JPS594911B2 - Nijigen pattern Niyuriyokusouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for faithfully inputting a two-dimensional pattern to a photodiode array that converts a bright and dark image into an electrical signal.

A photodiode array has tens to thousands of photoelectric conversion elements arranged in a straight line, and by sequentially extracting the photocharge from each element in synchronization with a clock pulse, it converts bright and dark images in a straight line into electrical signals. The scan is started by a start pulse.

An example of a method for inputting a two-dimensional pattern using a photodiode array is shown in FIG. In the figure, 1 is a photodiode array, 2 is an electric circuit such as a photodiode array drive circuit and a binarization circuit, 3 is a microscope, and 4 is an illumination device, which is placed on a table 6 by an objective lens 5. The pattern on the object to be inspected 7 is projected onto the light receiving surface of the photodiode array 1 as a real image. 8 is table 6
The feed screw/nut part 9 is a motor that drives the table 6 at a constant speed.

When the table 6 is moved by the mono 9 at a constant speed in a direction perpendicular to the scanning direction of the photodiode array, the pattern projected onto the photodiode array 1 also moves at a constant speed, and the photodiode array 1 The pattern is sequentially converted into an image signal. The scanning of the photodiode array is started by a start pulse, but in the conventional method, the start pulse is obtained at regular intervals by measuring a clock pulse. For example, when the photodiode array has N bits, In this case, the interval between start pulses was N+α clock period, and was constant in time.

Therefore, if the table 6 is moved at an appropriate constant speed, the pattern will be input faithfully, but if the speed of the table 6 changes due to fluctuations in the speed of the motor 9, etc., the vertical and horizontal patterns will be changed. The ratio will no longer be constant. In other words,
Even if the pannon is circular, due to the slow speed of the table 6, the input pannon will become a vertically long or horizontally long rectangular shape. In order to input a faithful pattern, it is difficult to accurately adjust the speed of the table 6 and to adjust the electrical and mechanical systems so that it can move at a constant speed. That is, the present invention uses a photodiode array to input a pattern by moving the relative position of the pannon and the photodiode array, measures the amount of movement, and scans the photodiode array every fixed amount of movement. This provides a device for accurately inputting patterns.

In addition, when converting the output of a photodiode array into a binary value, the output changes depending on the scanning time interval, so
The present invention provides an apparatus that measures the scanning interval by counting the clock pulses of the photodiode array, changes the threshold of the comparator according to the measured value, and performs binarization using the appropriate threshold.

t ′ Embodiments of the present invention will be described with reference to the drawings.

The mechanical configuration of the Pannon input may be the configuration shown in FIG. 1, similar to the prior art.

The relationship between the start of scanning and the amount of movement of the pattern is determined by how many μm of the pattern corresponds to one pixel of the photodiode array 1, and this is determined by the magnification of the objective lens 5. Now, if the magnification of the objective lens 5 is determined so that one pixel of the photodiode array 1 corresponds to Lμm of the path, the photodiode array 1 is scanned every time the path moves by Lμm. and the aspect ratio is "1"
” and can input Panong faithfully. FIG. 2 shows an electrical configuration according to an embodiment of the present invention.

10 is a photodiode array; 11 is a video amplifier that amplifies the output of the photodiode array 10; 12
13 is a pulse generator that generates a lock pulse 21 necessary for driving the photodiode array 10; 14 is a displacement measuring device 12 for the table 6;
This is a synchronization circuit that synchronizes with the clock pulse 21 and generates the start pulse 22 necessary for scanning the photodiode array 10 from the output of the photodiode array 10.

15 is the interval between the start pulses 22 and the clock pulses 21.
16 is a memory circuit that temporarily stores the contents of the counter 15, 17 is a digital-to-analog converter that converts the contents of the memory circuit 16 into analog, and 18 is a converter that converts the output of the digital analog converter to an appropriate value. It is an attenuator that attenuates.

19 is a fixed threshold circuit, and 20 is an analog comparator, which has the function of binarizing the output of the video amplifier 11 using a voltage obtained by adding the output of the attenuator 18 and the output of the fixed threshold circuit 19 as a threshold.

Next, the apparatus of the present invention will be described in more detail with reference to an example in which a rotary encoder is used as the movement amount measuring device 12. As mentioned above, it is assumed that it is necessary to output the snort pulse 22 for scanning the photodiode array 1 every time the pattern moves by L μm.

Assuming that the output pulses 26 of the rotary encoder are P per rotation, the amount of movement of the table 6 per rotation of the rotary encoder must be configured so that P>(Lμm.Therefore, the diameter is P× By attaching a pulley of N/πμm to the shaft of the rotary encoder, it is possible to issue a start pulse 22 every time the table 6 moves by Lltm.A synchronous circuit generates the start pulse 22 from the output 26 of the rotary encoder and the clock pulse 21. 14 specific examples are shown in FIG. 3-a, and a time chart of signals of each part of the circuit is shown in FIG. 3-b.

In FIGS. 3-A and 3-b, first, the rotary encoder output 26 is synchronized with the clock pulse 21 using the D-type flip-flop 23. Furthermore, the D-type flip-flop 24 delays the output 27 of the D-type flip-flop 23 by one clock, and the exclusive OR circuit 25 takes the exclusive OR of the outputs 27 and 28 of the D-type flip-flops 23 and 24, thereby generating the start pulse 22. can be obtained.
With such a configuration, it is possible to obtain the start pulse 22 when the output 26 of the output 26 rises, but of course it is also possible to output the start pulse 22 only when the output 26 rises or falls. In that case, use a rotary encoder with twice the number of output pulses, or use a rotary encoder with 6 output pulses per revolution.
The amount of movement can be halved. When the moving speed of the table 6 changes, the time interval of the start pulse 22 changes accordingly.

If the time intervals of the start pulses 22 are different, the output of the photodiode array 10 will vary as shown in FIG. That is, the output of the photodiode array 10 is
When the time interval between the start pulses 22 is short, the video signal has a waveform shown by a solid line 29, and when the time interval is long, the video signal has a waveform shown by a dotted line 30. In this way, as the time interval of the start pulse 22 becomes longer, the video signal changes from 29 to 30, so when these signals are binarized by the analog comparator 20, the optimal binarization level is the threshold value 31. The threshold value drops from 32 to 32.
Therefore, in order to always binarize the output of the photodiode array 10 at the optimal level, an analog comparator 1 it is necessary.
The value of the fixed threshold circuit 19 added to the start pulse 2
You can change it according to the interval of 2. Therefore, the counter 15 in FIG. 2 always counts the clock pulses 21,
It is configured to be cleared by the start pulse 22, and the contents of the counter 15 immediately before being cleared are stored in the memory circuit 17 until the next snort pulse comes. This is repeated every time the start pulse comes, and the output of the memory circuit 17 is always converted into analog by the analog-to-daisymel converter 17. If the voltage converted to analog is attenuated to an appropriate value and added to the output voltage of the fixed threshold circuit 19, and that value is used as a threshold, the analog comparator 20 can always perform binarization at an optimal level. Note that the analog comparator 20 shown in FIG. Input to one side (one terminal),
The output voltage of the video amplifier 11 is input to the other input terminal (10 terminal), the two voltages are compared, and the comparison result is obtained as a binary output of the 7-analog comparator 20. With the above processing, it is possible to always input a pattern faithfully even if the table movement speed changes.

In this embodiment, a rotary encoder is used as the movement measuring device, but a linear encoder, a magnescale, etc. can also be used.

Further, although a configuration has been described in which the pattern on the object to be inspected 7 is moved by moving the table 6, it is also possible to conversely be configured to move the phototransistor array with respect to the pattern. As described above, according to the present invention, a pattern can be accurately and faithfully input into a photodiode array regardless of the relative moving speed of the pattern and the photodiode array.

Furthermore, since the threshold value of the binarization level is changed according to the scan start interval corresponding to the moving speed, accurate conversion into a binarized electric signal is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a general mechanical configuration of an apparatus for inputting a photodiode array dimensional pattern. FIG. 2 is a block diagram showing the electrical configuration of the input device according to the present invention. FIG. 3-a is a circuit diagram showing a specific example of the configuration of the synchronous circuit. FIG. 3-b is a time chart of signals of each part of the circuit shown in FIG. 3-a. FIG. 4 is a diagram for explaining the relationship between changing the threshold value of the binarization level of the video signal. Explanation of symbols, 1... Photodiode array 2... Electric circuit, 3... Microscope, 4... Lighting device, 5...・Objective lens, 6...Table, 7...Object to be inspected, 8...Feed screw, 9...Motor, 1
0...Photodiode array, 11...
...video amplifier, 12...mobile measuring instrument, 1
3...Pulse generation circuit, 14...Synchronization circuit, 15...Counter, 16...Memory circuit, 17...Digital/analog converter,
18... Attenuation name, 19... Fixed threshold circuit, 20... Analog comparator, 2
1... Clock pulse, 22... Start pulse, 23, 24... D-type flip-flop, 25... Exclusive OR circuit, 26...
...mouth-to-shio encoder output, 27, 28...
- Flip-flop output, 29, 30... video signal, 31, 32... comparator threshold.

Claims (1)

[Claims] 1 Photodiode that converts bright and dark images into electrical signals
A device for inputting a two-dimensional pattern into an array, the device comprising means for moving the relative position of the two-dimensional pattern and the photodiode array in the scanning direction of the photodiode array and in the orthogonal direction; A two-dimensional pattern input device comprising means for measuring the amount of movement of the relative position between a pattern and a photodiode array, and means for starting scanning of the photodiode array every time the relative position moves by a certain amount. , a circuit for measuring the time interval of the start of scanning of the photodiode array, converting the start pulse inputted at each time interval of the start of scanning obtained by the measurement in the circuit into analog, and converting the start pulse into an analog voltage value; Add the constant voltage obtained from the fixed threshold circuit,
an analog comparator circuit that compares the added voltage with the output voltage of the photodiode array as a threshold and obtains a binary output; the threshold of the analog comparator that compares with the output voltage of the photodiode array is the threshold of the start pulse. A two-dimensional pattern input device characterized in that it is configured so that it can be changed according to.