3D measuring device

Abstract

A three-dimensional measurement device is provided that can more reliably prevent a decrease in measurement accuracy and extend the life of a light source when using a reflective light modulation element such as a DMD. [Solution] A first projection device, a second projection device, and a camera are controlled to sequentially project and capture a plurality of stripe patterns, thereby acquiring a plurality of image data sets with different light intensity distributions. To acquire the image data, after the light sources of the projection devices 4x and 4y are turned on and a rise time has elapsed, which is required for the brightness of the light emitted from the light sources to stabilize, a phase-change lighting process is executed sequentially in each of the projection devices 4x and 4y, in which the phase of the stripe pattern is changed multiple times while the light sources are turned on and the brightness of the light emitted from the light sources is stable. Furthermore, while the light sources are turned on and the brightness of the light emitted from the light sources is stable, a continuous imaging process is executed in the camera 5, in which a plurality of stripe patterns with different phases are respectively captured.

Description

[Technical Field]

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

[0002] Generally, in a circuit board manufacturing line where electronic components are mounted on a printed circuit board, cream solder is first printed on the lands of the printed circuit board (solder printing process). Next, the electronic components are temporarily attached to the printed circuit board using the viscosity of the cream solder (mounting process). After that, the printed circuit board is introduced into a reflow furnace, where the cream solder is heated and melted to perform soldering (reflow process).

[0003] In such a circuit board manufacturing line, a circuit board inspection device is sometimes installed to inspect, for example, the printing condition of cream solder before component mounting. Conventionally, various three-dimensional measurement devices using the phase shift method and the like have been proposed as circuit board inspection devices.

[0004] The three-dimensional measuring device includes, for example, a projection means consisting of a light source that emits a predetermined light and a grating that converts the light from the light source into a predetermined stripe pattern, and an imaging means (for example, a CCD camera) that is placed directly above the object to be measured. Then, with the stripe pattern projected onto the object to be measured projected from the projection means, the imaging means captures an image of the stripe pattern projected onto the object to be measured, and obtains the height (Z) of the object at each coordinate (X, Y) based on the obtained image data.

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

[0006] In terms of improving measurement accuracy, it is preferable to project a stripe pattern having a sinusoidal light intensity distribution. However, it is extremely difficult to project a stripe pattern having an ideal sinusoidal light intensity distribution with high accuracy.

[0007] Therefore, in order to make the stripe pattern closer to an ideal sinusoidal light intensity distribution, it is possible to use a digital micromirror device (DMD), which can more accurately express the gray scale of the stripe pattern. A DMD expresses light with the desired brightness on a frame-by-frame basis by changing the duty ratio of each pixel within a range of 0 to 100% during one frame (e.g., 1 / 60 seconds) (see Figure 4). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-276607 Summary of the Invention [Problem to be solved by the invention]

[0009] However, it takes a certain amount of 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 the projection period of a predetermined number of frames related to a predetermined stripe pattern, the brightness of the light (grayscale according to the duty ratio) expressed by each pixel of the DMD on a frame-by-frame basis will not be properly reflected in the image data acquired by the imaging means, and as a result, there is a risk that measurement accuracy will not be sufficiently improved.

[0010] Therefore, it is conceivable to ensure sufficient rise time for stabilizing the brightness of the light emitted from the light source and to start capturing images using the capturing means once the brightness has stabilized. In this case, it is conceivable to alternately capture images of the stripe pattern associated with one projection means (first projection device) and the stripe pattern associated with the other projection means (second projection device) using the capturing means (camera) while continuously lighting both light sources or repeatedly turning on and off both light sources as appropriate (see, for example, Figures 6 and 7). Note that the "black pattern" in Figure 6 etc. refers to an optical image in which the entire projection area is black (completely dark), and when the "black pattern" is projected, no light is irradiated onto the entire projection area.

[0011] However, to capture, for example, four different stripe patterns, a lighting time t of about 8 frames (= 7 frames + rise time t1 + fall time t2) is required in the case of continuous lighting, and even if the light is turned on and off repeatedly as appropriate, a lighting time t of about 8 frames [= 4 × (1 frame + rise time t1 + fall time t2)] is required. Therefore, to capture multiple different stripe patterns, the light source needs to be turned on for a long time, which may shorten the life 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 measurement device that can more reliably prevent a decrease in measurement accuracy related to three-dimensional measurement while extending the life 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] The following describes each of the means suitable for achieving the above object, with specific effects of the corresponding means added as necessary.

[0014] Means 1: A plurality of projection means each having a light source that emits a predetermined light and a reflective light modulation element that can convert 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 imaging the stripe pattern projected onto the object to be measured; a data acquisition means for controlling the projection means and the imaging means to sequentially project and capture a plurality of stripe patterns having different phases, thereby acquiring a plurality of image data having different light intensity distributions; a three-dimensional measuring apparatus including an image processing means capable of performing three-dimensional measurement of the object to be measured based on a plurality of image data acquired by the data acquisition means, the reflective light modulation element has a configuration in which a plurality of pixels are two-dimensionally arranged and switchable between an ON state in which the 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 the light from the light source is not projected onto the object to be measured, and is configured to be able to generate the stripe pattern by adjusting the ratio of the time in which the pixel is in the ON state during one frame period for each pixel; the data acquisition means is configured to sequentially execute, on each of the plurality of projection means while switching among the projection means to be controlled, a phase change lighting process in which, after a rise time required for the brightness of the light emitted from the light source to stabilize has elapsed since the lighting of the light source was started, the phase of the stripe pattern is changed a plurality of times while the light source is still turned on, and then the light source is turned off, and to cause the imaging means to execute a continuous imaging process in which, while the light source is turned on and the brightness of the light emitted from the light source is stable, each of the plurality of stripe patterns with different phases is imaged.

[0015] According to the above-mentioned means 1, after the rise time has elapsed since the light source started to be turned on, that is, when the brightness of the light emitted from the light source is stable, the imaging means captures an image while changing the phase of the stripe pattern. Therefore, the brightness of the light (gradation according to the duty ratio) expressed by each pixel of the reflective light modulation element on a frame-by-frame basis 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 of three-dimensional measurement.

[0016] Furthermore, when the light source is on and the brightness of the light emitted from the light source is stable, the imaging means successively captures multiple stripe patterns with different phases. Therefore, compared to alternately capturing a stripe pattern associated with one projection means and a stripe pattern associated with another projection means, the light source illumination time required to capture multiple stripe patterns can be shortened. For example, to capture four stripe patterns, the illumination time t of the light source can be set to approximately five frames (= 4 frames + rise time t1 + fall time t2) (see FIG. 5). This allows for a longer life of the light source.

[0017] Means 2: The three-dimensional measuring device described in Means 1, characterized in that the data acquisition means is configured to, while the phase change lighting process is being executed by the projection means of Means 1, start lighting the light source by the projection means that performs the phase change lighting process next to the projection means 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-mentioned means 2, while a first projection means is executing a phase change lighting process (i.e., while the light source of the projection means is on), the light source of the projection means that performs the phase change lighting process next after the first projection means starts to light up. Therefore, while the light source of the first projection means is on or immediately after it is turned off, the brightness of the light emitted from the light source of the projection means that performs the phase change lighting process next can be stabilized. As a result, immediately after completing the imaging of multiple stripe patterns projected from one projection means, it is possible to start imaging of a stripe pattern projected from another projection means without having to ensure a specific rise time for stabilizing the brightness of the light emitted from the light source. As a result, the speed of the three-dimensional measurement process can be increased.

[0019] Next, the projection means, which performs the phase change lighting process, starts lighting the light source while preventing a stripe pattern from being projected onto the object to be measured. Therefore, the image data is not affected by the start of lighting 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 device described in Means 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 of the projection means of 1 is turned off, while controlling the imaging means so as to start the continuous imaging process.

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

[0022] Furthermore, while the light source of the projection means 1 is turned off, 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. This prevents the image data to be acquired from being affected by starting to capture images while the light source is turned off. As a result, it is possible to further speed up the three-dimensional measurement process while more reliably preventing a decrease in measurement accuracy.

[0023] The technical matters relating to the above means may be combined as appropriate. Therefore, the technical matters relating to the above means 2 may be combined with the technical matters relating to the above means 3. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram illustrating a substrate inspection device. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the substrate inspection device. [Figure 3] FIG. 2 is a partially enlarged schematic plan view showing a reflective surface of a DMD. [Figure 4] FIG. 10 is a diagram showing the relationship between the brightness of each pixel and the on-time of the micromirror. [Figure 5] 4 is a timing chart for explaining the processing operations of each projection device and camera. [Figure 6] This is a timing chart to explain the processing operations of each projection means and camera that can be considered when alternately capturing a stripe pattern related to one projection means and a stripe pattern related to the other projection means, particularly when the light source is continuously lit. [Figure 7] This is a timing chart to explain the processing operations of each projection means and camera that can be considered when alternately capturing a stripe pattern related to one projection means and a stripe pattern related to the other projection means, particularly when the light source is repeatedly turned on and off. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a substrate inspection device 1. In this embodiment, the substrate inspection device 1 constitutes a "three-dimensional measurement device."

[0026] 1, the substrate inspection apparatus 1 includes 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 each constitute a "projection means," and the camera 5 constitutes an "imaging means."

[0027] The mounting table 3 is a table for placing a printed circuit board 2 as an "object to be measured" on which cream solder is printed as a measurement target. The mounting table 3 is provided with motors 15 and 16, and the motors 15 and 16 are driven and controlled by the control device 6 so that the printed circuit board 2 placed on the mounting table 3 can slide 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) from diagonally above onto the surface of the printed circuit board 2. The projection devices 4x, 4y are provided, for example, at symmetrical positions with respect to the center of the mounting table 3.

[0029] The projection devices 4x and 4y include light sources 4xa and 4ya that emit predetermined light, and digital micromirror devices (hereinafter referred to as "DMDs") 4xb and 4yb that function as "reflective light modulation elements" that convert the light from the light sources 4xa and 4ya into a stripe pattern. The projection devices 4x and 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 (e.g., 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 condenser lenses (not shown) etc. Then, the light that is selectively reflected and modulated by the reflective surfaces of the DMDs 4xb and 4yb is guided to projection lenses 4xc and 4yc, where it is projected onto the printed circuit board 2 via the projection lenses 4xc and 4yc.

[0031] In this embodiment, LED light sources that emit white light are used as the light sources 4xa and 4ya. Of course, the light sources 4xa and 4ya are not limited to this, and may be, for example, lamp light sources or laser light sources. Furthermore, light sources that emit other light sources, such as near-infrared light, may also be used. However, it is preferable that the 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 DMDs 4xb and 4yb used in this embodiment are known. The basic configuration of the DMDs 4xb and 4yb will be described below with reference to Fig. 3. Fig. 3 is a partially enlarged plan view schematically showing the reflecting surfaces of the DMDs 4xb and 4yb.

[0033] The DMDs 4xb and 4yb are used to convert light from light sources 4xa and 4ya into a predetermined stripe pattern, and are configured with a large number of independently driveable, rectangular micromirrors (movable mirrors) 41 arranged two-dimensionally on a silicon substrate. Each micromirror 41 constitutes one pixel of the DMDs 4xb and 4yb.

[0034] Each micromirror 41 is supported so that it can oscillate around one of its diagonal lines as an oscillation axis 41a, and is tilted by electrostatic attraction generated when a drive voltage is applied to an electrode (not shown) disposed on the back side of the micromirror.

[0035] By controlling the drive voltage applied to each pixel, each micromirror 41 can be switched alternatively between an on state in which it is tilted, for example, by +10° relative to the reference plane of DMD 4xb, 4yb, and an off state in which it is tilted by -10°.

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

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

[0038] As shown in FIG. 4, the DMDs 4xb and 4yb perform high-speed on / off control, and by changing the proportion of time each micromirror 41 is in the on state (duty ratio) during one frame period using, for example, pulse width modulation (PWM), it is possible to express, for example, 256 levels of gradation for each pixel.

[0039] Then, by individually driving and controlling each micromirror 41 arranged two-dimensionally on the DMDs 4xb and 4yb using control signals generated based on preset projection pattern information, it is possible to project an optical image such as a stripe pattern (a light pattern having a sinusoidal light intensity distribution) modulated according to the projection pattern information onto the printed circuit board 2.

[0040] The camera 5 is composed of a lens, an imaging element, etc., and captures an image of the stripe pattern (more precisely, the stripe pattern and the printed circuit board 2 onto which it is projected) projected onto the printed circuit board 2. Examples of the imaging element include a CMOS sensor and a CCD sensor.

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

[0042] The control device 6 is used to perform various controls, image processing, and arithmetic 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, arithmetic processing, and the like, which will be described later.

[0043] Here, we will explain the electrical configuration of the control device 6. As shown in Fig. 2, the control device 6 includes 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. These devices 22 to 26 are electrically connected to the CPU etc. 21.

[0044] The CPU 21 and other components are responsible for overall control of the substrate inspection apparatus 1, as well as for transmitting and receiving signals to and from external devices (for example, the projection devices 4x, 4y, etc.). The input device 22 is composed 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 LCD, and displays various information stored in the control device 6.

[0045] The image data storage device 24 stores image data captured by the camera 5. The calculation result storage device 25 stores various calculation results such as inspection results. The setting data storage device 26 stores in advance 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, an inspection routine performed by the board inspection apparatus 1 for each inspection area of ​​the printed board 2 will be described in detail with reference to Fig. 5. Fig. 5 is a timing chart for explaining the processing operations of the projection devices 4x, 4y and the 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 sets of image data with different light intensity distributions are acquired for each inspection area.

[0048] The control device 6 first controls the driving of the motors 15 and 16 to move the printed circuit board 2, and aligns the field of view (imaging range) of the camera 5 with a predetermined inspection area on the printed circuit board 2. The inspection area is one of the areas into which the surface of the printed circuit board 2 is divided in advance, with the size of the field of view of the camera 5 being one unit.

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

[0050] Specifically, the control device 6 controls the projection devices 4x and 4y to execute processing to turn off all pixels (all micromirrors 41) of the DMDs 4xb and 4yb for the entire period of one frame. As a result, regardless of whether the light sources 4xa and 4ya are lit or not, light is not continuously projected from the projection devices 4x and 4y onto the printed circuit board 2 for the entire period of one frame, and a "black pattern" is projected. When the "black pattern" is projected, no light is irradiated onto the entire projection area.

[0051] The control device 6 then starts the lighting process of the light source 4xa of the first projection device 4x at a predetermined timing during the projection period of this "pattern black." The start timing of the lighting process is set based on the start timing 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 source 4xa, 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 causes the camera 5 to capture images of multiple stripe patterns with different phases (four in this embodiment). Therefore, the generation of the stripe pattern and the capture 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 specifically explain the generation of stripe patterns and the capturing of images by the camera 5, the control device 6 first executes a first stripe pattern generation process for the first projection device 4x. In this process, the control device 6 drives and controls the DMD 4xb to execute a process for generating the first of four stripe patterns with different phases (pattern 1 with a phase of 0°) for a predetermined number of frames (one frame in the example of FIG. 5). As a result, the first stripe pattern for the first projection device 4x is projected onto the printed circuit board 2 for the predetermined number of frames.

[0054] Furthermore, the control device 6 controls the driving of the camera 5 in synchronization 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. Note that the image data acquired by imaging by the camera 5 is transferred to and stored in the image data storage device 24 after each imaging process is completed.

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

[0056] Then, the control device 6 starts the second imaging process (exposure process) for the first projection device 4x by controlling the driving of the camera 5 in synchronization with the projection of the second stripe pattern by 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 executed.

[0057] Furthermore, after the second stripe pattern projection period (stripe pattern generation process) is completed, the control device 6 executes a third stripe pattern generation process for the first projection device 4x, and executes a third imaging process (imaging X3) by the camera 5 in accordance with the projection of the stripe pattern (pattern 3 with a phase of 180°). Furthermore, after the third stripe pattern projection period (stripe pattern generation process) is completed, the control device 6 executes a fourth stripe pattern generation process for the first projection device 4x, and executes a fourth imaging process (imaging X4) by the camera 5 in accordance with the projection of the stripe pattern (pattern 4 with a phase of 270°). Note that the light source 4xa remains lit while each stripe pattern is being imaged.

[0058] Furthermore, when the image capturing process of the fourth stripe pattern by the camera 5 is completed, the control device 6 starts the process of turning off the light source 4xa of 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 executes the process of turning 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 in which the "black pattern" is projected.

[0059] In this way, after the rise time t1 required for the luminance of the light emitted from the light source 4xa to stabilize has elapsed since the light source 4xa was turned on, the control device 6 causes the first projection device 4x to execute a phase change lighting process in which the phase of the stripe pattern is changed four times while the light source 4xa is turned on and then the light source 4xa is turned off. Furthermore, the control device 6 causes the camera 5 to execute a continuous imaging process in which, while the light source 4xa is turned on and the luminance of the light emitted from the light source 4xa is stable, four different stripe patterns with different phases are successively captured.

[0060] Furthermore, while the camera 5 is capturing the image of the fourth stripe pattern, i.e., while the first projection device 4x is executing 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 to turn off all pixels so that the stripe pattern related to the second projection device 4y is not projected onto the printed circuit board 2. The start timing of the lighting process of the light source 4ya is set based on the start timing of the imaging process of the stripe pattern 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 causes the camera 5 to capture four stripe patterns with different phases.

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

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

[0064] Therefore, similarly to when capturing an image of the stripe pattern associated with the first projection device 4x, the control device 6 causes the second projection device 4y to execute a phase-changing lighting process in which, after the start of lighting of the light source 4ya and the rise time t1 required for the brightness of the light emitted from the light source 4ya to stabilize has elapsed, the phase of the stripe pattern is changed four times while the light source 4ya is still on, and then the light source 4ya is turned off. Furthermore, the control device 6 causes the camera 5 to execute a continuous imaging process in which, while the light source 4ya is on and the brightness of the light emitted from the light source 4ya is stable, images of four different stripe patterns with different phases are captured.

[0065] In this way, the control device 6 switches between the projection devices 4x, 4y to be controlled, and sequentially executes phase change lighting processing on each of these projection devices 4x, 4y, and, when the brightness of the light emitted from the light sources 4xa, 4ya is stable, executes continuous imaging processing on the camera 5. In this embodiment, the control device 6 controls the projection devices 4x, 4y and the camera 5 to sequentially project and capture 8 (=4×2) different phase stripe patterns, thereby acquiring multiple image data with different light intensity distributions, and 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 sets of image data (brightness 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 the multiple sets of image data constitutes the "image processing means."

[0067] Next, the control device 6 performs a quality judgment process for the cream solder based on the three-dimensional measurement results (height data at each coordinate). Specifically, the control device 6 detects the cream solder printing range that is higher than the reference surface based on the measurement results of the inspection area obtained as described above, and calculates the amount of printed cream solder by integrating the height of each part within this range.

[0068] Next, the control device 6 compares the calculated data such as the amount of cream solder with reference data (such as Gerber data) previously stored in the set data memory device 26, and determines whether the printing condition of the cream solder in the inspection area is good or bad depending on whether the comparison result is within the acceptable range.

[0069] While this process is being performed, the control device 6 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 are repeated in all inspection areas until the inspection of the entire printed circuit board 2 is completed.

[0070] As described above in detail, according to this embodiment, after the rise time t1 has elapsed since the light sources 4xa and 4ya started to be turned on, that is, when the brightness of the light emitted from the light sources 4xa and 4ya is stable, the phase of the stripe pattern is changed and an image is captured by the camera 5. Therefore, the brightness of the light (grayscale according to the duty ratio) expressed by each pixel of the DMDs 4xb and 4yb on a frame-by-frame basis is appropriately reflected in the image data acquired by the camera 5. This makes it possible to more reliably prevent a decrease in the measurement accuracy related to three-dimensional measurement.

[0071] Furthermore, while the light sources 4xa and 4ya are on and the brightness of the light emitted from the light sources 4xa and 4ya is stable, the camera 5 successively captures four different stripe patterns with different phases. Therefore, compared to alternately capturing the stripe pattern associated with the first projection device 4x and the stripe pattern associated with the second projection device 4y, the illumination time of the light sources 4xa and 4ya required to capture the four stripe patterns can be shortened. That is, in this embodiment, the illumination time t of the light sources 4xa and 4ya can be set to approximately five frames (=4 frames + rise time t1 + fall time t2) when capturing the four stripe patterns (see FIG. 5). This allows the light sources 4xa and 4ya to have a longer life.

[0072] Furthermore, while the first projection device 4x is executing the phase change lighting process (i.e., while the light source 4xa of the first projection device 4x is on), the second projection device 4y starts to turn on the light source 4ya. Therefore, while the light source 4xa of the first projection device 4x is on 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 will next perform the phase change lighting process, can be stabilized. As a result, immediately after completing the imaging of the four stripe patterns projected from the first projection device 4x, it is possible to start imaging the stripe pattern projected from the second projection device 4y without particularly ensuring the rise time t1 for stabilizing the brightness of the light emitted from the light source 4ya. As a result, the three-dimensional measurement process can be performed at a high speed.

[0073] In addition, the second projection device 4y turns on the light source 4ya while turning off each pixel of the DMD 4yb to prevent the stripe pattern from being projected onto the printed circuit board 2. This prevents the image data (image data relating to the stripe pattern projected from the first projection device 4x) from being affected by the light source 4ya starting to turn on. This makes it possible to speed up the three-dimensional measurement process while more reliably preventing a decrease in measurement accuracy.

[0074] Furthermore, while the light source 4xa of the first projection device 4x is being turned off, the camera 5 starts capturing an image. That is, without waiting for the light source 4xa of the first projection device 4x to be turned off, the camera 5 starts capturing an image of the stripe pattern of the second projection device 4y. This allows for further speed-up of the three-dimensional measurement process.

[0075] Furthermore, while the light source 4xa of the first projection device 4x is turned 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 start of imaging while the light source 4xa is turned off from affecting the acquired image data (image data relating to the stripe pattern projected from the second projection device 4y). As a result, it is possible to more reliably prevent a decrease in measurement accuracy while further increasing the speed of the three-dimensional measurement process.

[0076] The present invention is not limited to the above-described embodiment, and may be implemented as follows: Of course, other applications and modifications not exemplified below are also possible.

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

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

[0079] (c) In the above embodiment, each of the projection devices 4x and 4y is configured to project four stripe patterns with a phase difference of 90°, but the number of phase shifts and the amount of phase shift are not limited to these, and other numbers of phase shifts and amounts of phase shifts that allow three-dimensional measurement by the phase shift method may be used. Therefore, the projection devices 4x and 4y may project, for example, three stripe patterns with a phase difference of 120°, or two stripe patterns with a phase difference of 180°.

[0080] (d) In the above embodiment, three-dimensional measurement is performed using the phase shift method, but this is not limiting and other pattern projection methods (three-dimensional measurement methods) such as the spatial code method may also be used. However, when measuring small measurement targets such as cream solder, 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 device 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, the present invention is not limited to this. For example, the inspection head including the projection devices 4x and 4y and the camera 5 may be moved to adjust to a predetermined inspection area on the printed circuit board 2 while the printed circuit board 2 is fixed.

[0082] (e) The configuration of the projection devices 4x and 4y is not limited to that of the above embodiment. For example, in the above embodiment, DMDs 4xb and 4yb are used as the "reflective light 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 gradations, frame rate, two-dimensional array configuration of micromirrors 41, direction of oscillation axis 41a of micromirrors 41, tilt angle of micromirrors 41, etc. related to DMDs 4xb and 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 ratio) that each micromirror 41 in DMD4xb, 4yb is in the on state during one frame period. However, this is not limited to this, and pulse density modulation (PDM) or the like may also be adopted, which adjusts the number of times each micromirror 41 is in the on state during one frame period. [Explanation of symbols]

[0085] 1...board inspection device (three-dimensional measurement device), 2...printed circuit board (object to be measured), 4x...first projection device (projection means), 4xa...light source, 4xb...DMD (reflective optical modulator), 4y...second projection device (projection means), 4ya...light source, 4yb...DMD (reflective optical modulator), 5...camera (imaging means), 6...control device (data acquisition means, image processing means).

Claims

1. a plurality of projection means each having a light source that emits a predetermined light and a reflective light modulation element that can convert 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 imaging the stripe pattern projected onto the object to be measured; a data acquisition means for controlling the projection means and the imaging means to sequentially project and capture the stripe patterns having different phases, thereby acquiring a plurality of image data having different light intensity distributions; a three-dimensional measuring apparatus including an image processing means capable of performing three-dimensional measurement of the object to be measured based on a plurality of image data acquired by the data acquisition means, the reflective light modulation element has a configuration in which a plurality of pixels are two-dimensionally arranged and switchable between an ON state in which the 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 the light from the light source is not projected onto the object to be measured, and is configured to be able to generate the stripe pattern by adjusting the ratio of the time in which the pixel is in the ON state during one frame period for each pixel; the data acquisition means is configured to sequentially execute, on each of the plurality of projection means while switching among the projection means to be controlled, a phase change lighting process in which, after a rise time required for the brightness of the light emitted from the light source to stabilize has elapsed since the lighting of the light source was started, the phase of the stripe pattern is changed a plurality of times while the light source is still turned on, and then the light source is turned off, and to cause the imaging means to execute a continuous imaging process in which, while the light source is turned on and the brightness of the light emitted from the light source is stable, each of the plurality of stripe patterns with different phases is imaged.

2. 2. The three-dimensional measuring device according to claim 1, wherein the data acquisition means is configured to, while one of the projection means is executing the phase change lighting process, start lighting of the light source by the projection means that subsequently executes the phase change lighting process after the first projection means while controlling the reflective light modulation element so that the stripe pattern is not projected onto the object to be measured.

3. 2. The three-dimensional measuring device according to claim 1, wherein the data acquisition means is configured to control the reflective light modulation element of one of the projection means so that the stripe pattern is not projected onto the object to be measured while the light source of one of the projection means is turned off, and to control the imaging means so as to start the continuous imaging process.

Images