Method of detecting a film

Abstract: A method of detecting a film with an optical detecting means in a photographic printer machine. The presence of a film is detected by the optical detecting means installed at a film detecting location where light receiver means (2a to 2n) receives an intensity of light from light emitter means (1a to 1n). The method comprises the steps of determining a setting of the film detecting means so that outputs of the light receiver means (2a to 2n) are higher than a reference level prepared in a control means (10) for judgement of the presence of the film and assigning the setting to the film detecting means so that the outputs of the light receiver means (2a to 2n) have a sufficient margin as compared with the reference level. The initial setting for detecting the presence of a photographic film is carried out with no use of any reference film.

Description: BACKGROUND OF THE INVENTION The present invention relates to a method of detecting a film with an optical detecting means in a photographic processing machine. A photographic processing machine, e.g. a photographic printer, is provided with an optical film detecting means which upon detecting the loading of a film produces and delivers a detection signal to other automatic devices for actuation. The film detecting means is preset to an appropriate detection condition level by initial setting of reference data with the use of a developed film. The initial setting has a value between two extreme levels which represent the presence and absence of the film. In common, the initial setting is carried out at factory before shipment and/or at site by a service person during maintenance service. Such a conventional film detecting method is thus essential to conduct the initial setting using a reference film. If the film detecting means comprises a plurality of components, the initial setting will be troublesome because the components have to be adjusted one by one. Also, the reference film with average density should be employed. If a high density film is used for the initial setting, the detection of a low density film is hardly feasible. The photographic printer machine may thus produce frequent fault actions or critical troubles. The initial setting is also tended to deteriorate with time and becomes incorrect, for example, while the film detecting means being fouled. WO-A-90/08974 discloses apparatus for detecting the presence of processed photographic film in a predetermined location comprising a light source emitting light at a wavelength strongly absorbed by the film and a light receiving means positioned to receive the emitted light when film is not present at said location. WO-A-90/15362 discloses web detection system for determining the measurements of a web. The system comprises a plurality of LED's which are illuminated sequentially and successively so as to scan the web so that the area of the web can be determined for replenishing the chemicals of the film processing equipment. For each LED an initial D/A output signal (D-out) is recorded. Uniform intensity is ensured by measurement of the peak signal for each LED. After storage of the initial D-OUT values, the system is run and as each LED is lit the peak signal is read and classified as blocked, or not. Periodically a re-calibration program is run classifying the measured peak value. If film is present then the signal is compared with the first signal for that LED when there was film present and adjusted accordingly. If there is no film present, LED values for each LED during a scan are classified as to whether they fall within the blocked region or the upper of lower guard regions. It is an object of the present invention, for eliminating the foregoing disadvantages of the conventional film detecting method, to provide an improved film detecting method in which the initial setting is carried out without the use of a reference film so that no troublesome adjustment on each component is needed and fault actions of a film detecting means are avoided. Accordingly the present invention provides a method as set out in claim 1 of the appended claims. A result of which is that an initial setting for detecting the presence of a photographic film is carried out with no use of any reference film. The margin is determined depending on sensitivity characteristics of the film detecting means. With respect to the foregoing method, the light receiver means may be provided with an output circuit which contains a reference level modifying means. In action, the reference level is increased by the margin to have a modified reference level. The illumination of the light emitter means is then increased until the reference level of the reference level modifying means turns to the modified reference level. After the light emitter means are preset with the modified reference level, the reference level modifying means is shifted back to the original reference level. As the result, the light emitter means have a margin of illumination corresponding to the sufficient margin over the reference level. In another modification of the method, the control means is programmed to increase the illumination of the light emitter means so that the margin covers an instantaneous excessive intensity of light over the reference level. Also, the control means may be programmed to increase the gain of the light receiver means so that the margin covers an instantaneous excessive gain over the reference level. It may be adapted to read each output of the light receiver means in relation to a corresponding intensity of light of the light emitter means and reduce the output to a given level which is then stored and used as the reference level. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic overall block diagram of a control circuit showing a first embodiment of the present invention; Fig. 2 is a flow chart explaining a method of detecting a film implemented with the control circuit; Fig. 3 is an explanatory view showing conditions of the first to fourth embodiments of the present invention; Fig. 4 is a schematic overall block diagram of a control circuit showing the second embodiment of the present invention; Fig. 5 is a flow chart explaining a method of detecting a film implemented with the control circuit of the second embodiment; Fig. 6 is a schematic overall block diagram of a control circuit showing the third embodiment of the present invention; Fig. 7 is a flow chart explaining a method of detecting a film implemented with the control circuit of the third embodiment; Fig. 8 is a schematic overall block diagram of a control circuit showing the fourth embodiment of the present invention; and Fig. 9 is a flow chart explaining a method of detecting a film implemented with the control circuit of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described referring to the accompanying drawings. Embodiment 1 Fig. 1 is a schematic block diagram of a circuit for controlling an optical film detecting means in a photographic printer machine showing one embodiment of the present invention. An electronic control circuit 10 is connected to a display 11 and a keyboard 12. The display 11 is provided for displaying screen messages indicative of detected information from a film detecting means. The keyboard 12 is manually operable for modifying the detected information on the display. The electronic control circuit 10 has various functions for actuating a film feeder, guides, a scanner, an exposure illumination source, optical filters, and other devices which all are not shown. The electronic control circuit 10 also contains a control program for the film detecting means. In common, the action and setting of the optical film detecting means are controlled by a timer (not shown) which has been preset for start or interval actions of the photographic printer machine using the electronic control circuit 10. It would be understood that the film detecting means can also be controlled by manual entry of commands through the keyboard 12. There are provided an input/output port 13, a bus circuit 14, a RAM (random access memory) 15, a ROM (read only memory) 16, and a CPU (central processing unit) 17. The optical film detecting means comprises multiple pairs of light emitters 1a and light receivers 2a: for example, light emitting diodes and pin-PD photodiodes respectively, which are mounted at appropriate locations in the photographic printer machine. Each pair of the diodes of the film detecting means are denoted by 1n and 2n in Fig. 1. The light emitters 1a to 1n are actuated by an analog control signal which is converted by a D/A converter circuit 3 from a digital output of the electronic control circuit 10 and fed via a constant current circuit 4. The light receivers 2a to 2n deliver their respective detection signals to an input circuit 5 where they are processed before being further transmitted to the electronic control circuit 10. The output of the input circuit 5 is fed en route to a comparator circuit 6 where it is compared in magnitude with a reference voltage supplied from a reference voltage generator circuit 7 to produce comparison signals H and L (high and low) which are then transmitted to the electronic control circuit 10. The reference voltage of the reference voltage generator circuit 7 is produced in response to a corresponding signal from the electronic control circuit 10. The method of film detection with the optical film detecting means according to the present invention is implemented by the foregoing control circuit. In a manual mode, a flow chart shown in Fig 2 is commenced by key entry action with the keyboard 12. An automatic mode action starts when a start-up inspection mode of the photographic printer machine is selected and accessed. The action of the flow chart starts with Step S1 where the film detecting means is initiated so that each light path between the light emitter 1 and the light receiver 2 is not blocked. This initial action may be executed by an unshown transfer mechanism. If a film is in its loaded position, it may be moved back to clear the light path. At Step S2, the electronic control circuit 10 sends a command signal to the reference voltage generator circuit 7 for temporal increase of the reference voltage. The increase may substantially be equal to, but not limited to, 20 % of the reference voltage. It is determined depending on sensitivity characteristics of the film detecting means so that the intensity of transmitted light is decreased to 50 % to 60 % when blocked by a film. This may be common to other embodiments employing 20 % or 80 %. It is then examined at Step S3 whether or not the output of the light receiver 2 is at high level. If not, the intensity of illumination of the light emitter 1 is increased at Step S4 until the output of the light receiver 2 shifts from low to high. The high and low outputs or H and L signals are indicative of above and below a reference voltage level (a datum setting value) respectively which are provisionally determined for the light receiver 1 as shown in Fig. 3(a). The H and L signals represent the absence and presence of a film respectively. Accordingly, when the reference voltage level has been increased at Step S2, it is examined whether the output is higher or lower than an increased reference voltage. When the output of the light receiver 2 is high, an input current to the light emitter 1 is reduced at Step S5 until the output of the light receiver 2 turns to low. Upon the output of the light receiver 2 shifting to low, the input current of the light emitter 1 drops to a level for generating an intensity of illumination which corresponds to the L signal (and is registered). More specifically, the current driver of the light emitter 1 is set with an increased level of the reference voltage rather than an original level. The increase of current for causing the output voltage of the light receiver 2 to turn to high is applied for eliminating the effect of hysteresis property of the film detecting means and detecting a point where the output voltage of the light receiver 2 is shifted from high to low on the decay slope. The reference voltage at the light receiver 2 is then returned to the original level at Step S7. This series of actions give the following verification. The loading of a film is detected by the film detecting means as the film is being placed between the light emitter 1 and the light receiver 2. According to the embodiment, the intensity of illumination of the light emitter 1 when blocked is decreased to at least 50 % to 60 % even if the film carries a lower density. It is now assumed that the output voltage of the light receiver 2 in response to the illumination of the light emitter 1 is set to correspond to the original reference voltage level (a datum setting value) as in the prior art. In general, the light emitter 1 will deteriorate with time and produce a decreased intensity of illumination after a long-run service of the film detecting means, e.g. one or two years, while the light receiver 2 remains unchanged in the reference voltage level. If so, the illumination of the light emitter 1 has to be increased by manual adjustment which is considered a troublesome task. Also, such erratic adjustment as to set the reference voltage to a lower level may result in fault action of the photographic printer machine, i.e. a detection signal indicative of the presence of a film is released. For eliminating such a fault action, the present invention allows the light emitter 1 to illuminate so that the light receiver 2 produces a voltage output which is greater by a given increment margin than the reference voltage. The increment margin is preferably 20 % of the original reference voltage. If the increment margin is 50 % or greater, the output of the light receiver 2 remains overleveled. Accordingly, since the loss of transmitted light across the film is 50 % to 60 %, the film detecting means may correctly generate a detection signal indicative of no presence of the film. If the margin of the reference voltage is as small as less than 10 %, it may easily be affected or offset by the deterioration with time. We have thus determined an eligible margin of 20 % through a succession of experiments. In brief, the current input to the light emitter 1 is increased, while no film is loaded between the light emitter 1 and the light receiver 2 of the film detecting means, from a low level to a high level sufficient for having the voltage output of the light receiver 2 greater than the reference voltage. As the reference voltage is modified, a difference between the presence and absence of the film is maintained at optimum. Therefore, the detection of any film can be executed at a higher accuracy in response to loading and unloading of the film. According to the method of the present invention, even if the reference voltage of the film detecting means is biased due to physical deterioration with time, the film detecting means performs the foregoing routine procedure before starting its main detecting action. In case that the reference voltage is biased to low, the current input to the light emitter 1 is modified so that the voltage output of the light receiver 2 is 20 % higher than the reference voltage. As the result, the difference between the two voltage output levels across the reference voltage remains unchanged while the actual voltage output being changed, ensuring the accuracy of the film detecting action. Embodiment 2 Fig. 4 is a schematic overall block diagram of a control circuit according to a second embodiment of the present invention. As shown, the comparator circuit 6 and the reference voltage generator circuit 7 of the first embodiment are eliminated. Components identical to those of the first embodiment are denoted by like numerals and will be explained in no more details. In this embodiment, the above two components are substituted with a modification of the program in the electronic control circuit 10. As shown in Fig. 5, the output voltage of the light receiver 2 is examined whether or not it is high at Step S12 similar to Step S3. As the reference voltage is not involved, the output voltage is compared with reference values prepared and stored in the electronic control circuit 10 for judging the level. The two steps S13 and S14 thus correspond to Steps S4 and S5 of Fig. 2. While Step S15 is equivalent to S6, the routine of Fig. 5 is distinguished by only the fact that the comparison is based on a prepared set of the reference values in a memory. The current input to the light emitter 1 is increased at Step S16. More specifically, the increase of the current input is calculated by a computer so that it results in a 20 % increase of the voltage output. This action is identical to the initial current setting of the first embodiment on the light emitter 1 relative to the reference voltage. Even if the output voltage of the light receiver 2 is biased with time, it will hardly be critical because the current input to the light emitter 1 is modified to offset the bias. Embodiment 3 Fig. 6 is a schematic overall block diagram of a control circuit showing a third embodiment of the present invention. As shown, the D/A converter circuit 3, constant current circuit 4, input circuit 5, comparator circuit 6, and reference voltage generator circuit 7 are all eliminated. They are substituted with an amplifier circuit 8 which is coupled between the outputs of the light receivers 2 and the electronic control circuit 10. The electronic control circuit 10 of this embodiment is substantially composed of a microcomputer operable with digital signals. The light emitters 1 and the light receivers 2 are however driven by analog signals and thus, there are provided a group of a D/A converter and a signal amplifier in the light emitter side and an A/D converter in the light receiver side. Those components are not directly related to the performance of the film detecting method of the present invention and appear not in the drawing. No appearance of the components are throughout the drawings of the embodiments. In the third embodiment, the film detecting method is conducted by modifying the gain of the amplifier circuit 8 as illustrated in a flow chart of Fig. 7. Similar to the second embodiment, it is examined at Step S22 whether or not the output voltage of the light receiver 2 supplied through the amplifier circuit 8 is at high level or greater than a corresponding reference value stored in the electronic control circuit 10. If not, the gain of the amplifier 8 is increased until the output voltage becomes at the high level (Step S23). Upon the output voltage reaching the high level, the gain is reduced. When the output voltage is at low level, the gain of the amplifier circuit 8 is observed and registered to the electronic control circuit 10 which in turn determines and records a corresponding reference value. An initial value which is higher by an increment margin than the reference value is then assigned to the gain of the amplifier 8. The increment margin is preferably 20 % as well as of the first embodiment. As the gain of the amplifier circuit 8 is increased, the output voltage of the light receiver 2 becomes relatively high while the illumination of the light emitter 1 remains unchanged. This is equivalent to increase of the illumination of the light emitter 1. Accordingly, the action of the film detecting means will be executed at a higher accuracy as initially modified without the use of a film, similar to the first or second embodiment where the margin is given to the light emitters 1. Embodiment 4 Fig. 8 is a schematic block diagram of an overall control circuit showing a fourth embodiment of the present invention. As shown, an A/D converter circuit 9 is coupled to the electronic control circuit 10 which performs a film detecting method of this embodiment. At Step S31 of Fig. 9 similar to Step S1 of the first embodiment, a film loaded across the film detecting means is removed to allow transmission of light. The step S32 follows for reading an output of the A/D converter circuit 9 as a reference level data. The read output is then reduced to a given level and recorded into the RAM 15 at Step S33. The reduced level is preferably 80 % of the original level which is eligible as described in the previous embodiments. According to the film detecting method, the presence or absence of a film is determined as shown Fig. 3(b). When no film is loaded, it is judged that the output of the A/D converter 9 is greater than the reference level thus to be at high level. If a film is loaded and attenuates the transmission of light, the output is lower than the reference level to be at low level. In other words, the output has a margin of 20 % as compared with the reference level.

Claims: A method of detecting a film with an optical detecting means in a photographic printer machine, the method being provided for detecting the presence of a film with the optical detecting means being installed at a film detecting location where light receiver means (2a,... 2n) generate an output voltage depending on the intensity of light received from light emitter means (1a,...1n) which receive an input current, the optical detecting means comparing an output voltage of the light receiver means with a reference voltage value, characterized in that an initial setting for detecting the presence of a photographic film comprises: detecting an illumination of the light emitter means as a voltage at the light receiver means without a film being placed between the light emitter means and the light receiver means; adjusting one of: a) the reference voltage value to replace the preset reference voltage value; b) the input current to the light emitter means; or c) a degree of amplification of the output voltage from the light receiver means, such that the difference between the output voltage of the light receiver means when there is no film present is greater by a margin of 10 to 50% than the reference voltage value. A method of detecting a film with an optical detecting means in a photographic printer machine as defined in claim 1, wherein the margin is 20 %.

Inventors: EHARA TAKUJI, EHARA, TAKUJI, EHARA, TAKUJI, C/O NORITSU KOKI CO. LTD.
Applicants: NORITSU KOKI CO LTD, NORITSU KOKI CO., LTD.
Application year: 1995
Main classification: G03B27
IPC codes: G03D15, G01V8, G03B27