JP3882745B2 - Optical information reader - Google Patents

Description

ただし、Ｗ：標識の幅データ、ta、tb：デジタル信号が変化した時刻、
Ａ、Ｂは定数、taveは（ta＋tb）／２である。
これによれば、請求項１と同様の効果を得ることができる。
【００２２】
【発明の実施の形態】
以下、本発明を手持ち式のバーコードリーダに適用した一実施例につき図面を参照して説明する。本実施例に係る光学的情報読取装置たるバーコードリーダは、図３に示すように、操作者（ユーザー）が片手でもって操作可能な大きさの縦長形状をなす装置ケースたるケース１内の先端側に、後述するように、読取対象２（図１参照）に記録されたバーコード（標識）３を読取るための、光学機構４を備えて構成されている。
【００２３】
この光学機構４は、図１に示すように、光源たるレーザー光源５と、このレーザー光源５からのレーザー光を偏向して前記読取対称２を走査する走査手段たる走査ミラー６と、入射光量に応じた電気信号を発生する光電変換手段としての光電変換素子７と、前記読取対象２から反射したレーザー光（反射光）を光電変換素子７に集光させるレンズ８とを備えて構成されている。
【００２４】
前記走査ミラー６は駆動力供給手段たる駆動力供給装置９によって、中心軸を中心としてある角度範囲で往復運動この場合振動運動により往復運動（揺動）するようになっている。上記駆動力供給装置９は、図２に示すように構成されている。走査ミラー６を回転軸１０により回転可能に支持し、この回転軸１０にはばね部材１１の中央部が連結されている。そして、このばね部材１１の両端部は動き可能にアーム部材１２に支持されている。さらに回転軸１０には駆動力付与部材１３が連結されている。この駆動力付与部材１３の先端部には磁石１４が取り付けられており、この磁石１４は電磁コイル１５に駆動パルスが与えられることより吸引・解放されるようになっている。この場合、電磁コイル１５の駆動力付与つまり電磁コイル１５の駆動パルスはこの振動系の共振周波数と同期した周波数で与えられるものである。
【００２５】
前記光電変換素子７は読取対象２のバーコード３の反射率に対応した電気信号（アナログ信号）を出力するものであり、その出力信号は増幅手段１６により増幅され、そしてこの電気信号を量子化例えば二値化する二値化手段１７により二値化される。
【００２６】
この二値化信号（デジタル信号）は制御装置１８に与えられる。この制御装置１８は、基準クロック発生手段、ＣＰＵ、ＲＯＭ、ＲＡＭなどを備えて構成されており、推定手段及び復号手段として機能するものである。また、この制御装置１８は前記駆動力供給装置９に前記共振周波数と同期する駆動パルスを出力するものである。
【００２７】
また、前記レーザー光源５はレーザー駆動手段１９により駆動されてレーザー光を出力するものであり、このレーザー駆動手段１９は制御装置１８により制御される。
【００２８】
なお、前記ケース１の先端には、読取窓１a（図３参照）が形成されていて、この読取窓１ａの中心線はケース１の中心線と合致する。そして、前記走査ミラー６の振動中心軸Ｐはこのケース１の中心線と合致し、走査の有効範囲がこの振動中心軸Ｐに対して略対称である。
【００２９】
また、図４に示すように、上記振動中心軸Ｐに対して対象位置（つまり走査基準点Ｏから左右同じ角度θ_Ｗの位置）には、検出手段たる第１の光センサ２０及び第２の光センサ２１が配置されている。各光センサ２０、２１は図５に示すように、レーザー光を受けて検出信号S1、S2を出力するものであり、この場合、例えば第１の光センサ２０はレーザー光の走査に伴って検出信号S1を図５に示すように出力するものであり、これに基づいて走査光の１周期Ｔが分かるものである。従って角速度ωが検知される。
【００３０】
角速度ω＝２π／Ｔ
また、各検出信号S1、S2から有効走査範囲Ｓが分かるものである。
【００３１】
さて、上記構成において、ユーザーがケース１の読取窓１ａを、バーコードが記録された読取対象に対してほぼ平行となるように近接（例えば距離Ｄ）させた状態で、読取走査（トリガスイッチのオン操作）を行なうことにより、制御装置１８がレーザー駆動装置１９を制御して、レーザー光源５からレーザー光を出力させる。さらに、制御装置１８は駆動力供給装置９を制御して操作ミラー６を振動させて、レーザー光を偏向して読取対象に当てる（走査する）。
【００３２】
レーザー光は、読取対象でバーコードの白黒の反射率に応じた光強度で反射して、レンズ８を介して光電変換素子７に入射する。そして、この光電変換素子７は反射率に対応した入射光量に応じて電気信号（アナログ信号）を出力する。この出力は、増幅手段１６を介して二値化手段１７に与えられ、この二値化手段１７は、バーコードの白黒に応じて（前記反射率に応じて）二値化信号を出力する。このとき、バーコードの白黒を同じ幅としたとき、走査速度が単振動的に変化するから、走査中心から遠ざかるに従って走査速度が遅く、基準クロックでデジタル化すると、走査中心から遠ざかるに従って二値化信号（例えば黒をハイレベル、白をロウレベルとする）のハイレベル領域及びロウレベル領域は広くなる。
【００３３】
しかし、制御装置１８は、上記基準クロックに基づいて走査光の反射率が変化する位置を検出している。すなわち、前記有効走査範囲Ｓの基準クロック数Ｎは計測できるものであり、走査往方向（図４の矢印Ｒ方向）の検出信号S1から、Ｎ／２の基準クロック数をカウントした時刻が時刻「ｔ０」であり、この中心位置「ｔ０」から矢印Ｒ方向へ基準クロックの１パルス時間分移った時刻が時刻「ｔ１」、以下、矢印Ｒ方向へ順次、時刻「ｔ２」、「ｔ３」、・・・となる。逆に、上記時刻「ｔ０」から、復方向（矢印Ｌ方向）へ順次時刻「−ｔ１」、「−ｔ２」、・・・となる。
【００３４】
そして、制御装置１８は、次のようにしてバーの幅である黒の幅及び白の幅データを生成する。図４に示すように走査基準点Ｏから読取対象２までの距離をＤとすると、中心軸からの走査光の位置Ｘを次の式（６）のように推定する。
【００３５】
Ｘ＝Ｄ・tan（θ_Ａ・sin（ω・ｔ））・・・（６）
ここで、ｔは前記時刻「ｔ１」、「ｔ２」、・・・及び「−ｔ１」、「−ｔ２」、・・・のいずれかである。これにて、中心軸Ｐからの時刻（基準クロックによる時刻）における走査光の位置Ｘを推定できるのである。
【００３６】
従って、反射率が変化した時刻つまり二値化信号が変化した時刻ｔaの位置Ｘから次の二値化信号が変化した時刻ｔｂの位置Ｘの差をとれば幅データＷを生成することが可能である。
従って、幅データＷは下記（３）式のようになる。
【数５】

なお、この場合全走査角の１／２の角度θ_Ａは予め定められた既知の値としており、角速度ωは測定されて判明している値であり、反射率が切り替わった時刻つまり二値化信号が変化した時刻ta、tbは検出されて判明している値であり、よって、Ｗが求められる。
【００３７】
なお、上記式（３）を用いて、基準クロックの１周期における幅データの変化（中心軸から遠ざかるにつれての変化）の様子を表１に示している。
【表１】

【００３８】
この場合、走査１周期で基準クロック数を４０００とし、全走査角の１／２の角度θ_Ａを３０°としている。この表１から分かることは、中心軸極近くの幅データ（時刻ｔ０、時刻ｔ１間の幅データ）を基準幅データ「１」としたとき、中心軸から遠ざかるにつれて幅データが小さくなる。つまり、実際の走査位置にあった幅データとなる。
【００３９】
前記式（３）（式（１）と同じ）には、次の考え方が含まれている。すなわち、基準クロック周期に相当する幅データ（中心軸での時刻ｔ０からｔ１への時間（例えば１ms）での幅データ）を基準幅データ「１」（これは実際の長さ例えば０．１mmとしてもよい）とし、二値化信号が変化した走査位置（推定値）の差分と、この基準幅データとに基づいて、バーコードの白黒の幅データが求められている。
【００４０】
この結果、基準クロックを用いて二値化しながらも、簡単な構成によりバーコードの正確な幅データを得ることができる。
【００４１】
また、走査ミラー６を、装置の中心線近傍を振動中心軸Ｐとして振動し、走査の有効範囲Ｓがこの振動中心軸Ｐに対して略対称であるようにしているから、幅データＷを誤差無く生成できる。
【００４２】
なお、上記全走査角の１／２の角度θ_Ａは、前記二つの光センサ２０、２１により推定しても良い。すなわち、
θ_Ｗ＝θ_Ａ・sin（ω・Ｓ／２）＝θ_Ａ・sin（π・Ｓ／Ｔ）
よって、θ_Ａ＝θ_Ｗ／sin（π・Ｓ／Ｔ）
となる。従って、測定されたＳ、Ｔと、既知のθ_Ｗとから全走査角の１／２の角度θ_Ａを推定できる。
【００４３】
またこのようにして、走査ミラー６の振動運動（往復運動）の１周期ごとに、全走査角の１／２の角度θ_Ａを求めると共に、光センサ２０、２１のいずれかにより角速度ωを求めた後に前記幅データＷを求めるようにしても良い。これによれば、走査開始初期の過渡期などにおいても、正確な角速度ω及び全走査角の１／２の角度θ_Ａを得ることができて、幅データＷを正確に得ることができる。
【００４４】
このほか、全走査角の１／２の角度θ_Ａが既知の場合には、前記二つの光センサ２０、２１のいずれか一方を設けて、角速度ωを、走査ミラー６の振動運動（往復運動）の１周期ごとに、求めた後に前記幅データＷを求めるようにしても良い。これによれば、走査開始初期の過渡期などにおいても、正確な角速度ωを得ることができて、幅データＷを正確に得ることができる。
【００４５】
また、前記角速度ω及び前記全走査角の１／２の角度θ_Ａは測定値ではなく、画一的な定数として例えばＲＯＭや不揮発性メモリなどの記憶手段に記憶させるようにしても良い。これによれば、角速度ω及び全走査角の１／２の角度θ_Ａの測定の面倒はない。さらにこの記憶手段に、前記角速度ω及び前記全走査角の１／２の角度θ_Ａを補正するための補正値を記憶させるようにしても良い。これによれば、装置個々に角速度ωや全走査角の１／２の角度θ_Ａについて誤差を調べておけば、これを補正値として記憶手段により記憶させておくことにより、定数としての角速度ωや全走査角の１／２の角度θ_Ａを補正できる。
【００４６】
また、前記駆動力供給装置９を、検出手段を兼ねるようにしても良い。この場合、駆動力供給装置９の、走査ミラー６に対する往復運動の駆動力たとえば駆動パルスは、ある周波数でしかもほぼ一定の走査位置で与えられるので、その駆動パルスのタイミングで走査の位置を検出することが可能となる。
【００４７】
さらに、走査ミラー６の走査が安定状態であるときにのみ走査の位置の推定を行なうように（推定手段を有効にするように）しても良く、これによれば、走査不安定状態での幅データ取得をなくして幅データＷを精度良く生成できる。
また、前記推定手段を有効にするかどうかを操作者が設定することができる設定手段を設けても良い。
また幅データＷを求める式として前記（１）式に近似する近似式でもよく、この場合、その近似式は下記（２）式としても良い。
【００４８】
【数６】

ただし、Ｗ：標識の幅データ、ta、tb：二値化信号が変化した時刻、
Ａ、Ｂは定数、taveは（ta＋tb）／２である。
【００４９】
例えば定数Ａは、３．２×１０^−１３、定数Ｂは、７．０８×１０^−７である。前記ta、tbを適宜選択しての計算結果を表２に示す。この表２と前記表１との比較から分かるように、正確な幅データを得ることができる。
【表２】

【００５０】
なお、本発明の光学的情報読取装置は、手持ち式のバーコードリーダに限られず、固定式のバーコードリーダに適用しても良い。また、走査手段に駆動力を供給する駆動力供給手段としてはパルスモータを用いたものでも良い。
【図面の簡単な説明】
【図１】光学機構及び電気的ブロック構成を示す図
【図２】駆動力供給装置の平面図
【図３】光学機構部分を示す平面図
【図４】走査光の範囲を示す図
【図５】（ａ）は第１の光センサの出力を示し、（ｂ）は有効走査範囲を示す図
【図６】アナログ信号波形と基準クロックと二値化信号波形との関係を示す図
【図７】従来における二値化信号出力の様子を示す図
【符号の説明】
１はケース、２は読取対象、３はバーコード（標識）、４は光学機構、５はレーザー光源、６は走査ミラー（走査手段）、７は光電変換素子（光電変換手段）、９は駆動力供給装置（駆動力供給手段）、１１はばね部材、１４は磁石、１５は電磁コイル、１７は二値化手段、１８は制御装置（推定手段、復号手段）を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical information reading apparatus that scans light to a sign that uses the reflectance of light such as a barcode and decodes the sign.
[0002]
[Prior art]
Conventionally, in an optical information reading apparatus such as a laser scanner, light from a light source is deflected by a scanning mirror serving as a scanning unit and applied to a barcode, and the intensity of reflected light corresponding to the white / black reflectance of the barcode is increased. The light is converted into an electric signal by the light receiving sensor. The converted electric signal (analog signal) changes corresponding to white / black of the barcode. The analog signal is A / D converted to generate a digital signal, and the digital signal is processed to obtain and decode barcode width data.
[0003]
In the above configuration, when an analog signal is A / D converted, the analog signal is sampled with a sampling clock at equal intervals. That is, for example, if an analog signal corresponding to reflected light having a black reflectance continues in an equally spaced sampling clock, the number of sampling clocks in the continuous period, or width data of one sampling clock period is added to the number of counts. The multiplication is recognized as one black width data.
[0004]
However, when there is no change in the scanning speed within one scan or when the change is small, there is no problem. However, when the scanning speed changes greatly within one scan, the bar code is changed depending on the change in the speed. The width data will change. For example, as shown in FIG. 7, even when the white / black widths of the barcode are the same, when the scanning speed changes in a simple vibration, the speed of the scanning peripheral part becomes slower than the scanning center P part, As a result, the sampling clock count number in the scanning peripheral portion is large, and the width data obtained from the digital signal becomes larger than the actual one.
[0005]
[Problems to be solved by the invention]
In order to cope with this, as disclosed in JP-A-5-242285, there is a configuration in which the generation timing of the sampling clock is controlled to n times the scanning speed. In this case, as clock generation means, In addition to the reference clock generating means, a PLL circuit, a phase comparator, an integrator, a voltage controlled oscillation circuit, a frequency divider, and the like are required, and there is a problem that the configuration becomes complicated.
[0006]
The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical information reading apparatus capable of accurately recognizing barcode width data with a relatively simple configuration.
[0007]
[Means for Solving the Problems]
[0008]
According to the optical information reading apparatus of the first aspect, since the estimating means estimates the light scanning position, the scanning position of the high reflectance portion and the low reflectance portion of the barcode are scanned by the digital signal at the scanning position. The position can be determined. Then, the decoding means generates the width data of the sign based on the scanning position and the digital signal, so that it is possible to obtain the width data close to the actual measurement value.
Further, based on the signal from the detection means, the angular velocity ω of the reciprocating motion used in the equation (1) is calculated for each cycle of the scanning means, and the estimation means and the decoding means Since the width data of the marker is obtained by the equation (1), an accurate angular velocity ω can be obtained even in a transition period at the beginning of scanning, and the width data can be obtained accurately.
[0014]
The detection means detects two points of the scanning position. Based on a signal from the detection means, the angular velocity ω and an angle θ _A that is ½ of the total scanning angle are detected by the scanning means. The calculation may be performed for each cycle of the reciprocating motion (the invention of claim 2), and in this way, the latest accurate angular velocity ω and the angle θ _A that is ½ of the total scanning angle can be obtained. Thus, the width data can be obtained accurately.
[0015]
Further, the storage means may be configured to store the angular velocity ω and the angle θ _A which is a half of the total scanning angle as constants in the storage means (invention of claim 3 ). According to this, there is no trouble of measuring the angular velocity ω and the angle θ _{A which} is ½ of the entire scanning angle. Further, the storage means may store correction values for correcting the angular velocity ω and the angle θ _A that is ½ of the total scanning angle (invention of claim 4 ). According to this, if an error is examined for each device, the angular velocity ω or the angle θ _A which is ½ of the total scanning angle, by storing the error as a correction value by the storage means, the angular velocity ω as a constant is obtained. And an angle θ _A that is ½ of the total scanning angle can be corrected.
[0016]
Further, the detection means may comprise an optical sensor (invention of claim 12). Further, a driving force supply means to the scanning means may be provided, and this driving force supply means may also serve as the detection means (the invention of claim 13). When the scanning means is reciprocated, the driving force of the reciprocating motion, such as a driving pulse, is applied at a certain frequency and at a substantially constant scanning position, so that the scanning position can be detected at the timing of the driving pulse.
[0017]
Further, the scanning means may be vibrated with the vicinity of the center line of the apparatus as a vibration center axis, and the effective scanning range may be substantially symmetric with respect to the vibration center axis. In this way, the width data can be generated without error.
[0018]
Further, the estimation means may be made effective only when the scanning of the scanning means is in a stable state (invention of claim 15), and according to this, width data acquisition in an unstable scanning state is eliminated. Width data can be generated with high accuracy.
[0019]
Further, a setting unit that allows an operator to set whether or not to enable the estimation unit may be provided (invention of claim 16).
[0020]
In order to achieve the above object, according to a seventeenth aspect of the present invention, the decoding means obtains the width data of the marker by the following equation (2) that approximates the equation (1).
[0021]
[Expression 4]

However, W: Mark width data, ta, tb: Time when digital signal changed,
A and B are constants, and tave is (ta + tb) / 2.
According to this, an effect similar to that of the first aspect can be obtained.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a hand-held bar code reader will be described with reference to the drawings. As shown in FIG. 3, the bar code reader as an optical information reading apparatus according to the present embodiment is a front end in a case 1 as a device case having a vertically long shape that can be operated with one hand by an operator (user). As will be described later, an optical mechanism 4 for reading a barcode (marker) 3 recorded on a reading object 2 (see FIG. 1) is provided on the side.
[0023]
As shown in FIG. 1, the optical mechanism 4 includes a laser light source 5 that is a light source, a scanning mirror 6 that is a scanning unit that deflects the laser light from the laser light source 5 and scans the reading symmetry 2, and an incident light amount. A photoelectric conversion element 7 serving as a photoelectric conversion unit that generates a corresponding electrical signal, and a lens 8 that focuses the laser light (reflected light) reflected from the reading object 2 onto the photoelectric conversion element 7 are configured. .
[0024]
The scanning mirror 6 is reciprocated (oscillated) by a reciprocating motion, in this case, an oscillating motion, within a certain angle range around the central axis by a driving force supplying device 9 as a driving force supplying means. The driving force supply device 9 is configured as shown in FIG. The scanning mirror 6 is rotatably supported by a rotating shaft 10, and a central portion of a spring member 11 is connected to the rotating shaft 10. Both end portions of the spring member 11 are supported by the arm member 12 so as to be movable. Further, a driving force applying member 13 is connected to the rotating shaft 10. A magnet 14 is attached to the tip of the driving force applying member 13, and the magnet 14 is attracted / released when a driving pulse is applied to the electromagnetic coil 15. In this case, the driving force application of the electromagnetic coil 15, that is, the driving pulse of the electromagnetic coil 15, is given at a frequency synchronized with the resonance frequency of the vibration system.
[0025]
The photoelectric conversion element 7 outputs an electric signal (analog signal) corresponding to the reflectivity of the barcode 3 of the reading object 2, and the output signal is amplified by the amplifying means 16, and the electric signal is quantized. For example, binarization is performed by binarization means 17 for binarization.
[0026]
This binarized signal (digital signal) is given to the control device 18. The control device 18 includes a reference clock generation unit, a CPU, a ROM, a RAM, and the like, and functions as an estimation unit and a decoding unit. In addition, the control device 18 outputs a driving pulse synchronized with the resonance frequency to the driving force supply device 9.
[0027]
The laser light source 5 is driven by a laser driving means 19 to output laser light. The laser driving means 19 is controlled by a control device 18.
[0028]
A reading window 1 a (see FIG. 3) is formed at the tip of the case 1, and the center line of the reading window 1 a coincides with the center line of the case 1. The vibration center axis P of the scanning mirror 6 coincides with the center line of the case 1, and the effective scanning range is substantially symmetric with respect to the vibration center axis P.
[0029]
As shown in FIG. 4, the first optical sensor 20 and the second optical sensor 20 serving as detection means are located at the target position (that is, at the same angle θ _{W on} the left and right from the scanning reference point O) with respect to the vibration center axis P. An optical sensor 21 is arranged. As shown in FIG. 5, each of the optical sensors 20 and 21 receives laser light and outputs detection signals S1 and S2. In this case, for example, the first optical sensor 20 detects the laser light as it scans. The signal S1 is output as shown in FIG. 5, and based on this, one cycle T of the scanning light is known. Accordingly, the angular velocity ω is detected.
[0030]
Angular velocity ω = 2π / T
Further, the effective scanning range S can be determined from the detection signals S1 and S2.
[0031]
Now, in the above configuration, the reading scan (trigger switch of the trigger switch) is performed in a state in which the user brings the reading window 1a of the case 1 close (for example, distance D) so as to be substantially parallel to the reading target on which the barcode is recorded. The control device 18 controls the laser drive device 19 to output laser light from the laser light source 5. Further, the control device 18 controls the driving force supply device 9 to vibrate the operation mirror 6, deflects the laser light, and hits (scans) the reading target.
[0032]
The laser beam is reflected by the light intensity corresponding to the black and white reflectance of the barcode on the reading target, and enters the photoelectric conversion element 7 via the lens 8. The photoelectric conversion element 7 outputs an electrical signal (analog signal) according to the amount of incident light corresponding to the reflectance. This output is given to the binarizing means 17 via the amplifying means 16, and the binarizing means 17 outputs a binarized signal according to the black and white of the barcode (in accordance with the reflectance). At this time, when the black and white of the barcode is the same width, the scanning speed changes in a simple vibration, so the scanning speed decreases as the distance from the scanning center increases. When digitized with the reference clock, binarization is performed as the distance from the scanning center increases. A high level region and a low level region of a signal (for example, black is high level and white is low level) are widened.
[0033]
However, the control device 18 detects a position where the reflectance of the scanning light changes based on the reference clock. That is, the reference clock number N in the effective scanning range S is measurable, and the time when the N / 2 reference clock number is counted from the detection signal S1 in the scanning forward direction (arrow R direction in FIG. 4) is the time “ t0 ”, and the time shifted from the center position“ t0 ”by one pulse time of the reference clock in the direction of arrow R is time“ t1 ”, and thereafter in the direction of arrow R, time“ t2 ”,“ t3 ”,.・ ・Conversely, from the time “t0”, the times “−t1”, “−t2”,... Sequentially in the backward direction (arrow L direction).
[0034]
Then, the control device 18 generates black width data and white width data as the width of the bar as follows. As shown in FIG. 4, when the distance from the scanning reference point O to the reading object 2 is D, the position X of the scanning light from the central axis is estimated as the following equation (6).
[0035]
X = D · tan (θ _A · sin (ω · t)) (6)
Here, t is any one of the times “t1”, “t2”,..., “−t1”, “−t2”,. Thus, the position X of the scanning light at the time from the central axis P (time based on the reference clock) can be estimated.
[0036]
Therefore, the width data W can be generated by taking the difference between the position X at the time tb at which the next binarized signal changes from the position X at the time ta at which the reflectance changes, that is, the time ta at which the binarized signal changes. It is.
Accordingly, the width data W is expressed by the following equation (3).
[Equation 5]

In this case, the angle θ _{A that} is ½ of the total scanning angle is a predetermined known value, the angular velocity ω is a value that has been measured and found, and the time when the reflectivity is switched, that is, binarization. The times ta and tb at which the signal changes are values that are detected and found, and thus W is obtained.
[0037]
Table 1 shows how the width data changes (changes away from the central axis) in one cycle of the reference clock using the above equation (3).
[Table 1]

[0038]
In this case, the number of reference clock 4000 in scanning one period, is set to 30 ° 1/2 of angle theta _A total scan angle. As can be seen from Table 1, when the width data near the center axis pole (width data between time t0 and time t1) is set as the reference width data “1”, the width data decreases as the distance from the center axis increases. That is, the width data matches the actual scanning position.
[0039]
The formula (3) (same as formula (1)) includes the following concept. That is, the width data corresponding to the reference clock cycle (the width data at the time from the time t0 to the time t1 (for example, 1 ms) on the central axis) is set to the reference width data “1” (this is the actual length, for example, 0.1 mm). The black and white width data of the barcode is obtained based on the difference between the scanning positions (estimated values) at which the binarized signal has changed and the reference width data.
[0040]
As a result, it is possible to obtain accurate width data of the barcode with a simple configuration while binarizing using the reference clock.
[0041]
Further, since the scanning mirror 6 is vibrated with the vicinity of the center line of the apparatus as the vibration center axis P and the effective scanning range S is substantially symmetric with respect to the vibration center axis P, the width data W is determined as an error. It can be generated without.
[0042]
Note that the angle θ _{A which} is ½ of the total scanning angle may be estimated by the two optical sensors 20 and 21. That is,
θ _W = θ _A · sin (ω · S / 2) = θ _A · sin (π · S / T)
Therefore, θ _A = θ _W / sin (π · S / T)
It becomes. Therefore, an angle θ _A that is ½ of the total scanning angle can be estimated from the measured S and T and the known θ _W.
[0043]
Further, in this way, an angle θ _A that is ½ of the total scanning angle is obtained for each cycle of the vibration motion (reciprocating motion) of the scanning mirror 6, and the angular velocity ω is obtained by one of the optical sensors 20 and 21. After that, the width data W may be obtained. According to this, even in a transition period at the beginning of scanning, an accurate angular velocity ω and an angle θ _A that is ½ of the total scanning angle can be obtained, and the width data W can be obtained accurately.
[0044]
In addition, when the angle θ _{A which} is a half of the entire scanning angle is known, either one of the two optical sensors 20 and 21 is provided to change the angular velocity ω to the vibration motion (reciprocating motion of the scanning mirror 6). ), The width data W may be obtained after obtaining each cycle. Accordingly, an accurate angular velocity ω can be obtained even in a transition period at the beginning of scanning, and the width data W can be obtained accurately.
[0045]
Further, the angular velocity ω and the angle θ _{A which} is a half of the total scanning angle may be stored in a storage unit such as a ROM or a non-volatile memory as a uniform constant instead of a measured value. According to this, there is no trouble of measuring the angular velocity ω and the angle θ _{A which} is ½ of the entire scanning angle. Further, the storage means may store correction values for correcting the angular velocity ω and the angle θ _A that is ½ of the total scanning angle. According to this, if the error is checked for the angular velocity ω or the angle θ _A which is ½ of the total scanning angle for each apparatus, the angular velocity ω as a constant can be obtained by storing this as a correction value by the storage means. And an angle θ _A that is ½ of the total scanning angle can be corrected.
[0046]
Further, the driving force supply device 9 may also serve as a detection unit. In this case, the driving force of the driving force supply device 9 for the reciprocating motion with respect to the scanning mirror 6, for example, a driving pulse, is applied at a certain frequency and at a substantially constant scanning position, so that the scanning position is detected at the timing of the driving pulse. It becomes possible.
[0047]
Further, the position of the scan may be estimated only when the scanning of the scanning mirror 6 is in a stable state (estimating means is made effective). The width data W can be generated with high accuracy by eliminating the width data acquisition.
Moreover, you may provide the setting means which an operator can set whether the said estimation means is validated.
Further, as an expression for obtaining the width data W, an approximate expression approximate to the expression (1) may be used. In this case, the approximate expression may be the following expression (2).
[0048]
[Formula 6]

Where W: width data of the sign, ta, tb: time when the binarized signal changes,
A and B are constants, and tave is (ta + tb) / 2.
[0049]
For example, the constant A is 3.2 × 10 ⁻¹³ and the constant B is 7.08 × 10 ⁻⁷ . Table 2 shows the calculation results when ta and tb are appropriately selected. As can be seen from the comparison between Table 2 and Table 1, accurate width data can be obtained.
[Table 2]

[0050]
The optical information reader of the present invention is not limited to a hand-held bar code reader, and may be applied to a fixed bar code reader. Further, as the driving force supply means for supplying the driving force to the scanning means, a pulse motor may be used.
[Brief description of the drawings]
FIG. 1 is a diagram showing an optical mechanism and an electric block configuration. FIG. 2 is a plan view of a driving force supply device. FIG. 3 is a plan view showing an optical mechanism portion. (A) shows the output of the first optical sensor, (b) shows the effective scanning range. FIG. 6 shows the relationship between the analog signal waveform, the reference clock, and the binarized signal waveform. ] Figure showing the state of conventional binarized signal output [Explanation of symbols]
1 is a case, 2 is an object to be read, 3 is a barcode (label), 4 is an optical mechanism, 5 is a laser light source, 6 is a scanning mirror (scanning means), 7 is a photoelectric conversion element (photoelectric conversion means), and 9 is driven A force supply device (driving force supply means), 11 is a spring member, 14 is a magnet, 15 is an electromagnetic coil, 17 is a binarization means, and 18 is a control device (estimation means, decoding means).

Claims (4)

A light source that projects light;
A scanning means configured to reciprocate by a vibration motion, reciprocating at a resonance frequency of a vibration system, and deflecting light from the light source toward a label using light reflectance such as a barcode;
Photoelectric conversion means for receiving reflected light from the sign and converting it into an analog signal corresponding to the reflectance;
A / D conversion means for quantizing the analog signal and converting it into a digital signal;
Detecting means for detecting at least one point of the scanning position;
Estimating means for estimating a scanning position of the light;
A decoding means for generating width data of the marker based on the scanning position estimated by the estimation means and the digital signal;
Based on the signal from the detection means, the angular velocity ω of the reciprocating motion used in the following formula (1) is calculated for each period of the scanning means, and the estimation means and the decoding means have the following formula (1): An optical information reading apparatus characterized in that width data of the sign is obtained by the following.

Where W: width data of the sign, θ _A : half of the total scanning angle,
ω: angular velocity of reciprocating motion, ta , tb : time when the digital signal changes. The detecting means detects two points of the scanning position. Based on the signal from the detecting means, the angular velocity ω and an angle θ _A that is ½ of the total scanning angle are detected by the scanning means. 2. The optical information reading apparatus according to claim 1, wherein calculation is performed for each period of reciprocation . The optical information reading apparatus according to claim 1, further comprising a storage unit, wherein the storage unit stores the angular velocity ω and an angle θ _A that is ½ of the total scanning angle as constants . 4. The storage unit according to claim 1, further comprising a storage unit, wherein the storage unit stores a correction value for correcting the angular velocity ω and an angle θ _A that is ½ of the total scanning angle. The optical information reading device described .

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