JPH028709A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To enable measurement of a distance to a short range without the enlargement of a distance measuring device by measuring a distance with three photodetectors utilizing adjacent photodetectors in addition to ordinary photodetectors in a short-range distance measurement. CONSTITUTION:In measurement of distance, light emitting devices LED 5-LED 1 are lighted sequentially to detect distancies of an object to AF5-AF1. In this case, as for the light emitting device LED 1, a distance is measured with SPC 1 and SPC 2 as photodetectors and as for the LED 2, a distance is measured with two photodetectors SPC 2 and SPC 3. In a short range, the measurement of distance is performed with sets SPC 4 and SPC 5 of the photodetectors again for the LED 3 so that an output ratio of the photodetectors is in a proportional range even for a short range to the object. This eliminates the need for the enlargement of the apparatus by adding other photodetectors for short- range distance measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a subject distance detection device in a camera.

2. Description of the Related Art Active distance measuring devices have traditionally been used as distance measuring devices for cameras. In this method, a parallel beam of light is emitted from a light source provided in the camera, and an image of the irradiation spot of the light beam on the subject is formed so as to span two light receiving elements placed on the sides of the light source. This method detects the distance to the subject based on the output ratio of these two light receiving elements.

When distance measurement is performed using this active method, the image of the spot on the subject formed by the light from the light-emitting element moves on the light-receiving surface depending on the distance, and the output ratio of the two light-receiving elements changes depending on the distance to the subject. The distance to the subject is measured based on the output ratio of the image, but since the distance range to the subject to be photographed is wide, the moving distance of the image is also large. Therefore, if an attempt is made to measure the distance of a subject from 0 to ω with the light-emitting element and light-receiving element fixed, the image may not be formed on the light-receiving element at a short distance. For example, FIG. 4A shows an example of a conventional distance measuring system. The image (2) formed by the reflected light from the subject of the light beam projected from the light emitting element LED is generated by the light receiving element 5PC1,
Since it moves on 5PCQ, 5PC2 due to the movement of the image.
and the output ratio of 5PC1 changes. This 5PC2/5PC
The relationship between the output of I and the distance is expressed by a relationship curve as shown in FIG. Since this ratio is constant regardless of the reflectance of the object, the distance to the object can be measured by measuring this ratio. However, as can be seen from Figure 4, when the subject distance becomes as short as 84.35 mag, the image ■ due to the reflected light from the subject shifts to the right and is hardly imaged on the 5PCI plane. , the image is focused only on 5PC2, the ratio of 5PC2/5PCI does not change with distance, and as shown in Figure 5, it becomes saturated and the distance resolution decreases, eventually making distance measurement impossible. occurs. This problem can be solved by adding another light receiving element 5PC3 as shown in Figure 4B.
If the distance cannot be determined with only 2, 5PC2 and 5PC
This can be solved by determining the distance using 3, but it is not desirable to do this only for extremely short distance measurements because it increases the size of the distance measuring device. On the other hand, a camera has been proposed that uses an active distance measuring method to measure distances in a plurality of areas of the object and focuses on an appropriate reference, for example, the closest area.

Problems to be Solved by the Invention The present invention is a distance measuring device that measures distances in multiple areas of a subject using an active method, and can measure the distance to a subject from close to far without increasing the size of the device. The objective is to measure with high accuracy over a wide area up to a distance.

20 Means for Solving Problems In an active type distance measuring device, an arrangement of a plurality of light emitting means for projecting light spots onto a plurality of distance measurement areas of a subject, and a method of arranging the light emitting means as described above are provided. A means for forming an image of a projected light spot, and a light receiving element on the image plane of the same means, which shares one light receiving element with an adjacent distance measuring area, and two light receiving elements are provided in each distance measuring area.
For each distance measurement area, the distance of the distance measurement area of the object is detected based on the position of the image of one of the light emitting spots on at least three adjacent light receiving elements. The object distance is detected by a calculation means.

E1 Effect As explained in the conventional example section, for one distance measurement area, two light-receiving elements are usually used, and on the two light-receiving elements, the position of the projected light spot image in the subject is determined. By determining whether a distance measurement area is formed, the distance to the distance measurement area can be determined. As the distance gets closer, the image of the projected light spot will change to the above 2.
Since the light receiving element is formed only on one of the two light receiving elements and deviates outward from the light receiving element, it is necessary to add one more light receiving element for short range distance measurement.

In the present invention, in order to perform distance measurement for each of a plurality of distance measurement areas, two light receiving elements are provided for each area.

Of these two, - pieces are common to the adjacent distance measurement areas, so the number of light receiving elements is at least the number of distance measurement areas plus one. This is the minimum number necessary, but since the photodetectors are arranged in this way, even at short distances where the distance cannot be detected with just two photodetectors matched to one distance measurement area, the two photodetectors can be used. Distance can be determined using an adjacent light receiving element, and there is no need to add a special light receiving element for short distance measurement.

Embodiment FIG. 1 shows a schematic configuration of a distance measuring system in this embodiment. The figure shows the five ranging areas (A) on the screen shown in Figure 3.
This is intended to perform distance measurement of a subject at F1 to AF5).

In FIG. 1, LEDI to LED5 are light emitting elements, which are arranged in a line perpendicular to the optical axis of the camera, and el is arranged so that the focal plane is located on the row of these light emitting elements. ~A lens that projects the image of the LED 5 onto the subject. AFI to AF5 are the images of these light emitting elements on the subject, and the range of these images becomes the distance measurement area in the subject field. An image of the light emitting element on the subject, that is, an irradiation spot is formed by the lens e2 on the array of light receiving elements 5PCI to 5PC6. For example, the shaded part A in the figure is the image of the image of the light emitting element LED1 on the subject by the lens e2,
In the figure, it is formed across 5PCI and 5PC2. Distance measurement using these two sets of adjacent light receiving elements is the same as in the conventional active method, and thereby distance measurement is performed at five locations on the photographic screen. In this example, 5
The closest distance is selected from the distance measurement results for each location and the camera is focused on it, but it is up to you how you use the multiple distance measurement results.

When measuring distance, the light emitting elements are turned on in sequence, and the light receiving element corresponding to the light emitting element that lights up performs distance measurement using 5PCI and 5PC2 for the light emitting element LED1, and the light emitting element LED
2, distance measurement is performed using 5PC2 and 5PC3. Similarly, LED3, LED4. Distance measurement is also performed for each of the LEDs 5 using two light receiving elements. The selection of the light receiving element set in the above case is a selection when the distance to the subject is long, but in this example, the short distance light receiving element set 5PC4 and 5PC5 is used again to measure the LED3. The distance is calculated so that the output ratio of the light receiving element is in the proportional range even when the distance to the subject is short.

FIG. 2 shows an outline of the circuit configuration of the distance measuring system according to the present invention. LEDI-LED5 is a light emitting element such as a light emitting diode as a light source. 5PCI to 5PC6 are light receiving elements. Tr2 to Tr6 are driving transistors that light the light emitting elements LEDL to LED5, and MPXl is the light emitting element LEDI.
This is a multiplexer for sequentially lighting up the LEDs 5. MPX2. MPX3 is also a multiplexer, MPX2
Input terminals a, b, c, d, e have light receiving elements 5PC1~
A signal obtained by logarithmically transforming the output of 5PC5 is input. MP
In X3, excluding the light receiving element 5PCI, the logarithmically converted output of 5PC2 is input to the top input terminal a゛, and the logarithmically converted signals of the outputs of 5PC2 to 5PC6 are input to the b゛ to e° input terminals. It is now entered into AN
C1 to ANC6 are logarithmic conversion amplifiers. A clock pulse from a control circuit (not shown) causes the multiplexer MPX to
The input terminals of MPX1 to MPX3 are sequentially selected synchronously, and at the timing when the light emitting element LED5 is lit, the input terminals of the multiplexers MPX2. M-PX3 output terminal a,
a' is selected, the logarithmically converted signals of the outputs of 5PCI and 5PC2 are input to the differential amplifier DIF, and the difference between the two signals is output. Since this difference signal is a logarithmic difference, it is the ratio of the outputs of the light receiving elements 5PCI and 5PC2, and this signal is input to the comparators c1 to c8. A reference voltage obtained from each point on a voltage dividing resistor R by passing a constant current is applied to each of the comparators c1 to c8, and the output of the differential amplifier DIF is ranked into eight levels.

This operation sequentially causes LED4. This is done by lighting up LED3 to LEDI, and the distance of the subject from AF5 to AFL in FIG. 1 is detected. After passing through the above operations, the control circuit drives the multiplexer MPXI to the low level again.
Multiplexer MPX2 that lights up ED3. Input terminal d of MPX3.

do, and in the same manner as above, set the light receiving elements 5PC4 and 5PC4.
The output ratio of PC5 is classified into ranks and extracted. In other words, A
After performing distance measurement for each area of F1 to AF5,
Close-range distance measurement is being performed again for AF3 in the center. When the outputs of the comparators c1 to c8 are all at high level, the control circuit determines that distance measurement is not possible at short distances, and in other cases, it detects the distance depending on how many comparators have outputs at high level. There is. The feature of this embodiment is that the distance measurement operation is repeated twice.In the first operation, the distances of each part of AFI to AF5 on the subject are measured in Fig. 1, and in the second operation, the central part AF3 is again Measurements are made using a photodetector. If the distance at the center has been determined by the first operation, the second operation is not necessary, but depending on whether the distance at the center has been determined by the first operation or not, the second operation may be necessary.
It is easier to program a program by randomly performing an action twice than by deciding whether to perform the action the second time.

Further, in this embodiment, the measurement in the case of short distance is performed only for the center of the screen, but it goes without saying that this may be performed for each area. For example, in the case of a short distance for the area AF1, the distance is detected using the ratio of the outputs of the light receiving elements 5PC2 and 5PC3.

In Fig. 2, MPXI uses a signal OT1 [signal 1 corresponding to the ranging areas AF1 to AF5] from the microcomputer controlling the ranging device to control the ranging area AP and the LEDs that emit light as shown in Table 1 below. A multiplexer outputs an rH and level signal to any one of output terminals 1 to 5 as selected. MPX2. MPX3 is a multiplexer that selects one of the signals input from each SPC and outputs it to the differential amplifier DIF so that the relationship between the ranging area AF and the light receiving element SPC shown in Table 1 is established using the signal OTI from the microcomputer μC. It is. c2 is a capacitor for supplying energy to the light emitting element LED. ANI-
AN5 and Tr1 to Tr6 are AND circuits and transistors for causing the light emitting elements LEDI to LED5 corresponding to the ranging areas AFI to AF5 to emit light in response to the signal rH from the MPX1 and the ranging start signal AFS. AN01
~ANC6 is a detection signal of the light from the light emitting element reflected from the subject, and is output as a logarithmically compressed signal to the multiplexer MPX2.
This is an analog circuit that outputs to MPX3. Differential amplifier D
IF is multiplexer MPX2. This is a circuit that takes the difference between the outputs from M1'X3 (it takes the difference between logarithmically compressed signals, so it essentially takes the ratio of the output signals of the light receiving elements).

01 to c8 are comparators for detecting the output level of the differential amplifier, and the latch circuit connected to this is controlled by the signal of the circuit (delay) that provides the AF start signal.
The output of the comparator is latched, and the selection circuit CHI~CH
Output to 8. The reference voltages of the comparators c1 to c8 are formed by a well-known constant current element 11 and a voltage dividing resistor.

In this application, the distance measuring system includes five light emitting elements LEDI to LED5 and six light receiving elements 5PCI to 5PC, as shown in FIG.
It consists of 6. Table 1 below shows the relationship between the combinations of these light emitting elements LED and light receiving elements SPC and distance measurement areas.

Table (OTI) signal compatible table distance measurement area LED SPCOTI signal AFI LE
DI 5PCI (a) 0HSPC2(a'
) AF2 LED2SPC2(b) lN5PC
3(b') AF3 LED3 5PC3(c) 2H3P
C4(c') AF4 LED4 5PC4(d) 3H3P
C5(d') AF5 LED5 5PC5(e) 4H3P
C6(e') AF3 LED3 5PC4(d) 5H3PC
5(e') In the second distance measurement in the distance measurement area AF3, LED3 is used as the light emitting element, but unlike the first distance measurement in the distance measurement area AF3, the light receiving element has a baseline length of <5PC4, 5pcs
5 is used to measure closer distances.

The distance measurement operation will be explained. Based on the control signal sent from the OTI terminal of the microcomputer, distance measurement is performed from AFL to AF5 using combinations corresponding to Table 1 above. The detection signals of each light receiving element SPC obtained in each ranging area are logarithmically compressed and differentially amplified! The difference between the two detection values logarithmically compressed using DIF (ie, the ratio of detection outputs) is calculated, and the calculated value is sent to the microcomputer and stored. The closest distance value is extracted from the stored distance measurement values, and a focusing operation is performed using that value. In distance measurement in the distance measurement area AF3, the light receiving elements SP4, 5PC5 are insufficient, and when it is desired to measure someone at a closer distance, the light receiving elements 5PC5 and 5PC6 may be used.

(Effects of the Invention) According to the present invention, in a distance measuring device that performs multi-point distance measurement using an active method in a camera, when short-range distance measurement is performed for one distance measurement area, the normal distance range of that distance measurement area is In addition to the photodetector used, a photodetector for distance detection in the adjacent area is used, so there is no need to add a separate photodetector for short-range distance measurement, and it is possible to measure short distances without increasing the size of the distance-measuring device. becomes.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the arrangement of the light emitting element LED and the light receiving element SPC, Fig. 2 is a circuit diagram of the distance measuring circuit AF, Fig. 3 is an explanatory diagram of the ranging area, and Fig. 4 is an explanation of distance measuring in the conventional example. FIG. 5 is a diagram showing the relationship between distance measurement and signal ratio according to a conventional example. AFL to AF5... Distance measurement area, el, e2... Lens, LED-LED5... Light emitting element, 5PC1 to 5P
C6... Light receiving element, ANCI to ANC6... Logarithmic conversion amplifier, MPXl, MPX2. MPX3...Multiplexer, DIF...Differential amplifier, R...Voltage dividing resistor, cl-c8...Comparator. Agent: Hiroshi Agata, Patent Attorney, Illustration 13

Claims (1)

[Claims] an array of a plurality of light emitting means for projecting light spots onto a plurality of ranging areas of a subject, means for forming an image of the light projection spot on the side of the light emitting means array, and an image plane of the light emitting means; A light-receiving element array in which one light-receiving element is shared with an adjacent distance-measuring area, and two light-receiving elements are arranged corresponding to each distance-measuring area, and at least three adjacent ones for one distance-measuring area. A distance measuring device comprising calculation means for detecting the distance of the distance measuring area of the object field based on the position of the image of one of the light projection spots on the two light receiving elements.