Scanner of a Bar Code Verifier

1. Field of the Invention

This invention relates to a bar code verifier designed to check if a bar code disposed on a package or some other object typically by printing meets the requirements of a given standard and, more particularly, it relates to a scanner of such a machine for reading the bar code.

2. Background Art

Japanese patent Laid-Open publication No. 5-120462 discloses a scanner for reading a bar code. This known scanner is provided with a viewing window where a dichroic mirror which is arranged so that the operator can ensure that the scanner is properly placed relative to the bar code to be read.

The dichroic mirror may be so designed as to reflect only rays of red light emitted from a red-light emitting device (red-LED) housed within the scanner and allows rays of light having a wavelength shorter than that of red light to pass therethrough. Consequently any external rays of light having a wavelength close to that of red light emitted from the light source (LED) are reflected by the outer surface of the dichroic mirror and not allowed to enter the scanner whereas rays of light having a relatively short wavelength are allowed to enter and pass through the dichroic mirror and reflected by the bar code to pass through the dichroic mirror again before they get to the operator so that the operator can easily view the bar code if the scanner is properly located relative to the bar code.

On the other hand, a sensor device is arranged within the scanner at a position appropriate for receiving the rays of light reflected by the dichroic mirror and, therefore, the rays of light that have a relatively short wavelength and hence enter the scanner from outside would not get to the sensor device. Consequently, the scanner can read the bar code without being adversely affected by external light.

However, the above described conventional scanner functions properly only when the dichroic mirror operates to show an ideal transmissivity curve (a) as illustrated in FIG. 5.

On the other hand, the line (b) illustrated in FIG. 5 represents a normally observably transmissivity curve of a scanner. Therefore, rays of light having a wavelength within the range A are allowed to pass through the dichroic mirror and reflected by the plane of the bar code, say by 50%, before they reenter the dichroic mirror and are received by the sensor device.

Thus, the known scanner is influenced by external light to consequently degrade the contrast of the image to be picked up by the sensor device to a significant extent.

Japanese patent Laid-Open publication No.5-120462 discloses a scanner using a half mirror in place of a dichroic mirror, although it is obvious that such a scanner is also adversely affected by external light.

While such a degradation in contrast due to the presence of a viewing window may not be significant if a scanner of the type under consideration is used for reading bar codes in a retail shop, it provides a problem of impermissible inaccuracy if the scanner is used for the purpose of verifying bar codes. On the other hand, a viewing window is indispensable for a scanner in order for the latter to be accurately placed relative to a bar code. Therefore, one object of the present invention is to provide a scanner having a viewing window that is free from the above problem.

According to the invention, the above object is achieved by providing a scanner of a bar code verifier comprising a viewing window for aligning the scanner and the bar code characterized in that the viewing window is provided with a blind shutter for opening and closing the viewing window.

FIG. 1 is a schematic perspective view of an embodiment of scanner of a bar code verifier according to the present invention.

FIG. 2 is a cross sectional view of the embodiment of FIG. 1 taken along line 2--2.

FIG. 3 is a cross sectional view of another embodiment of scanner of a bar code verifier according to the present invention.

FIG. 4 is a cross sectional view of a still another embodiment of scanner of a bar code verifier according to the present invention.

FIG. 5 is a graph illustrating an ideal transmissivity curve of a dichroic mirror.

Now, the present invention will be described in greater detail by referring to the accompanying drawings that illustrate preferred embodiments of the invention. FIGS. 1 and 2 show a first embodiment of scanner of a bar code verifier (hereinafter simply referred as scanner) according to the invention. Like a prior art scanner, the scanner 1 of FIGS. 1 and 2 comprises a case 2 provided with a viewing window 7, light sources 3, 3, which is typically an LED for illuminating a bar code 20 and contained in the case 2, a sensor device 4 which is typically a CCD and a lens 5 for forming an image of the bar code 20 on the sensor device 4.

Also like a prior art scanner, a reflection plane 6 is produced by a half mirror or a dichroic mirror somewhere on the light path between the bar code 20 and the sensor device 4 so that the operator can view the bar code 20 through the reflection plane 6 and the viewing window 7 to ensure the positional relationship between the scanner 1 and the bar code 20. Note that,in this embodiment, the viewing window 7 has a window pane 7a and the operator sees the back of the reflection plane 6 through the window pane 7a.

With the above described arrangement, rays of external light enter the scanner through the viewing window 7 and are irregularly reflected before they impinge upon the sensor device 4 to degrade the contrast of the image to be detected by the sensor. However, this problem is avoided by a blind shutter 8 specifically arranged for closing and opening the viewing window 7.

The blind shutter 8 is flexible and typically made of an opaque resin film or a thin metal plate so that it may be moved along the curved inner surface of the case 2 to open or close the viewing window 7 and, therefore, the scanner 1 need not be significantly enlarged in order to accommodate the blind shutter 8.

For verifying a bar code 20 with the scanner 1, the operator moves the blind shutter 8 to its open position to expose the viewing window 7 and places the scanner 1 vis-a-vis the bar code 20. If the reflection plane 6 is that of a half mirror, the bar code 20, the latter can be seen through the viewing window 7 and, therefore, aligned easily with the scanner 1 as it is illuminated by the light source 3. Then, the operator moves the blind shutter 8 to its closed position to cover the viewing window 7 and causes the scanner to read and verify the bar code 20 so that there may be no degradation of contrast by external light of the detected image of the bar code 20.

If, on the other hand, the reflection plane 6 is that of a dichroic mirror which is designed to reflect rays of light coming from the light source 3 with a particular wavelength, the operator cannot see the bar code 20 when the viewing window 7 is open because all the rays of light coming from the light source 3 to irradiate the bar code 20 are reflected by the mirror.

In such a case, the light source 3 may be replaced by one that emits light with a wide range of wavelength such as an incandescent lamp so that the operator can see the bar code 20 with the components of light other than the one having the wavelength reflected by the dichroic mirror and received by the sensor device 4 or the viewing window 7 may be made wide enough to take in a sufficient amount of external light so that the operator can see the bar code 20 with external light. If external light is used for the operator to, see the bar code 20, the operator simply closes the blind shutter 8 after aligning the scanner 1 and the bar code 20 so that the scanner 1 may accurately read and verify the bar code without being affected by irregular reflection of light.

The scanner 1 operates differently when the reflection plane 6 is produced by a half mirror and when it is produced by a dichroic mirror in a manner as described below. When a half mirror is used, the rays of light reflected by the plane of the bar code 20 are transmitted through the half mirror typically by 50% and the remaining 50% of the reflected rays of light are reflected again by the mirror and are directed to the sensor device 4. Thus, the rays of light coming from the light source 3 are utilized by both the sensor device 4 and the operator simultaneously, although the efficiency with which the light is used for verifying the bar code 20 is reduced.

When, on the other hand, a dichroic mirror is used, all the rays of light coming from the light source 3 are reflected by the mirror and move toward the sensor device 4 to remarkably raise the efficiency with which the light is used for verifying the bar code 20, although some light, such as external light, having a wavelength other than that of the rays of light coming from the light source 3 is required to enable the operator to see the bar code 20 through the viewing window. In short, a half mirror and a dichroic mirror provide respective advantages and disadvantages if used in a scanner according to the invention. For the purpose of the invention, therefore, it is necessary to select either one of them depending on the requirements of the specific application of a scanner according to the invention.

FIG. 3 is a cross sectional view of another embodiment of scanner according to the invention. Referring to FIG. 3, the scanner 1A comprises a case 2 provided with light sources 3, 3, a sensor device 4, a lens 5, a reflection plane 6, a viewing window 7 and a blind shutter 8 as in the case of the above described first embodiment. Additionally, the case 2 is provided on the bottom 2a thereof with a contact sensing switch 9 for sensing a state of contact between the scanner 1 and the plane carrying the bar code 20 and a control circuit 10.

With the above arrangement, if the contact sensing switch 9 is turned on to indicate that the scanner 1A is placed directly on the bar code 20, the control circuit 10 immediately turns off the light source 3 for a very short period of time to check and see if the sensor device 4 provides an output. If there is an output of the sensor device 4, it indicates that the viewing window 7 is open, allowing external light to enter the scanner and the control circuit 10a causes a buzzer 10 to sound and notify the operator of the fact that the blind shutter 8 is not completely closed and hence the scanner 1A cannot carry out the operation of reading and verifying the bar code 20.

A limit switch 8b may additionally be provided at the end of the track of the blind shutter 8 on the case 2 that the blind shutter 8 reaches when the viewing window 7 is completely closed in order to cause the buzzer 10a to stop sounding and notify the operator of the fact. Then, the buzzer 10a continues the sounding as long as the operator is trying to align the scanner 1A and the bar code 20 and stops sounding only when the blind shutter 8 is moved to its completely closed position so that a situation where the operator makes the scanner 1A read and verify the bar code 20 without completely closing the viewing window 7 can be prevented positively from taking place.

Thus, with the above described embodiment, the viewing window 7 is completely closed whenever the operation of verifying a bar code is conducted and the operator starts a verifying operation only after the blind shutter 8 is moved to its completely closed position. In other words, a bar code verifying operation is carried out within a period of time that may be varied depending on the skill of the operator and other factors.

FIG. 4 shows a cross sectional view of still another embodiment of scanner according to the invention. Referring to FIG. 4, the scanner lB comprises a case 2 provided with a light source 3, a sensor device 4, a lens 5, a reflection plane 6, a viewing window 7, a blind shutter 8, a limit switch 8b, a contact sensing switch 9 and a control circuit 10 as in the case of the preceding embodiment as well as a blind shutter shifting mechanism 11 for positionally shifting the blind shutter 8 between a closed position and an open position, the control circuit 10 being additionally provided with a timer 10b.

With the scanner lB configured in a manner as described above, as the contact sensing switch 9 is turned on to notify that the scanner lB is placed on a bar code 20, the control circuit 10 starts the internal timer 10b and, when the time set in the timer 10b expires, drives the shifting mechanism 11 to move the blind shutter 8 to its closed position and turns on the limit switch 8b to cause the scanner 1B to automatically start a bar code reading and verifying operation or be put to a ready state for an operation.

When the operation is over and the scanner 1B is moved away from the bar code 20, the control circuit drives the shifting mechanism 11 to move the blind shutter 8 to its open position and brings the scanner into a stand-by state for a subsequent operation. The timer 10b may be set such that a sufficient period of time is allowed to any operator to carry out an operation of aligning the scanner 1B and the bar code 20. Thus, while the time allotted to a single verifying operation is made invariable with this embodiment, the entire verifying operation can be advantageously simplified particularly when a large number of bar codes are involved in the operation.

While a contact sensing switch is used in the above embodiment, a pressure sensing switch or a light sensing switch may alternatively be used. Still alternatively, the contact sensing switch may be replaced by an arrangement with which the blind shutter is closed and opened or a blind-shutter-open-state is notified by a scanning operation initiating switch or a scanning operation start command (typically issued by a microcomputer connected to the scanner in order to analyze the output wave form of the scanner and control the operation of the scanner).

As described above in detail, the viewing window of a scanner of a bar code verifier according to the invention is provided with a blind shutter that can be closed to shut off external light trying to enter the scanner in order to prevent possible degradation in the accuracy of operation of verifying a bar code that may occur to known scanners of the type under consideration. Thus, a scanner of a bar code verifier that operates highly accurately can be provided by the present invention.

Additionally, a scanner according to the invention may be provided at the bottom thereof with a contact sensing switch, which, upon sensing a contact state between the bottom and a bar code carrying plane placed thereunder, temporarily turns off the light source to check and see if the viewing window is completely closed so that, if the viewing window is not completely closed, the operator is notified of the fact. With such an additional arrangement, any undesirable circumstances involving an inadvertently unclosed blind shutter can be effectively avoided to further improve the efficiency and accuracy of the operation of the bar code verifier.

Finally, a scanner according to the invention may be further provided with an additional arrangement that operates to drive the blind shutter to move and close the viewing window after a predetermined period of time if a contact state is detected between the bottom of the scanner and a bar code carrying plane and immediately drives the blind shutter to move to an open position, if a no contact state is detected between the bottom of the scanner and a bar code carrying plane. With such an arrangement, the entire bar code verifying operation can be advantageously simplified particularly when a large number of bar codes are involved in the operation.