Bar code reader head

Abstract

A bar code reader head having an optical block with cavities formed therein into which various optical elements may be placed without the need for any adjustment thereof. A first illumination source, producing any desired spectrum of light, illuminates at least a portion of the bar code. A second illumination source may be provided to produce a second spectrum of light. Reflected light passes through a lens in front of which is an aperture slit parallel to the bar code bars. A channel is formed between the lens and a photodetector perpendicular to the light path. If both visible and infrared illumination sources are used, visible light is focused at the side of the channel toward the lens and infrared light is focused at the other side of the channel. In the channel is a template having at least one discriminator slit parallel with the slit in front of the lens. The width of the discriminator slit depends upon the widths of the bars to be read. With visible light, the template is positioned with the slit at the side toward the lens. With infrared light, the template is positioned with the slit at the other side. Alternatively, a specially designed lens may be employed to focus both visible and infrared light at one side of the channel. The template may have additional slits for changing the resolution of the device by moving the template to align a slit having a different width with the light path, thus allowing use of the device with different bar codes having substantially different bar widths.