JPH0531992B2 - - Google Patents
Info
- Publication number
- JPH0531992B2 JPH0531992B2 JP62101072A JP10107287A JPH0531992B2 JP H0531992 B2 JPH0531992 B2 JP H0531992B2 JP 62101072 A JP62101072 A JP 62101072A JP 10107287 A JP10107287 A JP 10107287A JP H0531992 B2 JPH0531992 B2 JP H0531992B2
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- output
- time constant
- image sensor
- flip
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000007599 discharging Methods 0.000 claims description 8
- 230000003287 optical effect Effects 0.000 claims description 8
- 238000001514 detection method Methods 0.000 claims description 4
- 230000004069 differentiation Effects 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 5
- 239000003990 capacitor Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
Landscapes
- Character Input (AREA)
- Image Input (AREA)
- Facsimile Image Signal Circuits (AREA)
Description
【発明の詳細な説明】
〔産業上の利用分野〕
この発明は、OCR、バーコードリーダ、イメ
ージセンサ等の光学式画像入力装置における白レ
ベル検出回路に関するものである。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white level detection circuit in an optical image input device such as an OCR, a barcode reader, or an image sensor.
画像入力装置では照明光源の不均一性、cos4則
によるレンズ周縁部での効率劣化、あるいは紙質
の不均一、紙面上の汚れ等により基準になるべき
白レベルが不安定であることが多い。そこで忠実
に画像を再現するためには白レベルを正確にトレ
ースし画信号の基準とすることが必要になる。
In image input devices, the reference white level is often unstable due to non-uniformity of the illumination light source, efficiency degradation at the lens periphery due to the Cos 4 law, non-uniformity of paper quality, dirt on the paper surface, etc. Therefore, in order to faithfully reproduce an image, it is necessary to accurately trace the white level and use it as a reference for the image signal.
従来良く用いられる方式を第８図に示す。これ
は適当な放電を伴うピークホールド回路であつて
第９図ａのような画信号に対し、白レベルが上昇
中は急速充電によつて追従し、白レベルが下降中
はＣ、Ｒの時定数によつて放電することによつて
追従する。 A commonly used method is shown in FIG. This is a peak hold circuit with appropriate discharge, and when the white level is rising, it follows the image signal as shown in Figure 9a by rapid charging, and when the white level is falling, it follows the image signal at C and R. Follow up by discharging by a constant.
充電の時定数を短く放電の時定数を適度に長く
設定しておけば、画信号全体の周期の長い不均一
性には良く追従する一方、第９図ｂに示されるよ
うに幅の狭い黒に対しては追従しないため、白レ
ベル（背景）と画像をうまく弁別出来る。しかし
ながら、第９図ｃのようにかなり幅の広い黒が入
つた場合、その間に放電による出力低下が進み、
画信号は黒であるのに白レベルとの差がなくなつ
ていまうことになり、正確な画像の再現ができな
くなる。 If the charging time constant is set short and the discharging time constant is set appropriately long, it will be possible to track long-period non-uniformity of the entire image signal well, but it will also be able to track the non-uniformity of the image signal with a narrow width as shown in Figure 9b. Since it does not track the white level (background) and the image, it can effectively distinguish between the white level (background) and the image. However, when a fairly wide black area appears as shown in Figure 9c, the output decreases due to discharge during that time.
Even though the image signal is black, there is no difference between it and the white level, making it impossible to accurately reproduce the image.
またこれに対応するべく放電の時定数を極端に
長く設定すると、画信号全体の不均一性によるな
だらかな下降にも追従できなくなつてしまう。 Furthermore, if the discharge time constant is set extremely long to accommodate this, it becomes impossible to follow the gradual decline due to non-uniformity of the entire image signal.
特公昭61−20033号公報では、この対策として
２系統の光学系を用い、それぞれのイメージセン
サからの出力が互いに補い合う方式が提案されて
いる。 As a countermeasure to this problem, Japanese Patent Publication No. 61-20033 proposes a method in which two optical systems are used and the outputs from the respective image sensors complement each other.
しかしながら、２系統の光学系を使用する方式
は、特に小型軽量化を要求される手持ちの入力装
置はもちろん、据え起き式の装置においても不利
であり、また電気部品に比べて光学部品のコスト
がはるかに高いこと、光学系の調整が面倒である
こと等を考えるとあまり得策ではない。 However, the method of using two optical systems is disadvantageous not only for hand-held input devices that require compactness and weight reduction, but also for stationary devices, and the cost of optical components is higher than that of electrical components. Considering that it is much more expensive and the adjustment of the optical system is troublesome, it is not a good idea.
そこで、この発明は、第９図ｄに示すように、
幅の広い黒が入つても誤判断なく、安定した画像
の弁別ができる白レベル検出装置を提供すること
を目的とする。 Therefore, this invention, as shown in FIG. 9d,
To provide a white level detection device capable of stable image discrimination without erroneous judgment even when a wide black color is included.
この発明は上述の問題点を解決するために、第
１図に示すように、イメージセンサ出力のピーク
値を順次充電保持し適当な時定数で放電する充放
電回路１と、前記イメージセンサ出力の微係数を
求める微分回路２と、前記微分回路の出力と設定
値を比較する比較回路３と、前記比較回路の出力
によつてセツトあるいはリセツトされるフリツプ
フロツプ回路４と、前記フリツプフロツプ回路の
出力によつて駆動され前記充放電回路１の放電時
定数を切り替えるスイツチ回路５からなり、前記
イメージセンサ出力の微係数の絶対値が顕著に大
きくなつたときに充放電回路１の放電時定数を変
化させるようにしたものである。
In order to solve the above-mentioned problems, the present invention includes a charging/discharging circuit 1 that sequentially charges and holds the peak value of the image sensor output and discharges it with an appropriate time constant, as shown in FIG. A differentiating circuit 2 for calculating a differential coefficient, a comparing circuit 3 for comparing the output of the differentiating circuit with a set value, a flip-flop circuit 4 that is set or reset by the output of the comparing circuit, and a flip-flop circuit 4 that is set or reset by the output of the flip-flop circuit. The switch circuit 5 is configured to change the discharge time constant of the charge/discharge circuit 1 when the absolute value of the differential coefficient of the image sensor output becomes significantly large. This is what I did.
充放電回路１の放電時定数を決定するＣ、Ｒの
うちここではＲの値をスイツチ回路５によつて可
変にできるようにしている。
Of C and R that determine the discharge time constant of the charging/discharging circuit 1, the value of R here can be made variable by a switch circuit 5.
微分回路２は、画信号（第２図ａ）を微分し、
その変化の大きさ（微係数）に応じた信号を出力
する（第２図ｂ）。必要があれば線形または非線
形の増幅を行なう。 The differentiating circuit 2 differentiates the image signal (Fig. 2 a),
A signal corresponding to the magnitude of the change (differential coefficient) is output (Fig. 2b). Perform linear or nonlinear amplification if necessary.
比較回路３は、微分回路２の出力と、予め設定
された正および負のスライスレベルTH1とTH2
との比較を行ない、微分回路２の出力が正のスラ
イスレベルTH1より大きい値であればセツト信
号Ｓを、負のスライスレベルTH2より小さい値
であれば、リセツト信号Ｒを出力する。 Comparison circuit 3 receives the output of differentiation circuit 2 and preset positive and negative slice levels TH1 and TH2.
If the output of the differentiating circuit 2 is larger than the positive slice level TH1, a set signal S is output, and if the output is smaller than the negative slice level TH2, a reset signal R is output.
フリツプフロツプ回路４は、セツト信号Ｓが入
力されると出力を１にし、リセツトＲが入力され
ると出力を０にする。 The flip-flop circuit 4 sets the output to 1 when the set signal S is input, and sets the output to 0 when the reset signal R is input.
スイツチ回路５は、フリツプフロツプ回路４の
出力が１の間はスイツチを閉じて充放電回路１の
放電時定数を短くし、比較回路３の出力が０にな
るとスイツチを開いて充放電回路１の放電時定数
を広くする（第２図ｆ）。 The switch circuit 5 closes the switch while the output of the flip-flop circuit 4 is 1 to shorten the discharge time constant of the charge/discharge circuit 1, and opens the switch when the output of the comparator circuit 3 becomes 0 to discharge the charge/discharge circuit 1. Widen the time constant (Fig. 2 f).
白レベルから黒レベルに変わるときには、最初
の立ち上がりエツジで画信号の微係数が負の方に
大きくなるため、比較回路３、スイツチ回路５の
作用により、充放電回路１の放電時定数が長くな
る。そのため、前述の第９図ｃのごとき幅広の黒
レベルに対しても、白レベルが下がつて画信号に
近づくということはない。 When changing from the white level to the black level, the differential coefficient of the image signal increases in the negative direction at the first rising edge, so the discharge time constant of the charge/discharge circuit 1 becomes longer due to the action of the comparison circuit 3 and the switch circuit 5. . Therefore, even for a wide black level as shown in FIG. 9c described above, the white level does not drop and approach the image signal.
また、黒レベルから白レベルに戻るときには、
画信号の微係数が正の方に大きくなるのでスイツ
チ回路５が閉じ、放電時定数は短くなつて、白レ
ベルの変化に追従することが出来る。 Also, when returning from black level to white level,
Since the differential coefficient of the image signal becomes larger in the positive direction, the switch circuit 5 is closed, the discharge time constant becomes shorter, and it is possible to follow changes in the white level.
このため、第９図ｄのような、安定した画像の
弁別が可能となる。 Therefore, stable image discrimination as shown in FIG. 9d becomes possible.
第３図は実施例であり、充放電回路１は、バツ
フアとコンデンサC1、抵抗R1、R2でなるCR回路
とにより構成される。抵抗R2は、スイツチ回路
５のトランジスタにより入り切りされる。
FIG. 3 shows an embodiment, and the charging/discharging circuit 1 is constituted by a CR circuit including a buffer, a capacitor C 1 , and resistors R 1 and R 2 . The resistor R 2 is turned on and off by the transistor of the switch circuit 5.
微分回路２は、コンデンサC2と抵抗R3とから
成る。 Differentiator circuit 2 consists of capacitor C 2 and resistor R 3 .
比較回路３は、一対のオペアンプにより構成さ
れ、一方のオペアンプの負端子にスライスレベル
THI、正端子に微分回路２の出力信号が入力さ
れ、また他方のオペアンプの正端子にスライスレ
ベルTH2、負端子に微分回路２の出力信号が入
力される。 Comparison circuit 3 is composed of a pair of operational amplifiers, and a slice level is connected to the negative terminal of one operational amplifier.
The output signal of the differentiating circuit 2 is input to the positive terminal of the other operational amplifier THI, and the slice level TH2 is input to the positive terminal of the other operational amplifier, and the output signal of the differentiating circuit 2 is input to the negative terminal of the other operational amplifier.
フリツプフロツプ回路４は、一対のNORゲー
トにより構成され、各ゲートにセツト信号Ｓ、リ
セツト信号Ｒが入力される。 The flip-flop circuit 4 is composed of a pair of NOR gates, and a set signal S and a reset signal R are input to each gate.
スイツチ回路５は、エミツタ接地のトランジス
タにより構成され、そのコレクタに前記の抵抗
R2が接続される。 The switch circuit 5 is constituted by a transistor whose emitter is grounded, and whose collector is connected to the above-mentioned resistor.
R 2 is connected.
スイツチ回路５は第４図に示すようにダイオー
ド等を用いてもよい。ただし、この場合はトラン
ジスタによるスイツチングとは論理が逆になるた
め、フイリツプフロツプ回路４の反転出力に接続
しなければならない。 The switch circuit 5 may use a diode or the like as shown in FIG. However, in this case, the logic is opposite to that of switching using transistors, so it must be connected to the inverted output of the flip-flop circuit 4.
また、充放電回路１の放電時定数を変化させる
他の方法としては、第５図から第７図に示すごと
き回路もある。この場合、第６図及び第７図で
は、スイツチ信号が１のとき時定数が長くなるの
で、フリツプフロツプ回路４のＱ出力（反転出
力）をスイツチ信号として使用する。 Further, as another method of changing the discharge time constant of the charging/discharging circuit 1, there are also circuits as shown in FIGS. 5 to 7. In this case, in FIGS. 6 and 7, since the time constant becomes long when the switch signal is 1, the Q output (inverted output) of the flip-flop circuit 4 is used as the switch signal.
以上説明したように、この発明では黒の幅にか
かわらず白レベルを正確にトレースする白レベル
検出回路を提供するものであるから、この白レベ
ルを基準にすることによつて画像を忠実に再現す
ることが出来る。しかも解決の手段を光学系によ
らず単純な電気的処理のみとしたため、読取部を
小型かつ安価に構成することができ、また当然調
整も容易である。
As explained above, the present invention provides a white level detection circuit that accurately traces the white level regardless of the black width, so by using this white level as a reference, images can be faithfully reproduced. You can. Moreover, since the solution is not based on an optical system but only on a simple electrical process, the reading section can be constructed in a small size and at low cost, and of course it is easy to adjust.
第１図はこの発明の構成を示すブロツク図、第
２図のａ図からｆ図は各部の信号の波形図、第３
図は実施例の回路図、第４図から第７図は他の実
施例の一部を示す回路図、第８図は従来例の回路
図、第９図のａ図からｄ図は従来例の問題点の説
明のための画信号の波形図である。
１……充放電回路、２……微分回路、３……比
較回路、４……フリツプフロツプ回路、５……ス
イツチ回路。
Figure 1 is a block diagram showing the configuration of the present invention, Figures a to f in Figure 2 are waveform diagrams of signals at each part, and Figure 3
The figure is a circuit diagram of the embodiment, Figures 4 to 7 are circuit diagrams showing part of another embodiment, Figure 8 is a circuit diagram of a conventional example, and Figures a to d in Figure 9 are conventional examples. FIG. 3 is a waveform diagram of an image signal for explaining the problem of FIG. 1... Charge/discharge circuit, 2... Differential circuit, 3... Comparison circuit, 4... Flip-flop circuit, 5... Switch circuit.
Claims (1)
において、イメージセンサ出力のピーク値を順次
充電保持し適当な時定数で放電する充放電回路
と、前記イメージセンサ出力の微係数を求める微
分回路と、前記微分回路の出力と設定値を比較す
る比較回路と、前記比較回路の出力によつてセツ
トあるいはリセツトされるフリツプフロツプ回路
と、前記フリツプフロツプ回路の出力によつて駆
動され前記充放電回路の放電時定数を切り替える
スイツチ回路からなり、前記イメージセンサ出力
の微係数の絶対値が顕著に大きくなつたときに充
放電回路の放電時定数を変化させることを特徴と
する光学式画像入力装置の白レベル検出回路。1. In an optical image input device using an image sensor, a charging/discharging circuit sequentially charges and holds the peak value of the image sensor output and discharges it with an appropriate time constant, a differentiation circuit that calculates a differential coefficient of the image sensor output, and a differentiation circuit that calculates the differential coefficient of the image sensor output; a comparison circuit that compares the output of the circuit with a set value; a flip-flop circuit that is set or reset by the output of the comparison circuit; and a flip-flop circuit driven by the output of the flip-flop circuit to switch the discharge time constant of the charge/discharge circuit. 1. A white level detection circuit for an optical image input device, comprising a switch circuit, and changing a discharge time constant of a charging/discharging circuit when the absolute value of a differential coefficient of the image sensor output becomes significantly large.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62101072A JPS63266965A (en) | 1987-04-23 | 1987-04-23 | White level detection circuit for optical image input device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62101072A JPS63266965A (en) | 1987-04-23 | 1987-04-23 | White level detection circuit for optical image input device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS63266965A JPS63266965A (en) | 1988-11-04 |
| JPH0531992B2 true JPH0531992B2 (en) | 1993-05-13 |
Family
ID=14290899
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62101072A Granted JPS63266965A (en) | 1987-04-23 | 1987-04-23 | White level detection circuit for optical image input device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS63266965A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2938588B2 (en) * | 1991-01-14 | 1999-08-23 | 信越化学工業株式会社 | Pellicle for optical dust |
-
1987
- 1987-04-23 JP JP62101072A patent/JPS63266965A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS63266965A (en) | 1988-11-04 |
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