JPS6134408A - Size measuring method - Google Patents

Abstract

PURPOSE:To eliminate errors in size measurement due to floating dust, by detecting the number of pulses of a binary-coded signal corresponding to a projected area, and computing the diameter of a material under examination based on the logical output when the number of pulses is equal to the number of projected materials under examination. CONSTITUTION:Dust D other than a material under examination S is floating between an optical system 11 and a CCD12. S and D are projected on the CCD 11. An amplified picked-up image signal (a) is imparted to a comparator circuit 14 and compared with a threshold value Vth from a threshold-value setting circuit 15. An offset pulse (c), which has the pulse width corresponding to the projected area of the CCD12, is imparted to an AND gate 16 from a synchronization pulse generating circuit 18. As a result, a binary-coded signal (d), from which dummy pulses are offset, is outputted from the AND16. After the amplification in a driver 19a, the signal is transmitted to an operating part 30. The number of pulses of the binary-coded signal is detected. When the number is equal to the number of the projected materials under examination, the diameter of the material under examination is computed based on the logical output.

Description

Detailed Description of the Invention (a) Industrial Application Field This invention binarizes an analog imaging signal of an imaging means on which a material to be inspected is projected, and converts the binarized signal and a reference pulse into a logical output. The present invention relates to a dimension measurement method for calculating the diameter of a material to be inspected based on the diameter of the material to be inspected.

(b) Prior Art This type of dimension measurement method performs dimension measurement based on irradiating a material to be inspected with parallel light and detecting its shadow with an imaging device. Therefore, if dust such as scale peeled off from the surface of the inspected material exists between the optical system and the image sensor, its shadow will be detected by the image sensor. As a result, a problem arises in that the dimension measurement result of the inspected material becomes larger than the actual dimension.

(c) Purpose This invention aims to provide a dimension measuring method that can accurately measure dimensions of a material to be inspected by eliminating errors in dimension measurement results due to floating dust as described above.

(D) Structure The dimension measuring method according to the present invention binarizes the analog imaging signal of the imaging means on which the inspected material is projected, and measures the inspected material based on the logical output of the binarized signal and the reference pulse. A dimension measurement method for calculating the diameter, in which the number of pulses of the binarized signal corresponding to the projection area is detected, and when the number is equal to the number of objects to be inspected to be projected, the number of pulses is calculated from the logic output. By calculating the diameter of the inspection material, the influence of dust floating between the optical system and the imaging means on the measurement results is eliminated.

(E) Embodiment FIG. 1 is a block diagram schematically showing the configuration of a dimension measuring apparatus using an embodiment of the dimension measuring method according to the present invention.

This dimension measuring device includes a detection section 10 for obtaining a binary signal of the material S to be inspected, and a detection section 10 that is provided apart from the detection section 10 and measures the diameter of the material S to be inspected based on the transmitted binary signal and the like. It consists of an arithmetic processing section 30 that provides data for calculating .

First, the configuration of the detection section 10 will be explained.

Reference numeral 11 denotes an optical system that irradiates the inspected material S with parallel light rays.

Reference numeral 12 denotes a charge coupled device (CCD) as an imaging means on which the inspected material S is projected. The optical system 11 and the CCD 1
2 is configured to rotate around the material S to be inspected.

Then, the CCD 12 scans the projected image, for example, 30 times,
An imaging signal is output for each scan.

13 is an amplifier that amplifies the imaging signal of the CCD 12.

14 is a comparison circuit to which the amplified image signal a is given as one input.

15 is a threshold setting circuit for setting the threshold value vth of the comparison circuit 14;

16 is an AND gate to which the output of the comparison circuit 14 is applied as one input.

Reference numeral 17 denotes a clock pulse generation circuit that provides the transfer timing of the CCD 12, etc.

18 is given a clock pulse, CCD 12, AND
This is a synchronization signal generation circuit that provides a predetermined synchronization pulse to the gate 16 and the like.

19a and 19b are drivers for transmitting predetermined signals to the arithmetic processing section 30, which is usually provided apart from the detection section 10. The driver 19a amplifies and outputs the binary signal d which is the output of the AND gate 16, and the driver 19b amplifies and outputs the scanning synchronization pulse e given from the synchronization signal generation circuit 18. Firstly,
The configuration of the arithmetic processing section 30 will be explained.

31a and 31b are receivers for receiving each signal sent from the detection unit 1o.

32 is a counter that counts the number of pulses of the received binary signal d.

33 is a reference pulse generation circuit. In relation to the pixel size of the CCD 12, the length corresponding to one reference pulse is predetermined.

34 is an AN to which the binary signal d and the reference pulse f are applied.
This is the D gate.

35 is a counter to which the output of the AND gate 34 is applied.

36 is a launch circuit that latches the count value of the counter 35.

Reference numeral 37 denotes an adder circuit that sequentially adds the outputs of the latch circuit 36 and stores the added value.

38 is based on the output of the counter 32 and adds 2 to the binary signal d.
A counter that counts the number of scans that contain more than one pulse.

39 is a counter 32, a latch circuit 36, and an addition circuit 37.
, counter 38 etc. IIJ! This is a control circuit that performs II.

Next, the dimension measuring method according to this embodiment will be explained by explaining the operation of the dimension measuring apparatus having the above-described configuration. FIG. 2 shows an operation waveform diagram of each part shown in FIG. 1.

It is assumed that there is dust floating between the optical system 11 and the CCD 12 in addition to the inspected material S. Therefore, the inspected material S and dust are projected onto the CCD 12.

The amplified imaging signal a of the CCD 12 is given to a comparison circuit 14. In FIG. 2(a), sl is a signal caused by the material to be inspected S, s2 is a signal caused by a single dust, and s3 is a dummy signal.

In the comparison circuit 14, the image signal a is compared with a threshold value vth given from a threshold setting circuit 15. The comparison output b is applied to an AND gate 16. AND
The gate 16 is supplied from the synchronization pulse generation circuit 18 in the same figure (C
) is given an erasing pulse C having a pulse width corresponding to the projection area of the CCD 12. As a result, the AND gate 16 outputs a binary signal d from which the dummy pulse has been removed, as shown in +d) in the figure. This binary signal d is amplified by the driver 19a and then transmitted to the arithmetic processing section 30.

Further, the scanning synchronizing pulse e generated from the synchronizing pulse generating circuit 18 is amplified by the driver 19b and then transmitted to the arithmetic processing section 30.

The binarized signal d received by the receiver 31a of the arithmetic processing section 30 is given to the counter 32 and the AND gate 34. The AND gate 34 provides a logical product output of the binary signal d and the reference pulse f to the counter 35. Therefore, the count value of the counter 35 is
This data indicates the length of the shadow projected on the object (hereinafter referred to as "measurement data"). This measurement data is stored in the latch circuit 36.
given to. The latch circuit 36 has a scan synchronization pulse j(
(same as e) is input, the measurement data is held and given to the addition circuit 37. After that, counter 35
The measurement data of is reset by the control circuit 39.

On the other hand, when the binarized signal d contains two or more pulses, the counter 32 detects II! As shown in (Ulh), a data invalidation pulse g is output in synchronization with the rising edge of the second pulse of the binarized signal d. This pulse g is detected by the counter 38
and the control circuit 39. The counter 38 counts the number of input invalid data pulses g.

Control times v given data invalid pulse g! 139 is
A reset pulse h is applied to the latch circuit 36.

As a result, the measurement data held in the launch circuit 36 is erased. Further, in this case, since the addition pulse i is not issued from the control circuit 39 to the addition circuit 37, the addition circuit 37 excludes the launched measurement data from the addition calculation target. In this way, measurement data when the binarized signal contains two or more pulses is ignored.

Conversely, if the binary signal contains only one pulse, it means that no dust is floating between the optical system 11 and the CCD 1'2. In this case, the control circuit 3
9 outputs an addition pulse i as shown by a broken line in the figure (il) to the addition circuit 37.As a result, the measurement data held in the latch circuit 36 at this time is output to the addition circuit 37.
It is added to the measurement data stored in . In this way, only the measurement data when the binarized signal includes one pulse are sequentially added and stored in the adding circuit 37.

The above-described operation is performed every time the CCD 12 scans. As mentioned above, the CCD 12 scans a predetermined number of times (for example, 30
times) is carried out. The number of scans is preset in the control circuit 39. The control circuit 39 is given a scan synchronization pulse as shown in tJ) (the time axis of the scan synchronization pulse shown in 9te in the same figure is shortened), and counts the number thereof. When the number of input scan synchronization pulses j reaches the preset number, the control circuit 39 gives a signal k to the next stage microcomputer (not shown) to inform it that data can be read i. When the data reading time t has elapsed after the signal k is issued, the control circuit 39 starts the addition circuit 3
7 and counter 38 with a reset pulse m. Furthermore, each time the control circuit 39 is given a scan synchronization pulse,
A reset pulse is applied to the counter 32 to erase its contents for each scan.

The microcomputer calculates the sum of the measurement data stored in the addition circuit 37 of the arithmetic processing section 30 and the counter 3.
Read each measurement value of 8. The counter 38 displays the number of scans that have not been added to the adding circuit 37.

This microcomputer subtracts the count value of the counter 38 from the predetermined number of scans (for example, 30 times), and divides the added value of the adder circuit 37 by that value.

For example, if the influence of floating dust occurs twice out of 30 scans, the count value of the counter 38 will be 2. Therefore, the microcomputer divides the added value of the adder circuit 37 by 28.

In this way, the average value of the data excluding measurement data obtained by scanning when dust was floating is calculated. This average value and the length corresponding to each reference pulse, for example, 13 μm, which corresponds to the length of one pixel.
), the diameter of the material S to be inspected is determined.

Note that the means for binarizing the image pickup signal a is not limited to the means described in the above embodiment. For example, it is also possible to obtain a binarized signal by differentiating the image signal a, processing the differentiated waveform appropriately, and then applying it to a flip-flop. By doing so, it is possible to avoid the influence of fluctuations in the DC level included in the image pickup signal a.

Further, in the above embodiment, since there was one material S to be inspected, if the number of pulses included in the binarized signal was two or more, the measurement data was ignored. Therefore, it goes without saying that if the number of materials S to be inspected is two, and the number of pulses included in the binarized signal is three or more, the measurement data will be ignored.

(F) Effect: In the dimension measuring method according to the present invention, when the number of pulses of the binary signal is greater than the number of inspected materials S, the measurement data obtained by scanning is ignored, and other measurement data are ignored. The diameter of the inspected material S is calculated from

Therefore, according to the present invention, it is possible to prevent errors in measurement results due to dust floating between the optical system and the imaging means, so that highly accurate dimensional measurements can be performed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram schematically showing the configuration of a dimension measuring device using an embodiment of the dimension measuring method according to the present invention, and Fig. 2 shows an operation waveform diagram of each part shown in Fig. 1. . 10... Detection unit, 11... Optical system, 12... CC
D, 14... Comparison circuit, 30... Arithmetic processing section, 32
．． 35.38...Counter, 33...Reference pulse generation circuit, 34...AND gate, 37...Addition circuit, 39...Control circuit.

Claims (1)

[Claims] (1) In a dimension measurement method in which the analog imaging signal of the imaging means on which the inspected material is projected is binarized, and the diameter of the inspected material is calculated based on the logical output of the binarized signal and a reference pulse, the projection area A dimension characterized in that the number of pulses of the binarized signal corresponding to the digitized signal is detected, and when the number is equal to the number of the inspected materials to be projected, the diameter of the inspected material is calculated from the logical output. Measuring method.