JPH0623643B2 - Edge position detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an edge position detecting device that optically detects an accurate position of an edge (edge portion) of an object.

(Prior Art) Generally, there is a strong demand for knowing the position of an edge of an object from optical imaging, and it is used in many technical fields for an assembly process or automation of work.

FIG. 3 is a diagram showing a conventional configuration of such an optical edge detecting device. Reference numeral 1 denotes an object to be detected whose edge is to be detected. When the object to be measured reflects light emitted from a light source, the reflected light is sensed and imaged by a line sensor 2 such as a CCD, and its output is a multiplexer (hereinafter ,
After being multiplexed by an MPX 3 and sample-held by a sample-hold (hereinafter referred to as S / H) circuit 4, analog-digital (hereinafter referred to as A / D)
The output of the line sensor 2 is digitally converted. That is, the output of the line sensor 2 including the detection information of the edge of the DUT 1 is taken out as a digital signal. Hereinafter, this digital signal is referred to as the output (or digital output) of the line sensor 2.

The digital output of the line sensor 2 is applied to the subtractor 6 and stored in the first memory 7 for each frame. Reference numeral 8 denotes a second memory in which an output of the line sensor 2 (referred to as a background signal) when the device under test 1 does not exist is stored in advance, and the output is applied to the subtractor 6 to generate a line. It is subtracted from the digital signal of the sensor 2. Therefore, the output of the subtractor 6 is the DUT 1
Is a signal containing the complete edge information of only the DUT 1 whose background signal has been subtracted, which is the third memory 9
Memorized in. An averaging circuit 10 divides the total digital output of the line sensor 2 for one frame by the number of bits for one frame to calculate an average value. Reference numeral 11 denotes an arithmetic unit that calculates a threshold value for edge detection by adding, subtracting, multiplying, and dividing a certain fixed value to the output of the averaging circuit 10. 12 is a comparator, the third
The output signal of the memory 9 is compared with the threshold output of the arithmetic unit 11, and the output is used to correspond the digital output of the line sensor 2 to the scanning position to detect the edge position. 13 is a microcomputer (hereinafter referred to as CPU)
Then, the position of the edge of the DUT 1 is calculated from the output of the comparator 12. 14 is a data bus.

FIG. 4 shows the result of edge detection by the configuration of FIG. 3 described above, where a is the output of the subtracter 6, which is the output of the line sensor 2 after subtracting the background signal. b is a threshold value of the output of the calculator 11. Therefore, the edge position detected by the DUT ₁ becomes the bit position m ₁ at which the output exceeds the threshold value b.

(Problems to be Solved by the Invention) However, in the conventional optical edge detection device, since the edge position is determined by whether or not a certain threshold is exceeded, the cross section of the edge of the DUT 1 is curved. In the case of a spherical surface, there is a problem that the detected edge position lacks accuracy. That is, as shown in FIG. 5, although the correct edge position is the bit position m ₃ , the cross section of the edge changes gently, so that the digital output gradually increases and exceeds the threshold value b. m ₂ is detected as the edge position.

The present invention aims to provide an excellent optical edge position detecting device which eliminates the problems of the conventional device.

(Means for Solving the Problems) In order to achieve the above object, the present invention is provided with a differentiator and an integrator in addition to the configuration of FIG. The difference between adjacent bits of the digital output is taken, and whether the difference is positive or negative is judged. When this difference takes a positive value, the bit position P is temporarily stored, and when it takes a negative value, an integrator is taken. The difference value is integrated by, and it is determined whether or not the integrated value has reached a constant first threshold value. If the integrated value has not reached the first threshold value, the memory is canceled and the When the threshold value of 1 is reached, the bit position is further changed and integration is performed. When the integrated value reaches a second threshold value that is larger than the first threshold value, the bit position P is set. It is determined as the edge position.

(Operation) According to the present invention, the difference between the digital outputs of adjacent bits is calculated, and when it is determined that the digital output has increased, this is detected as the edge position.

(Example) Hereinafter, the Example of this invention is described in detail, referring drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and the same reference numerals as those in FIG. 3 denote the same parts.

Reference numeral 1 is an object to be detected whose edge is to be detected. When the object to be measured reflects the light emitted from the light source, the reflected light is CC
S / H, which is detected and imaged by the line sensor 2 such as D, and whose output is multiplexed by MPX3.
It is sampled and held by the circuit 4 and is digitally converted by the A / D conversion circuit 5. That is, the DUT 1
The output of the line sensor 2 including the detection information of the edge of is converted into a digital signal and applied to the subtractor 6, and
It is stored in the first memory 7. This first memory 7 is
The digital output of the line sensor 2 is stored for each frame. In the subtractor 6, the background signal of the device under test 1 stored in advance in the second memory 8 is subtracted from the output of the A / D conversion circuit 5, and the edge information signal of only the device under test 1 is output. Then, it is stored in the third memory 9.
Reference numeral 15 is a differentiator, whereby the data of the contents of the third memory 9 is controlled by the CPU 13, and the difference is sequentially detected for each adjacent bit of the digital output of the line sensor 2, and the value is integrated by the integrator 16. After that, the values are compared with the values in the fourth memory 19 and the fifth memory 20 by the comparators 17 and 18, respectively. The fourth memory 19 and the fifth memory
A threshold value 1 for determining an edge and a threshold value 2 higher than that are stored in the reference numeral 20, and are shown in FIG. Algorithm control is performed to detect edges.

FIG. 2 is a flow chart for explaining the edge detection algorithm of the embodiment of the present invention shown in FIG.
(However, i is an arbitrary positive integer, the same applies hereinafter) is the bit position of the digital signal output of the line sensor 2, D _i is the i-th output of the line sensor 2, K is the difference value between adjacent bit outputs, and TH ₁ and TH ₂ are the first and second thresholds, respectively, and Me is the memory.

The operation of this embodiment will be described with reference to FIG. First, the difference value K between adjacent bit outputs is calculated from K = D _{i + 1} −D _i from the first bit, which is the end of the line sensor 2, to determine whether the difference value K is positive or negative.

Here, when the difference value is positive, the difference value K is integrated to obtain the integrated value S as S = S + K, and it is determined whether the value of the flag Fl is 0 or 1. When the value of the flag Fl is 0, the bit position i is stored in the memory Me, the value of the flag Fl is set to 1, and the bit position i is incremented by 1. On the other hand, when the value of the flag Fl is 1,
Increase the bit position by one.

That is, when the adjacent bit output increases, the bit position i is stored.

When the difference value is not positive, the difference value K is integrated to obtain the integrated value S as S = S + K, and the magnitude relationship between the integrated value S and the first threshold value TH ₁ is determined. When the integrated value S is smaller than the first threshold value TH ₁ , the flag Fl is set to 0 and the bit position i is incremented by 1. On the other hand, when the integrated value S is not smaller than the first threshold value TH ₁ , the bit position is incremented by 1.

That is, when the adjacent bit output decreases or is the same and the integrated value S does not exceed the threshold value TH ₁ , the flag Fl becomes 0, and the memory stored before that becomes a state in which the memory can be updated. In the case where the matching bit output decreases or is the same and the integrated value S exceeds the threshold value TH ₁ , the bit position is updated as it is.

With the above operation, when the integrated value S is larger than the threshold value TH _{1, the} bit position stored in the memory Me remains unchanged, but when it is smaller than the threshold value TH ₁ , the memory Me stores the difference. When the value K becomes positive, it is updated with the new bit position.

Further, it is determined whether the integrated value S is larger or smaller than the threshold value TH ₂ , and if it is smaller, the difference value K of the next bit position is obtained, and if it is larger, the bit position i stored in the memory Me is determined. The edge position is finally detected.

The present invention has been described above. In the second flow chart, the bit position i is described starting from the first bit. This is to detect the same edge in the reverse direction from the maximum bit position of the line sensor. By doing so, it is possible to detect both ends of the edge.

(Effects of the Invention) As described above, according to the present invention, the position where the change in the line sensor output appears is determined to be the edge, and therefore even when the cross section of the edge gradually changes like a sphere. The advantage is that the position of the edge can be detected accurately and there is no error.

[Brief description of drawings]

FIG. 1 is a block diagram of an edge position detecting apparatus showing an embodiment of the present invention, FIG. 2 is a flow chart of an edge detecting algorithm, FIG. 3 is a block diagram of a conventional edge position detecting apparatus, FIGS. The figure shows the relationship between the line sensor output and the determination threshold value. 1 ... DUT, 2 ... Line sensor, 3 ... Multiplexer (MPX), 4 ... Sample and hold circuit (S /
H circuit), 5 ... Analog-digital conversion circuit (A / D conversion circuit), 6 ... Subtractor, 7, 8, 9, 19, 20 ... Memory, 13 ... Microcomputer (CPU), 14 ... Data bus, 15 ... differentiator, 16 ... integrator, 17, 18 ... comparator.

Claims (1)

[Claims] 1. A line sensor for scanning an object to be measured, a differentiator for sequentially detecting a difference between outputs at adjacent scanning positions on the line sensor along a scanning direction, and an integrator for integrating the difference. A storage unit that stores a scanning position determined as an edge, scans the DUT from one end of the line sensor toward the other end, and when the differentiation result by the differentiator is positive, , The scanning position is stored in the storage means as the edge, and when the differentiation result by the differentiator is negative or 0, if the integration result by the integrator is not less than the first threshold value, If the result of integration by the integrator is less than or equal to the first threshold value while holding the stored contents, a new scanning position at which the differential result is positive is stored in the storage means again, and the new scanning position by the integrator is stored. Integration An edge detection position, characterized in that when the result exceeds a second threshold value that is larger than the first threshold value, the scanning position stored in the storage means is the edge.