JP2010134008A - Projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection device for reducing the illuminance of a projection image without making a user feel uncomfortable. <P>SOLUTION: The voltage value of a battery 18 detected by a battery voltage detection signal 11a is compared with a first threshold voltage Vth1. When the voltage value is lower than the first threshold voltage Vth1, the current value for driving an LED light source 21 is reduced every certain amount, and the brightness of the LED light source 21 is reduced gradually. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a projection apparatus.

An increase in power consumption is a big problem for a handy type projector using a battery as a power source. Conventionally, a battery voltage (battery information) indicating the battery status is projected when the battery voltage is checked every predetermined time and the battery discharge status is either `` low battery level '' or `` no battery level '' There is known a projector that superimposes on (see the following publication).
JP 2007-78807 A

  By the way, in order to extend the life of the battery, a method of controlling the intensity of the light source according to the voltage of the battery checked every predetermined time is known. However, since the driving current of the light source is as large as several hundred mA or more, and the illuminance of the projected image changes abruptly as the light source is switched, the user of the projector may be uncomfortable.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a projection apparatus that can reduce the illuminance of a projected image without causing discomfort to the user.

  In order to solve the above-mentioned problems, the invention described in claim 1 includes a projection unit that has a light source for projection and projects an optical image, a battery voltage detection unit that detects a voltage of a battery that drives the light source, and the battery. Comparison means for comparing the voltage value detected by the voltage detection means with the first threshold voltage; and control means for changing the luminance of the light source based on a comparison result between the voltage value and the first threshold voltage. When the voltage value becomes less than the first threshold voltage, the control means gradually decreases the luminance of the light source.

  According to a second aspect of the present invention, in the projection apparatus according to the first aspect, the control means gradually decreases the luminance of the light source by gradually decreasing the drive current of the light source.

  According to a third aspect of the present invention, in the projection apparatus according to the second aspect, when the voltage value becomes equal to or higher than the first threshold voltage during the gradual decrease of the drive current, the control means is configured to perform the gradual decrease of the drive. The current is gradually increased.

  According to a fourth aspect of the present invention, in the projection apparatus according to the second aspect, when the voltage value becomes equal to or higher than the first threshold voltage during the gradual decrease of the drive current, the control means is configured to perform the gradual decrease of the drive. The current is maintained at a constant current value.

  According to a fifth aspect of the present invention, in the projection device according to the second aspect, when the voltage value becomes equal to or higher than the first threshold voltage during the gradual decrease of the drive current, the control means is configured to perform the gradual decrease of the drive. It is characterized by continuing to gradually decrease the current.

  According to a sixth aspect of the present invention, in the projection device according to any one of the first to fifth aspects, when the voltage value is less than the second threshold voltage smaller than the first threshold voltage, the The control means stops the projection of the optical image by the projection means.

  The invention according to claim 7 is the projection apparatus according to any one of claims 1 to 6, wherein the light source is an LED.

  According to this invention, the luminance of the light source can be lowered without causing discomfort to the user.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of the projection apparatus 1 according to the first embodiment of the present invention, and FIG.

  The projection apparatus 1 includes a CPU (control means) 10 that is a main control unit. The CPU 10 includes a battery voltage detection circuit (battery voltage detection means) 11 that detects the voltage of the battery 18 that drives the light source (projection light source) 21, a main switch 12 that turns on and off the power supply module 14, and the power supply module 14. Are connected to the display unit 13, the projection light source drive circuit 15, the projection optical system (projection means) 20, the display image data processing circuit 16, and the image display driver 17.

  The CPU 10 has a function as a comparison unit that compares the voltage value of the power supply 18 detected by the battery voltage detection circuit 11 with the first threshold voltage.

  When the main switch 12 is pressed, the CPU 10 outputs the power supply activation signal 10a to activate the power supply module 14, and outputs the display instruction signal 10b to display the display unit 13. The display part 13 is comprised by LED, for example.

  The CPU 10 outputs a current value instruction signal 10g for changing the luminance of the light source 21 based on the comparison result between the voltage value of the battery 18 and the first threshold voltage.

  The projection light source driving circuit 15 controls the power supply to the LED light source 21 based on the LED lighting control signal 10c for controlling the lighting of the LED light source 21 from the CPU 10 and the current value instruction signal 10g, and the LED light source 21 is turned on. And turn off.

  The display image data processing circuit 16 is connected to an external interface (external I / F) 19A and a memory card 19B. The external interface 19A exchanges video / audio data and projector control data with an external device (not shown). The memory card 19B is a storage medium for writing / reading video / audio data.

  The display image data processing circuit 16 determines whether the image signal 19b is valid or invalid from the synchronization state of the input image signal 19b, and outputs an image valid / invalid signal 16a to the CPU 10. The image signal 19b includes various synchronization signals (such as a horizontal synchronization signal and a vertical synchronization signal) that define the scanning timing of the image signal.

  The image signal 19b is A / D converted by the display image data processing circuit 16 and output to the image display driver 17 as a digital image signal 16b.

  When the image display driver 17 receives the control signal 10 e from the CPU 10, the image display driver 17 generates an image signal 17 c for driving the image display element 22 in accordance with the image signal 16 b output from the display image data processing circuit 16.

  The projection optical system 20 includes an LED light source 21, an image display element 22, and a projection lens (not shown).

  Compared with a discharge light source lamp, the LED light source 21 can be reduced in size including the power source, can be turned on and off instantaneously, and the load on the light source is reduced even if the brightness change is repeated in a short time. It has many advantages as a light source for a projection device, such as being capable of stable light emission and having a long lifetime.

  The image display element 22 is, for example, a liquid crystal light valve. When the image display element 22 receives a control signal 10f from the CPU 10, the image signal 17c is modulated by modulating the light emitted from the LED light source 21 based on the image signal 17c. An optical image corresponding to is formed. The optical image formed by the image display element 22 is enlarged and projected onto the screen 5 or the like by a projection lens (not shown) (see FIG. 2).

  Next, the operation of the projection apparatus 1 according to this embodiment will be described with reference to FIG.

  FIG. 3 is a flowchart for explaining the operation of the projection apparatus according to the first embodiment of the present invention, and FIG. In FIG. 3, S11 to S18 indicate each processing step. In FIG. 4, Vth1 and Vth2 on the vertical axis are threshold voltages of the battery 18, Iset1 and Iset2 (Iset1> Iset2) are drive currents of the light source 21, and t10 to t17 on the horizontal axis are check points.

  The CPU 10 inputs the battery voltage detection signal 11a from the battery voltage detection circuit 11 and checks the voltage V of the battery 18 (S11).

  The CPU 10 determines whether or not the voltage V of the battery 18 is equal to or higher than the second threshold voltage Vth2 (S12).

  When the voltage V of the battery 18 is equal to or higher than the second threshold voltage Vth2 (YES) (t10 to t17 in FIG. 4), the CPU 10 determines whether or not the voltage V of the battery 18 exceeds the first threshold voltage Vth1. (S13).

  When the voltage V of the battery 18 exceeds the first threshold voltage Vth1 (YES) (t12, t14 in FIG. 4), it is determined whether or not the drive current is Iset1 (S16). When the drive current is Iset1 (YES), the process proceeds to another routine (not shown).

  When it is determined in step S16 that the drive current is not Iset1 (NO) (t12 and t14 in FIG. 4), a predetermined speed (for example, a speed at which 1% of Iset1 is increased per second) toward the drive current Iset1. The current value is increased by a certain amount (S17). Thereafter, the process proceeds to another routine (not shown).

  When the voltage V of the battery 18 is equal to or lower than the first threshold voltage Vth1 (NO) (t13, t15, t16, t17 in FIG. 4), it is determined whether or not the drive current is Iset2 (S14). When the drive current is Iset2 (YES), the process proceeds to another routine (not shown).

  When the drive current is not Iset2 (NO) (t13, t15, t16, t17 in FIG. 4), the drive current is directed toward Iset2 at a predetermined speed (for example, a speed that reduces the current of 1% of Iset1 per second). The value is reduced by a certain amount (S15). Thereafter, the process proceeds to another routine (not shown).

  The above process is repeated until the voltage V of the battery 18 does not exceed the first threshold voltage Vth1 and until the drive current reaches Iset2.

  When the voltage V of the battery 18 becomes less than the second threshold voltage Vth2 (NO) (t7 in FIG. 4), a flag for prohibiting the lighting of the LED light source 21 is set, and the process proceeds to another routine (not shown). 21 is turned off (S18).

  According to this embodiment, since the increase / decrease amount per unit time of the drive current for driving the LED light source 21 is reduced so that the user cannot recognize the change in the luminance of the LED light source 21, the user is uncomfortable. In addition, the illuminance of the projected image can be reduced.

  FIG. 5 is a flowchart for explaining the operation of the projection apparatus according to the second embodiment of the present invention. FIG. 6 is a diagram for explaining a method for reducing the drive current with respect to the battery voltage. The same parts as those in the first embodiment are the same. Reference numerals are assigned and explanations thereof are omitted. In FIG. 5, S21 to S26 indicate processing steps, respectively.

  In this embodiment, after the voltage V of the battery 18 once becomes equal to or lower than the first threshold voltage Vth1, the drive current of the LED light source 21 is increased when the voltage of the battery 18 again exceeds the first threshold voltage Vth1. This is different from the first embodiment in that it is maintained at a constant current value.

  The CPU 10 inputs the battery voltage detection signal 11a from the battery voltage detection circuit 11 and checks the voltage of the battery 18 (S21).

  The CPU 10 determines whether or not the voltage V of the battery 18 is equal to or higher than the second threshold voltage Vth2 (S22).

  The CPU 10 determines whether the voltage V of the battery 18 exceeds the first threshold voltage Vth1 when the voltage V of the battery 18 is equal to or higher than the second threshold voltage Vth2 (YES) (t21, t22, t23, t24 in FIG. 6). It is determined whether or not (S23).

  When the voltage V of the battery 18 exceeds the first threshold voltage Vth1 (YES), the process proceeds to another routine (not shown). At this time, without increasing the current value of the drive current, the current value when the voltage V of the battery 18 exceeds the first threshold voltage Vth1 is maintained. The drive current value is a current value between Iset1 and Iset2, and varies depending on the sampling interval for checking the voltage V of the battery 18, the rate of decrease of the voltage V, and the degree of consumption of the battery 18.

  When the voltage V of the battery 18 is equal to or lower than the first threshold voltage Vth1 (NO) (t21, t23, t24 in FIG. 6), it is determined whether or not the drive current is Iset2 (S24). When the drive current is Iset2 (YES), the process proceeds to another routine (not shown).

  When the drive current is not Iset2 (NO) (t21, t23 in FIG. 6), the drive current is directed toward Iset2, and the current value is constant at a predetermined speed (for example, a speed that reduces 1% of current of Iset1 per second). Reduce it step by step (S25). Thereafter, the process proceeds to another routine (not shown).

  Note that when the drive current reaches Iset2 before the voltage V of the battery 18 exceeds the first threshold voltage Vth1, driving is performed with the drive current Iset2.

  When the voltage V of the battery 18 becomes less than the second threshold voltage Vth2 (NO), a flag for prohibiting the lighting of the LED light source 21 is set, and the process proceeds to another routine (not shown), and the LED light source 21 is turned off (S26). ).

  According to this embodiment, the same effects as those of the first embodiment can be obtained. In the above embodiment, the voltage V of the battery 18 exceeds the first threshold voltage Vth1 only once after the voltage V of the battery 18 becomes equal to or lower than the first threshold voltage Vth1, but the voltage V of the battery 18 is the first threshold voltage Vth1. In some cases, the threshold voltage Vth1 may be increased and decreased several times across the threshold voltage Vth1, and when the driving current for the LED light source 21 is maintained multiple times when the voltage V of the battery 18 exceeds the first threshold voltage Vth1. There is also.

  FIG. 7 is a flowchart for explaining the operation of the projection apparatus according to the third embodiment of the present invention. FIG. 8 is a view for explaining a method for reducing the drive current with respect to the battery voltage. The same parts as those in the first embodiment are the same. Reference numerals are assigned and explanations thereof are omitted. In FIG. 7, S31 to S39 indicate processing steps, respectively.

  In this embodiment, after the voltage V of the battery 18 once becomes equal to or lower than the first threshold voltage Vth1, the current value is decreased by a certain amount at a predetermined speed until the drive current of the LED light source 21 becomes Iset2. This is different from the first embodiment.

  The CPU 10 inputs the battery voltage detection signal 11a from the battery voltage detection circuit 11 and checks the voltage V of the battery 18 (S31).

  The CPU 10 determines whether or not the voltage V of the battery 18 is equal to or higher than the second threshold voltage Vth2 (S32).

  When the voltage V of the battery 18 is equal to or higher than the second threshold voltage Vth2 (YES) (t31, t32, t33 in FIG. 8), the CPU 10 determines whether or not the voltage V of the battery 18 exceeds the first threshold voltage Vth1. Is determined (S33).

  When the voltage V of the battery 18 exceeds the first threshold voltage Vth1 (YES) (t32, t33 in FIG. 8), a current transition flag indicating whether or not the drive current value is gradually decreasing from Iset1 to Iset2 (S37).

  If the drive current value is not gradually decreased from Iset1 to Iset2 (NO) (t33 in FIG. 8), the process proceeds to another routine (not shown).

  When the drive current value is gradually reduced from Iset1 to Iset2 (YES) (t32 in FIG. 8), the drive current is continuously reduced toward Iset2 by a certain amount (S38). Thereafter, the process proceeds to another routine (not shown).

  When the voltage V of the battery 18 is equal to or lower than the first threshold voltage Vth1 in step S33 (NO) (t31 in FIG. 8), a current transition flag is set (S34), and whether the drive current value is Iset2 or not. Is determined (S35).

  When the drive current value is Iset2 (YES) (t33), the current transition flag is cleared (S36), and the process proceeds to another routine (not shown). When the drive current value is not Iset2 (NO), the process proceeds to step S38, and the current value is decreased by a certain amount at a predetermined speed with the drive current directed to Iset2.

  When the voltage V of the battery 18 becomes lower than the second threshold voltage Vth2 (NO), a flag for prohibiting the lighting of the LED light source 21 is set, and the routine proceeds to another routine (not shown) to turn off the LED light source 21 (S39). ).

  According to this embodiment, the same effects as those of the first embodiment can be obtained.

  Next, a conventional driving current reduction method will be described as a comparative example.

  FIG. 9 is a diagram for explaining a method of reducing the drive current with respect to the battery voltage.

  When the voltage V of the battery 18 becomes less than the first threshold voltage Vth1 (t1), the drive current of the LED light source 21 is switched from Iset1 to Iset2. When the drive current decreases, the voltage V of the battery 18 rapidly increases, and the voltage V of the battery 18 again exceeds the first threshold voltage Vth1. Therefore, the LED light source 21 is driven with the drive current Iset2 until the next voltage check (t2), and is driven with the drive current Iset1 after t2.

  Thereafter, when the voltage V of the battery 18 becomes less than the first threshold voltage Vth1 (t3), the drive current of the LED light source 21 is switched from Iset1 to Iset2 again. At this time, the voltage V of the battery 18 rapidly increases, and the voltage V of the battery 18 again exceeds the first threshold voltage Vth1.

  As described above, the LED light source 21 is driven by the drive current Iset2 until the next voltage check (t4), and is driven by the drive current Iset1 after t4.

  Thereafter, when the voltage of the battery 18 becomes less than the first threshold voltage Vth1 (t5), the drive current of the LED light source 21 is switched from Iset1 to Iset2.

  When the battery 18 is exhausted, the voltage V of the battery 18 does not exceed the first threshold voltage Vth1, and the LED light source 21 continues to be driven with the drive current Iset2.

  Thereafter, at time t6 when the voltage of the battery 18 becomes less than the second threshold voltage Vth2, the projection light source drive circuit 15 is driven to turn off the LED light source 21.

  When the drive current of the LED light source 21 is controlled as described above, since the change in the luminance of the LED light source 21 is large, the change in the luminance is recognized by the user, and the user is uncomfortable.

FIG. 1 is a block diagram showing the configuration of a projection apparatus 1 according to the first embodiment of the present invention. FIG. 2 is a perspective view showing a usage state of the projection apparatus 1. FIG. 3 is a flowchart for explaining the operation of the projection apparatus according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating a method for reducing drive current with respect to battery voltage. FIG. 5 is a flowchart for explaining the operation of the projection apparatus according to the second embodiment of the invention. FIG. 6 is a diagram for explaining a method of reducing the drive current with respect to the battery voltage. FIG. 7 is a flowchart for explaining the operation of the projection apparatus according to the third embodiment of the invention. FIG. 8 is a diagram for explaining a method of reducing the drive current with respect to the battery voltage. FIG. 9 is a diagram for explaining a method of reducing the drive current with respect to the battery voltage.

Explanation of symbols

  1: projection device, 10: CPU (control means), 11: battery voltage detection circuit (battery voltage detection means), 18: power supply (battery), 20: projection optical system (projection means), 21: light source (for projection) light source).

Claims (7)

A projection unit having a light source for projection and projecting an optical image;
Battery voltage detection means for detecting the voltage of the battery that drives the light source;
Comparison means for comparing the voltage value detected by the battery voltage detection means with a first threshold voltage;
Control means for changing the brightness of the light source based on a comparison result between the voltage value and the first threshold voltage;
When the voltage value becomes less than the first threshold voltage, the control unit gradually decreases the luminance of the light source.   The projection apparatus according to claim 1, wherein the control unit gradually decreases the luminance of the light source by gradually decreasing the driving current of the light source. When the voltage value becomes equal to or higher than the first threshold voltage during the gradual decrease of the drive current,
The projection apparatus according to claim 2, wherein the control unit gradually increases the driving current being gradually decreased. When the voltage value becomes equal to or higher than the first threshold voltage during the gradual decrease of the drive current,
The projection apparatus according to claim 2, wherein the control means maintains the driving current that is gradually decreasing at a constant current value.   3. The projection apparatus according to claim 2, wherein when the voltage value becomes equal to or higher than the first threshold voltage during the gradual decrease of the drive current, the control unit continues to gradually decrease the drive current being gradually decreased. When the voltage value is less than the second threshold voltage less than the first threshold voltage,
The projection device according to claim 1, wherein the control unit stops the projection of the optical image by the projection unit.   The projection apparatus according to claim 1, wherein the light source is an LED.

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