JP3001302B2 - Distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique of camera focusing (AF).

[0002]

2. Description of the Related Art There are two types of distance measuring devices for a camera: a passive type based on luminance information of a subject, and an active type which emits distance measuring light to the subject and measures the distance in accordance with the reflected signal light. . The triangulation AF of the active method is a technique that is realized on the premise that light for distance measurement is correctly projected on a subject.

[0003] This technique will be described with reference to FIG. A light emitting lens 22 from an infrared light emitting diode (IRED) 20;
The light signal projected onto the subject 23 through the light receiving lens 24 enters a light position detecting device (PSD) 25 through a light receiving lens 24. The incident position x is determined as a function of the subject distance l as x = S · f / l (1) since the distance S between the principal points of the light emitting and receiving lens and the focal length f of the light receiving lens are constant.

That is, 1 can be obtained from the incident position x of light, and this known x is detected by a known light position detecting element (PSD) 25. PSD is I _A,
Outputs two signals of I _B, in this case, _I A / _(I A +
I _B) is _{I A / (I A + I} B) = (a + x) / t = (a
+ S · f / l) / t (2) Where t
Is the length of the PSD, and a is the distance from the end of the PSD to the point where the PSD and the optical axis of the light receiving lens cross.

When the light projecting unit is displaced by Y in the base line length direction as shown in the drawing, when the focal lengths of the light projecting and receiving lenses are equal, the incident position of the reflected signal light returned from the subject at the same distance is also PSD25. Shift by Y over That is, at this time, unlike the expression (1), the relationship between l and x is as follows: x−Y = S · f / l (3) Therefore, the expression (2) becomes I _A / (I _A + I _B ) = (a + x) / t = (a + Y + S · f / l) / t (4), and the expression (2) is corrected by Y / t. Otherwise, correct distance measurement will not be possible.

In FIG. 12, light rays are represented as straight lines. However, in practice, a perfect point light source cannot be used as a light source, and the projected beam spreads as shown in FIG. have.

[0007]

As described above, when the light beam is completely projected on the subject, the distance can be measured correctly. However, in the case of the conventional active triangulation AF, FIG. ), When the projection beam is partially missing (spot missing), the light of the part deviating from the subject is not received, and the spot image formed on the PSD shifts the center of gravity, and correct distance measurement is not possible. Will not be done.

The distance measuring apparatus of the present invention has been made in view of such a problem, and its purpose is to change the shape of the light projecting spot so that the light projecting spot is lost from the subject. It is an object of the present invention to provide a distance measuring device capable of preventing erroneous distance measurement.

[0009]

In order to achieve the above object, a distance measuring apparatus according to a first aspect of the present invention comprises a light projecting means for projecting projection light toward a subject, and a reflected light from the subject. And a distance calculating means for calculating the subject distance according to the light receiving position of the reflected light based on the output of the light receiving means. A first spot light that emits one spot light, and which becomes a part of the spot light when individually projected, has a plurality of adjacent light projecting units, and simultaneously projects light projected by the plurality of light projecting units. A projection control mode that has a projection mode and a second projection mode for projecting the projection light from the plurality of projection units in a time-series manner, and switches to a plurality of projection patterns to control the projection. Means. Further, the distance measuring device according to the second invention is the distance measuring device according to the first invention,
When the light projection control unit emits light in a time series with the plurality of light projection patterns, based on a calculation result of the subject distance by the distance calculation unit obtained according to the plurality of light projection patterns, A determination unit is provided for determining whether or not the projection light in the first projection mode is uniformly irradiated on the subject. The distance measuring apparatus according to a third aspect of the present invention is the distance measuring apparatus according to the first aspect, wherein the light projecting means includes a light emitting element formed on one chip and an electrode divided and formed on the light emitting element. And the light emission control means switches a light emitting area of the light emitting element by a combination of energization to each electrode.

[0010]

That is, in the distance measuring apparatus according to the first invention, the light projecting means projects the projection light toward the subject, the light receiving means receives the reflected light from the subject, and the output of the light receiving means. When performing distance measurement by calculating the subject distance according to the light receiving position of the reflected light by the distance calculating means based on
A plurality of adjacent light projecting portions, which become one spot light and become a part of the spot light when individually projected, and configured to simultaneously project the light projected by the plurality of light projecting portions. A light projection control unit having a light projection mode and a second light projection mode for projecting the light projected by the plurality of light projection units in chronological order is switched to a plurality of light projection patterns to perform light emission control. I do. Further, in the distance measuring apparatus according to the second invention, in the distance measuring apparatus according to the first invention, when the light projection control means emits the light in a time series in the plurality of light emission patterns, Based on the result of the calculation of the subject distance by the distance calculation means obtained in accordance with the light projection pattern, the determination means determines whether or not the projection light in the first light projection mode is uniformly applied to the subject. To do. In the distance measuring apparatus according to the third invention, the first
In the distance measuring apparatus according to the invention, the light projecting means is constituted by having a light emitting element formed on one chip and an electrode formed by dividing the light emitting element into a plurality of pieces, and energizing each electrode. The light emitting area of the light emitting element is switched by the light emitting control means by the combination.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In this embodiment, when a spot missing as shown in FIG. 13B occurs, the distance is measured at the light projecting spot as shown in FIG. This is made possible, and more specifically, an IRED having a structure as shown in FIG. 2 is to be used. First, FIG. 3 shows a conventional IRED.
The structure of is shown. (A) is a sectional view, (b) is its appearance, and (c) is the shape of a light emitting spot.

Reference numerals 2 and 4 denote electrodes, one of which is electrically connected to a lead 13 via a wire bonding 15 and the other of which is directly connected to a lead 11. Then, carriers are recombined in the active region 7, and light emission starts. Reference numeral 17 denotes an electrode opening for taking out the electrode.

Here, returning to the sectional view of FIG.
Reference numeral 0 denotes a substrate for forming layers having various functions on the IRED chip, and GaAs, which is a III-V group compound semiconductor,
Is used. Each of layers 6, 7, and 8 is a part generally forming a double hetero structure, and has an n-type GaAlAs layer 6 having a wider band gap and a p-type Ga
The AlAs layer 8 forms a cladding layer, and is designed to perform efficient electro-optical conversion by binding carriers.

The layer 9 is called a block layer and is made of n-type GaAs. When a current flows from the layer 4 to the layer 2, a reverse bias is applied between the layer 9 and the layer 8. ,
Not flow only in the middle of the current narrow 窄 unit 18, a current is crowded run at high current density in the lower part of the active region of the opening 17.

In the wavelength range of the infrared light generated in the active layer 7, the transmittance of GaAlAs is extremely high,
From the spot of the light as shown in FIG. 3 in accordance with the shape of the current narrow 窄 portion 18 and the opening 17 (c) is obtained. In the present invention, the shape of the electrode portion of the IRED having such a structure is devised to change the flow of current supplied to the active layer 7 to change the light emission shape. FIG. 2 is a schematic view thereof, and the electrode 2 in FIG. 3 is divided into 2a and 2b, and the electrode 4 is
, And is divided into three parts 4a and 4b.

By using these electrodes properly, it is possible to change the current flow. FIG. 1 shows a light projecting / receiving lens 31, 32 and PS using such an IRED 30.
It is a conceptual diagram of the light projection / reception optical system of this invention which comprises D33.

In FIG. 1, the current output I of the PSD 33
_{A, I B} is amplified by a preamplifier 35 and 36, the known arithmetic circuit 37 as a difference in logarithmic compression it,
By performing the calculation of I _A / (I _A + I _B ) shown in the equation (2) and inputting it to the calculation control circuit (CPU) 38 composed of a one-chip microcomputer or the like, the calculation of the distance can be performed. Has become. The CPU 38 includes a current source I ₁ ,
By controlling I ₂ and I ₃ , the shape of the AF light can also be controlled, and has the effect of determining the focusing distance of a focusing optical system (not shown) according to the distance measurement result. Hereinafter, the current control and the light emission mode of the IRED will be described with reference to FIG.

FIG. 3A shows a current I ₂ flowing between the electrodes 2b and 4b. Since the current is concentrated on the right side of FIG.
A light emission pattern b deviated to the right as shown in FIG. (C) shows a state in which the current I ₃ flows between the electrodes 2a and 4a. Since the current flows intensively on the left side of the figure, the light emission of the pattern shown by d as in (d) is shown. A spot is obtained.

Further, when an electric current is applied between the electrodes 2a, 2b and 5 as shown in (e), the central portion of the opening 17 shines in a band as shown in (f). This light emission pattern is c
And

The current sources I ₁ , I ₂ and I ₃ are simultaneously turned on.
When N, the flow of the current is almost the same as that of the IRED in FIG. 3, so that the light emission spot has almost the same shape as the opening 17, and the light emission pattern of a shown in FIG. As described above, the light emission pattern is switched according to the current sources I ₁ , I ₂ and I ₃ . The control of the IRED is summarized as shown in FIG.

FIG. 1 shows a distance measuring apparatus in which the above-described IRED is configured as 30. The light of the IRED 30 is projected through the light projecting lens 31 toward the subject, and the reflected light spot is projected through the light receiving lens 32 to the PSD 33.
34, b, c, and d indicate that the image is formed above.
It is. If the light emission with the shape of the opening is a, b, b
The state where the area where c and d are combined shines is a.

In this figure, as can be easily understood, when the light is emitted from the pattern a and the light is emitted from the pattern c, when the center of gravity of the light spot in the base line length direction is a reflected light from the same distance, the light is substantially emitted. Although it can be considered to be equal, even when the distance is measured with the b or d light emission pattern, even if the subject is at the same distance, there is a difference in the incident spot position on the PSD as compared with the distance measurement with the pattern a. .

This requires correction by the method already described with reference to FIG. 12 and equation (4), and the CPU 38 performs distance measurement in the patterns a and c by the amount Y / t in equation (4). By performing the corrected calculation, a correct distance measurement result can be obtained.

In the case of the distance measuring system arranged as shown in FIG. 1, the signal light incident on the PSD moves in the direction of N as the subject distance decreases and moves in the direction of F as the distance increases. That is, as shown in FIG. 13B, when a spot is missing, for example, if the spot b is missing, the distance measurement result of the spot a is shifted to the far side. Then, the distance measurement result by the light projection spot of d becomes a correct value.

On the other hand, if the spot d is missing, the result of distance measurement using the spot a will be shifted to the near side. Then, the distance measurement result by the light projection spot b becomes a correct value.

In this way, it is possible to prevent erroneous distance measurement due to spot missing, which is a problem of active AF. That is, as shown in FIG. 5, to a subject who is at a distance of l _0, there is no spot eclipse as state 1, when the AF light strikes the object, can be correctly ranging Any conventional AF, In the following states 2, 3, 4, and 5, the PS
Movement of the center of gravity of spot D causes erroneous distance measurement.

In the present invention, the distance measurement information at each of the spots a, b, c, and d is sequentially inputted, thereby discriminating the above-described spot missing state and eliminating erroneous distance measurement. However, in the state of 6 in FIG. 5, since the spot is completely deviated, in such a case, a countermeasure must be taken with a known multi-AF that measures a plurality of points.
It cannot be dealt with by the present invention. Below, FIG.
A method for determining the states 2 to 5 in FIG. 5 and eliminating erroneous distance measurement will be described with reference to the flowchart of FIG.

First, in steps S1 to S4, as described above, the distance measurement result is converted to the CP while changing the shape of the spot.
This is the process of inputting to U. A, after step S5
b, c, and d represent the distance measurement results in each spot state.

In step S5, a state in which a distance measurement result at infinity is shown in any spot is determined, and a situation like state 6 in FIG. 5 is considered. In step S10, the focusing lens is uncovered.

Next, at step S6, the distance measurement result at the spot a and the spots b and d divided and projected in the base line length direction are obtained.
It is determined whether or not the distance measurement results are substantially equal. At this time, if they are equal, the state of 1 in FIG. 5 should have been discriminated.
Focusing lens is controlled by focusing on the result of distance measurement.

Next, in step S7, of the IRED spots divided in the base line length direction, b
Is determined for the spot of. That is, in the states 4 and 5 in FIG. 5, the distance measurement data of b is correct and the distance measurement data of a is incorrect.
In state 4, 5 (see FIG. 1) from the arrangement of the light projecting and receiving systems and IRED, the measurement result of the spot a is not because it is shifted farther than the actual distance l _0, which can be determined.

That is, assuming that the difference between the distance measurement results is α, in step S 7, the result of a is longer than the result of b, and the degree is not extreme, such as ∞, but is a−α. It is determined only when the relation of <b is satisfied. For example, spot a does not lack a spot,
FIG. 7A shows a state of incidence on the PSD. In FIG. 12, if S = 50 mm and f = 14 mm, 1 = 3 m
In the case of x, x = S · f / l = 50 × 16/3000
= 800/3000 = 0.26. On the other hand, FIG. 7B shows an example in which the spot is partially missing, and the center of gravity is φ / 4.
If it is shifted, φ is set to 0.36 and x ′ = 0.26
−φ / 4 = 0.26−0.09 = 0.17. Therefore, even if this state is incorrectly calculated, 1 is

1 = S · f / x ′ = 50 × 16 / 0.17
Calculating this, l is about 4.7 m,
Thus, the error for 3 m is +1.7 m.
That is, α may be considered to be about ± 2 m. When the process branches from step S7 to step S12, the lens extracts the distance measurement result of the spot b. Also,
It is also possible to determine the gap and correct the distance measurement result of a.

[0034] Step S8 is the opposite, the determination of when the missing spot b, d of the spot is shifted to the side distance measurement result is closer than the actual distance l ₀ of a Despite the distance measuring correctly Therefore, the lack is determined by this. That is, in step S8, the determination of the states 2 and 3 in FIG. 5 is performed, and in step S13, correct focus can be obtained by extracting d. Alternatively, the distance measurement result of a
Contrary to 12, correction may be made to the far side.

If the step S8 branches to N, it is considered that some abnormal state has occurred, rather than any of the states 1 to 6 in FIG. In this case, the lens should be focused in accordance with the distance measurement result of c, which has the least fear of chipping.

Here, steps S12 and S13
Correction for the distance measurement result of spot a described in
When the light emission area and the like are considered, the spot of a is b, c,
The output energy is larger than d, and distance measurement in that state is most advantageous in S / N. Therefore, in order to effectively utilize the distance measurement result of a, the distance measurement result of a is shifted by φ / 4 by determining the state shown in FIG. 7B, for example. Can be corrected. Assuming that the distance measurement result at the spot a in FIG. 7 (b) is l ′, when the correct l is that φ is approximately 0.36, S and f are fixed values, so l = S · f / x = S · f / (S · f / l + φ / 4) (5)

FIG. 8 shows a second embodiment of the present invention. In this embodiment, the IRED 30 uses an array of three chips 54, 55 and 56 as shown in FIG.

The chips 54, 55 and 56 is a chip of known infrared emitting diodes, for the double hetero structure having no current narrow 窄 unit as described in Figure 3, or be of a mere PN junction Good. These have one electrode connected to a common frame 53 and the other electrode connected to the frames 50, 5 via wire bonding.
1 and 52, and independent chipping of each chip is possible depending on which of the three lead frames is energized.

Therefore, the CPU 38 controls the current sources I ₄ , I ₅ , and I ₆ as shown in FIG.
The spot pattern shape in which the IRED 30 irradiates the subject via the light projecting element 31 can be changed as shown in FIGS.

In this IRED array, the light emission pattern is changed in the base line length direction, so that spot missing can be detected by a method similar to that described with reference to FIG. This embodiment is considered to be advantageous in terms of cost although there is a problem that the harmful light reflected by the adjacent chip has a large effect and the chip size cannot be reduced too much.

[0041]

As described above, according to the present invention,
A light emitting element capable of changing the shape of a light projection spot can be provided. Also, by utilizing this, it is possible to prevent erroneous distance measurement when a light projection spot, which is a weak point of the conventional active triangulation, is missing from the subject.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a distance measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a structure of an IRED used in one embodiment of the present invention.

3A is a cross-sectional view of the structure of a conventional IRED, FIG. 3B is an external view thereof, and FIG. 3C is a view showing a shape of a light emitting spot.

FIGS. 4A to 4F are diagrams for explaining current control of the IRED and a light emission mode thereof.

FIG. 5 is a diagram for explaining which of the light emitting spots corresponding to the respective states of the light emitting spots selects the distance measurement result.

FIG. 6 is a flowchart showing a procedure for obtaining a correct distance measurement result according to each state of FIG.

FIG. 7A is a diagram showing a state in which a spot a is incident on a PSD without chipping, and FIG.
(B) is a diagram showing a state where a spot is partially missing.

FIG. 8 is a configuration diagram of a distance measuring apparatus according to a second embodiment of the present invention.

FIG. 9 is a diagram showing an example of the IRED of FIG. 8;

FIG. 10 shows an example of switching light emission patterns according to a current source.
It is the figure which summarized control of RED.

FIG. 11 is a diagram summarizing the control of the IRED according to the second embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a conventional triangulation AF device.

FIGS. 13 (a) to 13 (c) are diagrams for explaining a problem that occurs when the projection beam is partially missing from a subject.

[Explanation of symbols]

2,4 ... electrode, 30 ... IRED, 31 ... light projection lens, 3
2: light receiving lens, 33: PSD, 34: light emission pattern,
37: arithmetic circuit, 38: CPU.

Claims (3)

(57) [Claims] 1. A light projecting means for projecting a projection light toward a subject, a light receiving means for receiving reflected light from the subject, and a light receiving position of the reflected light based on an output of the light receiving means. in the distance measuring apparatus comprising a distance calculating means for calculating the object distance, the light projecting means comprises a when projected simultaneously one spot beam, a part of the spot light when individually to project,
A first light-emitting device having a plurality of light-projecting portions adjacent to each other and simultaneously projecting the light projected by the light-emitting portions;
And the projection mode of the multiple
And a second light emitting mode for projecting light in a row.
Light emission control hand that controls light emission by switching the number of light emission patterns
A distance measuring device comprising a step . 2. A calculation result of the subject distance by the distance calculation means, which is obtained in accordance with the plurality of light projection patterns, when the light is projected in time series by the plurality of light projection patterns by the light projection control means. The distance measuring apparatus according to claim 1, further comprising: a determination unit configured to determine whether or not the projection light in the first projection mode is uniformly applied to the subject based on the distance. 3. The light emitting means has a light emitting element formed on one chip and an electrode formed by dividing the light emitting element into a plurality of light emitting elements. 2. The distance measuring apparatus according to claim 1, wherein the light emitting area of the light emitting element is switched by a switch.