Data symbol reader utilizing ambient light illumination
First Claim
1. A data symbol reader, comprising:
- an image sensing device;
an optical system for forming an image of a data symbol, located in a symbol reading area, on said image sensing device;
a light source for illuminating the symbol reading area;
a luminance detector, for detecting a luminance in the symbol reading area;
a light source driving circuit for controlling a quantity of light emitted by the light source in accordance with a detected luminance in the symbol reading area wherein said light source driving circuit comprises;
comparing means for comparing said detected luminance with a predetermined luminance level of an acceptable luminance range, wherein said predetermined luminance level is one of an upper limit and a lower limit of said acceptable luminance range;
first adjusting means for adjusting the quantity of light emitted by said light source, in response to said comparison of said detected luminance with said lower limit of said acceptable luminance range, said first adjusting means increasing the quantity of light emitted by said light source until said detected luminance reaches said lower limit of said acceptable luminance range; and
second adjusting means for adjusting the quantity of light emitted by said light source, in response to said comparison of said detedted luminance with said upper limit of said acceptable luminance range, said second adjusting means decreasing the quantity of light emitted by said light source until said detected luminance reaches said upper limit of said acceptable luminance range; and
a casing, at least said image sensing device, said optical system, said light source and said luminance detector being positioned in said casing, said casing provided with walls which contact a surface on which the data symbol is located to read the data symbol, said casing further including an ambient light window for introducing ambient light into said symbol reading area,said luminance detector being responsive to both said ambient light and to illumination from said light source.
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Accused Products
Abstract
A casing, including a grip portion and a head portion, houses a pair of light sources for illumination, an image sensing device, an optical system for forming an image on the image sensing device, a photosensor for detecting the luminance of symbol reading area, a signal processing circuit, and a light quantity detection circuit. The housing extends from the head portion towards the symbol reading area. An ambient light window is provided in the housing for introducing ambient light into the symbol reading area. A light source driving circuit controls an amount of light emitted by the light source, by increasing or decreasing the amount of light, such that the combined ambient light and light source illumination is between predetermined levels. A selector is provided for selecting between a first mode, in which a maximum illumination is decreased to an upper limit of an acceptable illumination range, and a second mode, in which a minimum illumination is increased to a lower limit of an acceptable illumination range.
162 Citations
25 Claims
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1. A data symbol reader, comprising:
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an image sensing device; an optical system for forming an image of a data symbol, located in a symbol reading area, on said image sensing device; a light source for illuminating the symbol reading area; a luminance detector, for detecting a luminance in the symbol reading area; a light source driving circuit for controlling a quantity of light emitted by the light source in accordance with a detected luminance in the symbol reading area wherein said light source driving circuit comprises; comparing means for comparing said detected luminance with a predetermined luminance level of an acceptable luminance range, wherein said predetermined luminance level is one of an upper limit and a lower limit of said acceptable luminance range; first adjusting means for adjusting the quantity of light emitted by said light source, in response to said comparison of said detected luminance with said lower limit of said acceptable luminance range, said first adjusting means increasing the quantity of light emitted by said light source until said detected luminance reaches said lower limit of said acceptable luminance range; and second adjusting means for adjusting the quantity of light emitted by said light source, in response to said comparison of said detedted luminance with said upper limit of said acceptable luminance range, said second adjusting means decreasing the quantity of light emitted by said light source until said detected luminance reaches said upper limit of said acceptable luminance range; and a casing, at least said image sensing device, said optical system, said light source and said luminance detector being positioned in said casing, said casing provided with walls which contact a surface on which the data symbol is located to read the data symbol, said casing further including an ambient light window for introducing ambient light into said symbol reading area, said luminance detector being responsive to both said ambient light and to illumination from said light source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A data symbol reader, comprising:
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an image sensing device; an optical system for forming an image of a data symbol, located in a symbol reading area, on said image sensing device; a light source for illuminating the symbol reading area; a luminance detector, for detecting a luminance in the symbol reading area; a light source driving circuit for controlling a quantity of light emitted by the light source in accordance with a detected luminance in the symbol reading area; and a casing, at least said image sensing device, said optical system, said light source and said luminance detector being positioned in said casing, said casing provided with walls which contact a surface on which the data symbol is located to read the data symbol, said casing further including an ambient light window for introducing ambient light into said symbol reading area; said light source driving circuit comprising means for comparing said detected luminance with a predetermined luminance level, said predetermined luminance level being a lower limit of an acceptable luminance range; and adjusting means for adjusting the quantity of light emitted by said light source, in response to said comparison of the detected luminance with said lower limit, said adjusting means increasing the quantity of light emitted by said light source until the detected luminance reaches said lower limit; said adjusting means first setting the quantity of light emitted by said light source to a minimum level before increasing the quantity of light emitted by said light source until said detected luminance reaches said lower limit. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A data symbol reader, comprising:
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an image sensing device; an optical system for forming an image of a data symbol, located in a symbol reading area, on said image sensing device; a light source for illuminating the symbol reading area; a luminance detector, for detecting a luminance in the symbol reading area; a light source driving circuit for controlling a quantity of light emitted by the light source in accordance with a detected luminance in the symbol reading area; and a casing, at least said image sensing device, said optical system, said light source and said luminance detector being positioned in said casing, said casing provided with walls which contact a surface on which the data symbol is located to read the data symbol, said casing further including an ambient light window for introducing ambient light into said symbol reading area; said light source driving circuit comprising means for comparing said detected luminance with a predetermined luminance level, said predetermined luminance level being an upper limit of an acceptable luminance range, and adjusting means for adjusting the quantity of light emitted by the light source, in response to said comparison of said detected luminance with said upper limit, said adjusting means decreasing the quantity of light emitted by the light source until the detected luminance reaches said upper limit, said adjusting means first setting the quantity of light emitted by said light source to a maximum level before decreasing the quantity of light emitted by said light source until said detected luminance reaches said upper limit. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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Specification