JPH11344692A - Contrast adjusting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a user to adjust a contract more intiuitively without making the user feel uneasy about whether or not switch operation for contrast adjustment is accepted. SOLUTION: When a user commands a process part 5 to start contrast adjusting operation by operating a switch 4, the process part 5 writes set values on a memory 6 onto a register 1 and simultaneously displays the set values on the memory 6 and the current contrast on the register 1 or its difference in characters or symbols on a screen of an LCD display module 3. The process part 5 varies the contrast of the screen of the module 3 gradually for example, from the densest to the lightest by gradually varying the contents of the register 1. When a contract value becomes a contrast value suitable to a current ambient temperature in a process of this variation, the user reads the set values and the current contrast from the screen of the module 3 and operates a switch 7 to be able to set the optimum contrast value on the memory 6. Instead of displaying the contrast, etc., discrimination or multistage adjustment based upon the toggle state of the switch 4 can be introduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contrast adjusting method and circuit for adjusting the contrast of a screen of an LCD (liquid crystal display).

[0002]

2. Description of the Related Art A dot matrix type L
The CD display has the property that the contrast of the screen changes with the change of the ambient temperature. For example, consider a case where an LCD display in which a contrast suitable for a room with a heated room is already set is taken out and used outdoors in winter. Since the LCD display exposed to low temperature outdoors is cold, it may not be possible to read anything from the screen immediately after the power is turned on. That is, L
Even if the circuit for controlling the display of the CD display performs a process of displaying some characters, symbols, graphics, etc. on the screen of the LCD display, the contrast setting value is out of the optimum value at the outdoor temperature. Therefore, the screen may become dark (or white), and the user may not be able to read the character or the like. In this situation where nothing can be read from the screen, many users say,
Is the display (and the device containing it) working correctly? "

[0003] Users who feel such anxiety usually
In order to eliminate the anxiety, try to operate one of the various switches and buttons attached to the device that does not seem to hinder the operation. As a result, if there is no response from the device side, the situation is erroneously recognized as "this device is out of order", and it takes time to recover the situation. Conversely, if there is a reaction from the device side, such as a buzzer sound, many users say, "This device is not malfunctioning, and it is likely that the contrast has not been properly adjusted. Is determined. However, at this point, since the key or button operation has been performed several times, the user performs an operation for restoring the original state or exiting the current state according to his / her memory without reading characters or the like from the screen. Operation must be performed. In particular, if you do not remember the types of keys and buttons that have been operated up to that time and their operation order, or if you do remember complicated operations, you will be asked "What kind of situation is the current situation?" Do you do what you want to do? "

[0004] In order to prevent such a situation from occurring, the contrast does not change even when the ambient temperature changes, so that an easy-to-see screen state is maintained, or the contrast can be adjusted as needed by the user. Or either action is necessary. As an example of the former, that is, an example of automatic temperature compensation, there is an example in which the ambient temperature is detected by a temperature sensing element such as a thermistor and the contrast is automatically adjusted in accordance with the result. Since the characteristics of the respective circuit elements constituting the display vary, it is difficult to always keep the screen state in an easily viewable state.
As an example of the latter, that is, manual adjustment, a variable resistor whose resistance value changes according to the operation of a sliding or rotary knob is provided, and an LCD is provided according to the voltage or current supplied through the variable resistor. There are examples of setting and changing the contrast of the display screen.However, the resistance of the variable resistor is generally insufficient, and it is suitable for equipment used outdoors such as portable and portable equipment. Absent.

[0005] Circuit components that can be used for manual adjustment of contrast and are more waterproof than variable resistors include:
There is a push button switch. For example, by using a combination of an up switch for increasing contrast and a down switch for decreasing contrast, that is, an up-down switch, the user appropriately instructs an increase or decrease of the contrast value.
Set and change the contrast of the screen of the CD display.
However, in this case, the user may not be able to immediately find the optimum screen state. That is, as described above, a situation in which nothing can be read from the screen and the user judges that "this device is not malfunctioning, and the contrast is probably not properly adjusted". Underneath, even if the user operates the up / down switch to adjust the contrast, whether the user should operate the up switch or the down switch, and how many times the switch should be pressed, is usually determined by the user. I do not know. In many cases, operating the up-down switch several times in this state does not provide the optimum contrast in many cases. For this reason, the user is asked, "Is the device surely accepting the operation of the up-down switch?" It becomes a material of anxiety such as. Further, the operation of the up-down switch is trial and error, and the operation is slightly unnecessarily repeated (for example, the operation of pressing the up switch unnecessarily based on a judgment that "I'm sure that the contrast should be strengthened") is repeatedly performed. As a result, useless operations may be performed and the user's labor may be impaired. Further, when the up / down switch is shared with another operation function, the contrast may not be adjusted due to the influence of the key operated so far. If the user presses the up / down key in such a state, the result may be unexpected for the user, which is dangerous.

[0006]

SUMMARY OF THE INVENTION One of the objects of the present invention is that a contrast adjustment operation must be performed in a state where characters and the like cannot be read from a screen, and a user must perform an adjustment operation by trial and error. It is an object of the present invention to solve the problem and allow the user to adjust the contrast easily without feeling uneasy. In order to achieve this object, the present invention uses a technique of gradually changing contrast and displaying contrast information, and a technique of adjusting contrast by repeatedly operating a contrast adjustment start / end switch.

The present invention can be realized as a contrast adjusting method for setting and changing the contrast of a display in response to a command from a user, or as a contrast adjusting circuit. The display to which the present invention is applied is an LCD display whose contrast has temperature dependence, and a display whose contrast can be set by the level of the drive voltage. Further, in the present invention, regarding the start and end of the contrast adjustment (and increase / decrease of the contrast), a command is received from the user by operating a switch or the like.

In the present invention, the contrast gradual change operation is started and ended according to the start and end commands of the contrast adjustment. Here, the contrast gradually changing operation is L
This is an operation of gradually changing the contrast of the screen of the CD display from the darkest to the lightest or from the lightest to the darkest in a predetermined cycle,
This is realized by gradually changing the level of the drive voltage for driving the LCD display.

The present invention is divided into at least two types of embodiments depending on the processing during the execution of the contrast gradually changing operation. The first embodiment is configured to execute the adjustment index display process and the set value update process while performing the contrast gradual change operation. The purpose of the contrast gradual change operation according to the present embodiment is to provide the user with information necessary for setting the contrast at that moment, utilizing the fact that the screen is always read in an instant due to the gradual change. The adjustment index display process referred to here is a process of displaying information on the current value and the set value of the screen contrast in characters or symbols on the screen of the LCD display. The set value update process is a process of changing the contrast. This is a process of changing the contrast set value in accordance with the instruction regarding the image data and storing the changed value. Note that the start and end of the contrast adjustment can also be realized as a toggle state of one switch.

According to the order of instructions from the user,
First, when the user instructs the start of the contrast adjustment by operating a switch or the like, the contrast of the screen of the LCD display gradually starts to change from darkest to lightest or from lightest to darkest. While the contrast is gradually changing, a state where the contrast of the screen becomes the most suitable value for the current ambient temperature (more generally, the current ambient environment) occurs in a short period of time. During that period, the user can see the characters or symbols related to the adjustment index display process, that is, the information on the current value and the set value of the screen contrast from the screen of the LCD display. The user operates a switch or the like in accordance with the information seen, that is, the difference between the current value and the set value, thereby appropriately giving a contrast change instruction. When this command is given, the set value of the contrast is changed and stored. When the user instructs the end of the contrast adjustment by operating a switch or the like, the level of the drive voltage thereafter is determined based on the set value at that time. Therefore,
The display is performed with the contrast adjusted by the user.

As described above, in the present invention, there are situations where the contrast adjustment operation must be performed in a state where characters and the like cannot be read from the screen, and the user must perform the adjustment operation by trial and error. Does not occur. Therefore, the contrast can be adjusted easily without the user feeling anxiety and compared with the related art. In addition, while the contrast gradual change operation is being performed, the value of the contrast of the screen and the set value of the contrast at that time may be displayed on the screen of the LCD display. It is also possible to display the difference between the screen contrast values on the screen of the LCD display. In any of these display modes,
The user can more easily know how to issue a command for changing the contrast (for example, how many times the up / down switch should be operated in the up / down direction). This effect becomes more prominent in the latter case, that is, in the form of displaying the difference. Further, by displaying the display during the execution of the contrast gradual change operation as a graph display, for example, a bar graph display indicating the required number of switch operations, a display that is more intuitive and easy to understand can be realized.

In this embodiment of the invention,
A contrast adjustment start / end switch as a member operated by the user to instruct the start and end of the contrast adjustment processing, an up / down switch operated by the user to instruct an increase or decrease of the contrast value of the screen of the LCD display, Each is provided. Since these switches do not use a variable resistor, they contribute to the realization of a device having excellent waterproofness and suitable for outdoor use. Further, a contrast memory and a contrast register are provided, and the contrast setting value is stored in the contrast memory, and a voltage generator (a circuit for generating a drive voltage for the LCD display) is used by the contrast register to control the contrast value of the screen of the LCD display. If a circuit configuration or a memory configuration that gives a command is used, the drive voltage level is determined by writing to the contrast register, and the drive voltage level is gradually changed by periodically updating the content of the contrast register. The above-described contrast adjustment method can be executed by a method of updating the set value by writing to the contrast memory. The processing unit for that can be realized by software or hardware. That is, the contrast adjusting method according to the present invention can be realized by one or more programs, and further includes a clock generator, a counter, a comparator,
It can also be realized by hardware resources such as registers.

In the second embodiment of the present invention, the contrast adjusting operation is started by operating the contrast adjusting start / end switch, and the contrast is adjusted by operating the contrast adjusting starting / ending switch in the state where the contrast adjusting operation is being performed. This is a configuration for terminating the gradual change operation.
That is, whether to start or end the contrast gradual change operation is determined based on the toggle state of the contrast adjustment start / end switch, which is a single switch. The purpose of the contrast gradual change operation according to the present embodiment is to stop the screen by a switch when the screen becomes readable by the gradual change, and to maintain the contrast at that time,
The difference from the first embodiment is that it is not necessary to display information necessary for contrast adjustment. As a result, compared to the first embodiment, the operation by the user and the processing on the device side are simplified, and the number of members such as switches is reduced because an up-down switch is not required. Further, since there is no need to display information relating to contrast, the display content may be kept as it is (ie, no special characters, symbols, etc. are displayed), and the processing on the device side is simplified accordingly.

When the contrast adjustment start / end switch is operated in the state where the contrast change operation is being performed, for example, the contrast change operation is ended and the drive voltage level at that time is immediately changed to the next drive voltage. Level. More preferably, the adjustment may be made so as to compensate for a shift corresponding to a user operation delay time from the viewing of the screen of the LCD display to the operation of the contrast adjustment start / end switch. That is, it takes a certain amount of time for the user to look at the screen of the LCD display and determine that the contrast is “just right” and operate the contrast adjustment start / end switch, and the contrast changes even during that time. Therefore, a step of compensating the drive voltage level, that is, the contrast at the end of the contrast gradually changing operation may be added.

Further, the contrast gradual change operation is performed in the entire range at first, and the second gradual change operation is performed in a narrower range and at a slower gradual change speed. It may be performed at the stage. That is,
When the contrast adjustment start / stop switch is operated by operating the contrast adjustment start / end switch and then the contrast adjustment start / end switch is operated again, the gradual change range up to and including the contrast corresponding to the drive voltage level at that time. Contrast adjustment start / stop switch after narrowing the contrast gradual change range to a narrower range and reducing the gradual change speed from the previous speed, continuing the contrast gradual change operation, and starting the contrast gradual change operation When the number of operations has reached the predetermined number, the contrast gradual change operation ends, and the drive voltage level at that time becomes the subsequent drive voltage level. As described above, the contrast gradual change operation is performed in a plurality of steps while narrowing the gradual change range of the contrast, that is, the contrast can be adjusted in each step such as the coarse adjustment and the fine adjustment. It is not necessary to compensate for time. The above-mentioned predetermined number of times, that is, the number of execution steps of the contrast gradual change operation may be a natural number of 2 or more in principle, but is preferably 2 in consideration of the simplicity of the operation by the user.

The method of determining the gradual change range when the contrast gradual change range is narrowed and the contrast gradual change operation is continued, for example, corresponds to the drive voltage level at the time when the contrast adjustment start / end switch is operated. There is a method in which a predetermined value is added to or subtracted from the contrast substantially at the center and a gradual change range of the contrast in the subsequent operation is determined. When using this method,
It is also effective to expect a shift corresponding to the user operation delay time. For example, the above-mentioned predetermined value is set in advance to a value larger than the shift corresponding to the user operation delay time. Alternatively, in order to compensate for a shift corresponding to the user operation delay time, the gradual change range of the contrast in the subsequent operation is determined by shifting the range to either light or dark.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the present application, the term “LCD display” is used to include various display devices having a characteristic that the contrast depends on temperature, in addition to a known device usually called an LCD display. Also,
In the description in the present application, the present invention refers to a “contrast adjustment method”.
Although it is stated that the invention relates to a "contrast adjustment circuit", the present invention relates to "an LCD display having a manual contrast adjustment function", "a processing device for a contrast adjustment circuit".
It can also be expressed as: This rephrasing can be easily made by those skilled in the art with reference to the disclosure of the present application. And
In the following description, an example in which the contrast is gradually changed from the lightest to the darkest is shown, but the contrast may be gradually changed in the opposite direction.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) First Embodiment FIG. 1 shows a configuration of a contrast adjusting circuit according to a first embodiment of the present invention. In the figure, the contrast register 1 is
This is a register for giving a command relating to the contrast of the screen of the LCD display module 3 to the voltage generator 2. The voltage generator 2 generates a drive voltage according to the contrast value on the contrast register 1. The LCD display module 3 is driven by the voltage. The contrast adjustment start / end switch is a switch for the user to instruct the processing unit 5 to start and end the contrast adjustment operation. For example, a push button switch for notifying the start of the contrast adjustment processing and a stop button are provided. It can be realized by a push button switch for notifying. Alternatively, one push button switch can be used as the contrast adjustment start / end switch 4 in such a manner that a start of the contrast adjustment operation is instructed by the first depression and an end is instructed by the second depression.

The contrast memory 6 is a memory for storing the set value of the contrast. The processing unit 5 reads out the set value in the contrast memory 6 and writes it in the contrast register 1 so that the LCD can store the set value.
The contrast of the screen of the display module 3 is controlled so as to be a contrast corresponding to a preset setting value. Further, the up / down switch 7 is a push button switch operated by the user while performing the contrast gradual change operation according to the feature of the present invention. Specifically, the up-down switch 7 can be realized by a push button switch for instructing to increase the contrast and a push button switch for instructing to decrease the contrast.

FIG. 2 shows a flow of the operation of the processing unit 5 in this embodiment. The procedure shown in FIG.
Is a part related to the contrast adjustment in the procedure executed by the user, and is executed when the user commands the start of the contrast adjustment operation by the contrast adjustment start / end switch 4 (100).

When the start of the contrast adjustment operation is instructed by operating the contrast adjustment start / end switch 4, the processing unit 5 first reads the set value of the contrast from the contrast memory 6 (101), and stores the read set value in the contrast register. 1 and (10
2) Display the read setting values on the screen of the LCD display module 3 (103). LCD display module 3
In the display mode of, for example, as shown in FIG. 3B, the “set value” and the “current contrast” are displayed by a number (gradation value) representing the strength of the contrast. “Set value” in FIG. 3B indicates a set value currently stored in the contrast memory 6, and “current contrast” indicates a value currently stored in the contrast register 1.

However, at this stage, the user cannot always read the “set value” and “current contrast” from the screen of the LCD display module 3. That is,
If the environment surrounding the LCD display module 3, especially the temperature, has changed between the time when the user made the last adjustment (or the time when the manufacturer made the adjustment immediately before shipping) and the present, the contrast memory 6 Often, the above set values are not optimal at the current state of the LCD display module 3. For example, it is assumed that the contrast value of the LCD display module 3 is represented by 16 gradations from 0 to 15, and that the contrast value = 8 is the optimum contrast value at the current ambient temperature. In this case, as shown in the following table, for contrast values less than 8, for example 0,
The entire screen of the LCD display module 3 looks white, and it is impossible or difficult for the user to read the “set value” and the “current contrast” from the screen (FIG. 3).
(A)). Conversely, when the contrast value is larger than 8, for example, 15, the entire screen of the LCD display module 3 looks black, and again, can the user read the "set value" and "current contrast" from the screen? Or it is difficult (see FIG. 3 (c)).

[0023]

[Table 1] Therefore, in the present embodiment, the display of the LCD display module 3 is continued until the user commands the end of the contrast adjustment operation by operating the contrast adjustment start / end switch 4 while continuously performing the display according to step 103. Is executed to gradually change the contrast of. That is, the processing unit 5 increments the content of the contrast register 1 by one (104) and increments the "current contrast" on the screen of the LCD display module 3 by one (105). Until the end of the adjustment operation is commanded (10
6) Execute repeatedly. When the content of the contrast register reaches the maximum value (15 in the example of the above table) as a result of repeatedly executing step 104 (107), the processing unit 5 sets the content of the contrast register 1 to the minimum value (in the example of the above table, 0) (108), and at the same time, the “current contrast” on the screen of the LCD display module 3 is set to the minimum value (109), and the operations from step 104 onward are repeated. Of course, it goes without saying that a similar effect can be obtained even when the value is returned from the maximum value to the minimum value.

In the state where the operation of gradually changing the contrast of the screen of the LCD display module 3 is performed, the contents of the contrast register 1 indicate a periodic change as shown in FIG. . In this figure, t _s is the time the user has commanded the start of the contrast adjustment operation at the contrast adjustment start end switch 4, the t _e is the time that the command completion. Further, in this figure, it is assumed that the value stored as the set value on the contrast memory 6 at time t _s is 2 and that at the end of the adjustment is 4, and the period of the contrast gradual change is determined by the user. Is a time, for example, 2 to 4 seconds during which each step can be easily read.

While the contrast gradual change operation is being performed, the processing unit 5 accepts a command from the user through the up / down switch 7. That is, when the user operates the up / down switch 7 to instruct to increase the contrast, the processing unit 5 increments the set value in the contrast memory 6 by 1 (111), and conversely, instructs to decrease the contrast. Sometimes contrast memory 6
The above set value is decremented by 1 (112). Processing unit 5
Indicates that the display of the “set value” and “current contrast” is continued during the contrast change operation.
On the screen of the LCD display module 3, the contrast value to be gradually changed is set as “current contrast”, and the content of the contrast memory 6, which is appropriately updated by operating the up / down switch 7, is set as “set value”. As it continues to be displayed.

As described above with reference to FIG. 3, if the contrast value deviates from the optimum value for the current ambient temperature, L
Either "set value" or "current contrast" is not displayed on the screen of the CD display module 3, or it is displayed only slightly with difficulty. Conversely, when the contrast gradually changing operation is performed,
Since the user always passes through the contrast value which is considered to be optimal at the current ambient temperature, the user can easily set the “set value” and the “current contrast” during the passing period as shown in FIG. Ready to read. The user reads the display of “set value” and “current contrast” in this state, and operates the up / down switch 7 accordingly.

For example, as shown in FIG.
When the “current contrast” is four times larger than the “set value” (that is, the contrast value that is considered to be optimal at the current ambient temperature is four times larger than the set value currently stored in the contrast memory 6) If it is)
The switch for increasing the contrast among the switches constituting the up-down switch 7 is pressed four times, thereby setting the set value on the contrast memory 6 to 8. At this stage, the user operates the contrast adjustment start / end switch 4 to give a command to the processing unit 5 to end the contrast adjustment operation. In response to this command (106), the processing unit 5 turns off the display of the "set value" on the screen of the LCD display module 3 and "displays the current contrast". Is completed (113).

Therefore, according to the present embodiment, regardless of what the ambient temperature is, and at what temperature the ambient temperature of the LCD display module 3 when the contrast was adjusted last time. Regardless of whether or not the user operates the contrast adjustment start / end switch 4 to start the contrast adjustment operation, a period in which the “set value” and the “current contrast” are clearly displayed on the screen of the LCD display module 3 always occurs. Therefore, the user can adjust the contrast to the optimum value by operating the up / down switch 7 while watching this. In this process, the user does not feel confused or uneasy. Further, since the contrast adjustment start / end switch 4 and the up / down switch 7 can be realized by a push button switch, a device that is more waterproof than a case using a variable resistor and is suitable for outdoor use can be obtained. . The drive voltage generated by the voltage generator 2 is generally a pulse voltage having a predetermined duty ratio. When the duty ratio of the pulse voltage is 1/16 or more, the influence of the change in the ambient temperature on the contrast value of the LCD display module 3 is relatively small. Conversely, when the duty ratio of the drive voltage generated by the voltage generator 2 is 1/16 or less, for example, when the duty ratio is as small as 1/64 or 1/128, the contrast adjustment method according to the present invention is used. The effect becomes particularly remarkable.

FIGS. 5 to 8 show other examples of the screen display of the LCD display module 3 during the execution of the contrast gradually changing operation. In the example shown in FIG. 5, “set value” and “current contrast” are represented not by numerals but by bar-graph-like symbols. In this case, the user can more intuitively know in which direction the up / down switch 7 should be operated in the up / down direction. Further, in the example shown in FIG. 6, not only the “set value” and the “current contrast”, but also the difference between the former and the latter is displayed as “difference”. As described above, when the difference is displayed together, the user can intuitively grasp in which direction the up / down switch 7 should be operated in which direction. In the example shown in FIG.
The display relating to “set value” and “current contrast” is omitted, and only the difference is displayed. In the example shown in FIG. 8, this difference is indicated by a bar-graph-like symbol as in FIG. That is, the method according to the present invention uses the “setting value”
The present invention is not limited to the embodiment displaying both the “current contrast”, but also includes an embodiment displaying only the difference.

(2) Second Embodiment FIG. 9 shows a configuration of a contrast adjustment circuit according to a second embodiment of the present invention. In the present embodiment, the contrast register 1, the processing unit 5, and the contrast register 1, which are provided in the first embodiment,
There is no need to provide the contrast memory 6 and the up-down switch 7. Further, the contrast adjustment start / end switch 4 in the present embodiment is a single push button switch, and the counter 8 operates according to the toggle state of the push button switch, and the drive voltage corresponding to the count value of the counter 8 is controlled. The voltage is generated by the voltage generator 2.

In this embodiment, the contrast adjustment operation by the counting operation of the counter 8 is started by the first operation of the contrast adjustment start / end switch 4, and thereafter the LCD is operated until the contrast adjustment start / end switch 4 is operated again. By operating the counter 8 in a range determined by the maximum and minimum values of the contrast of the display module 3, a contrast gradually changing operation (for example, an operation of gradually changing the contrast from the lightest to the darkest) is executed. The user operates the contrast adjustment start / end switch 4 when determining that the contrast is moderate. When the contrast adjustment start / end switch 4 is operated, it is considered that the first-stage adjustment, that is, the coarse adjustment is completed, and the process shifts to the second-stage adjustment, that is, the fine adjustment. When shifting to fine adjustment, the counter 8 narrows the gradual change range. In other words, the "maximum value" and "minimum value" of the counting range of the counter 8 are reset according to the count value at the time of operating the contrast adjustment start / end switch 4, thereby performing the contrast gradual change operation in the narrower gradual change range. Start.

In the second stage of adjustment, that is, fine adjustment, the speed of increment of the counter 8 may be reduced. That is, if the adjustment is fine, the counting operation of the counter 8 is delayed. The width of the increment in the first stage may be set to 2 or more, and the width of the increment in the second stage may be set to a smaller value. Therefore, the adjustment in the second stage is performed in a state where the gradual change range of the contrast is narrowed and the gradual change speed is slowed. Therefore, in the adjustment in the second stage, the user determines whether or not the contrast has become moderate in the first stage. More detailed judgment can be made as compared with the case of adjusting the stage. When the user determines that the contrast has been improved and operates the contrast adjustment start / end switch 4, the counter 8
Counting operation stops, and the contrast adjustment operation ends. Thereafter, display on the screen of the LCD display module 3 is performed with the contrast indicated by the count value at this time.

As described above, according to the present embodiment, whether to start or end the contrast adjustment operation is determined by the toggle state of the single contrast adjustment start / end switch 4.
Since the distinction is made between the coarse adjustment and the fine adjustment, it is not necessary to perform the display as shown in FIGS. 5 to 8 while the contrast is gradually changed (that is, the point at which the contrast is gradually changed). Except normal display). As a result, the processing unit 5 which is not sufficient only with the counter 8 becomes unnecessary. Further, since it is not necessary to provide the up-down switch 7, the operation of operating the up-down switch 7 is eliminated. The toggle state of the contrast adjustment start / end switch 4 can be determined by a method of setting / resetting a flag for specifying the toggle state of the contrast adjustment start / end switch 4.

Further, when the contrast adjustment is completed, the counter 8 is reversely rotated by a predetermined amount, so that the delay time from when the user views the screen to when the contrast adjustment start / end switch 4 is operated is absorbed, and the user feels uncomfortable. No contrast setting can be achieved.

In this embodiment, since the contrast can be adjusted in two stages of coarse adjustment and fine adjustment, the contrast can be accurately adjusted and set even though the up-down switch 7 is omitted. it can. Especially,
The difference between the “maximum value” and the “minimum value” (that is, the counting range of the counter 8) after the shift to the fine adjustment is displayed on the LCD display module 3.
In addition to the type and the number of gradations, the counter 8 is previously stored in the counter 8 taking into account the delay time (about 50 msec to 200 msec) from when the user views the screen to when the user operates the contrast adjustment start / end switch 4. By setting, the lag time can be absorbed to realize the gradual change range setting without a sense of incongruity. Specifically, the counting range is set to a value larger than the delay time, or the delay time is set to be compensated. The present invention is not limited to the two steps of coarse adjustment and fine adjustment, and can be realized as a configuration capable of performing generally N steps of adjustment including an intermediate adjustment step, but from the viewpoint of simplification of the adjustment operation. It is preferable to use two stages of coarse adjustment and fine adjustment as in the present embodiment. Further, the gradual change range at the time of fine adjustment depends on the type of the LCD display module 3, but is preferably a range having a spread of about four gradations in the case of 16 gradations.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a contrast adjustment circuit according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a flow of a contrast adjustment procedure executed by a processing unit in the first embodiment.

3A and 3B are diagrams illustrating an example of a screen of the LCD display module during a period in which a contrast gradually changing operation is performed. FIG. 3A illustrates a case where the contrast is smaller than an optimum value, for example, 0, and FIG. FIG. 9 is a diagram showing a case where the optimum value is, for example, 8;

FIG. 4 is a diagram showing the contents of a contrast register during a period in which a contrast gradually changing operation is being performed.

FIG. 5 is a diagram showing another example of the screen display of the LCD display module during a period in which the contrast varying operation is being performed.

FIG. 6 is a diagram showing another example of the screen display of the LCD display module during a period in which the contrast gradually changing operation is being performed.

FIG. 7 is a diagram showing another example of the screen display of the LCD display module during a period in which the contrast gradually changing operation is being performed.

FIG. 8 is a diagram showing another example of the screen display of the LCD display module during the period in which the contrast gradually changing operation is being performed.

FIG. 9 is a block diagram illustrating a configuration of a contrast adjustment circuit according to a second embodiment of the present invention.

[Description of Signs] 1 Contrast register, 2 Voltage generator, 3 LC
D display module, 4 contrast adjustment start / end switch, 5 processing unit, 6 contrast memory, 7 up / down switch, 8 counter.

Claims (11)

[Claims] In a contrast adjusting method for setting and changing the contrast of an LCD display whose contrast has temperature dependency in accordance with a command from a user, a level of a drive voltage for driving the LCD display is gradually reduced. Starts the contrast adjustment operation in which the contrast of the LCD display is gradually changed from darkest to lightest or from lightest to darkest in a predetermined cycle by changing the contrast in response to the start and end commands of the contrast adjustment. And while the contrast gradual change operation is being performed, an adjustment index display process of displaying information on the current value and the set value of the screen contrast in characters or symbols on the LCD display screen, and setting of the contrast. Executes the set value update process that changes and saves the contrast set value according to the value change command, and gradually changes the contrast. A contrast adjustment method characterized in that a level of a drive voltage thereafter is determined based on a set value of the contrast at the time when the operation is completed. 2. The contrast adjusting method according to claim 1, wherein the information displayed on the screen of the LCD display during the execution of the contrast gradual change operation is the contrast of the screen at that time with respect to the set value of the contrast. A contrast adjustment method characterized by including a difference between the values of. 3. The contrast adjusting method according to claim 1, wherein the information displayed on the screen of the LCD display while performing the contrast gradually changing operation includes a graph display. A contrast adjustment method characterized by the following. 4. The contrast adjusting method according to claim 1, wherein a command to change the set value of the contrast is given by operating an up-down switch. 5. A contrast adjusting method for setting and changing the contrast of an LCD display having a temperature dependence in accordance with a command from a user, wherein the level of a drive voltage for driving the LCD display is gradually reduced. The contrast gradual change operation of gradually changing the contrast of the screen of the LCD display from the darkest to the lightest or from the lightest to the darkest in a predetermined cycle by changing the contrast adjustment start / end switch is performed. When the contrast adjustment start end switch is operated in a state where the contrast gradual change operation is being executed, the contrast gradual change operation is ended, and the subsequent drive is performed according to the drive voltage level at that time. A contrast adjustment method, which comprises determining a drive voltage level. 6. A contrast adjusting method for setting and changing the contrast of an LCD display having a temperature dependence in accordance with a command from a user, wherein the level of a drive voltage for driving the LCD display is gradually reduced. The contrast gradual change operation of gradually changing the contrast of the screen of the LCD display from the darkest to the lightest or from the lightest to the darkest in a predetermined cycle by changing the contrast adjustment start / end switch is performed. When the contrast adjustment start / stop switch is operated in the state where the contrast gradual change operation is being executed, the range including the contrast corresponding to the drive voltage level at that time is narrower than the previous gradual change range. And the contrast gradual change range is narrowed, and the contrast gradual change speed is On was comb, when continuing the contrast Xu variation operation, the number of operations of the contrast adjustment start end switch after the start of the contrast Xu variation work has reached the predetermined number of times,
A contrast adjusting method, comprising: ending the contrast gradually changing operation and determining a subsequent drive voltage level according to the drive voltage level at that time. 7. The contrast adjusting method according to claim 6, wherein when the contrast gradually changing range is narrowed and the contrast gradually changing operation is continued, a predetermined value is set substantially centering on the contrast corresponding to the drive voltage level at that time. A contrast adjustment method characterized by defining a gradual change range of contrast in a subsequent operation by performing addition and subtraction. 8. The contrast adjusting method according to claim 7, wherein the predetermined value is larger than a shift corresponding to a user operation delay time from when the screen of the LCD display is viewed to when the contrast adjustment start / end switch is operated. A contrast adjustment method characterized in that a value is set in advance. 9. The contrast adjusting method according to claim 7, wherein, when the contrast gradually changing range is narrowed and the contrast gradually changing operation is continued, from the time when the LCD display screen is viewed to the time when the contrast adjustment start / end switch is operated. A contrast adjustment method characterized in that a gradual change range of contrast in a subsequent operation is shifted to one of light and shade so as to compensate for a shift corresponding to a user operation delay time. 10. The contrast adjusting method according to claim 6, wherein the predetermined number of times is two. 11. The contrast adjusting method according to claim 5, wherein, when the contrast gradual change operation is ended, a user operation delay time from when the LCD display screen is viewed to when the contrast adjustment start / end switch is operated is set. A contrast adjustment method characterized in that the level of the drive voltage is determined by adjusting the level of the drive voltage to be higher or lower so that a corresponding shift is compensated.