JP4002199B2

JP4002199B2 - Light wave distance meter

Info

Publication number: JP4002199B2
Application number: JP2003053701A
Authority: JP
Inventors: 速見木川
Original assignee: 株式会社ソキア
Priority date: 2003-02-28
Filing date: 2003-02-28
Publication date: 2007-10-31
Anticipated expiration: 2023-02-28
Also published as: JP2004264116A

Description

【０００１】
【発明の属する技術分野】
本発明は、ターゲットに向けて測距光を出射し、ターゲットからの反射光を受光する位相差方式の光波距離計に関する。
【０００２】
【従来の技術】
従来用いられていた光波距離計としては、下記特許文献１に開示されているものがあり、これを図４に示す。この光波距離計では、光源３から発した測距光Ｌは、プリズム１２，ミラー４、対物レンズ５等の送光光学系を経て、測点上に置かれたターゲット６を照射する。ターゲット６で反射された測距光Ｌは、対物レンズ５、ミラー４等の受光光学系を経て、検出器（受光素子）７に入射し、検出器７に測距信号Ｍを発生させる。
【０００３】
光源３は変調器２に接続されていて、光源３から発する測距光Ｌは、発振器１で発生させた基準信号Ｋによって変調されている。この基準信号Ｋと、検出器７で発生した測距信号Ｍは、ともに位相計９に入力され、両信号Ｋ、Ｍの位相差を求めると、この位相差と光の速さからターゲット６までの距離が求まる。
【０００４】
この光波距離計では、前記距離計測中に光源３から発した測距光Ｌを、切換器８によって、プリズム１０、１１、１２を経る内部光路を通って検出器７に至る参照光Ｒに切り換え、測距信号Ｍとの位相差を求め、前述の測距光Ｌを用いて求めた距離に関して、機械に固有の誤差等の補正が行われる。
【特許文献１】
特許第３２３６９４１号公報
【０００５】
【発明が解決しようとする課題】
ところで、検出器７へ入射する測距光Ｌの光量が変化すると、位相計で検出される基準信号Ｋと測距信号Ｍとの位相差、すなわち測定距離が変化することが知られている。しかも、その光量の変化と位相差（測定距離）の変化の関係が機械ごとに異なるものである。このため、従来は、機械の組立終了後の調整時に、機械ごとに光量に応じた位相差の補正量を調べて、光量に応じて位相差が補正されるように機械毎に電気回路の定数を調節していた。
【０００６】
しかしながら、電気回路の定数を調節することでは、機械によっては、検出器７へ入射する測距光Ｌの光量の全レベルにわたっては位相差を補正できない場合もある。このような場合には、測距中に陽炎等の大気の揺らぎにより、検出器７へ入射する測距光Ｌの光量が大きく変動した場合には、測距誤差が残るという問題があった。
【０００７】
本発明は、前記問題に鑑みてなされたもので、位相差方式の光波距離計において、受光素子へ入射する測距光の光量の変動による測距誤差を、機械にかかわらず常に確実に補正できるようにすることを課題とする。
【００１０】
【課題を解決するための手段】
上記の課題を解決するため、請求項１に係る発明の光波距離計では、基準信号を発生させる基準信号発振器と、基準信号で変調された測距光を出射する光源と、測距光を送光する送光光学系と、ターゲットで反射してきた測距光を受光する受光光学系と、受光した測距光を測距信号に変換する受光素子と、前記測距信号を周波数を下げた中間周波信号に変換する周波数変換器と、前記基準信号と同期して前記中間周波信号を多数周期にわたってサンプリングするＡ／Ｄ変換器と、前記Ａ／Ｄ変換器でサンプリングされた中間周波信号の同位相毎に加算した合成データを正弦波にあてはめ、該正弦波の初期位相から距離を算出する演算手段と、前記受光素子へ入射する測距光の光量の全レベルにわたって、前記中間周波信号の振幅に応じた前記初期位相の補正量を示す補正情報を予め記憶した記憶手段を備え、前記演算手段は、距離測定時に前記中間周波信号の振幅の度数分布を記憶手段に記憶させ、前記度数分布と前記補正情報を用いて、前記補正量に前記中間周波信号の振幅の重みつけをした加重平均を算出し、該加重平均を用いて前記初期位相の補正を行うことを特徴とする。
【００１１】
前記請求項１に係る発明の光波距離計によれば、受光素子へ入射する測距光の光量の全レベルにわたって、前記光量に応じた前記位相差又は前記初期位相の補正量を示す補正情報を予め記憶手段に記憶しており、距離測定時、前記中間周波信号の振幅の度数分布を記憶手段に記憶させ、前記度数分布と前記補正情報とを用いて初期位相を補正しているので、１回の測定における前記中間周波信号のサンプリング開始からサンプリング終了までの期間内で受光素子へ入射する光量が大きく変動しても測距誤差を常に確実に補正できる。
【００１２】
【発明の実施の形態】
以下、本発明の好ましい実施の形態について、添付図面を参照して詳細に説明する。
【００１３】
図１に本発明に係る光波距離計の一実施例を示す。この光波距離計では、レーザダイオ−ド等の光源２０から送光された測距光Ｌは、図示しない送光光学系を経て、測点上に置かれたターゲット（プリズム等）２２に向けて出射される。光源２０は変調器２４に接続されており、測距光Ｌは基準信号発振器２６で発生された基準信号Ｋによって変調されている。
ターゲット２２で反射された測距光Ｌは、図示しない受光光学系と、測距光Ｌの光量を調整する絞り２７を経て、受光素子（フォトダイオード）２８に導かれる。すると、受光素子２８によって、測距光Ｌが測距信号Ｍに変換され、測距信号Ｍは、高周波増幅器３０で増幅された後に、バンドパスフィルタ３２でノイズを除去される。
【００１４】
さらに、この測距信号Ｍは、混合器３４と局部発振器３６からなる周波数変換器３７で、局部発振器３６で発生させた局部発振信号Ｑと乗算され、両信号Ｍ、Ｑの周波数の和となる周波数と、両信号Ｍ、Ｑの周波数の差となる２つの周波数に変換される。ここで、両信号Ｍ、Ｑの周波数の差となる周波数のみをローパスフィルタ３８で選り分けて中間周波信号（以下、単に中間周波と記載する。）Ｎに周波数を落とした後に、これを中間周波増幅器４０で増幅するとともに波形成形をする。増幅された中間周波Ｎは、Ａ／Ｄ変換器４２でデジタル信号に変換され、ＣＰＵ４４（演算手段）に入力され、メモリ（記憶手段）４６に記憶される。ここで、測距信号Ｍを中間周波Ｎに変換するのは、周波数の低い所定周波数とすることにより、増幅し易くして安定に高利得が得られること、中間周波Ｎ以外をカットして高いＳ／Ｎ比が得られること、１周期内に余裕を持ってできるだけ多数回サンプリングする時間を確保すること等のためである。
【００１５】
距離測定を行う際には、ＣＰＵ４４から基準信号発振器２６とＡ／Ｄ変換器４２に同期信号Ｐを送ることにより、基準信号発振器２６で基準信号Ｋを発生させるとともに、Ａ／Ｄ変換器４２で基準信号Ｋと同期の取れたサンプリングを行う。この距離測定中、絞り２７の開度は固定される。
【００１６】
図２に示したように、Ａ／Ｄ変換器４２のサンプリング周期は、中間周波Ｎの１周期分を常に一定の位相角でサンプリングするように、例えば、１周期をｎ（ｎ≧３）等分するように決定される。このサンプリング周期で中間周波Ｎを数千以上の多数周期にわたって連続してサンプリングする。この際、Ａ／Ｄ変換器４２の入力レンジを越えたり、入力レンジに対して小さすぎる中間周波Ｎのサンプリングデータは破棄する。
【００１７】
サンプリングデータをメモリ４６に記憶するには、中間周波Ｎの１周期分のｎ個のデータに対する記憶領域をメモリ４６内に用意し、図３に示したように、同位相のサンプリングデータを加算して記憶していく。こうして、同位相のサンプリングデータが加算された大きな振幅の１周期分の中間周波Ｎの合成データが作成される。この合成データは、最小二乗法により正弦波Ｓにあてはめられ、この正弦波Ｓの初期位相φを求める。基準信号Ｋと同期を取ってＡ／Ｄ変換器４２はサンプリングしているから、初期位相φは基準信号Ｋと測距信号Ｍの位相差に等しくなり、この初期位相φからターゲット２２までの距離が算出される。
【００１８】
ところで、陽炎等の大気の揺らぎにより、測距中においても受光素子２８に入射する測距光Ｌの光量は大きく変動するので、この測距光Ｌの変動による初期位相φの補正が必要になる。
【００１９】
そこで、この光波距離計は、組立終了後の調整時に機械ごとに、同一のターゲットを視準したうえで、絞り２７の開度を一定にし、受光素子２８へ入射する測距光Ｌの光量を一定に保ちながら、Ａ／Ｄ変換器４２に入力された中間周波Ｎの振幅ａｉ（受光素子２８へ入射する測距光Ｌの光量又は測距信号Ｍの振幅に対応する値である。）のときに必要な初期位相φの補正量Δφｉ（ａｉ）を調べて、メモリ４６内に設けられている補正テーブル記憶領域に書き込んでいく。以下同様に、絞り２７の開度を変化させ、受光素子２８へ入射する測距光Ｌの光量の全レベルにわたって、中間周波Ｎの振幅ａｉのときに必要な初期位相φの補正量Δφｉ（ａｉ）を補正テーブル記憶領域に書き込んでいく。こうして、絞り２７の開度毎に受光素子２８へ入射する測距光Ｌの光量の全レベルにわたって、Ａ／Ｄ変換器４２に入力された中間周波Ｎの振幅ａｉと、このときの初期位相φの補正量Δφｉ（ａｉ）を記憶した補正テーブル（補正情報）がメモリ４６に記憶される。
【００２０】
もちろん、この補正テーブルの代わりに、Ａ／Ｄ変換器４２に入力された中間周波Ｎの振幅がａｉであるときの初期位相φの補正量Δφｉ（ａｉ）を求める補正式（補正情報）を記憶させてもよい。
【００２１】
距離測定に際しては、図３に示したように、中間周波Ｎの多数周期を同位相毎に加算した合成データＳを用いているため、初期位相φの補正量ΔΦは、中間周波Ｎのｉ番目の周期に係る振幅がａｉであり、この振幅ａｉのときの補正量をΔφｉ（ａｉ）とすると
ΔΦ＝tan^−１[Σ{ai・sin(Δφi(ai))}／Σ{ai・cos(Δφi(ai))}]
となる。ここで、Δφｉ（ａｉ）は一般に小さいから、
ΔΦ＝tan^−１[Σ{ai・Δφi(ai)}／Σai]
＝Σ{ai・Δφi(ai)}／Σai
と近似できる。結局、初期位相φの補正量ΔΦは、補正量Δφｉ（ａｉ）を中間周波Ｎの振幅ａｉで重みづけした加重平均となる。真の初期位相は、測定された初期位相φから前述の補正量ΔΦを減算すればよい。
【００２２】
この光波距離計で距離測定を行うには、距離測定に先だって、光波距離計を作動させ、予め中間周波Ｎの数周期分をサンプリングして、中間周波Ｎの最大レベルａmaxと最小レベルａminを示すサンプリング位置を検出する。そして、Ａ／Ｄ変換器４２の入力レベルを複数の階級に区分した記憶領域をメモリ４６内に用意する。それから改めて距離測定を開始し、中間周波Ｎの１周期分を検出するごとに、同位相のサンプリングデータを加算した中間周波Ｎの合成データＴ（図３参照）をメモリ４６に記憶するとともに、先だって求めた最大レベルａmaxと最小レベルａminを示すサンプリング位置の間のレベル差から、中間周波Ｎの振幅ａｉの階級を求め、その階級の度数に１を加算していき、振幅ａｉの度数分布もメモリ４６に記憶する。サンプリング終了後に、中間周波Ｎの合成データＴを正弦波Ｓにあてはめ、該正弦波Ｓの初期位相φを求めるとともに、振幅ａｉの度数分布を用いて、補正量Δφｉ（ａｉ）を中間周波Ｎの振幅ａｉの重みつけをした加重平均Σ{ai・Δφi(ai)}／Σaiを算出する。そして、初期位相φから補正量ΔΦとして前記加重平均Σ {ai ・Δφ i(ai)} ／Σ aiを減算して、ターゲット２２までの距離を算出する。
【００２３】
もちろん、本実施例の光波距離計も、測距光Ｌを絞り２７ａを含む機械の内部光路を通って受光素子２８に至る参照光Ｒに切り換えることもできる。この参照光Ｒを用いて測距することにより、前述の測距光Ｌを用いて求めた距離の補正がなされることは、従来例と同じである。
【００２４】
本実施例では、絞り２７の開度毎に受光素子２８へ入射する測距光Ｌの光量の全レベルにわたって、Ａ／Ｄ変換器４２に入力された中間周波Ｎの振幅ａｉと、このときの初期位相φの補正量Δφｉ（ａｉ）を記憶した補正テーブル記憶領域がメモリ４６に記憶されているので、どのような光波距離計をどのような環境で使用しても、受光素子２８へ入射する測距光Ｌの光量変動による測距誤差を常に確実に補正できる
ところで、本発明は、前記実施例に限るものではなく、種々の変形が可能である。例えば、前記実施例では、測距信号Ｍを中間周波Ｎに変換しているが、基準信号Ｋの周波数が低い場合などは、バンドパスフィルタ３２から取り出した測距信号Ｍを直接Ａ／Ｄ変換器４２でサンプリングし、このサンプリングされた測距信号Ｍを用いて、距離測定することも可能である。この場合は、周波数変換器３７とローパスフィルタ３８と中間周波増幅器４０が不要になり回路が簡単になる。
【００２５】
また、図４に示した従来の光波距離計に対しても、検出器７の出力を本発明のＡ／Ｄ変換器４２に入力し、Ａ／Ｄ変換器４２で取り出したデータを本発明と同様にＣＰＵ４４とメモリ４６で処理すれば、位相計９から出力される位相差の補正量を算出することができる。
【００２６】
【発明の効果】
以上の説明から明らかなように、請求項１に係る発明の光波距離計によれば、受光素子へ入射する測距光の光量の全レベルにわたって、前記光量に応じた位相差又は初期位相の補正量を示す補正情報を予め記憶手段に記憶しており、距離測定時、前記中間周波信号の振幅の度数分布を記憶手段に記憶させ、前記度数分布と前記補正情報とを用いて初期位相を補正しているので、１回の測定における前記中間周波信号のサンプリング開始からサンプリング終了までの期間内で受光素子へ入射する測距光の光量が大きく変動した際にも、測距誤差を常に確実に補正できる。よって、本発明の光波距離計であれば、陽炎等の大気の揺らぎが大きい環境で使用しても測距誤差をほとんどなくすことができる。
【００２７】
【図面の簡単な説明】
【図１】本発明の一実施例に係る光波距離計のブロック図である。
【図２】中間周波信号をサンプリングした例を示す図である。
【図３】中間周波信号の同位相のサンプリングデータを加算した中間周波一周期分のデータを示す図である。
【図４】従来の光波距離計を説明する図である。
【符号の説明】
２０光源
２２ターゲット
２４変調器
２６基準信号発振器
２８受光素子
３７周波数変換器
４２Ａ／Ｄ変換器
４４ＣＰＵ（演算手段）
４６メモリ（記憶手段）
Ｋ基準信号
Ｌ測距光
Ｍ測距信号
Ｎ中間周波信号[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a phase difference type lightwave distance meter that emits distance measuring light toward a target and receives reflected light from the target.
[0002]
[Prior art]
Conventionally used light wave distance meters include those disclosed in Patent Document 1 below, which are shown in FIG. In this light wave distance meter, the distance measuring light L emitted from the light source 3 irradiates the target 6 placed on the measuring point through a light transmission optical system such as the prism 12, the mirror 4, and the objective lens 5. The distance measuring light L reflected by the target 6 is incident on a detector (light receiving element) 7 through a light receiving optical system such as the objective lens 5 and the mirror 4 and causes the detector 7 to generate a distance measuring signal M.
[0003]
The light source 3 is connected to the modulator 2, and the distance measuring light L emitted from the light source 3 is modulated by the reference signal K generated by the oscillator 1. The reference signal K and the distance measurement signal M generated by the detector 7 are both input to the phase meter 9, and when the phase difference between the signals K and M is obtained, the phase difference and the speed of light are used to obtain the target 6. The distance is obtained.
[0004]
In this optical wave distance meter, the distance measuring light L emitted from the light source 3 during the distance measurement is switched by the switch 8 to the reference light R that reaches the detector 7 through the internal optical path passing through the prisms 10, 11, and 12. Then, a phase difference from the distance measurement signal M is obtained, and an error inherent to the machine is corrected with respect to the distance obtained using the distance measurement light L described above.
[Patent Document 1]
Japanese Patent No. 3236941
[Problems to be solved by the invention]
By the way, it is known that when the light amount of the ranging light L incident on the detector 7 changes, the phase difference between the reference signal K detected by the phase meter and the ranging signal M, that is, the measurement distance changes. In addition, the relationship between the change in the amount of light and the change in the phase difference (measurement distance) is different for each machine. For this reason, conventionally, at the time of adjustment after the assembly of the machine, the correction amount of the phase difference corresponding to the light amount is checked for each machine, and the constant of the electric circuit for each machine so that the phase difference is corrected according to the light amount. Was adjusting.
[0006]
However, by adjusting the electric circuit constant, depending on the machine, the phase difference may not be corrected over the entire level of the distance measuring light L incident on the detector 7. In such a case, there has been a problem that a distance measurement error remains if the light amount of the distance measurement light L incident on the detector 7 fluctuates greatly due to fluctuations in the atmosphere such as a flame during distance measurement.
[0007]
The present invention has been made in view of the above problems, and in a phase-difference optical wave distance meter, it is always possible to reliably correct a ranging error due to a variation in the amount of distance measuring light incident on a light receiving element regardless of the machine. The challenge is to do so.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problem, in the optical distance meter of the invention according to claim 1 , a reference signal oscillator that generates a reference signal, a light source that emits distance measuring light modulated by the reference signal, and a distance measuring light are transmitted. A light-transmitting optical system, a light-receiving optical system that receives the distance-measuring light reflected by the target, a light-receiving element that converts the received distance-measuring light into a distance-measuring signal, and an intermediate frequency of the distance-measuring signal lowered A frequency converter for converting to a frequency signal; an A / D converter for sampling the intermediate frequency signal over a plurality of periods in synchronization with the reference signal; and an in- phase of the intermediate frequency signal sampled by the A / D converter The combined data added every time is applied to a sine wave, the calculation means for calculating the distance from the initial phase of the sine wave, and the amplitude of the intermediate frequency signal over the entire level of the amount of ranging light incident on the light receiving element. It said the response was Includes a pre-stored memory means correction information indicating the amount of correction of the period phase, said computing means, said at distance measuring the amplitude frequency distribution of the intermediate frequency signal is stored in the storage means, the correction information and the frequency distribution And calculating a weighted average obtained by weighting the amplitude of the intermediate frequency signal to the correction amount, and correcting the initial phase using the weighted average .
[0011]
According to inventions of the light wave distance meter according to claim 1, correction information across all levels of the light quantity of the measuring light incident on the light receiving element, which indicates a correction amount of the phase difference or the initial phase corresponding to the amount of light Is stored in advance in the storage means, and at the time of distance measurement, the frequency distribution of the amplitude of the intermediate frequency signal is stored in the storage means, and the initial phase is corrected using the frequency distribution and the correction information. Ranging errors can always be reliably corrected even if the amount of light incident on the light receiving element varies greatly within the period from the start of sampling of the intermediate frequency signal to the end of sampling in one measurement .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0013]
FIG. 1 shows an embodiment of a light wave distance meter according to the present invention. In this optical distance meter, distance measuring light L transmitted from a light source 20 such as a laser diode is emitted toward a target (prism or the like) 22 placed on a measurement point via a light transmission optical system (not shown). Is done. The light source 20 is connected to the modulator 24, and the distance measuring light L is modulated by the reference signal K generated by the reference signal oscillator 26.
The distance measuring light L reflected by the target 22 is guided to a light receiving element (photodiode) 28 through a light receiving optical system (not shown) and a diaphragm 27 for adjusting the amount of the distance measuring light L. Then, the ranging light L is converted into a ranging signal M by the light receiving element 28, and the ranging signal M is amplified by the high frequency amplifier 30 and then noise is removed by the band pass filter 32.
[0014]
Further, the ranging signal M is multiplied by a local oscillation signal Q generated by the local oscillator 36 by a frequency converter 37 including a mixer 34 and a local oscillator 36, and becomes the sum of the frequencies of both signals M and Q. It is converted into two frequencies which are the difference between the frequency and the frequency of both signals M and Q. Here, only the frequency that is the difference between the frequencies of the two signals M and Q is selected by the low-pass filter 38, and the intermediate frequency signal (hereinafter simply referred to as the intermediate frequency) is dropped to N, and then the intermediate frequency amplifier. Amplification at 40 and waveform shaping. The amplified intermediate frequency N is converted into a digital signal by the A / D converter 42, input to the CPU 44 (calculation means), and stored in the memory (storage means) 46. Here, the reason why the ranging signal M is converted to the intermediate frequency N is that it is easy to amplify and obtain a stable high gain by setting it to a predetermined low frequency, and is high by cutting other than the intermediate frequency N. This is because the S / N ratio can be obtained, for example, to ensure the time for sampling as many times as possible within a single period.
[0015]
When the distance is measured, the CPU 44 sends the synchronization signal P to the reference signal oscillator 26 and the A / D converter 42 to generate the reference signal K by the reference signal oscillator 26 and the A / D converter 42. Sampling synchronized with the reference signal K is performed. During this distance measurement, the opening of the diaphragm 27 is fixed.
[0016]
As shown in FIG. 2, the sampling period of the A / D converter 42 is, for example, one period of n (n ≧ 3) so that one period of the intermediate frequency N is always sampled at a constant phase angle. It is decided to divide. In this sampling period, the intermediate frequency N is sampled continuously over a large number of thousands or more. At this time, sampling data of the intermediate frequency N that exceeds the input range of the A / D converter 42 or is too small with respect to the input range is discarded.
[0017]
In order to store the sampling data in the memory 46, a storage area for n data for one cycle of the intermediate frequency N is prepared in the memory 46, and the sampling data of the same phase is added as shown in FIG. And remember. In this way, synthesized data of the intermediate frequency N for one period with a large amplitude obtained by adding the sampling data of the same phase is created. This synthesized data is applied to the sine wave S by the least square method, and the initial phase φ of the sine wave S is obtained. Since the A / D converter 42 is sampling in synchronization with the reference signal K, the initial phase φ is equal to the phase difference between the reference signal K and the distance measurement signal M, and the distance from the initial phase φ to the target 22. Is calculated.
[0018]
By the way, since the light amount of the distance measuring light L incident on the light receiving element 28 varies greatly even during distance measurement due to atmospheric fluctuations such as a hot flame, it is necessary to correct the initial phase φ due to the fluctuation of the distance measuring light L. .
[0019]
Therefore, this light wave distance meter collimates the same target for each machine at the time of adjustment after assembly is completed, makes the aperture of the diaphragm 27 constant, and sets the amount of the distance measuring light L incident on the light receiving element 28. While maintaining constant, the amplitude ai of the intermediate frequency N input to the A / D converter 42 (a value corresponding to the light amount of the ranging light L incident on the light receiving element 28 or the amplitude of the ranging signal M). The correction amount Δφi (ai) of the initial phase φ that is sometimes required is checked and written in a correction table storage area provided in the memory 46. Similarly, the amount of correction ΔΔi (ai) of the initial phase φ required for the amplitude ai of the intermediate frequency N over the entire level of the light amount of the distance measuring light L incident on the light receiving element 28 by changing the opening of the diaphragm 27. ) Is written in the correction table storage area. Thus, the amplitude ai of the intermediate frequency N input to the A / D converter 42 and the initial phase φ at this time over the entire level of the light amount of the ranging light L incident on the light receiving element 28 for each opening degree of the diaphragm 27. A correction table (correction information) storing the correction amount Δφi (ai) is stored in the memory 46.
[0020]
Of course, instead of this correction table, a correction formula (correction information) for obtaining the correction amount Δφi (ai) of the initial phase φ when the amplitude of the intermediate frequency N input to the A / D converter 42 is ai is stored. You may let them.
[0021]
In the distance measurement, as shown in FIG. 3, since the composite data S obtained by adding a large number of cycles of the intermediate frequency N for each phase is used, the correction amount ΔΦ of the initial phase φ is the i-th of the intermediate frequency N. If the amplitude of the period is ai, and the correction amount at this amplitude ai is Δφi (ai), ΔΦ = tan ⁻¹ [Σ {ai · sin (Δφi (ai))} / Σ {ai · cos ( Δφi (ai))}]
It becomes. Here, Δφi (ai) is generally small,
ΔΦ = tan ⁻¹ [Σ {ai · Δφi (ai)} / Σai]
= Σ {ai · Δφi (ai)} / Σai
Can be approximated. After all, the correction amount ΔΦ of the initial phase φ is a weighted average obtained by weighting the correction amount Δφi (ai) by the amplitude ai of the intermediate frequency N. The true initial phase may be obtained by subtracting the aforementioned correction amount ΔΦ from the measured initial phase φ.
[0022]
In order to perform distance measurement with this light wave distance meter, prior to the distance measurement, the light wave distance meter is operated, and several periods of the intermediate frequency N are sampled in advance to indicate the maximum level amax and the minimum level amin of the intermediate frequency N. Detect the sampling position. A storage area in which the input level of the A / D converter 42 is divided into a plurality of classes is prepared in the memory 46. Then starts anew distance measurement, each for detecting one cycle of the intermediate frequency N, stores synthesized data T of the intermediate frequency N obtained by adding the sampling data of the same phase (see FIG. 3) in the memory 46, The class of the amplitude ai of the intermediate frequency N is obtained from the level difference between the sampling positions indicating the maximum level amax and the minimum level amin obtained in advance, and 1 is added to the frequency of the class, and the frequency distribution of the amplitude ai is also obtained. Store in the memory 46. After the sampling is completed, the composite data T of the intermediate frequency N is applied to the sine wave S, the initial phase φ of the sine wave S is obtained, and the correction amount Δφi (ai) is calculated using the frequency distribution of the amplitude ai. A weighted average Σ {ai · Δφi (ai)} / Σai weighted with the amplitude ai is calculated. Then, the distance to the target 22 is calculated by subtracting the weighted average Σ {ai · Δφ i (ai)} / Σ ai as the correction amount ΔΦ from the initial phase φ.
[0023]
Of course, the light wave distance meter of this embodiment can also switch the distance measuring light L to the reference light R that reaches the light receiving element 28 through the internal optical path of the machine including the stop 27a. The distance obtained using the distance measuring light L is corrected by measuring the distance using the reference light R as in the conventional example.
[0024]
In the present embodiment, the amplitude ai of the intermediate frequency N input to the A / D converter 42 over the entire level of the light amount of the distance measuring light L incident on the light receiving element 28 for each opening of the diaphragm 27, and at this time Since the correction table storage area storing the correction amount Δφi (ai) of the initial phase φ is stored in the memory 46, the light is incident on the light receiving element 28 no matter what kind of light wave distance meter is used in any environment. The present invention is not limited to the above-described embodiment, and various modifications can be made where the ranging error due to the light amount fluctuation of the ranging light L can always be reliably corrected. For example, in the above embodiment, the ranging signal M is converted into the intermediate frequency N. However, when the frequency of the reference signal K is low, the ranging signal M taken out from the bandpass filter 32 is directly A / D converted. It is also possible to measure the distance using the sampled distance measuring signal M sampled by the device 42. In this case, the frequency converter 37, the low-pass filter 38, and the intermediate frequency amplifier 40 are not necessary, and the circuit is simplified.
[0025]
Also for the conventional optical distance meter shown in FIG. 4, the output of the detector 7 is input to the A / D converter 42 of the present invention, and the data extracted by the A / D converter 42 is the same as that of the present invention. Similarly, if processing is performed by the CPU 44 and the memory 46, the correction amount of the phase difference output from the phase meter 9 can be calculated.
[0026]
【The invention's effect】
As apparent from the above description, according to the inventions of the light wave distance meter according to claim 1, over the entire level of the light amount of the measuring light incident on the light receiving elements, the phase difference or the initial phase corresponding to the amount of light Correction information indicating the correction amount is stored in advance in the storage means, and at the time of distance measurement, the frequency distribution of the amplitude of the intermediate frequency signal is stored in the storage means, and the initial phase is determined using the frequency distribution and the correction information. Because it is corrected, even if the amount of ranging light incident on the light receiving element fluctuates greatly during the period from the start of sampling of the intermediate frequency signal to the end of sampling in one measurement , the ranging error is always assured. Can be corrected. Therefore, the light wave distance meter of the present invention can eliminate almost any distance measurement error even when used in an environment where atmospheric fluctuation is large, such as a hot flame.
[0027]
[Brief description of the drawings]
FIG. 1 is a block diagram of a lightwave distance meter according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of sampling an intermediate frequency signal.
FIG. 3 is a diagram illustrating data for one period of an intermediate frequency obtained by adding sampling data having the same phase of an intermediate frequency signal.
FIG. 4 is a diagram for explaining a conventional lightwave distance meter.
[Explanation of symbols]
20 light source 22 target 24 modulator 26 reference signal oscillator 28 light receiving element 37 frequency converter 42 A / D converter 44 CPU (calculation means)
46 Memory (memory means)
K reference signal L ranging light M ranging signal N intermediate frequency signal

Claims

A reference signal oscillator that generates a reference signal, a light source that emits a distance measuring light modulated by the reference signal, a light transmitting optical system that transmits the distance measuring light, and a light receiving that receives the distance measuring light reflected by the target An optical system; a light receiving element that converts received ranging light into a ranging signal; a frequency converter that converts the ranging signal into an intermediate frequency signal with a reduced frequency; and the intermediate frequency in synchronization with the reference signal. An A / D converter that samples a signal over a number of cycles and a synthesized data obtained by adding the same phase of the intermediate frequency signal sampled by the A / D converter are applied to a sine wave, and the distance from the initial phase of the sine wave And a storage means for preliminarily storing correction information indicating the correction amount of the initial phase according to the amplitude of the intermediate frequency signal over all levels of the light amount of the ranging light incident on the light receiving element. ,
The arithmetic means stores the frequency distribution of the amplitude of the intermediate frequency signal in the storage means at the time of distance measurement, and weights the amplitude of the intermediate frequency signal to the correction amount using the frequency distribution and the correction information. A light wave distance meter which calculates a weighted average and corrects the initial phase using the weighted average .