JPH01240812A - Range finder - Google Patents

Abstract

PURPOSE:To expand a distance measuring range by disposing three or more light-sensing elements adjacently to each other and by making the distance measuring range shared by two or more sets of distance measuring computation outputs obtained by computation from two light-sensing regions facing each other on the boundary. CONSTITUTION:Four silicon photodiodes (SPD) 1A-1D are provided as light- sensing elements. The boundaries of the adjacent ones of the SPD 1A-1D are set in the directions vertical to the direction of the length of a base line. A light flux emitted from a light-emitting element 20 is projected through a projec tion lens 26 to an object 28 to be measured on a distance, and a reflected light therefrom is made to enter the SPD 1A-1D through a light-sensing lens 27. Outputs of the SPD 1A-1D are supplied to an arithmetic means 29 and subjected to distance measuring computation.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a distance measuring device used in a camera or the like, and more specifically, to a distance measuring device used in a camera, etc. The present invention relates to a light irradiation triangulation type distance measuring device that measures all distances by receiving light with a light receiving section disposed a predetermined baseline length apart from a light transmitting section.

[Prior Art] The above-mentioned light irradiation type triangular 0+distance type distance measuring device is already well known, and various types have been provided in the past.

For example, the distance measuring device described in Japanese Patent Application Laid-Open No. 57-104809 has a pattern of projecting light from a light emitting element 80 toward an object 86 through a projecting lens 83, as shown in FIG. 6(A). 85, and the reflected light from the distance measuring object 86 is made incident on the light receiving elements 81 and 82 by the light receiving lens 84, and the distance is measured according to the output state of the light receiving probes 81 and 82. . The light emitting element 80 and the light receiving element 8
1°82 are arranged at predetermined positions on the Lll- substrate 87, as shown in FIG. 6(B). That is,
A light emitting element 80 surrounded by an electrode part 80a is placed near one edge of the substrate 87, and two light receiving elements 8 are placed near the other edge.
1.82 and the light receiving elements are fixed close to each other so that the boundary lines between the light receiving elements are perpendicular to the base line length direction 88.

In the A11l range device configured in this way, the positions of the eight reflected light images formed on the base line length direction 88 of the light receiving surface change according to the distance to the object to be ranged based on the principle of triangulation. Since there is a difference between the area where the light receiving element 81 receives light and the area where the light receiving cable 82 receives light depending on the position of the reflected light image 89, the distance to the object can be determined by the difference in output between the two light receiving elements 81 and 82. can be detected.

FIG. 7(A) shows the 41 distance device shown in FIGS. 6(A) and 6(B) above. In the arrangement of the '1111 distance optical system, a light emitting element 'T-80 with a chip size of t is placed at a distance from the projection lens 83 by its focal length, 4f. The focal length f of the light-receiving lens 84, which is placed a baseline length apart from the light-emitting lens 83, and the photocurrent 1. The object distance 4a to the distance measuring object 86 is determined by I. In addition, Fig. 7 (B) to (E
) shows how the reflected light images move according to the distance to the object to be measured, and 8 reflected light images with outer diameter tJ are 1
1111 distanceThe light receiving element 81.8 corresponds to the distance to the object.
2, the photocurrent 11.82 output from the light receiving cable 81.82. The distance measurement calculation output ■2/(■1+12) obtained by processing I2 changes from 1 to 0 depending on the subject distance, as shown in FIG. 7(F). This range of change from 1 to 0 is exactly the reflected light image 8
between two diameters t.

[Problems to be Solved by the Invention] However, in the conventional distance 41 setting device configured as described above, there arise fundamentally contradictory problems of improving the 71111 distance accuracy and expanding the Al11 distance range. . This will be explained below.

In the distance measuring device as described above, there is a relationship as shown in FIG. 8(A) between the reciprocal of the distance a to the subject and the distance measurement calculation output I2/(11+■2). That is, the solid line Ω1 in FIG. 8(A).
ρ2 is the projection chip size or t, t2 (t
t < t2), the relationship between the distance measurement calculation output 2/(11+12) and the reciprocal of the subject distance a is shown.

Generally, the amount of signal light incident on the light receiving element from the subject is very weak, so the signal current ratio I2/(11+12) is affected by circuit noise and the like. As shown in FIG. 8(B), the variation in the output signal caused by circuit noise, that is, the noise width, is the same noise width Δρ3. Δg4, distance measurement calculation output with added noise component! 2/(It + 12) is indicated by the shaded area.

Therefore, in order to judge the subject distance a1, the characteristic line Ω3 uses the judgment level Va, and the characteristic line Ω4 uses the judgment level v.
b will be used.

Then, due to the noise component, the range of uncertainty in distance determination is α for the characteristic line Ω3 and β for the characteristic line Ω4. In other words, when measuring distance using the characteristic line g4, the characteristic line g
Compared to case 3, the range of uncertainty in distance determination becomes wider and the fll11 distance accuracy is inferior.

Therefore, as an index representing the distance measurement accuracy of the distance measurement device, it can be evaluated by (noise width)/(slope of distance measurement calculation output). In other words, the distance measurement range S is the distance between the light projecting lens and the light emitting element. , and if the base line length and the chip size of one light emitting element are t, then -LS-■ ~ □. In addition, the distance measurement accuracy R is determined by the distance measurement calculation output noise N
Then, it becomes. As can be seen from the above equation, the Al11 distance range S becomes larger as the focal length fT+ base line length of the projecting lens becomes smaller, and when the chip size t of the light emitting element becomes larger as t2, the distance range S becomes larger as shown in FIG. ) As shown by the characteristic line Ω2, the closest side extends by fT-L/12, so the distance measurement range S becomes larger, but the distance accuracy R deteriorates on the contrary. On the contrary, the larger f,,L becomes, and the smaller t, the better the distance measurement accuracy R becomes or the smaller the distance measurement range S becomes. In other words, in such a distance measuring device, improving the distance measuring accuracy and expanding the distance measuring range are contradictory to each other.

In addition, in order to both improve distance measurement accuracy and expand the distance measurement range, there is a way to increase the amount of projected light and reduce the noise width of the distance measurement calculation output, or if it is incorporated into a small device such as a camera. Since there is limited space for the power source and the light emitting/receiving unit, and the power that can be supplied to the distance measuring device is also limited, the solution of increasing the amount of projected light is problematic in terms of cost and space. I can't hire you for some reason.

In addition, in order to expand the range of distance measurement, if measures are adopted such as increasing the chip size t of the light emitting element or decreasing the focal length fT of the light emitting lens, the object to be measured will usually be large, such as a person. Since the distance is limited, the projected light pattern may be larger than the object to be measured, making it difficult to accurately measure the distance.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a distance measuring device that can expand the range of distance measurement without reducing or even improving the accuracy of distance measurement.

[Means and Effects for Solving the Problems] The distance measuring device of the present invention includes a light projecting means for projecting light emitted from a light emitting element toward an object to be measured, and a light projecting section in the light projecting means. The sensor is arranged in a meandering manner along a predetermined base line from the base line, receives reflected light from the object to be measured, and has at least three adjacent light receiving elements, and the boundary line between each of the light receiving elements is perpendicular to the base line length direction. the light receiving means arranged so that and calculation means for calculating the distance to the object to be ranged based on the ratio of the amount of light received on one side of the two light receiving areas and the total amount of light received, the boundary being characterized by: The amount of light received in two light receiving areas divided by a line is determined for each of a plurality of boundary lines, and then the distance to the object to be ranged is detected.

[Example] Hereinafter, the present invention will be specifically described with reference to the drawings.

FIG. 1 is a diagram showing the arrangement of a distance measuring optical system of a distance measuring device showing an embodiment of the present invention, in which four 5PD (silicon photodiodes) IA, IB are used as light receiving elements.
, IC, and ID are provided. And each 5
The boundary line between PDIA and ID is set in a direction perpendicular to the baseline length direction. A feature of the present invention is that there are two or more boundary lines. In this embodiment, four SPDs are used, but any number of SPDs may be used as long as it is three or more. In FIG. 1, a light emitting element 20 with a chip size of t, which is disposed at a distance of a focal length p4fT from the light emitting lens 26, has a light beam emitted by the light emitting element 20, which is focused by the light emitting lens 26. The light is emitted and projected onto the object 28 at a distance of 71,111. Same l1
The light reflected by the object 28 at a distance of
The light is condensed by the light receiving lens 27, which is arranged a baseline length apart from the lens 27, and enters 5PDIA, IB, IC, and ID which are arranged at a focal length f from the lens 27. Then, each of the 5 PDIA, IB, IC, and ID has a photocurrent of 11. I2. I3. I4 is generated and supplied to the calculation means 29, where distance measurement calculation is performed.

FIG. 2 is an electrical circuit diagram of the distance measuring device of this embodiment, and FIG. 3 is a timing chart of signals supplied from the control circuit section 25 in FIG.

As shown in FIG. 2, this distance measuring device includes a light projection circuit section 21 that projects a first pulse onto an A+++ distance object, and a light projection circuit section 21 that receives reflected light from the distance object and detects a signal pulse photocurrent component. , photocurrent detection circuit units 22 to 22C for amplification, calculation output circuit units 23 to 23B for obtaining distance information of the subject from the photocurrent superimposed on the bias current, and outputs of the calculation output circuit units 23 to 23B. Count circuit section 2 for A/D conversion
4, and a control circuit section 2 that sends control signals to each of the above circuit sections.
It consists of 5.

The photocurrent detection circuit section 22.22A, 22B.

22C use the same constituent members and have a similar configuration, so only the circuit section 22 will be explained.
For the circuit components 22A, 22B, and 22C, A, B, and C are simply attached to the same members, and repeated explanations will be omitted. In addition, calculation output circuit sections 23.23A, 23B
The same shall apply to

In FIG. 2, an IRED (infrared light emitting diode) 68 of the light projecting circuit section 21 is composed of a transistor 67° and a resistor 66.6.
9 and an operational amplifier 65, it is driven at a constant current. The base of a transistor 70 that controls on/off of this constant current drive circuit is connected to the terminal T1 of the control circuit section 25 via a resistor 71, and the pulse waveform shown in FIG. 3 is projected from this I RED 68. Control circuit section 2 controls on/off of the infrared light.
This is done by the output signal of terminal T1 of No. 5 (see FIG. 3).

The photocurrent detection circuit section 22 includes an operational amplifier 3. Preamplifier circuit section consisting of transistor 2 and operational amplifier 5. It consists of a background light removal circuit section consisting of a transistor 4 and its peripheral circuitry, and a current mirror circuit consisting of transistors 8, 9, and 10.degree.12. A signal pulse photocurrent (1) obtained from the anode of the 5PDIA is supplied to an operational amplifier 3 constituting a preamplifier circuit section. This operational amplifier 3 has its output terminal connected to the emitter of the transistor 2, its inverting input terminal connected to the base, and its non-inverting input terminal connected to the reference power supply V ref so that feedback is applied by the transistor 2. The base input resistance of the transistor 2 is isometrically reduced to about several 10KΩ.

The operational amplifier 5 constituting the background light removal circuit section becomes active when turned on by the "H" level of the output signal of the terminal T1 of the control circuit section 25 being applied to the base of the transistor 6 through the resistor 73 when no light is emitted. The capacitor 7 connected to the output terminal accumulates a charge corresponding to the brightness of this background light, and a feedback loop consisting of the capacitor 7 and the transistor 4
The charge current component due to the background light of the PDIA and the bias current component of the operational amplifier 3 are discharged to the ground line as the collector current of the transistor 4. As a result, the collector current of transistor 2 is independent of the magnitude of the background light.
The value approximately corresponds to the pulse signal photocurrent. When light is emitted, the operational amplifier 5 becomes non-active because the transistor 6 is turned off, but due to the charge accumulated in the capacitor 7, the transistor 4 continues to discharge the photocurrent due to the background light to the ground line, so that the photocurrent is obtained from the anode of the 5PDIA. The pulsed light component obtained by subtracting the photocurrent due to the background light from the photocurrent is multiplied by β in the transistor 2 and sent to the current mirror circuit 8.
9. 10. 12, and the signal pulse photocurrent βN is transmitted to the compression diode 46 of the calculation output circuit section 23.
Injected as I.

In addition, the photocurrents obtained from each anode of the other 5 PDIBs, IC, and ID 11. I is also a photocurrent detection circuit section 22A that operates in the same way as the 2'' 34 circuit section 22 described above.
, 22B, and 22C, respectively, and the signal pulse photocurrent βNI/3N■3. β2. I4 and 2' are supplied to the calculation output circuit sections 23.23A and 23B.

The calculation output circuit section 23 includes a transistor 41°42.44
．． 45, compression diodes 46, 47, constant current source 43, and buffer circuits BUF, , BUF2, lp
It constitutes a logarithmic expansion circuit for outputting 1-distance calculations. The bases of the transistors 41 and 42 forming the differential amplifier are connected to the anodes of the compression diodes 46 and 47 via buffer amplifiers BUF and BUF2, and the emitters of the transistors 41 and 42 are commonly connected to the constant current source 43. ing.

The collector of transistor 42 is connected to the bases of transistors 44, 45 forming a current mirror circuit and to the collector of transistor 44.

By the way, the currents II flowing through the diodes 46 and 47 are combined with the signal pulse photocurrents outputted from the photocurrent detection circuit section lb' 2b 22, and the circuits are connected so that the sum thereof flows. Therefore, in the arithmetic output circuit section 23, the above-mentioned current 11b is only the signal pulse photocurrent βNI from the photocurrent detection circuit section 22, but the current '2b is only the signal pulse photocurrent βNI from the photocurrent detection circuit section 22A, 22B, 2
Signal pulse photocurrent βNl + βNI from 2C
, β, and I4.

Therefore, if the constant current of the constant current source 43 is I, the collector current Ic of the transistor 42 becomes as follows. Therefore, the collector current 11' of the transistor 45, which is the output of the arithmetic output circuit section 23, is obtained by substituting the above equation (1) into the equation (2). Similarly, in the calculation output circuit section 23A, the current l1
Since bA is the sum of signal pulse photocurrents βNI and βNI2 from the photocurrent detection circuit sections 22 and 22A, and current l2bA is the sum of signal pulse photocurrents βNl and βNI4 from the photocurrent detection circuit sections 22B and 22C, becomes. In addition, in the calculation output circuit section 23B, the current 'lb
B is the sum of the signal pulse photocurrent βNl + βNI2°βNI from the photocurrent detection circuit sections 22, 22A and 22B, and the current l2br3 is the sum of the signal pulse photocurrent βNI4 from the photocurrent detection circuit section 22C, so the following equation is obtained. Therefore, the output current 12' from the second arithmetic output circuit section 23A is obtained by substituting the above equation (4) into the equation (2). Further, the output current 3' from the third arithmetic output circuit section 23B is obtained by substituting the above equation (5) into the equation (2).

Above 1st. Second. Third calculation output circuit section 23° 23A,
The output currents I', I2', and I3' of the 23B range from infinity to close range, depending on the reciprocal of the subject distance a, as shown in Fig. 4 (A), (B), and (C).
1111 distance ranges are shared for distance measurement, and when these are combined, a comprehensive characteristic diagram of distance measurement is obtained as shown in FIG. 4(D). In this Figure 4 (D), there is a possibility that a step may occur at the connection points J, J2, but this is because
By appropriately selecting the size of the light receiving spot image and the SPD, it is possible to prevent an excessively large level difference. In terms of the circuit, there are three calculation output circuit sections 23 at the connection point P1.
．． A wired OR is established between each output terminal of 23A and 23B.

In the manner described above, the distance to the subject can be determined from the combined sum of the output currents of the three calculation output circuit units.

On the other hand, the count circuit section 24 includes transistors 45.45A and 4 of the calculation output circuit sections 23.23A and 23B.
Total sum of collector current of 5B I'+I''+
Ia' is measured digitally by a counter mechanism (not shown) built in the control circuit section 25.

The output currents of the arithmetic output circuit sections 23, 23A, and 23B are determined as follows.

The output current of the arithmetic output circuit section flows through the capacitor 52 each time light is emitted, and charges are accumulated in the capacitor 52. The operational amplifier 53 is for resetting the capacitor 52, and the base of the transistor 54 for controlling the operational amplifier 53 is connected to the terminal T3 of the control circuit section 25 via a resistor 76. Therefore, the output signal of this terminal T3 (see FIG. 3) turns on the transistor 54, sets the potential of the capacitor 52 to the reference voltage Vrcf, and turns it off immediately before the start of light emission, making the operational amplifier 53 inoperable. do. Thereafter, the potential of the capacitor 52 increases due to the current injected into the capacitor 52.

When the light has been emitted a predetermined number of times, as shown in the timing chart in Figure 3, the terminal T4 becomes H-L, so resistor 7
7, transistor 63 is turned off, and transistor 5
5, the capacitor 52 is discharged. At the same time, a counter built in the control circuit section 25 operates and continues counting until the output of the comparator 62 becomes H. Comparator 6
2, the voltage across the capacitor 52 is the reference voltage V rel
'When it becomes smaller, it changes from L to H. The discharge rate of the capacitor 52 is determined by a current mirror circuit consisting of a constant current source 61 and transistors 56 and 55 connected in series thereto. In this way, an output corresponding to the object distance can be obtained as the count value of the counter in the control circuit 25.

FIG. 5 shows another circuit example of the /7A calculation output circuit section 23. According to this circuit example, the subject distance is determined by the ratio of the difference between the received light "Ib" 2b of the two light receiving areas and the total amount of received light (I -1
) / (11b+l2b) lb
2b It is possible.

A detailed explanation of the circuit shown in FIG. 5 and its operation is disclosed in Japanese Patent Application No. 62-310689 (see Japanese Unexamined Patent Application Publication No. 1988) previously filed by the applicant, so a brief explanation will be given here. .

In FIG. 5, transistor 1 of a differential amplifier is composed of transistors 121 to 124 and a constant current source 129.
22. The first current I mentioned above and the second
The current I2b is supplied respectively. Since transistors 121 and 125 constitute a current mirror circuit, and similarly transistors 123 and 127 also constitute a current mirror circuit, the current flowing through transistors 125 and 126 is equal to the current flowing through transistor 122, and the current flowing through transistors 127 and 128 is equal to the current flowing through transistor 122. The current flowing through transistor 124 is equal to the current flowing through transistor 124. Therefore, the calculation output from the collector of the transistor 128 of the differential amplifier composed of the transistors 125 to 128 is (1-1)/(I, b+125) lb 2b . In addition, 11. IIA is a compression diode, BUF
, BUF4 is a buffer amplifier.

[Effects of the Invention] As described above, according to the present invention, at least three or more light-receiving elements are arranged adjacently, and two or more sets of light-receiving areas calculated from two light-receiving areas facing each other with a boundary between them are arranged adjacently. Since distance measurement is performed by dividing the distance measurement range using the distance measurement calculation output and combining them in a circuit, the slope of the distance measurement calculation output characteristic g1 with respect to the reciprocal of the subject distance shown in FIG. 8 (A), that is, the distance measurement It is possible to have a 411 distance range of the characteristic line Ω2 while maintaining accuracy.

With this configuration, not only is the structure simple, but it is also compact and can be used in small devices such as cameras without using large power batteries to increase the light emitting energy of the light emitting element. Suitable for built-in use, reducing camera distance measurement accuracy. Improve without any problems, and lt
'll distance range can be expanded. In particular, when the object to be measured is relatively far away and small like a person, the projected light image only partially hits the object at a distance of d
However, in the present invention, there is no need to enlarge the projected light image, so the #1pj distance accuracy 0 deterioration as described above does not occur, and sufficient distance measurement accuracy can always be maintained. It has the effect of being able to be maintained.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of a distance measuring optical system in a distance measuring device showing an embodiment of the present invention, FIG. 2 is an electric circuit diagram of the distance measuring device shown in FIG. 1, and FIG. The timing chart of the signals of the control circuit section in FIG. 2, and FIGS. Figure 4 (D) shows these (A),
Figure 5 is a diagram when (B) and (C) are added to form one characteristic line, and Figure 5 is an electric circuit diagram showing another circuit example of the arithmetic output circuit section in Figure 2 above. (A) and (B) are a perspective view and a front view showing the arrangement of the ranging optical system of a conventional distance measuring device, and FIG. 7(A) is a diagram showing the arrangement of the ranging optical system of a conventional distance measuring device. In the plan view shown in Fig. 7 (B), (C), (
D). (E) is an explanatory diagram showing how the reflected image from the object to be measured is formed on the light-receiving element group in accordance with the object distance;
In Fig. 7 (F), the center position of the received and reflected image is shown in (B),
Figure 8 (^) is a characteristic diagram of the calculation output I / (I, +1.,) when the position corresponds to (C), (D), (E). Characteristic diagram showing the relationship between distance measurement calculation output ■2/(■1+12) with respect to the reciprocal of distance, Figure 8 (
B) is a characteristic diagram when noise is superimposed on the diagram shown in FIG. 8(A).

Claims (1)

[Claims] (1) A light projecting means for projecting light emitted from a light emitting element toward a distance measuring object; and a light projecting means arranged a predetermined baseline length away from the light projecting section of the light projecting means, and a light projecting means for projecting light emitted from a light emitting element toward a distance measuring object; a light-receiving means that receives reflected light and has at least three or more light-receiving elements adjacent to each other, the boundary line between each of the light-receiving elements being arranged perpendicular to the base line length direction; two divided by one
The ratio of the amount of light received on one side of the two light-receiving areas to the total amount of light received, and the two divided by a boundary line that is different from one of the boundaries above.
1. A distance measuring device comprising: a calculation means for calculating a distance to an object to be measured based on the ratio of the amount of light received on one side of the two light receiving areas to the total amount of received light.