JP2005055617A - Projector, its focusing method, and its focusing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector capable of performing alignment to a focusing point with good accuracy by eliminating the influence of noise. <P>SOLUTION: A photodetecting sensor 21 receives the reflected light of the image projected from a projection lens optical system 8 onto a screen and outputs the signal depending on the amount of the received light of the reflected light. A rounding-off operation part 22d of an operation part 22 substitutes the value of the signal off the range with the value within the range in such a manner that the value of the signal from the photodetecting sensor 21 attains the value within the range. The contrast value of the image is calculated by subjecting the signal after the processing by the rounding-off operation part 22d to integration by an integrator 22e. The calculated contrast value is formed of the signal removed of the noise component and therefore the focusing position of the image can be specified with the good accuracy. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a projector that obtains a focus position using reflected light of an image projected on a screen while moving a projection lens optical system, and focuses the image projected on the screen, and a focus adjustment method thereof, and It relates to the focus adjustment program.

  In a projector that projects an image on a screen, it is desired to accurately focus the image projected on the screen in order to improve the convenience of the projector.

  As one method of focusing the image, paying attention to the fact that the contrast value of the input image signal corresponds to the definition of the reproduced image, the position of the projection lens is adjusted so that the contrast value is maximized. There is known an automatic focusing method that matches the above.

  The automatic focus adjustment method disclosed in Patent Document 1 will be described. The invention disclosed in Patent Document 1 is an invention related to an imaging apparatus, and as shown in FIG. 9, a main lens 101, a focus lens 102, a diaphragm shutter 103, a focus motor 104, a reset switch 105, A photoelectric conversion element 106, an imaging circuit 107, an arithmetic circuit 108, a CPU 109, and a mode change switch 110 are included.

  The focus lens 102 for moving the subject image on the photoelectric conversion element 106 is moved so that the focal length continuously changes from the infinity position to the nearest position. The subject image formed on the photoelectric conversion element 106 by the focus lens 102 is converted into an electric signal by the photoelectric conversion element 106, and the electric signal is converted into a luminance signal suitable for the arithmetic circuit 108 in the subsequent stage by the imaging circuit 107. The luminance signal is input to the arithmetic circuit 108, and a focus evaluation value is obtained. FIG. 9 shows a focus evaluation value when the focus lens 102 is moved so that the focal length continuously changes from the infinity position to the nearest position. The focus evaluation value represents the level of contrast, and it can be said that the higher the focus evaluation value, the higher the definition of the image.

Japanese Patent Application Laid-Open No. 8-1866752.

  However, in the focus evaluation value obtained when the invention of Patent Document 1 is applied to a projector and the focus lens is continuously changed, a plurality of peak values due to noise appear as shown in FIG. It is not a symmetrical mountain. When the focal point is detected using such a focal point evaluation value, a peak value that is not the focal point formed by the noise component may be erroneously determined as the focal point. In the example shown in FIG. 11, the peak position Q far from the in-focus position P is mistaken as the maximum focus evaluation value.

  Since Patent Document 1 is an invention related to an imaging apparatus, a factor that affects the focus evaluation value is that the luminance of external light such as a fluorescent lamp is not constant. However, in the case of a projector, in addition to the influence of external light, the influence of an air cooling fan that dissipates heat inside the apparatus must be taken into consideration. If the projector does not provide a sufficient cooling effect with natural heat radiation alone, the air around the parts generating heat is forced to convection using an air cooling fan, or the heat inside the system is exhausted to the outside. doing. However, the vibration of the air cooling fan is transmitted to the projection lens that projects the image on the screen, and the image projected on the screen is disturbed. Therefore, the focus evaluation value measured by the reflected light of the projected image is also affected.

  In addition, when various electric / electronic devices are connected to the AC power source to which the projector is supplied with power, noise generated from these devices is ridden. In addition, the power supply waveform itself is often distorted due to fluctuations in the power consumption of each device connected to the AC power supply. Therefore, the light amount of the projector that emits light upon receiving this power supply is not constant due to these effects.

  In addition, when a fluorescent lamp is used as the illumination device, the luminance of the fluorescent lamp is not constant, so that the amount of light received by the photoelectric conversion element varies depending on whether the fluorescent lamp is bright or dark. For example, when the image projected from the projection lens is received by the light receiving sensor when the brightness of the fluorescent lamp is lowered and the surroundings are dark, the output of the light receiving sensor is also lowered. On the contrary, when the image projected from the projection lens is received by the light receiving sensor when the brightness of the fluorescent lamp is increased and the surroundings are bright, the output of the light receiving sensor is also increased. These errors appear as noise in the focus evaluation value.

  The present invention has been made in view of the above circumstances, and provides a projector, a focus adjustment method thereof, and a focus adjustment program thereof that can accurately perform positioning at a focal point by eliminating the influence of noise. With the goal.

  In order to achieve this object, a projector according to claim 1 receives a reflected light of an image projected on a screen by a projection device and outputs a signal corresponding to the amount of received light, and a value of the signal. A calculation unit that replaces the value of the signal outside the range with a value within the range so that the value falls within a preset range, performs a calculation based on the replaced signal, and outputs the contrast value of the image; The optical system of the projection apparatus is driven and controlled to adjust the focal length of the image projected on the screen, and the position of the optical system where the contrast value of the image is maximized is detected to focus the projection apparatus. And a control unit for aligning with the position.

  The projector according to claim 1, wherein a range of a signal level output from the light receiving element when there is no noise component is obtained in advance, and the signal on which the noise component rides when the signal output from the light receiving element is not within this range. It is determined that And the process which replaces the value outside a range in a range is performed. An image contrast value is calculated by performing an operation on the signal thus obtained. Since the calculated contrast value is generated from the signal from which the noise component is removed, a plurality of peak values due to the noise component do not appear, and the in-focus position can be specified with high accuracy.

  According to a second aspect of the present invention, there is provided a method for adjusting a focal point of a projector, wherein a focal length adjusting step of adjusting an focal length of an image projected on a screen by driving and controlling an optical system of the projection device, A reflected light amount measuring step in which reflected light of the received image is received by a light receiving element, and a signal corresponding to the amount of received light is output, and the value of the signal outside the range so that the value of the signal is within a preset range Is replaced with a value within the range, a calculation is performed based on the replaced signal, and the contrast value of the image is output, and the position of the optical system where the contrast value of the image is maximum is detected. And a focal position detection step.

  The focus adjustment method for a projector according to claim 2, wherein a range of a signal level output from the light receiving element when there is no noise component is obtained in advance, and a noise component when the signal output from the light receiving element is not within this range. Is determined to be a signal on board. And the process which replaces the value outside a range in a range is performed. An image contrast value is calculated by performing an operation on the signal thus obtained. Since the calculated contrast value is generated from the signal from which the noise component is removed, a plurality of peak values due to the noise component do not appear, and the in-focus position can be specified with high accuracy.

  The focus adjustment program for a projector according to claim 3 is projected onto the screen by a focal length adjustment process for adjusting the focal length of an image projected on the screen by driving and controlling the optical system of the projection device. The reflected light of the received image is received by the light receiving element, and a reflected light amount measurement process for outputting a signal corresponding to the amount of received light, and the value of the signal outside the range so that the value of the signal falls within a preset range. Is replaced with a value within the range, a calculation is performed based on the replaced signal, and the contrast value of the image is output, and the position of the optical system where the contrast value of the image is maximum is detected. And a focal position detection process.

  The projector focus adjustment program according to claim 3 obtains in advance a range of signal levels output from the light receiving element when there is no noise component, and the noise component when the signal output from the light receiving element is not within this range. Is determined to be a signal on board. And the process which replaces the value outside a range in a range is performed. The contrast value of the image is calculated by calculating the signal thus obtained. Since the calculated contrast value is generated from the signal from which the noise component is removed, a plurality of peak values due to the noise component do not appear, and the in-focus position can be specified with high accuracy.

  According to the present invention, since the contrast value of the image is generated from the signal from which the noise component generated by the light source of the projector, the external light, and the air cooling fan of the projector is removed, the focal position can be accurately identified from the contrast value. .

  Next, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the projector 2 of the present embodiment receives reflected light of an image projected on the screen 1 by the projection lens optical system 8 and outputs a contrast value for determining the focal length of the image. And a first and second line-type passive distance measuring devices 3 and 4 for accurately measuring the relative inclination angle of the screen 1 with respect to the projector 2 in a horizontal plane and a vertical plane. Yes.

  Further, the control circuit 5 shown in FIG. 1 inputs image data from an automatic focus detection device 20, the first and second line type passive distance measuring devices 3 and 4, and a device such as a personal computer (not shown) to obtain image information. In order to change the focal length of the projection lens optical system 8, and the projection lens optical system 8 along the optical axis. And an optical system driving unit 23 composed of a stepping motor or the like for moving the lens.

  The control circuit 5 adjusts the focal length of the image projected on the screen 1 by controlling the optical system driving unit 23 that drives the projection lens optical system 8. Further, the control circuit 5 determines the horizontal direction of the screen 1 relative to the projector 2 and the output from the calculation unit 32 of the first line type passive distance measuring device 3 and the calculation unit 42 of the second line type passive distance measuring device 4. The relative inclination angle in the vertical direction is calculated. The control circuit 5 also controls the projection image generation unit 6 and the display driving unit 7 so as to correct the trapezoidal distortion based on the calculated tilt angle, and enlarges the image projected on the top, bottom, left and right of the screen 1. Reduce.

  The memory unit 10 stores data and commands necessary for the configuration of the projector 2, and supplies data and commands to the control circuit 5, the calculation unit 22, the calculation units 32 and 42, and the like as necessary. Receive data. The memory unit 10 has two types of memory devices such as a non-volatile flash memory and a volatile RAM, and stores necessary data and instructions and data used for a long time in the non-volatile memory device. Store data that is only used temporarily in a volatile memory device.

  The automatic focus detection device 20 is based on a light receiving sensor 21 that receives reflected light on the screen 1 of an image projected on the screen 1 by the projection lens optical system 8 and an electric signal output from the light receiving sensor 21. And a calculation unit 22 that performs calculation and outputs the contrast value of the image. As the light receiving sensor 21, a CCD line sensor or the like can be applied.

  The calculation unit 22 of the automatic focus detection apparatus 20 will be described with reference to FIG. As shown in FIG. 2, the calculation unit 22 includes a high-pass filter (HPF) 22 a that extracts a high-frequency component from the electric signal input from the light-receiving sensor 21, and a detector that performs amplitude detection of the luminance signal that includes only the high-frequency component. 22b, the A / D converter 22c that converts the detection output of the detector 22b into a digital signal, and the digital signal after the A / D conversion has a value within a preset range. , A rounding operation unit 22d for replacing a value outside the range with a value within the range, and an integrator 22e for integrating the signal after the rounding processing by the rounding operation unit 22d. The integrator 22e outputs a contrast value of the image signal as shown in FIG.

  As shown in FIG. 10, the contrast value appearing in the high-frequency component of the image signal has a characteristic that the contrast value becomes maximum at the in-focus position and decreases as the position deviates from the in-focus position. . Using this characteristic, the present embodiment detects the position (focus position) of the projection lens optical system 8 when the image projected by the projection lens optical system 8 forms an image on the screen 1.

  More specifically, first, an autofocus image pattern is projected from the projection lens optical system 8 onto the screen 1. The projection lens optical system 8 is moved at a constant speed from the initial position shown in FIG. 10 by the optical system driving unit 23, and is moved to the nearest position shown in FIG. The initial position is the position of the projection lens optical system 8 at which the focus (focus position) of the image projected by the projection lens optical system 8 is infinity, and the nearest position is the projection lens optical system 8. Is the position of the projection lens optical system 8 that can focus on the position closest to the projector 2. The reflected light projected from the projection lens optical system 8 moving at a constant speed and reflected by the screen 1 is received by the light receiving sensor 21 and an electric signal corresponding to the amount of light received by the light receiving sensor 21 is output. The calculation unit 22 calculates the electric signal output from the light receiving sensor 21 and calculates the contrast value of the image every predetermined time. Since the calculated contrast value becomes the maximum value when the projection light forms an image on the screen 1, the contrast value output from the calculation unit 22 is compared by the control circuit 5, so that the contrast value becomes the maximum. Can be detected.

  However, the contrast value measured by continuously moving the projection lens optical system 8 from the initial position to the nearest position includes a plurality of peak values due to noise components as shown in FIG. When the focal point is detected using such a contrast value, a peak value that is not the focal point formed by the noise component may be erroneously determined as the focal point. In the example shown in FIG. 11, the peak position Q far from the in-focus position P is mistaken as the place where the contrast value is maximum.

  As described above, the noise component is added to the contrast value because the light quantity of the projector's light source is not constant, the brightness of the external light is not constant, and the vibration caused by the air cooling fan provided in the projector projects the image onto the screen. The image is transmitted to the projection lens optical system 8 and is projected on the screen 1 to be disturbed.

  For this reason, in the present embodiment, a rounding process is performed on a signal output from the light receiving sensor 21 in accordance with the amount of reflected light of the projected image to remove a noise component. Specifically, a rounding process is performed by a rounding calculation unit 22d of the calculation unit 22 shown in FIG. The rounding operation unit 22d compares the value of the digital cell data output from the A / D converter 22c with a preset maximum value (hereinafter referred to as a set maximum value). The cell data value is compared with a preset minimum value (hereinafter referred to as a set minimum value). When the value of the digital cell data is larger than the set maximum value, the cell data from the corresponding cell is replaced with the set maximum value. When the cell data value is smaller than the set minimum value, the cell data value from the corresponding cell is replaced with the set minimum value.

  The set maximum value and the set minimum value are a range of signal levels output from the light receiving sensor 21 in a state where no noise component is present or as close to zero as possible. When the signal output from the light receiving sensor 21 is not within this range, it is determined that the signal has a noise component. And the process which replaces the value outside a range in a range is performed. FIG. 3 shows a state in which a rounding process is performed on a signal output from each cell of the light receiving sensor 21 and subjected to A / D conversion by the A / D converter 22c.

  The integrator 22e shown in FIG. 2 performs an integration operation on the signal from which the noise component has been removed by the above procedure to calculate an image contrast value. Since the calculated contrast value is a contrast value generated based on the signal from which the noise component has been removed, a plurality of peak values due to noise do not appear as shown in FIG. As shown in FIG. 5, the contrast value having the largest value at the in-focus point is measured.

  Therefore, the image projected on the screen 1 can be accurately focused from the calculated contrast value of the image.

  The procedure for specifying the in-focus position will be described with reference to the flowcharts shown in FIGS. First, the procedure for calculating the contrast value by the automatic focus detection device 20 will be described with reference to the flowchart shown in FIG. After the projector 2 is turned on, an automatic focus adjustment operation is started. First, the projection lens optical system 8 is driven to the initial position by the optical system driving unit 23, and the storage area (register) of the control circuit 5 for storing data and the calculation unit 22 is initialized (step S1). The information to be initialized includes a timer value for measuring time, a contrast value (cont) calculated by the calculation unit 22, and cell data output and recorded from each cell constituting the light receiving sensor 21 [ k]. In this embodiment, the feeding time Ts during which the projection lens optical system 8 moves at a constant speed from the initial position to the nearest position by the optical system driving unit 23 such as a step motor is set in advance. To do.

  Next, an image pattern for autofocus suitable for automatic focus adjustment stored in advance in the projector 2 is projected onto the screen 1 by the projection lens optical system 8 (step S2).

  Next, a timer for measuring the moving time of the projection lens optical system 8 is activated, and the optical lens drive unit 23 moves the projection lens optical system 8 from the initial position (position where the focal length is infinite) at a constant speed ( Feeding out). At the same time, the reflected light of the image pattern projected on the screen 1 is received by the light receiving sensor 21 (step S3). The light receiving sensor 21 outputs a signal corresponding to the amount of reflected light received to the subsequent calculation unit 22 (step S4). The signal from the light receiving sensor 21 is subjected to filter processing, A / D conversion processing, and the like by the arithmetic unit 22, and digital cell data is output (step S6).

  The rounding calculator 22d of the calculator 22 first compares whether or not the value of the cell data output from each cell of the light receiving sensor 21 is smaller than a preset minimum value (step S7). If the cell data value is smaller than the preset minimum value (step S7 / YES), the cell data value from the corresponding cell is replaced with the preset minimum value (step S8). If the value of the cell data is larger than the preset minimum value set in advance (step S7 / NO), the cell data from the corresponding cell is output as it is to the integrator 22e at the subsequent stage.

  Next, the rounding calculation unit 22d compares whether or not the value of the cell data is larger than a preset maximum value. If the cell data value is larger than the preset maximum value (step S9 / YES), the cell data value from the cell is replaced with the preset maximum value (step S10). Also. When the value of the cell data is smaller than the preset maximum position set in advance (step S9 / NO), the cell data from the corresponding cell is output as it is to the subsequent integrator 22e.

  When the above-described procedure is repeated (steps S11 and S12 / NO) and the comparison with the set minimum value and the set maximum value of the cell data from each cell of the light receiving sensor 21 is completed (step S12 / YES), the integrator 22e. Is used to calculate the contrast value of the image.

  Next, a procedure for specifying the in-focus position with reference to the contrast value of the image will be described with reference to the flowchart shown in FIG. When the contrast value of the image is calculated by the calculation unit 22 (step S21), the control circuit 5 compares whether or not the calculated contrast value is larger than the Max_cont value (step S22). Note that the Max_cont value is the maximum value among the previously measured contrast values. When the calculated contrast value is larger than the Max_cont value (step S23 / YES), this contrast value is recorded as the Max_cont value, and the time T [i] when the contrast value is measured is recorded (step S23). ). If the calculated contrast value is not larger than the Max_cont value (step S22 / NO), all the data relating to the contrast value is erased, and the processing for the contrast value is ended.

  When the comparison between the calculated contrast value and the Max_cont value is completed, the movement position of the projection lens optical system 8 is confirmed. Since the time Ts required for moving the projection lens optical system 8 from the initial position shown in FIG. 10 to the nearest position at a constant speed is known in advance, the timer value of the timer is compared with Ts, and the projection lens optical system 8 is moved to the nearest position. It is determined whether or not it has reached (step S24). When the projection lens optical system 8 has not reached the latest position (when the timer value has not reached Ts) (step S24 / NO), the procedure of steps S4 to S12 in the flowchart shown in FIG. 4 is repeated. The rounding process of the cell data and the calculation of the contrast value of the image from the rounded cell data are performed.

  When the timer value of the timer becomes Ts and the projection lens optical system 8 has moved to the nearest position (measurement is completed from the initial position of the contrast value to the nearest position) (step S24 / YES), the time taken to move to the nearest position The movement time Tr to the Max_cont position held from Ts is subtracted to obtain the movement time Tr to the in-focus position (step S25). Since the projection lens optical system 8 has finished the measurement and moved from the initial position to the nearest position, the movement time Tr for moving from the nearest position to the in-focus position specified is calculated. The projection lens optical system 8 can be moved to the in-focus position by moving the projection lens optical system 8 from the nearest position in the reverse direction (from the nearest position to the initial position) for the obtained time Tr.

  As described above, in this embodiment, the range of the signal level output from the light receiving sensor 21 in a state in which the noise component is not present or as close to zero as possible is registered, and the signal output from the light receiving sensor 21 is within this range. If it is not within, it is determined that the signal has a noise component. The contrast value is calculated by replacing the output of the light receiving sensor 21 with a value from which noise is removed. Therefore, the image projected on the screen 1 can be accurately focused from the calculated contrast value of the image.

  In the present embodiment, the rounding processing unit 22d performs rounding processing on the cell data output from each cell of the light receiving sensor 21, as in the first embodiment. The rounding process is a process of replacing cell data larger than a preset maximum value with a preset maximum value and replacing cell data smaller than a preset minimum value with a preset minimum value. A rounding process is performed by the rounding calculator 22d, and the contrast value of the image is calculated from the integrator 22e at regular intervals from the signal from which the noise component has been removed.

  The control circuit 5 compares the contrast value output from the integrator 22e with a preset threshold value. This threshold value is used to extract only a contrast value above a certain value. When a contrast value greater than the threshold value is detected, the moving time when this contrast value is measured (the moving time from the initial position of the projection lens optical system 8 to the current position) is recorded. When the movement of the projection lens optical system 8 from the initial position to the nearest position is completed and the measurement of the contrast value is completed, a plurality of recorded movement times (when a contrast value greater than the threshold value is measured) Average time). In FIG. 6, the movement times T1, T2, T3,... Tn when the contrast value larger than the threshold value is obtained are detected, and the average value thereof is obtained and set as the in-focus position. That is, the moving time when the contrast value larger than the threshold value is measured is held, and the average moving time is determined as the moving time to the focal point.

  It is known that the contrast value obtained on the assumption that there is no influence of noise has a substantially symmetrical shape with the focal point as a boundary. In this embodiment, rounding processing is performed by the rounding calculation unit 22d of the calculation unit 22 shown in FIG. 2 to remove noise components, but not all noise components have been completely removed. Therefore, the noise value is somewhat added to the contrast value output from the automatic focus detection apparatus 20. Therefore, in order to specify the in-focus position without being affected by the noise component, only the movement time when the contrast value larger than the threshold value is measured is extracted, and the average of these is obtained. As a result, it is possible to specify the in-focus point with high accuracy even with a contrast value with a noise component. Accordingly, the image projected on the screen can be accurately focused.

  Next, the operation procedure of this embodiment will be described with reference to the flowchart shown in FIG. Note that the procedure for calculating the contrast value by the automatic focus detection apparatus 20 is the same as that in the first embodiment, and thus the description thereof is omitted. The cell data that has been subjected to the rounding processing is subjected to integration calculation by the integrator 22e, and the contrast value of the image is output to the control circuit 5 at regular intervals (step S31). The control circuit 5 determines whether or not the contrast value (cont) calculated by the calculation unit 22 is larger than a preset threshold value (step S32). If the calculated contrast value (cont) is larger than the threshold value (step S32 / YES), the moving time when the contrast value (cont) is measured (from the initial position of the projection lens optical system 8 to the current position). Is stored as T [i] (step S33). Further, the value of the variable i is incremented by 1, and the variable i is used as a variable for identifying the time when the contrast value exceeding the threshold value is measured next (step S33). When the calculated contrast value (cont) is smaller than the threshold value (step S32 / NO), all the data relating to the contrast value is deleted, and the processing for the contrast value is ended.

  Next, it is determined whether or not the current timer time has reached a preset feeding time Ts (step S34). When the projection lens optical system 8 has not reached the latest position (when the timer value has not reached Ts) (step S34 / NO), the procedure of steps S4 to S12 in the flowchart shown in FIG. 4 is repeated. The rounding process of the cell data is performed, and the contrast value of the image is calculated from the rounded cell data.

  If the current timer time reaches the payout time Ts (step S34 / YES), an average value of the movement time T [i] obtained by measuring the contrast value larger than the threshold value is obtained (step S35). ). The obtained average moving time is determined as the true in-focus point, and the projection lens optical system 8 is moved in the reverse direction by the time obtained by subtracting the average value from Ts (step S36). The rotation direction of the stepping motor that drives the projection lens optical system 8 is rotated in the direction opposite to the contrast value measurement direction (the direction from the nearest position to the initial position), and the projection lens optical system 8 is moved to the obtained focal point. .

  As described above, in the present embodiment, the contrast value is calculated by replacing the output of the light receiving sensor 21 with a value from which noise is removed. Furthermore, the calculated contrast value is compared with a threshold value, and only the moving time when a contrast value greater than the threshold value is measured is extracted, and the average value of these is determined as the in-focus position. ing. That is, the noise component is removed and the in-focus position is specified in consideration of the influence of the noise component that cannot be removed. Therefore, it is possible to specify the focal position of the projection lens optical system with higher accuracy.

  In the first embodiment described above, the relative focus angle of the screen 1 with respect to the projector 2 and the automatic focus detection device 20 that outputs a contrast value for determining the focal position of the projection light is accurately set in the horizontal plane and the vertical plane. The first and second line-type passive distance measuring devices 3 and 4 are separately provided.

  In the present embodiment, as shown in FIG. 8, one of the first and second line type passive distance measuring devices 3 and 4 has the function of the automatic focus detection device of the first embodiment. Since the line sensors are used for the imaging units 31 and 41 of the first and second line-type passive distance measuring apparatuses 3 and 4, the output of one of the line sensors is calculated by the calculation unit 32 or 42. The image contrast value is output. The control circuit 5 detects the position where the contrast value is maximized based on the contrast value output from one of the first and second line-type passive distance measuring devices 3 and 4, and outputs the position from the projection lens optical system 8. Alignment is performed so that the image is projected onto the screen 1. Further, the position where the contrast value is maximized is detected from the contrast value output from either one of the first and second line type passive distance measuring devices 3 and 4 also in the detailed measurement.

  As described above, in this embodiment, the focus detection function for detecting the focus position of the projection light is provided in the distance measuring device, so that the number of components can be reduced and the configuration of the projector can be simplified.

  Next, an embodiment of a focus adjustment program for a projector according to the present invention will be described. In this embodiment, the processing procedure performed by each unit shown in FIG. 1 is performed by a hardware circuit and a computer that reads a control program from the hardware circuit and performs processing according to the control program. Specifically, the computer is caused to execute the following processes. First, a focal length adjustment process for adjusting the focal length of an image projected on the screen 1 by driving and controlling the projection lens optical system 8 is executed. Next, a reflected light amount measurement process is performed in which the light reflected by the light received from the image projected onto the screen 1 by the projection lens optical system 8 is received by the light receiving sensor 21 and a signal corresponding to the amount of received light is output. Next, the value of the signal outside the range is replaced with a value within the range so that the value of the signal is within a preset range, and an operation is performed on the replaced signal to output an image contrast value. Then, an in-focus position detection process for detecting the position of the optical system that maximizes the contrast value of the output image is executed.

  Thus, also in the present embodiment, the range of the signal level output from the light receiving sensor 21 when there is no noise component is obtained in advance, and the noise component when the signal output from the light receiving sensor 21 is not within this range. Is determined to be a signal on board. And the process which replaces the value outside a range in a range is performed. An image contrast value is calculated by performing an operation on the signal thus obtained. Since the calculated contrast value is generated from the signal from which the noise component is removed, a plurality of peak values due to the noise component do not appear, and the in-focus position can be specified with high accuracy.

  The above-described embodiment is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the projection lens optical system 8 is set with the position of the projection lens optical system 8 at which the focus position of the image projected by the projection lens optical system 8 is infinite as the initial position. Is moved from the initial position in a direction in which the focal length becomes shorter. On the contrary, the position of the projection lens optical system 8 at which the position where the image is focused (focal length) is the shortest is set as the initial position, and the projection lens optical system 8 is moved from this initial position in the direction in which the focal length becomes longer. It may be allowed. In the above-described embodiments, the position of the projection lens optical system 8 is obtained from the movement time from the initial position, but the position is grasped by the number of steps of the stepping motor that drives the projection lens optical system 8. Also good.

It is a block diagram which shows the structure of the projector of an Example. 3 is a block diagram illustrating a configuration of a calculation unit 22. FIG. It is a figure for demonstrating the rounding process by the rounding calculating part 22d. It is a flowchart which shows the procedure which calculates | requires the contrast value of an image. It is a flowchart which shows the identification procedure of the focus position by the calculated | required contrast value. It is a figure which shows the contrast value obtained by the measurement, and the movement time when the contrast value larger than a threshold value is measured. 10 is a flowchart illustrating an operation procedure according to the second embodiment. 10 is a block diagram illustrating a configuration of Example 3. FIG. 1 is a diagram illustrating a configuration of an invention disclosed in Patent Document 1. FIG. It is a figure which shows the relationship between a focal point and a focus evaluation value (contrast value). It is a figure which shows the state on which the noise was added to the contrast value measured.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screen 2 Projector 3 1st line type passive distance measuring device 4 2nd line type passive distance measuring device 5 Control circuit 6 Projection image generation part 7 Display drive part 8 Projection lens optical system 10 Memory part 20 Automatic focus detection apparatus 21 Light receiving sensor 22 arithmetic unit 22a HPF 22b detector 22c A / D converter 22d rounding arithmetic unit 22e integrator 31, 41 imaging unit 32, 42 arithmetic unit

Claims (3)

A light receiving element that receives reflected light of the image projected on the screen by the projection device and outputs a signal corresponding to the amount of light received;
An operation for replacing the value of the signal outside the range with a value within the range so that the value of the signal is within a preset range, and performing an operation based on the replaced signal and outputting the contrast value of the image And
The optical system of the projection apparatus is driven and controlled to adjust the focal length of the image projected on the screen, and the position of the optical system at which the contrast value of the image is maximized is detected to match the projection apparatus. A control unit for aligning with the focal position;
A projector comprising: A focal length adjustment step for adjusting the focal length of an image projected on the screen by driving and controlling the optical system of the projection device;
A reflected light amount measuring step in which reflected light of an image projected on the screen by the projection device is received by a light receiving element, and a signal corresponding to the amount of received light is output;
A contrast in which the value of the signal outside the range is replaced with a value within the range so that the value of the signal falls within a preset range, and a calculation is performed based on the replaced signal and the contrast value of the image is output. A value calculation process;
A focus position detecting step for detecting a position of the optical system where the contrast value of the image is maximized;
A method for adjusting the focus of a projector. Focal length adjustment processing for adjusting the focal length of an image projected on the screen by driving and controlling the optical system of the projection device;
A reflected light amount measurement process in which reflected light of an image projected on a screen by the projection device is received by a light receiving element, and a signal corresponding to the amount of received light is output;
A contrast in which the value of the signal outside the range is replaced with a value within the range so that the value of the signal falls within a preset range, and a calculation is performed based on the replaced signal and the contrast value of the image is output. Value calculation processing,
A focus position detection process for detecting the position of the optical system where the contrast value of the image is maximized;
A focus adjustment program for a projector, characterized in that

Images