JP4174252B2 - Optical deflection apparatus, image forming apparatus using the same, and driving method thereof - Google Patents

Description

によって与えられる。
【０１４６】
ここで、ＢＣ間の長さはφ１であるので、最大変位角θｃは、
θｃ＝２×（ＴＡ＋ＴＢ）／Ｔ×φ１
となる。
【０１４７】
つぎに、Ｊ’Ｄ上の任意の位置と、その位置の反射光２２２の通過時間との関係について説明する。まず、ＡＬの長さは、［ＤＥ＋ＢＣ＋ＩＪ］から［ＤＥ＋ＢＭ］分（横軸よりも上側の長さ）を差し引いてさらに［ＩＪ］分差し引いた長さに等しく、［ＤＥ＋ＢＭ］の長さは［ＤＥ＋ＢＣ＋ＩＪ］の長さの半分であるので、上記のＤＥ、ＩＪの式から

が成り立つ。
【０１４８】
また、線分ＡＫの傾きは、ＢＣ／ＴＡであり、点Ａを反射光２２２が通過する時間をｔ１、点Ｋを反射光２２２が通過する時間をｔ０とすると、［ＡＬ＝ＢＣ／ＴＡ×（ｔ０−ｔ１）］より、
ｔ０＝ｔＡ×（ｔＡ＋ｔＢ＋ｔＣ−ｔＤ）／２／（ｔＡ＋ｔＢ）＋ｔ１
である。
【０１４９】
以上の式より、Ｊ’Ｄ上の任意の位置となる変位角φαは、その位置の反射光２２２の通過時間をｔαを用いて

＋ｔＢ）＋ｔ１｝
と表される。
【０１５０】
本実施例によると、鋸波駆動しているガルバノミラーの変位角を示す情報を取得することができる。実際には、ガルバノミラーをノコギリ波駆動した場合、理想的なノコギリ波状にはならないが、一般的な駆動条件であれば、上記のように理想的なノコギリ波と近似して算出しても問題ない。
【０１５１】
（実施例５）
図８は、本発明の実施例５の光偏向器の模式的な構成図である。本実施例では、光センサ２０３，２１２をスクリーン上でなく、偏向装置内に設置している。
【０１５２】
具体的には、図８に示すようにガルバノミラー２０２と垂直走査ミラー２２１との間にビームスプリッタ２０４を設け、これにより進路が変更された検出用走査光２０６の光路に光センサ２０３，２１２を配置している。また、ビームスプリッタ２０４によって進路の変更されない描画用走査光２０５が投影面２１０に照射される。
【０１５３】
図８に示すように光センサ２０３，２１２を配置すると、全走査検出を行うことができるというメリットがある。すなわち、図５に示す場合に比して投影面２１０の垂直方向の走査に拘わらず、水平方向の走査の度に光センサ２０３，２１２に光源２０１からの光が入射するようになるので、より精度よく光源２０１及びガルバノミラー２０２の制御を行うことができる。
【０１５４】
（実施例６）
図９は、本発明の実施例６の光偏向器の模式的な構成図である。本実施例では、光源２０１の他に、光センサ２０３，２１２でガルバノミラー２０２の変位波形を検出するために別途検出用光源２１１を光源２０１からの光の光路外に設けている。
【０１５５】
検出用光源１１は、走査光との干渉を避けるため、異なる波長を用いる。ガルバノミラー２０２に対する、検出用光源１１からの入射角と、変調手段を有する光源２０１からの入射角は、異なっている。光センサ２０３、２１１は、検出用光源の走査光を検出できる位置に配置される。なお、他の構成は図５と同様である。
【０１５６】
図９に示すように検出用光源２１１を設けると、図８に示す場合に比して、投影面への光の照射光量が低下しなくなるので、描画の輝度を相対的に高めることが可能となる。また、検出用ビーム系の大きさや、光センサの配置を最適化することが容易となり、高精度な変位角を示す情報の取得が可能となる。
【０１５７】
以上、本発明の実施例１−６では、ガルバノミラー２０２の光反射面の変位角を検出するタイミングセンサとして、光センサ２０３，２１２を用いた場合を例に説明したが、タイミングセンサは光センサに限定されず、これに代えて、ガルバノミラー２０２に内蔵された静電センサ、コイル等の磁気センサを用いてもよい。また、光センサ２０３，２１２の一方が静電センサで、他方が磁気センサであってもよい。
【０１５８】
（実施例７）
図１２は、実施例１〜実施例６で説明した光偏向器ユニットのいずれかを備える画像形成装置の模式的な構成図である。なお、図１２において図１３と同様の部分には同一符号を付している。
【０１５９】
水平方向走査のガルバノミラー２０２は、共振型で約２３ｋＨｚの正弦波の駆動信号を印加している。ガルバノミラー２０２の出射光は、タイミングセンサ２０３，２１２に入射される。
【０１６０】
垂直走査ミラー（ガルバノミラー）２２１は、約６０Ｈｚで帰線期間が１０％の鋸波の駆動信号を印加している。ガルバノミラー２２１の出射光は、タイミングセンサ２０３’，２１２’に入射される。
【０１６１】
光源２０１は、光出力約３０ｍＷの半導体レーザを用い、パルス幅変調で直接変調を行っている。なお、水平方向及び垂直方向の変位角を示す情報は、実施例１，２及び実施例５で説明した手法を用いることによって取得している。
【０１６２】
それぞれの走査方向に対して、変位角を示す情報を取得し、駆動の安定化制御及び、変調開始／終了タイミングの生成を行った。本実施例によれば、異なる走査方向及び走査速度のそれぞれの変位角を示す情報を取得することができ、安定した高品質な画像を表示させることができる。
【０１６３】
さらに、本実施例では、画像表示装置を例に説明したが、光偏向器ユニットは、レーザプリンタなどの画像描画装置、レーザ顕微鏡等の走査型読み取り装置などにも備えることができ、また該光偏光ユニットを単体の光偏向装置として用いることができる。
【０１６４】
以上の実施例では、画像表示装置を例に説明したが、光偏向器ユニットは、レーザプリンタなどの画像描画装置、レーザ顕微鏡等の走査型読み取り装置などにも備えることができ、また該光偏光ユニットを単体の光偏向装置として用いることができる。
【０１６５】
【発明の効果】
本発明によれば、正弦波のような非直線的走査を行なう光偏向器を用いた画像表示装置の、駆動信号と偏向器の実際の運動との関係、さらには駆動信号と実際のスクリーン上の光ビーム走査との関係が、何らかの原因で所定状態からずれたばあい、従来の偏向器の動きを自動検出する方法に比べ、検出器の数が少なくてすみ、また、得られたデータから未定のパラメータを決定する演算も簡単で高速であるという効果がある。
【図面の簡単な説明】
【図１】本発明の光偏向装置とそれを用いた画像形成装置の模式的な構成図である。
【図２】図１の各部で生成される種々の信号の説明図である。
【図３】図１の制御回路の構成を示すブロック図である。
【図４】図１の画像形成装置の変形例である。
【図５】本発明の別の光偏向装置とそれを用いた画像形成装置の模式的な構成図である。
【図６】図５の各部で生成される種々の信号の説明図である。
【図７】スクリーンとガルバノミラーの位置関係の説明図である。
【図８】図５の画像形成装置の変形例である。
【図９】図５の画像形成装置の変形例である。
【図１０】光偏向器の駆動信号に対する振動の関係を示す説明図である。
【図１１】共振型ガルバノミラーの駆動周波数と最大変位角および位相の関係を示す図である。
【図１２】図５の画像形成装置の変形例である。
【図１３】本発明の第１の実施例の光偏向装置である。
【図１４】本発明の第４の実施例の光偏向器の振動を示す説明図である。
【符号の説明】
２０１ 光源
２０２ ガルバノミラー
２０３，２１２ 光センサ
２０４ ビームスプリッタ
２０５ 描画用走査光
２０６ 検出用走査光
２０７ ガルバノミラーの駆動中心点を結ぶ線
２１０ スクリーン
２１１ 検出用レーザ光源
２２１ 垂直走査ミラー
２２２ 反射光
２２３ 描画領域
２２４ 非描画領域
２２６ 生成手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical deflecting device (herein referred to as an optical deflecting device or an optical deflector unit including an optical deflector and its drive part and control part) and an image forming apparatus, and more particularly to a laser display, a laser printer, The present invention relates to an optical deflector unit such as a scanner and an image forming apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known an optical deflection scanning device that deflects a light beam emitted from a light source such as a laser using an optical deflector such as a polygon mirror or a galvanometer and scans a screen or an exposure surface. The polygon mirror is a deflector that applies a periodic drive signal to a plurality of polygonal mirrors and rotates the mirror to perform optical scanning in one direction on the screen. The galvanometer causes a mirror surface to perform a reciprocating reciprocating motion by applying a periodic drive signal, and causes a reciprocating light beam scanning on the screen. Of course, it is also possible to use only one scan with the light beam partially off.
[0003]
Known driving methods for galvanometers include electrostatic driving, electromagnetic driving, and those using the piezoelectric effect. The vibration waveform is generally a sine wave, but by appropriately setting the drive voltage waveform, vibration such as a triangular wave and a sawtooth wave is also possible. Further, when the galvanometer has a natural vibration, a vibration with a maximum amplitude can be obtained with a minimum power by applying a drive signal having a frequency corresponding to the galvanometer to cause resonance.
[0004]
There has been proposed a projection type image display device that uses these optical deflectors to project and display an image of a television or the like on a screen. Some of these image forming apparatuses include an optical deflector that scans laser light emitted from a laser light source such as an LD in the horizontal and vertical directions by resonating and rotating two galvanometer mirrors. .
[0005]
In such an image display device using an optical deflector, a periodic drive signal applied to the deflector, a rotational motion or a reciprocating rotational motion actually generated in the deflector, and a periodic scanning of the light spot generated on the screen are performed. In general, the following differences usually occur. This will be described below.
[0006]
FIGS. 10A to 10E show the temporal relationship between the drive voltage applied to the galvanometer and the position of the light spot actually generated on the screen. FIG. 10A shows the time change of the driving voltage applied to the galvanometer, and FIGS. 10B to 10E show the time change of the position of the light spot reciprocating on the screen. Assuming that the response of (b) is standard, (c) shows the case where the phase is shifted, (d) shows the case where the amplitude is changed, and (e) shows the case where the center position is shifted. In practice, these may appear together.
[0007]
The main causes of the phase, amplitude, and center position deviation are the galvanometer characteristic variation, temperature variation, mirror and light source position variation, and mirror and screen position variation.
[0008]
The vibration characteristics of a galvanometer vary depending on the dimensions of the mirror and the torsion shaft that supports it, the distance between drive electrodes or electromagnetic coils, etc., but these variations are unavoidable, and galvanometers have subtle characteristics. There is a difference. For this reason, the response is different for the same voltage, and the maximum displacement angle, that is, the amplitude and the phase deviate from the reference value.
[0009]
In the case of resonance vibration, the natural frequency changes when the temperature fluctuates and deviates from the frequency of the drive signal. This also shifts the amplitude and phase. FIGS. 11A and 11B are diagrams schematically showing this, where FIG. 11A shows the drive frequency and amplitude, and FIG. 11B shows the relationship between the drive frequency and phase. The maximum amplitude is obtained when the driving frequency is in the state A corresponding to the resonance point, but when the resonance frequency is shifted to the state B, the amplitude is decreased and the phase is shifted. The phase shift is reversed depending on the direction of fluctuation, such as a delay when the resonance frequency fluctuates higher and a advance when the resonance frequency fluctuates lower.
[0010]
If the relative position of the light source with respect to the mirror varies in addition to the characteristic variation and temperature variation of the individual mirrors, the incident angle of the light beam to the mirror changes, and therefore the scanning center position on the screen shifts. Further, when the screen setting position is shifted, the center position is further shifted.
[0011]
In the above, the case of sinusoidal vibration is described as an example, but the same applies to other vibrations. In contrast, when the deflector is a polygon mirror, the maximum displacement angle is determined by the number of mirror surfaces, so the variation in scanning amplitude is not in principle and is not resonant. There is no change in amplitude and phase due to.
[0012]
On the other hand, the light beam emitted from the light source undergoes strong and weak modulation by the image signal and is displayed as an image on the screen, but the start and end timing of the modulation is the image in a predetermined area on the screen. As shown, it is synchronized with the mirror drive signal. However, as described above, if the relationship between the drive signal and the light spot on the screen deviates from the reference, a predetermined image cannot be obtained correctly. For example, as shown in FIG. 10 (c), when the phase is shifted and the light spot is scanned with a delay from a predetermined timing, the image is displayed upstream of the predetermined position. In the case of scanning in one direction, such as a polygon mirror, the image is only slightly shifted to the side, and if it is mild, there is no problem. However, in the case of reciprocating scanning, the image is shifted in the opposite direction on the way back and forth. As a whole, a double image can be seen, resulting in a fatal defect. A change in amplitude or a change in the center position also causes a significant defect in the image depending on the degree.
[0013]
In order to avoid this defect, in the actual display device, the state of vibration of the galvanometer or the movement of the light spot on the screen is monitored, thereby adjusting the drive signal of the deflector or the modulation timing of the light beam. is required. Conventionally proposed monitoring methods include the following.
[0014]
The galvanometer mirror described in Japanese Patent Registration No. 2657769 is provided with a permanent magnet. By superimposing a high frequency on the drive current, a drive coil on the galvanometer mirror and a detection coil arranged opposite to the galvanometer mirror are provided. The displacement angle of the galvanometer mirror is detected from the change in mutual inductance.
[0015]
In addition, in Japanese Patent Registration No. 30111144, by superimposing a high-frequency AC voltage having a minute voltage value in addition to a driving voltage, a current difference flowing through the fixed electrode of the galvanomirror electrode portion of the capacitor structure can be used. A method for measuring the swing position is described.
[0016]
Furthermore, Japanese Patent Application Laid-Open No. 64-28535 proposes a method of detecting reflected light from a polygon mirror at two locations and measuring the rotational variation of the mirror, that is, jitter from the time difference therebetween.
[0017]
[Problems to be solved by the invention]
The displacement angle sensor described in Japanese Patent Registration No. 2657769 and Japanese Patent Registration No. 30111144 is built in the deflector and has the advantage that it can detect the fluctuation of the galvanometer mirror over the entire period. It is difficult to detect a minute amplitude and phase shift. The detector needs to have sufficient time resolution to determine the modulation start timing. However, in the deflector that performs minute vibration, changes appearing in the coil inductance and displacement current are very small in the first place. Therefore, it is difficult in practice to determine the displacement angle with high accuracy because it increases the complexity and cost of the apparatus.
[0018]
On the other hand, Japanese Patent Laid-Open No. 64-28535 detects the reflected light of a polygon mirror and has a high time measurement accuracy. However, if this is applied to sine wave vibration by a galvano mirror, there are the following difficulties.
[0019]
The sinusoidal vibration has an amplitude A, a phase δ, and a center position X (assuming that the period T is constant and known).₀These three parameters are uniquely determined. The time variation of the spot position X on the screen is determined using these parameters.
X = Asin (2πt / T−δ) + X₀
It is expressed. As described above, these parameters vary depending on various factors. If all of these parameters are known, the position of the spot on the screen at an arbitrary time can be known.
[0020]
When the parameters are determined and the above equation is established, when it is desired to display the image in the range of XA <X <XB, assuming that both end positions of the image on the screen are XA and XB, the above equations correspond to XA and XB. Time tA and tB
XA = Asin (2πtA / T−δ) + X₀
XB = Asin (2πtB / T−δ) + X₀
The modulation signal sent to the light source may be controlled so that the modulation of the image signal starts at tA and ends at tB. The time reference for tA and tB may be selected appropriately from the timing of a fixed signal having a period of vibration of the galvanometer mirror, but in the following, this is based on the rise of the signal synchronized with the drive signal of the galvanometer mirror. .
[0021]
In this way, by automatically calculating the modulation timing and applying the actual modulation based on it, the image will always be displayed regardless of any change in the deflector characteristics or misalignment with the light source or screen. A predetermined size can be displayed within a predetermined area.
[0022]
Therefore, consider determining the above three parameters.
[0023]
First, detect light at two places on the screen.
X1 = Asin (2πt1 / T−δ) + X₀
X2 = Asin (2πt2 / T−δ) + X₀
Even if the measurement data is obtained, the three unknowns A, δ, X₀Obviously, it is necessary to detect light at three or more positions.
[0024]
In addition, if the light is detected at three locations, the third measurement data
X3 = Asin (2πt3 / T−δ) + X₀
From these, three unknowns A, δ, X₀It is not easy to determine. The reason is that δ is included as a non-linear parameter, which requires a complicated calculation and takes a long time. In particular, when the above detection is performed for each scanning line, high-speed calculation within one line scanning time is required, but it is difficult to satisfy the request with a simple circuit.
[0025]
Of the three parameters, X₀Can be easily adjusted by moving the deflector unit position or the screen position while watching the image of the light beam projected on the screen, in which case there are two unknown parameters, but there are still two detectors Necessary and the computational complexity of determining δ still remains.
[0026]
Also, taking the difference between the above two data,
X1−X2 = A {sin (2πt1 / T−δ) −sin (2πt2 / T−δ)}
X₀Disappears, but two parameters A and δ remain, and the amplitude cannot be uniquely determined from the difference data.
[0027]
On the other hand, in the case of a polygon mirror, the time change of the spot position on the screen is linear after correction by the fθ lens.
X = A (t / T−δ) + X₀
It becomes. Again, amplitude A, phase δ, center position X₀Are the same, but δ and X₀The two are -Aδ + X₀In effect, there are two parameters. This is due to the fact that both the phase change and the center position change appear as image position shifts and cannot be distinguished on the screen. Therefore, in this case, measurement data at two locations
X1 = A (t1 / T−δ) + X₀
X2 = A (t2 / T-δ) + X₀
Therefore, the unknown amount disappears and the position change on the screen can be completely reproduced. Specifically, first, take the difference data
X1-X2 = (A / T) (t1-t2)
A / T is obtained from This is then substituted into the formula of X1 and −Aδ + X₀And substituting it into the formula of X
X = (X1-X2) / (t1-t2). (T-t1) + X1
Get.
[0028]
As described above, since the galvanometer reciprocates, it is not possible to use a scanning light timing detection method like a conventional polygon mirror having a one-way, constant scanning speed. Furthermore, simply detecting the scanning timing makes it difficult to estimate the displacement angle at times other than the detection timing because the scanning speed of the galvano mirror changes. When the galvanometer mirror is mounted on a laser display or the like, the laser beam intensity is modulated by image information while reciprocating the light with the galvanometer mirror. To generate the modulation start / end timing, the displacement angle at an arbitrary time is changed. It is necessary to make an estimation.
[0029]
The present invention relates to the relationship between the drive signal and the actual movement of the deflector of the image display device using the optical deflector that performs non-linear scanning such as a sine wave, and further the drive signal and the actual light on the screen. If the relationship with the beam scanning deviates from a predetermined state for some reason, the conventional method of automatically detecting the movement of the deflector requires an increase in the number of detectors, and the obtained data is undecided. The object is to solve the problem that the calculation for determining the parameters is complicated and difficult.
[0030]
[Means for Solving the Problems]
  The present invention that achieves the above object includes a light source that emits a light beam, a modulation unit that modulates the light beam emission intensity of the light source, a modulation signal generation unit that outputs a modulation signal to the modulation unit, and a light source An optical deflector for deflecting the emitted light beam, and the deflected light beamRunDrive means for driving the optical deflector to be inspected, and drive signal generating means for outputting a drive signal of a predetermined period to the drive means;RunAn optical deflecting device having measuring means for measuring a first time at which a specific position on the scanning line of the examined light beam passes on the forward path and a second time at which the light beam passes on the backward path, respectively, Furthermore, from the first and second times, the drive signal of the optical deflectorStart timingDisplacement waveform of the optical deflector with respect toDisplacement start timingDelay timeDelay time equivalent toFrom the delay time data calculating means for calculating data, the first time and the second time, and the delay time data, the light beam modulation start timeEvery momentThere is provided an optical deflecting device comprising timing data calculating means for calculating corresponding timing data, wherein the modulation signal generating means outputs a modulation signal to the modulating means based on the calculated timing data To do.
  Further, the present invention for achieving the above object includes a light source that emits a light beam, a modulation unit that modulates the light beam emission intensity of the light source, a modulation signal generation unit that outputs a modulation signal to the modulation unit, An optical deflector that deflects the light beam emitted from the light source, and the deflected light beamRunDrive means for driving the optical deflector to be inspected, and drive signal generating means for outputting a drive signal of a predetermined period to the drive means;RunA first time at which the examined light beam passes through the first specific position on the scanning line in the forward path, a second time at which the light beam passes through the backward path, and a second specific position on the scanning line of the light beam at the forward path or A light deflecting device having a measuring means for measuring a third time passing on the return path, wherein the light deflecting device further starts driving signals of the light deflector from the first time and the second time. ofStart timingDisplacement waveform of the optical deflector with respect toDisplacement start timingDelay timeDelay time equivalent toFrom the delay time data calculating means for calculating the data, the first to third times, and the delay time data, the light beam modulation start timeEvery momentThere is provided an optical deflecting device comprising timing data calculating means for calculating corresponding timing data, wherein the modulation signal generating means outputs a modulation signal to the modulating means based on the calculated timing data To do.
  In addition, the present invention that achieves the above object provides a light beam from a light source.RunA method of driving an optical deflectorRunA step of measuring a first time passing through a specific position on the scanning line of the scanned light beam in a forward path and a second time passing through a specific position on the return path, and the light deflection from the first and second times Of the drive signalStart timingDisplacement waveform of the optical deflector with respect toDisplacement start timingAnd calculating the delay time of the light beam from the first and second times and the delay time.Every momentThere is provided a method of driving an optical deflector comprising: calculating corresponding timing data; and modulating a light beam from the light source based on the timing data.
  In addition, the present invention that achieves the above object provides a light beam from a light source.RunA method of driving an optical deflectorRunA first time at which the examined light beam passes through the first specific position on the scanning line in the forward path, a second time at which the light beam passes through the backward path, and a second specific position on the scanning line of the light beam at the forward path or A step of measuring a third time passing in the return path, and a driving signal of the optical deflector from the first and second times.Start timingDisplacement waveform of the optical deflector with respect toDisplacement start timingAnd calculating the delay time of the light beam from the first to third times and the delay time.Every momentCalculating corresponding timing data; modulating a light beam from the light source based on the timing data;
An optical deflector driving method is provided.
  Further, the present invention for achieving the above object includes a light source that emits a light beam, a modulation unit that modulates the light beam emission intensity of the light source, a modulation signal generation unit that outputs a modulation signal to the modulation unit, An optical deflector for deflecting the light beam emitted from the light source, a driving means for driving the optical deflector to scan the deflected light beam, and a drive signal generation for outputting a driving signal of a predetermined period to the driving means Scanned by an optical deflecting device having means and measuring means for measuring a first time at which a specific position on the scanning line of the scanned light beam passes on the forward path and a second time at which the scanned light beam passes on the return path, respectively. A method for determining a modulation start time of a light beam,
  Measuring each of a first time at which a specific position on the scanning line of the scanned light beam passes on the forward path and a second time at which the scanned light beam passes on the return path;
  Calculating a delay time of the displacement start timing in the displacement waveform of the optical deflector with respect to the start timing of the drive signal of the optical deflector from the first and second times;
  Calculating a light beam modulation start time from the first and second times and the delay time;
There is provided a method for determining a modulation start time of a light beam.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0032]
1. Embodiment 1
First, consider the case where the scan center position on the screen can be easily adjusted by matching the relative positions and directions of the screen and deflector while viewing the image. Adjustment is performed by moving the screen or by moving the deflecting device.
[0033]
In this case, the center position shift X₀The light spot movement on the screen as not
X = Asin (2πt / T−δ)
If the two unknown parameters A and δ are determined, the movement of the light spot can be completely detected. This case will be described below as Embodiment 1.
FIG. 1 shows the configuration of the light deflection apparatus of this embodiment.
[0034]
FIG. 1 shows an example of an optical deflection apparatus that performs main scanning and sub-scanning to project a two-dimensional image onto a screen. This light deflection apparatus outputs an electric signal when incident light source 201 and reflected light 222 of main scanning galvanometer mirror 202, sub-scanning galvanometer mirror 221, and galvanometer mirrors 202 and 221 for scanning light from light source 201. An optical sensor 203 such as a photoelectric conversion element, a measurement circuit 106 that receives the output of the optical sensor and measures the time when the light passes through the sensor position, and acquires information indicating the displacement angle of the main scanning galvanometer mirror 202 based on the measurement result The control circuit 107, the deflector drive circuit 108, and the light source drive circuit 109 that generate a synchronization signal synchronized with the drive signal applied to the main scanning galvanometer mirror 202 and a timing signal indicating the drawing start timing and drawing end timing of the light source 201. Consists of.
[0035]
The main scanning galvanometer mirror 202 reciprocates and moves the light spot on the screen 210 in the direction of arrow A. The sub-scanning galvanometer mirror 221 deflects light in a direction perpendicular to A.
[0036]
The optical sensor 203 is disposed near the upper end of the screen 210. This optical sensor is a timing sensor that generates a detection signal 130 at a timing when a light beam is scanned in the main scanning direction (arrow A) and passes over the sensor 203. The detection signal 130 of the timing sensor 203 is sent to the measurement circuit 106. The measurement circuit measures the time difference between the reference signal 131 and the detection signal 130 sent from the control circuit 107 by a built-in counter (not shown), and outputs the result 132 to the control circuit 107. The reference signal 131 is a clock signal that is generated inside the control circuit 107 and gives the deflection cycle of the main scanning galvanometer mirror 202. A galvano mirror drive signal 133 synchronized with this is also generated in the control circuit 107 and sent to the drive circuit 108. In response to this, the drive circuit applies an AC voltage to the electrostatic electrodes of the galvano mirrors 202 and 221 for driving. To do. Further, in synchronization with the reference signal, a light source modulation signal 134 is generated in the control circuit at a predetermined timing and is sent to the light source modulation circuit 109. With this modulation signal, the light intensity emitted from the light source is modulated, and an image is formed on the screen.
[0037]
In this embodiment, the timing sensor 203 generates a signal when the displacement angle of the main scanning galvanometer mirror 202 reaches a predetermined value. This timing sensor detects both the reciprocation of the light spot on the screen, that is, the galvanometer. Regardless of whether the displacement angle of the mirror 202 is a direction toward the maximum position or a direction returning from the maximum position, a detection signal is output at the timing when the light spot comes there. Therefore, the timing signal (detection signal 130) is generated twice in one cycle. From the output signal of this sensor, the phase of the displacement angle of the galvanometer mirror and the maximum displacement angle are obtained by calculation by the method described below.
[0038]
The position of the timing sensor 203 may be a position where the displacement angle of the galvanometer indicated by a dotted line 225 in FIG. 1 is 0 degree, that is, an arbitrary position other than the scanning center, but the position is set to a predetermined value in advance in the control circuit. (See FIG. 3 described later).
[0039]
In this embodiment, since a sinusoidal drive signal is applied to the galvanometer mirror, the change in the displacement angle with time is symmetric between the forward path and the backward path. However, the drive signal waveform is not limited to a sine wave, and may be a triangular wave, a sawtooth wave, or the like.
[0040]
Below, the case where the galvanometer mirror 202 is resonantly driven by applying a sinusoidal drive signal will be described.
[0041]
FIG. 2 is an explanatory diagram of various signals generated by each unit in FIG. 2A is a reference signal synchronized with a clock signal of a clock generation circuit built in the control circuit, and FIG. 2B is a drive signal applied to a galvanomirror according to a drive signal (not shown) synchronized with FIG. The response waveform of the galvanometer mirror, (c) is the detection signal of the photosensor, (d) is calculated by the procedure described below, and the reproduced galvanometer mirror deflection angle, that is, the time change of the position of the light beam on the screen is shown. Show.
[0042]
In FIG. 2, φ is the displacement angle from the drive center point of the galvano mirror to the position where the optical sensor is installed, ± θc is the maximum displacement angle of the galvano mirror, and Dc is from the rise of the drive signal in FIG. ), The delay time until the rise of the response waveform, T is the period of each signal in FIG. 2, and td1 and td2 are the time differences from the rise of the drive signal to the output of each timing signal.
[0043]
Incidentally, the delay time Dc is generated in the resonance operation of the galvano mirror, the drive system of the galvano mirror, and the electrical system of the optical sensor.
As shown in FIG. 2, the optical sensor 203 is arranged so as to output a timing signal when the reflected light 222 from the galvanometer mirrors 202 and 221 deviates by a displacement angle φ from the rotation center point.
[0044]
Since the time change φ (t) of the displacement angle is a sine wave,
φ (t) = θcsin {2π (t−Dc) / T}
The displacement angle φ of the sensor position and the two detection timings td1 and td2 are
φ = θcsin {2π (td1−Dc) / T}
φ = θcsin {2π (td2-Dc) / T}
Are in a relationship.
[0045]
Accordingly, the delay time Dc and the maximum displacement angle θc can be obtained from the detection data φ and td1 and td2 by the following formulas (1) and (2), respectively.
[0046]
Dc = (1/4) (2td1 + 2td2-T) (1)
θc = φ / sin {(π / T) (td1−td2 + T / 2)} (2)
Depending on which of td1 and td2 is the forward pulse and which is the backward pulse, Dc calculated by equation (1) is deflected from Dc defined in FIG. 10, that is, from the rising of the drive signal in one direction. The time until the device rises in the same direction may differ by T / 2, but the sensor position is shifted from the scanning center in a predetermined direction, the difference between td1 and td2 is calculated, and the value is T By determining whether or not it is greater than / 2, it is possible to determine which is the forward path or the return path, and thus there is no arbitrary determination of Dc.
[0047]
Further, when the sensor 203 is placed at the scanning center position 225, θc cannot be obtained because φ = 0 in equation (2). Therefore, in this sense, it is necessary to displace the sensor 203 from the center.
[0048]
Expression (1) is a linear calculation between the measured sensor position passage times td1 and td2 and the scanning period T. In this case, since the vibration waveform is reciprocally symmetrical, Dc can be calculated by the sum of the average value of the two passage times and T / 2. Therefore, a complicated calculation process of solving the nonlinear equation is not required, and the calculation can be performed with a simple arithmetic circuit in a short time. The reason why Dc can be obtained by such simple calculation is that reciprocal scanning is detected and data at different times at the same position is used.
[0049]
In this way, since two unknown parameters have been determined, the waveform of FIG. 2D, that is, the deflection angle of the deflector at an arbitrary time is known. Using this result, the start and end timings of modulation applied to the laser beam are calculated according to the image signal. Specifically, if the displacement angles corresponding to the start and end positions of the image are φA and φB, respectively, the start time tA and the end time tB are respectively
tA = (T / 2π) (arcsin (φA / θc) + Dc) (3)
tB = (T / 2π) (arcsin (φB / θc) + Dc) (4)
As required.
[0050]
Note that the sine function in Expression (2) and the arcsin function in Expressions (3) and (4) are frequently used functions, and can be calculated in a short time with an arithmetic routine built in the control circuit.
[0051]
Hereinafter, the operation of the control circuit 107 of FIG. 1 will be described with reference to FIG. FIG. 3 is a block diagram showing an internal configuration of the control circuit. The control circuit includes at least a controller 301, an arithmetic circuit 302, and a memory 303.
Scan period data and sensor position data are stored in the memory 303 in advance.
[0052]
When the detection pulse of the timing sensor is generated after the start of scanning, the measurement circuit measures the passage time and sends the result 132 to the control circuit 107. The controller 301 records time data received from the measurement circuit in the built-in memory 303.
[0053]
When the measurement of the two timings is completed by the reciprocation of the light beam, the controller reads the data of two passage times recorded in these memories and sends them to the arithmetic circuit 302, which corresponds to equations (1) and (2). Perform the operation and record the result in memory. For this calculation, scan cycle data is also read from the memory and used.
[0054]
Next, the values of the displacement angle φA at the display start position and the displacement angle φB at the display end position stored in advance in the memory 303 are read, and the modulation start timing tA and the modulation end timing tB are calculated by the equations (3) and (4). To do.
[0055]
In the subsequent scanning, the light source modulation signal 134 is controlled to start modulation according to the image at the timing when the tA time has elapsed and to end the modulation when the tB time has elapsed. That is, the controller 107 generates a galvanometer mirror drive signal 133 in synchronization with the reference signal and sends it to the galvanometer drive circuit, then generates a light source modulation start signal at a time delayed by tA, and sends it to the light source modulation circuit. A light source modulation end signal is generated and sent to the light source modulation circuit at a time delayed by a certain amount. Further, during the time tA and tB, image data is read from the image memory, modulated to be a light source modulation signal, and sent to the light source modulation circuit.
[0056]
In the above operation, the intermediate calculation data Dc and θc may be calculated simultaneously in the calculation process of equations (3) and (4).
[0057]
The calculation may be performed using detection signals generated in each cycle individually or using an average of detection signals for a plurality of cycles. The former method can be employed when timing detection is performed only in a part of the period of the response waveform of the galvanometer mirror, and the time until the control of the drive signal of the galvanometer mirror can be shortened. On the other hand, when the latter method is adopted, detection accuracy is improved by integration averaging or the like.
[0058]
Hereinafter, each part of this embodiment will be described.
[0059]
(About light source 201)
The light source 201 is preferably capable of modulating the emitted light, such as a gas laser or a solid-state laser having a modulator, or a light source capable of direct modulation such as a semiconductor laser or an LED. As the modulation method of the light source 201, a pulse width modulation method or an intensity modulation method can be used. In the present embodiment, the intensity modulation method has been described.
[0060]
(About galvanometer mirrors 202 and 221)
The galvanometer mirrors 202 and 221 may be any one that drives a galvanometer with a periodic drive waveform, a silicon micro scanner manufactured by using a semiconductor process, or an actuator that reciprocates around a rotation axis. The driving frequency may be any frequency as long as the galvano mirror 202 can be driven.
[0061]
(About the timing sensor 203)
As the timing sensor 203, a light detection type using a beam detector or the like, a unit integrated with an optical deflector unit, or the like can be used.
[0062]
When the timing sensor 203 is an optical sensor manufactured by a semiconductor process or an electrostatic sensor, an optimum sensor can be arranged at each displacement point, and the sensor arrangement error is also an error in production. Therefore, there are merits that high accuracy and easy sensor positioning are possible, and that miniaturization and cost reduction are easy.
[0063]
When the galvano mirrors 202 and 221 are manufactured by a semiconductor process, the timing sensor 203 can be mounted on a substrate integrated with or adjacent to the galvano mirrors 202 and 221, and integrated with the optical deflector, And galvanometer mirror can be easily positioned with high accuracy.
[0064]
The arithmetic circuit 302 may be a microcomputer, a DSP (digital signal processor), a CPLD / FPGA (complex programmable logic device / field programmable gate array), or the like.
[0065]
(Modification of Embodiment 1)
FIG. 4 is a diagram illustrating another example of the arrangement of the optical sensor and the galvanometer mirror in the present embodiment. In FIG. 4A, the reflected light 222 from the galvano mirror 202 is detected by detecting the light 206 branched by the beam splitter 204 out of the reflected light emitted from the light source 201 and reflected by the galvano mirror 202. It shows a state where it is detected that has reached a predetermined displacement angle φ.
[0066]
The position of the timing sensor 203 is on a position 208 that is shifted from the rotation center point 207 by a predetermined angle φ. Although it is necessary to reduce the light amount of the drawing light 205 and to facilitate the beam splitter 204, it is not necessary to provide a separate light source for detection, and there is an advantage of all-scan detection.
[0067]
Further, since the divided light travels in different directions, there is an advantage that the reliability at the time of detection is increased without interfering with each other.
[0068]
In FIG. 4B, a detection light source 211 different from the light source is prepared, and the light beam 212 is emitted from the detection light source 211 to the galvanometer mirror 202 at a different angle from the light beam from the light source. A state in which reflected light is detected by the timing sensor 203 is shown. Reference numeral 213 denotes a rotation center point of the galvanometer mirror 202.
[0069]
By preparing the detection light source 211, there is an advantage that the reduction of the drawing light is eliminated as compared with the case of FIG.
[0070]
FIG. 4C shows a state in which the timing sensor 203 is arranged in the non-drawing region 224 out of the drawing region 223 and the non-drawing region 224 of the two-dimensional scanning system. Incidentally, here, the light beam from the light source 201 is reflected by the galvano mirror 202 and then reflected by the reflection mirror 221 to become drawing light 222. Reference numeral 225 denotes a rotation center point of the galvanometer mirror 202. Although some scan detection is disadvantageous, there is an advantage that a new component is unnecessary.
[0071]
The example shown in FIGS. 4A to 4C is a method in which the scanning light is detected by the optical sensor 203 at a position away from the galvano mirror 202, but the small galvano mirror 202 and the optical sensor 203 are used in a semiconductor process. And may be integrated.
[0072]
Further, the timing sensor is not limited to the optical sensor 203, and a magnetic sensor such as an electrostatic sensor or a coil may be used. However, as described in Japanese Patent No. 2657769 and Japanese Patent No. 30111144 described above, Instead of generating a detection signal over the entire period of vibration of the galvanometer, one that outputs a sharp detection signal when a specific displacement angle is reached is used.
[0073]
2. Embodiment 2
Next, a second embodiment of the present invention will be described with reference to the second embodiment.
[0074]
The second of the present invention is based on the premise that the scanning center position of the deflector has an unknown shift and the relative position and direction of the screen and the deflector cannot be easily changed. This is the case when the screen and deflector are both fixed to the wall surface of the room. In this case, the center position shift X₀The movement of the light spot on the screen including
X = Asin (2πt / T−δ) + X₀
As the three unknown parameters A, δ, X₀Is determined, the movement of the light spot can be completely grasped. This case will be described below as a second embodiment.
[0075]
Hereinafter, this embodiment will be described with reference to the drawings.
[0076]
FIG. 5 is a schematic configuration diagram of the optical deflector unit of the present embodiment. In FIG. 5, the same components as those in FIG.
[0077]
Unlike FIG. 1, two timing sensors 203 and 212 are arranged at the upper end of the screen. At least one of them detects the timing of the reciprocating scanning beam, but the other may detect only the forward or backward timing.
[0078]
FIG. 6 is an explanatory diagram of a method for generating a drive signal for the main scanning galvanometer mirror 202 of FIG.
[0079]
FIG. 6A shows a drive signal synchronization signal, FIG. 6B shows a drive signal applied to the galvano mirror 202 in synchronization with the reference signal of FIG. 6A, and FIG. 6C shows a drive signal of FIG. Based on the displacement waveform of the actually driven galvanometer mirror 202, (d) and (d ′) are output signals of the optical sensors 203 and 212, respectively, and (e) is based on the output signals of (d) and (d ′). The reproduced displacement waveform of the galvanometer mirror 202, (f) shows the start / end timing of drawing based on the displacement waveform of (e), respectively.
[0080]
In FIG. 6C, φ1 and φ2 are displacement angles when the galvanometer mirror 202 is rotated from the drive center point to the installation position of the optical sensors 203 and 212, respectively, ± θc is the maximum displacement angle of the galvanometer mirror 202, Dc is the delay time from the rise of the drive signal (a) to the rise of the displacement waveform (b), and T is the period of the displacement waveform (b). The delay time Dc occurs in the electrical system of the galvano mirror 202 drive system and the optical sensors 203 and 212.
[0081]
When the drive signal A1 shown in FIG. 6B is applied to the galvano mirror 202 in synchronization with the reference signal as shown in FIG. 6A, the galvano mirror 202 corresponds to the drive signal after a delay time Dc. Then, as shown in FIG. 6C, the displacement waveform becomes a sine waveform.
[0082]
Then, after td1 after the drive signal A1 is applied, the reflected light 222 of the vertical scanning mirror 221 enters the optical sensor 203, and the detection signal C1 is output from the optical sensor 203 as shown in FIG. The
[0083]
Furthermore, when the galvano mirror 202 is driven, the reflected light 222 eventually reaches the displacement angle θ, which is the peak point of the sine waveform, and after td2 after the drive signal A1 is applied, the reflected light 222 again becomes the optical sensor 203 again. And the detection signal C2 is output from the optical sensor 203.
[0084]
Then, the galvanometer mirror 202 returns to the displacement angle of 0 degree, is rotated so that the displacement angle is in the negative direction, and after td3 after applying the drive signal, as shown in FIG. The reflected light 222 enters the optical sensor 212, the detection signal C3 is output from the optical sensor 212, and then reaches the displacement angle −θ.
[0085]
Then, after td4 after applying the drive signal, the reflected light 222 is incident again on the optical sensor 212, and the detection signal C4 is output as shown in FIG. 6 (d '), and then returns to the displacement angle of 0 degree.
If the displacement of the galvano mirror is a sine wave
φ (t) = θcsin {2π (t−Dc) / T} + φ₀
Therefore, between the displacement angles φ1 and φ2 of the sensor position and the four detection timings td1 to td4,
φ1 = θcsin {2π (td1−Dc) / T} + φ₀
φ1 = θcsin {2π (td2−Dc) / T} + φ₀
−φ2 = θcsin {2π (td3−Dc) / T} + φ₀
−φ2 = θcsin {2π (td4-Dc) / T} + φ₀
There is a relationship.
[0086]
Subsequently, when the drive signal A2 is applied to the galvanometer mirror 202, a detection signal is output to the measurement circuit 106 as in the above-described series of procedures. As described above, the measurement circuit 106 receives four pulses of the detection signals C1 to C4 with respect to the displacement of one cycle T of the galvanometer mirror 202.
[0087]
Similar to the first embodiment, the delay time Dc is determined from the times td1 and td2 by the following equation (5).
[0088]
Dc = (1/4) (2td1 + 2td2-T) (5)
Alternatively, the delay time Dc may be determined from the times t31 and t42 by the following formula (6).
[0089]
Dc = (1/4) (2td3 + 2td4-3T) (6)
Since Dc is determined in this way, the amplitude θc and the center position φ₀Solves simultaneous linear equations composed of one of the above φ1 and φ2 equations,
θc = (φ1 + φ2) / [sin {(π / T) (td1−td2 + T / 2)} + sin {(π / T) (td3−td4 + T / 2)}] (7)
and
φ₀= [Φ1 · sin {(π / T) (td3−td4 + T / 2)} − φ2 · sin {(π / T) (td1−td2 + T / 2)}] / [sin {(π / T) (td1− td2 + T / 2)} + sin {(π / T) (td3-td4 + T / 2)}] (8)
Is required.
[0090]
As can be seen from (5) and (6), td1-td4 is not independent,
-Td1-td2 + td3 + td4 = T
There is a relationship.
[0091]
Equation (5) for obtaining Dc has T / 2 arbitrary depending on which of td1 and td2 is the forward pulse and which is the backward pulse, but the sensor position is shifted from the scanning center and the interval is narrow. If t is determined to be td1 and td2, it is possible to determine which is the forward path or the return path, and the arbitraryness is lost. The same applies to (6).
[0092]
Expressions (5) and (6) are linear calculations of the measured sensor position passage times td1 to td4 and the scanning period T. In this case, since the vibration waveform is reciprocally symmetrical, Dc can be calculated by the sum of the average value of the two passage times and T / 2. Therefore, a complicated calculation process of solving the nonlinear equation is not required, and the calculation can be performed with a simple arithmetic circuit in a short time. The reason why Dc can be obtained by such simple calculation is that at least one photodetector detects a round trip light beam and uses data at different times at the same position.
[0093]
Thus, since all three unknown parameters have been determined, the displacement angle of the deflector at an arbitrary time is known. Using this result, the start and end timing of modulation applied to the laser beam according to the image signal can be obtained in the same manner as the calculation described in the first embodiment. That is,
tA = (T / 2π) (arcsin (φA−φ₀) / Θc) + Dc) (9)
tB = (T / 2π) (arcsin (φB−φ₀) / Θc) + Dc) (10)
In FIG. 6F, the drawing start position and its timing are indicated by ◯, and the end position and its timing are indicated by ●. It is preferable that the drawing start and end be performed around a region where the speed change of the galvanometer mirror is small.
[0094]
In the present embodiment, the first and second sensor position data φ1 and φ2 and the displacement angle data φA and φB indicating the image display range match the scanning center and the screen reference position 226 (for example, the center position of the screen). It is set as a distance from the reference position on the display screen.
[0095]
FIG. 7 shows the positions of the main scanning deflector 202 and the screen 210. The first and second sensors 203 and 212 are arranged on the screen 210, and the image display range XA <X <XB is defined. . L is the distance from the main scanning deflector to the screen, but in actuality, a sub-scanning galvanometer mirror is disposed therebetween.
[0096]
If the distance from the screen center of the first (second) optical sensor is X1 (X2), φ1 (φ2) is
φ1 = arctan (X1 / L)
φ2 = arctan (X2 / L)
It is determined as Similarly, the distance XA (XB) between the left end (right end) of the image display range and the screen center is
φA = arctan (XA / L)
φB = arctan (XB / L)
It is determined as
[0097]
Even if the scanning center is deviated from the reference position of the screen, according to the present embodiment, as described above, the offset value of the scanning center is determined, and the modulation start and end timings are set based on the offset value. Therefore, the image positions XA and XB on the screen do not shift.
[0098]
By the way, the above equation (7) includes the parameters φ1 and φ2 representing the position of the detector in the sum form φ1 + φ2. This represents that the amplitude is determined by the relative position of the two detectors. That is, if the distance between the detectors is fixed, the delay time Dc and the amplitude θc are determined independently of each other regardless of the position on the screen. When the detectors are displaced on the screen while maintaining a mutual distance, φ₀Will shift the image to the left or right on the screen, which can be easily adjusted to bring the detector to the correct position. Therefore, even in a situation where it is difficult to move the positional relationship between the deflecting device and the screen, it is possible to always project an image at a predetermined position on the screen.
[0099]
Even if the detector is not on the screen but in the deflecting device, the position of the image range on the screen can be adjusted similarly by maintaining the distance between the detectors and adjusting the position.
[0100]
As described above, according to the present embodiment, the arrangement of the photosensors with respect to the drive center point only needs to be determined by a relative distance. Since there are no severe restrictions, the assembly cost of the optical deflector unit can be reduced.
[0101]
The control circuit in this embodiment is the same as the control circuit in the first embodiment shown in FIG. Hereinafter, a specific operation of the control device 107 will be described.
[0102]
The scanning cycle data T, the first and second sensor position data φ1, φ2, and the displacement angle data φA, φB indicating the image display range are stored in the memory in advance.
[0103]
First, after the reference signal rises, the control device confirms that four pieces of scanning beam passage time data from the measurement circuit have been sent continuously, and stores this in the memory. If the second sensor detects only one of the reciprocating scans, the passage time data is three. Even when four time data are sent, the control circuit may check and store only the first three.
[0104]
Next, these data are sent to the arithmetic circuit together with the scanning cycle data T and the sensor position data φ1 and φ2, and the arithmetic circuit calculates Dc by the equation (5) or (6), and the equations (7) and (8). Θc and φ₀And return the result to the control circuit. The control circuit stores this result in the memory.
[0105]
Next, the control circuit determines the displacement angle data φA, φB, the period data T, the previously calculated delay time data Dc and amplitude data θc, and the center position offset data φ determined from the image display range and stored in the memory.₀Is sent to the arithmetic circuit, tA and tB are calculated by equations (9) and (10), and the results are stored in the memory.
[0106]
In the subsequent scanning, the light source modulation signal is controlled so as to start modulation according to the image at the timing when the tA time elapses and to end the modulation at the timing when the tB time elapses. That is, the controller generates a galvanometer mirror drive signal in synchronization with the reference signal, sends it to the galvanometer drive circuit, generates a light source modulation start signal at a time delayed by tA, sends it to the light source modulation circuit, and delays by tB At the same time, a light source modulation end signal is generated and sent to the light source modulation circuit. Further, during the time tA and tB, image data is read from the image memory, modulated to be a light source modulation signal, and sent to the light source modulation circuit.
[0107]
Note that if the two sensor position data are not given individually, but only the relative position (relative displacement angle) φ1 + φ2 data is given, the offset data φ₀Assuming that 0 is 0, equations (9) and (10) are calculated. As a result, if the image display range is deviated from the specified position on the screen,₀Can be changed with a dial, etc.₀Using the value of, the equations (9) and (10) are recalculated to adjust to the desired position.
[0108]
The calculation using the above mathematical formulas (5) to (10) may be performed every time an electric signal is input every cycle, or may be performed every several cycles, as described in the first embodiment. Incidentally, it is preferable to provide the control circuit 107 with a signal processing system capable of performing the above-described calculation within one cycle because control can be performed more quickly.
[0109]
The same light source, galvanometer mirror, and timing sensor as those in the first embodiment can be used. As control means, microcomputer, DSP (digital signal processor), CPLD, FPGA (complex programmable logic device, field programmable gate array)
It is the same that can be used.
When the timing sensors 203 and 212 are optical sensors or the like manufactured by a semiconductor process or are electrostatic sensors, it is possible to arrange optimal sensors at the respective displacement points, and also produce sensor placement errors. Therefore, there are merits that high accuracy and easy sensor positioning are possible, and that miniaturization and cost reduction are easy.
[0110]
When the galvano mirrors 202 and 221 are manufactured by a semiconductor process, the timing sensors 203 and 212 can be mounted on a substrate integral with or adjacent to the galvano mirror, and integrated with the optical deflector, Highly accurate positioning with the galvanometer mirror can be easily realized.
[0111]
(Modification of Embodiment 2)
Similar to the first embodiment, several variations are conceivable as the detection method.
[0112]
First, as shown in FIG. 8, it is conceivable to divide the reflected light from the galvanometer mirror with a beam splitter and detect it with a divided light beam detector or the like.
[0113]
According to this method, since the divided light travels in different directions, there is an advantage that the reliability at the time of detection is increased without interfering with each other.
[0114]
As shown in FIG. 9, in addition to the main light source 201 for image display, a detection light source 211 that emits another beam for detection is provided, and the galvanometer mirror 202 has an angle different from that emitted from the light source 201. A method may be considered in which light is irradiated and detected by the timing sensor 203 (there may be two, but only one case will be described here). The main light source beam is not detected.
[0115]
According to this method, the sensor 203 can be placed on a screen or in a device that is out of the display area, and it is possible to avoid obstructing image viewing. Also, when detecting the main light source, the image may be modulated and the intensity of the sensor may happen to be weakened or become extinguished. That can be solved.
[0116]
In addition, detection light is emitted and detected only during a part of the time during which the main light source is sub-scanned, that is, during the period when the main scan is on the sensor, and the other light is extinguished for detection The power consumption of the light source can be reduced. Furthermore, even when the sensitivity of the sensor is poor and the intensity of the light from the main light source is insufficient, there is an advantage that light having sufficient luminance, intensity, and spot diameter can be emitted from the detection light source.
[0117]
When the detection light source 211 is provided as shown in FIG. 9, the amount of light applied to the projection surface is not reduced as compared with the case shown in FIG. 8, so that the luminance of drawing can be relatively increased. Become. In addition, it becomes easy to optimize the size of the detection beam diameter and the arrangement of the optical sensors, and it is possible to acquire information indicating the displacement angle with high accuracy.
[0118]
FIG. 12 shows still another modification. Sub-scanning is also performed on the non-drawing area, timing sensors 203 and 212 are arranged there, and light is emitted from the light source 201 when the reflected light from the galvano mirror 202 enters the timing sensors 203 and 212. Since it is not necessary to provide a beam splitter, a light source for detection, or the like, it is possible to avoid the problem of luminance reduction and interference.
[0119]
The surface 223 on which the timing sensors 203 and 212 shown in FIG. 12 are arranged does not necessarily have to be on the projection surface 210. An image forming apparatus in which the projection surface 210 is not selected can be configured by bringing the timing sensor arrangement surface 223 into the projection device.
[0120]
【Example】
Hereinafter, the present invention will be described by way of examples. The following example is a configuration in which two optical sensors are arranged, but may be one.
[0121]
Example 1
FIG. 13 is a schematic configuration diagram of the optical deflection apparatus according to the first embodiment of the present invention, which is a one-dimensional scanning optical deflection apparatus. A light source 201, a galvano mirror 202 for scanning light from the light source 201, optical sensors 203 and 212 such as photoelectric conversion elements that output an electrical signal when reflected light 222 of the galvano mirror 202 is incident; Based on the output of 212, information indicating the displacement angle of the galvano mirror 202 is acquired, and a synchronization signal synchronized with the drive signal applied to the galvano mirror 202 and timing signals indicating the drawing start timing and drawing end timing of the light source 201 are generated Acquisition means 226 to perform. The acquisition unit 226 is a combination of the measurement circuit 106, the control circuit 107, the drive circuit 108, and the modulation circuit 109 shown in FIG.
The light source 201 uses a semiconductor laser having an optical output of about 5 mW, and directly modulates by pulse width modulation. The galvanometer mirror 202 is driven by a sinusoidal drive signal having a period of about 10 kHz.
[0122]
When a drive signal is applied to the deflector 202, four pulses of the total detection signal are output for one cycle of the drive signal, and the detection signals from the timing sensors 203 and 212, the timing sensors 203 and 212, and the galvanometer mirror are formed. Information indicating the displacement angle of the galvanometer mirror 202 is acquired from the angle.
[0123]
As described above, by calculating predetermined data using at least three of the four pulses, information indicating the displacement angle of the galvanometer mirror 202 can be completely acquired.
[0124]
(Example 2)
In a two-dimensional image forming apparatus similar to that shown in FIG. 5, the galvanometer mirrors 102 and 121 were replaced with an optical deflector manufactured integrally using a semiconductor process as described in Japanese Patent Registration No. 2983088. The optical deflector of this embodiment is a biaxial deflector in which resonant galvanometer mirrors are nested. The resonance frequency is 8 kHz. The other parts are the same as in FIG.
[0125]
As described in the second embodiment, it is possible to completely acquire information indicating the displacement angle of the galvanometer mirror 202 by calculating predetermined data using at least three of the four pulses obtained from the sensor. it can.
[0126]
By measuring the reciprocating passage time as in the present embodiment, the vibration of the deflector can be predicted without increasing the number of detectors, and as a result, the image modulation timing can be determined with high accuracy.
[0127]
Moreover, since the delay time of the deflector can be easily calculated, high-speed processing is possible. Furthermore, even when two detectors are provided, only the relative position needs to be fixed, so that positional accuracy is not required, and a screen and other installations are easy.
[0128]
(Example 3)
The present embodiment is an example of a driving method in which a fluctuation in resonance frequency is detected from a phase shift and the driving frequency is changed based thereon.
[0129]
FIG. 11A is a diagram showing the relationship between the frequency of the drive signal and the maximum displacement angle in the resonant galvanometer mirror. FIG. 6B is a diagram showing the relationship between the frequency and phase of the drive signal. The horizontal axis of (a) shows the frequency of the drive signal, and the vertical axis shows the maximum displacement angle. The horizontal axis of (b) shows the driving frequency, and the vertical axis shows the phase shift.
[0130]
Here, two data (characteristics A and B) are shown by changing the ambient temperature around the optical deflector unit.
[0131]
When the galvanometer mirror is driven at the resonance frequency, the resonance frequency changes significantly when the environmental temperature changes. As a specific example, when the temperature changes by 1 ° C., the resonance frequency may change by several tens of Hz. Then, the drive signal frequency-maximum displacement angle characteristic shown in FIG.
[0132]
For example, if the characteristic A is changed to the characteristic B (this corresponds to an increase in the resonance frequency), the displacement angle decreases if the driving is continued at the same frequency.
[0133]
However, as shown in the characteristic A of FIG. 11A, in the resonance characteristic that is substantially symmetric about the resonance point (●), if only the amplitude of the waveform is detected when the frequency changes, the resonance frequency is It cannot be detected to which side of the height has changed.
[0134]
Therefore, as shown in FIG. 11B, it can be considered to detect which side the frequency has changed by detecting a change in the phase information of the drive signal. That is, as shown by the characteristics A and B in FIGS. 11A and 11B, the phase information increases when the resonance frequency is changed to a higher one. On the other hand, when the resonance frequency changes to a lower side, the phase information becomes smaller.
[0135]
The delay time data Dc is related to the phase shift ω by the following formula:
ω = 2πf / (Dc−nT) × 360 (n: integer, 0 ≦ ω <360 °)
In this example, the scanning timing is detected by the method described in the first or second embodiment, the delay time Dc is calculated, the phase shift is obtained by the above equation, and the deflector is driven using the method described above. Adjustment is made so that the frequency matches the resonant frequency. If the phase shift ω is negative, the drive frequency is increased, and if the phase shift ω is positive, the drive frequency is decreased to control the phase shift ω to be always zero, thereby placing the image forming apparatus. Even if there is a change in the ambient temperature, a desired drive signal is applied to the galvanometer mirror.
[0136]
The phase signal such as the delay time Dc can be used as an input of the phase locked loop in frequency tracking control in driving the galvano mirror.
[0137]
According to this embodiment, even if the environmental temperature where the image display device is placed changes, the driving frequency can be made to follow the resonance point without changing the frequency as in wobbling, so that the image is disturbed. In addition, the resonance frequency can be detected in real time.
[0138]
Example 4
In this embodiment, the drive signals A1 and A2 of the galvano mirror 202 are driven with a sawtooth wave having a period of about 60 Hz.
[0139]
FIG. 14 is an explanatory diagram of a method of generating the drive signals A1 and A2 by the galvanometer mirror 202 of the generation unit 226. First, a method for calculating the maximum displacement angle θc based on the detection signals C1 to C5 of the optical sensors 203 and 212 will be described.
[0140]
As shown in FIG. 14B, points A to A 'are taken on the drive signal A1, the phase difference between the points A and C is TA, the phase difference between the points B and F is TC, and the point F The phase difference between the point H and the point H is TB, and the phase difference between the point H and the point A ′ is TD. Note that point A, point B, point F, point H, and point A ′ are intersections with displacement angles φ1 and φ2.
[0141]
Further, as shown in FIG. 14B, an auxiliary line parallel to the line connecting the point D and the point H is drawn so as to pass through the point B, and the intersection of the auxiliary line and the line connecting the drive center point is defined as a point H ′. Then,
△ ABH’∽ △ BDF
And the length between CH 'is TB.
[0142]
Here, in calculating the maximum displacement angle θc, the lengths between DE, BC, and IJ are obtained.
[0143]
Since the length between DE is similar between ΔABH ′ and ΔBDF, the ratio between the distances between AH ′ and BF is used as a reference, based on the length between BCs.
DE = BC × tC / (tA + tB)
Given by.
[0144]
Since the length between IJ is similar to ΔABH ′ and ΔA′JH, the ratio between the distances between AH and A′H is based on the length between BCs.
IJ = BC × tD / (tA + tB)
Given by.
[0145]
From the above equation for DE and IJ, the sum of lengths between DE, BC, and IJ is

Given by.
[0146]
Here, since the length between BC is φ1, the maximum displacement angle θc is
θc = 2 × (TA + TB) / T × φ1
It becomes.
[0147]
Next, the relationship between an arbitrary position on J′D and the passing time of the reflected light 222 at that position will be described. First, the length of AL is equal to the length obtained by subtracting [DE + BM] (the length above the horizontal axis) from [DE + BC + IJ] and further subtracting [IJ], and the length of [DE + BM] is [DE + BC + IJ]. ] From the above DE and IJ formulas

Holds.
[0148]
The slope of the line segment AK is BC / TA, where t1 is the time for the reflected light 222 to pass through the point A, and t0 is the time for the reflected light 222 to pass through the point K. [AL = BC / TA × From (t0-t1)]
t0 = tA × (tA + tB + tC−tD) / 2 / (tA + tB) + t1
It is.
[0149]
From the above formula, the displacement angle φα at an arbitrary position on J′D is obtained by using tα as the transit time of the reflected light 222 at that position.

+ TB) + t1}
It is expressed.
[0150]
According to the present embodiment, it is possible to acquire information indicating the displacement angle of the galvanometer mirror driven by the sawtooth wave. Actually, when a galvano mirror is driven with a sawtooth wave, it does not become an ideal sawtooth wave. Absent.
[0151]
(Example 5)
FIG. 8 is a schematic configuration diagram of an optical deflector according to a fifth embodiment of the present invention. In this embodiment, the optical sensors 203 and 212 are installed not in the screen but in the deflecting device.
[0152]
Specifically, as shown in FIG. 8, a beam splitter 204 is provided between the galvano mirror 202 and the vertical scanning mirror 221, and the optical sensors 203 and 212 are placed in the optical path of the detection scanning light 206 whose path has been changed by this. It is arranged. In addition, the projection plane 210 is irradiated with the drawing scanning light 205 whose path is not changed by the beam splitter 204.
[0153]
When the optical sensors 203 and 212 are arranged as shown in FIG. 8, there is a merit that full scanning detection can be performed. That is, compared with the case shown in FIG. 5, the light from the light source 201 enters the photosensors 203 and 212 every time the horizontal scanning is performed regardless of the vertical scanning of the projection surface 210. The light source 201 and the galvanometer mirror 202 can be controlled with high accuracy.
[0154]
(Example 6)
FIG. 9 is a schematic configuration diagram of an optical deflector according to a sixth embodiment of the present invention. In this embodiment, in addition to the light source 201, a separate detection light source 211 is provided outside the light path of the light from the light source 201 in order to detect the displacement waveform of the galvanometer mirror 202 by the optical sensors 203 and 212.
[0155]
The detection light source 11 uses different wavelengths in order to avoid interference with the scanning light. The incident angle from the detection light source 11 to the galvanometer mirror 202 is different from the incident angle from the light source 201 having the modulation means. The optical sensors 203 and 211 are arranged at positions where the scanning light from the detection light source can be detected. Other configurations are the same as those in FIG.
[0156]
When the detection light source 211 is provided as shown in FIG. 9, the amount of light applied to the projection surface is not reduced as compared with the case shown in FIG. 8, so that the luminance of drawing can be relatively increased. Become. In addition, it becomes easy to optimize the size of the detection beam system and the arrangement of the optical sensors, and it is possible to acquire information indicating the displacement angle with high accuracy.
[0157]
As described above, in the first to sixth embodiments of the present invention, the case where the optical sensors 203 and 212 are used as the timing sensor for detecting the displacement angle of the light reflecting surface of the galvano mirror 202 has been described as an example. However, it is not limited to this, and instead of this, a magnetic sensor such as an electrostatic sensor or a coil built in the galvano mirror 202 may be used. One of the optical sensors 203 and 212 may be an electrostatic sensor and the other may be a magnetic sensor.
[0158]
(Example 7)
FIG. 12 is a schematic configuration diagram of an image forming apparatus including any one of the optical deflector units described in the first to sixth embodiments. In FIG. 12, the same parts as those in FIG. 13 are denoted by the same reference numerals.
[0159]
The galvanometer mirror 202 for horizontal scanning applies a resonance type sine wave drive signal of about 23 kHz. The light emitted from the galvanometer mirror 202 enters the timing sensors 203 and 212.
[0160]
The vertical scanning mirror (galvanomirror) 221 applies a sawtooth drive signal having a blanking period of 10% at about 60 Hz. The light emitted from the galvanometer mirror 221 is incident on the timing sensors 203 'and 212'.
[0161]
The light source 201 uses a semiconductor laser with an optical output of about 30 mW, and directly modulates by pulse width modulation. Information indicating the displacement angle in the horizontal direction and the vertical direction is obtained by using the method described in the first and second embodiments and the fifth embodiment.
[0162]
Information indicating the displacement angle was obtained for each scanning direction, and drive stabilization control and modulation start / end timing generation were performed. According to the present embodiment, it is possible to acquire information indicating respective displacement angles in different scanning directions and scanning speeds, and to display a stable and high-quality image.
[0163]
Furthermore, in this embodiment, the image display device has been described as an example. However, the optical deflector unit can be provided in an image drawing device such as a laser printer, a scanning reader such as a laser microscope, and the like. The polarization unit can be used as a single light deflecting device.
[0164]
In the above embodiments, the image display device has been described as an example. However, the optical deflector unit can be provided in an image drawing device such as a laser printer, a scanning reader such as a laser microscope, and the like. The unit can be used as a single light deflecting device.
[0165]
【The invention's effect】
According to the present invention, the relationship between the drive signal and the actual movement of the deflector of the image display device using the optical deflector that performs non-linear scanning such as a sine wave, and the drive signal and the actual screen. When the relationship with the optical beam scanning of the sensor deviates from the predetermined state for some reason, the number of detectors can be reduced compared to the conventional method of automatically detecting the movement of the deflector. The calculation for determining the undetermined parameter is also easy and fast.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an optical deflecting device of the present invention and an image forming apparatus using the same.
FIG. 2 is an explanatory diagram of various signals generated by each unit in FIG. 1;
FIG. 3 is a block diagram illustrating a configuration of a control circuit in FIG. 1;
4 is a modification of the image forming apparatus in FIG.
FIG. 5 is a schematic configuration diagram of another optical deflecting device of the present invention and an image forming apparatus using the same.
6 is an explanatory diagram of various signals generated by each unit in FIG. 5;
FIG. 7 is an explanatory diagram of a positional relationship between a screen and a galvanometer mirror.
8 is a modification of the image forming apparatus in FIG.
9 is a modification of the image forming apparatus in FIG.
FIG. 10 is an explanatory diagram showing the relationship of vibration with respect to the drive signal of the optical deflector.
FIG. 11 is a diagram showing the relationship between the drive frequency, maximum displacement angle, and phase of a resonant galvanometer mirror.
12 is a modification of the image forming apparatus in FIG.
FIG. 13 shows an optical deflection apparatus according to the first embodiment of the present invention.
FIG. 14 is an explanatory diagram showing vibration of an optical deflector according to a fourth embodiment of the present invention.
[Explanation of symbols]
201 Light source
202 Galvano mirror
203,212 Optical sensor
204 Beam splitter
205 Scanning light for drawing
206 Scanning light for detection
207 Line connecting drive center points of galvanometer mirror
210 screens
211 Laser light source for detection
221 Vertical scanning mirror
222 Reflected light
223 drawing area
224 Non-drawing area
226 generating means

Claims (15)

A light source that emits a light beam;
Modulation means for modulating the light beam emission intensity of the light source;
Modulation signal generation means for outputting a modulation signal to the modulation means;
An optical deflector for deflecting the light beam emitted from the light source;
Driving means for driving the light deflector to scan the deflected light beam;
Drive signal generating means for outputting a drive signal of a predetermined period to the drive means;
An optical deflecting device having measuring means for measuring a first time at which a specific position on a scanning line of a scanned light beam passes on a forward path and a second time at which the scanned light beam passes on a return path, respectively.
The light deflection apparatus further comprises:
Delay time data calculating means for calculating delay time data corresponding to the delay time of the displacement start timing in the displacement waveform of the optical deflector with respect to the start timing of the drive signal of the optical deflector from the first and second times; ,
Timing data calculating means for calculating timing data corresponding to the modulation start time of the light beam from the first and second times and the delay time data;
An optical deflecting device, wherein the modulation signal generating means outputs a modulation signal to the modulation means based on the calculated timing data. A light source that emits a light beam;
Modulation means for modulating the light beam emission intensity of the light source;
Modulation signal generation means for outputting a modulation signal to the modulation means;
An optical deflector for deflecting the light beam emitted from the light source;
Driving means for driving the light deflector to scan the deflected light beam;
Drive signal generating means for outputting a drive signal of a predetermined period to the drive means;
A first time at which it passes through a first specific position on the scanning line of the scanned light beam in the forward path and a second time at which it passes through the return path;
A light deflection apparatus comprising: a measuring unit that measures a third time at which the second specific position on the scanning line of the light beam passes through the forward path or the return path;
The light deflection apparatus further comprises:
Delay time data calculating means for calculating delay time data corresponding to the delay time of the displacement start timing in the displacement waveform of the optical deflector with respect to the start timing of the drive signal of the optical deflector from the first and second times; ,
Timing data calculating means for calculating timing data corresponding to the modulation start time of the light beam from the first to third times and the delay time data;
An optical deflecting device, wherein the modulation signal generating means outputs a modulation signal to the modulation means based on the calculated timing data.   The optical deflection apparatus according to claim 1 or 2, wherein the delay time data calculating means calculates delay time data by linear calculation of the first and second times and a scanning cycle.   4. The optical deflecting device according to claim 3, wherein the reciprocating scanning of the optical deflector is a symmetric vibration, and the delay time data is calculated by linear calculation of an average value of the first and second times and a scanning cycle.   The reciprocating scan of the optical deflector is sawtooth wave oscillation, and the delay time data is calculated by linear calculation of the weighted average value of the reciprocating scanning speeds at the first and second times and the scanning cycle. The light deflection apparatus according to claim 1 or 2.   The optical deflection apparatus according to claim 1, wherein the drive signal generating unit outputs a drive signal to the drive unit based on the calculated delay time data.   The measuring means measures the passage time of a specific position on the scanning line of one light beam obtained by separating the light beam deflected by the optical deflector by the beam splitter, so that the specific position on the scanning line of the other light beam is measured. The light deflection apparatus according to claim 1 or 2, wherein the passage time is indirectly measured.   The measurement means measures the passage time of a specific position on the scanning line of the light beam, and the passage time of the specific position on the scanning line of another light beam incident on the optical deflector at an angle different from the light beam. The light deflection apparatus according to claim 1 or 2, wherein the measurement is performed indirectly. Said timing data calculation means, the calculation of the timing data, the optical deflecting device of claim 1 using a modulation starting position before Kitoku position and the light beam as a parameter. The light deflection device further comprises:
Amplitude data calculating means for calculating amplitude data corresponding to the maximum deflection angle of the optical deflector from the first and second times and the calculated delay time data;
3. The drive signal generation unit according to claim 1, wherein the drive signal generation unit outputs a drive signal to the drive unit by increasing or decreasing a cycle of the drive signal based on the calculated delay time data and the amplitude data. Optical deflection device. Said timing data calculation means, the calculation of the timing data, relative to the first and the relative position of the second specific position, the light beam modulating start position reference position on the projection plane of the location of the scanline for measuring the transit time The light deflection apparatus according to claim 2, wherein the position is used as a parameter. The timing data calculating means includes t d1 as the first time, td2 as the second time, T as the scanning period, delay time as Dc = (1/4) (2td1 + 2td2-T), and maximum displacement angle as θc = φ. / Sin {(π / T) (td1−td2 + T / 2)}, where the modulation start position of the light beam is φA, the modulation start time t A is
tA = (T / 2π) (arcsin (φA / θc) + Dc) ,
Optical deflecting device of claim 1, out by Risan on. A method of driving an optical deflector that scans a light beam from a light source,
Measuring each of a first time at which a specific position on the scanning line of the scanned light beam passes on the forward path and a second time at which the scanned light beam passes on the return path;
Calculating a delay time of the displacement start timing in the displacement waveform of the optical deflector with respect to the start timing of the drive signal of the optical deflector from the first and second times;
Calculating timing data corresponding to the modulation start time of the light beam from the first and second times and the delay time;
Modulating the light beam from the light source based on the timing data, and driving the optical deflector. A method of driving an optical deflector that scans a light beam from a light source,
A first time at which the scanned light beam passes through the first specific position on the scanning line in the forward path, a second time at which the light beam passes through the backward path, and a second specific position on the scanning line of the light beam as the forward path or Measuring a third time passing on the return path;
Calculating a delay time of the displacement start timing in the displacement waveform of the optical deflector with respect to the start timing of the drive signal of the optical deflector from the first and second times;
Calculating timing data corresponding to the modulation start time of the light beam from the first to third times and the delay time;
Modulating the light beam from the light source based on the timing data, and driving the optical deflector. A light source that emits a light beam;
Modulation means for modulating the light beam emission intensity of the light source;
Modulation signal generation means for outputting a modulation signal to the modulation means;
An optical deflector for deflecting the light beam emitted from the light source;
Driving means for driving the light deflector to scan the deflected light beam;
Drive signal generating means for outputting a drive signal of a predetermined period to the drive means;
A light beam scanned by the light deflecting device, having measuring means for measuring a first time at which a specific position on the scanning line of the scanned light beam passes on the forward path and a second time at which the scanned light beam passes on the backward path; A method for determining a modulation start time,
Measuring each of a first time at which a specific position on the scanning line of the scanned light beam passes on the forward path and a second time at which the scanned light beam passes on the return path;
Calculating a delay time of the displacement start timing in the displacement waveform of the optical deflector with respect to the start timing of the drive signal of the optical deflector from the first and second times;
Calculating a light beam modulation start time from the first and second times and the delay time;
A method for determining a modulation start time of a light beam, comprising:

Images