JP3639585B2 - Ranging device - Google Patents

Description

  The present invention relates to a distance measuring device, and more particularly to a distance measuring device for a camera that projects distance measuring light onto a subject to obtain a distance to the subject.

Conventionally, a pair of light receiving means arranged with a light projecting means is provided, and the position of the reflected light from the subject is obtained from the output signals of the pair of light receiving means. A distance measuring device for obtaining the distance is known (see, for example, Patent Document 1, Patent Document 2, etc.).
JP-A-5-52558 Japanese Patent Publication No. 3-2245

  However, in this method, as the subject distance is closer, the reflected light from the subject is incident on the light receiving means from an oblique direction, so that the reflected light protrudes from the light receiving means and cannot be measured.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a distance measuring device that enables accurate distance measurement regardless of the subject distance.

That is, the present invention provides a pair of light receiving means arranged at a predetermined baseline length to detect the position of reflected signal light from a subject for distance measuring light, a light projecting lens, and a subject through the light projecting lens. Projecting the distance measuring light, a light projecting means disposed between the pair of light receiving means, a first calculation process for detecting a distance to the subject based on an output signal of the pair of light receiving means, Calculating means for executing a second calculation process for detecting a distance to the subject based on an output signal of one of the pair of light receiving means, and the light projecting means includes: When it is possible to shift in the baseline length direction around the optical axis, and the computing means can detect the reflected signal light from the subject simultaneously with the pair of light receiving means according to the shift range of the light projecting means Is the output signal of the pair of light receiving means. The distance to the subject is detected based on the output signal of the one light receiving means when only one of the pair of light receiving means can detect the reflected signal light from the subject. Is detected .

  According to the present invention, the features of each distance measurement principle can be utilized to the maximum without waste, and accurate distance measurement can be performed regardless of the subject distance.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing the concept of a distance measuring apparatus according to a first embodiment of the present invention. In the figure, a CPU 1 controls a light projecting unit 2 that is a means for projecting distance measuring light to a subject and a scanning unit 3 that scans the light projecting unit 2. Further, a light position detecting element (PSD) 5 is positioned behind the light receiving lens 4, and similarly, a PSD 7 is positioned behind the light receiving lens 6. The outputs of these PSDs 5 and 7 are input to the CPU 1 via the optical position detection circuits 8 and 9, respectively.

  In such a configuration, ranging light is projected from the light projecting unit 2 to a subject (not shown). At this time, the light projecting unit 2 is controlled and scanned by the CPU 1 via the scanning unit 3 so that the light projecting direction is changed. Thereby, distance measurement of each point in the screen becomes possible.

  The distance measuring light projected by the light projecting unit 2 is reflected on a subject (not shown) and connects the light spots on the PSDs 5 and 7 through the two light receiving lenses 4 and 6, respectively. Based on the output signals of these two PSDs 5 and 7, the light position detection circuits 8 and 9 calculate the incident position of the light spot. The subject distance is calculated by the CPU 1 based on the outputs of the light position detection circuits 8 and 9.

FIG. 2 shows the distance measuring principle of the distance measuring apparatus of the present invention. In the figure, reference numeral 10 denotes a distance measuring light spot projected on a subject, and light receiving lenses 4 and 6 are arranged at a distance L from the distance measuring light spot 10. The PSDs 5 and 7 are arranged behind the light receiving lenses 4 and 6. Further, if the distance between the light receiving lenses 4 and 6 and the PSDs 5 and 7 is f _J and the light spot positions on the PSDs 5 and 7 are x ₁ and x _{2 as} shown in the drawing with reference to the optical axis of each lens, the following relationship is obtained. The formula holds.

L: f _J = S ₁ : x ₁
L: f _J = S ₂ : x ₂
S ₁ = L · x ₁ / f _J (1)
S ₂ = L · x ₂ / f _J (2)
S = S ₁ + S ₂ = (L / f _J ) (x ₁ + x ₂ ) (3)
L = (S · f _J ) / (x ₁ + x ₂ ) (4)
Therefore, if x ₁ and x ₂ are detected by the PSDs 5 and 7, S and f _J are fixed values, and therefore the distance L can be obtained.

  Therefore, accurate distance measurement is possible regardless of the position of the distance measuring light spot 10.

  Next, a second embodiment in which the distance measuring apparatus of the present invention is applied to a camera will be described.

  FIG. 3 is a block diagram showing the configuration of the second embodiment of the present invention. In the first embodiment described above, the one-dimensional position detection type is used as the PSDs 5 and 7, but in this second embodiment, a mechanism of a type that scans the IRED two-dimensionally is adopted, and the PSD is also used. A device capable of two-dimensional position detection is used. Therefore, according to the embodiment, it is possible to deliver the light projection points (ranging light points) within the camera screen.

  First, the mechanism for scanning the IRED two-dimensionally will be described. The IRED 11 is driven and controlled by the CPU 1 via the IRED driver 12, and a light projection lens 13 is disposed in front of the IRED 11. The IRED 11 is attached to the IRED holding portion 14 and is slid along the guide rail 18 in the x direction in the drawing by a motor 16 and a feed screw 17 driven by a motor (M) driver 15. The IRED 11 and the IRED holding unit 14 are slid in the y-direction along the guide rail 23 together with the support unit 22 by a motor 20 and a feed screw 21 driven by a motor (M) driver 19.

  On the other hand, PSDs 5 and 7 capable of two-dimensional position detection are respectively arranged behind the light receiving lenses 4 and 6 that are separated by the base line length S. The output of PSD 5 is supplied to CPU 1 via optical position detection circuits 8a and 8b, and the output of PSD 7 is supplied to CPU 1 via optical position detection circuits 9a and 9b. Reference numeral 24 denotes a switch for inputting a distance measurement start timing, which is commonly used as a release switch.

  FIG. 4A is an external view showing an arrangement in which the distance measuring device shown in FIG. 3 is incorporated in a camera. In FIG. 4A, a release switch 24 is provided on the upper surface of the camera body 25. On the front surface of the camera, a photographic lens 26 is arranged at a substantially central portion thereof, and a window of a finder 27 and a light projecting lens 13 and light receiving lenses 4 and 6 of a distance measuring device are arranged as shown in the vicinity thereof. ing.

  In such a configuration, when the motor 16 is rotated by the M driver 15, the IRED holding portion 14 is slid along the guide rail 18 in the x direction by the feed screw 17. Further, the support portion 22 is movable along the guide rail 23, and the motor 20 driven by the M driver 19 rotates the feed screw 21, whereby the IRED 11 is scanned in the y direction. The CPU 1 causes the IRED 11 to emit light via the IRED driver 12 while controlling the M drivers 15 and 19 according to a predetermined sequence.

  The distance measuring light from the IRED 11 is projected onto a subject (not shown) by the light projecting lens 13. Since the distance measuring light is projected in a direction connecting the position of the IRED 11 and the principal point of the light projecting lens 13, each time the position of the IRED 11 moves in the x and y directions, it is shown in FIG. As described above, the distance measuring point 28 on the photograph screen (finder) changes two-dimensionally.

  On the other hand, the position of the reflected signal light from the subject incident on the PSDs 5 and 7 from the outputs of the two PSDs 5 and 7 from the outputs of the two PSDs 5 and 7 in synchronism with the light emission of the IRED 11, the optical position detection circuits 8a, 8b, Detected by 9a and 9b. The CPU 1 calculates the distance to the subject at each point in the screen from the outputs of the light position detection circuits 8a, 8b, 9a, 9b.

  Here, the optical position detection circuit of FIG. 3 will be described with reference to FIG.

Output currents i ₁ and i ₂ are output from both ends of the PSD 30, and NPN transistors constituting a differential arithmetic circuit together with the constant current source 37 via preamplifiers 31 and 32, compression diodes 33 and 34, and buffers 35 and 36, respectively. 38 and 39 are supplied to the base. The emitters of the transistors 38 and 39 are connected in common and connected to a constant current source 37. The collector of the transistor 39 is connected to the power source via the integrating capacitor 40 and is connected to the CPU 1 via the switch 41 and the terminal 42. A background light removal circuit 43 that removes the background light current is connected to the output of the PSD 30.

Now, it is assumed that the signal light is incident on the PSD 30 having the length t as shown in FIG. The two output currents i ₁ and i ₂ depend on the light positions x and t,
i ₁ / (i ₁ + i ₂ ) = x / t (5)
Satisfy the relationship.

However, PSD 30 has incident background light other than signal light, and i ₁ and i _{2 in} the above equation (5) cannot be obtained without removing this background light. Therefore, the background photocurrent removal circuit 43 is connected to the output of the PSD 30.

The signal photocurrents i ₁ and i ₂ are amplified β times by the preamplifiers 31 and 32 and flow to the compression diodes 33 and 34 as shown in FIG. The voltage generated in the compression diodes 33 and 34 is input to the differential arithmetic circuit by the buffers 35 and 36. The constant current source 30 controlled by the CPU 1 allows the current I ₀ to flow in synchronization with the emission of the IRED, that is, the incidence of the signal light. On the other hand, the integrating capacitor 40 is initialized by the switch 41 so that the potentials at both ends are equal to Vcc before the light emission of the IRED.

The switch 41 is turned off in synchronization with the light emission of the IRED.

With the circuit thus configured, the relationship between the output currents i ₁ and i ₂ of the PSD 30 and I _INT is
I _INT = (i ₁ / (i ₁ + i ₂ )) × I ₀
= (X / t) I ₀ (6)
It becomes. Since this current I _INT is integrated into the integrating capacitor 40 for a predetermined time, by detecting the voltage at the terminal 42, the CPU 1 can obtain the above equation (6).
x = t · I _INT / I ₀ (6) ′
The signal light incident position x can be calculated as follows.

  The optical position detection circuits 8a, 8b, 9a and 9b shown in FIG. 3 detect the position of light based on such a principle.

  Next, a method for obtaining the subject distance L from the signal light position on the PSD will be described with reference to FIG.

  In the example of FIG. 2 described above, the principle of distance measurement has been described for the one-dimensional projection scan in the x direction. Here, however, it corresponds to the two-dimensional projection scan in consideration of the change in the y direction of the distance measurement point. This is an example of AF. That is, when the angle θ formed by the optical axes of the light receiving lenses 4 and 6 and the distance measuring point in FIG. 6A is θ = 0, the above-described equation (4) described in FIG.

In FIG. 6A, from the above equation (4)
L ₁ = S · f _J / (x ₁ + x ₂ ) (7)
So,
L = L ₁ cos θ (8)
If θ is detected, it is clear that the subject distance L can be obtained from x ₁ and x ₂ together with the above equation (7).

  The distance measuring light projected from the light projecting lens 13 toward the subject 44 is provided with the light receiving lenses 4 and 6 as shown in FIG. When the y-direction is arranged so that the direction (x) connecting the principal points of the light-receiving lenses 4 and 6 and the y-direction perpendicular to the direction can be detected, as shown in FIG. Connect light spots on PSDs 5 and 7.

Assuming that the distance between the two pairs of light receiving lenses and the PSD is f _J , the position y ₁ of the light direction in the y direction with respect to the positions 45 and 46 on the PSD of the lens optical axis is between the above θ. The following relational expression is established.
tan θ = y ₁ / f _J (9)
From this relationship, the subject distance L can be calculated from the light spot positions in the x and y directions, x ₁ , x ₂ , and y _{1 as} follows.
L = (S · f _J / (x ₁ + x ₂ )) · cos (arctan (y ₁ / f _J ))
(10)
Therefore, as shown in FIG. 3, the CPU 1 and the optical position detection circuits 8a, 8b, 9a and 9b calculate x ₁ , x ₂ and y ₁ from the outputs of the two-dimensional PSDs 5 and ₇ , whereby the CPU 1 The subject distance can be obtained according to equation (10).

Note that the optical position detection circuit described in FIG. 5 is used. Although y ₁ can be detected by any PSD, here, the detection accuracy of y ₁ is increased assuming a flowchart as shown in FIG.

  Next, the scan AF operation of the distance measuring apparatus will be described with reference to the flowcharts of FIGS.

In FIG. 7, step S1 is a step of reversing the motors 19 and 20 of FIG. 3 to initialize the position of the IRED 11. At the same time, this position is set to M = 0 and N = 0. Next, in step S2, the first distance measurement coordinate in the y direction is determined. Then, in step S3, the number of points scanned ranging determines whether or not exceed M _1.

Here, still the number of points that are the distance measurement does not exceed the M _1, a predetermined amount scans IRED11 the x direction proceeds to step S4. In step S5, M is incremented, distance measurement is performed in step S6, and the process returns to step S3. Thus, at step S3 to S6, as referenced in FIG. 4 (b), the distance measurement of M ₁ place in the x direction are sequentially performed.

Thus, if it is determined in step S3 that a scan in the x direction has been performed, the process branches to step S7, which is to determine the next distance measurement y coordinate. Then, after N is incremented in step S8, it is determined in step S9 that the number of points subjected to scan distance measurement is N ₁ .

Here, if the number of scan-measured points does not exceed N ₁ , the process proceeds to step S10 to reset the position in the x direction. Then, at step S11, the value of M also return initialized to step S4, measuring a distance in the x direction M ₁ places previously described. This is repeated at step S9 to the range-finding in the y direction N ₁ place is completed. In step S12, the distance measurement result closest to the obtained distance measurement results L _{11 to} L _M1N1 is focused.

With this flowchart, as shown in FIG. 4B, M ₁ × N ₁ number of distance measuring points can be arranged in the photo screen.

  By the way, it is difficult to detect the light position in the x direction and the y direction at the same time with the two-dimensional PSD. Therefore, in this embodiment, the IRED is emitted twice, and the light position coordinate in the x direction and the light position coordinate in the y direction are detected each time. However, position detection circuits connected to different PSDs can be operated simultaneously.

  Therefore, in the distance measurement subroutine in step S6 of FIG. 7, it is clearly shown that the optical positions are detected from the PSDs 5 and 7 at the same timing as in steps S22 and S23 and steps S28 and S29. doing.

In FIG. 8, first, in step S21, the IRED 11 starts to emit light, and using the optical position detection circuits 8a, 8b, 9a, 9b, the signal light incident position x in the x direction at the same timing as in steps S22 and S23. _1, determine the x _2. Specifically, a voltage depending on the above equation (6) is generated and held in the integrating capacitors (40 in FIG. 5) of the optical position detection circuits 8a, 8b, 9a, 9b. In step S24, it is determined whether or not the integration to the integrating capacitor has been completed for a predetermined time. Here, after the integration is finished, the light emission of the IRED 11 is finished in step S25.

  Next, the IRED 11 is caused to emit light again, but in order to prevent light quantity deterioration due to a rise in the chip temperature of the IRED 11 due to continuous light emission, a predetermined time interval is set with a timer in step S26. In step S26, the CPU 1 reads the integrated voltage held by the integrating capacitor in steps S22 and S23 described above by A / D conversion.

Next, the IRED 11 is caused to emit light again in step S27, and the signal light incident positions y ₁₅ and y ₁₆ in the y direction are detected by the optical position detection circuits 8b and 9b in steps S28 and S29.

Similar to the detection in the x direction described above, when the integration for a predetermined time is completed in step S30, the process proceeds to step S31, and the light emission of the IRED 11 is terminated. Then, to read again the integration result at the step S32, the (6) 'signal light position y ₁₅ and y ₁₆ obtained by the method as described in formula, averaged as in step S33, to reduce the measurement error To. In step S34, the subject distance is calculated from the thus obtained y ₁ , x ₁ , and x ₂ using the arithmetic expression described in the above expression (10).

  In the flowchart described above, ranging is performed as shown in FIG. 9A. However, the present invention is not limited to this, and for example, ranging points may be changed as shown in FIG. 9B. According to the example shown in FIG. 9B, there is an advantage that the distance measurement time can be further shortened.

  With such a distance measuring device, as shown in FIG. 10, it is possible to correctly focus on the main subject 44 even in a scene where no subject exists at the point of the central portion 47 of the screen 27.

  As described above, according to the embodiment, it is possible to provide a camera with a simple configuration that can measure a plurality of points in a screen with high accuracy and high speed and easily take a correct focus photograph.

  Further, according to this embodiment, since the distance can be measured according to the equation (10) without any relation to the shading of the movable part of the IRED, there is no need for strict scanning position detection means. That is, when the IRED is initialized as in step S1 of the flowchart of FIG. 7, it is only necessary to appropriately detect the position, and the subsequent predetermined amount of scan may be controlled by the energization time of the motor. As in the case of scanning the light projecting portion with the conventional active type triangulation method using the base line length as the base line length, it does not require strict positioning.

  As shown in FIG. 11, the main subject 44 exists in the center of the screen, and if the subject is simply focused on the closest subject, the miscellaneous subject 48 is in focus and the main subject 44 is in focus. Since there are many scenes, the main subject selection flowchart may be considered in which only the distance measurement result at the center of the screen is treated specially. For example, when there is nobody at the center of the screen and there is only a landscape, the distance measurement result at the center of the screen shows an infinite value, so an algorithm that selects the closest distance only at this time can be considered.

  As described above, according to the present invention, the distance measurement result at the center of the screen can be selected without having a strict positioning means. This will be described as a third embodiment with reference to FIG.

  FIG. 12A is a front view showing an arrangement in which a distance measuring device is incorporated in a camera according to a third embodiment of the present invention. A release switch 24 is provided on the upper surface of the camera body 25. Further, on the front surface of the camera, a photographic lens 26 is provided at a substantially central portion thereof, and at the periphery thereof, a window of a finder 27, a light projecting lens 13 and light receiving lenses 4 and 6 of a distance measuring device, as illustrated. Has been placed.

  FIG. 12B is a conceptual view of the camera of FIG. In the figure, two light receiving lenses 4 and 6 are arranged side by side with respect to the finder objective lens 27. Here, if only the x coordinate is considered, the center of the camera screen is at the position 47 in the figure. However, if the y direction is not considered, the measurement unit obtained when the distance measuring light is projected at this point from the light projecting unit (not shown). The distance result can be said to be a distance measurement result centered on the screen.

Accordingly, when the x direction of the distance between the principal points of the finder objective lens 27 and the light receiving lens 4 is S _2x (see FIG. 4A), the signal light receiving position on the PSD 7 is determined from the distance f _J between the light receiving lens and the PSD. The following relationship is established between x ₁ and the distance L.

x ₂ = ((S + S _2x ) · f _J ) / L (11)
Although the signal position x ₁ on the PSD 5 may be used, generally, the longer base line is better, so x ₂ is used.

If only the y coordinate is considered, it is as shown in FIG. In the figure, if 13 is a light projecting lens, 11 is an IRED, and 27 is a finder objective lens, the reflected signal light incident from the subject at the center of the screen is transmitted to the y ₁ position of the PSD 7 via the light receiving lens 4. Connect the dots. At this time, the signal receiving position y _{1 in} the y direction on the PSD 7 establishes the following relationship with the distance L.

y ₁ = (S _2y · f _J ) / L (12)
Here, S ₂ indicates a y-direction component of the distance between the principal points of the lens 27 and the lens 4 as shown in FIG.

When S + S _2x = 30 mm, f _J = 20 mm, and S _2y = 30 mm, the equations (11) and (12) are
x ₂ · L = y ₁ · L = 600 mm ² (13)
It becomes.

FIG. 13 is a flowchart for explaining the operation of the third embodiment in which the distance measurement result L _MNO at the center of the screen is emphasized. In the flowchart of FIG. 13, steps S1 to S11 are the same as steps S1 to S11 of FIG.

In step S9, if the number N of points measured by scanning exceeds N ₁ , the process proceeds to step S13, and the obtained distance L _{MN is} obtained according to the principle described in the above equations (11) and (12). Then, the distance measurement result at the center of the screen is determined from the light incident position x ₂ and L ₁ at that time. The numerical value for determination here is based on the above equation (13). The inequalities are used because of variations in the optical position detection circuit and errors in the IRED scan position.

Next, in step S14, thus the distance measurement result of the center of the screen obtained Compare L _MNO and a predetermined distance L _1. Here, for example, if the distance is shorter than L ₁ = 5 m, the subject at the center is considered to be the main subject, so the process branches to step S15 to focus on the distance measurement result L _MNO at the center of the screen. . On the other hand, if the distance is L ₁ = 5 m or more, the process branches to step S16 because there is no main subject at the center of the screen. Then, similarly to step S12 of FIG. 7, in step S16, the closest distance is selected from the obtained M ₁ × N ₁ distance measurement results, and the focus is adjusted here.

  In such an embodiment, it is possible to correctly focus on the person who is the main subject even in the scene shown in FIG.

  By the way, as shown in FIG. 14, the positional relationship between the finder lens 27 of a general conventional camera and the light projecting means (IRED 11, light projecting lens 13) is fixed, and the screen at the position indicated by 27a is fixed. Even if distance measurement is possible at the center, distance measurement at the center of the screen is not possible for the screen at the position indicated by 27b. This is referred to as a parallax error between the distance measuring system and the finder system. In the third embodiment described above, it is possible to take measures against such a parallax problem.

  In the above description, the IRED scan mechanism shown in FIG. 3 is assumed as an example of the distance measurement optical scan. However, the present invention is not limited to this, and for example, shown in FIGS. 15 (a) and 15 (b). Such a mechanism can be substituted. That is, FIG. 15A shows a configuration of a unit 50 that can integrally turn the light projecting lens 13 and the IRED 11 and rotate around the fulcrum 49. FIG. 15B shows a mechanism for reflecting the distance measuring light of the IRED 11 projected through the light projecting lens 13 by a mirror 52 that can rotate around a fulcrum 51.

  In the above-described embodiment, the PSD is used as the optical position detection element. However, the present invention is not limited to this, and a two-split SPD may be used.

  Next, a further embodiment of the present invention will be described with reference to FIGS.

In FIG. 16, the IRED 53 is arranged in the vertical direction of PSDs 54 and 55 having a size represented by a length t and a width w, that is, in the middle of the y direction in the drawing. In front of these IRED 53 and PSDs 54 and 55, a light projecting lens 56 and light receiving lenses 57 and 58 are arranged in the vertical direction, respectively. The distance measuring light 59 projected from the IRED 53 via the light projection lens 56 can be changed in the light projection direction by the scanning device 60 (θ _x ). The scan position is input to the CPU 62 by the position detection circuit 61.

  The reflected signal light received through the light receiving lenses 57 and 58 is received by the PSDs 54 and 55, and the light receiving position is detected by the AF circuit 63. In the AF circuit 63, a value for correcting the distance measurement result is obtained from an inclination adjustment circuit 64 described later.

  The CPU 62 is connected to an EEPROM 65, which is an electrically rewritable memory that stores adjustment values of the apparatus.

  FIG. 17 is an external view of a camera on which the distance measuring apparatus having such a configuration is mounted. In the figure, a release switch 67 is provided on the upper surface of the camera body 66. On the front surface of the camera, a photographic lens 68 is disposed at a substantially central portion, and a finder objective lens 69 is disposed above the photographing lens 68. A light receiving lens 57 is disposed adjacent to the viewfinder objective lens 69 at the periphery of the photographing lens 68, and a light projecting lens 56 and a light receiving lens 58 are disposed below the light receiving lens 57 as shown in the figure. Yes. Reference numeral 70 denotes a strobe.

  Next, the operation of the two PSDs of the distance measuring apparatus having such a configuration will be described with reference to FIG.

The PSD 54 can measure the position of an optical signal incident from the range of θ ₅₇ via the light receiving lens 57. On the other hand, the PSD 55 can measure an optical signal from the range of θ ₅₈ via the light receiving lens 58. Therefore, the position of the light spot at which two PSDs can be measured simultaneously falls within the range of θ _y indicated by the shaded portion E in FIG. That is, if the distance from the end of the PSD to the optical axis of the light receiving lens is a and the focal length is f _J , θ _y is expressed as in equation (14).

Here, if f _j = 16 mm and a = 0.3 mm, θ _y is only about 2 °.

On the other hand, as shown in FIG. 16, in consideration of the width w of the PSDs 54 and 55, the detectable range θ _x of the light spot in the x direction shown in the figure is
θ _x = arctan (w / f _J ) (15)
When w = 3 mm and f _J = 16 mm, θ _x is 10.6 °. In order to increase θ _y , it is conceivable to increase a. However, if a is increased, the PSD length t increases, and the AF resolution deteriorates.

  Considering this, it can be seen that if the distance measuring device is used to measure the distance of many points in the photo screen, the x direction can cover a wider range than the y direction.

  FIG. 18B shows the light spot positions in the y direction incident on the PSDs 54 and 55 when the distance measuring light 59 moves in the y direction at the same distance. As shown in FIG. 18A, the light spot positions 54a and 55a on the PSD by the outputs of the PSDs 54 and 55 intersect at the positions where light is incident symmetrically on both PSDs. If the light receiving lenses 57 and 58 and the PSDs 54 and 55 are arranged with good symmetry and the circuits for processing the outputs of the two PSDs have exactly the same characteristics, the correct distance measurement can be performed by adding the results of 54a and 55a. The result can be obtained.

  It should be noted here that if the circuit or the arrangement of each element becomes unbalanced, the slope of the output of each PSD becomes unbalanced as shown by the straight line 55b, and correct measurement is possible even by the above addition. The distance result is not obtained. The inclination adjustment circuit 64 described above electrically corrects this.

  FIG. 18C shows the light spot positions in the y direction on the PSDs 54 and 55 when the distance measuring light 59 moves in the x direction at the same distance. Since there is no change in the y direction, the output is ideally constant as shown in the figure.

  Therefore, the distance measuring apparatus having the configuration shown in FIG. 16 outputs two PSDs for the distance measuring light incident from the range of 10 ° in the x direction and 2 ° in the y direction under the conditions of the above constants. Distance measurement is possible.

  With such a distance measuring method, as shown in FIG. 19, it is possible to focus correctly on distance measuring light reflected from a portion of a range E ′ of 2 ° × 10 ° within the screen. Become. Therefore, even when the distance measuring light spreads as shown in FIG. 19 and protrudes from the subject, there is an advantage that the distance can be correctly measured as long as the reflected light is returned.

In particular, in a long-distance subject, the projection spot diameter φ _T increases in proportion to the distance L due to the relationship of the equation (16). Thus, it is likely to be from phi _T is larger magnitude phi _F face.
φ _T = (φ _LED / f _T ) · L (16)
Where f _T : Projector lens focal length
φ _LED : IRED emission diameter In the general active triangular distance measuring method, correct distance measurement can be performed only under the condition of φ _F > φ _T. However, according to the embodiment, as described above, the light for distance measurement from the subject is used. If a part of the light is reflected and enters two PSDs, there is an advantage that correct distance measurement is possible.

  Next, the embodiment will be described in more detail with reference to FIG.

  The IRED 53 is controlled to emit light by the CPU 62 via the IRED driver 71 and is attached to the movable member 72. The IRED 53 is movable in the x direction in the figure by a motor 73 and a feed screw 74, and in the y direction by a motor 75 and a feed screw 76. Then, the CPU 62 controls the rotation of the motors 73 and 75 via the motor (M) drivers 77 and 78, whereby the relative position between the IRED 53 and the light projecting lens 56 can be controlled.

  The initial position switch 79 is for detecting the initial position of the IRED 53, and the CPU 62 detects the position of the IRED 53 depending on how much each motor has rotated from this initial position. Since the direction of the light beam passing through the light projection lens 56 changes depending on the position of the IRED 53, the distance measuring light projection point 59 can be changed as shown in FIG. While changing the position of the IRED 53 in this way, the CPU 62 controls the IRED driver 71 to measure each part in the screen.

  The distance measuring light thus projected is reflected on a subject (not shown) and imaged on the PSDs 54 and 55 via the two light receiving lenses 57 and 58. From the distance measuring light incident on these PSDs 54 and 55, two current signals having outputs corresponding to the incident position of the light are output by the function of the PSD. These current signals are absorbed by the preamplifiers 80, 81, 82, 83 with low input impedance, amplified, and input to the compression diodes 84, 85, 86, 87.

The respective compressed voltages generated in the compression diodes 84, 85, 86, 87 are guided to the bases of the NPN transistors 92, 93, 94, 95 on the basis of the reference voltage V _ref by the buffer circuits 88, 89, 90, 91, respectively. . The NPN transistors 92 and 93, and 94 and 95 constitute a differential circuit in which emitters are connected in common. The emitters of these NPN transistors are connected to current sources 96 and 97 that can flow or stop a predetermined current value in synchronization with the light emission of the IRED 53. The collectors of the NPN transistors 93 and 94 are connected to Vcc, and the collectors of the NPN transistors 92 and 95 are connected to Vcc through an integrating capacitor 98. The output voltage of the integrating capacitor 98 is controlled by the CPU 62 and can be initialized by the switch 99.

In this way, the two output currents of the PSDs 54 and 55 are compressed and input to the differential circuit, so that the collector currents of the NPN transistors 92 and 95 are outputs proportional to the signal light incident position of each PSD. These collector currents are I ₉₂ and I ₉₅ .

Here, using the symbols shown in FIG.
I ₉₂ = A ₉₂・ (a + y ₅₄ )
I ₉₅ = A ₉₅ · (a + y ₅₅ ) (17)
_A92 , _A95 : Proportional constant
Therefore, when A ₉₂ = A ₉₅ , when the switch 99 is turned off and the IRED 53 is caused to emit light, the voltage V ₉₈ generated in the integrating capacitor ₉₈ is
V ₉₈ = A ₉₂ (2a + y ₅₄ + y ₅₅ ) · B ₉₈ (18)
B ₉₈ : Proportional constant
It becomes.

That is, since the relationship expressed in equation (19), CPU 62 is when inputted by the built-in A / D converter of this V _98, y ₅₄ + y ₅₅ from V ₉₈ is determined.

Therefore, the subject distance L is
L = S · f _J / (y ₅₄ + y ₅₅ ) (20)
Can be calculated as

  When the distance of a landscape or the like is measured, the reflected signal light from the subject may not enter the PSD. In this case, if the amount of signal light is small, the output voltage of the compression diode becomes small, and distance measurement calculation due to noise is performed. Since the calculation result is naturally irrelevant to the correct subject distance, the output voltages of the compression diodes 85 and 87 are determined by the comparison circuits 100 and 101. When the output voltage is smaller than a predetermined level, the comparison circuit outputs a determination signal to the CPU 62. Therefore, when detecting this signal, the CPU 62 ignores the output voltage of the integrating capacitor 98 and determines that the subject distance is, for example, infinity.

  Reference numeral 102 denotes an inclination adjustment circuit described as 55a and 55b in FIG.

FIG. 21 is a diagram for explaining the adjustment circuit 102. For example, as shown in FIG. 21C, the positional relationship between the light receiving lenses 57 and 58 and the PSDs 54 and 55 may not match correctly in manufacturing. That is, it is difficult to completely match f _J54 with f _J55, and it is difficult to completely match the inclinations θ ₅₄ and θ ₅₅ in the assembly of the PSD.

  Such an assembly error directly leads to a tilt error of the AF result as shown in FIG. 18B. In order to adjust the tilt mechanically, a dedicated adjustment mechanism is prepared. This tends to be expensive and the adjustment time tends to be long. Therefore, the adjustment circuit 102 and the EEPROM 65 are used to electrically adjust this.

  More specifically, the adjustment circuit 102 is configured as shown in FIG. 21A and switches the current value of the current source 96.

When the current value of the current source 96 changes, the above-described collector current I ₉₂ of the NPN transistor ₉₂ and the proportional constant A ₉₂ of the light position y ₅₄ incident on the PSD ₅₄ can be changed. Accordingly, when the proportional constant A ₉₂ does not coincide with the proportional constant A ₉₅ of the other light receiving system due to the assembly of the PSD, this can be electrically adjusted to enable correct distance measurement.

  The current source 96 is constituted by an NPN transistor as shown in the figure, and forms a current mirror circuit together with the NPN transistor 103. The NPN transistor 103 has a collector and a base that are short-circuited, and five constant current sources 104, 105, 106, 107, and 108 are connected to the collector. Among the current sources 104 to 108, the four current sources 105 to 108 are controlled to be turned on and off by a counter circuit including flip-flops 109, 110, 111, and 112.

The CPU 62 can turn on and off each current source by controlling the counter circuit to input a CK (clock) signal and a Reset (reset) signal. When a predetermined clock is input to the CK terminal of the counter circuit in the state of the reset signal L (low level), the current value I _INT flowing through the collectors of the transistors 103 and 96 changes as shown in FIG. .

Therefore, when the device is assembled, the difference between A ₉₂ and A ₉₅ based on the PSD assembly error, etc. is detected, the value of I _INT is calculated to cancel the difference, and the value corresponding to the number of clocks is calculated. It may be stored in an electrically writable ROM (EEPROM) 65.

  Note that the transistor 113 in FIG. 21A is a switch for controlling on / off of the current source 96 in synchronization with light emission of the IRED.

If the PSD has inclinations as shown by θ ₅₄ and θ ₅₅ in FIG. 21C, when the IRED is scanned in the x direction, the AF result changes even if the subject distance is equal. Therefore, a graph that does not change with respect to x as shown in FIG. 18C cannot be obtained.

  Therefore, a correction coefficient that cancels this error according to x is input to the EEPROM 65 at the IRED scan position. The CPU 62 can detect the scan position x from the number of rotations of the initial position switch 79 and the motor 73 (see FIG. 20). A distance measurement result obtained when the position of x is measured is input to the EEPROM. If the correct distance measurement result is determined after correction with the correction value corresponding to x, the PSD assembly process can be simplified, and the cost can be reduced.

  Next, with reference to FIG. 22, a method of measuring the distance outside the range E where the two PSDs 54 and 55 cannot be detected simultaneously will be described.

When the IRED 53 projects light from a position shifted by y _LED from the optical axis of the light projection lens 56, the above-described method is insufficient for distance measurement of the portion 59 of the subject distance L. This is because the reflected signal light from the portion 59 does not enter the PSD ₅₅ even if it enters the PSD ₅₄ , and y ₅₅ cannot be detected.

However, since the reflected light is incident on y _{54 of the} other PSD ₅₄ , distance measurement is possible according to this information. That is, if the distance between the principal points of the light projecting and receiving lenses 56 and 57 is S ₁ and the focal length of the light receiving lens 57 is f _J
L = S ₁ · f _J / (y _LED + y ₅₄ ) (21)
It becomes.

  FIG. 23 is a flowchart for explaining the operation of this distance measuring apparatus that enables distance measurement even in such a case. The operation will be described below according to this flowchart.

First, in step S41, the CPU 62 detects the position yLED of the IRED 53 from the number of rotations of the initial position switch 79 and the motor 73. Next, in steps S42 and S43, the value of yLED is determined. Here, only when the y _LED satisfies the condition of −y _g ≦ y _LED ≦ y _g , the process proceeds to the distance measurement process using the PSDs 54 and 55 after step S44. The above-y _g and y _g represent the limit of the position of the y _LED for the distance measuring light 59 to enter the shaded area E in FIG.

In step S44, the emission of the IRED 53 is started. Subsequently, in steps S45 and S46, the currents are detected so that the two PSDs ₅₄ and ₅₅ perform integration operations for detecting the signal light incident positions y54 and y55, respectively. Sources 96 and 97 are turned on. Then, the signal is integrated into the integrating capacitor 98, and it is determined in step S47 that the integration for a predetermined time has ended. If it is determined in step S47 that the integration has been completed, the light emission of the IRED 53 is then terminated in step S48. Thereafter, in step S49, the subject distance L is calculated from the charging voltage of the integrating capacitor 98 according to the distances S between the two light receiving lenses and y ₅₄ and y ₅₅ .

On the other hand, if it is considered in step S42 that y _LED becomes large and no signal is input to the PSD ₅₄ , the process branches to step S50. Then, after the IRED 53 emits light in step S50, the current source 97 is turned on for integration operation for detecting the signal light incident position y55 on the PSD ₅₅ in step S51. Next, when the end of integration is detected after a predetermined time in step S52, the end of light emission of the IRED 53 is controlled in step S53. Thereafter, the detected y ₅₅ from the integrated result in the step S54, the distance between the y _LED and projection lens 56 and the light receiving lens 58, the object distance L is calculated.

Further, in the above-mentioned step S43, if the y _LED is determined to exceed -y _g, a situation as just illustrated in FIG. 22. Therefore, after the IRED 53 emits light in step S55, the current source 97 is turned on in step S56. Next, when integration end detection is performed after a predetermined time in step S57, the light emission end of the IRED 53 is controlled in step S58. Thereafter, in the same manner as in the above step S54, in step S59, from y ₅₄ , y _LED and S ₁ (see FIG. 22),
A subject distance L is calculated.

As described above, by using the IRED scan position y _LED and the distance calculation in consideration of the distance between light projection and reception, it is possible to provide an apparatus capable of measuring a wider angle of view.

1 is a block diagram showing a concept of a distance measuring device in a first embodiment of the present invention. FIG. It is the figure which showed the ranging principle of the ranging apparatus of this invention. It is a block diagram which shows the structure of 2nd Example of this invention. (A) is an external view showing an arrangement in which the distance measuring device shown in FIG. 3 is incorporated in a camera, and (b) is a diagram showing an example of a distance measuring point that changes two-dimensionally on a photographic screen (finder). It is. It is a circuit block diagram which shows the detail of the optical position detection circuit of FIG. (A) is a diagram for explaining a method for obtaining the subject distance L from the light position detection circuit of FIG. 3 and the signal light position on the PSD, and (b) is the principal point of the light receiving lens on the PSD of FIG. It is the figure which showed arrangement | positioning of the direction (x) which connects, and the perpendicular direction (y) to it. It is a flowchart explaining the scan AF operation of the distance measuring apparatus. It is a subroutine explaining the ranging operation in step S6 of FIG. It is the figure which showed the example which scans a ranging point. It is the figure which showed the example of the scene where a to-be-photographed object does not exist in the point of the center part of a screen. It is the figure which showed the example of the scene where a main subject exists including a miscellaneous subject in the screen center part. (A) is the 3rd Example of this invention, and is a front view which shows the arrangement | positioning which incorporated the ranging apparatus in the camera, (b) is the conceptual diagram which looked at the camera of the same figure (a) from the upper part, (c). FIG. 4 is a conceptual diagram showing only the y coordinate of the camera of FIG. It is a flowchart explaining the operation _| movement of the 3rd Example which gave importance to the ranging result _LMNO of the screen center part. It is the figure which showed the positional relationship of the finder lens of a general camera, and a light projection means. It is the figure which showed the other structural example of the optical scan for ranging. In the further Example of this invention, it is the block diagram which showed the concept of the ranging device. FIG. 17 is an external view of a camera on which the distance measuring apparatus having the configuration of FIG. 16 is mounted. It is a figure explaining operation | movement of two PSD in the distance measuring device of the further Example. It is the figure which showed the relationship between IRED and the ranging light in the ranging apparatus of the further Example. It is a block diagram showing the structure for demonstrating the further Example in detail. FIG. 20 is a diagram illustrating details of the adjustment circuit 102 in FIG. 20. FIG. 20A is a circuit configuration diagram, and FIG. 20B shows a relationship between the number of CKs of the counter circuit and the current value I _INT flowing through the collectors of the transistors 103 and 96. FIG. 4C is a diagram showing the positional relationship between the light receiving lenses 57 and 58 and the PSDs 54 and 55. It is a figure explaining the method to measure a range other than the range E which two PSD54,55 cannot detect simultaneously. It is a flowchart explaining operation | movement of the ranging apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... CPU, 2 ... Light projection part, 3 ... Scanning part, 4, 6 ... Light receiving lens, 5, 7 ... Optical position detection element (PSD), 8, 8a, 8b, 9, 9a, 9b ... Optical position detection circuit DESCRIPTION OF SYMBOLS 10 ... Light spot for ranging, 11 ... IRED, 12 ... IRED driver, 13 ... Projection lens, 14 ... IRED holding part, 15, 19 ... Motor (M) driver, 16, 20 ... Motor, 17, 21 ... Feed screw, 18, 23 ... guide rail, 22 ... support, 24 ... switch.

Claims (1)

A pair of light-receiving means for detecting the position of the reflected signal light from the subject of the ranging light, arranged at a predetermined baseline length;
A projector lens;
A light projecting means disposed between the pair of light receiving means for projecting the distance measuring light to the subject via the light projecting lens;
A first calculation process for detecting a distance to a subject based on an output signal of the pair of light receiving means, and a first arithmetic processing for detecting a distance to the subject based on an output signal of one of the pair of light receiving means. A computing means for performing two computing processes;
Comprising
The light projecting means can be shifted in the base line length direction around the optical axis of the light projecting lens, and the computing means can be configured such that the pair of light receiving means is in accordance with the shift range of the light projecting means. When the reflected signal light from the subject can be detected at the same time, the distance to the subject is detected based on the output signals of the pair of light receiving means, and only one of the pair of light receiving means is reflected signal light from the subject. A distance measuring device that detects the distance to the subject based on the output signal of the one light receiving means when it can be detected .

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