JPS641858B2 - - Google Patents
Info
- Publication number
- JPS641858B2 JPS641858B2 JP13699679A JP13699679A JPS641858B2 JP S641858 B2 JPS641858 B2 JP S641858B2 JP 13699679 A JP13699679 A JP 13699679A JP 13699679 A JP13699679 A JP 13699679A JP S641858 B2 JPS641858 B2 JP S641858B2
- Authority
- JP
- Japan
- Prior art keywords
- light
- reflected
- error signal
- objective lens
- prism
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000003287 optical effect Effects 0.000 claims description 26
- 238000001514 detection method Methods 0.000 claims description 17
- 238000010586 diagram Methods 0.000 description 8
- 238000000034 method Methods 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 230000005236 sound signal Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/0908—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only
Landscapes
- Optical Head (AREA)
- Automatic Focus Adjustment (AREA)
- Optical Recording Or Reproduction (AREA)
Description
【発明の詳細な説明】
本発明は、例えば記録媒体上に螺旋或いは同心
円状に記録された情報トラツクに対物レンズを経
て読み取り光スポツトを集束して情報を読み取る
装置において対物レンズの記録媒体に対する焦点
はずれおよび光スポツトの情報トラツクに対する
位置のずれを検出する光学的情報読取装置に関す
るものである。DETAILED DESCRIPTION OF THE INVENTION The present invention provides an apparatus for reading information by focusing a reading light spot onto an information track recorded spirally or concentrically on a recording medium through an objective lens. The present invention relates to an optical information reading device that detects deviation and positional deviation of a light spot with respect to an information track.
上述した情報読取装置は従来より既知であり、
情報トラツクを有する記録媒体には、例えばビデ
オデイスクと呼ばれているものがある。このビデ
オデイスクには情報トラツクに符号化されたビデ
オ信号や音声信号が、光学的透過特性、反射特
性、位相特性などの光学的情報として記録されて
いる。ビデオデイスクに記録された情報は、これ
を高速で回転させながらレーザ光源から放射され
るレーザ光を対物レンズに経て情報トラツク上に
集束させ、情報トラツクによつて変調された透過
光または反射光を検出して読み取つている。この
ような記録媒体の特長の一つは、情報の記録密度
が非常に高いことであり、そのため各情報トラツ
クの幅が極めて狭いと共に、順次の情報トラツク
間の間隔も非常に狭くなつている。このように幅
もピツチも狭い情報トラツクから元の情報を正確
に読み取るためには、対物レンズをビデオデイス
ク面に対して常に合焦状態となるようにして、デ
イスク面上での光スポツトの径を常に最小とする
必要があると共に光スポツトを情報トラツク上に
位置させる必要がある。このためかかる光学的読
取装置においては、対物レンズのデイスク面に対
する焦点はずれを検出し、この焦点はずれ信号に
基いて対物レンズをその光軸方向に変位させるフ
オーカツシング制御が行なわれていると共に情報
トラツクに対する光スポツトの位置ずれを検出
し、このトラツキング誤差信号に基づいて光スポ
ツトを情報トラツクと直交する方向に変位させる
トラツキング制御が行なわれている。 The information reading device described above is conventionally known,
For example, there is a recording medium having an information track called a video disk. On this video disk, video signals and audio signals encoded into information tracks are recorded as optical information such as optical transmission characteristics, reflection characteristics, and phase characteristics. Information recorded on a video disk is recorded by rotating the video disk at high speed and focusing laser light emitted from a laser light source onto an information track through an objective lens, and transmitting or reflecting light modulated by the information track. It is detected and read. One of the features of such recording media is that the information recording density is very high, so that the width of each information track is very narrow and the spacing between successive information tracks is also very narrow. In order to accurately read the original information from such a narrow information track, it is necessary to keep the objective lens always in focus on the video disk surface and to adjust the diameter of the light spot on the disk surface. It is necessary to always minimize the light spot, and it is necessary to position the light spot on the information track. For this reason, in such optical reading devices, focusing control is performed to detect the defocus of the objective lens with respect to the disk surface, and to displace the objective lens in the direction of its optical axis based on this defocus signal. Tracking control is performed by detecting the positional deviation of the optical spot with respect to the track and displacing the optical spot in a direction perpendicular to the information track based on this tracking error signal.
第１図は従来の光学的読取装置における焦点検
出装置の一例を示す線図である。レーザ光源１か
ら放射された光（紙面内に直線偏光している）は
コリメータレンズ２によつて平行光とされ、偏光
膜を有する偏光プリズム３、1/4波長板４および
対物レンズ５を経て情報トラツクを含むデイスク
６上に集束される。この光束は凹凸のピツト形状
を持つ情報トラツクにより反射され、対物レンズ
５および1/4波長板４を経て偏光プリズム３に入
射する。偏光プリズム３に入射する反射光は、1/
４波長板４の作用により紙面に対し垂直方向に偏
光されているから、この光は偏光プリズム３で反
射される。この偏光プリズム３で反射された光束
を集光レンズ７および円柱レンズ８により集束さ
せる。ここで円柱レンズ８は一軸方向にのみ集束
作用を持つから、集光レンズ７および円柱レンズ
８による集束ビームの形状は、デイスク６の位置
が上下にずれると、情報トラツクに正しく集束さ
れた状態（合焦位置）を境として直交した方向に
変形する。従来は、この形状変化を例えば四分割
した光検出器（図示せず）により検出して焦点誤
差信号を得、この信号によりフオーカツシング制
御を行なつている。 FIG. 1 is a diagram showing an example of a focus detection device in a conventional optical reading device. Light emitted from a laser light source 1 (linearly polarized in the plane of the paper) is made into parallel light by a collimator lens 2, and then passes through a polarizing prism 3 having a polarizing film, a 1/4 wavelength plate 4, and an objective lens 5. It is focused onto a disk 6 containing information tracks. This light beam is reflected by an information track having an uneven pit shape, passes through an objective lens 5 and a quarter-wave plate 4, and then enters a polarizing prism 3. The reflected light incident on the polarizing prism 3 is 1/
Since the light is polarized in a direction perpendicular to the plane of the paper due to the action of the four-wavelength plate 4, this light is reflected by the polarizing prism 3. The light beam reflected by the polarizing prism 3 is focused by a condenser lens 7 and a cylindrical lens 8. Here, since the cylindrical lens 8 has a focusing effect only in one axis direction, the shape of the focused beam by the condensing lens 7 and the cylindrical lens 8 will change to a state in which the beam is correctly focused on the information track ( deforms in a direction perpendicular to the focal point). Conventionally, this shape change is detected by, for example, a quarter-divided photodetector (not shown) to obtain a focus error signal, and focusing control is performed using this signal.
しかし、上述した従来の焦点検出位置において
は、偏光プリズム３を反射した後に焦点を結ばせ
るための光路長を必要とするため、光学系が大形
になる欠点がある。また焦点誤差信号を得る光検
出器は、光軸方向とこれと直交する平面内での方
向との二軸方向に正確に配置する必要があるた
め、その位置調整が難しい欠点がある。更に、集
光ビームの形状変化による誤差信号が得られる領
域が狭いため、合焦状態から離れ過ぎると信号が
得られない欠点がある。 However, the above-described conventional focus detection position requires an optical path length for focusing after reflection from the polarizing prism 3, which has the disadvantage that the optical system becomes large. Furthermore, since the photodetector that obtains the focus error signal needs to be accurately placed in two axes: the optical axis direction and the plane orthogonal to the optical axis direction, it is difficult to adjust its position. Furthermore, since the area in which an error signal can be obtained due to changes in the shape of the focused beam is narrow, there is a drawback that no signal can be obtained if the beam is too far away from the focused state.
このような欠点を除去し、光学系を小形に構成
できると共に、焦点誤差信号を得る光学検出器の
配置が容易で、しかも常に正確に焦点状態を検出
できる装置を本願人は既に提案している。 The applicant has already proposed a device that eliminates these drawbacks, allows a compact optical system, allows easy placement of an optical detector for obtaining a focus error signal, and allows accurate detection of the focus state at all times. .
第２図は本願人が先に提案した焦点検出装置の
一例の要部の構成を示す線図である。本例の装置
において、デイスク６に反射させる迄は第１図に
示す装置と同じ構成なので、第１図に示す符号と
同一符号は同一光学部材を表わす。偏光プリズム
３で反射した平行光束を検出プリズム１０に入射
し、その反射面１１により反射される光束を検出
器１２で受光する。反射面１１は、合焦状態での
入射光線（平行光束）に対してほぼ臨界角となる
ように設定する。このようにすれば、合焦状態で
は偏光プリズム３で反射された全光線は反射面１
１で全反射され（実際には反射面の状態が完全で
はないので図示ｎ方向に幾分の光が透過する）、
デイスク６が合焦状態からａ方向にずれると偏光
プリズム３で反射された光束は反射面１１に対し
て最大ai1〜ai2で示す傾き成分を持つ光線束とな
る。またデイスク６が合焦状態からｂ方向にずれ
ると、反射面１１の入射光線はbi1〜bi2で示す傾
き成分を持つ光線束となる。すなわち、デイスク
６が合焦状態からずれると、反射面１１への入射
光線は光軸上の中心光線（一点鎖線）を除いて臨
界角の前後で連続的に変化する。したがつて、デ
イスク６がａおよびｂ方向に変位して合焦状態か
らはずれると、反射面１１での反射強度が第３図
に示すように臨界角近傍では僅かな入射角の変化
で急激に変化するから、中心光線を含む紙面に対
し垂直な面を境として明暗の状態がそれぞれ逆に
なる。これに対し、合焦状態では、一様に全反射
されるから、このような明暗は現われない。光検
出器１２は、このような反射面１１からの反射光
の光量分布を検出するもので、第２図中に平面図
をも示すように、中心光線（光軸）を境に二分割
した二つの受光領域１２Ａ，１２Ｂをもつて構成
する。なお、第３図は検出プリズム１０の屈折率
が1.50で、Ｐ偏光およびＳ偏光におけるそれぞれ
反射強度RpおよびRsを示したものである。なお
偏光していない光に対する反射強度は、これらの
中間（Rp＋Rs）／２となる。 FIG. 2 is a diagram showing the configuration of essential parts of an example of a focus detection device previously proposed by the applicant. The apparatus of this example has the same configuration as the apparatus shown in FIG. 1 until it is reflected by the disk 6, so the same reference numerals as those shown in FIG. 1 represent the same optical members. The parallel light beam reflected by the polarizing prism 3 is incident on the detection prism 10, and the light beam reflected by the reflecting surface 11 is received by the detector 12. The reflective surface 11 is set to form a substantially critical angle with respect to an incident light beam (parallel light beam) in a focused state. In this way, in the focused state, all the rays reflected by the polarizing prism 3 are reflected by the reflecting surface 1.
1 (actually, the state of the reflecting surface is not perfect, so some light is transmitted in the n direction shown in the figure),
When the disc 6 deviates from the in-focus state in the direction a, the light beam reflected by the polarizing prism 3 becomes a light beam having a maximum tilt component represented by a i1 to a i2 with respect to the reflecting surface 11. Further, when the disk 6 deviates from the focused state in the direction b, the incident light rays on the reflective surface 11 become a bundle of light rays having tilt components shown by b i1 to b i2 . That is, when the disk 6 is out of focus, the light beams incident on the reflective surface 11 change continuously around the critical angle, except for the central ray (dotted chain line) on the optical axis. Therefore, when the disk 6 is displaced in directions a and b and is out of focus, the intensity of reflection at the reflecting surface 11 suddenly changes with a slight change in the angle of incidence near the critical angle, as shown in FIG. Because the light changes, the light and dark states are reversed across the plane perpendicular to the plane of the paper containing the central ray. On the other hand, in the focused state, such brightness and darkness do not appear because the light is totally reflected uniformly. The photodetector 12 detects the light intensity distribution of the reflected light from the reflecting surface 11, and is divided into two parts with the central ray (optical axis) as the border, as shown in the plan view in FIG. It is configured with two light receiving areas 12A and 12B. Note that FIG. 3 shows the reflection intensities R p and R s for P-polarized light and S-polarized light, respectively, when the refractive index of the detection prism 10 is 1.50. Note that the reflection intensity for unpolarized light is between these two (R p +R s )/2.
第２図において、デイスク６がａ方向に変位し
たときは、反射面１１に入射する光のうち中心光
線より図において下側の光束は、一番外側の入射
光線ai1を筆頭としてすべての入射光線の入射角
は臨界角よりも小さくなる。したがつて、この部
分では透過光が存在し、一番外側の透過光線at1
からｎ迄を含む光線束が透過する。この透過した
分だけ、一番外側の反射光線ar1から中心光線迄
を含む反射光線束の強度は弱められる。反射面１
１に入射する光のうち、中心光線より図において
上側の光束は、一番外側の入射光線ai2を筆頭と
してすべての入射光線の入射角は臨界角よりも大
きくなる。したがつて、この部分では透過光が存
在せず、入射した全ての光線が、一番外側の反射
光線ar2から中心光線迄を含む光束に含まれて反
射する。したがつて、この場合には、光検出器１
２上での光量分布は、受光領域１２Ａが暗くな
り、受光領域１２Ｂが明るくなる。 In FIG. 2, when the disk 6 is displaced in the direction a, among the light incident on the reflective surface 11, the light beam below the center ray in the figure is composed of all the incident light beams starting from the outermost incident ray a i1 . The angle of incidence of the ray will be smaller than the critical angle. Therefore, there is transmitted light in this part, and the outermost transmitted light ray a t1
A bundle of rays including from n to n is transmitted. The intensity of the reflected ray bundle including the outermost reflected ray a r1 to the center ray is weakened by this transmitted amount. Reflective surface 1
Among the light beams incident on 1, the angles of incidence of all the light beams above the central ray in the figure, starting with the outermost incident ray a i2 , are larger than the critical angle. Therefore, there is no transmitted light in this part, and all the incident light rays are reflected as being included in the light flux that includes the outermost reflected light ray a r2 to the center ray. Therefore, in this case, the photodetector 1
Regarding the light amount distribution on 2, the light receiving area 12A becomes dark and the light receiving area 12B becomes bright.
これに対し、デイスク６がｂ方向に変位したと
きは、反射面１１への入射光線の傾きの関係が上
述したａ方向の場合と逆になり、したがつて光検
出器１２の領域１２Ａ，１２Ｂの明暗の関係が逆
になる。この場合の反射面１１における反射光お
よび透過光をそれぞれ符号br1，br2，bt2で示す。 On the other hand, when the disk 6 is displaced in the b direction, the relationship of the inclination of the incident light beam to the reflective surface 11 is opposite to that in the a direction described above, and therefore The relationship between light and dark is reversed. The reflected light and transmitted light on the reflective surface 11 in this case are indicated by symbols b r1 , b r2 , and b t2 , respectively.
なお、合焦状態では光検出器１２の受光領域１
２Ａ，１２Ｂへの入射光量はそれぞれ等しくな
る。 Note that in the focused state, the light receiving area 1 of the photodetector 12
The amounts of light incident on 2A and 12B are equal.
したがつて、各受光領域１２Ａ，１２Ｂの出力
の差を検出することにより、その量および極性か
らずれの量および方向を表わす焦点誤差信号を得
ることができ、この信号に基づいて対物レンズ５
を光軸方向に移動制御するフオーカツシング制御
を行なうことができると共に、受光領域１２Ａ，
１２Ｂの出力の和からデイスク６に記録された情
報信号を検出することができる。しかも合焦状態
では反射面１１での透過成分が殆んどないから、
光量の損失が極めて少ないと共に、合焦から外れ
た場合には、中心光線を境にいずれか一方の側の
光束が全反射され、他方の側の光束の反射強度が
極端に減少するから受光領域１２Ａ，１２Ｂにお
ける光量差が著しくなる。したがつて、十分正確
に焦点検出を行なうことができる。 Therefore, by detecting the difference between the outputs of the respective light receiving areas 12A and 12B, a focus error signal representing the amount and direction of deviation can be obtained from the amount and polarity, and based on this signal, the objective lens 5
It is possible to perform focusing control to control the movement of the light receiving areas 12A,
The information signal recorded on the disk 6 can be detected from the sum of the 12B outputs. Moreover, in the focused state, there is almost no transmitted component on the reflective surface 11,
The loss of light quantity is extremely small, and if the focus is out of focus, the light beam on either side of the central ray will be totally reflected, and the reflection intensity of the light beam on the other side will be extremely reduced. The difference in light amount between 12A and 12B becomes significant. Therefore, focus detection can be performed with sufficient accuracy.
ビデオデイスクのような情報記録媒体から情報
を読み取る際には上述したようにフオーカツシン
グ制御をして光スポツトが常に情報記録面に集束
するようにする必要があると共に光スポツトが所
定の情報トラツクから外れることなく常にその上
を走査するようにトラツキング制御が必要であ
る。第２図および第３図につき上述した焦点検出
装置ではデイスクからの反射光を平行光束若しく
はそれに近い光束として光検出器に入射させてい
るため、光検出器までに充分な光路長がないと光
スポツトの像が形成されないので、例えば３ビー
ム方式によるトラツキング誤差信号を取り出すこ
とはできず、光スポツトを情報トラツクに対し直
角な方向に微小量振り、その際の光量の変化を検
出してトラツキング誤差信号を取り出す所謂ウオ
ツブリング方式を利用できるだけであり、設計の
自由度が狭い欠点がある。 When reading information from an information recording medium such as a video disk, it is necessary to perform focusing control as described above so that the light spot is always focused on the information recording surface, and also to ensure that the light spot is focused on a predetermined information track. Tracking control is required to always scan over it without straying from it. In the focus detection device described above with reference to FIGS. 2 and 3, the reflected light from the disk is incident on the photodetector as a parallel beam or a parallel beam, so if there is not a sufficient optical path length to the photodetector, the light Since an image of the spot is not formed, it is not possible to extract a tracking error signal using, for example, a three-beam method.The tracking error signal is determined by swinging the optical spot a minute amount in a direction perpendicular to the information track and detecting the change in the amount of light at that time. It is only possible to use a so-called wobbling method for extracting signals, which has the disadvantage that the degree of freedom in design is limited.
本発明は上述した臨界角を利用して焦点誤差を
高感度で検出できるという利点をそのまま維持
し、トラツキング誤差を３ビーム方式で行なうこ
とができるようにした光学的情報読取装置を提供
せんとするものである。 The present invention aims to provide an optical information reading device that maintains the above-mentioned advantage of being able to detect focus errors with high sensitivity by utilizing the critical angle, and can detect tracking errors using a three-beam method. It is something.
第４図は本発明の情報読取装置の１実施例を示
すものである。３つのビームを発生させるため
に、光源２１からの光束を、レンズ３５，３６間
の平行光束光路中に配置した回析格子３７に通
す。この回析格子３７からの零次、±１次のビー
ムを３ビームとして用い、コリメータレンズ２
２、光路分割プリズム２３、1/4波長板２４およ
び対物レンズ２５を介してビデオデイスク２６上
に光スポツトとして照射する。ビデオデイスク２
６からの反射光を対物レンズ２５により集光し、
１／４波長板２４、光路分割プリズム２３、反射面
２７Ａを有するプリズム２７を経て光検出装置３
８に入射させる。 FIG. 4 shows one embodiment of the information reading device of the present invention. In order to generate three beams, the light beam from the light source 21 is passed through a diffraction grating 37 placed in the parallel beam path between lenses 35 and 36. The zero-order and ±1-order beams from this diffraction grating 37 are used as three beams, and the collimator lens 2
2. A light spot is irradiated onto the video disk 26 via the optical path splitting prism 23, the 1/4 wavelength plate 24, and the objective lens 25. video disc 2
The reflected light from 6 is focused by an objective lens 25,
The photodetector 3 passes through the quarter-wave plate 24, the optical path splitting prism 23, and the prism 27 having a reflective surface 27A.
8.
次に本例装置の動作を第５Ａ図〜第５Ｃ図をも
参照して説明する。光検出装置３８は４分割され
ており、中央のビームは情報トラツクの長手方向
に二分割された光検出器３８Ａおよび３８Ｂに入
射し、左右のビームは情報トラツクの幅方向に二
分割された光検出器３８Ｃおよび３８Ｄにそれぞ
れ入射する。 Next, the operation of the apparatus of this example will be explained with reference to FIGS. 5A to 5C. The photodetector 38 is divided into four parts, and the central beam enters the photodetectors 38A and 38B, which are divided into two in the longitudinal direction of the information track, and the left and right beams are divided into two in the width direction of the information track. The light is incident on detectors 38C and 38D, respectively.
第５Ａ図に合焦していると共にトラツキングず
れもない状態を示し、この状態では光検出器３８
Ａと３８Ｂの出力の差を求める差動増幅器３９の
出力は殆んどなく、焦点誤差信号は現われない。
情報信号はこれら光検出器３８Ａおよび３８Ｂの
出力の和を求める加算器４０から得られる。ま
た、光検出器３８Ｃおよび３８Ｄの出力の差を求
める差動増幅器４１の出力もなく、トラツキング
誤差信号も現われない。 FIG. 5A shows a state in which the photodetector 38 is in focus and there is no tracking deviation.
There is almost no output from the differential amplifier 39 that determines the difference between the outputs of A and 38B, and no focus error signal appears.
The information signal is obtained from an adder 40 which sums the outputs of these photodetectors 38A and 38B. Furthermore, there is no output from the differential amplifier 41 for determining the difference between the outputs of the photodetectors 38C and 38D, and no tracking error signal appears.
第５Ｂ図はビデオデイスク２６が対物レンズ２
５から遠ざかる方向に変位すると共に情報トラツ
クの幅方向の一方向にずれている状態を示し、差
動増幅器３９からは正極性の焦点誤差信号が得ら
れると共に差動増幅器４１からは負極性のトラツ
キング誤差信号が得られる。 FIG. 5B shows that the video disk 26 is connected to the objective lens 2.
5 and in one direction in the width direction of the information track, a positive polarity focus error signal is obtained from the differential amplifier 39, and a negative polarity tracking signal is obtained from the differential amplifier 41. An error signal is obtained.
また第５Ｃ図は、ビデオデイスク２６が対物レ
ンズ２５に近付く方向に変位していると共に情報
トラツクの幅方向に見て第５Ｂ図の場合とは反対
方向にずれている状態を示す。この場合には差動
増幅器３９からの負極性の焦点誤差信号が得ら
れ、差動増幅器４１からは正極性のトラツキング
誤差信号が得られる。 Further, FIG. 5C shows a state in which the video disk 26 is displaced in a direction approaching the objective lens 25 and is also shifted in the opposite direction from that in FIG. 5B when viewed in the width direction of the information track. In this case, a negative focus error signal is obtained from the differential amplifier 39, and a positive tracking error signal is obtained from the differential amplifier 41.
上述したようにして焦点誤差信号、トラツキン
グ誤差信号および情報信号を得ることができる。 A focus error signal, a tracking error signal and an information signal can be obtained as described above.
本発明は上述した例にのみ限定されるものでは
なく、幾多の変形または変更が可能である。例え
ば、偏光プリズム２３と検出プリズム２７との間
に90゜回転子を介在させて、検出プリズム２７へ
の入射光束をＰ偏光とすることができる。このよ
うすれば、第３図から明らかなように、臨界角近
傍において反射強度の変化が急峻となるから、検
出感度を更に高めることができる。また、このよ
うに検出プリズム２７にＰ偏光を入射させるに
は、90゜回転子を使わなくても、偏光プリズム２
３と検出プリズム２７との関係を90゜紙面垂直方
向に回転して配置してもよい。更に上述した例で
は偏光している光を使用するものについて説明し
たが、偏光していない光を使用する場合でも本発
明を有効に適用することができ、その場合には偏
光プリズム２３の代りにハーフミラーを用いるこ
とができる。 The present invention is not limited to the above-mentioned examples, but can be modified or modified in many ways. For example, by interposing a 90° rotator between the polarizing prism 23 and the detection prism 27, the light beam incident on the detection prism 27 can be made into P-polarized light. If this is done, as is clear from FIG. 3, the change in reflection intensity becomes steep near the critical angle, so the detection sensitivity can be further increased. In addition, in order to make the P-polarized light enter the detection prism 27 in this way, it is not necessary to use a 90° rotator.
3 and the detection prism 27 may be rotated by 90 degrees in the direction perpendicular to the plane of the paper. Furthermore, although the above-described example uses polarized light, the present invention can be effectively applied even when unpolarized light is used, and in that case, the polarizing prism 23 is replaced with A half mirror can be used.
第１図は従来の焦点検出方式を適用する光学的
読取装置の構成を示す線図、第２図は本願人が先
に提案した焦点検出方法を実施する光学的読取装
置の構成を示す線図、第３図は臨界角近傍での反
射強度の一例を示す線図、第４図は本発明の光学
的情報読取装置の一実施例の構成を示す線図、第
５Ａ図〜第５Ｃ図は同じくその動作を説明するた
めの線図である。
２１……レーザ光源、２２……コリメータレン
ズ、２３……偏光プリズム、２４……1/4波長板、
２５……対物レンズ、２６……デイスク、２７…
…検出プリズム、２７Ａ……反射面、３７……回
析格子、３８Ａ〜３８Ｄ……光検出器、３９，４
１……差動増幅器、４０……加算器。
FIG. 1 is a diagram showing the configuration of an optical reading device that applies a conventional focus detection method, and FIG. 2 is a diagram showing the configuration of an optical reading device that implements the focus detection method previously proposed by the applicant. , FIG. 3 is a diagram showing an example of the reflection intensity near the critical angle, FIG. 4 is a diagram showing the configuration of an embodiment of the optical information reading device of the present invention, and FIGS. 5A to 5C are diagrams showing an example of the reflection intensity near the critical angle. It is a diagram for explaining the operation similarly. 21...Laser light source, 22...Collimator lens, 23...Polarizing prism, 24...1/4 wavelength plate,
25...Objective lens, 26...Disc, 27...
...Detection prism, 27A...Reflection surface, 37...Diffraction grating, 38A-38D...Photodetector, 39,4
1... Differential amplifier, 40... Adder.
Claims (1)
前記対物レンズにより被照射物体に集束させ、１
本の光束の反射光の少く共一部を、該反射光路中
の一つの光線に対してほぼ臨界角となるようにし
た反射面を有するプリズムに入射させ、このプリ
ズムの反射面で反射された光の光量変化を検出す
ることにより、前記対物レンズの前記被照射物体
に対する焦点誤差信号を得ると共に、他の２本の
光束の被照射物体からの反射光の光量を比較する
ことによりトラツキング誤差信号を得ることを特
徴とする焦点並びにトラツキング誤差信号検出装
置。1 The three beams emitted toward the objective lens are focused on the irradiated object by the objective lens, and 1
A small portion of the reflected light of the book's light beam is made incident on a prism having a reflective surface that forms an approximately critical angle with respect to one ray in the reflected optical path, and the reflected light is reflected by the reflective surface of this prism. By detecting changes in the amount of light, a focus error signal of the objective lens with respect to the object to be irradiated is obtained, and by comparing the amounts of light reflected from the object to be irradiated with the other two beams, a tracking error signal is obtained. A focusing and tracking error signal detection device characterized in that:
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13699679A JPS5661044A (en) | 1979-10-25 | 1979-10-25 | Optical information reader |
| GB8020097A GB2057218B (en) | 1979-06-25 | 1980-06-19 | Detecting focussing error |
| NL8003659A NL192406C (en) | 1979-06-25 | 1980-06-24 | Device for detecting a focusing error signal for an objective lens when scanning an information carrier. |
| FR8014007A FR2459991A1 (en) | 1979-06-25 | 1980-06-24 | METHOD AND DEVICE FOR DETECTING A FOCUSING ERROR SIGNAL |
| DE19803023779 DE3023779A1 (en) | 1979-06-25 | 1980-06-25 | METHOD FOR DETERMINING THE FOCUS OF AN LENS WITH REGARD TO AN OBJECT AND DEVICE FOR IMPLEMENTING THE METHOD |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13699679A JPS5661044A (en) | 1979-10-25 | 1979-10-25 | Optical information reader |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5661044A JPS5661044A (en) | 1981-05-26 |
| JPS641858B2 true JPS641858B2 (en) | 1989-01-12 |
Family
ID=15188344
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13699679A Granted JPS5661044A (en) | 1979-06-25 | 1979-10-25 | Optical information reader |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5661044A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5766533A (en) * | 1980-10-09 | 1982-04-22 | Olympus Optical Co Ltd | Optical information reader |
| JPS6043240A (en) * | 1983-08-19 | 1985-03-07 | Mitsubishi Electric Corp | Optical signal reader |
-
1979
- 1979-10-25 JP JP13699679A patent/JPS5661044A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5661044A (en) | 1981-05-26 |
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