JPS58190710A - Range finder - Google Patents

Abstract

PURPOSE:To provide a range finder incorporating, in place of conventional logarithmic amplifier circuit, a linear amplifier circuit having superior signal to noise ratio and resolution, by making use of a light-receiving element the input/ output characteristics of which vary depending on the position of incidence of light. CONSTITUTION:An SPD10 has a deformed light-receiving pattern 11 so that the rate of change of light-receiving sensitivity thereof varies in accordance with the shape of the pattern 11. The reflected light image 8 of a closer object 3 is within a part of low light-receiving sensitivity of the SPD10, while the reflected light image 7 of a remoter object 4 is in the part of high light-receiving sensitivity of the SPD10. The quantity of the reflected light is in inverse proportion to the distance to the object, so that it becomes possible to reduce the amount of change of the output current from SPD10 by forming the light-receiving pattern 11 in a shape corresponding to the expected amount of change of the reflected light quantity. It is, therefore, possible to use a linear amplifier circuit which is superior to the logarithmic amplifier circuit in the aspects of the signal to noise ratio and resolution, even with a power source of a comparatively low voltage.

Description

[Detailed description of the invention] The present invention irradiates light from a projector toward an object.

A telescope that measures the distance to an object by receiving light reflected from it. In particular, it relates to improvements in the light-receiving element.

Conventionally, there was a device for this purpose as shown in Figure 1.

In the figure, there is a light nine body (hereinafter referred to as LEI), which looks like a light-emitting diode outside Q month (abbreviated as 1-ru) (February LED (1)).
Power is distributed to the aperture surface of the condenser lens, iJ and (4
) is the object to be measured that is irradiated with light by IJD (r),
(5) is a condensing lens that rotates the objects to be measured (3) and (4), and (6) is a condensing lens (a light receiving element such as a γ-reconverter photodiode placed on the other side of 5). (hereinafter abbreviated as bf'D), (force is the image of the object to be measured (4) formed on the light receiving element (6), (8) is the image of the object to be measured (4) formed on the light receiving element (6)? In the image (3), (9) is a logarithmic compression amplifier circuit connected to the light receiving element (6).

I will explain about the creation soon. The light emitted by LEIJ (υ) is emitted by the light beam, and the object to be measured (3 or (4)
) to form an irradiation surface. Board? St! 1 object (3)
(The irradiation direction on the top is the condensing lens (5) and the 8PD
The image is formed at position (8) or (7) on table ml of (s). The output current of 5P1) (6) is amplified by the logarithmic compression amplifier circuit (9), and the output current of SFD (6) is amplified by a logarithmic compression amplifier circuit (9).
>The distance is measured by detecting the position above. The logarithmic compression amplifier circuit (9) is used in response to the fact that the amount of reflected light from an object has a very large change. The amount of light reflected from an object is approximately inversely proportional to the square of the distance from the object, and if other factors are included, the change is approximately 1000 times. Therefore, the electric circuit that amplifies the output of the photodetector must be powered by a low-voltage power supply. It required a logarithmic pressure circuit to operate. However, logarithmic compression amplification circuits are disadvantageous in terms of signal to noise when amplifying minute signal currents compared to linear amplification circuits, and also have the disadvantage that their resolution is worse than that of linear amplification circuits. Conventional distance measuring devices were constructed as described above, and therefore required a logarithmic compression amplifier circuit, which had drawbacks such as deterioration of signal-to-noise ratio (1) resolution.

This invention was made to eliminate the above-mentioned drawbacks of the conventional method, and by improving the structure of the BPD, it does not use the logarithmic amplification N-path.

A distance measuring device that can use a convenient linear amplification circuit?
is intended to provide.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Second
In the figure, Ca H is 5 PIJ chip (B) is 5 PDaQ
It is a diffusing part that suppresses the light sensitivity that is configured with a slam on the top. In Figure 8, (1) is LED, <2) is LE
D (1) The front lens is arranged in this way, (3) and (4) are objects illuminated by light from LED <i),
(5) is the Glory lens that measures the objects to be measured (3) and (4> tm, &I is the Glory lens placed behind the Glory lens (5), and <n is the object imaged on the SPD Ql. (
4), (8) is an image of the object to be measured (3) formed on the light-receiving element α1, and 0 is a linear amplifier circuit connected to the light-receiving element.

Next, the operation will be explained. Since the 8PD ulJ has a cut-out light-receiving button (b), the light-receiving degree is very accurate in the direction of arrow A, and the ashing rate of the light-receiving sensitivity is determined by the shape of the pattern Oυ. This beautiful transformation slam (b)
If 8F1) (2) equipped with
The position is in the low part of the light receiving 1s trap on 8PDgq, and the reflection structure (7) of the distant object (4) is in the part with high light receiving sensitivity on spngg. Generally, the amount of reflected light is approximately inversely proportional to the square of the object distance.

The amount of reflected light that falls on a short-distance object (3) is the same as that of a long-distance object (4).
However, as a result of being limited by the light receiving panel of 5PDQ(J),
(The change in the output of l will be small. Since the change in the amount of reflected light depending on the distance can be predicted in advance by calculation and experiment, the light receiving batt (ro ), and further developed 81'D QO.
It becomes possible to reduce the change in the output torque Nj of 6
If the amount of change in the output current of 8FDαQ becomes smaller, it becomes possible to use a linear amplifier circuit that is superior to a logarithmic compression amplifier circuit in terms of signal-to-noise ratio Pk performance of 9 minutes even with a low-voltage power supply, and it becomes possible to use a linear amplifier circuit that is superior to a logarithmic compression amplifier circuit even with a low voltage power supply. It is possible to improve the accuracy and expand the range of reach for distant objects. FIG. 4 shows another embodiment. A plurality of independent light receiving parts (2) on the 8FD chip OQ, o4. There may be 71 BPD columns including (2) and (to), and the same effect as in the above embodiment can be obtained. FIG. 5 shows another embodiment. MPD
An F3PD may be used, which is provided with a light-receiving button a'h having a small sensitivity difference in the direction of arrow B on the chip CIQ, and has the same effect as the above embodiment. FIG. 6 shows another embodiment.

8PI) A light-receiving button having a shape having a benevolent functional relationship in the direction of arrow C may be formed on the chip OCI, and the same effect as in the above embodiment can be obtained.

In the above embodiment, the light receiving buttons (B), (To), DI,
Q5゜M, 02), a & was created by referring to diffusion, but light shielding with vapor-deposited metal, pine resin, etc. may be used instead of diffusion. In addition, in the above embodiment, the case of a pattern on a 8PI) chip was explained, but in 8, even if the effect is due to processing outside the D chip, it is a partial preemptive restriction that impairs the processing outside the bPD chip. However, the same effects as in the above embodiment can be achieved. In addition, in the above actual examples, the case of the triangular side fence method was explained, but other methods may be used.
The same effect as in the above embodiment can be obtained.

As described above, according to the present invention, since the 8PD is configured in such a way that the output change is limited, the signal-to-noise ratio can be improved by one resolution by using a linear amplification circuit in the amplification path. This has the effect of providing a distance measuring device with a high #1 degree.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the principle of a conventional distance measuring device. FIG. 2 is a top view showing an example of the light-receiving surface pattern of 8PD which is a feature of the present invention, @S is a principle explanatory diagram showing an embodiment of the present invention, and FIGS. 4 and 5. FIG. 6 is a top view showing another example of the light-receiving surface pattern of the 8PD, which is a feature of the present invention. (1)...Light emitting element, (2)...Condensing lens, (3
)...object constant. (4)...Object to be measured, (5)...Condensing lens, (7
)...Reflection image, t8)...Reflection image, QQ...8P
D, Qυ... Light receiving part, (2)... Linear amplifier circuit,
Ql, a◆, ni), an, (b), (g)...light receiving portions In Figure 1, the same reference numerals indicate the same or equivalent parts. Agent Makoto Kuzuno - Figure 1 Figure 2 Figure 4 Figure 5 Figure 6 Procedural amendment (voluntary) 11 Ko I Kocho Palace 1 ・Display of bar r'+- Patent application 1987-0787
No. 58 No. 3 Supplement 11: Representative Hitoshi Katayama Department, 1 Agent 6, Subject of amendment (2) The specification is amended as follows. Figure 1 Figure 2 O Δ Figure 6 1θ

Claims (4)

[Claims] (1) In a distance measuring device that measures the distance to the measured object by detecting the light incident position on a light receiving element that receives reflected light from the measured object, the light receiving element changes in accordance with the light incident position. A distance measuring device characterized by having input/output characteristics. (2) The distance measuring device according to claim 1, wherein the light receiving element has an input/output characteristic having a specific functional relationship with respect to a light incident position. (3) The distance measuring device according to claim 1 or 2, wherein the light receiving element has different light receiving sensitivities depending on the light incident position. (4) The distance measuring device according to any one of claims 1 to 8, wherein a table ml pattern having photosensitivity of the light-receiving element changes in accordance with a light incident position.