JPH035247A - Dimmer device - Google Patents

Abstract

PURPOSE:To improve resolving power and smoothly control light when a ripple signal is superposed on a detected output to improve the resolving power at digital conversion of the detected output by instituting the wave form of ripple signal laid upon asymmetry based at sampling. CONSTITUTION:The head up display device of an automobile is fundamentally composed of a detecting part 1, a processing part 2, and a display part 3. Detected and processed running information is displayed on the half mirror part 32 of a front glass. In a dimmer, the output detected with a light sensor 11 and amplified with an amplifying part 12 is processed with a CPU 21 to decide display brightness, hereby a driving part 31 is controlled. Further, the detected output is superposed on a ripple signal from a ripple generator 22, hereafter digital-converted to improve resolving power. In this case, the wave form of the ripple signal is instituted asymmetry based at sampling for digital conversion of the signal to be superposed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Applications! 7) The present invention mainly relates to a light control device used in a display device that displays driving information by light reflection on the windshield of a vehicle.

(Problems to be solved by conventional technology and invention) Vehicle speed,
Driving information such as mileage, remaining fuel level, etc. was previously displayed on meters installed on the instrument panel, but recently drivers have changed their driving style so that they do not have to take their eyes off the road ahead to view this information. A display device called a head-up display is used, which allows information to be visually recognized by forming an image in the front field of view of the windshield so that it overlaps with the foreground in the field of view.

In the display device, the brightness of the back shadow itself of the display portion is the brightness of the front of the vehicle, and by changing the brightness of the back shadow,
It is equipped with a light control device that adjusts the display brightness so that the display itself does not become difficult to see.
No. 333, JP-A No. 62-50239). This light control device detects the brightness of external light using a light sensor installed on the back of the rearview mirror or at the bottom of the windshield, and adjusts the display brightness according to the detected output. Since the display brightness, brightness pattern, etc. are determined by arithmetic processing by a CPU or the like, the detection output is first converted into a digital signal and then subjected to arithmetic processing. When converting this detection output into a digital signal, sampling takes out the values of the detection output at regular time intervals)
A so-called sample hold is performed in which this sampled value is held at that value until the next sampling. However, if the value of the detection output is sampled and held as is, the resolution of the detection output corresponds to the least significant digit of the digital value. Therefore, in order to improve the resolution, a ripple signal having an amplitude corresponding to the lowest digit during digital conversion is superimposed on the detection output signal, and sample and hold is performed based on the superimposed signal. That is, if we take out and explain the minimum number unit part during digital conversion, as shown in FIG. 4, α is less than or equal to the minimum number unit (ILSB) of the detection output. =0. β.

= 174. γ.

= 274. δ. = 374, both are sampled and held as "0". Add to this the quantization error -L
Arithmetic processing is performed using the value plus the LSB. However, the above a.
,β. , γ. , δ. When the ripple signal A is superimposed on the detection output of , the superimposed signals become α1 to δ shown in FIG. Therefore, if it is assumed that the sampled values at times b, c, and d are held for each time A, B, C, and D, the sample and hold values are as shown in the table below.

Table ■〉 The value to be determined is the average value, ten quantization errors, and therefore the output corresponding to the display brightness fluctuates at a high frequency that is not perceptible to the human eye. Therefore, the display brightness is the average of the desired values, so it can be detected. The resolution of the display degree adjustment for the output is approximately twice that of the case where the ripple signal is not superimposed, that is, the minimum unit in digital conversion (IL
It has a resolution of 172 (SB).

The present invention proposes a means to further improve resolution.

(Means for Solving the Problems) A light control device according to the present invention includes a detection section having an optical sensor;
It consists of a processing section that superimposes a ripple signal on the detection signal from the detection section, converts the superimposed signal into digital, and performs arithmetic processing to output a predetermined drive instruction signal, and a drive section that performs a predetermined dimming operation based on the drive instruction signal. The light control device is characterized in that the ripple signal has an asymmetrical waveform with reference to the sampling time for digital conversion of the superimposed signal.

(Function) When the ripple waveform is asymmetric with respect to the sampling time, for example, the ripple waveform itself is an asymmetric wave, or the ripple waveform itself is a symmetrical wave but is asynchronous to the sampling time, and the ripple waveform itself is asymmetrical. This method performs superimposition in which the amount of superimposition is not the same, and due to the diversification of changes in the amount of superimposition, the minimum digit [0
, IJ are also diversified, and the resolution based on the average output of the drive output that determines display brightness is improved.

(Example) Next, the present invention will be explained in detail.

A display device called a head-up display device to which the present invention is applied basically includes a detection section 1 and a processing section 22.
It consists of a display section 3, and a detection section 1 outputs resensor detection outputs from various sensors installed in various parts of the vehicle to a processing section 2 in order to obtain driving information such as vehicle speed, mileage, remaining fuel amount, etc. The processing section 2 is composed of a CPU, etc., and changes the detection output of the detection section into a signal that is easy to process, and also controls the operation of the display section, such as the information to be displayed, that is, the characters and figures to be displayed, and the display brightness. The display section 3 includes a drive section 31 that is driven by the processing section 2 to emit display light, and a display half mirror 32 that displays information.

Various information necessary for driving is displayed on the half-mirror part 32 of the windshield, and the driver visually recognizes this.
This is to obtain the desired information.

The present invention is a light control device for adjusting display brightness applied to the head-up display device described above, and by performing light control, the display can be displayed with a predetermined optimum contrast ratio even if there are fluctuations in external light. The light control device has the detection section 1 equipped with an optical sensor 11 and an amplification section 12, and upon receiving input from the optical sensor of the detection section 1, the processing section 2 performs predetermined processing to adjust the display brightness. After determining, the drive unit 3 of the display unit 3
1, and the amplified output (detection output) from the optical sensor l is sent to the cpu2 of the processing unit 2.
During digital conversion before performing the arithmetic processing in step 1, the processing unit 2 is equipped with a ripple generator @ 22, the ripple signal from the ripple generator 22 is superimposed on the detection output (analog amount), and the ripple signal from the ripple generator 22 is superimposed on the detection output (analog amount), and after the superposition, digital conversion is performed. This increases the resolution. The present invention is characterized in that the superimposed ripple signal is a signal that is asymmetrical with respect to the sampling time. As a specific example, a case where ripple signal ports having an asymmetrical waveform as shown in FIG. 2 are superimposed will be described next.

The minimum value of the digital value of the output of the detection unit 1 (optical sensor detection output) is, for example, αG-0. β.

=174. γ. −274, δ. -374, and if a ripple signal port with an asymmetrical waveform is superimposed on this, the superimposed signal α1
．． β3. γ8. δ is the graph on the right side of Figure 2.

Therefore, if each time a, b, c, and d are sampling times, and the sampling value at 8 o'clock is held for a period of time (A time) until the next sampling time at 5 o'clock, the sample hold value between A and D is as follows. As shown in the table.

Therefore, compared to the conventional case shown in Table I, the resolution is twice that of the conventional case, that is, a resolution that is 1/4 of the minimum value (ILSB) in the case of digital conversion can be obtained.

Next, as shown in Fig. 3, an example in which the ripple signal (ripple signal) is a triangular wave (symmetrical waveform) and is not synchronized with the sampling time will be explained. As in the case of the asymmetrical waveform described above, the detection output α
. −〇、β. = 174. γ. −274°δ. The superimposed signal of the ripple signal C on =3C is α8. β8. γ3.
δ, the sample and hold values are as shown in the table below.

Table ■〉 As in the example of the asymmetric waveform described above, the resolution is qLsB.

The present invention provides a means for superimposing a ripple signal on the output of the detection unit 1 (optical sensor detection output) and digitally converting (quantizing) the superimposed signal to increase the resolution. This is a proposal of technical ideas, and the detection unit 1. The specific structures of the processing section 2 and display section 3 are as follows:
As long as the above-mentioned technical idea of the present invention can be realized, it can be determined completely arbitrarily. Further, the ripple signal waveform is not limited to the asymmetric waveform or asynchronous triangular wave described above, and any waveform may be selected as long as the amount of superimposition during sampling is not the same, such as a sawtooth wave.

(Effects of the Invention) As described above, the present invention mainly resides in a light control device that adjusts the display brightness of a head-up display device, and in particular superimposes a ripple signal in order to improve resolution when converting a detection output into digital. In this method, the waveform of the ripple signal to be superimposed is made asymmetrical with respect to the sampling time, and the resolution is improved compared to the conventional method that uses symmetrical waves, resulting in smoother tuning. It is made possible by light.

[Brief explanation of the drawing]

FIG. 1 is a simple block diagram of a head-up display device including a light control device according to the present invention, FIG. 2 is a signal waveform diagram showing a superimposed state when the present invention is implemented, and FIG. FIG. 4 is a waveform diagram showing another embodiment of the present invention, and FIG. 4 is a waveform diagram of a conventional example. 1 is a detection section 11 is a light sensor 12 is an amplification section 2 is a processing section 21 is a CPU 22 is a ripple generator 3 is a display section 31 is a drive section 32 is a half mirror

Claims (1)

[Claims] (1) a detection section having an optical sensor; a processing section that superimposes a ripple signal on the detection signal from the detection section, digitally converts the superimposed signal, and performs arithmetic processing to output a predetermined drive instruction signal;
A light control device comprising a drive section that performs a predetermined light control operation in response to a drive instruction signal, characterized in that the ripple signal has an asymmetric waveform with reference to the sampling time for digital conversion of the superimposed signal. dimmer device.