JP4298367B2 - Image display device and brightness control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image display device and a luminance control method, and more particularly to a technique for performing automatic luminance correction of an image display device using an optical sensor.
[0002]
[Prior art]
An image display apparatus that performs automatic luminance correction using a conventional optical sensor is, for example, as shown in Patent Document 1, an external light intensity recommended from a result verified by a designer in a built-in luminance setting circuit− It has a luminance correction characteristic that is the relationship of the luminance correction amount. For example, as shown in Patent Document 2, this brightness correction characteristic can be adjusted to an optimum brightness corresponding to individual differences of the user by controlling the brightness of the screen by manual operation and changing the brightness correction characteristic. it can. In addition, as shown in Patent Document 3, for example, the luminance correction characteristics that are not linearly proportional and have these luminance correction characteristics as a table in the memory are arbitrarily set to suit the usage environment. There are also image display devices and automatic brightness correction methods that perform the adjustment.
[0003]
[Patent Document 1]
JP-A-5-227497 (page 2-3, FIG. 1)
[Patent Document 2]
Japanese Patent Laid-Open No. 5-88655 (page 2-4, FIG. 1)
[Patent Document 3]
JP-A-6-348245 (page 2-7, Fig. 1)
[0004]
[Problems to be solved by the invention]
In an image display apparatus that performs automatic luminance correction using the conventional optical sensor as described above, the luminance correction characteristic of the external light intensity-luminance correction amount recommended by the designer or the luminance correction characteristic according to the user's request is used. ing. However, for example, when the user selects steep brightness correction characteristics assuming use under daylight in the daytime, or when the outside light intensity changes greatly in a short time, the brightness also changes greatly in a short time. Therefore, there is a problem that the user may feel uncomfortable.
[0005]
The present invention has been made to solve the above problems, and an object of the present invention is to provide an image display apparatus and a brightness control method capable of performing automatic brightness correction without causing a user to feel uncomfortable.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a luminance control method according to the first aspect of the present invention includes a step of inputting an image to be displayed from the outside, and detecting an external light intensity at a predetermined sampling period and a light corresponding thereto. A step of generating a detection output, a step of obtaining a target luminance correction amount as a target of a luminance correction amount for correcting the luminance of the input image based on the light detection output, and a correction based on the light detection output And determining a luminance correction amount to be actually added to the input image based on the obtained target luminance correction amount and the upper limit luminance variation amount. A step of correcting the luminance of the image based on the determined luminance correction amount, a step of displaying the image whose luminance has been corrected, and a step of repeatedly executing each of the above steps. correction In the step of determining the target luminance correction amount as Y0, the current luminance correction amount as Y, and the upper limit luminance change amount as ΔY, if | Y0−Y | ≦ ΔY, the luminance correction amount to be actually added is ΔY. If Y0−Y <−ΔY, the luminance correction amount to be actually added is set to Y−ΔY, and if Y0−Y> ΔY, the luminance correction amount to be actually applied is set to Y + ΔY .
[0007]
An image display device according to the invention described in claim 3 detects an external light intensity at a predetermined sampling period and generates a light detection output corresponding to the image input unit for inputting an image to be displayed from the outside. Characteristics of the light detection means, the light detection output and the target luminance correction amount as a target of the luminance correction amount for correcting the luminance of the input image, and the luminance detection amount of the light detection output and the correction Based on the current values of the light detection output, the target luminance correction amount, and the upper limit luminance change amount, the storage means for storing the correspondence characteristics with the upper limit luminance change amount serving as the upper limit value is actually applied to the input image. A calculation unit that repeatedly determines a luminance correction amount to be added, a luminance correction unit that corrects the luminance of the image based on the determined luminance correction amount, and an image display unit that displays an image whose luminance is corrected , Above When the target luminance correction amount is Y0, the current luminance correction amount is Y, and the upper limit luminance change amount is ΔY, the arithmetic means sets the luminance correction amount to be actually applied to ΔY if | Y0−Y | ≦ ΔY. If Y0−Y <−ΔY, the luminance correction amount to be actually added is set to Y−ΔY, and if Y0−Y> ΔY, the luminance correction amount to be actually applied is set to Y + ΔY.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
<Embodiment 1>
FIG. 1 shows a projection-type image display apparatus 100 according to Embodiment 1 of the present invention. The image display device 100 includes an optical sensor 110, a storage unit 120, a calculation unit 130, an image input unit 140, a luminance correction circuit 150, an image output unit 160, an image display unit 170, and an instruction input unit 180. Is provided. An outline of these components will be described first.
[0009]
The optical sensor 110 detects the intensity of ambient light around the image display device 100 and generates a light detection output corresponding to the detected intensity. The storage unit 120 stores a luminance correction characteristic that is a relationship between the light detection output and the luminance correction amount. The calculation means 130 is for calculating the luminance correction amount from the light detection output of the optical sensor 110 based on the luminance correction characteristics stored in the storage means 120. The image input unit 140 is for inputting an image into the image display apparatus 100 from the outside. The luminance correction circuit 150 is for correcting an input image based on the calculated luminance correction amount. The corrected image is output from the image output unit 160 to the image display unit 170 and projected onto the screen 190 by the image display unit 170. The instruction input unit 180 is for inputting an instruction from the user to the image display device 100.
[0010]
Next, the operation of the image display apparatus 100 shown in FIG. 1 will be described in detail.
[0011]
First, the external light intensity around the image display device 100 is detected by the optical sensor 110. The optical sensor 110 is installed at a position where the external light intensity can be detected, such as the top surface or the side surface of the image display device 100. The optical sensor 110 has an external light intensity-light detection output characteristic peculiar to the element, and this light detection output is given to the calculation means 130. That is, the optical sensor 110 functions as a light detection unit.
[0012]
The storage unit 120 stores a target luminance correction amount that is a target of the luminance correction amount for correcting the luminance of the image to the optimum brightness for reading by the user under the lighting environment used by the user. That is, the storage unit 120 stores a luminance correction characteristic that is a relationship between the light detection output and the target luminance correction amount. The storage unit 120 also stores an upper limit luminance change amount that is an upper limit value of the luminance change amount for changing the luminance so that the user does not feel uncomfortable during the luminance correction. The target luminance correction amount and the upper limit luminance change amount have characteristics as shown in FIG. 2 for the light detection output, for example, and are measured in advance and stored as a table. Since the target luminance correction amount Y0 and the upper limit luminance change amount ΔY are correction amounts and change amounts based on the luminance when the external light intensity X is 0, when X = 0, Y0 = 0 and ΔY = 0. Become. These characteristics may be stored in advance in a plurality of types, and the user may select arbitrary characteristics by inputting an instruction from the instruction input unit 180.
[0013]
The calculation means 130 to which the light detection output X from the optical sensor 110 is input, in accordance with the procedure described later, actually adds an image to the image based on the target luminance correction amount Y0 and the upper limit luminance change amount ΔY stored in the storage means 120. A luminance correction amount Y to be added is determined and input to the luminance correction circuit 150. The luminance correction circuit 150 corrects the luminance of the image input from the outside of the image display apparatus 100 through the image input unit 140 using the input luminance correction amount Y. That is, the luminance correction circuit 150 functions as a luminance correction unit. The corrected image is output from the image output unit 160 to the image display unit 170 and projected onto the screen 190 by the image display unit 170. As a result, the image projected on the screen 190 by the image display unit 170 is automatically corrected for brightness to an image having optimal brightness for reading under the user's lighting environment without giving the user a sense of incongruity.
[0014]
Next, the calculation process of the luminance correction amount Y in the calculation means 130 in the image display apparatus 100 will be described using the block diagram shown in FIG. As illustrated in FIG. 3, the calculation unit 130 includes a calculation block 131, a determination block 132, and a waiting time setting unit 133. The calculation block 131 includes an arithmetic processing block 134 and a storage control block 135, and the waiting time setting unit 133 includes a timer 136 and a counter 137.
[0015]
First, in step S <b> 1 of FIG. 4, the calculation unit 130 reads the light detection output X from the light sensor 110.
[0016]
Next, in step S2, the storage control block 135 calculates the target luminance correction amount Y0 and the upper limit luminance change amount ΔY from the read light detection output X using the characteristic table stored in the storage unit 120. To do.
[0017]
Next, in step S3, the determination block 132 compares the current luminance correction amount Y added to the image with the target luminance correction amount Y0, and based on the result, the next luminance correction to be added to the image. The quantity Y ′ is determined. However, at this time, if the luminance correction characteristic selected by the user is steep, the difference between the target luminance correction amount Y0 and the current luminance correction amount Y becomes large, and the target luminance correction amount Y0 becomes the next luminance correction amount Y ′. If it is added to the image, the luminance that changes in a short period of time is too large, which gives the user a sense of incongruity. Therefore, the absolute value of the difference (Y0−Y) between the target luminance correction amount Y0 and the current luminance correction amount Y is calculated, and the difference (Y0−Y) is compared with the upper limit luminance change amount ΔY. Then, steps S4 to S6 are performed according to the comparison result.
[0018]
That is, when the absolute value of the difference (Y0−Y) is equal to or smaller than the upper limit luminance change amount ΔY, the process proceeds to step S5, and the target luminance correction amount Y0 is set as it is as the next luminance correction amount Y ′.
[0019]
If the absolute value of the difference (Y0−Y) is larger than the upper limit luminance change amount ΔY, the process proceeds to step S4 or step S6, and the next luminance is used by using the upper limit luminance change amount ΔY instead of the target luminance correction amount Y0. A correction amount Y ′ is determined. Specifically, if Y0−Y <−ΔY (ie, Y−Y0> ΔY), the process proceeds to step S4, and (Y−ΔY) is set as the next luminance correction amount Y ′. If Y0−Y> ΔY, the process proceeds to step S6, and (Y + ΔY) is set as the next luminance correction amount Y ′.
[0020]
From the above description, when the process proceeds to any of Steps S4 to S6, the next luminance correction amount Y ′ becomes a value closer to the target luminance correction amount Y0 by ΔY than the current luminance correction amount Y. I understand that.
[0021]
Next, in step S <b> 7, the calculation means 130 updates the next luminance correction amount Y ′ obtained in steps S <b> 4 to 6 to the current luminance correction amount Y, and gives it to the luminance correction circuit 150. Then, the luminance correction circuit 150 corrects the luminance of the image input through the image input unit 140 from the outside of the image display device 100 using the given current luminance correction amount Y.
[0022]
Next, in step S8, time is waited. Thereby, one cycle of operation is completed. This waiting time determines the sampling period for detecting the intensity of external light and the period for correcting the luminance of the image. In the arithmetic circuit 130 shown in FIG. 3, the waiting time setting means 133 counts the output from the timer 136 having a fixed period by a predetermined count number N by using the counter 137, thereby obtaining a desired period T. It is possible to set. For example, the period T is set to such a value that the luminance change can be recognized smoothly by setting the count number N so that the human vision can be a time of about 10 and several msec, which is a response time to the luminance change. It may be set.
[0023]
By repeating the sequence of steps S1 to S8, the luminance of the image changes stepwise as shown in FIG. 5, and finally converges to the target luminance correction amount Y0.
[0024]
As described above, the image display apparatus 100 according to the present embodiment uses the target luminance correction amount Y0 and the upper limit luminance change amount ΔY as the luminance correction amount Y that the arithmetic unit 130 gives to the luminance correction circuit 150. Control. Therefore, even when the user selects a steep brightness correction characteristic assuming use under daylight in the daytime, or when the external light intensity changes greatly in a short time by turning on or off the illumination The temporary change of the correction amount can be suppressed to the upper limit luminance change amount ΔY or less, and automatic luminance correction can be performed without causing the user to feel uncomfortable. Therefore, there is an effect that the burden on the eyes of the user can be reduced.
[0025]
<Embodiment 2>
6 to 8 are diagrams, graphs, and flowcharts showing the luminance control method according to the second embodiment of the present invention. In the present embodiment, as shown in FIG. 6, an obstacle such as a hand temporarily passes outside between the light sensor 110 provided in the image display device 100 and the illumination 200, and then leaves again. Assume cases. As described as an example in the first embodiment, if the sampling period T for detecting the intensity of external light is set to a time of about several tens of milliseconds, which is a time during which human vision can respond to a change in luminance, detection is performed. The external light intensity X is greatly changed as shown in FIGS. 7 (a) and 7 (c). Therefore, even if the shielding by the obstacle is as short as 1 sec or less, if the period T is a time width (T1) of about several tens of msec, ΔY is corrected several times to The correction amount Y varies greatly as shown in FIG. Therefore, the brightness of the image changes greatly despite the fact that the brightness around the screen 190 has not changed, and this is recognized by the user as a brightness change.
[0026]
Therefore, step S8-1 is added to the flowchart shown in FIG. 4 as shown in FIG. In step S8-1, the user inputs an instruction from the instruction input unit 180, thereby setting the count number N of the counter 137 and changing the waiting time (that is, the period T). Here, for example, as shown in FIG. 7D, when the period T is set to a time width (T2) of about several seconds, which is the time for the obstacle to pass, and when waiting for time in step S8-2, ΔY The number of corrections is only once. Accordingly, since the change in the luminance correction amount Y is ΔY, it is not recognized as a luminance change by the user.
[0027]
As described above, in the luminance control method of FIG. 8 according to the present embodiment, step S8-1 is added to the luminance control method of FIG. 4 according to the first embodiment, and the user can set the count number N. I am doing so. Therefore, in addition to the effect of the first embodiment, there is an effect that the luminance change when the external light intensity changes temporarily can be reduced.
[0028]
【The invention's effect】
As described above, the brightness control method according to the first aspect of the present invention and the image display device according to the third aspect of the present invention are sharp when the user is assumed to be used in daylight. Even when the brightness correction characteristic is selected, or when the external light intensity changes greatly in a short time by turning on (turning off) the illumination, the temporary change in the brightness correction amount can be kept below the upper limit brightness change amount. This has the effect that automatic brightness correction can be performed without giving the user a sense of incongruity. Therefore, there is an effect that the burden on the eyes of the user can be reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an image display apparatus 100 according to a first embodiment.
FIG. 2 is a graph showing a target luminance correction amount and an upper limit luminance change amount according to the first embodiment.
FIG. 3 is a block diagram showing computing means 130 according to the first embodiment.
FIG. 4 is a flowchart showing a luminance correction method according to the first embodiment.
5 is a graph showing a luminance correction method according to Embodiment 1. FIG.
FIG. 6 is a diagram illustrating a situation where a luminance correction method according to Embodiment 2 is required.
7 is a graph showing a luminance correction method according to Embodiment 2. FIG.
FIG. 8 is a flowchart illustrating a luminance correction method according to the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 Image display apparatus, 110 Optical sensor, 120 Storage means, 130 Calculation means, 131 Calculation block, 132 Judgment block, 133 Wait time setting means, 134 Calculation processing block, 135 Storage control block, 136 Timer, 137 Counter, 140 Image input , 150 brightness correction circuit, 160 image output unit, 170 image display means, 180 instruction input means, 190 screen, 200 illumination.

Claims (4)

(A) inputting an image to be displayed from the outside;
(B) detecting the intensity of external light at a predetermined sampling period and generating a light detection output corresponding thereto;
(C) obtaining a target luminance correction amount that is a target of the luminance correction amount for correcting the luminance of the input image based on the light detection output;
(D) obtaining an upper limit luminance change amount serving as an upper limit value of the luminance change amount by correction based on the light detection output;
(E) determining a luminance correction amount to be actually added to the input image based on the obtained target luminance correction amount and the upper limit luminance change amount;
(F) correcting the luminance of the image based on the determined luminance correction amount;
(G) displaying a luminance corrected image ;
Repeatedly executing the steps (b) to (g);
With
The step of determining the brightness correction amount includes:
When the target luminance correction amount is Y0, the current luminance correction amount is Y, and the upper limit luminance change amount is ΔY,
If | Y0−Y | ≦ ΔY, the luminance correction amount to be actually applied is set to ΔY,
If Y0−Y <−ΔY, the luminance correction amount to be actually applied is set to Y−ΔY,
If Y0−Y> ΔY, the luminance correction amount to be actually applied is set to Y + ΔY.
A luminance control method which is a process. The brightness control method according to claim 1,
A luminance control method further comprising a step of a user inputting the sampling period. An image input unit for inputting an image to be displayed from the outside;
A light detection means for detecting the intensity of external light at a predetermined sampling period and generating a light detection output according to the detection period;
Correspondence characteristics between the light detection output and a target luminance correction amount that is a target of the luminance correction amount for correcting the luminance of the input image, and an upper limit that is an upper limit value of the luminance change amount due to the light detection output and correction Storage means for storing a correspondence characteristic with the luminance change amount;
Based on the current values of the light detection output, the target luminance correction amount, and the upper limit luminance change amount, arithmetic means for repeatedly determining a luminance correction amount to be actually added to the input image;
Brightness correction means for correcting the brightness of the image based on the determined brightness correction amount;
Image display means for displaying an image with corrected brightness ,
The computing means is
When the target luminance correction amount is Y0, the current luminance correction amount is Y, and the upper limit luminance change amount is ΔY,
If | Y0−Y | ≦ ΔY, the luminance correction amount to be actually applied is set to ΔY,
If Y0−Y <−ΔY, the luminance correction amount to be actually applied is set to Y−ΔY,
If Y0-Y> ΔY, the luminance correction amount to be actually applied is set to Y + ΔY . Image display apparatus. The image display device according to claim 3,
An image display device further comprising instruction input means for a user to input the sampling period.

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