the captured image for the calibration process from the camera during a period other than a period of impact vibration caused by the start and end of an acceleration or deceleration operation on the installation unit, and performs the calibration process. A position adjustment device characterized by: This technique makes it possible to prevent captured images that are unstable due to shock vibrations from being used in the calibration process, thereby enabling the acquisition timing to be updated appropriately in the calibration process.

[0140] (Technology 9) In the position adjustment device according to any one of techniques 3 to 8, The signal generation unit an image processing unit that extracts the position of the object and the target position from the captured image; a control signal generating unit that generates the control signal based on the extracted position of the object and the target position, The acquisition of the captured image in the visual feedback control and the calibration processing are performed by the image processing unit. A position adjustment device characterized by: According to this technique, the image processing unit can smoothly perform captured image-related processes, such as acquisition of captured images in visual feedback control and calibration processing. [Explanation of symbols]

[0141] 1 Position adjustment device 11 Camera 12 Signal generation unit 13 Stage (Installation Area) 14 Acceleration sensor (detection part) 31 Object 121 Image processing section 123 Control signal generation unit 124 vibration processing unit 131 Stage servo circuit (drive unit) P0 target position Pd1 and Pd2 periods

Claims

1. a placement unit on which an object is placed; a driving unit that drives the installation unit to change the position of the object; a detection unit that detects vibrations of the object; a vibration processing unit that detects a period of the vibration based on a detection signal from the detection unit; and a signal generating unit that, in visual feedback control for moving the object to a target position, acquires captured images from a camera that captures an image of the object at an acquisition timing based on the period of the vibration, generates control signals for moving the object to a target position from each of the acquired captured images, and sequentially outputs the generated control signals to the driving unit. A position adjustment device characterized by:

2. 2. The position adjustment device according to claim 1, the signal generation unit causes the camera to capture an image at the capture timing to acquire the captured image; A position adjustment device characterized by:

3. 2. The position adjustment device according to claim 1, In the calibration process for setting the acquisition timing, The signal generation unit acquiring a plurality of captured images from the camera at a period shorter than the period of the vibration; determining a reference timing at which the object is positioned near the center of amplitude of the vibration from the plurality of captured images; setting the acquisition timing based on the determined reference timing; A position adjustment device characterized by:

4. 4. The position adjustment device according to claim 3, the signal generation unit sets the other period so that at least four captured images are acquired in one period of the vibration. A position adjustment device characterized by:

5. 4. The position adjustment device according to claim 3, the signal generation unit performs the calibration process to set the acquisition timing before starting the visual feedback control. A position adjustment device characterized by:

6. 6. The position adjustment device according to claim 5, the signal generation unit executes the calibration process and updates the acquisition timing based on a predetermined condition that may cause a change in the vibration of the object being satisfied after the start of the visual feedback control. A position adjustment device characterized by:

7. 7. The position adjustment device according to claim 6, The signal generation unit an ideal trajectory for moving the initial position of the object to a target position is estimated from the image captured by the camera; executing the calibration process for updating the acquisition timing, using as the predetermined condition that the position of the object in the captured images acquired from the camera at the predetermined period in the visual feedback control deviates from the ideal trajectory; A position adjustment device characterized by:

8. 7. The position adjustment device according to claim 6, the signal generation unit acquires the captured image for the calibration process from the camera during a period other than a period of impact vibration caused by the start and end of an acceleration or deceleration operation on the installation unit, and performs the calibration process. A position adjustment device characterized by:

9. 4. The position adjustment device according to claim 3, The signal generation unit an image processing unit that extracts the position of the object and the target position from the captured image; a control signal generating unit that generates the control signal based on the extracted position of the object and the target position, The acquisition of the captured image in the visual feedback control and the calibration processing are performed by the image processing unit. A position adjustment device characterized by:

Images