JPS589390B2 - Hatsuko Soshi Hiyouji Udedo Keino Kidohenchiyousouchi - Google Patents

Description

[Detailed description of the invention] The present invention relates to a brightness modulation device for a light emitting element display wristwatch.

2. Description of the Related Art Wristwatches that display time digitally using light emitting elements such as light emitting diodes are being developed.

Such wristwatches are designed to extend the life of the battery by pressing a switch to light up the light emitting element to display the time, since the light emitting element consumes a large amount of current.

As described above, battery life is a particularly important issue in this type of wristwatch.

The present invention aims to change the brightness of a light emitting element depending on the illuminance of ambient light, thereby reducing current consumption and extending battery life.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a cross-sectional model structure of a wrist watch body to which the present invention is applied.

In this figure, the case of the watch is omitted.

According to FIG. 1, a reference frequency source 2 for a crystal oscillator and an integrated circuit 3 for measuring time by dividing the reference frequency are fixed to the back surface of a ceramic substrate 1 on which a conductive path is formed and sealed with a resin layer 4. .

Further, on the upper surface of the ceramic substrate 1, a light emitting element 5 composed of a light emitting diode or the like for displaying numbers, a phototransistor 6 which is a feature of the present invention, and a substance that blocks infrared rays is attached to the surface of the glass or the like provided on the upper surface of the phototransistor 6. An infrared cutoff filter 7 is fixed.

Batteries 8, 8 are housed in a resin frame 9, and although not shown, supply power to the integrated circuit 3 and light emitting element 5 described above.

Furthermore, this frame 9 also supports the ceramic substrate 1, and the frame 9 is fixed to the case of the watch.

The light emitting element 5 is GaP or G that emits red light.
Since an aAsP light emitting diode is used, a red transmission filter 10 fixed to the watch case is provided on the top surface of the light emitting element 5 and phototransistor 6.

FIG. 2 is a block diagram illustrating the brightness modulation device of the present invention.

Reference numeral 11 denotes a light sensor, which corresponds to the phototransistor described above.

Reference numeral 12 denotes a duty modulation circuit which modulates the pulse width of a pulse for lighting the light emitting element to change the brightness of the light emitting element.

Reference numeral 13 denotes a driver circuit that lights up the light emitting element, and lights up the light emitting element using time information from the integrated circuit and pulses from the duty modulation circuit described above.

14 is a time display device composed of a light emitting element.

As mentioned above, the feature of the present invention lies in a portion of the optical sensor, and the operation of the present invention will be explained below with reference to the characteristic diagrams shown in FIGS. 3 to 6.

Curve A shown as a solid line in FIG. 3 is the spectral sensitivity characteristic of the phototransistor used in the present invention, and is
It can be seen that there is a peak at 0 Å.

Curve B shown by a broken line is the spectral transmittance characteristic of the red transmission filter, which transmits light with a wavelength of about 6000 Å or more.

Curve C shown by a dotted line is the spectral transmittance characteristic of the infrared cutoff filter used in the present invention, which blocks light with a wavelength of about 7000 Å or more.

Next, FIG. 4 shows the characteristics of fluorescent lamps and tungsten filament incandescent lamps, which are often used for night lighting, when they pass through a red transmission filter.

Curve D shown by a solid line is the spectral brightness characteristic of a fluorescent lamp after passing through a red transmission filter, and curve E shown by a broken line is a spectral brightness characteristic of an incandescent lamp after passing through a red transmission filter.

From FIG. 4, it is clear that, according to human vision, an incandescent light bulb has a sufficiently larger infrared portion even if the illuminance is the same.

Therefore, when ambient light is detected only by a phototransistor through a red transmission filter without using an infrared cutoff filter, the output sensitivity of the phototransistor is as shown in Figure 5 because the phototransistor has a peak in the infrared region. In the case of an incandescent lamp, a curve F is shown as a solid line, and in the case of an incandescent lamp, a curve G is shown as a broken line.

In other words, although the illuminance is the same for human vision, the output of the phototransistor, which is a light sensor, is much larger for an incandescent light bulb, which does not match human vision.

According to the present invention, the infrared part of the incandescent light bulb is blocked by the action of the infrared cutoff filter, so as shown in FIG. This substantially coincides with the broken line curve I, which is the output sensitivity.

Therefore, even if a phototransistor is used, if an infrared cutoff filter is provided on the top surface of the phototransistor, characteristics approximately proportional to human vision can be obtained even if the light source of the night illumination is different.

As described in detail above, according to the present invention, it is possible to perform brightness modulation of various night lighting light sources in proportion to human visual perception using an inexpensive phototransistor through the action of an infrared cutoff filter.

Therefore, the same brightness can be obtained with the same illuminance for human vision, and the unnecessary increase in the brightness of the light emitting element due to the output of the phototransistor due to infrared rays can be completely eliminated, and the life of the battery can be extended.

Furthermore, by removing infrared rays with an infrared cutoff filter, it is possible to prevent the temperature of the phototransistor from increasing due to the infrared rays, and it is also possible to compensate for the shift in the operating point due to the increase in the temperature of the phototransistor.

In the present invention, the infrared ray blocking filter may be formed by depositing a substance that blocks infrared rays on the surface of a red transmitting filter or a phototransistor.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional model diagram of a wrist watch body to which the present invention is applied, FIG. 2 is a block diagram illustrating the present invention, and FIGS. 3 to 6 are curve diagrams illustrating the operation of the present invention. 1 is a ceramic substrate, 2 is a reference frequency source, 3 is an integrated circuit, 4 is a resin layer, 5 is a light emitting element, 6 is a phototransistor, 7 is an infrared cutoff filter, 8 is a battery, 9 is a frame body, 1
0 is a red transmission filter, 11 is a light sensor, 12 is a duty modulation circuit, 13 is a driver circuit, and 14 is a time display device.

Claims (1)

[Claims] 1. In a wristwatch that includes a reference frequency source, an integrated circuit that measures time by dividing the reference frequency, a battery, and a light emitting element that displays the time, a phototransistor and an infrared cutoff filter provided on the top surface of the phototransistor are used. A brightness modulation device for a light-emitting element display wristwatch, comprising: detecting ambient light by the phototransistor through the filter to change the brightness of the light-emitting element.