JPH11183163A - Ranging device and computer-readable storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the range-finding time of a range finder that uses a skin CCD and measures distance by correlation operation. SOLUTION: Pulse-shaped luminous flux is applied to an object 15 from an IRED 14, the reflected light is received by sensors A16 and B17, and correlation operation is made according to each of output 18 and 19. In this case, time until the amount of accumulated charge after light is received by each of sensors A, B16 and 17 exceeds a setting value is measured, and the starting and ending values of the shift of the correlation operation are changed corresponding to the measured time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a distance measuring apparatus suitable for performing distance measurement using a skim apparatus and a computer-readable storage medium used in the distance measuring apparatus.

[0002]

2. Description of the Related Art A ranging device using a skim device has been known. The skim device includes a plurality of charge transfer channels connected in a loop to form a cyclic shift register, and operates so as to gradually add signal charges while circulating signal charges that have been photoelectrically converted in accordance with charge transfer pulses. For example, Japanese Patent Publication No. 5-22843 proposes a skim device in which a charge transfer section is formed in a ring shape to integrate a signal and at the same time remove external light.

FIG. 5 shows a schematic configuration of an image pickup device (hereinafter referred to as a skim CCD) using a skim device. In FIG. 5, reference numeral 20 denotes a light receiving sensor, which is composed of three photoelectric conversion elements of X, Y, and Z, and each photoelectric conversion element generates an electric charge corresponding to the amount of incident light. This skim CCD has an active mode in which an IRED 14 as a light emitting element is turned on and off in a pulsed manner and projected on a distance measuring object 15 and the reflected light is received by a light receiving sensor 20 to accumulate electric charges. The distance can be measured both in a passive mode in which electric charges are accumulated using reflected light of external light from the object 15 to be measured. This is a hybrid type distance measuring device that shifts to the passive operation when a reliable distance measurement result cannot be obtained by the active distance measuring operation.

The light receiving sensor 20 has 22 ON pixels and 2 ON pixels.
Each of the three OFF pixels has a configuration corresponding to each of the X, Y, and Z photoelectric conversion elements, and the charges accumulated by the light receiving sensor 20 are transferred to the ON / OFF pixels 22, 23,
Thereafter, it is transferred to the ring 21.

FIG. 6 is a timing chart of the charge transfer of the pixels 22 and 23. The charge accumulated in the light receiving sensor 20 during the High (ON) period of the accumulation time signal is transferred to the ON pixel 22 in synchronization with the High of the ON pixel transfer signal, and is received during the Low (OFF) period of the accumulation time signal. The electric charge accumulated in the sensor 20 is the Hig of the off-pixel transfer signal.
The data is transferred to the off pixel 23 in synchronization with h. The accumulated charge of each pixel (photoelectric conversion element) of X, Y, Z is turned on,
After being transferred to the off pixels 22 and 23, each image data is transferred to the ring 21 in synchronization with the High of the ring transfer signal. This ring transfer signal is the ON pixel 22 of the X pixel.
It is output in synchronization so that the same is added.

In the case of active distance measurement, the IRED1
Terminal 4 is turned on / off in synchronization with the accumulation time signal,
In the case of passive distance measurement, the terminal of the IRED 14 remains OFF regardless of the accumulation time signal. The numbers 1, 2, and 3 in the figure indicate the number of rings, and the number of rings in FIG.
Two or three times.

FIG. 7 schematically shows a state in which the accumulated charge amount in one ring and the accumulated charge amount are added when the number of rings is increased. The number of rings refers to the number of times that the pixel signal has been transferred to the ring, and the term "one ring" means that the accumulated charge has been transferred only once to the ring and has been accumulated only once. In this case, the accumulation is performed three times, and the total of the accumulated charges obtained by the three accumulations is stored in the ring. As described above, when the signal charge of one ring is not at a sufficient level, the signal charge having a good SN ratio can be obtained by turning the ring (by increasing the number of accumulations) and sequentially adding the signal charges. it can.

Conversely, when the amount of light incident on the light receiving sensor 20 is large, it is necessary to adjust the amount of accumulated charges in order to prevent the light receiving sensor 20 from being saturated. As the adjustment method, adjustment of the accumulation time by the electronic shutter function, the light receiving sensor 2
There is adjustment of the accumulation time by increasing the driving frequency of 0. In the method using the electronic shutter function, assuming that the reference accumulation time is 100%, if the object to be measured is bright, the accumulation time is 70%, 50%. . . Thus, the amount of accumulated charges can be reduced. In the method of increasing the driving frequency,
If the charge is saturated at a frequency of 1 MHz, the storage time can be reduced by half by setting the frequency to 2 MHz even under the same storage condition, so that the storage amount can be reduced.

FIG. 8 is a flowchart showing an AF (autofocus) sequence in a conventional camera.
In FIG. 8, when the AF is started in the process (701), first, an active ranging mode is set in (702), and in (703), it is checked whether the current ranging mode is active / passive. Nara (70
The process proceeds to 4), and if it is passive, the process proceeds to (705) to perform initial setting according to each ranging mode. After setting (706)
To execute the ICG mode. In the 1CG mode, a storage condition (setting of electronic shutter, drive frequency) for preventing the light receiving sensor 20 from being saturated at the time of storage by external light is determined.

When the storage setting is determined, the process proceeds to step (707) where the image signal is stored. By storing the number of rings and the driving frequency during the storage, the time required for the storage can be known. When signal accumulation is completed (70
Proceeding to 8), the signal accumulated by the light receiving sensor 20 is read into the microcomputer, and a distance measurement calculation for obtaining the subject distance from the image signal read in (709) is performed. This distance measurement operation is a method of calculating a shift amount at which two images coincide with each other while shifting two image signals called a correlation operation, and obtaining a subject distance from the shift amount. It is a thing using.

After the distance measurement calculation, the distance measurement mode is checked at (710). If the distance measurement mode is active, the process proceeds to (712). As a result of the distance measurement operation, it is checked whether the distance is OK or NG. In the case of (1), the process proceeds to (713), switches the distance measurement mode to passive, returns to (703), and performs the distance measurement again. If the active distance measurement is OK, the active distance measurement is adopted, and the process proceeds to (711) to end the AF. If the distance measurement mode is passive in (710), the distance measurement result obtained by the distance measurement calculation is adopted, and the process proceeds to (711) to end the AF.

The principle of the above-described correlation calculation will be briefly described with reference to FIGS. When the two image signals are a right image and a left image, and the distance measurement target is far from the distance measurement position, the left and right images are output in substantially the same positional relationship as shown in FIG.
When the object to be measured comes close as shown in (b) and (c),
The displacement between the left and right images is increased.

FIG. 10B shows the result of plotting the shift amount and the result of the logical product when two images as shown in FIG. 10A are obtained.

FIG. 11 is a flowchart for explaining the outline of the correlation operation. When the correlation operation for the distance measurement operation is started in (901), the pixel shift start value; Ms is set in (902). And (903) the end value of the pixel shift;
Me is set, and necessary RAM initialization is performed in (904).

Next, the right image is shifted by Ms in (905), and the logical product S of the left and right images is obtained in (906). FIG. 10B is a plot of the logical product obtained at this time together with the shift amount. Since the minimum value is the shift amount at which the left and right images coincide with each other, (907): The left and right images are compared to store the minimum value of the logical product in Smin, and when S is smaller than Smin, (90
Proceeding to 8), the value of S is substituted for Smin, and the shift amount at that time; Ms is stored in (909).

At (910), the shift amount Ms is incremented by one, and at (911), it is checked whether the shift amount has exceeded the set end value. If not, (90)
Returning to 5), the same operation is repeated.
Proceed to 2) to end the correlation calculation. As a result of this correlation operation, the subject distance can be known from the value of M (shift amount at which the logical product of the left and right images is minimized) stored in (909).

[0017]

In the above-described correlation operation in the distance measurement operation, the shift amount is smaller for a farther distance measurement object, and the shift amount is larger for a closer distance measurement object. Although the amount of shift increases when covering up to uniformly, since there is no means to know the distance to the target before performing the correlation operation, the distance must be obtained by shifting the entire range from short distance to long distance Therefore, there is a problem that it takes a long calculation time.

An object of the present invention is to solve the above-mentioned problem and shorten the distance measurement time.

[0019]

In a distance measuring apparatus according to the present invention, a light projecting means for projecting light toward an object to be measured, and a light receiving means for receiving reflected light from the object to be measured from the object to be measured. A pair of light receiving means for converting to an electric light receiving signal, a calculating means for performing a distance measurement operation using a predetermined value based on the light receiving signal of the pair of light receiving means, and a signal amplitude of the light receiving signal exceeds a set value. Detecting means for detecting that the signal amplitude exceeds the set value; measuring means for measuring the time until the signal amplitude exceeds the set value; and changing means for changing a predetermined value of the distance measurement calculation according to the measured time. I have.

In the computer-readable storage medium according to the present invention, a light projecting procedure for projecting light toward the object to be measured and a light reflected by the light emitted from the object to be measured are received by a pair of light receiving means. A light receiving procedure for converting the light receiving signal into an electrical light receiving signal; a calculating means for performing a distance measurement calculation using a predetermined value based on the light receiving signals from the pair of light receiving means; A detection procedure for detecting that the signal amplitude has exceeded, a measurement procedure for measuring a time until the signal amplitude exceeds the set value, and a change procedure and execution for changing a predetermined value of the distance measurement calculation according to the measured time. The program for performing is stored.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the present invention will be described in principle. Originally, when an image is formed on a light receiving sensor by reflected light of external light from a distance measurement target (subject) such as passive distance measurement, the distance of the distance measurement target is not known from the accumulation time, but active. In the case of distance measurement, since light is projected on a distance measurement target and an image is formed using the reflected light, the signal accumulation time varies depending on the intensity of the reflected light. In other words, if the signal accumulation time is short, the reflected light is strong, so it is determined that the object to be measured is near, the shift start value is increased, and if the signal accumulation time is long, the reflected light is strong. Since it is weak, it is determined that the object to be measured is far away, and the shift start value is reduced. In this embodiment, at the time of active ranging, the calculation time is reduced by judging the distance of the object to be measured from the change of the accumulation time of the signal and changing the start and end values of the shift amount. Features.

FIG. 1 is a block diagram showing the configuration of a camera to which the distance measuring apparatus of the present invention is applied. In FIG. 1, reference numeral 1 denotes an MPU for controlling the whole, which includes a microcomputer (not shown) having a RAM, an arithmetic unit, and a storage unit. 2 is the camera power supply
A main switch for N / OFF, a tele switch 3 for driving a camera barrel (not shown) to the tele side when the power of the camera is on, and a power switch for the camera 4
A wide switch 5 for driving the lens barrel to the wide side in the N state, and a preparation start switch 5 for starting preparation for photographing when the power of the camera is ON.
If N, preparation for photographing such as photometry and distance measurement is performed, and the photographing start switch is turned on. Reference numeral 6 denotes a winding-up switch for turning on the lens when the preparation start switch 5 is turned on.

Reference numeral 7 denotes a photometric sensor for measuring the external light luminance at the time of photographing, which includes a temperature sensor (not shown), and outputs a signal corresponding to the external light luminance to the MPU 1. 24 is skim CC
D, which is composed of a distance measuring sensor control unit 8 and a distance measuring sensor 9 for measuring the object distance during photographing. Reference numeral 10 denotes a shutter drive unit that controls the exposure time of the shutter using the photometric value obtained by the photometric sensor 7. Reference numeral 11 denotes a feed driving unit (not shown) for winding up one frame of the film after exposure, and reference numeral 12 denotes a lens barrel for driving a lens barrel to change a focal length by turning on a tele switch 3 or a wide switch 4. A driving unit 13 is a lens driving unit for driving a lens (not shown) to focus on a subject using the distance measurement result. 14 is an RO as a storage medium according to the present invention.
M, and stores a program including a process of the MPU 1 according to a flowchart of FIG. As the storage medium, a semiconductor memory, an optical disk, a magneto-optical disk, a magnetic medium, or the like is used.

FIG. 2 shows a basic configuration of a distance measuring system according to the present invention. In FIG. 2, the IRED 14 emits light to the subject 15. The light receiving sensor includes an A sensor 16 and a B sensor 17 arranged at a predetermined interval. The A sensor 16 and the B sensor 17 each include a photoelectric conversion element that receives reflected light of the subject 15 from the IRED 14 or external light reflected by the subject 15 and converts the light into an electric charge according to the amount of received light. The sensor outputs schematically show image outputs 18 and 19 when each sensor performs photoelectric conversion. The distance measurement method used in the present embodiment is a phase difference detection method for obtaining a subject distance from a phase difference between two sensor outputs using the principle of triangulation.

FIG. 3 shows the time required to accumulate a predetermined signal amount during active distance measurement and the distance from the object to be measured (object) at that time. Although the accumulation time differs, the accumulation time generally becomes shorter when the object to be measured is closer, and longer when the object is farther away.

FIG. 4 is a flow chart for explaining the outline of the correlation calculation, and shows the distance measurement calculation in a series of AF sequences described in the conventional example. In FIG. 4, when the correlation calculation for the ranging calculation is started in the process (301), the time required for accumulating a predetermined amount of signal is compared with the comparison value in (302), and the time is shorter than the time. If so, (303) sets the start shift amount Ms so as not to cover the infinite distance, and (304) sets the end shift amount Me to cover the close range. Next, in (302),
If the accumulation time is longer than the predetermined time, the start shift amount Ms is set to cover the infinite distance in (305),
In (306), the end shift amount that does not cover the close distance is set to Me. In (307), necessary RAM initialization is performed, and in (308), the right image is shifted by Ms.
In step 9), the logical product S of the left and right images is obtained.

At (310), a comparison is made to store the minimum value of the logical product of the left and right images in Smin. If S is smaller than Smin, the process proceeds to (311) and Smin is added to Smin.
And the shift amount Ms at that time is stored in (312). Next, the shift amount is incremented by one in (313), and it is checked in (314) whether the shift amount has exceeded the set end value. If not, (30)
Return to 8) and repeat the same operation.
Proceed to 5) to end the correlation calculation. As a result of the correlation operation, the subject distance can be known from the value of M (shift amount at which the logical product of the left and right images is minimized) stored in (312).

[0028]

As described above, according to the present invention, the distance to the object to be measured can be determined to some extent from the time until the signal is accumulated by a predetermined amount at the time of distance measurement. Since the predetermined value such as the shift amount used in the distance measurement calculation is appropriately changed, unnecessary correlation calculation can be omitted, thereby shortening the distance measurement time without impairing the distance measurement capability. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a camera to which a distance measuring device according to the present invention is applied.

FIG. 2 is a configuration diagram of a distance measuring system according to the present invention.

FIG. 3 is a characteristic diagram illustrating a relationship between a subject distance and a storage time until a predetermined signal amount is stored.

FIG. 4 is a flowchart illustrating a sequence of a correlation operation according to the present invention.

FIG. 5 is a configuration diagram illustrating the principle of a skim CCD.

FIG. 6 is a timing chart showing the operation of the skim CCD.

FIG. 7 is a characteristic diagram illustrating the amount of charge stored in the light receiving sensor.

FIG. 8 is a flowchart illustrating an outline of a distance measuring operation according to a conventional example and the present invention.

FIG. 9 is a waveform diagram showing an image waveform of a subject at a long distance, a medium distance, and a short distance.

FIG. 10 is a waveform diagram illustrating a pseudo waveform for explaining a correlation operation and a result of an AND operation when an image is shifted.

FIG. 11 is a flowchart illustrating a sequence of a correlation operation according to a conventional example.

[Explanation of symbols]

 1 MPU 7 Photometry sensor 8 Distance measurement control unit 9 Distance measurement sensor 14 IRED 15 Subject 16 A sensor 17 B sensor 18 A sensor output 19 B sensor output

Claims (8)

[Claims] 1. A light projecting means for projecting light toward a distance measuring object, and a pair of light receiving means for receiving reflected light from the light projecting from the distance measuring object and converting the reflected light into an electric light receiving signal. Calculating means for performing a distance measurement operation using a predetermined value based on the light receiving signals of the pair of light receiving means; detecting means for detecting that the signal amplitude of the light receiving signal exceeds a set value; A distance measuring device, comprising: a measuring means for measuring a time until a set value is exceeded; and a changing means for changing a predetermined value of the distance measurement calculation according to the measured time. 2. The distance measuring apparatus according to claim 1, wherein said distance measuring operation is a correlation operation. 3. The distance measuring apparatus according to claim 2, wherein the predetermined value of the distance calculation is a shift end value of the correlation operation. 4. The distance measuring apparatus according to claim 2, wherein the predetermined value of the distance calculation is a shift start value and an end value of the correlation calculation. 5. A light-projecting procedure for projecting light toward a distance-measuring object, and light reflected by the light-emitting from the distance-measuring object is received by a pair of light receiving means and converted into an electric light receiving signal. Light receiving procedure, calculating means for performing distance measurement calculation using a predetermined value based on the light receiving signals of the pair of light receiving means, and detecting procedure for detecting that the signal amplitude of the light receiving signal exceeds a set value, A computer readable program stored with a measurement procedure for measuring a time until the signal amplitude exceeds the set value, a change procedure for changing a predetermined value of the distance measurement calculation according to the measured time, and a program for executing the change procedure Storage media. 6. The computer-readable storage medium according to claim 5, wherein said distance measurement operation is a correlation operation. 7. The computer-readable storage medium according to claim 6, wherein the predetermined value of the distance measurement operation is a shift end value of the correlation operation. 8. The computer-readable storage medium according to claim 6, wherein the predetermined value of the distance calculation is a shift start value and an end value of the correlation calculation.