JP2007315782A - Distance measuring apparatus, distance measuring method, and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distance measuring apparatus having an expanded distance measurable range as compared to conventional ones. <P>SOLUTION: The distance measuring apparatus comprises a light emitting element for irradiating a reflecting object with light, a first light receiving element for outputting a first signal which is a signal corresponding to the light receiving position and light amount of the reflected light from the reflecting object, a second light receiving element which has lower light receiving sensitivity than that of the first light receiving element and outputs a second signal which is a signal corresponding to the intensity of the reflected light from the reflecting object, and a control section which, when receiving the first signal from the first light receiving element, calculates two different distances on the basis of the first signal as candidates for the distance between the light emitting element and the reflecting object, decides whether the second signal is received, and selects the shorter distance out of the two differences when the second signal is received and selects the longer distance out of the two distances when the second signal is not received. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a distance measuring device, a distance measuring method, and a projector for measuring a distance between two points.

  Some conventional cameras and projectors have an autofocus function. The autofocus function measures the distance to the object, moves the lens based on the obtained distance, and focuses. Below, an example of the ranging sensor used in order to measure the distance with a target object is demonstrated.

  The distance measuring sensor has an LED for emitting light to an object and a PSD (Position Sensitive Detector: position detecting element) for detecting reflected light from the object. The PSD has a rectangular detection area, and the output voltage of the PSD varies depending on the position and the amount of reflected light spot irradiated on the detection area. Then, the barycentric position of the spot in the detection region is obtained from the output voltage, and the distance between the distance measuring sensor and the object is calculated by the principle of triangulation using the barycentric position information (see Patent Document 1).

  FIG. 7 is a graph showing the relationship between the output voltage of the PSD and the distance. The horizontal axis represents distance, and the vertical axis represents PSD output voltage. The output voltage of a light receiving element such as PSD is referred to as a sensor output voltage. As shown in FIG. 7, the sensor output voltage increases rapidly until the distance between the two points of the distance measurement sensor and the object is almost zero until it reaches about 100 cm, but the distance between the two points is about 100 cm. If it exceeds, it will gradually decrease with changes in distance. Thus, the sensor output voltage has a “characteristic with aliasing” that changes from increasing to decreasing at a specific distance.

  Here, the reason why the PSD becomes the “characteristic with aliasing” will be described. If the distance between the two points of the distance measuring sensor and the object is too close, the reflected light spot is irradiated only toward the edge of the PSD detection area, and only a part of the spot is irradiated to the detection area. For this reason, even if the intensity of the spot light is strong, the amount of light applied to the detection region is small, and the sensor output voltage is small where the distance between the two points is close to zero. Subsequently, as the distance between the two points is gradually increased, the area of the spot irradiated to the detection area increases, the amount of light irradiated to the detection area gradually increases, and the sensor output voltage gradually increases. . The sensor output voltage becomes maximum when the distance between the two points is about 100 cm. After that, when the distance between the two points is further increased, the reflected light from the object becomes difficult to reach the detection region of the PSD, so that the amount of light irradiated to the detection region gradually decreases, and the sensor output voltage Gradually becomes smaller.

  In the example shown in FIG. 7, as a distance measurement possible range of the distance measurement sensor, a distance smaller than 100 cm is not used, and a range where the distance is 100 cm or more and 550 cm or less is used. The distance of 550 cm corresponds to an output voltage of 0.5 V, which is the detection limit of the sensor. Thereby, the relationship between the sensor output voltage and the distance becomes one-to-one, and the distance can be obtained according to the sensor output voltage.

Next, the autofocus function will be described. In addition to obtaining the relationship between the output voltage of the distance measuring sensor and the distance as described above, the relationship between the focus position and the distance is obtained in advance. Then, the sensor output voltage-focus position characteristic is obtained from the sensor output voltage-distance characteristic and the focus position-distance characteristic. FIG. 8 is a graph showing the relationship between the output voltage of the distance measuring sensor and the focus position. Each of the horizontal axis and the vertical axis takes a value converted by a predetermined formula. Based on the graph shown in FIG. 8, it is possible to focus by determining the focus position according to the output voltage of the distance measuring sensor.
JP 2005-331585 A

  As described with reference to FIG. 7, the output voltage of the conventional distance measuring sensor has a characteristic with aliasing. Therefore, in the example shown in FIG. 7, the range in which the distance between the two points of the distance measuring sensor and the object is 100 cm or more and 550 cm or less is set as the range that can be measured. When the distance measuring sensor as shown in this example tries to measure the distance even in the range where the distance between the two points is smaller than 100 cm, the following problem occurs.

  FIG. 9 is a graph for explaining the problems of the conventional distance measuring sensor. Assume that a projector provided with this distance measuring sensor is arranged so that the distance between the distance measuring sensor and the object is 50 cm. As shown in FIG. 9, the distance between the two points is 50 cm, which is the point A on the graph. The sensor output voltage at point A is 1.5V, and the sensor output voltage becomes 1.5V at point B in addition to point A. The sensor output voltage is the same at point A and point B.

  When the projector tries to obtain the distance between two points by the autofocus function, the sensor output voltage of 1.5V is detected by the distance measuring sensor. If the sensor output voltage value is recognized as the point B in the graph shown in FIG. 9, the distance between the two points is set to 200 cm and an attempt is made to focus. Here, since the distance between the two points is set to 50 cm corresponding to the point A of the graph, the focus cannot be achieved. When a sensor that detects whether or not the focus is finally achieved is provided, the sensor may operate forcibly and cause a malfunction.

  As described above, in the conventional distance measuring sensor, two distances are obtained for one value of the sensor output voltage. If you try to widen the range using a conventional distance sensor, the focus may or may not match depending on whether you select one of the two distances obtained from the sensor output voltage, and auto focus The problem that the function becomes unstable occurs.

  The present invention has been made in order to solve the above-described problems of the prior art, and provides a distance measuring device, a distance measuring method, and a projector that have a wider distance measurement range than in the past. Objective.

To achieve the above object, the distance measuring device of the present invention comprises:
A light emitting device for irradiating light on the reflector;
A first light receiving element that outputs a first signal that is a signal corresponding to a light receiving position and a light amount of reflected light from the reflector;
A second light receiving element that outputs a second signal that has a lower light receiving sensitivity than the first light receiving element and corresponds to the intensity of reflected light from the reflector;
When the first signal is received from the first light receiving element, two distances having different values are calculated based on the first signal as candidates for the distance between the light emitting element and the reflector. And determining whether or not the second signal is received. If the second signal is received, the shorter one of the two distances is selected, and the second signal is selected. If not received, a control unit that selects the longer of the two distances;
It is the structure which has.

  In the present invention, if the reflector is close to the light emitting element, light is detected by the second light receiving element, so the shorter distance is selected from the two distance candidates. On the other hand, if the reflector is far from the light emitting element, no light is detected by the second light receiving element, and therefore the longer distance is selected from the two distance candidates.

In addition, the distance measuring device of the present invention is
A light emitting device for irradiating light on the reflector;
A first light receiving element that outputs a first signal that is a signal corresponding to a light receiving position and a light amount of reflected light from the reflector;
A second light receiving element that outputs a second signal that has a lower light receiving sensitivity than the first light receiving element and corresponds to the intensity of reflected light from the reflector;
A threshold value serving as a reference for determining whether or not the second light receiving element has detected light is stored in advance, and when the first signal is received from the first light receiving element, the light emitting element and the reflection are reflected. Based on the first signal, two distances having different values are calculated as candidates for the distance between the object, the value based on the second signal is compared with the threshold value, and the distance based on the second signal is calculated. If the value is greater than or equal to the threshold, the shorter distance of the two distances is selected, and if the value of the second signal is smaller than the threshold, the longer distance of the two distances A control unit for selecting,
It is the structure which has.

  In the present invention, if the reflecting object is close to the light emitting element, the value of the signal received from the second light receiving element becomes greater than or equal to the threshold value, so the shorter distance is selected from the two distance candidates. . On the other hand, if the reflector is far from the light emitting element, the value of the signal received from the second light receiving element is smaller than the threshold value, so the longer one of the two distance candidates is selected. Further, since the threshold value is set in advance corresponding to the detection sensitivity of the second light receiving element, various light receiving elements can be used.

On the other hand, the projector of the present invention for achieving the above object is
A projection lens;
A focus adjustment unit that drives the projection lens in accordance with a received control signal;
A distance measuring sensor including a light emitting element for irradiating light on the reflector and a first light receiving element that outputs a first signal corresponding to a light receiving position and a light amount of the reflected light from the reflector;
A second light receiving element that outputs a second signal that is lower in light sensitivity than the first light receiving element and that corresponds to the intensity of reflected light from the reflector;
When the first signal is received from the first light receiving element, two distances having different values are calculated based on the first signal as candidates for the distance between the light emitting element and the reflector. And determining whether or not the second signal is received. If the second signal is received, the shorter one of the two distances is selected, and the second signal is selected. A control unit that selects a longer one of the two distances and transmits a control signal corresponding to the selected distance to the focus adjustment unit;
It is the structure which has.

In addition, the distance measuring method of the present invention for achieving the above object includes a light emitting element for irradiating light on a reflecting object, and a signal corresponding to a light receiving position and a light amount of reflected light from the reflecting object. A distance measuring sensor including a first light receiving element that outputs a signal and a control unit that calculates a distance between the light emitting element and the reflecting object based on a signal received from the first light receiving element. A distance method,
A second light receiving element that outputs a second signal that is lower in light sensitivity than the first light receiving element and that corresponds to the intensity of reflected light from the reflector;
The controller is
When the first signal is received from the first light receiving element, two distances having different values are calculated based on the first signal as candidates for the distance between the light emitting element and the reflector. ,
It is determined whether or not the second signal is received, and when the second signal is received, the shorter one of the two distances is selected and the second signal is received. If not, the longer of the two distances is selected.

  According to the present invention, the distance range in which the autofocus function can operate can be expanded. Conventionally, the distance can be measured even at a distance that may cause a malfunction of the autofocus function.

  The distance measuring device of the present invention is characterized in that a light receiving element having a low detection sensitivity is newly provided, and a correct value can be selected from a measurement result of the distance measuring sensor based on a detection value of the light receiving element.

  The configuration of the distance measuring apparatus according to the present embodiment will be described. In this embodiment, it is assumed that the distance measuring device is provided in the projector.

  FIG. 1 is a block diagram illustrating a configuration example of a projector according to the present embodiment. FIG. 2 is a block diagram showing the main part of the distance measuring apparatus.

  As shown in FIG. 1, the projector 1 includes a projection lens 11, a focus adjustment unit 12, a distance measuring sensor 14, a control unit 10, and an operation unit 15. The projector 1 according to the present embodiment is provided with a light receiving element 27 having a light receiving sensitivity lower than that of PSD. In this embodiment, a phototransistor is used as the light receiving element 27. The control unit 10 includes a CPU (Central Processing Unit) 21 that executes predetermined processing according to a program, and a memory 22 that stores the program.

  Although not shown in the figure, the projector 1 includes a light source, a display device typified by a liquid crystal device that partially reflects or transmits a light beam from the light source, and image processing (A Functions as a projector, such as an image processing unit that performs D / D conversion, synchronization signal separation, and writing and reading of image data to and from a frame memory, and a drive unit that drives a display device based on image data from the image processing unit A configuration for realizing the above is provided. Since these structures are the same as those of the prior art, detailed description thereof is omitted.

  The projection lens 11 has a plurality of lenses for projecting an image formed by the light valve onto the screen 2. The focal position on the screen 2 can be adjusted by moving at least some of the lenses back and forth along the optical axis. As a mechanism capable of adjusting the focal position, various mechanisms such as a mechanism that moves the entire projection lens 11 and a mechanism that moves a part of the projection lens 11 can be applied. A widely used mechanism that can move the position of the focus lens of the projection lens is used.

  The focus adjustment unit 12 has a lens motor for moving the lens in the projection lens 11, and drives the lens motor in accordance with a control signal from the control unit 10.

  The operation unit 13 is provided with a plurality of operation buttons and switches for operating the projector 1. The plurality of operation buttons include a focus button for operating the autofocus function.

  As shown in FIG. 2, the distance measuring sensor 14 is for measuring the distance from the front surface (projection lens 11) of the projector 1 to the screen 2. The distance measuring sensor 14 is configured to include an LED 25 serving as a light emitting element and a PSD 26 serving as a light receiving element. The LED 25 radiates infrared rays, and the PSD 26 detects the reflected light from the screen 2 as a reflector. The output of the PSD 26 is input to the control unit 10.

  When the light receiving element 27 detects the reflected light of the LED 25, the light receiving element 27 outputs a signal corresponding to the intensity of the reflected light. FIG. 3 is a graph showing the relationship between the sensor output voltage of the light receiving element 27 and the distance. FIG. 3 shows the characteristics of the PSD 26 for comparison.

  If the distance between the LED 25 and the screen 2 is too short, most of the light reflected on the screen 2 is irradiated near the LED 25, and the reflected light does not reach the light receiving element 27. As shown in FIG. The sensor output voltage is close to zero. When the distance between the LED 25 and the projector 1 is gradually increased, the light reflected on the screen 2 is gradually irradiated onto the light receiving element 27, and the sensor output voltage of the light receiving element 27 increases. Further, when the screen 2 is moved away from the projector 1, the light receiving element 27 has a light receiving sensitivity lower than that of the PSD 26, so that the sensor output voltage has a maximum value in the vicinity of a distance of 50 cm and then decreases as the distance becomes longer. In the vicinity of the distance of 100 cm, the sensor output voltage of the light receiving element 27 becomes the detection limit of 0.5V.

  When the focus button of the operation unit 15 is pressed, the CPU 21 of the control unit 10 causes the LED 25 of the distance measuring sensor 14 to emit light. When the signal from the PSD 26 is received, two candidate distances between the screen 2 and the projector 1 are calculated by the principle of triangulation based on the value of the sensor output voltage based on the signal from the PSD 26 as in the conventional case. . When the two distances are obtained, it is determined whether or not a signal is received from the light receiving element 27. As a result of the determination, when a signal is received from the light receiving element 27, the shorter one of the two distances is selected. On the other hand, when no signal is received from the light receiving element 27, the longer one of the two distances is selected. Thereafter, in response to the determined distance, a control signal for driving the lens motor is transmitted to the focus adjustment unit 12 in order to move the lens in the projection lens 11.

  FIG. 4 is a graph showing the distance measurement possible range of the distance measuring apparatus of the present embodiment. As shown in FIG. 4, the distance measurement possible range of the present embodiment is within the range of the characteristic 1 corresponding to the longer distance than the distance of 100 cm at which the distance between the two points is the maximum value of the sensor output voltage of the PSD 26. The range of the characteristic 2 corresponding to the distance shorter than the distance of 100 cm is not limited. The range of the characteristic 2 is expanded as compared with the conventional range.

  Next, a distance measuring method using the distance measuring apparatus of the present embodiment will be described. FIG. 5 is a schematic diagram for explaining the distance measuring method of this embodiment. The reflector 20 shown in FIG. 5 corresponds to the screen 2. FIG. 6 is a flowchart showing the procedure of the distance measuring method of this embodiment.

  When the focus button of the operation unit 15 is pressed, the control unit 10 causes the LED 25 of the distance measuring sensor 14 to emit light. Thereafter, when a signal from the PSD 26 is received, the distance between the reflector 20 and the projector 1 is calculated by the principle of triangulation as in the conventional case (step 101). When the two distances are obtained, it is determined whether or not a signal is received from the light receiving element 27 (step 102). If the signal is received from the light receiving element 27 as a result of the determination, the shorter one of the two distances is selected (step 103). On the other hand, when no signal is received from the light receiving element 27, the longer one of the two distances is selected (step 104).

  The distance measuring method of the present embodiment will be described using the schematic diagram of FIG. FIG. 5 shows two cases where the reflector 20 is arranged near the distance measuring sensor 14 and when the reflector 20 is arranged far from the distance sensor 14.

  When the reflector 20 is disposed near the distance measuring sensor 14, the infrared light emitted from the LED 25 is input to the PSD 26 along a broken line path. In step 101, two distances are calculated as candidates from the characteristic 1 and characteristic 2 of the graph shown in FIG. Further, infrared light reflected by the reflector 20 is input to the light receiving element 27 through the optical path 1. In this case, since the distance between the reflector 20 and the projector 1 is short, the intensity of infrared light input to the light receiving element 27 is strong, and the light receiving element 27 detects light and sends a signal corresponding to the sensor output voltage to the control unit 10. Send. Therefore, the control unit 10 selects the characteristic 1 of the graph shown in FIG. 4 and determines the shorter one of the two distances (step 103).

  On the other hand, when the reflector 20 is arranged far away from the distance measuring sensor 14, the infrared light emitted from the LED 25 is input to the PSD 26 along a solid line. In step 101, two distances are calculated as candidates from the characteristic 1 and characteristic 2 of the graph shown in FIG. Further, the infrared light reflected by the reflector 20 is input to the light receiving element 27 through the optical path 2. In this case, since the distance between the reflector 20 and the projector 1 is long, the intensity of infrared rays input to the light receiving element 27 is weak, and the light receiving element 27 cannot detect light. Therefore, the light receiving element 27 does not send a signal to the control unit 10. Therefore, the control unit 10 selects the characteristic 2 in the graph shown in FIG. 4 and determines the longer one of the two distances (step 104).

  After determining the distance between the reflector 20 and the projector 1 as described above, the control unit 10 moves the lens motor in order to move the focus lens in the projection lens 11 in accordance with the determined distance. A control signal for driving is transmitted to the focus adjustment unit 12.

  By using both the characteristics 1 and 2 of the graph shown in FIG. 4 according to the distance measuring method of this embodiment, and making it possible to use a distance measuring range that has not been used in the past, the autofocus operation The possible distance range can be expanded. In addition, it is possible to prevent the occurrence of malfunction and measure the distance even at a distance that may cause malfunction in the autofocus function using the conventional distance measuring sensor as it is.

  In the present embodiment, the light receiving element 27 is configured separately from the distance measuring sensor 14, but the distance measuring sensor 14 may include the light receiving element 27.

  In the present embodiment, the light receiving element 27 does not output a signal when it is below the detection limit. However, based on the signal received from the light receiving element 27, whether or not the light receiving element 27 has detected light is controlled. 10 may be determined. A threshold value serving as a reference for determining whether or not the light receiving element 27 has detected light is stored in the memory 22 of the control unit 10 in advance. And when CPU21 receives a signal from the light receiving element 27, it will determine whether the value by the received signal is more than a threshold value. If the value based on the received signal is equal to or greater than the threshold, the shorter one of the two distances is selected, and if the value is smaller than the threshold, the longer one of the two distances is selected. By setting a threshold value in advance corresponding to the detection limit value of the light receiving element and allowing the control unit 10 to determine whether or not the light receiving element has detected light, it is possible to apply many types of light receiving elements. Become.

  In addition, by using a distance measuring sensor with a short distance measurement instead of a phototransistor, it is possible to measure a short distance more accurately, and in combination with this, it is possible to function autofocus more accurately. It becomes.

  Furthermore, the distance measuring device of the present invention can be applied not only to a projector but also to a camera. Furthermore, in the apparatus and method for obtaining the distance between two points, the present invention can be applied not only to a projector and a camera.

It is a block diagram which shows the example of 1 structure of the projector of a present Example. It is a block diagram which shows the principal part of the distance measuring device of a present Example. It is a graph which shows the output characteristic of the light receiving element used for a present Example. It is a graph which shows the distance measurement possible range of the distance measuring device of a present Example. It is a schematic diagram for demonstrating the ranging method of a present Example. It is a flowchart which shows the procedure of the ranging method of a present Example. It is a graph which shows the measurable range of the conventional ranging sensor. It is a graph which shows the characteristic of ranging sensor output voltage-focus position. It is a graph for demonstrating the problem of the conventional ranging sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Projector 10 Control part 11 Projection lens 12 Focus adjustment part 14 Distance sensor 25 LED
26 PSD
27 Light receiving element

Claims (4)

A light emitting device for irradiating light on the reflector;
A first light receiving element that outputs a first signal that is a signal corresponding to a light receiving position and a light amount of reflected light from the reflector;
A second light receiving element that outputs a second signal that has a lower light receiving sensitivity than the first light receiving element and corresponds to the intensity of reflected light from the reflector;
When the first signal is received from the first light receiving element, two distances having different values are calculated based on the first signal as candidates for the distance between the light emitting element and the reflector. And determining whether or not the second signal is received. If the second signal is received, the shorter one of the two distances is selected, and the second signal is selected. If not received, a control unit that selects the longer of the two distances;
Ranging device having A light emitting device for irradiating light on the reflector;
A first light receiving element that outputs a first signal that is a signal corresponding to a light receiving position and a light amount of reflected light from the reflector;
A second light receiving element that outputs a second signal that has a lower light receiving sensitivity than the first light receiving element and corresponds to the intensity of reflected light from the reflector;
A threshold value serving as a reference for determining whether or not the second light receiving element has detected light is stored in advance, and when the first signal is received from the first light receiving element, the light emitting element and the reflection are reflected. Based on the first signal, two distances having different values are calculated as candidates for the distance between the object, the value based on the second signal is compared with the threshold value, and the distance based on the second signal is calculated. If the value is greater than or equal to the threshold, the shorter distance of the two distances is selected, and if the value of the second signal is smaller than the threshold, the longer distance of the two distances A control unit for selecting,
Ranging device having A projection lens;
A focus adjustment unit that drives the projection lens in accordance with a received control signal;
A distance measuring sensor including a light emitting element for irradiating light on the reflector and a first light receiving element that outputs a first signal corresponding to a light receiving position and a light amount of the reflected light from the reflector;
A second light receiving element that outputs a second signal that is lower in light sensitivity than the first light receiving element and that corresponds to the intensity of reflected light from the reflector;
When the first signal is received from the first light receiving element, two distances having different values are calculated based on the first signal as candidates for the distance between the light emitting element and the reflector. And determining whether or not the second signal is received. If the second signal is received, the shorter one of the two distances is selected, and the second signal is selected. A control unit that selects a longer one of the two distances and transmits a control signal corresponding to the selected distance to the focus adjustment unit;
Projector. A distance measuring sensor including a light emitting element for irradiating light on a reflecting object, and a first light receiving element that outputs a first signal corresponding to a light receiving position and a light amount of reflected light from the reflecting object; A distance measuring method using a distance measuring device having a control unit that calculates a distance between the light emitting element and the reflecting object based on a signal received from a first light receiving element,
A second light receiving element that outputs a second signal that is lower in light sensitivity than the first light receiving element and that corresponds to the intensity of reflected light from the reflector;
The controller is
When the first signal is received from the first light receiving element, two distances having different values are calculated based on the first signal as candidates for the distance between the light emitting element and the reflector. ,
It is determined whether or not the second signal is received, and when the second signal is received, the shorter one of the two distances is selected and the second signal is received. If not, a distance measuring method of selecting a longer one of the two distances.

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