Bar code scanner using a hologram disk and having detachable and adjustable optical elements

An information reader for reading information on an article comprising:

• a light source for emitting a light beam;
• means for detecting said light beam after it is reflected from said article;
• a rotatable circular hologram disk for scanning said light beam in two dimensions and guiding said reflected light beam to said detecting means;
• means for deflecting said light beam emitted from said light source toward said hologram disk;
• and
• a housing for receiving said light source, said detecting means, said hologram disk and said deflecting means therein,
• wherein said light source and said deflecting means are integrally detachable from said housing,
• wherein said circular hologram disk has a first hologram and a second hologram which have differemt focal lengths and different diffraction angles, each of said first and second holograms circumferentially extending along half of a full circumference of said circular hologram disk.

An information reader for reading information on an article, comprising:

• a light source for emitting a light beam;
• means for detecting said light beam after it is reflected from said article;
• a rotatable circular hologram disk scanning said light beam in two dimensions and directing said reflected light beam toward said detecting means;
• a condenser lens collecting said light beam after it is reflected from said article and focussing said light beam on said detecting means, said condenser lens facing to said circular hologram disk;
• means for deflecting said light beax emitted from said light source toward said circular hologram disk;
• and
• a housing for receiving said light source, said detecting means, said circular hologram disk, said condenser lens and said deflecting means therein, and
• wherein a radius of said condenser lens is smaller than a radius r of expanse of an unwanted light beam, the radius r being given as follows:
• r=h/tan.theta.
• wherein, .theta. denotes an angle of departure of said unwanted light beam to said circular hologram disk;
• and h denotes a distance between said condenser lens and said circular hologram disk.

An information reader for reading information on an article, comprising:

• a light source for emitting a light beam;
• means for detecting said light beam after it is reflected from said article;
• a rotatable circular hologram disk having a first surface and a second surface opposite to said first surface, scanning said light beam in two dimensions, and guiding said light beam reflected to said detecting means;
• a condenser lens collecting said light beam after it is reflected from said article and focusing said light beam on said detecting means, said condenser lens facing said first surface;
• means for deflecting said light beam emitted from said light source toward said first surface;
• and
• a housing for receiving said light source, said detecting means, said circular hologram disk, said condenser lens and said deflecting means therein, and
• wherein an unwanted light beam is reflected from said first surface, said unwanted light beam is a light beam which is also diffracted at said second surface without being reflected from said second surface, and a radius of said condenser lens is smaller than a radius of expanse of said unwanted light beam on a plane on which said condenser lens is installed.