JP2013016555A - Measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measuring accuracy of an incident light position.SOLUTION: The measuring device comprises: a light projection element 62 radiating detection light; an image sensor 85 opposed to the light projection element 62; a signal reading circuit 90 reading light receiving signals from the image sensor 85; and a measuring circuit 120 comparing a level of the light receiving signals with a predetermined reference level, and measuring and outputting an incident light position, at which the level of the light receiving signals varies from the reference level or more to the reference level or less, or from the reference level or less to the reference level or more, when a detected object passes through the detection region. A first filter circuit 100 removing a signal component of a predetermined frequency from a light receiving signal waveform read by the signal reading circuit 90 is provided between the signal reading circuit 90 and the measuring circuit 120.

Description

  The present invention relates to a measuring apparatus that measures an incident / light-shielding position on an imaging surface.

  2. Description of the Related Art Conventionally, a measuring apparatus that measures an incident light shielding position on an imaging surface is known. For example, the measuring apparatus disclosed in Patent Document 1 below includes a light projecting unit that emits detection light and a light receiving unit that has a two-dimensional imaging unit that receives the emitted detection light, and faces both units. It is placed at a certain distance in the state. Then, when a light shielding body such as a suction head or a part crosses between the two units, a part of the detection light is blocked by the light shielding body, so that the light receiving surface of the light receiving unit is blocked as shown in FIG. Only a portion (indicated by hatching in the figure) has a low signal level and a light-receiving image with a portion missing can be formed.

  At the edge of the partially missing received light image, the level of the received light signal is switched to light incident / light shielding. Therefore, the light receiving signal is read by the light receiving unit, and the light received signal level is changed from the light incident level to the light shielding level or the light shielding level. It is possible to determine the edge position of the partially missing light-receiving image by measuring the light-incoming light-shielding position that switches from the light-entering light level to the light-receiving level, and recognizes the orientation of the component that is the light-shielding body based on the light-receiving image.

JP 2008-31336 A

  By the way, the detection of the edge position (incident light shielding position) of the received light image is performed by measuring the position at which the level of the received light signal switches from the incident light level to the light shielding level. The sharper the difference is, the more accurately the edge position can be detected. However, in recent years, the relative distance L0 (see FIG. 2) between the light projecting unit and the light receiving unit may be set to be long, and the received light image is distorted depending on which position between the light shielding bodies passes between the units ( That is, the image has a small luminance difference at the edge position), and it has been regarded as a problem that the detection accuracy of the edge position is lowered. In particular, in the light-receiving image formed in the imaging unit, a light-receiving fringe is formed by interference of detection light due to light refraction by the light projecting lens and diffraction of detection light by the light shielding body. As a noise component, the edge position detection accuracy is further reduced.

  The present invention has been completed based on the above-described circumstances, and an object of the present invention is to improve the measurement accuracy of the incident light shielding position (edge position).

  As means for achieving the above object, a plurality of light projecting means for emitting detection light toward the detection area, a plurality of light projecting means and the detection area that are arranged to face each other and at least one-dimensionally disposed. A light receiving means comprising a plurality of light receiving elements, a signal reading means for sequentially reading a light reception signal from the light receiving means, a level of the light receiving signal read by the signal reading means and a predetermined reference level, and a detected object Measuring means for measuring and outputting an incident light shielding position where the level of the received light signal changes from the reference level to the reference level or from the reference level to the reference level when passing through the detection region; A signal component having a predetermined frequency is removed from the received light signal waveform which is disposed between the signal reading means and the measuring means and sequentially read by the signal reading means. It comprises a first filter circuit for.

As an embodiment of the present invention, the following configuration is preferable.
The predetermined frequency is a spatial frequency of light reception fringes formed in a light reception image formed by the light receiving means receiving the detection light. The light receiving fringes mentioned here include interference fringes due to interference of detection light and diffraction fringes due to diffraction.

A second filter circuit is provided between the first filter circuit and the measuring means to secondarily differentiate the received light signal waveform to obtain a difference from the received light signal waveform and output the difference.

  According to the present invention, since the noise component of the light reception fringes is removed by the filter circuit, the incident light shielding position where the level of the light reception signal changes from the reference level or more to the reference level or less, or from the reference level or less to the reference level or more. Can be detected accurately.

Plan view of a component mounter applied to this embodiment The perspective view which shows the state in which the components hold | maintained at the suction head cross a detection optical axis Block diagram showing the electrical configuration of the measuring device The figure which shows the light-receiving surface of the CMOS image sensor Digital filter circuit block diagram Diagram showing the relationship between component posture and incident light position Diagram showing the positional relationship between the image sensor and the light-shielding object Diagram showing the relationship between component posture and incident light position Diagram showing received light signal waveform (before passing through digital filter circuit) Diagram showing received light signal waveform (after passing through digital filter circuit) Diagram showing received light signal waveform (before passing through digital filter circuit) Diagram showing received light signal waveform (after passing through digital filter circuit) The block diagram which shows the electrical constitution of the measuring device in Embodiment 2. Diagram showing received light signal waveform (before Laplacian filter processing) Diagram showing received light signal waveform (after Laplacian filter processing)

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, the measuring apparatus 50 according to the present invention is mounted on a component mounter 10. The component mounting machine 10 is provided with a substrate transporting conveyor 15 at the center of the base 11, and after mounting the image F to be mounted on the base 11, it is stopped at a work position near the center of the base. It is like that.

  A component supply unit 16 is provided on the lower side of FIG. A large number of feeders 40 are installed side by side in the component supply unit 16. The feeder 40 has a function of supplying a component W mounted on the board F.

  In addition, a pair of guide rails 21 are installed on both the left and right sides of the base 11 with a work position interposed therebetween, and a head support 22 is installed with the guide rails 21 extending from side to side. The head support 22 is configured to be movable in the vertical direction in FIG. 1 along the left and right guide rails 21.

  A head unit 30 is attached to the head support 22. The head unit 30 is configured to be movable in the longitudinal direction of the head support 22. Accordingly, the head unit 22 is moved in the left-right direction along the head support 22 while moving the head support 22 in the up-down direction along the guide rail 21, so that the head can be placed at an arbitrary position on the base 11. The unit 30 can be moved horizontally.

  A suction head 31 is attached to the lower surface of the head unit 30 so as to protrude downward (omitted in FIG. 1, see FIG. 2). The suction head 31 is configured to be movable up and down with respect to the head unit 30, and a suction nozzle 35 is provided at the tip. A negative pressure is supplied to the suction nozzle 35 from a negative pressure means (not shown) to generate a suction force at the tip of the head.

  By configuring as described above, the part W on the feeder 40 can be taken out in the following manner. First, the head unit 30 is moved onto the feeder 40 and stopped above the feeder 40 (position (A) shown in FIG. 1).

  Thereafter, the suction head 31 is lowered, and negative pressure is supplied to the suction head 31 in accordance with the lowering timing. Thereby, the component W supplied through the feeder 40 can be sucked and held by the suction head 31.

  Thereafter, if the suction head 31 in the lowered state is raised, the component W held by suction rises together with the suction head 31. Thus, the part W is taken out from the feeder 40.

  When the work for taking out the component W is completed, a process of moving the head unit 30 located above the feeder toward the upper side of the substrate F stopped at the work position is then performed in order to mount the component on the substrate F. Is called.

  Accordingly, in the example of FIG. 1, the head unit 30 holding the component W moves to the upper side of the paper of FIG. 1 on the back side of the base, but this embodiment will be described later in the movement process. When the component W sucked and held at the tip of the suction head 31 crosses the detection optical axis L of the measuring device 50 (see FIG. 2), the posture of the component W sucked and held by the suction head 31 is inspected (hereinafter, both detected) It is configured to say.

  If there is no abnormality in the component posture as a result of the inspection, the component mounting process by the head unit 30 is advanced, and the component W is mounted on the substrate F that stops at the work position.

Next, the measuring apparatus 50 will be described.
The measuring device 50 emits detection light toward a detection region K through which a component W that is a detection object passes, and is disposed oppositely with the light projection unit 60 and the detection region K interposed therebetween and emitted. And a light receiving unit 70 that receives the detected light. Both units 60 and 70 are ones in which various devices are built in casings 61 and 71.

  As shown in FIG. 3, the light projecting unit 60 includes a light projecting element (that is, a laser light source) 62 composed of a laser diode. The light projecting unit 60 is electrically connected to the light receiving unit 70 and drives the light projecting element 62 to emit laser light as detection light in accordance with a light projecting command issued from the control circuit 130 on the light receiving unit 70 side. It has a configuration.

  The light receiving unit 70 includes a light receiving unit 80 that receives the detection light emitted from the light projecting unit 60. The light receiving unit 80 includes a condenser lens 81 and an image sensor 85. The condenser lens 81 has a function of causing the detection light to be incident on the image sensor 85 while condensing the detection light, and is disposed in front of the image sensor 85.

  As shown in FIG. 4, the image sensor 85 is a two-dimensional sensor in which light receiving elements (hereinafter also referred to as pixels) P are arranged in a matrix to form a light receiving surface 86. A CMOS image sensor having a CMOS (Seamos) device structure in which an amplifying element is incorporated in the element P is used.

  The CMOS image sensor can read a light reception signal (a signal charge is amplified internally to be a signal voltage) by selecting a light reception element P from a plurality of light reception elements P constituting the light reception surface. It is known as a random access type device. The CMOS image sensor 85 applied to the present embodiment has a format in which a light reception signal is read out for each vertical line V, and the vertical lines V1 to V16 that are read-out images can be arbitrarily selected.

  The CMOS image sensor 85 corresponds to the light receiving means of the present invention.

  Returning to FIG. 3, the description will be continued. The light receiving unit 70 includes a control circuit 130 that controls and controls the entire unit, a signal readout circuit 90, a digital filter circuit (corresponding to the “first filter circuit” of the present invention) 100, A measurement circuit 120 and a storage unit 135 are provided.

  The signal readout circuit 90 reads out the received light signal from the CMOS image sensor 85 in accordance with a readout command given from the control circuit 130.

  The digital filter circuit 100 is disposed between the signal readout circuit 90 and the measurement circuit 120. As shown in FIG. 5, the digital filter circuit 100 is an M-order (specifically sixth-order) FIR (Finite Impulse Response) filter, and includes six stages of delay elements T, amplifier elements A, and adders U. It has become. In FIG. 5, “x” indicates an input signal, and “y” indicates an output signal. This digital filter circuit 100 has a predetermined frequency, that is, a light-receiving fringe Y, from a light-receiving signal waveform read from the signal reading circuit 90 (light-receiving signal waveform with the position on the read line V as the horizontal axis and the light-receiving signal level as the vertical axis). This is a circuit for removing a signal component in the spatial frequency band, and the filter coefficients a1 to a7 of the respective amplification elements A1 to A7 are set so that the spatial frequency of the light receiving fringes Y included in the received light image Z is included in the stop band. .

  More specifically, the light reception image Z formed by the image sensor 85 receiving the detection light includes a light reception fringe (a general term for interference fringes and diffraction fringes) Y. This is because interference fringes are generated by interference of detection light refracted by a projection lens (not shown), and diffraction fringes are caused by detection light being diffracted by a light-shielding object such as a component W that crosses the detection optical axis L. This is because it is possible. Such diffraction fringes have different fringe repetition periods, that is, spatial frequencies, according to the distance La from the image sensor 85 to the light shielding object. FIG. 6 schematically shows an example of the light receiving stripe Y.

  Therefore, in the present embodiment, as shown in FIG. 7, the light receiving image Z is photographed by placing the part W, which is a light shielding object, at three points near the light receiving unit 70, that is, the middle point and the far point. Thus, the spatial frequency of the diffraction fringe is specified as an example of the light receiving fringe.

  More specifically, first, Fourier transform is performed on the image data of the received light image Z for each of the three points, and a power spectrum distribution indicating the correlation between the spatial frequency and the power spectrum is calculated.

  When the component W is placed at each of these three points (near point, middle point, far point), the received light image is the same image except for diffraction fringes, so the power spectrum distributions of the three received light images are compared. By examining whether or not there is a change, it is possible to specify the spatial frequency of the diffraction fringes generated corresponding to the passage position of the light shielding object. That is, regarding the power spectrum distribution of the near-point received light image, if there is a change in the frequency band Fa with respect to the power spectrum distribution of other received light images, the diffraction fringes generated when the part passes the near point The spatial frequency is known as “frequency band Fa”.

  Similarly, with respect to the power spectrum distribution of the received light image at the intermediate point, when a change is observed in the frequency band Fb with respect to the power spectrum distribution of the other received light images, the change can be made when the component passes the intermediate point. The spatial frequency of the diffraction fringes is known as “frequency band Fb”. In addition, regarding the power spectrum distribution of the received light image at the far point, when there is a change in the frequency band Fc with respect to the power spectrum distribution of the other received light images, the diffraction fringes generated when the part passes the far point The spatial frequency is known as “frequency band Fc”.

  In the present embodiment, the frequency band Fa˜ so that the light receiving fringes (diffraction fringes) generated by the light shielding object can be removed (filtered) from the received light signal waveform no matter which point from the near point to the far point passes through the light shielding object. The filter coefficients a1 to a7 are set so as to include all Fc in the stop band. In this embodiment, since the frequency bands Fa to Fc exist at 8 MHz or more, the filter coefficients a1 to a7 are set so as to be a low-pass filter having a stop band of 8 MHz or more and a pass band of 8 MHz or less. doing.

  The measurement circuit 120 compares the received light level (hereinafter also simply referred to as level) of the received light signal that has passed through the digital filter circuit 100 with a preset reference level R so that the level of the read received light signal is the reference level R. It is determined whether the light incident level is above or the light shielding level is below the reference level R. Then, the measurement circuit 120 measures an incident light blocking position on the detection line V where the level of the received light signal is switched from the incident light level to the blocked light level or from the blocked light level to the incident light level. In addition, according to the above, “the level of the light reception signal is compared with a predetermined reference level, and when the detected object passes through the detection region, the level of the light reception signal is higher than the reference level and lower than the reference level. Alternatively, the measurement of an incident light shielding position that changes from the reference level or less to the reference level or more is realized.

  The result measured by the measurement circuit 120 is output to a posture detection device 140 provided separately from the light receiving unit 70 via a signal line.

  Next, the operation of the measuring apparatus 50 will be described. When a timing signal Sr for notifying the movement timing of the suction head 31 is input from a control circuit (not shown) on the component mounter 10 side, measurement is automatically started in the following manner.

  To explain in sequence, upon receiving the timing signal Sr, the control circuit 130 gives a projection command to the projection unit 60 in accordance with the timing at which the component W sucked and held by the suction head 31 crosses the detection optical axis L. Then, the light projecting element 62 is turned on in pulses.

  Then, the detection light emitted from the light projecting element 62 enters the light receiving surface 86 of the CMOS image sensor 85 while being collected by the condenser lens 81. At this time, a part of the detection light is blocked by the suction head 31 and the part W held by suction. Therefore, the light receiving surface 86 of the CMOS image sensor 85 has a partially missing light receiving image Z having a low light receiving level only in the blocked portion (shown by hatching in FIG. 8).

  Then, in accordance with the formation of the received light image Z, the signal readout circuit 90 sequentially reads the received light signal from the light receiving element P on the detection line V. Thereafter, the read light reception signal is input to the digital filter circuit 100.

  The digital filter circuit 100 suppresses all high frequency signals of 8 MHz or higher. Since the light reception fringes (here, diffraction fringes) included in the light reception image Z are included in this band, the noise component due to the light reception fringes Y is removed from the light reception signal waveform by passing the light reception signal through the digital filter circuit 100. it can. FIG. 9 shows a light reception signal waveform before passing through the digital filter circuit 100, and FIG. 10 shows a light reception signal waveform after passing through the digital filter circuit 100. In the received light signal waveform of FIG. 10, it can be understood that the noise component can be removed from that of FIG.

  The received light signal that has passed through the digital filter circuit 100 is then input to the measurement circuit 120. In the measurement circuit 120, processing is performed to detect whether the read light reception signal level is the incident light level or the light shielding level, and the light reception signal level is shielded from the incident light level on the detection line V. The level or the incident / light-shielding position at which the light-shielding level is switched to the incident light level is measured.

  In this example, the upper side from the lower surface of the component is in a light shielding state, whereas the lower side from the lower surface of the component is in a light incident state. Therefore, in the case of (1) in FIG. 8 in which the component W is correctly held by the suction head 31, the incident / light shielding position is the position (c). The light reception signal waveforms in FIGS. 9 and 10 are those of (1) in FIG. 8 in which the components are correctly held, and at the position (c), the light reception level is switched from the light incident level to the light shielding level. ing. On the other hand, in the case of (2) in FIG. 8 in which the component W is held on the suction head 31 in a standing posture, the position (d) is the incident light shielding position.

  Then, the light incident / shielding position data is output from the measurement circuit 120 to the posture detection device 140, and the posture detection device 140 performs processing according to the light incident / light shielding position data.

  That is, when the posture detection device 140 receives data indicating that the incident / light-shielding position is the position (c), the posture detection device 140 determines “maintain normally” and sends a control signal to the component mounter 10 to advance the component mounting process. . As a result, under the initiative of the component mounter 10, the mounting process of mounting the component W on the board F stopped at the work position is advanced.

  On the other hand, when the posture detection device 140 receives data indicating that the incident / light-shielding position is the position (d), it determines that it is a “holding error” and sends an error signal to the component mounter 10. As a result, error processing is performed in the component mounter 10.

  Then, the mounting process of the component W on the board F is advanced by repeatedly performing the posture detection of the component W and the mounting process of the component W in the above manner.

Next, the effect of this embodiment will be described.
Depending on where the component W passes between the two units 60 and 70, the received light image becomes a sharp image (that is, an image having a large luminance difference at the incident / shielded position) or a distorted image (that is, at the incident / shielded position). Image with a small luminance difference). This is because the subject W and the light receiving lens 81 are in focus or not in focus.

  If the received light image does not pass the focus and the received light image has a distorted waveform, if the received light signal is not passed through the digital filter circuit 100, as shown in FIG. Since they are superposed, it is easy to erroneously detect the incident light shielding position. More specifically, the position (D) and the position (E) are erroneously detected where the intermediate position between the position (D) and the position (E) should be correctly detected as the incident / light shielding position.

  In this regard, in the present embodiment, the light reception signal is passed through the digital filter circuit 100, and the signal component (that is, noise component) of the light reception stripe Y is removed from the light reception signal waveform as shown in FIG. Therefore, the incident / shielded position of the received light signal can be accurately measured. Specifically, a position (F) corresponding to a substantially intermediate position between the position (D) and the position (E) is detected as the incident light shielding position. Therefore, the posture of the component W can be accurately recognized.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIGS.
The light receiving unit 170 of the second embodiment is obtained by adding a Laplacian filter circuit (corresponding to the “second filter circuit” of the present invention) 110 to the light receiving unit 70 of the first embodiment. The Laplacian filter circuit 110 is between the digital filter circuit 100 and the measurement circuit 120, performs the following processing on the received light signal that has passed through the digital filter circuit 100, and outputs it to the subsequent measurement circuit 120.

  In the Laplacian filter circuit 110, a second derivative of the waveform data of the light reception signal (original light reception signal) is obtained, and then a process of subtracting the second derivative from the light reception signal (original light reception signal) is performed.

  By performing the above processing, it is possible to generate waveform data in which the luminance difference at the incident / shielded position of the received light signal is emphasized. For example, as shown by the alternate long and short dash line in FIGS. 13 and 14, the received light signal is a signal having a large luminance difference at the incident / shielded position. In FIGS. 13 and 14, the original light reception signal is indicated by a solid line, and the light reception signal after the Laplacian filter processing is indicated by an alternate long and short dash line.

  As described above, if the Laplacian filter circuit 110 is provided between the digital filter circuit 100 and the measurement circuit 120, the luminance difference at the incident light position is reduced due to the rounding of the waveform caused by the passage of the digital filter circuit 100. In this case, the luminance difference can be restored, so that the incident / light-shielding position of the received light signal can be accurately measured by the measurement circuit 120 at the subsequent stage. Therefore, the posture of the component W can be accurately recognized.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the above embodiment, the two-dimensional CMOS image sensor 85 is used for the light receiving unit 80. However, the light receiving element can be two-dimensionally arranged and an arbitrary line can be selected to read a light reception signal. For example, a light receiving surface may be configured by arranging a plurality of one-dimensional line sensors. Further, it may be simply a one-dimensional line sensor.

  (2) In the above-described embodiment, the example in which the noise component due to the diffraction fringes is removed from the light reception signal waveform has been described. For this purpose, the spatial frequency of the interference fringes is detected by analyzing the waveform of the received light signal waveform, and the filter coefficient of the digital filter circuit (low-pass filter circuit) is set so that the band is included in the stop band.

DESCRIPTION OF SYMBOLS 50 ... Measuring apparatus 60 ... Light projection unit 62 ... Light projection element (equivalent to the "light projection means" of this invention)
DESCRIPTION OF SYMBOLS 70 ... Light receiving unit 80 ... Light receiving part 81 ... Condensing lens 85 ... CMOS image sensor (equivalent to the "light receiving means" of this invention)
90... Signal readout circuit (corresponding to “signal readout means” of the present invention)
100: Digital filter circuit (corresponding to “first filter circuit” of the present invention)
110 ... Laplacian filter circuit (corresponding to "second filter circuit" of the present invention)
120... Measuring circuit (corresponding to “measuring means” of the present invention)
DESCRIPTION OF SYMBOLS 130 ... Control circuit 180 ... Attitude detection apparatus L ... Detection optical axis W ... Component (equivalent to "detected object" of this invention)
V ... Vertical line)

Claims (3)

A light projecting means for emitting detection light toward the detection region;
A light receiving means comprising a plurality of light receiving elements arranged opposite to each other across the light projecting means and the detection region, and arranged in a one-dimensional manner;
Signal readout means for sequentially reading out the received light signals from the light receiving means;
The level of the received light signal read by the signal reading means is compared with a predetermined reference level, and when the detected object passes through the detection area, the level of the received light signal is higher than the reference level and lower than the reference level. Or a measuring device comprising measuring means for measuring and outputting an incident light shielding position that changes from the reference level or lower to the reference level or higher,
A measuring apparatus comprising a first filter circuit disposed between the signal reading unit and the measuring unit and configured to remove a signal component having a predetermined frequency from a received light signal waveform sequentially read by the signal reading unit.   The measuring apparatus according to claim 1, wherein the predetermined frequency is a spatial frequency of a light-receiving fringe formed in a light-receiving image formed by the light-receiving unit receiving the detection light.   2. A second filter circuit is provided between the first filter circuit and the measuring means, wherein a second filter circuit that secondarily differentiates the received light signal waveform to obtain a difference from the received light signal waveform and outputs the difference is provided. The measuring apparatus according to claim 2.

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