JPH0429047B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic focusing device that automatically adjusts the focus and forms an image on an imaging plane when optically detecting a detection area.

Such an automatic focus adjustment device is necessary for reading a detection area provided on an article using an industrial television camera or the like in logistics sorting, etc., and automatically sorting the article. In other words, if the detection area provided on the article consists of multiple linear parts coded to indicate the sorting destination, such as a so-called bar code, if the detection area is not accurately read, the sorting will not be possible. Unable to obtain information and automatic sorting becomes difficult.

An object of the present invention is to provide an automatic focus adjustment device that accurately reads an image of a detection area by automatically adjusting the focus.

In the present invention, a pair of belt-shaped labels 6a and 6b are arranged on the surface of an article 1 along a predetermined direction with an interval d, and there is a clear contrast between these labels 6a and 6b and their background. detection area 2
is formed, and an image of the detection area 2 of the object is transmitted to the photoelectric conversion means.
An image is formed by an image forming means 5 whose focal length is adjustable, and the predetermined direction is set in the direction of a horizontal scanning line; A drive device 23 that moves in one direction so that the distance to the photoelectric conversion means is changed and the focus is adjusted, and a binary drive device that binarizes the video signal of one horizontal scanning line from the photoelectric conversion means of the television camera 3. conversion circuit 8
, an oscillator 9 that generates pulses, and a oscillator 9 that derives pulses from the pulse oscillator 9 in response to the outputs of the binarization circuit 8 and the pulse oscillator 9.
1AND gate 10 and a first inverting circuit 1 that inverts the output of the binarization circuit 8
1, and is reset by a horizontal synchronizing signal from the television camera 3, and after being reset, the first inverting circuit 11 is reset in response to the output of the first inverting circuit 11.
The output of the first flip-flop 12 is set by receiving one of the predetermined rising or falling waveforms of the output, and then receiving the other waveform, and the output of the binarization circuit 8. and the first flip-flop 1
The output of the second AND gate 13 is reset by the horizontal synchronizing signal from the television camera 3, and after being reset, the second AND gate
In response to the output of the gate 13, one of the predetermined rising or falling waveforms of the output of the second AND gate 13 is received, and then either of the other waveforms is received, thereby setting the second AND gate 13. A second flip-flop 14, a second inversion circuit 15 for inverting the output of the second flip-flop 14, an output of the first AND gate 10, an output of the first flip-flop 12, and an output of the second inversion circuit 15 are provided, A third AND gate 16 that derives the pulse output from the pulse oscillator 9 via the first AND gate 10 during the interval d, a counter 17 that counts the pulses from the second AND gate 16, and a vertical synchronization signal from the television camera 3. in response to a register 19 that stores the counted value from the counter 17 of the previous screen; and in response to the outputs of the counter 17 and the register 19, the current counted value and the one horizontal scan of the previous screen. A subtracter 20 that subtracts the absolute value |Δd| of the difference from the counted value by the line, and a constant setter 22 that sets a predetermined constant ΔdS.
And the output of the absolute value |Δd| from the subtractor 20 is
a comparator 21 that stops the drive device 23 when the constant ΔdS set by the constant setter 22 is less than the constant ΔdS;
An automatic focus adjustment device comprising:

FIG. 1 is a perspective view of one embodiment of the present invention.
A detection area 2 provided on the article 1 is read by an industrial television camera 3. This item 1
is conveyed in the conveyance direction 4 by a conveyor or the like through the front of the industrial television camera 3. The industrial television camera 3 includes an imaging means 5 including a convex lens, etc.
and a photoelectric conversion means such as a vidicon which uses the imaging means 5 to convert the image of the detection area 2 into an electrical video signal.

FIG. 2 is a front view of the detection area 2. FIG. This detection area 2 consists of a pair of strip-shaped (bar) marks 6a and 6b (generally indicated by reference numeral 6) along a predetermined direction (that is, horizontal direction in this embodiment) on the surface of the article 1. ) are arranged as indicated by diagonal lines, and it is considered that the distance between the designated markers 6a and 6b is a constant distance d. The sign 6 and the surface of the article 1 serving as its background are color-coded in advance to provide a clear contrast. In this embodiment, for simplicity of explanation, it is assumed that the sign 6 is black and the background 1 is white.

FIG. 3 shows an image obtained by an industrial television camera 3. FIG. If the industrial television camera 3 is out of focus as shown in Fig. 3, the sign 6
The boundary between images 6a1 and 6b1 of a and 6b is unclear. On the other hand, when the television camera 4 is in focus as shown in FIG.
The boundaries between the images 6a2 and 6b2 of a and 6b are clear, and the distance d between them is also clear. That is, the detection area is imaged with an industrial television camera, and the distance d between the markers is determined from this image. The distance d has the property of being maximum when the object is in focus.

FIG. 4 shows the imaging means 5 of the industrial television camera 3.
FIG. 3 is a diagram showing the relationship between the position of the sign and the interval between the signs calculated from the image of an industrial television camera. As a result, if the position of the imaging means 15 corresponding to the point d3 where the interval between the markers is maximum is f, then the imaging means 5 is moved to f
You can focus by positioning it.
To position the imaging means 5 at f, the imaging means 5
While moving from the front end to the rear end, the distance d between the signs is measured using video signals obtained from time to time, and the imaging means 5 is set at the point where the amount of change Δd of the detected value of the distance d with respect to time is minimum. Just stop it.

FIG. 5 is a control block diagram in this embodiment. The video signal S1 from the photoelectric conversion means of the industrial television camera 3 is applied to the binarization circuit 8, and the video signal of one horizontal scanning line indicated by reference numeral 7 in FIG. 3 is binarized. In this binarization operation, 1
The video signal of one horizontal scanning line is binarized using a predetermined threshold value (see FIG. 6, which will be described later). As a result, parts 6a and 6b (black) corresponding to the marker part
For example, is determined to be a logic "0", and the background (white) is determined to be a logic "1". Distance between signs d
is calculated by the calculation circuit 25. A pulse oscillator 9 is provided to sample the output S2 of the binarization circuit 8. The output pulse S3 of the pulse oscillator 9 and the output S2 of the binarization circuit 8 are input to an AND gate 10, and as a result, a sampling pulse output of a binarized signal is obtained. Flip-flops 12 and 14 control the counting period of a counter 18 that counts pulses occurring during a period corresponding to the interval d. The output S2 of the binarization circuit 8 is input to a flip-flop 12 via an inverter 11. As a result, flip-flop 12
is set under the condition that the inverted signal of the binarized signal is at a high level. The output S5 of flip-flop 12 is input to AND gate 13. AND
The other input of the gate 13 is the output S of the binarization circuit 8.
It is 2. The output of AND gate 13 is input to flip-flop 14. As a result, the flip-flop 14 outputs the output S5 of the flip-flop 12.
is at a high level, and the output S of the binarization circuit 8
2 is set by a high level condition.
The output S5 of the flip-flop 12, the signal obtained by inverting the output S6 of the flip-flop 14 by the inverter 15, and the output of the AND gate 10 are input to the three-input AND gate 16. As a result, the output S7 of the AND gate 16 provides a sampling pulse with a period corresponding to the interval d.

FIG. 6 is a time chart showing the above signal relationship. FIG. 6 1 shows the video signal S1, and FIG. 6 2 shows the output S2 of the binarization circuit 8.

FIG. 6 2 shows the output waveform of the inversion circuit 11.
The flip-flop 12 is reset by the horizontal synchronizing signals q1 and q2 (see FIG. 6, 1) obtained from the television camera 3 in the synchronizing signal separation circuit 24, and after being reset, the flip-flop 12 is reset in response to the output of the inverting circuit 11. , the rising waveform p1 of the output of the inverting circuit 11 is received, and then the falling waveform p2 is received, thereby setting the signal.

Further, the flip-flop 14 receives a horizontal synchronizing signal q
1, q2, and after being reset, the rising waveform of the AND gate 13 corresponding to the rising waveform p11 of FIG. AND
It is set by receiving the falling waveform from gate 13. In another embodiment, the flip-flops 12 and 14 are configured to be reset by receiving a falling waveform and then receiving a rising waveform after being reset, and to set the flip-flops in response to this. It is also possible to implement the invention with slight changes in other components.

6.3 shows the output S3 of the pulse oscillator 9, FIG. 6.4 shows the output S4 of the AND gate 10, FIG. 6.5 shows the output S5 of the flip-flop 12, FIG. 6 shows the output S6 of the flip-flop 14, and FIG. 6.7 is AND
This is the output S7 of the gate 16.

The output S7 of the AND gate 16 is
As a result, the number of pulses corresponding to the distance d between the markers on one horizontal scanning line scanning the markers is counted. The register 18 stores a pulse count corresponding to the interval d for each screen. The contents of the register 18 in the other register 19 are read for each screen in response to the vertical synchronization signal. As a result, register 19
The contents of one horizontal scanning line one screen before are stored in . Subtractor 20 subtracts the contents of register 18 from the contents of register 19. As a result,
The subtracter 20 obtains the difference Δd between the interval d2 in the previous screen and the interval d1 in the current screen. The comparator 21 compares whether the absolute value |Δd| of the output of the subtracter 20 is smaller or larger than the constant ΔdS given by the constant setter 22. The imaging means 5 of the industrial television camera 3 are moved by a drive 23 . While moving the imaging means 5 from the front end to the rear end in the moving direction by the driving device 23, or vice versa, from the rear end to the front end,
Focusing can be achieved by measuring the distance d between the markers using video signals obtained from time to time and positioning the imaging means at the position where the distance d is maximum. The position where the interval d is maximum is the amount of change Δd in d
is near zero, and is a position where |Δd|<ΔdS holds true in the comparator 21. The comparator 21 detects |Δd|< during the operation of the drive device 23.
A point where ΔdS is established is determined, and the drive device 23 is stopped at this point. The synchronization signal separation circuit 24 separates a horizontal synchronization signal and a vertical synchronization signal from the video signal. The horizontal synchronizing signal is input to flip-flops 12 and 14 and a counter 17,
Gives an indication of the start and end timing of each horizontal scan line. The vertical synchronization signal is sent to registers 18, 19,
The signal is input to a subtracter 20 and a comparator 21, and provides an indication of the start and end timing of one screen.

In the embodiment described above, the detection area 2 is a black mark on a white background, but in another embodiment of the present invention, the mark may be realized by a so-called color code having chroma.

In the above embodiment, the distance between the marks imaged by the industrial television camera changes depending on the degree of defocus, so the focus is adjusted by maximizing this distance. In another embodiment of the invention, when black and white is the opposite of the above embodiment, the image of the mark (bar) as the detection area is widened due to defocus, and therefore a single bar image is used. The focal point may be determined by the position where the width is minimum. At this time, as described above, the interval between the previous screen and the interval between the current screen are adjusted so that the width in which the level corresponding to the indicator of the video signal shown in FIG. When the difference becomes a value close to zero, the movement of the imaging means 5 may be stopped.

As described above, according to the present invention, the focus of the imaging means of the optical detection device is automatically adjusted and an image of the detection area is formed on the photoelectric conversion means, so that the detection area can be clearly read. It becomes possible to identify the

In particular, in the present invention, the video signal for each horizontal scanning line from the photoelectric conversion means provided in the television camera 3 is binarized by the binarization circuit 8, and the interval d of the detection area 2 such as a bar code is Pulses from the pulse oscillator 9 corresponding to the width are counted by the counter 17, and the difference between the counted value and the stored contents of the register 19 that stores the counted value counted by the counter 17 one screen before. When the absolute value |Δd| of An excellent effect is achieved.

In particular, the ability to automatically adjust focus by processing an image binarized by the binarization circuit 8 and performing arithmetic processing on only one horizontal scanning line is a major advantage of the present invention. It is an effect.

Furthermore, by appropriately determining the constant ΔdS set in the constant setting device 22, it is possible to determine the precision of focus adjustment, and it is possible to set the optimum precision according to various uses. There is no problem that the accuracy is too high or too low, and it becomes possible to automatically perform optimal focus adjustment according to various uses.

Furthermore, according to the present invention, the detection area 2 formed on the surface of the article 1 includes a pair of band-shaped marks 6a and 6b arranged at an interval d along the direction of the horizontal scanning line of the television camera 3. By forming the detection region 2 having such a simple structure on the surface of the article 1, there is a clear contrast between the marks 6a and 6b and the background thereof. Adjustments can be made reliably. Such a detection area may be, for example, a bar code, and therefore the excellent effect that automatic focusing of the article 1 can be easily realized is achieved. The fact that the present invention can be easily implemented in this way is extremely important in the field of transporting goods 1, for example.

Further, according to the present invention, the first to third AND gates 10, 13, 16 and the first and second inverting circuits 1
1, 15 and the first and second flip-flops 1
2, 14, the distance d between the markers 6a, 6b
can be reliably detected, and its configuration is simple. This is also important for the present invention to be implemented in various fields.

Moreover, in the present invention, automatic focus adjustment can be performed by processing at least one horizontal scanning line of the television camera 3, and calculation processing is extremely simple, which is also important in the present invention. be.

Furthermore, in the present invention, the interval d is
By comparing the counted value of 7 with the stored content of the register 19, which is the counted value of one screen before, it can be relatively maximized or minimized. Therefore, it is not necessary to accurately determine the distance d, and even if it differs for each article 1, accurate focusing can be achieved.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a front view of the detection area 2, and FIG. 3 is a diagram showing an image of the detection area 2 taken by an industrial television camera. FIG. 4 shows the imaging means 5 of the industrial television camera 3.
FIG. 5 is a control block diagram for automatic focus adjustment, and FIG. 6 is a circuit diagram for calculating the distance between the markers in the detection area 2. It is a time chart. DESCRIPTION OF SYMBOLS 1... Article, 2... Detection area, 3... Industrial television camera, 5... Imaging means, 6... Sign, 8... Binarization circuit, 18, 19... Register, 20... Subtractor, 21
...Comparator, 23...Drive device, 25...Calculation circuit.

Claims (1)

[Claims] 1. A pair of belt-shaped signs 6a, 6b are arranged on the surface of the article 1 along a predetermined direction with an interval d, and there is a clear contrast between these signs 6a, 6b and the background thereof. An image of the detection area 2 of the object is formed on the photoelectric conversion means.
An image is formed by an image forming means 5 whose focal length is adjustable, and the predetermined direction is set in the direction of a horizontal scanning line; A drive device 23 that moves in one direction so that the distance to the photoelectric conversion means is changed and the focus is adjusted, and a binary drive device that binarizes the video signal of one horizontal scanning line from the photoelectric conversion means of the television camera 3. conversion circuit 8
, an oscillator 9 that generates pulses, and a oscillator 9 that derives pulses from the pulse oscillator 9 in response to the outputs of the binarization circuit 8 and the pulse oscillator 9.
1AND gate 10 and a first inverting circuit 1 that inverts the output of the binarization circuit 8
1, and is reset by a horizontal synchronizing signal from the television camera 3, and after being reset, the first inverting circuit 11 is reset in response to the output of the first inverting circuit 11.
The output of the first flip-flop 12 is set by receiving one of the predetermined rising or falling waveforms of the output, and then receiving the other waveform, and the output of the binarization circuit 8. and the first flip-flop 1
The output of the second AND gate 13 is reset by the horizontal synchronizing signal from the television camera 3, and after being reset, the second AND gate
In response to the output of the gate 13, one of the predetermined rising or falling waveforms of the output of the second AND gate 13 is received, and then either of the other waveforms is received, thereby setting the second AND gate 13. A second flip-flop 14, a second inversion circuit 15 for inverting the output of the second flip-flop 14, an output of the first AND gate 10, an output of the first flip-flop 12, and an output of the second inversion circuit 15 are provided, A third AND gate 16 that derives the pulse output from the pulse oscillator 9 via the first AND gate 10 during the interval d, a counter 17 that counts the pulses from the second AND gate 16, and a vertical synchronization signal from the television camera 3. in response to a register 19 that stores the counted value from the counter 17 of the previous screen; and in response to the outputs of the counter 17 and the register 19, the current counted value and the one horizontal scan of the previous screen. A subtracter 20 that subtracts the absolute value |Δd| of the difference from the counted value by the line, and a constant setter 22 that sets a predetermined constant ΔdS.
And the output of the absolute value |Δd| from the subtractor 20 is
a comparator 21 that stops the drive device 23 when the constant ΔdS set by the constant setter 22 is less than the constant ΔdS;
An automatic focus adjustment device comprising: