JPS6134407A - Size measuring method - Google Patents

Abstract

PURPOSE:To eliminate measuring errors due to dust, by removing a signal having a specified width from a signal based on the output of an image sensor means, to which the image of a material under examination is projected, adding the removed signal to the measured value of the material under examination, and computing the diameter of the material under examination based on the added value. CONSTITUTION:Dust D is floating other than a material under examination between an optical system 11 and a CCD12. Therefore S and D are projected on the CCD12. A picked up image signal (a) of the CCD12, which is amplified, is imparted to a comparator circuit 14 and compared with a threshold value Vth of a threshold setting circuit 15. The compared output (b) is imparted to an AND gate 16. An offset pulse (c), which has the pulse width corresponding to the projected area of the CCD12, is imparted to a gate 16 from a synchronization pulse generating circuit 18. A binary coded signal (d), from which dummy pulse is offset, is outputted. A counter circuit 19 counts clock pulses during the ''H'' period of the signal (d). When the predetermined number of pulses (preset value N) is counted, ''H'' is outputted. The preset value N is determined by the size of the dust D.

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 measurement result of the dimension of the material to be inspected is 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) Configuration The dimension measuring method according to the present invention removes a signal of a certain width from a signal based on the output of an imaging means on which the inspected material is projected, and the measured value of the inspected material that has become smaller due to this. By adding the removed signals and calculating the diameter of the inspected material from this added value, errors in the measurement results due to dust are removed.

(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.

, 11 is an optical system that irradiates parallel light beams onto the material S to be inspected.

Reference numeral 12 denotes a charge coupled device (COD) as an imaging means on which the inspected material S is projected.

Reference numeral 13 denotes an amplifier that amplifies the imaging signal of the CCDI 2.

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.

17 is a clock pulse generation circuit.

18 is a scanning synchronizing pulse to the CCD 12 and an erasing pulse C
This is a synchronous pulse generation circuit that provides the AND gate 16 with the following.

19 is a counter that counts the number of clock pulses input to the C0P terminal. This counter 19 performs counting while 'HJ' is input to the C terminal, and erases the counted value when 'LJ is input to the C terminal. The counter 19 outputs "HJ" when a predetermined number of pulses (hereinafter referred to as the set value N) has been passed.The set value N corresponds to the size of the floating dust and one clock pulse. For example, assume that the maximum length of dust is 130 μm and one clock pulse corresponds to a pixel unit length of 13 μm. " is set.

20 is a counter output holding circuit. When this counter output holding circuit 20 receives rH from the counter 19,
An output holding signal is given to the counter 19.

21 is an AND gate to which the output signal e of the counter 19 and the clock pulse are applied.

Next, an embodiment according to the present invention will be explained through an explanation of the operation of the apparatus having the above-described configuration. FIG. 2 shows operating waveforms of each part of the device shown in FIG. 1.

It is assumed that there is dust floating between the optical diameter 11 and the CCD 12 in addition to the inspected material S. Therefore, the inspected material S and dust are projected onto cc'D12.

The amplified imaging signal a of the CCD 12 is given to a comparison circuit 14. In FIG. 2 (al), Sl is a signal caused by the material to be inspected S, S2 is a signal caused by 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 is applied to AND gate 16. AND
16 is from the - period pulse generation circuit 18 in the same figure (e).
) 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 as shown in FIG. .

On the other hand, the counter circuit 19 counts clock pulses while the binary signal d is "Hj".
During T1, when the first pulse of 1 is input, the number of clock pulses counted is less than or equal to the number (for example, 10) set in advance in the counter 19. In this case, the counter 19 does not output 'HJ. Then, the count value in the counter 19 is erased when the first pulse falls.

Next, a case will be explained in which the second pulse of the binarized signal d is input.

Since the second pulse corresponds to the material S to be inspected, its pulse width T2 is sufficiently wide. Therefore, while this pulse is input, the number of clock pulses counted becomes greater than the set value N. Therefore, the counter 19 outputs 'HJ. The counter output holding circuit 8, which has been given this output rH, provides an output holding signal to the counter 19. As a result, the counter 19 outputs rH until the second pulse falls.

The third pulse, like the first pulse, is based on dust and has a narrow pulse width T3. Therefore, the counter 19 does not output 'HJ.

Thus, as shown in FIG. 2(e), the pulses due to dust are eliminated from the output of the counter 19.

Then, the pulse based on the inspected material S is shortened by the time width Tn corresponding to the set value N and is output.

The output e of the counter 19 is applied to an AND gate 21, and as a result, an AND output of this and a clock pulse is provided. This logic output is given to a next-stage microcomputer (not shown).

The microcomputer adds the set value N to the number M of pulses included in this logic output. Thereby, the time Tn shortened by the operation of the counter 19 is compensated for, and measurement data corresponding to the actual diameter of the material S to be inspected is obtained. Then, the diameter of the material S to be inspected is calculated by multiplying this addition result M+N by the length per clock pulse (for example, 13 μl11).

Note that the means for binarizing the image signal is not limited to that described in the above embodiment. For example, it is also possible to obtain a binarized signal by differentiating the image pickup signal a, appropriately processing this differentiated waveform, 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.

(f) Effects The dimension measuring method according to the present invention removes a signal of a certain width related to the size of dust from a signal based on the output of an imaging means on which a material to be inspected is projected.

Therefore, according to the present invention, it is possible to prevent the influence of dust that causes errors in the dimensional measurement results, and thus it is possible to improve the dimensional measurement accuracy.

[Brief explanation of the drawing]

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, and FIG. 2 shows an operation waveform diagram of each part shown in FIG. 1. 11... Optical system, 12... CCD, 14... Comparison circuit, 16.21... AND gate, 19... Counter, 20... Counter output holding circuit. Patent applicant Shimadzu Corporation Representative Patent attorney Takaharu Ohnishi Figure 1 Figure 2

Claims (1)

[Claims] (1) While removing a signal of a certain width from the signal based on the output of the imaging means on which the inspected material is projected, the removed signal is added to the measurement value of the inspected material that has become smaller due to this, and this addition A dimension measurement method characterized by calculating the diameter of a material to be inspected from the results.