JP6285376B2 - Edge detection device - Google Patents

Description

  The present invention relates to an edge detection apparatus that detects an edge position of a detected object (work) that is a detection object.

  When an object exists in the optical path of monochromatic light typified by laser light, Fresnel diffraction occurs at the edge position of the object. Therefore, an edge detection apparatus has been developed that uses a line sensor to determine the light intensity distribution of the Fresnel diffraction and detects the edge position of the object by analyzing the light intensity distribution. That is, when the detection object is positioned so as to block a part of the optical path irradiated with monochromatic parallel light from the light projecting unit toward the line sensor in which a plurality of pixels are arranged, the output of the line sensor indicates the edge position of the detection object. It changes greatly as a boundary. In particular, it is known that the light intensity distribution on the line sensor shows a certain change tendency under the influence of Fresnel diffraction in the vicinity of the edge position.

The invention disclosed in Patent Document 1 can accurately detect the edge position of an object to be detected, and whether the line sensor is in a completely incident state or in a completely shielded state by a transparent body. Can be determined. For example, in order to provide an edge detection device suitable for use in position control of the detected object, an edge position analyzing means for detecting the edge position of the detected object is provided, and the detected object is further detected by the edge position analyzing means. If the total light reception amount by the line sensor is smaller than the total light reception amount in the total light incident state of the line sensor stored in advance when the edge position of the line sensor cannot be detected, the total light shielding is determined as the total light shielding state by the detected object It is characterized by comprising state determination means.

In the invention disclosed in Patent Document 2, when detecting the edge position of an object to be detected positioned in the optical path of monochromatic parallel light from the output of a line sensor in which a plurality of light receiving cells are arranged at a predetermined pitch, The output is searched from the free space side, and the position where the light quantity is reduced to the first light quantity threshold is detected from the light quantity distribution pattern generated at the edge of the object as the first detection position. The position that has increased to the light amount threshold value is detected as the second detection position of the object. A defect such as a chip or a crack is detected from changes in the first and second detection positions when the inspection site is scanned along the edge.

JP 2007-64733 A JP 2009-75078 A

  In the edge detection device of Patent Document 1 or Patent Document 2, it is assumed that the positional relationship between the laser light source that is the light projecting unit and the line sensor that is the light receiving unit is consistent. At the time of device calibration, the position applied to the optical axis has been adjusted, but there has been a problem that the optical axis is displaced due to changes in equipment over time, vibration shocks, and the like.

  The present invention uses the property that both ends of the line sensor are not suitable for measurement in the first place, and detects the optical axis deviation quickly even during operation by monitoring the light quantity at both ends (unused area). To solve the problem.

The present invention relates to a pixel arrangement of the line sensor from a line sensor, a light source that emits monochromatic light toward the line sensor, and a light intensity distribution of Fresnel diffraction at the edge of the detected object positioned in the optical path of the monochromatic light. Edge position analyzing means for detecting the edge position of the detected object in the direction;
An edge detection apparatus comprising: an optical axis misalignment determining unit that detects an optical axis misalignment based on light amount data at both ends of the line sensor not used in the edge position analyzing unit.

  The optical axis misalignment determining means determines the direction where the detected object is present and the direction where there is no detected object based on the light amount data at both ends of the line sensor, and the light amount without the detected object is a predetermined light amount deviation. An edge detection apparatus that detects an optical axis shift when a condition is met.

More specifically, the light amount deviation condition is
If the amount of light without the detected object is greater than a predetermined threshold,
If the amount of light without the detected object is smaller than a predetermined threshold,
Is an edge detection device.

  According to the present invention, edge detection is provided with a function for detecting the occurrence of optical axis misalignment between the light source and the line sensor, in parallel with the function for detecting the detected object by the transmission line sensor even during operation. Providing equipment. Of course, when there is no object to be detected, the calibration function can be implemented under free conditions.

Overall configuration diagram of an edge detection apparatus according to the present invention Light quantity data characteristic chart with respect to optical axis deviation, which is an embodiment of the present invention Main part flowchart of edge detection apparatus according to the present invention

(1) Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is a diagram showing a schematic configuration of an edge detection apparatus according to this embodiment, and 1 is a line sensor in which a plurality of pixels are arranged at a predetermined pitch. The breakdown consists of a CMOS linear image sensor, an AD converter, and a communication controller. On the other hand, reference numeral 2 denotes a light source provided so as to face the line sensor 1 and irradiating the line sensor 1 with monochromatic parallel light. The light source 2 is a projector including, for example, a laser element and a light projecting lens that irradiates the line sensor 1 with laser light emitted from the laser element as parallel light. It is driven from a light projection control unit 4c of the microcomputer 4 to be described later. The optical path irradiated with the monochromatic parallel light between the line sensor 1 and the light source 2 is used as a detection region for detecting the edge of the detected object 3. Since both end portions of the line sensor 1 are not suitable for measurement, the center portion is used region and both end portions (approximately several percent pixel region) are unused regions.

  The microcomputer 4 that receives the output signal (light intensity signal) of the line sensor 1 analyzes the output signal to detect the edge position of the detected object 3 in the pixel array direction of the line sensor 1. Means 4a are provided. The edge position analysis means 4a receives the output signal from the line sensor 1, first performs disturbance light removal, and normalizes the signal data. Edge search is performed using the normalized light quantity data. In this case, subpixel processing or other arithmetic processing is performed to detect a position where the light amount data is a predetermined value or less as an edge position. Then, the result of edge detection is passed to the output control unit 4d.

  Next, when the edge position of the detected object 3 can be detected by the edge position analyzing means 4a, the optical axis deviation determining means 4b executed from the light quantity data at both ends of the line sensor 1 is executed. The optical axis deviation determination unit 4b may use light amount data after disturbance light removal and normalization performed by the edge position analysis unit 4a.

  The optical axis misalignment determining means 4b is preliminarily determined from the output signal of the line sensor 1 in the total light incident state detected in a state where the detected object 3 is not interposed in the optical path when the edge detection device is initially started. Means are provided for determining the amount of received light and storing this as an initial value. Incidentally, the total amount of received light is obtained by calculating the sum of light quantity data of a plurality of pixels 1 to n constituting the line sensor 1. The optical axis misalignment determining means 4b also stores light amount data at both ends of the line sensor 1 at the initial stage. Then, it may be used for comparison and determination as a predetermined value with the light amount data of the portion not covered with the detected object 3 during driving. This is M_Bottom described later.

  Although the measurement area at the center of the plurality of pixels 1 to n constituting the line sensor 1 is used, the unused areas at both ends are referred to as Top and Bottom. Here, for convenience, the one far from the microcomputer is denoted as Top, The closer one is called “Bottom”, but the calling method is arbitrary. Assuming that the light source 2 has shifted to the top (Top) side from the beginning, it can be seen that the light amount data on the Bottom side is small. This is because, as indicated by a broken line at one end of the optical path in FIG. When such an abnormality is found, it is the optical axis deviation determination means 4b that determines that an optical axis deviation has occurred.

(2) Next, the determination logic of the optical axis deviation will be described using the light quantity data characteristic diagram with respect to the optical axis deviation of FIG. FIG. 2 is a plan view of the line sensor 1 viewed from the light source 2. 2 shows a rectangle indicating the unused area of the line sensor 1 and shows that the laser beam 10 is irradiated with a rounded rectangle on the outer periphery thereof. As shown in the upper left XY coordinate, it is usually assumed that an optical axis shift occurs in the X-axis direction from Top to Bottom.

Now, FIGS. 2A to 2D show examples in which an object to be detected (denoted as a detection object in the figure) 3 is inserted from the Top side.
In FIG. 2A, there is no deviation of the optical axis (that is, the laser beam 10), indicating a normal state, and the distribution of light amount data in the characteristic diagram on the right side of FIG. 2A is normal.
In FIG. 2B, it can be seen that the optical axis is shifted to the bottom side, and the light amount data on the bottom side is increased on the right side of FIG. 2B.
FIG. 2C shows the case where the optical axis is shifted to the Top side, and it can be seen that the light amount data on the Bottom side is small on the right side of FIG. 2C.
FIG. 2D shows a case where the optical axis is shifted in the Y-axis (−) direction, and it can be seen that the light amount data on the Boot side does not change much on the right side of FIG. 2D.

Thus, conditions for detecting an abnormality caused by an optical axis shift for detecting the optical axis shift when there is an optical axis shift will be described. The light quantity data is described with M_. The predetermined value here may be an average value of all received light amounts, or an M_Bottom value at the time of initial calibration is used. This is multiplied by a parameter to obtain a threshold value.

A change in the light quantity data M_Bottom is detected, and will be described according to the case of FIG.
M_Bottom> 110% Of Predetermined value: number (1)
This considers the case where the light hits excessively as shown in FIG. 2B.
next,
M_Bottom <10% Of Predetermined value ... number (2)
The case where the light no longer hits abnormally as shown in FIG. 2C is considered.
In addition, when the optical axis is shifted with respect to the Y-axis as shown in FIG. 2D, it is necessary to perform a more specific calculation (in correlation with the total amount of received light), but the present invention does not appeal so far.

(3) The operation centering on the edge position analyzing means 4a and the optical axis deviation determining means 4b will be described with reference to the flowchart of FIG.
First, it starts when the power is turned on (S0) (hereinafter, steps in FIG. 3 are indicated by Sn). Here, initialization processing such as driving the light source 2 is performed. Stores the total amount of light received. An optical axis calibration process may also be performed.

Subsequently, an output signal (light intensity signal) is acquired from the line sensor 1 and a light receiving process such as normalization is executed (S1). Next, a calculation process for detecting the edge position in comparison with the threshold for edge detection is performed (S2). If the predetermined edge is detected (Yes), the process proceeds to the edge detection process (S3) in step S3. Such normal processing is the same as that described in Patent Document 1 and the like, and thus further description thereof is omitted.

  If the edge cannot be detected (No), the calibration detection process for checking whether the detected object does not exist (free) from the initial calibration data based on the light amount data at both ends of the line sensor 1 (S10) Fly to. This can be a simple check.

  After the edge detection process (S3), the area detection process for the optical axis deviation determination means 4b is performed (S4). Here, the presence / absence of an object to be detected is checked in both directions of Top / Bottom using the light intensity data at both ends of the line sensor 1, and it is checked whether there is an abnormality based on the light intensity data on the side without the object to be detected. The judgment condition is based on the equations (1) and (2) described above.

If a deviation error is not found in the light amount data at both ends (No), the result is a loop end.
If a deviation abnormality is found in the light amount data (Yes), the process proceeds to an optical axis deviation notification process (S6) for promptly notifying that an optical axis deviation has occurred. Therefore, preparation for event output to that effect is made.

After executing the calibration detection process (S10) when no edge is detected or the optical axis deviation notification process (S6), an output control process such as an event output to the outside is performed (S20). It is also possible to add a function such as logging various optical signal data when the event occurs.

  As described above, the entire process is completed and the process loops and returns to step S1, and this is repeated.

  Although the embodiment of the edge detection apparatus according to the present invention has been described, the threshold value and other parameters do not need to stick to the exemplified values, and various design tunings are possible.

  Object to be detected The object to be detected is not limited to glass but relates to a processing process such as a thin film. Since the total light-shielding state determination of the present invention can be executed instantaneously, it can be used for a process control system that requires real-time performance.

1 Line sensor 2 Light source 3 Object 4 Microcomputer 10 Laser beam

Claims (3)

A line sensor and a light source that emits monochromatic light toward the line sensor;
Edge position analysis means for detecting the edge position of the detected object in the pixel array direction of the line sensor from the light intensity distribution of Fresnel diffraction at the edge of the detected object positioned in the optical path of the monochromatic light;
An edge detection apparatus comprising: an optical axis shift determination unit that detects an optical axis shift based on light amount data at both ends of the line sensor that is not used in the edge position analysis unit. The edge detection apparatus according to claim 1,
The optical axis misalignment determining means determines the end of the line sensor where the detected object is present and the end where the detected object is absent based on the light amount data at both ends of the line sensor. An edge detection device that detects a deviation of an optical axis when a light quantity deviation condition of the optical axis is met. The edge detection apparatus according to claim 2, wherein the light amount deviation condition is:
If the amount of light without the detected object is greater than a predetermined threshold, or
If the amount of light without the detected object is smaller than a predetermined threshold,
An edge detection apparatus characterized by being one of the above.

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