JP4414955B2 - Brightness adjustment method and brightness adjustment device - Google Patents

Description

  The present invention relates to a luminance adjustment method for adjusting the luminance of light emitted from a light source and a luminance adjustment device using the luminance adjustment method, and more particularly to a luminance adjustment device that realizes stable light emission under various conditions.

  A fluorescent tube used as a light source of a liquid crystal monitor using a light modulation element has a characteristic that the amount of light changes at the start of operation and when used for a long time. The main factor that changes the amount of light is the change in luminous efficiency due to the temperature change of the fluorescent tube.

  FIG. 6 is a graph showing the relationship between the temperature of the fluorescent tube and the luminous efficiency. In FIG. 6, the temperature is plotted on the horizontal axis and the luminous efficiency is plotted on the vertical axis, and the relationship is shown. The tube current supplied to the fluorescent tube is constant. As apparent from FIG. 6, the light emission efficiency varies depending on the temperature. Therefore, even if the tube current is constant, the light amount varies depending on the temperature.

Therefore, in order to stabilize the light amount, a method of measuring the light amount of the fluorescent tube and controlling the tube current to the fluorescent tube so that the measured value becomes constant has been put into practical use (see, for example, Patent Document 1). By controlling the tube current, the amount of light is adjusted within a dimming range in which the fluorescent tube can stably emit light.
Japanese Patent Laid-Open No. 9-043569

  However, since the luminous efficiency varies depending on the temperature, there is a problem that the dimming range must be narrowed in order to stably emit light regardless of the temperature. The reason why the dimming range must be narrowed will be described below.

  FIG. 7 is a graph showing the stability of light emission with respect to the tube current and temperature of a fluorescent tube. In FIG. 7, the horizontal axis represents the tube current and the vertical axis represents the temperature, and the stability of light emission with respect to the tube current and temperature is shown. In the graph shown in FIG. 7, a region A is a stable light emitting region where light emission is stable, and a region B is an unstable light emitting region where light emission becomes unstable. As shown in FIG. 7, the higher the tube current, the more stable the light emission, and the lower the tube current, the more unstable. Further, the higher the temperature, the wider the stable light emitting region, and the lower the temperature, the narrower the stable light emitting region.

  FIG. 8 is a graph showing the stability of light emission and the temperature with respect to the tube current and the luminance of the fluorescent tube. In FIG. 8, the horizontal axis represents the tube current, and the vertical axis represents the luminance obtained by measuring the amount of light, and the relationship between the stability of light emission with respect to the tube current and the luminance and the temperature is shown. In FIG. 8, tube currents I1 and I2 correspond to I1 and I2 in FIG. 7, respectively. Further, the solid line shown as T1 in FIG. 8 shows the relationship between the tube current and the luminance at the temperature T1 in FIG. 7, and the solid line shown as T2 in FIG. 8 shows the tube at the temperature T2 in FIG. The relationship between current and luminance is shown. FIG. 8A shows a stable light emission region and an unstable light emission region at the temperature T1, and a region α1 in FIG. 8A is a stable light emission region where light emission is stable, and a region β1 is light emission. Is an unstable emission region where becomes unstable. FIG. 8B shows a stable light emission region and an unstable light emission region at the temperature T2, and a region α2 in FIG. 8B is a stable light emission region where light emission is stable, and a region β2 is light emission. Is an unstable emission region where becomes unstable. As described with reference to FIG. 7, the stable light emitting region changes depending on the temperature, and therefore the range of the region differs between the temperature T1 and the temperature T2.

  For example, as described in Patent Document 1, in the conventional method of measuring the light amount of a fluorescent tube and controlling the luminance of the fluorescent tube so that the measured value is constant, the dimming range of B1 shown in FIG. When the lower limit is set, light emission is stable at low temperatures near T1, but light emission becomes unstable at high temperatures near T2. Therefore, in order to obtain stable light emission in the range of temperatures T1 to T2, the lower limit of the dimming range must be set to B2 or more.

  However, when the temperature is T1, the lower limit value of the luminance can be lowered to B1 lower than B2. That is, although the lower limit value of the luminance can be lowered to B1, in order to stably emit light within the temperature range of T1 to T2, the lower limit value of the luminance must be set to B2. Need to be narrowed.

  The present invention has been made in view of such circumstances, and by using a control method for controlling tube current based on luminance and a method for controlling temperature, and selecting a control method according to the situation, It is an object of the present invention to provide a luminance adjustment method capable of expanding the dimming range, and a luminance adjustment device using the luminance adjustment method.

The brightness adjustment method according to the first aspect of the present invention is a brightness adjustment method for a brightness adjustment apparatus that adjusts the brightness of light emitted from a light source, wherein the brightness adjustment apparatus controls a current supplied to the light source based on the measured brightness of the light. light at selects one from among the temperature control for adjusting the brightness by controlling the current control for adjusting the brightness, the temperature of the light source based on the temperature of the measurement light source, the selected current control or temperature control by In this case, when the measured luminance falls below a preset lower limit value, temperature control with a constant current supplied is selected .

A brightness adjusting apparatus according to a second aspect of the present invention is a brightness adjusting apparatus that adjusts the brightness of light emitted from a light source by supplying a current, a brightness measuring means for measuring brightness, and supplying the light source based on the measured brightness. Current control means for adjusting brightness by controlling current, temperature measurement means for measuring the temperature of the light source, temperature control means for adjusting brightness by controlling the temperature of the light source based on the measured temperature, and brightness As a method of adjusting, comprising a selection means for selecting one of the current control by the current control means and the temperature control by the temperature control means , the selection means, when the brightness is below a preset lower limit value, as a control method, configured so as to select the temperature control in which the current supplied is constant and said tare Rukoto.

  The brightness adjustment method and the brightness adjustment apparatus according to the present invention perform current control for controlling current based on brightness at high brightness, and select temperature control with a constant current to be supplied at low brightness. Since the lower limit value can be lowered, the dimming range can be expanded.

  The brightness adjustment method and the brightness adjustment apparatus according to the present invention are apparatuses for adjusting the brightness of light irradiated to a liquid crystal panel using a light modulation element from a light source such as a fluorescent tube. When the brightness is high, the brightness is measured and measured. The tube current supplied to the light source is controlled based on the brightness, and the temperature of the light source is controlled using a temperature control element such as a Peltier element based on the temperature of the light source when the brightness is low.

  With this configuration, the light emission can be stabilized by lowering the temperature even at low brightness, where the light emission of the fluorescent tube tends to be unstable, so the lower limit of the brightness can be lowered, so the light control range can be reduced. It has excellent effects such as being able to enlarge.

  Hereinafter, the screen showing the embodiment of the present invention will be described in detail.

  FIG. 1 is a block diagram showing a configuration example of a brightness adjusting apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a brightness adjusting apparatus of the present invention such as an LCD monitor. The brightness adjusting apparatus 1 includes a liquid crystal panel 10 using a light modulation element and a fluorescent tube for irradiating light to the light modulation element of the liquid crystal panel 10. And the like. The brightness adjusting device 1 also includes a brightness measuring unit 12 that measures the amount of light emitted from the light source 11 as brightness, a current control unit 13 that controls the current supplied to the light source 11, that is, a tube current, and the temperature of the light source 11. A temperature measurement unit 14 for measuring and a temperature control unit 15 using a temperature control element such as a Peltier element for controlling the temperature of the light source 11 are provided. Further, the brightness adjusting apparatus 1 includes a control unit 16 including circuits such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory) that control the entire apparatus.

  FIG. 2 is a flowchart showing an example of the control selection process of the brightness adjusting apparatus 1 of the present invention. The brightness adjusting device 1 acquires the brightness of the light source 11 measured by the brightness measuring unit 12 under the control of the control unit 16 (step S1), and compares the acquired brightness with a preset lower limit value. It is determined whether or not the value is greater than or equal to the value (step S2).

  When it is determined in the comparison in step S2 that the acquired luminance is equal to or higher than the lower limit value (step S2: YES), the luminance adjusting device 1 turns off the low luminance mode for controlling the luminance by temperature (step S3), and the tube The high brightness mode for controlling the brightness by the current is turned on (step S4). By the processing of steps S3 to S4, the luminance adjusting apparatus 1 selects the high luminance mode for performing current control when the luminance is equal to or higher than the lower limit value.

  When it is determined in the comparison in step S2 that the acquired luminance is less than the lower limit value (step S2: NO), the luminance adjusting device 1 turns off the high luminance mode (step S5) and turns on the low luminance mode. (Step S6). By the processing of steps S5 to S6, the luminance adjusting device 1 selects the low luminance mode for performing temperature control when the luminance is less than the lower limit value.

  When the low brightness mode is turned off and the high brightness mode is turned on, the brightness adjusting device 1 performs the current control process by using the current control unit 13 to calculate the tube current based on the brightness of the light source 11 measured by the brightness measuring unit 12. The light quantity of the light source 11 is controlled by the feedback process to be controlled.

  FIG. 3 is a graph showing an example of the relationship between the tube current and the luminance in the luminance adjusting apparatus 1 of the present invention. FIG. 3 shows the relationship between the tube current and the luminance under the condition that current control is performed in the high luminance mode, with the horizontal axis representing the tube current and the vertical axis representing the luminance. As shown in FIG. 3, since the tube current and the brightness have a positive correlation, it is possible to adjust the brightness by controlling the light amount of the light source 11 by controlling the tube current with the current control unit 13. .

  When the high luminance mode is turned off and the low luminance mode is turned on, the luminance adjustment device 1 controls the temperature by the temperature control unit 15 based on the temperature of the light source 11 measured by the temperature measurement unit 14 as a temperature control process. The amount of light from the light source 11 is controlled by the feedback process. When the temperature control process is executed in the low luminance mode, the tube current is controlled by the current control unit 13 so as to be constant at a value at the point where the mode is switched, for example, a burst duty lower limit value.

  FIG. 4 is a graph showing an example of the relationship between temperature and light emission efficiency in the brightness adjusting apparatus 1 of the present invention. FIG. 4 shows the relationship between temperature and light emission efficiency under conditions where temperature control is performed in the low luminance mode, with the horizontal axis representing temperature and the vertical axis representing light emission efficiency. The tube current is controlled to be constant. When the temperature is controlled within the range shown as the temperature control range in FIG. 4, the temperature and the light emission efficiency have a positive correlation. Therefore, the temperature control unit 13 controls the temperature to control the light emission efficiency. Therefore, the luminance can be adjusted by controlling the light quantity of the light source 11.

  FIG. 5 is a graph showing light emission stability and temperature with respect to tube current and luminance in the luminance adjusting apparatus 1 of the present invention. In FIG. 5, the horizontal axis represents the tube current and the vertical axis represents the luminance, and the relationship between the stability of light emission with respect to the tube current and the luminance and the temperature is shown. Also, the lower limit value of the temperature control range of the light source 11 is T1, the upper limit value is T2, and the solid line shown as T1 in FIG. 5 shows the relationship between the tube current and the luminance at the temperature T1, and the solid line shown as T2. Shows the relationship between the tube current and the brightness at the temperature T2. FIG. 5A shows a stable light emission region and an unstable light emission region at the temperature T1, and a region α1 in FIG. 5A is a stable light emission region where light emission is stable, and a region β1 is light emission. Is an unstable emission region where becomes unstable. FIG. 5B shows a stable light emission region and an unstable light emission region at the temperature T2, and a region α2 in FIG. 5B is a stable light emission region where light emission is stable, and a region β2 is light emission. Is an unstable emission region where becomes unstable. Since the stable light emitting region changes depending on the temperature, the range of the region is different between the temperature T1 and the temperature T2. Further, the lower limit value of the luminance in the control selection process described with reference to FIG. 2 is B3.

  In the brightness adjusting apparatus 1 of the present invention, when the brightness is equal to or higher than the lower limit B3, the control by the tube current is performed as the current control process. When the luminance is B3 or higher, as long as the temperature of the light source 11 is within the temperature control range, control within the stable light emission region indicated as the region α1 or α2 is possible. When the luminance is less than the lower limit B3, temperature control is performed as a temperature control process. In this case, the tube current is fixed at a value equal to or higher than I2 which is the lower limit value at the time of luminance B3 and temperature T2. When the tube current is fixed at I2, even if the temperature is lowered to T1, it is possible to control within the stable light emitting region shown as the region α1 or α2, and the dimming range to the luminance B1 lower than the luminance B2 and the luminance B3. Can be expanded.

  That is, compared with the conventional method described with reference to FIG. 8, the method using the brightness adjusting apparatus 1 according to the present invention enables control not only in the area above the brightness B3 but also in the area below the brightness B3. Since the lower limit value of the dimming range can be lowered from B3 to B1, the dimming range can be expanded.

  The above-described embodiment is one of innumerable forms for realizing the present invention, and can be developed in various forms other than the above-described forms. For example, instead of selecting the control method based on the luminance, the control method may be selected based on the tube current value. Furthermore, the present invention is not limited to the light source of the liquid crystal monitor, and can be applied to ordinary illumination such as room light.

It is a block diagram which shows the structural example of the luminance adjustment apparatus of this invention. It is a flowchart which shows an example of the control selection process of the luminance adjustment apparatus of this invention. It is a graph which shows an example of the relationship between the tube current and the brightness | luminance in the brightness | luminance adjustment apparatus of this invention. It is a graph which shows an example of the relationship between the temperature in the brightness | luminance adjusting device of this invention, and luminous efficiency. It is a graph which shows the stability and temperature of the light emission with respect to the tube current and the brightness | luminance in the brightness adjusting device of this invention. It is a graph which shows the relationship between the temperature of a fluorescent tube, and luminous efficiency. It is a graph which shows the stability of the light emission with respect to the tube current and temperature of a fluorescent tube. It is a graph which shows the stability and temperature of the light emission with respect to the tube current and the brightness | luminance of a fluorescent tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brightness adjustment apparatus 10 Liquid crystal panel 11 Light source 12 Luminance measurement part 13 Current control part 14 Temperature measurement part 15 Temperature control part 16 Control part

Claims (2)

In the luminance adjustment method of the luminance adjustment device for adjusting the luminance of light emitted from the light source,
The brightness adjusting device includes:
Current control for adjusting the brightness by controlling the current supplied to the light source based on the measured brightness of the light;
Temperature control that adjusts brightness by controlling the temperature of the light source based on the measured temperature of the light source ;
One of them is selected, and the brightness of light is adjusted by the selected current control or temperature control.
A brightness adjustment method comprising: selecting temperature control in which a supplied current is constant when measured brightness falls below a preset lower limit value . In a brightness adjustment device that adjusts the brightness of light emitted from a light source by supplying current,
A luminance measuring means for measuring luminance;
Current control means for adjusting the luminance by controlling the current supplied to the light source based on the measured luminance;
Temperature measuring means for measuring the temperature of the light source;
Temperature control means for adjusting brightness by controlling the temperature of the light source based on the measured temperature ;
As a method of adjusting the brightness, comprising a selection means for selecting one of current control by the current control means and temperature control by the temperature control means ,
Said selecting means, if below the lower limit value the brightness is preset as a control method, the brightness adjusting device, wherein the structure to be Ru tare so as to select the temperature control in which the current supplied is constant .

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