Product inspection device, product inspection method, and computer program

A product inspection method comprising:

• measuring characteristic values indicating predetermined characteristics of products;
• calculating a standard deviation of variation in the measured characteristic values as a deemed standard deviation;
• calculating a standard deviation of measurement value variation indicating variation in measurement results as a measurement value standard deviation;
• determining whether or not each of the products is a non-defective article depending on whether or not the measured characteristic value is in a range smaller than or equal to an upper limit value and greater than or equal to a lower limit value, wherein an inspection standard defines the upper limit value and the lower limit value of the characteristic values for determining defectiveness of the products as a reference;
• and
• calculating a consumer risk as a probability that a product out of a product standard is mistakenly determined as a non-defective article by the measurement value variation and a producer risk as a probability that a product within the product standard is mistakenly determined as a defective article by the measurement value variation, based on an average value of the measured characteristic values, the deemed standard deviation, and the measurement value standard deviation, wherein
• the characteristic values of a set of the products contained in a product lot having a predetermined number of the products as one unit are measured,
• the deemed standard deviation is calculated from the measured characteristic values of the set of the products,
• the consumer risk and the producer risk are calculated based on the average value of the measured characteristic values of the set of the products, the deemed standard deviation, and the measurement value standard deviation, and
• the inspection standard is changed based on at least one of the calculated consumer risk or the calculated producer risk, and whether or not all the products contained in the product lot are non-defective articles is determined with the changed inspection standard as a reference.

A non-transitory computer-readable medium executable in a product inspection device for inspecting products, the non-transitory computer-readable medium causing the product inspection device to:

• measure characteristic values indicating predetermined characteristics of products;
• calculate a standard deviation of variation in the measured characteristic values as a deemed standard deviation;
• calculate a standard deviation of measurement value variation indicating variation in measurement results as a measurement value standard deviation;
• determine whether or not each of the products is a non-defective article depending on whether or not the measured characteristic value is in a range smaller than or equal to an upper limit value and greater than or equal to a lower limit value with an inspection standard defining the upper limit value and the lower limit value of the characteristic values for determining defectiveness of the products as a reference;
• and
• calculate a consumer risk as a probability that a product out of a product standard is mistakenly determined as a non-defective article by the measurement value variation and a producer risk as a probability that a product within the product standard is mistakenly determined as a defective article by the measurement value variation, based on an average value of the measured characteristic values, the deemed standard deviation, and the measurement value standard deviation, wherein
• the characteristic values of a set of the products contained in a product lot having a predetermined number of the products are measured as one unit,
• the deemed standard deviation is calculated from the measured characteristic values of the set of the products,
• the consumer risk and the producer risk is calculated based on the average value of the measured characteristic values of the set of the products, the deemed standard deviation, and the measurement value standard deviation, and
• the inspection standard is changed based on at least one of the calculated consumer risk or the calculated producer risk, and determining whether or not all the products contained in the product lot are non-defective articles with the changed inspection standard as a reference.