JPH02105778A - Image pickup device - Google Patents

Abstract

PURPOSE:To prevent occurrence of a failure caused by a reflecting section by detecting a reflecting section of the surface of an object and outputting a reflecting signal. CONSTITUTION:In a device which outputs image pickup signals outputted from a one-dimensional image sensor 16 after binarizing the signals after the signals are passed through an AGC circuit 18, reference potential of a fixed level corresponding to the background color of an object is produced by means of the 1st charging and discharging circuit 20 based on the image pickup signals and, at the same time, an output which follows a change in the image pickup signals, but does not rise beyond the reference potential is produced by means of the 2nd charging and discharging circuit 22. Then the output is compared with the image pickup signals and, when the level of the image pickup signals exceeds the output, a reflecting signal indicating that the image picked-up part is a reflecting section is outputted. Therefore, a failure caused by a reflecting section can be prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an imaging device used in a device for printing out characters and figures drawn on a wall surface such as a blackboard, whiteboard, or bulletin board. Regarding.

(Prior technology) Letters, figures, etc. drawn on various walls such as a blackboard are incident through a lens, the angle of view is determined while being monitored by a viewfinder, and the image is scanned by a one-dimensional image sensor. The present applicant has proposed a so-called imaging printing device that operates a printer based on an image signal generated by the image and prints out the characters, figures, etc. on paper.

In such an imaging device, an imaging signal output from a one-dimensional image sensor is binarized and used as a double-sided signal for the subsequent printer or the like.

Binarization of the carrier signal is performed as shown in FIG. In other words, a comparator IG is used, and the R image signal is input to its (to) input terminal ■, and the image signal is smoothed by a resistor R, a capacitor, and a variable A comparison signal voltage-divided by the resistor VR is input.

Here, as shown in FIG. 12, a white board 1 is used as a subject.
Let us consider a case where a character 12 is drawn on the surface of a computer 1, and this is to be imaged. Generally, the white board 11 has a smooth surface and a high reflectance, so a reflective part 13 of light from an indoor fluorescent lamp or the like is formed, and uneven brightness occurs on the surface of the white board 11 as a subject.

When capturing an image of the surface of the white board 11, a one-dimensional image sensor is arranged in the straight y direction in the figure, main scanning is performed in the y direction, and the one-dimensional image sensor is moved in the horizontal direction in the figure by a drive mechanism (not shown). The object is moved and sub-scanning is performed. Now, when one line including the reflection section 13 is main-scanned as shown by the straight line y in FIG. 12, the imaging signal input to the 0 input terminal O of the comparator IG in FIG. In 2), it changes as shown by the solid line. That is, the surface of the white board 11 other than the reflective portion 13 is maintained at a certain level and includes a high frequency portion corresponding to the characters 12. As described above, a comparison signal smoothed by a resistor R and a capacitor C and set to a low level by a variable resistor VR is input to the input terminal 0 of the comparator IC. It is indicated by a broken line in Figure (2). Since the high frequency portion corresponding to the character 12 is lower than the comparison signal level, the
A binary output corresponding to black is produced as shown in .

The m-image signal level has a peak corresponding to the reflection section 13 in FIG. 12. Furthermore, a comparison signal obtained by smoothing this imaging signal also peaks with a predetermined time delay. Therefore, due to the deviation of these peaks, the levels of both signals are inverted in the latter half of the reflection section 13, resulting in a binary signal corresponding to black, that is, a false signal. As a result, in the printout, as shown in FIG. 14 (2), in addition to the characters 12 written on the white board, a thick black portion 13a appears behind the reflective section 13 in the main scanning direction. .

(Problems to be Solved by the Invention) As described above, if there is a reflective part in the subject, false signals will be mixed into the binary output due to this, making it impossible to obtain accurate binary output.

An object of the present invention is to provide an imaging device configured to detect a reflective part on a subject and output a reflected signal, thereby preventing problems caused by the reflective part.

[Structure of the invention]

(Means for Solving Problem 1) The imaging device according to the present invention passes an imaging signal output from a one-dimensional image sensor through an AGC circuit, converts it into a binarized signal, and outputs the binarized signal. and a reflected signal detection circuit. The first charging/discharging circuit inputs the carrier signal that has passed through the AGC circuit, and is set to a time constant of a size that does not cause an output change during at least one main scanning period of the one-dimensional image sensor. has been done. The second charging/discharging circuit is set to a time constant smaller than the time constant of the first charging/discharging circuit, and obtains a smoothed signal that follows changes in the imaging signal occurring during the one main scanning period. This generates an output that is limited to a reference potential which is the output value of the first charging/discharging circuit.

Roughly speaking, the reflected signal detection circuit compares the output of the second charging/discharging circuit with the imaging signal, and produces an output when the imaging signal exceeds the output level of the second charging/discharging circuit.

Further, the invention of claim 2 provides that a part of the first charging/discharging circuit is A
A switch means is provided which also serves as a control signal input section of the GC circuit, is operated by the output of the reflected signal detection circuit, and attenuates the input signal of the first charging/discharging circuit.

Furthermore, the invention of claim 3 provides a first signal having a relatively small time constant and a second signal having a relatively large time constant and a signal level slightly lower than the first signal based on the imaging signal. and a falling detection circuit that generates an output by reversing the magnitude relationship between these two signals, and operates on the condition that the output of the falling detection circuit and the output of the reflected signal detection circuit are both generated, A switch means is provided for reducing the level of the comparison signal for binarization, which is set lower than the lff1 image signal and follows the change thereof.

(Function) In the present invention, the first charging/discharging circuit generates a reference potential at a partial level corresponding to the background color of the subject based on the image carrier signal, and the second charging/discharging circuit changes the imaging signal. Generates an output that follows but does not exceed the above reference potential, and compares this output with the imaging signal. If the imaging signal level exceeds the above output, it means that this image carrying part is a reflective part. outputs a reflected signal.

In addition, there is a peak in the imaging signal caused by the reflection part, and if this peak is repeatedly input to the first charging/discharging circuit, the level of the reference potential will rise and a problem will occur. Therefore, the switching means is operated by the reflected signal. This attenuates the peak in the human input signal and prevents the reference potential level from rising.

Furthermore, by detecting the falling edge of the l1iH[I signal and combining this falling detection signal with the above reflected signal, it is possible to determine whether this falling edge is the falling edge after the peak of the reflective part or not by imaging thick characters, etc. If it is a fall after the peak, the level of the comparison signal for binarization is reduced, and if it is a fall after the peak, the level of the comparison signal for binarization is reduced. This prevents the generation of false signals.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In Fig. 1, 16 is a one-dimensional image sensor (hereinafter C
(described as OD), the drive circuit 17 main scans the white board 11 shown in FIG. 12, for example, in the direct IIyh direction to generate a 1lil image signal corresponding to the brightness of the white board 11, which is the subject. Of course, sub-scanning is also performed in the horizontal direction in FIG. 12, and the entire surface of the white board 11 is conveyed.

Reference numeral 18 denotes an AGC circuit that controls the amplitude of the imaging signal, and includes an amplifier section 18a and a control section 18b. The amplifier section 18a has an input amplifier AMP from the CG D 16 via an ms multiplied signal input resistor R1. II @ part 18b is
The amplifier AMP has a transistor Q1 whose collector is connected to the input terminal of the amplifier AMP via a capacitor C1 and whose emitter is connected to ground. The base of this transistor Q1 is connected to the emitter of a transistor Q2 whose collector is connected to the power supply Vcc via a resistor R2. This transistor Q
The base of 2 includes a resistor R3 whose one end is connected to the output terminal of the amplifier AMP, a forward diode D1, and a capacitor C provided between the cathode of this diode D1 and the ground.
2 and a time constant circuit consisting of a resistor R4 connected in parallel thereto via a resistor R5.

20 is a first charging/discharging circuit, which includes a buffer IC1o;
Its 0) input terminal is connected to the time constant circuit. Further, the 0 input terminal is connected to the ground via a resistor R6, and is also connected to the output terminal via a resistor R7. That is, the time constant circuit portion of the first charging/discharging circuit 200 is connected to the AG
It also serves as a control signal input section for the control section 18b of the C circuit 18. Further, this first charge/discharge circuit 20 is set to a large time constant by the time constant circuit so that the output generated at the output terminal of the buffer C1o does not change during at least one main scanning period of the COD 16, AGC circuit 1
Based on the imaging signal that has passed through step 8, a base potential of a level corresponding to the color of the subject's back is generated.

SW1 is a switch means, one end of which is connected to the anode of the diode D1 via a resistor R8, and the other end connected to ground. Then, it turns on in response to a reflected signal, which will be described later, and attenuates the input signal level to the first charging/discharging circuit 20.

22 is a second charging/discharging circuit, which has a buffer IC1t and a comparator IC12, and has a buffer IC1t and a comparator IC12.
0) input terminal is connected to ground via a resistor R9, and is also connected via a resistor R1o to the other end of a capacitor C3 whose one end is connected to ground.

Further, the other end of this capacitor C3 is connected to the switch means SW.
2. It is connected to the output side circuit of the AGC circuit 18 via a resistor R11 and a diode D2 in the charging direction, and is also connected to the output circuit through a diode D3 and a resistor R12 in the discharging direction. Also, this buffer ■C11
The output terminal of is connected to the (to) input terminal and also to the 0 input terminal of the comparator 1C12. This comparator ICtzO) (g) input terminal is connected to the first charging/discharging circuit 20.
It is connected to the output terminal of , and its output, the reference potential, is input. Further, the output end thereof is connected to the power supply Vcc via a resistor R13, and the control 2! of the switch means SWz is controlled. Connect to the L end.

As mentioned above, the reference potential is applied to the ←) input terminal of the comparator IC12, and if the output potential of the buffer ■C11, that is, the potential at the point ■ is lower than the base potential M, the control @ end of the switch means SW2 is energized. and turn it on. When this switch means SW2 is in the on state,
The imaging signal that has passed through the AGC circuit 18 is charged to a capacitor C3 via a diode D2 and a resistor R11, and is also discharged via a diode D3 and a resistor R12. The time constant of this charging/discharging section is set to be smaller than the time constant of the first charging/discharging circuit 20, and a smoothed signal that follows changes in the imaging signal is input to the ←) input terminal of the buffer C11. Ru. As mentioned above, the output terminal of this buffer IC11 is connected to the 0 input terminal of the comparator IC12, so when the potential at point (2) becomes equal to or higher than the reference potential, the comparator ICv operates inverted, the switch element SW2 is turned off, and (2) A rise in point potential is prevented. That is, the output of the second charging/discharging circuit 22 (potential at point ■) follows changes in the imaging signal, but is cut off when it exceeds the reference potential, resulting in a value limited to below the reference potential.

23 is a reflected signal detection circuit, which is a comparator IC? 3, whose 0 input terminal is connected to the output terminal of the second charging/discharging circuit 22, and the potential at the point ■ is inputted thereto. Moreover, the 0) input terminal of the converter ICt+ is connected to a resistor R14 connected in series between the output side circuit of the AGC circuit 18 and the ground.
These resistors R14, Rs
The pressure is divided by I! A display signal is input.

Therefore, the] comparator 1C13 generates an output (reflection signal) when the imaging signal increases rapidly by imaging the reflective portion (13 in FIG. 12) in the object and exceeds the 0 point level.

The output terminal of this comparator ICl3 is connected to the power supply VCC via a resistor R16, and the switch means SW1
The switch means SW1 is turned on by the reflected signal.

In the above configuration, it is assumed that the surface of the white board 11 shown in FIG. 12 is imaged by the CG D 16.

Generally, when the white board 11 is used as a subject, the image signal of the white background has a flat amplitude characteristic. Although the characters 12 and the like drawn on the white board 11 are output as low-level (dark-color level) pulse-like signals, the proportion of the white board 11 to the whole is small and does not affect the flat amplitude characteristics. Therefore, in the following description, the image signals of the characters 12 and the like will be ignored, and only the image signals of white will be explained.

Such a white image pickup signal is sent to the AGC circuit 18.
Tall lower r constant value Sasuruka, A G CTo
Since the time constant of the control signal input section in the ll till section 18b is large, it does not respond to the brightness of each main scanning line.

In other words, as shown by the solid line in FIG. 3, the image signal of one line after a stable state becomes larger when the subject, the white board 11, is brighter, and becomes smaller when it is darker. The output voltage (reference potential) of the discharge circuit 20 also changes similarly, as shown by the broken line in the figure.

Then, as shown in FIG. 12, when the imaging state is such that the reflection section 13 is included during the main scanning of one line y, an imaging signal with peak characteristics is naturally obtained as shown in FIG. 4. However, the reference potential is still held at its previous value due to the large time constant mentioned above. That is, A.G.C.
Due to the response delay of the system, the voltage with no reflection remains as the reference potential.

On the other hand, in the second charge/discharge circuit 22, the switch means SW2
is on, the imaging signal is transferred to capacitor C3 and resistor R.
11, R12 and the diodes D2 and D3, and when the value exceeds the reference potential, the switch means SW2 is turned off to regulate the upper limit. As shown in , an output whose upper limit value is regulated by the reference potential is generated.

The output of the second charge/discharge circuit 22, that is, the point ■ potential, is compared with the voltage-divided WAM image signal, that is, the O point potential, in the reflected signal detection circuit 23, and as shown in FIG.
When the O point potential exceeds the point ■ potential due to the peak corresponding to the reflection 1s13, the comparator ■C13 performs an inverting operation and produces an output with a pulse width corresponding to the peak width at the output terminal [F], that is, a reflected signal.

Here, the reason why the point ■ potential based on the imaging signal is used as the comparison signal for the O point potential in the reflected signal detection circuit 23 without using a constant level threshold is as follows. In other words, as shown in Figure 9, if the white board's stiffness differs between the upper and lower parts, it may not be possible to create a reflected signal when comparing using a constant single value, but if point potential is used, such a This is because the reflected signal can be reliably reflected.

Furthermore, when an imaging signal including a peak value corresponding to the reflection 8B13 is repeatedly input, the reference potential which is the output of the first charging/discharging circuit 20 increases as shown in FIG. Detection and binarization described later become inaccurate. Therefore, once the reflection section 13 is detected, the reflection signal turns on the switch means SW1 shown in FIG. Attenuate. In this way, it is possible to prevent the reference potential from rising, and as shown in FIG.
Even if the 1m signal includes a peak, the reference potential can be maintained at the value when there is no peak.

Next, referring to FIG. 2, a means for removing false signals during binarization will be explained.

In FIG. 2, 25 is a falling/falling detection circuit, which has a comparator ICn, and its 0 input terminal (0 point) is connected to a capacitor C4 provided between a resistor R17 and the ground.
A carrier signal is inputted through a time constant circuit consisting of a resistor Rw and a resistor Rw. Similarly, the 0 input terminal (0 point) has a resistor RFI.
The m-image signal is inputted through a time constant circuit consisting of a capacitor C5 and a resistor R20, which are provided between the ground and the ground.

Here, the values of each of the above time constant circuits are changed so that the time constant of the first signal applied to the 0 input terminal is relatively small, and the time constant of the second signal applied to the (G) side input terminal is is relatively large and the signal level is set to be slightly lower than the first signal.

At the output J end (point 0) of the comparator IC14, an output, that is, a falling detection signal is generated by reversing the magnitude relationship between the first signal and the second signal.

26 is a binarization circuit, the basic circuit configuration of which is the same as that shown in FIG. 11, and includes a comparator ICl3. The il image signal is input to the 0) input terminal of this comparator ICs, and the ms multiplied signal is smoothed by the resistor Rzl and the capacitor C6, and the variable resistor v
A comparison signal voltage-divided by R1 is input. In addition, its output end is connected to the power supply Vcc via a resistor R22,
Generates a binary output corresponding to changes in the imaging signal.

Here, the upper end of the capacitor CB and the 0 point at which the second charge/discharge circuit 22 exits are connected via a resistor R23 and a switch means SW3. The above-mentioned switch means SW3, by its ON operation,
This is to reduce the potential of the comparison signal applied to the 0 input terminal of s to near the torpedo level.

The output terminal of the fall detection circuit 25 is connected to the power supply Vcc via a resistor R24, and also connected to the output terminal of the reflected signal detection circuit 23 via a diode D4, and further connected to the control terminal of the switch means SW3. are doing.

In the above configuration, the fall detection circuit 25 responds to and detects the fall of the low frequency component of the imaging signal. In other words, as shown in Fig. 7, it responds to and detects the falling edge after the peak corresponding to the reflective part, or the falling edge when thick characters or filled figures are imaged. It does not respond to high frequency components corresponding to thin lines, letters, etc.

Here, if you image the reflective part 13 on the white board 11 within one line and then image the thick black line, etc., the potential at the 0 point in FIG. 2 will change to the line state after the peak, as shown by the solid line in FIG. becomes. On the other hand, the potential at the 0 point in Figure 2 is slightly lower than the 0 point, as shown by the broken line in Figure 7, due to the above-mentioned time constant relationship, and it follows the change in the torpedo position. Change. Therefore, in the falling portion, the magnitude relationship between the two is reversed, and the output terminal (0 point) of the comparator IC14
Falling detection signals P and P2 are generated. However, the falling detection signal P2 corresponding to the thick line etc. is generated on the condition that the diode D4 connected to the output end (point [F]) of the reflected signal detection circuit 23 is an oven. However, since the diode D4 is actually connected and no reflected signal is detected at this timing, point [F] is at the "L" level, and the detection signal P2 is applied to the control terminal of the switching means SWa. The switching means SWa remains in the OFF state.

On the other hand, at the timing when the falling detection signal P1 after the peak corresponding to the reflection section 13 is generated, the reflected signal is detected as shown in FIG. ] point) is at "H" level. Therefore, the falling detection signal P1 does not drop to a single point level via the diode D4, and the falling detection signal P1
The potential of the comparison signal applied to the O input terminal (point 0) of the comparator ICl3 is changed to the potential of the output terminal (point 0) of the second charging/discharging circuit 22 by turning on the switching means SWa. (lower than M quasi-potential) by discharging and reducing it.

Here, 0) of the comparator ICl3 of the binarization circuit 26
The above-mentioned signal is input to the input terminal, and the input terminal (0 point) has a potential lower than this carrier signal, as shown by the broken line in FIG. 10 (2). In addition, since a comparison signal that follows changes in the m-image signal is added, the reflection section 13
At the time of falling after the peak corresponding to
), the magnitude relationship between these is reversed, and a false signal is generated as shown in (c) of the same figure. However, as mentioned above, the falling signal P1 after the peak turns on the switch means SW3, and as shown in FIG. , the reversal of the carrier signal and the comparison signal (0 torpedo level) is extremely instantaneous, and a large false signal does not occur as in the conventional case shown in FIG. 13(2). Therefore, even in the results of printing based on this binary signal, a thick black portion 13a does not occur behind the reflective section 13 in the scanning direction as in the conventional example shown in FIG. ).

On the other hand, when imaging a thick line or a filled part drawn on the white board 11, the imaging signal falls at a low frequency, but the falling detection signal P2 explained in FIG. Since it is wired, it is not applied to the switch means SW3, and the switch means SW3 remains off. Therefore, the comparison signal (0 torpedo level) does not decrease as shown in Figure 10 (2), and therefore, as shown in Figure 10 (B), a binary output that means black corresponding to the falling edge of the imaging signal occurs.

That is, by combining the falling detection signal and the reflected signal, it is determined whether the falling signal is caused by imaging the reflecting section 13 or the falling signal is caused by imaging a bold character, etc. I! If the image is imaged, turn on the switch means SWa,
The level of the comparison signal is reduced to prevent the output of large false signals.

In addition, in FIG. 1, the AGC circuit 18 is shown in order to simplify the explanation.
Although the control unit 18b and the first charging/discharging circuit 20 have been described as being common, they may be provided separately.

〔Effect of the invention〕

As described above, according to the present invention, if there is a reflective part on the surface of the subject, it is reliably detected and a reflected signal is generated.
It is possible to prevent problems caused by this reflective part, such as the occurrence of large false signals due to the reference potential becoming monotonous or falling after the peak corresponding to the reflective part.

Furthermore, if a memory element is used, false signals in binarized data can be completely removed.

[Brief explanation of drawings]

Figures 1 and 2 are circuit diagrams showing an embodiment of the image carrier Pi@ according to the present invention, Figure 3 is a characteristic diagram showing the relationship with the ms multiplied signal reference potential, and Figures 4 and 5 are reflection Figure 6 shows the relationship between the reflected signal detected by the device in Figure 1 and the control signal input of the AGC circuit attenuated by it. FIG. 7 is a characteristic diagram explaining the operation of the falling detection circuit shown in FIG. 2, and FIGS. 8 and 9 are characteristic diagrams explaining the operation of the reflected signal detection circuit shown in FIG. 1. , FIG. 10 is a characteristic diagram explaining the operation of the binarization circuit shown in FIG. An explanatory diagram showing the relationship with main scanning by the dimensional image sensor, FIG. 13 is a characteristic diagram explaining the problems of the conventional method, and FIG. 14 is a diagram comparing the printing results by the conventional device with the printing results by the device of the present invention. . 11... Subject (white board), 12... Characters, 13... Reflective part, 16... One-dimensional image sensor, 18... AGC circuit, 20... First charging/discharging circuit, 22... Second charging/discharging circuit. Discharge circuit, 23... Reflected signal detection circuit, 25... Fall detection circuit, SWl, 3W3... Switch means. ]1% stem

Claims (3)

[Claims] (1) In an imaging device that outputs an imaging signal output from a one-dimensional image sensor through an AGC circuit and then binarized, the imaging signal that has passed through the AGC circuit is input, and the one
A first time constant set to a magnitude that does not cause an output change during at least one main scanning period of the dimensional image sensor.
a charging/discharging circuit, the time constant of which is set to be smaller than the time constant of the first charging/discharging circuit, and a smoothed signal that follows changes in the imaging signal occurring during the one main scanning period is obtained; A second circuit that produces an output limited to a reference potential that is the output value of the charge/discharge circuit of
and a reflected signal detection circuit that compares the output of the second charging/discharging circuit with the imaging signal and generates an output when the imaging signal exceeds the output level of the second charging/discharging circuit. An imaging device characterized by: (2) A part of the first charging/discharging circuit also serves as the control signal input section of the AGC circuit, and is operated by the output of the reflected signal detection circuit to attenuate the input signal of the first charging/discharging circuit. The imaging device according to claim 1, further comprising a switch means. (3) A first signal with a relatively small time constant and a second signal with a relatively large time constant and a signal level slightly lower than the first signal are generated based on the imaging signal, and both of these signals are generated. It operates on the condition that the falling detection circuit generates an output by reversing the magnitude relationship of The imaging device according to claim 1, further comprising: a switch means for reducing a comparison signal level for binarization that follows a change.