Low EMI multiplexed dual display

• US 6,346,698 B1
• Filed: 07/22/1999
• Issued: 02/12/2002
• Est. Priority Date: 07/22/1999
• Status: Expired due to Term

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Turnbull, Robert R.
• Primary Examiner(s): Lee, John R.
• Application Number:
  US09/359,616
• Time in Patent Office: 936 Days
• Field of Search: 250/205, 250/216, 250/208.1, 250/214.R, 307/9.1, 307/10.1, 333/172, 333/181, 333/12, 313/497, 359/265, 359/266, 359/267, 359/604, 359/838, 359/843, 359/884
• US Class Current: 250/214.00R
• CPC Class Codes: B60R 2001/1215 with information displays
• CPC Class Codes: G02B 5/23 Photochromic filters

Abstract

A mirror assembly having an electrically adjustably reflectivity provides for the simultaneous display of a vehicle heading and an external temperature. The mirror assembly includes a reflective device, a dual display and a control circuit. The reflective device includes a transmissive element and a reflective surface formed on the transmissive element. The dual display is located behind the reflective surface of the reflective device. The dual display visually provides the vehicle heading and the external temperature through the reflective device. The control circuit provides for the variable attenuation of light through the transmissive element of the reflective device and controls the intensity and information displayed by the dual display. An advantage of the present invention is that it provides a dual display while exhibiting currently acceptable electromagnetic interference levels.

Claims

1. A mirror assembly having an electrically adjustable reflectivity, the mirror assembly providing for the simultaneous display of a vehicle heading and an external temperature, the mirror assembly comprising:

a reflective device that includes a transmissive element and a reflective surface formed on the transmissive element;

a dual display located behind the reflective surface of the reflective device, the dual display visually providing the vehicle heading and the external temperature through the reflective device; and

a control circuit which provides for the variable attenuation of light through the transmissive element and controls the intensity and information displayed by the dual display, the control circuit alternately providing the vehicle heading and the external temperature to the dual display, the control circuit exhibiting an electromagnetic interference level less than about 41 dBuV/m for emissions in the frequency range from about 0.4 MHz to about 20 MHz.

2. The mirror assembly of claim 1, wherein the control circuit further includes:

a first power supply filter coupled between a first power supply and a dual display driver; and

a second power supply filter coupled between a second power supply and the dual display,

and wherein the first and second power supply filters function to reduce the electromagnetic interference level exhibited by the control circuit.

3. The mirror assembly of claim 2, wherein the second power supply is derived from the first power supply.

4. The mirror assembly of claim 1, wherein the control circuit further includes:

a light sensor which senses ambient and glare light levels;

a dual display driver which provides a vehicle heading signal and an external temperature signal to the dual display; and

an intensity circuit which adjusts the reflectivity of the reflective device and intensity of the dual display responsive to the light sensor.

5. The mirror assembly of claim 4, wherein the electromagnetic interference level exhibited by the control circuit is less than about 28 dBuV/m for narrowband emissions in the frequency range from about 0.4 MHz to about 20 MHz.

6. The mirror assembly of claim 1 further including a housing, wherein the vehicle heading is provided by a compass circuit mounted in the housing.

7. The mirror assembly of claim 1, wherein the reflectivity of the reflective device is adjusted based on an ambient light level.

8. The mirror assembly of claim 1, wherein the reflectivity of the reflective device is adjusted based on a glare light level.

9. The mirror assembly of claim 1, where the reflectivity of the reflective device is adjusted based on both an ambient light level and a glare light level.

10. The mirror assembly of claim 1, wherein the reflective surface includes a window opening through which the dual display is visible.

11. The mirror assembly of claim 1, wherein the reflective surface includes a window opening in which the reflective surface is partially removed such that the dual display is visible.

12. The mirror assembly of claim 1, wherein the transmissive element includes an electrochromic medium.

13. The mirror assembly of claim 1, wherein the dual display is a vacuum fluorescent display.

14. A method for simultaneously displaying a first readout and a second readout through a window in an electrically adjustable reflective mirror assembly while producing an electromagnetic interference level less than about 41 dBuV/m for emissions in the frequency range from about 0.4 MHz to about 20 MHz, the first readout and second readout being simultaneously displayed on a dual display, the method comprising:

(a) providing power supply filters to reduce EMI levels;

(b) providing a first readout signal to a dual display drive circuit;

(c) updating the first readout based on the first readout signal using the dual display driver circuit;

(d) providing a second readout signal to the dual display drive circuit;

(e) updating the second readout based on the second readout signal using the dual display driver circuit; and

(f) repeating steps (b) through (e) when the first and second readout are active.

15. The method of claim 14, wherein the power supply filters are provided on power supply lines of the dual display and the dual display driver circuit.

16. The method of claim 14, wherein the first readout and the second readout are provided at a rate of approximately 150 times per second.

17. The method of claim 14, wherein the first and second readout signal are provided in serial form.

18. The method of claim 14, wherein the dual display is a vacuum fluorescent display.

19. The method of claim 14, wherein the electrically adjustable reflective mirror assembly includes an electrochromic transmissive element.

20. The method of claim 14, wherein the first readout includes a vehicle heading provided by a compass circuit and the second readout includes a temperature provided by a temperature circuit.

21. The method of claim 14, wherein the electromagnetic interference level is less than about 28 dBuV/m for narrowband emissions in the frequency range from about 0.4 MHz to about 20 MHz.