Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1999-06-29
2002-05-14
Mathews, Alan A. (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C359S107000, C359S199200, C359S199200
Reexamination Certificate
active
06386708
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a projection display device having a control circuit substrate on which a control circuit is mounted for controlling driving of the device according to an input operation signal from an external apparatus connected to the device, and particularly to a projection display device having a structure in which a signal transmission element having an opposite light emitting element and light receiving element is provided in a passage for transmitting an external input signal to a control circuit on a control circuit substrate.
2. Description of Related Art
When a signal generated in a first circuit substrate is transmitted from the first circuit substrate to a second circuit substrate and decoded by signal decoding means arranged on the second circuit substrate, it is generally necessary to draw a wire cable such as a lead wire from the first circuit substrate to the second circuit substrate. Namely, communication between the circuit substrates is performed by using electric signals. In this case, where the distance between the first circuit substrate and the second circuit substrate is relatively long, or electrical noise occurs between the first circuit substrate and the second circuit substrate, means for intensifying electric signals or means for removing noise is required. Further, where the voltage of an electric signal handled in the first circuit substrate is different from that in the second circuit substrate, means for converting the voltage of an electric signal is required.
In a product such as a projection display device, in which various electric devices and optical systems are arranged in a compact device case, and many circuits are arranged for controlling driving of these devices, a plurality of circuit substrates must be arranged, thereby requiring signal transmission and reception between the circuit substrates. Conventionally, the circuit substrates are connected by cables so that such signal transmission and reception is carried out by using electric signals.
However, in realization of miniaturization of a product (device), miniaturization is difficult because a space is required for providing a connector for connecting cables and for drawing the cables between a first circuit substrate and a second circuit substrate, for example, in order to transmit a signal from the first circuit substrate to the second circuit substrate.
Where a relatively large electric noise occurs in the product, or a long cable must be used, it is necessary to arrange a transmission buffer on the first circuit substrate and a receiving buffer and means (noise filter) for removing noise on the second circuit substrate. Particularly, the projection display device has noise sources such as a light source lamp driven at a high voltage, and an image signal processing circuit for handling digital signals, and thus requires such buffers and noise removing means.
Furthermore, where the voltage of an electric signal handled by the first circuit substrate is different from that in the second circuit substrate, means for converting the voltage is also required.
Arrangement of the buffers, the noise removing means and the voltage converting means on the circuit substrates not only interferes with miniaturization of the product but also causes an increase in the product cost.
SUMMARY OF THE INVENTION
The present invention has been achieved in consideration of the above problem, and an object of the invention is to provide means for communication between circuit substrates, which permits miniaturization of a device and cost reduction.
In order to achieve the object, a projection display device of the present invention includes a light source; an optical system for optically processing the light emitted from the light source to form an optical image corresponding to image information; a projection lens for projecting the image formed by the optical system on a projection plane; a device case for containing at least the light source and the optical system; a control circuit substrate contained in a predetermined space in the device case, for mounting a control circuit for controlling drive of the device; an external apparatus connecting terminal provided on the control circuit substrate so that the control circuit is operated by an input operation signal from an external apparatus; and a signal transmission circuit including a light emitting element and a light receiving element and provided in an external input signal transmission passage between the terminal and the control circuit; the control circuit substrate including a first circuit substrate on which the control circuit and the light receiving element are provided, and a second circuit substrate which is arranged opposite to the first circuit substrate, and on which the external apparatus connecting terminal and the light emitting element are provided.
Since the control circuit substrate includes the first and second circuit substrates, a space for mounting electronic components on the control circuit substrate is extended.
Since the light emitting element and light receiving element serving as a signal transmission circuit are provided opposite to each other between the first and second circuit substrates, a space for mounting electronic components on each of the circuit substrates is also extended.
Since a plurality of circuit substrates are provided, various external apparatus connecting terminals can be provided on the circuit substrates. Also, since the external apparatus connecting terminal is provided on the second circuit substrate without the control circuit, many other external apparatus connecting terminals can be provided on the first circuit substrate.
Since a medium for communication from the first circuit substrate to the second circuit substrate comprises optical signals, there is no need for a space for providing a connector for connecting cables and drawing the cables between the first circuit substrate and the second circuit substrate, thereby permitting close arrangement of the first and second circuit substrates. In addition, since optical signals are not affected by noise sources such as a light source lamp driven at a high voltage and an image signal processing circuit, there is no need for a buffer and noise removing means, which are needed in a conventional device.
Even when the voltage of a signal handled by the first circuit substrate is different from that in the second circuit substrate, the voltage of a signal can be changed by using the light emitting element and the light receiving element having desired photoelectric conversion efficiency, and thus another voltage converting means need not be provided.
Therefore, the present invention causes extension of a space for mounting electronic components, and a decrease in a space for containing the control circuit substrate, thereby achieving high-density mounting and a compact device. Also, the degree of layout freedom for arrangement of other external apparatus connecting terminals is increased.
In the projection display device of the present invention, the first circuit substrate preferably comprises a main circuit substrate on which the control circuit is mounted, and a sub-circuit substrate electrically connected to the main circuit substrate, disposed between the main circuit substrate and the second circuit substrate, and provided with the light receiving element.
Since the control circuit substrate comprises the three circuit substrates, the space for mounting electronic parts is further extended, and more external apparatus connecting terminals can be provided on the circuit substrates.
Therefore, it is possible to achieve higher-density mounting or more compact control circuit substrate, that is, a more compact device.
In the projection display device of the present invention, the light receiving element is preferably provided on a side of the first circuit substrate which faces the second circuit substrate with the light receiving plane parallel to the first circuit substrate,
Arai Jun
Suyama Masayuki
Tominaga Akira
Fuller R.
Mathews Alan A.
Seiko Epson Corporation
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