JP3595580B2 - Active ranging device - Google Patents

Description

となり、又各ＰＳＤのＮ_１ 端子とＮ_２ 端子の出力電流の和を取り、それをＩ_Ｎ とすると、前述の式（５），（８）及び上記式（１０）より

と表せる。
【００２８】
次に、被写体にコントラストがある場合を考える。この場合は図３に示すように、各ＰＳＤの受光スポット像の光重心位置はａだけ同一方向へ変移する。したがって、各ＰＳＤからの出力電流は以下の様になる。
【００２９】
Ｉ_Ｆ１＝ｋ×（Ｘ_１ −Ｓ_１ −ａ） ……………（１２）
Ｉ_Ｎ１＝ｋ×（Ｓ_１ ＋ａ） ……………（１３）
Ｉ_Ｆ２＝ｋ×（Ｘ_２ −Ｓ_２ ＋ａ） ……………（１４）
Ｉ_Ｎ２＝ｋ×（Ｓ_２ −ａ） ……………（１５）
これより、和電流は以下の様に表せる。
【００３０】

以上から明らかな様に、上記の式（１０）と（１６）及び上記の式（１１）と（１７）は同じであるので、本構成をとると、コントラスト被写体の場合も均一被写体と同じ出力電流が得られる。つまり、コントラストに依存しない信号が得られるものである。
【００３１】
この出力電流Ｉ_Ｆ とＩ_Ｎ は公知の信号処理回路で処理されて、測距情報が得られる。
【００３２】
尚、前記の式（９）を成立させるためにはトータル信号電流は受光レンズ１２，１４の開口量に比例するので、
√（Ｄ_１ ）／Ｘ_１ ＝√（Ｄ_２ ）／Ｘ_２ ＝ｋ …………（１８）
が成立つように、受光レンズ１２及びＰＳＤ１８，２０を設計すればよい。
【００３３】
図４は本実施例における測距装置の回路構成を示すブロック図である。
【００３４】
同図において、３０及び３２は電流・電圧変換回路を構成するＯＰアンプ、３４及び３６はその負帰還路に接続されたフィードバック抵抗であり、前記ＯＰアンプ３０には前記信号電流Ｉ_Ｆ が、又ＯＰアンプ３２には信号電流Ｉ_Ｎ が各々入力する。３８は二重積分を行う信号処理回路であり、前記ＯＰアンプ３０及び３２の出力が入力する。４０は二重積分用のコンデンサである。４２はワンチップマイクロコンピュータで、前記信号処理回路３８を制御するとともに、該回路の出力を入力して測距情報を演算する。
【００３５】
なお、二重積分を行う信号処理回路３８の構成及び動作は既に公知の技術なので、その説明は省略する。
【００３６】
（変形例）
本発明は、一眼レフカメラ，レンズシャッタカメラ，ビデオカメラ等のカメラに具備された場合を例にしているが、これに限定されるものではなく、双眼鏡等の光学機器であっても同様に適用することが出来るものである。
【００３７】
【発明の効果】
以上説明したように、本発明によれば、当該装置の小型化を達成しつつ、コントラストを持つ測距対象物に対しても高精度の測距を行うことができる。
【図面の簡単な説明】
【図１】本発明の一実施例におけるアクティブ測距装置に具備される投光レンズ及び受光レンズの配置を示す図である。
【図２】図１の投光レンズの焦点面に配置されたＩＲＥＤ及び各ＰＳＤを示す図である。
【図３】図２の各ＰＳＤの構造並びに被写体コントラストがキャンセルされる原理について説明する為の図である。
【図４】本発明の一実施例におけるアクティブ方式の測距装置の回路構成を示すブロック図である。
【符号の説明】
１０ 投光レンズ
１２，１４ 受光レンズ
１６ ＩＲＥＤ
１８，２０ ＰＳＤ[0001]
[Industrial applications]
The present invention relates to an improvement in an active distance measuring device including one light projecting optical system and a plurality of light receiving optical systems.
[0002]
[Prior art]
2. Description of the Related Art In a conventional camera, a so-called active distance measuring device that projects light from a light projecting device onto a subject, receives reflected light from the subject, and measures the distance of the subject from the amount of received light or the light receiving position is widely known.
[0003]
Compared to passive rangefinders, this rangefinder has the advantage of being more resistant to low-contrast subjects, and has the advantage of being able to measure distance in the dark without auxiliary light. It has the disadvantage of erroneous ranging if not hit. That is, in this case, the position of the center of gravity of the reflected light of the projection beam changes.
[0004]
In order to solve the above-mentioned drawbacks, Japanese Patent Application Laid-Open No. 63-235909 discloses that another light receiving element is arranged at a position symmetrical in the base line length direction around the light projecting means, and a contrast is obtained from the outputs of the two light receiving elements. A method for canceling a change in the position of the center of gravity of light due to a subject has been proposed.
[0005]
[Problems to be solved by the invention]
However, the above method provides an active distance measuring apparatus that does not depend on contrast in principle, and its effect is great, but the two light receiving means are arranged at the same base line length with the light emitting means as the center of symmetry. Therefore, the size of the device itself has increased, and it has been unsuitable for recent compact cameras.
[0006]
Object of the INVENTION An object of the present invention, while achieving the miniaturization of the device, to provide an active distance measuring device capable of measuring a distance is also highly accurate distance measurement object having a contrast It is.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a light projecting optical system including a light projecting element and a light projecting lens, and a first light receiving element as a light receiving element which is arranged at a predetermined base line distance from the light projecting optical system. A first light receiving optical system for distance measurement including a semiconductor position detecting element and a first light receiving lens, and a base line which is disposed in a direction perpendicular to the base line length direction and which is closer to the base than the first semiconductor position detecting element A second semiconductor position detecting element as a light receiving element having a small length in the long direction and a second light receiving optical system for contrast correction including a second light receiving lens having an aperture smaller than that of the first light receiving lens. The ratio of the opening amount of the first light receiving lens to the length of the first semiconductor position detecting element in the base line length direction; the opening amount of the second light receiving lens; and the ratio of the second semiconductor position detecting element. The length ratio in the base line length direction is made the same, and the first The sum of the inner output signal from the terminal F _1, F ₂ each other beauty second semiconductor position detecting elements, each other output from the outside of the terminal N _1, N ₂ of the first and second semiconductor position detecting element According to the present invention, there is provided an active distance measuring apparatus which outputs a signal which does not depend on the contrast according to the sum of the signals.
[0010]
【Example】
Hereinafter, the present invention will be described in detail based on illustrated embodiments.
[0011]
FIG. 1 shows an arrangement of a light projecting lens and a light receiving lens provided in an active distance measuring apparatus according to one embodiment of the present invention, and this figure is an arrangement view at a normal position as viewed from the front of a camera. .
[0012]
In the figure, 10 is the projection lens, 12 is a light receiving lens for distance measurement, a diameter of D _1. 14 is a light receiving lens for contrast correction, a diameter of D _2. Then, these diameters D ₁ and D ₂ are defined as D ₁ > D ₂ ... (1)
Is established to reduce the size of the device.
[0013]
As described above, the light receiving lens 14 for contrast correction is arranged near the light projecting lens 10 in a direction perpendicular to the direction of the base line length L1.
[0014]
FIG. 2 shows an IRED (infrared light emitting diode) as a light projecting element and a PSD (semiconductor position detecting element) as a light receiving element arranged on the focal plane of the light projecting lens 10.
[0015]
In the figure, reference numeral 16 denotes an IRED (light emitting unit) which is a light emitting element. Reference numeral 18 denotes a PSD for distance measurement, which is a light receiving element, and reference numeral 20 denotes a PSD for contrast correction. The length of the PSD 18 is X ₁ and the width is Y _1. The length of the PSD 20 is X ₂ and the width is Y ₂ .
[0016]
As is clear from the figure, since the IRED 16 and the PSD 18 for distance measurement are arranged separated by the base line length L1, the reflected spot image of the IRED 16 on the PSD 18 moves in the base line length direction corresponding to the subject distance. Accordingly, the length X ₁ of PSD18 should be sufficient to cover the amount of the movement.
[0017]
On the other hand, since the distance between the PSD 20 for contrast correction and the IRED 16 in the base line length direction is substantially zero, the reflected spot image of the IRED 16 on the PSD 20 does not move in the base line length direction corresponding to the subject distance. Therefore, it is sufficient that the length X2 of the PSD ₂₀ is equal to or larger than the maximum width of the reflected spot image. That is,
X ₁ > X ₂ ............ (2)
Can satisfy the relationship.
[0018]
However, since the PSD 20 for contrast correction is arranged at a distance L2 (see FIG. 1) perpendicular to the base line length direction from the IRED 16, the reflected spot image of the IRED 16 on the PSD 20 corresponds to the subject distance. Move in the direction perpendicular to the base line length direction. Therefore, the width Y ₂ of PSD20 should be sufficient to cover the amount of the movement.
[0019]
On the other hand, the distance between the PSD 18 for distance measurement and the IRED 16 in the direction perpendicular to the base line length is substantially zero, so that the reflected spot image does not move in the direction perpendicular to the base line length. Therefore, the width Y ₁ of PSD18 is sufficient if the secured over the maximum width of the reflection spot image. That is,
Y ₁ <Y ₂ ... (3)
Can satisfy the relationship.
[0020]
The minimum value of Y ₂ satisfying the relation of the equation (3), the reflective spot image may be a minimum value that covers the movement amount corresponding to the distance. The distance L2 between the light projecting lens 10 and the light receiving lens 14 is sufficiently smaller set than base length L1, Y ₂ is sufficiently smaller than X _1.
[0021]
Therefore, the PSD 20 for contrast correction is sufficiently smaller than the PSD 18 for distance measurement, and in combination with the downsizing of the light receiving lens 14, the distance measuring device itself can be downsized.
[0022]
Next, the principle of canceling the subject contrast will be described with reference to FIG. The description of the components having the same reference numerals as those in FIG. 2 will be omitted.
[0023]
In the figure, reference numeral 22 denotes a light receiving spot image on the PSD 20 for contrast correction, and reference numeral 24 denotes a light receiving spot image on the PSD 18 for distance measurement. Both terminal names of each PSD are defined as F ₁ and N ₁ and F ₂ and N ₂ as shown in the figure. Also, the shift amount of the center point of the light receiving spot image 24 from the terminal F ₁ is S ₁ , and the shift amount of the center point of the light receiving spot image 22 from the terminal F ₂ is S ₂ .
[0024]
Now, consider a case where the subject has no contrast and the received light spot image has uniform luminance. The output current from the terminals _{F 1} and _{N 1} of the PSD 18, as each and _{I F1} and _{I N1,
I F1 = I T1 × (X} 1 -S 1) / X 1 ............... (4)
I _N1 = I _T1 × S ₁ / X ₁ (5)
Can be expressed as _{Here, I T1} is the total of the signal current _{I T1 = I F1 + I N1} ............... (6)
It is.
[0025]
Then, the output current from the terminals _{F 2} and _{N 2} of PSD20, as each and _{I F2} and _{I N2,} similarly _{I F2 = I T2 × (X} 2 -S 2) / X 2 ............... (7)
I _N2 = I _T2 × S ₂ / X ₂ (8)
Can be expressed as Here, _IT2 is a total signal current, and _IT2 = _IF2 + _IN2.
It is.
[0026]
Here, it is assumed that the ratio between the total signal current and the sensor length of each PSD is designed to satisfy the following relationship.
[0027]
I _T1 / X ₁ = I _T2 / X ₂ = k (9)
It takes the sum of the output currents of the _{F 1} terminal and _{F 2} terminals of the PSD, when it and _{I F,} the foregoing equation (4) and (7) and the equation (9)

Next, also takes the sum of the output currents of the _{N 1} terminal and _{N 2} terminals of the PSD, when it with _{I N,} the above-mentioned formula (5), (8) and the formula (10)

Can be expressed as
[0028]
Next, consider the case where the subject has contrast. In this case, as shown in FIG. 3, the position of the center of gravity of the light receiving spot image of each PSD shifts by a in the same direction. Therefore, the output current from each PSD is as follows.
[0029]
_{I F1 = k × (X 1} -S 1 -a) ............... (12)
I _N1 = k × (S ₁ + a) (13)
I _F2 = k × (X ₂ −S ₂ + a) (14)
I _N2 = k × (S ₂ −a) (15)
Thus, the sum current can be expressed as follows.
[0030]

As is clear from the above, since the above equations (10) and (16) and the above equations (11) and (17) are the same, this configuration provides the same output as a uniform subject even in the case of a contrast subject. A current is obtained. That is, a signal independent of contrast can be obtained.
[0031]
The output currents _IF and _IN are processed by a known signal processing circuit to obtain distance measurement information.
[0032]
In order to satisfy the above equation (9), the total signal current is proportional to the opening amount of the light receiving lenses 12 and 14, so that
√ (D ₁ ) / X ₁ = √ (D ₂ ) / X ₂ = k (18)
What is necessary is just to design the light receiving lens 12 and PSD18,20 so that may be satisfied.
[0033]
FIG. 4 is a block diagram showing a circuit configuration of the distance measuring apparatus in the present embodiment.
[0034]
In the figure, OP amplifier 30 and 32 constituting the current-voltage conversion circuit, 34 and 36 are feedback resistors connected to the negative feedback path, the signal current I _F to the OP amplifier 30 is also The signal current _IN is input to the OP amplifier 32. Reference numeral 38 denotes a signal processing circuit for performing double integration, to which the outputs of the OP amplifiers 30 and 32 are input. Numeral 40 is a double integration capacitor. Reference numeral 42 denotes a one-chip microcomputer which controls the signal processing circuit 38 and inputs the output of the circuit to calculate distance measurement information.
[0035]
Note that the configuration and operation of the signal processing circuit 38 that performs double integration is a known technique, and a description thereof will be omitted.
[0036]
(Modification)
The present invention exemplifies a case in which the present invention is provided in a camera such as a single-lens reflex camera, a lens shutter camera, and a video camera. However, the present invention is not limited to this. It is something you can do.
[0037]
【The invention's effect】
As described above, according to the present invention, high-precision distance measurement can be performed on a distance measurement target having contrast while achieving downsizing of the device .
[Brief description of the drawings]
FIG. 1 is a diagram showing an arrangement of a light projecting lens and a light receiving lens provided in an active distance measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing an IRED and respective PSDs arranged on a focal plane of the light projecting lens of FIG. 1;
FIG. 3 is a diagram for explaining a structure of each PSD in FIG. 2 and a principle of canceling a subject contrast.
FIG. 4 is a block diagram showing a circuit configuration of an active distance measuring apparatus according to an embodiment of the present invention.
[Explanation of symbols]
10 Projection lens 12, 14 Receiving lens 16 IRED
18,20 PSD

Claims (1)

Includes a light projecting optical system including a light projecting element and a light projecting lens, a first semiconductor position detecting element as a light receiving element, and a first light receiving lens arranged at a predetermined base line distance from the light projecting optical system. A first light receiving optical system for distance measurement, and a second light receiving element disposed in a direction perpendicular to the base line length direction and having a length in the base line length direction smaller than that of the first semiconductor position detecting element. And a second light receiving optical system for contrast correction including a second light receiving lens having an aperture smaller than that of the first light receiving lens .
The ratio of the opening amount of the first light receiving lens to the length of the first semiconductor position detecting element in the base line length direction, the opening amount of the second light receiving lens, and the base line length of the second semiconductor position detecting element The ratio of the length in the direction is the same,
The sum of output signals from terminals F ₁ and F ₂ inside the first and second semiconductor position detecting elements and terminals N ₁ and N ₂ outside the first and second semiconductor position detecting elements. An active distance measuring apparatus characterized in that a signal independent of contrast is output according to a sum of output signals from the distance measuring apparatus.

Images