Three-dimensional measuring device

Abstract

This invention provides a three-dimensional measuring device that can more reliably prevent a decrease in measurement accuracy while extending the lifespan of the light source when using reflective optical modulation elements such as DMDs. [Solution] By controlling the first projection device, the second projection device, and the camera, multiple stripe patterns are projected sequentially and imaged, thereby acquiring multiple image data with different light intensity distributions. In acquiring the image data, after the rise time required for the brightness of the light emitted from the projection devices 4x and 4y to stabilize has elapsed since the start of lighting the light sources of the projection devices 4x and 4y, a phase change lighting process is sequentially performed on each projection device 4x and 4y, in which the phase of the stripe pattern is changed multiple times while the light sources are lit, and then the light sources are turned off. Furthermore, while the light sources are lit and the brightness of the light emitted from them is stable, a continuous imaging process is performed on the camera 5 to capture multiple stripe patterns with different phases.

Description

Technical Field

[0001] The present invention relates to a three-dimensional measurement apparatus that performs three-dimensional measurement using a phase shift method or the like.

Background Art

[0002] Generally, in a substrate manufacturing line for mounting electronic components on a printed circuit board, first, cream solder is printed on the lands of the printed circuit board (solder printing process). Next, the electronic components are temporarily fixed on the printed circuit board based on the viscosity of the cream solder (mounting process). Thereafter, the printed circuit board is led into a reflow furnace, and soldering is performed by heating and melting the cream solder (reflow process).

[0003] In such a substrate manufacturing line, for example, a substrate inspection apparatus for inspecting the printed state of cream solder before component mounting may be provided. Conventionally, various three-dimensional measurement apparatuses using a phase shift method or the like have been proposed as the substrate inspection apparatus.

[0004] The three-dimensional measurement apparatus includes, for example, a projection unit including a light source that emits predetermined light and a grating or the like that converts the light from the light source into a predetermined stripe pattern, and an imaging unit (for example, a CCD camera or the like) disposed directly above the object to be measured. Then, while the stripe pattern is projected from the projection unit onto the object to be measured, the stripe pattern projected onto the object to be measured is imaged by the imaging unit, and the height (Z) at each coordinate (X, Y) of the object to be measured is obtained based on the acquired image data.

[0005] Furthermore, in order to measure three-dimensional shapes with greater accuracy, three-dimensional measuring devices using two or more projection means have been proposed (see, for example, Patent Document 1). The three-dimensional measuring device according to Patent Document 1 has a light source and a grid element, and includes two projection means (projection unit) that move the grid element two or more times and project a striped pattern (grid pattern) onto the object to be measured with each movement, and an imaging means (imaging unit) that captures the striped pattern projected onto the object to be measured and acquires image data. The projection of the striped pattern (imaging is performed at this time) and the phase change of the striped pattern (movement of the grid element) are performed alternately by both projection means, so that the striped pattern from one projection means and the striped pattern from the other projection means are captured alternately.

[0006] Incidentally, in terms of improving measurement accuracy, it is preferable to project a fringe pattern having a sinusoidal light intensity distribution. However, projecting a fringe pattern with an ideal, highly accurate sinusoidal light intensity distribution is extremely difficult.

[0007] Therefore, in order to bring the stripe pattern closer to an ideal sinusoidal light intensity distribution, it is conceivable to use a Digital Micromirror Device (DMD), which can more accurately represent the intermediate tones of the stripe pattern. In a DMD, the duty cycle of each pixel within one frame (e.g., 1 / 60 second) is varied within the range of 0 to 100%, thereby representing light with the desired brightness on a frame-by-frame basis (see Figure 4). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2010-276607 [Overview of the project] [Problems that the invention aims to solve]

[0009] Incidentally, it takes a certain amount of rise time for the brightness of the light emitted from the light source to stabilize, and during this rise time, the brightness of the light emitted from the light source changes. If such a change in brightness occurs during one frame period out of a predetermined number of frames for a given stripe pattern, the brightness of the light represented by each pixel of the DMD on a frame-by-frame basis (gradation according to the duty cycle) may not be properly reflected in the image data acquired by the imaging means, and as a result, there is a risk that the measurement accuracy cannot be sufficiently improved.

[0010] Therefore, it is conceivable to ensure a sufficient rise time to stabilize the brightness of the light emitted from the light source, and to start imaging by the imaging means after the brightness has stabilized. In this case, it is conceivable to continuously illuminate both light sources, or to repeatedly turn both light sources on and off as appropriate, and to alternately image the stripe pattern related to one projection means (first projection device) and the stripe pattern related to the other projection means (second projection device) with the imaging means (camera) (see, for example, Figures 6 and 7). Note that "pattern black" in Figure 6, etc., refers to an optical image in which the entire projection area is black (completely dark), and when "pattern black" is projected, the entire projection area is not illuminated with any light.

[0011] However, to image, for example, four different stripe patterns, continuous illumination requires an illumination time t of approximately 8 frames (= 7 frames + rise time t1 + fall time t2), and even when the illumination is turned on and off as needed, an illumination time t of approximately 8 frames (= 4 × (1 frame + rise time t1 + fall time t2)) is required. Therefore, obtaining multiple different stripe patterns requires keeping the light source on for a long time, which may shorten the lifespan of the light source.

[0012] The present invention has been made in view of the above circumstances, and its purpose is to provide a three-dimensional measuring device that can more reliably prevent a decrease in measurement accuracy related to three-dimensional measurement while extending the lifespan of the light source when a reflective light modulation element such as a DMD is used as the projection means. [Means for solving the problem]

[0013] Below, we will describe, in separate sections, each means suitable for achieving the above objectives. Furthermore, we will add notes on the effects and benefits specific to each means as needed.

[0014] Means 1. A plurality of projection means having a light source that emits predetermined light and a reflective optical modulation element capable of converting the light from the light source into a predetermined stripe pattern, and capable of projecting the stripe pattern onto an object to be measured at a predetermined number of frames per unit time, An imaging means capable of capturing the stripe pattern projected onto the object to be measured, A data acquisition means that controls the projection means and the imaging means and sequentially projects and images multiple stripe patterns with different phases, thereby acquiring multiple image data with different light intensity distributions. A three-dimensional measuring device comprising: an image processing means capable of performing three-dimensional measurement of an object to be measured based on a plurality of image data acquired by the data acquisition means, The reflective optical modulation element has a configuration in which a plurality of pixels are arranged in a two-dimensional array and can be switched between an ON state in which light from the light source is reflected so that it can be projected onto the object to be measured, and an OFF state in which light from the light source is not projected onto the object to be measured, and the stripe pattern can be generated by adjusting the proportion of time that the pixel is in the ON state during one frame period. The data acquisition means is configured to sequentially perform a phase change lighting process on each of the multiple projection means while switching the projection means to be controlled, after a rise time has elapsed from the start of lighting the light source until the brightness of the light emitted from the light source stabilizes, in which the phase of the stripe pattern is changed multiple times while the light source is lit, and then the light source is turned off, and while the light source is lit and the brightness of the light emitted from the light source is stable, the imaging means is configured to perform a continuous imaging process in which multiple stripe patterns with different phases are each captured.

[0015] According to the above-described method 1, imaging by the imaging means is performed after the rise time has elapsed since the start of ignition of the light source, that is, when the brightness of the light emitted from the light source has stabilized, while the phase of the stripe pattern is changed. Therefore, the brightness of the light represented by each pixel of the reflective light modulation element on a frame-by-frame basis (gradation according to the duty cycle) is appropriately reflected in the image data acquired by the imaging means. This makes it possible to more reliably prevent a decrease in the measurement accuracy related to three-dimensional measurement.

[0016] Furthermore, while the light source is lit and the brightness of the light emitted from it is stable, the imaging means continuously captures multiple stripe patterns with different phases. Therefore, compared to the case where the stripe pattern related to one projection means and the stripe patterns related to other projection means are captured alternately, the lighting time of the light source required to capture multiple stripe patterns can be shortened. For example, when capturing four different stripe patterns, the lighting time t of the light source can be set to approximately 5 frames (= 4 frames + rise time t1 + fall time t2) (see Figure 5). This allows for a longer lifespan for the light source.

[0017] Means 2. The three-dimensional measuring apparatus according to Means 1, characterized in that the data acquisition means is configured such that, while the projection means of 1 is performing the phase change lighting process, the projection means that performs the phase change lighting process next to the projection means starts lighting the light source while controlling the reflective light modulation element so that the stripe pattern is not projected onto the object to be measured.

[0018] According to the above-described means 2, while the phase change lighting process is being performed by projection means 1 (i.e., while the light source of said projection means is lit), the light source of the projection means that performs the next phase change lighting process is turned on. Therefore, while the light source of projection means 1 is lit or immediately after it is turned off, the brightness of the light emitted from the light source of the projection means that performs the next phase change lighting process can be stabilized. As a result, immediately after completing the imaging of multiple stripe patterns projected from projection means 1, imaging of stripe patterns projected from another projection means can be started without having to specifically secure a rise time to stabilize the brightness of the light emitted from the light source. Consequently, the speed of three-dimensional measurement processing can be increased.

[0019] Furthermore, the projection means that then performs the phase-shift illumination process starts illuminating the light source while ensuring that no stripe pattern is projected onto the object being measured. Therefore, the image data is not affected by the start of illumination of the light source. This makes it possible to speed up the three-dimensional measurement process while more reliably preventing a decrease in measurement accuracy.

[0020] Means 3. The three-dimensional measuring apparatus according to Means 1, characterized in that the data acquisition means controls the reflective light modulation element of the projection means so that the stripe pattern is not projected onto the object to be measured while the light source of the projection means of Means 1 is turned off, and controls the imaging means to start the continuous imaging process.

[0021] According to the above-described method 3, while the light source in projection means 1 is being turned off, imaging by the imaging means begins. In other words, imaging by the imaging means begins without waiting for the light source in projection means 1 to be turned off. This makes it possible to further speed up the three-dimensional measurement process.

[0022] Also, while the light source is being turned off by the projection means of 1, the reflective light modulation element of the projection means is controlled so that a stripe pattern is not projected onto the object to be measured. As a result, the acquired image data is not affected by starting imaging during the period when the light is off. Consequently, while further speeding up the three-dimensional measurement process, it is possible to more reliably prevent a decrease in measurement accuracy.

[0023] In addition, the technical matters related to each of the above means may be combined as appropriate. Therefore, the technical matters related to the above means 3 may be combined with the technical matters related to the above means 2.

Brief Description of the Drawings

[0024] [Figure 1] It is a schematic configuration diagram schematically showing a substrate inspection apparatus. [Figure 2] It is a block diagram showing the electrical configuration of the substrate inspection apparatus. [Figure 3] It is a partially enlarged plane schematic diagram schematically showing the reflective surface of the DMD. [Figure 4] It is a diagram showing the relationship between the luminance at each pixel and the on-time of the micromirror. [Figure 5] It is a timing chart for explaining the processing operations of each projection device and camera. [Figure 6] It is a timing chart for explaining the processing operations of each projection device and camera that may be considered when alternately imaging the stripe pattern related to one projection means and the stripe pattern related to the other projection means, particularly the processing operations when the light source is continuously lit. [Figure 7] It is a timing chart for explaining the processing operations of each projection device and camera that may be considered when alternately imaging the stripe pattern related to one projection means and the stripe pattern related to the other projection means, particularly the processing operations when the lighting and extinguishing of the light source are repeated.

Embodiments for Carrying Out the Invention

[0025] The following describes one embodiment with reference to the drawings. Figure 1 is a schematic diagram showing the board inspection device 1. In this embodiment, the board inspection device 1 constitutes a "three-dimensional measuring device".

[0026] As shown in Figure 1, the substrate inspection apparatus 1 comprises a mounting table 3, a first projection device 4x, a second projection device 4y, a camera 5, and a control device 6. In this embodiment, the first projection device 4x and the second projection device 4y constitute the "projection means," and the camera 5 constitutes the "imaging means."

[0027] The mounting platform 3 is a platform on which the printed circuit board 2, which is the "object to be measured" and has solder paste printed on it, is placed. The mounting platform 3 is equipped with motors 15 and 16, and these motors 15 and 16 are driven and controlled by the control device 6 so that the printed circuit board 2 placed on the mounting platform 3 slides in any direction (X-axis direction and Y-axis direction).

[0028] The first projection device 4x and the second projection device 4y (hereinafter sometimes simply referred to as "projection devices 4x, 4y") project a predetermined stripe pattern (a light pattern having a sinusoidal light intensity distribution) onto the surface of the printed circuit board 2 from an oblique angle above. The projection devices 4x, 4y are, for example, positioned symmetrically with respect to the center of the mounting base 3.

[0029] The projection device 4x,4y comprises light sources 4xa,4ya that emit predetermined light, and digital micromirror devices (hereinafter referred to as "DMDs") 4xb,4yb that act as "reflective optical modulation elements" that convert the light from the light sources 4xa,4ya into a stripe pattern. The projection device 4x,4y can project an optical image such as a stripe pattern onto the printed circuit board 2 at a predetermined number of frames per unit time (for example, 60 frames per second: 60 FPS).

[0030] In the projection devices 4x and 4y, light emitted from light sources 4xa and 4ya is guided to DMDs 4xb and 4yb via a focusing lens (not shown) or the like. The light is then selectively reflected and modulated at the reflective surfaces of DMDs 4xb and 4yb and guided to projection lenses 4xc and 4yc, where it is projected onto the printed circuit board 2.

[0031] In this embodiment, LED light sources emitting white light are used as light sources 4xa and 4ya. Of course, light sources 4xa and 4ya are not limited to these, and may be lamp light sources, laser light sources, etc. Also, light sources that emit other light, such as near-infrared light, may be used instead of white light. However, it is preferable that light sources 4xa and 4ya have a relatively short rise time required for the brightness of the emitted light to stabilize (for example, a rise time of 10 ms or less).

[0032] The DMD4xb and 4yb used in this embodiment are known. The basic configuration of the DMD4xb and 4yb will be described below with reference to Figure 3. Figure 3 is a schematic partially enlarged plan view illustrating the reflective surface of the DMD4xb and 4yb.

[0033] DMD4xb,4yb is used to convert light from light sources 4xa,4ya into a predetermined stripe pattern, and has a configuration in which a number of planar rectangular micromirrors (movable mirrors) 41, which can be driven and controlled independently of each other, are arranged in a two-dimensional array on a silicon substrate. Each micromirror 41 constitutes one pixel of DMD4xb,4yb.

[0034] Each micromirror 41 is supported so as to be able to swing with its diagonal as the pivot axis 41a, and is tilted by the electrostatic attraction generated when a driving voltage is applied to an electrode (not shown) disposed on its back side.

[0035] Furthermore, by controlling the drive voltage applied to each pixel, each micromirror 41 can selectively switch between an ON state, which is tilted, for example, by +10° with respect to the reference plane of the DMD4xb,4yb, and an OFF state, which is tilted by -10°.

[0036] When light from light sources 4xa and 4ya is incident on the ON-state micromirror 41, the reflected light from the micromirror 41 is incident on the projection lenses 4xc and 4yc, and projected onto the printed circuit board 2 via the projection lenses 4xc and 4yc.

[0037] On the other hand, when light from light sources 4xa and 4ya is incident on the off-state micromirror 41, the reflected light from the micromirror 41 does not enter the projection lenses 4xc and 4yc, but is projected toward a predetermined light absorber (not shown). In other words, no light is projected toward the printed circuit board 2, and black dots are projected onto the printed circuit board 2.

[0038] Furthermore, as shown in Figure 4, the DMD4xb and 4yb perform on / off control at high speed, and by changing the proportion of time each micromirror 41 is in the ON state (duty cycle) during one frame period, for example by pulse width modulation (PWM), it is possible to express grayscale levels of, for example, 256 levels for each pixel.

[0039] Furthermore, by individually driving and controlling each micromirror 41 arranged in a two-dimensional array on the DMD4xb and 4yb using control signals generated based on pre-set projection pattern information, it is possible to project an optical image such as a modulated stripe pattern (a light pattern with a sinusoidal light intensity distribution) onto the printed circuit board 2 according to the projection pattern information.

[0040] Camera 5 consists of a lens, an image sensor, etc., and captures images of the stripe pattern projected onto the printed circuit board 2 (more precisely, the stripe pattern and the printed circuit board 2 on which it is projected). Examples of image sensors include CMOS sensors and CCD sensors.

[0041] Image data captured and acquired by camera 5 is converted into a digital signal within camera 5, input to control device 6 in digital signal form, and stored in image data storage device 24, which will be described later.

[0042] The control device 6 is used to perform various controls, image processing, and calculation processing within the substrate inspection device 1, such as drive control of the projection devices 4x and 4y and the camera 5. Based on the image data acquired by the camera 5, the control device 6 performs image processing and calculation processing as described later.

[0043] The electrical configuration of the control device 6 will now be described. As shown in Figure 2, the control device 6 comprises a CPU and input / output interface 21 (hereinafter referred to as "CPU etc. 21"), an input device 22, a display device 23, an image data storage device 24, a calculation result storage device 25, and a setting data storage device 26. Each of these devices 22 to 26 is electrically connected to the CPU etc. 21.

[0044] The CPU 21 and other components control the entire board inspection apparatus 1 and are responsible for sending and receiving signals with external devices (e.g., projection devices 4x, 4y, etc.). The input device 22 consists of a keyboard, mouse, touch panel, etc., and is used to input information to the control device 6. The display device 23 has a display screen such as a CRT or liquid crystal and displays various information stored in the control device 6.

[0045] The image data storage device 24 stores image data acquired by the camera 5. The calculation result storage device 25 stores various calculation results, such as inspection results. The setting data storage device 26 pre-stores various information, such as design information related to the printed circuit board 2 and projection pattern information related to the stripe patterns generated by the projection devices 4x and 4y.

[0046] Next, the inspection routine performed by the board inspection device 1 for each inspection area of ​​the printed circuit board 2 will be explained in detail with reference to Figure 5. Figure 5 is a timing chart for explaining the processing operation of the projection devices 4x, 4y and camera 5.

[0047] This inspection routine is executed by the control device 6 (CPU, etc. 21). In this embodiment, four image acquisition processes are performed twice for each inspection area. As a result, a total of eight different image data sets with varying light intensity distributions are acquired for each inspection area.

[0048] The control device 6 first drives and controls the motors 15 and 16 to move the printed circuit board 2, and adjusts the field of view (imaging range) of the camera 5 to a predetermined inspection area on the printed circuit board 2. The inspection area is one of the areas in which the surface of the printed circuit board 2 has been pre-divided, with the size of the camera 5's field of view as one unit.

[0049] Next, the control device 6 starts the process of generating one frame's worth of "pattern black" at a predetermined timing based on the clock signal, etc.

[0050] Specifically, the control device 6 controls the projection devices 4x and 4y to perform a process that turns off all pixels (all micromirrors 41) of the DMD 4xb and 4yb for the entire duration of one frame. As a result, regardless of whether the light sources 4xa and 4ya are lit or not, no light is continuously projected onto the printed circuit board 2 from the projection devices 4x and 4y for the entire duration of one frame, resulting in a "black pattern" being projected. In this "black pattern" state, no light is illuminating the entire projection area.

[0051] Then, the control device 6 starts the process of turning on the light source 4xa in the first projection device 4x at a predetermined timing during the projection period of this "pattern black". The timing of the start of the turning on process is set based on the timing of the start of the imaging process of the stripe pattern projected from the first projection device 4x and the rise time t1 required for the brightness of the light emitted from the light source 4xa to stabilize. Note that the rise time t1 may vary depending on the light sources 4xa and 4ya used.

[0052] After the rise time t1 has elapsed, the control device 6 changes the phase of the stripe pattern projected from the first projection device 4x onto the printed circuit board 2, and uses the camera 5 to capture images of multiple (four in this embodiment) stripe patterns with different phases. Therefore, the generation of the stripe pattern and the imaging by the camera 5 are performed after the rise time t1 has elapsed and the brightness of the light emitted from the light source 4xa has stabilized.

[0053] To explain in detail the generation of the stripe pattern and imaging by the camera 5, the control device 6 first executes the first stripe pattern generation process related to the first projection device 4x. In this process, by driving and controlling the DMD 4xb, the generation process of the first stripe pattern (pattern 1 with a phase of "0°") out of four different stripe patterns with different phases is executed for a predetermined number of frames (1 frame in the example of Figure 5). As a result, the first stripe pattern related to the first projection device 4x is projected onto the printed circuit board 2 for a predetermined number of frames.

[0054] Furthermore, the control device 6 drives the camera 5 in accordance with the projection of the first stripe pattern by the first projection device 4x, thereby starting the first imaging process (exposure process) by the first projection device 4x. While the first stripe pattern is being projected by the first projection device 4x, the first imaging process (imaging X1) by the camera 5 continues to be executed. The image data acquired by the camera 5 is transferred to and stored in the image data storage device 24 after the completion of each imaging process.

[0055] Next, after the completion of the first fringe pattern projection period (fringe pattern generation process), the control device 6 executes the second fringe pattern generation process for the first imaging device 4x. Specifically, it drives and controls the DMD 4xb to execute the generation process of the second fringe pattern (pattern 2 with a phase of "90°") for the first projection device 4x for a predetermined number of frames (1 frame in the example of Figure 5). As a result, the second fringe pattern for the first projection device 4x is projected onto the printed circuit board 2 for a predetermined number of frames.

[0056] The control device 6 then drives the camera 5 in accordance with the projection of the second stripe pattern by the first projection device 4x, thereby starting the second imaging process (exposure process) for the first projection device 4x. While the second stripe pattern is being projected, the second imaging process (imaging X2) by the camera 5 continues to be performed.

[0057] Furthermore, after the completion of the second stripe pattern projection period (stripe pattern generation process), the control device 6 executes the third stripe pattern generation process related to the first projection device 4x, and simultaneously performs the third imaging process (imaging X3) by the camera 5 in conjunction with the projection of the stripe pattern (pattern 3 with a phase of "180°"). After the completion of the third stripe pattern projection period (stripe pattern generation process), the control device 6 executes the fourth stripe pattern generation process related to the first projection device 4x, and simultaneously performs the fourth imaging process (imaging X4) by the camera 5 in conjunction with the projection of the stripe pattern (pattern 4 with a phase of "270°"). The light source 4xa remains lit while each stripe pattern is being imaged.

[0058] Furthermore, once the camera 5 has finished imaging the fourth stripe pattern, the control device 6 starts the process of turning off the light source 4xa related to the first projection device 4x. At this time, while the light source 4xa is being turned off, that is, during the fall time t2, the control device 6 performs a process to turn off all pixels of the DMD 4xb so that the stripe pattern is not projected onto the printed circuit board 2, resulting in a state where "black pattern" is projected.

[0059] Thus, the control device 6 causes the first projection device 4x to perform a phase change lighting process after a rise time t1 has elapsed, which is required from the start of lighting the light source 4xa until the brightness of the light emitted from the light source 4xa stabilizes. This process involves changing the phase of the stripe pattern four times while the light source 4xa is lit, and then turning off the light source 4xa. Furthermore, while the light source 4xa is lit and the brightness of the light emitted from the light source 4xa is stable, the control device 6 causes the camera 5 to perform a continuous imaging process, which involves continuously imaging four different stripe patterns with different phases.

[0060] Furthermore, while the camera 5 is capturing the fourth stripe pattern, that is, while the first projection device 4x is performing the phase change lighting process, the control device 6 starts the lighting process of the light source 4ya in the second projection device 4y. At this time, the control device 6 controls the DMD 4yb so that all pixels are turned off, so that the stripe pattern related to the second projection device 4y is not projected onto the printed circuit board 2. The timing of the start of the lighting process of the light source 4ya is set based on the start timing of the stripe pattern capturing process related to the second projection device 4y and the rise time t1 required for the brightness of the light emitted from the light source 4ya to stabilize.

[0061] Then, after the rise time t1 for the second projection device 4y has elapsed, the control device 6 changes the phase of the stripe pattern projected from the second projection device 4y onto the printed circuit board 2, and uses the camera 5 to capture images of four different stripe patterns with different phases.

[0062] Here, the generation of the stripe pattern by the second projection device 4y and the imaging by the camera 5 are started while the light source 4xa of the first projection device 4x is being turned off. In other words, the continuous imaging process for capturing the stripe pattern by the second projection device 4y is started while the light source 4xa of the first projection device 4x is being turned off (fall time t2 for the first projection device 4x). Furthermore, the generation of the stripe pattern by the second projection device 4y and the imaging by the camera 5 are performed after the rise time t1 for the second projection device 4y has elapsed and when the brightness of the light emitted from the light source 4ya has stabilized.

[0063] The imaging of the stripe pattern by the second projection device 4y is performed in the same manner as the imaging of the stripe pattern by the first projection device 4x. That is, the control device 6 controls the second projection device 4y (particularly DMD4yb) to sequentially project the first, second, third, and fourth stripe patterns (stripe patterns with phases "0°", "90°", "180°", and "270°") onto the printed circuit board 2. The control device 6 then controls the camera 5 to perform one imaging process (imaging Y1, imaging Y2, imaging Y3, and imaging Y4) for each stripe pattern. As a result, four different stripe patterns are sequentially imaged. When the imaging process for the fourth stripe pattern by the camera 5 is completed, the control device 6 turns off the light source 4ya.

[0064] Therefore, the control device 6, in the same manner as when imaging the stripe pattern related to the first projection device 4x, causes the second projection device 4y to perform a phase change lighting process, which involves changing the phase of the stripe pattern four times while the light source 4ya is lit, after the rise time t1 required for the brightness of the light emitted from the light source 4ya to stabilize, has elapsed, and then the light source 4ya is turned off. In addition, the control device 6 causes the camera 5 to perform a continuous imaging process, which involves imaging four different stripe patterns with different phases, while the light source 4ya is lit and the brightness of the light emitted from the light source 4ya is stable.

[0065] In this manner, the control device 6 switches between the controlled projection devices 4x and 4y, sequentially executing phase-change lighting processing on each of these projection devices 4x and 4y, and when the brightness of the light emitted from the light sources 4xa and 4ya is stable, it causes the camera 5 to execute continuous imaging processing. In this embodiment, the control device 6, which controls the projection devices 4x and 4y and the camera 5, sequentially projects and images eight (=4×2) different stripe patterns with different phases, thereby acquiring multiple image data with different light intensity distributions, constitutes the "data acquisition means".

[0066] Next, the control device 6 performs three-dimensional measurement (height measurement) using a known phase shift method based on the eight types of image data (luminance values ​​of each pixel) acquired as described above, and stores the measurement results in the calculation result storage device 25. In this embodiment, the control device 6 that performs three-dimensional measurement of the printed circuit board 2 based on multiple image data constitutes the "image processing means".

[0067] Next, the control device 6 performs quality determination processing on the solder paste based on the three-dimensional measurement results (height data at each coordinate). Specifically, based on the measurement results of the inspection area obtained as described above, the control device 6 detects the printed area of ​​the solder paste that is higher than the reference plane, and calculates the amount of printed solder paste by integrating the height of each part within this area.

[0068] Next, the control device 6 compares the calculated data, such as the amount of solder paste, with reference data (such as Gerber data) stored in the pre-set data storage device 26, and determines whether the solder paste printing in the inspection area is of good or bad quality based on whether the comparison result falls within an acceptable range.

[0069] While this process is being carried out, the control device 6 drives and controls the motors 15 and 16 to move the printed circuit board 2 to the next inspection area, and thereafter, the above series of processes is repeated in all inspection areas until the inspection of the entire printed circuit board 2 is completed.

[0070] As detailed above, according to this embodiment, after the rise time t1 has elapsed since the start of lighting the light sources 4xa and 4ya, that is, when the brightness of the light emitted from the light sources 4xa and 4ya has stabilized, the phase of the stripe pattern is changed and imaging is performed by the camera 5. Therefore, the brightness of the light represented by each pixel of the DMD 4xb and 4yb on a frame-by-frame basis (gradation according to the duty cycle) is appropriately reflected in the image data acquired by the camera 5. This makes it possible to more reliably prevent a decrease in measurement accuracy related to three-dimensional measurement.

[0071] Furthermore, while the light sources 4xa and 4ya are lit and the brightness of the light emitted from them is stable, the camera 5 continuously captures four different stripe patterns with different phases. Therefore, compared to the case where the stripe pattern related to the first projection device 4x and the stripe pattern related to the second projection device 4y are captured alternately, the lighting time of the light sources 4xa and 4ya required to capture the four different stripe patterns can be shortened. In other words, in this embodiment, when capturing the four different stripe patterns, the lighting time t of the light sources 4xa and 4ya can be set to approximately 5 frames (= 4 frames + rise time t1 + fall time t2) (see Figure 5). This makes it possible to extend the lifespan of the light sources 4xa and 4ya.

[0072] Furthermore, while the phase-shift lighting process is being performed by the first projection device 4x (i.e., while the light source 4xa of the first projection device 4x is lit), the light source 4ya of the second projection device 4y is started to light up. Therefore, while the light source 4xa of the first projection device 4x is lit or immediately after it is turned off, the brightness of the light emitted from the light source 4ya of the second projection device 4y, which then performs the phase-shift lighting process, can be stabilized. As a result, immediately after completing the imaging of the four different stripe patterns projected from the first projection device 4x, imaging of the stripe patterns projected from the second projection device 4y can be started without having to specifically secure a rise time t1 to stabilize the brightness of the light emitted from the light source 4ya. Consequently, the speed of the three-dimensional measurement process can be increased.

[0073] In addition, the second projection device 4y turns off each pixel of the DMD4yb, preventing the projection of the stripe pattern onto the printed circuit board 2, while simultaneously starting to light up the light source 4ya. Therefore, the start of lighting up the light source 4ya does not affect the image data (image data related to the stripe pattern projected from the first projection device 4x). This allows for faster three-dimensional measurement processing while more reliably preventing a decrease in measurement accuracy.

[0074] Furthermore, while the light source 4xa in the first projection device 4x is being switched off, imaging by camera 5 begins. In other words, without waiting for the light source 4xa in the first projection device 4x to be switched off, imaging by camera 5 to capture the stripe pattern related to the second projection device 4y begins. This makes it possible to further speed up the three-dimensional measurement process.

[0075] Furthermore, while the light source 4xa of the first projection device 4x is switched off, the DMD 4xb of the first projection device 4x is controlled so that the stripe pattern is not projected onto the printed circuit board 2. This prevents the acquired image data (image data related to the stripe pattern projected from the second projection device 4y) from being affected by the start of imaging while the light source is switched off. As a result, it is possible to further speed up the three-dimensional measurement processing while more reliably preventing a decrease in measurement accuracy.

[0076] Furthermore, the embodiment is not limited to the description above, and may be implemented as follows, for example. Of course, other applications and modifications not exemplified below are also possible.

[0077] (a) In the above embodiment, the substrate inspection apparatus 1 is equipped with two projection devices 4x and 4y, but it may be equipped with three or more projection devices. In this case as well, the control device 5 switches the projection device to be controlled and sequentially executes the phase change lighting process on each of these projection devices, and when the brightness of the light emitted from the light source is stable, it executes the continuous imaging process on the camera 5.

[0078] (b) In the above embodiment, the three-dimensional measuring device is implemented as a substrate inspection device 1 that inspects the printing condition of solder paste printed on the printed circuit board 2. However, it is not limited to this, and may be implemented in a configuration that measures other objects, such as adhesive applied to the printed circuit board, electronic components mounted on the printed circuit board, or solder bumps formed on a wafer substrate. Furthermore, the object to be measured may be something other than the printed circuit board 2.

[0079] (c) In the above embodiment, each projection device 4x,4y is configured to project four different stripe patterns with phases differing by 90°, but the number of phase shifts and the amount of phase shift are not limited to these, and other number of phase shifts and amounts of phase shift that can be measured in three dimensions by the phase shift method may be adopted. Accordingly, the projection devices 4x,4y may project three different stripe patterns with phases differing by 120°, or two different stripe patterns with phases differing by 180°.

[0080] (d) In the above embodiment, three-dimensional measurement is performed using the phase shift method, but the system is not limited to this, and other pattern projection methods (three-dimensional measurement methods), such as the spatial coding method, may be used. However, when measuring small objects such as solder paste, it is more preferable to use a measurement method with high measurement accuracy, such as the phase shift method.

[0081] (e) The configuration of the circuit board inspection apparatus 1 is not limited to the above embodiment. For example, in the above embodiment, the motors 15 and 16 are driven and controlled to move the printed circuit board 2, and the field of view (imaging range) of the camera 5 is adjusted to a predetermined inspection area on the printed circuit board 2. However, it is not limited to this, and for example, the inspection head consisting of projection devices 4x and 4y and camera 5 may be moved with the printed circuit board 2 fixed in place to adjust to a predetermined inspection area on the printed circuit board 2.

[0082] (e) The configuration of the projection devices 4x and 4y is not limited to the above embodiment. For example, in the above embodiment, DMD4xb and 4yb are used as "reflective optical modulation elements," but other elements such as reflective liquid crystal elements (LCOS: Liquid Crystal On Silicon) may be used instead.

[0083] Furthermore, the number of pixels, number of grayscale levels, frame rate, two-dimensional array configuration of the micromirrors 41, orientation of the pivot axis 41a of the micromirrors 41, and tilt angle of the micromirrors 41 related to the DMD4xb,4yb are not limited to the above embodiment, and other configurations may be adopted.

[0084] Furthermore, in the above embodiment, pulse width modulation (PWM) is exemplified as a method for changing the proportion of time (duty cycle) that each micromirror 41 in DMD4xb,4yb is ON during one frame period. However, the method is not limited to this, and for example, pulse density modulation (PDM) or the like, which adjusts the number of times each micromirror 41 is ON during one frame period, may also be employed. [Explanation of Symbols]

[0085] 1... Circuit board inspection device (three-dimensional measuring device), 2... Printed circuit board (object to be measured), 4x... First projection device (projection means), 4xa... Light source, 4xb... DMD (reflective optical modulation element), 4y... Second projection device (projection means), 4ya... Light source, 4yb... DMD (reflective optical modulation element), 5... Camera (imaging means), 6... Control device (data acquisition means, image processing means).

Claims

1. A light source that emits a predetermined light and a reflective optical modulation element capable of converting the light from the light source into a predetermined stripe pattern, and a plurality of projection means capable of projecting the stripe pattern onto an object to be measured at a predetermined number of frames per unit time, An imaging means capable of capturing the stripe pattern projected onto the object to be measured, A data acquisition means that controls the projection means and the imaging means and sequentially projects and images multiple stripe patterns with different phases, thereby acquiring multiple image data with different light intensity distributions. A three-dimensional measuring device comprising: an image processing means capable of performing three-dimensional measurement of an object to be measured based on a plurality of image data acquired by the data acquisition means, The reflective optical modulation element has a configuration in which a plurality of pixels are arranged in a two-dimensional array and can be switched between an ON state in which light from the light source is reflected so that it can be projected onto the object to be measured, and an OFF state in which light from the light source is not projected onto the object to be measured, and the stripe pattern can be generated by adjusting the proportion of time that the pixel is in the ON state during one frame period. The data acquisition means is configured to sequentially perform a phase change lighting process on each of the multiple projection means while switching the projection means to be controlled, after a rise time has elapsed from the start of lighting the light source until the brightness of the light emitted from the light source stabilizes, in which the phase of the stripe pattern is changed multiple times while the light source is lit, and then the light source is turned off, and while the light source is lit and the brightness of the light emitted from the light source is stable, the imaging means is configured to perform a continuous imaging process in which multiple stripe patterns with different phases are each captured.

2. The three-dimensional measuring apparatus according to claim 1, characterized in that the data acquisition means is configured to start lighting the light source while the projection means 1 is performing the phase change lighting process, and the projection means that performs the phase change lighting process after the projection means starts lighting the light source while controlling the reflective light modulation element so that the stripe pattern is not projected onto the object to be measured.

3. The three-dimensional measuring apparatus according to claim 1, characterized in that the data acquisition means is configured to control the reflective light modulation element of the projection means so that the stripe pattern is not projected onto the object to be measured while the light source is being turned off by the projection means of claim 1, and at the same time to control the imaging means to start the continuous imaging process.

Images